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Report of the Committee on
Boiler Combustion System Hazards
James IL Lafontaine, Chair Pennsylvania Electric, PA
Courtney D. Alvey, Lutherville, MD William H. Axtman, Gray Gull Assoc. Inc., VA Jl~hnny William (Bill) Bass, Forney Int'l Inc., TX
erbert L. Berman, Caltex Services Corp., TX Rep. American Petroleum Inst.
James R. Bostick, Bailey Controls Co., OH Thaddeus Bukowski, Underwriters Laboratories Inc., IL Paul L. Cioffi, Babcock & Wilcox, OH William E. Cunningham, Raytheon Engr & Constructors, MA John C. deRuyter, The DuPont Company, DE Dale E. Dressel, Monsanto Co., MO Robert S. Elek, Kemper Nat'l. Insurance Cos., OH Ronald E. Fringeli, M&M Protection Consultants, OH Warren G. Hudson, Union Carbide Chemicals and Plastics Co. Inc., WV Masaaki Kinoshita, Mitsubishi Heavy Industries Ltd, Japan Donald.]. L, Lin, Qilin Inc., "IX FrancisX. Maskoi, Honeywell, Inc., PA Peter B. Matthews, Hartford Steam Boiler Insp & Ins Co., CT Russell N. Mosher, American Boiler Manufacturers Assn., VA { erryJ. Moskal, Combustion Engineering Inc., CT
obert P. Richmond, Baton Rouge, LA ames L. Sherman, Baltimore Gas & Electric Co., MD om Tighe, Int'l. Union of Operating Engr (IUOE), DC
RobertF. Tomczak, Tampa Electric Co., FL Rep. Electric Light Power Group/Edison Electric Inst.
PeterJ. Gore Willse, Industrial Risk Insurers, CT Rep. Industrial Risk Insurers
Henry IL Wong, Foster Wheeler Energy Corp., NJ
Alternates
John Jaresko, Industrial Risk Insurers, IL (Alt. to P.J.G. WUlse)
Dennis P. Jenkins, Kemper Nat'l. Insurance Cos., NC (Alt. to IL S. Elek)
Kenneth N. Lawrence, Honeywell Inc.,PA (Alt. to F. X. Maskol)
W. Scott Matz, Forney Int'l Inc.,TX (Alt. toJ. W. Bass)
Richard F. Murphy, Exxon Research & Engr Co., NJ (Air. to H. L. Berman)
Satoshi Nouaka, Mitsubishi Heavy Industries Ltd, Japan (Alt. to M. Kinoshita)
John P. O'Rourke, Combustion Engineering Inc., CT (Alt. toJ.J. Moskal)
S. Sam Pagadala, M & M Protection Consultants, IL (Air. to 1L E. Fringeli)
J. C. Wanng, Babcock & Wilcox Co., OH (Alt. to P. L. Cioffi)
Nonvoting
Shelton Ehrlich, Electric Power Research Inst., CA Rep. Electric Power Research Inst.
Thomas B. Hamilton, Hamilton Consulting Services, NC Nell H.Johnsou, SFT, Inc., OH Robert M. Lundberg, Los Altos, CA Michael C. Polagye, Factory Mutual Research Corp., MA
Committee Scope: This Committee shall have primary responsibil- ity for documents on the reduction of combustion system hazards in commercial, industrial and utility boilers with a heat input rate of 12,500,000 Btu/hr and above. This includes all fuels or heat inputs except nuclear. Also responsible for documents on reduction of hazards in pulverized fuel systems, and stoker fired boilers with a heat input rate of 400,000 Btu/hr and above.
Technical Committee on
Heat Recovery Steam Generators
Michael C. Polagye, Chair Factory Mutual Research Corp., MA
Samuel H. Allen, Dow Chemical U.SA., LA Kristlna Brandt, Stewart & Stevenson Operations, Inc., CA Joseph R. Buchanan, ITT Engineered Valves - Skotch, PA Inn M. Clark, ABB Combustion Engineering, Inc., Cq" Ralph S. Ciemens, J. Makowski Assoc., MA Colin Cowan, Callidns Technologies Inc., OK Paul A. Giansiracusa, United Engr & Constructors, MA Alfred W. Grasi, John Zink Co./Div. Koch Engineering Co., OK Edward A. Harris, Tampella Power Corp., PA Harold F. Honath, Coen Co. Inc., CA Warren G. Hudson, Union Carbide Chemicals and Plastics Co. Inc., WV Robert P. Kaltenbach, Burns & McDonnell Eng, MO George Y. Keller, Burns & Roe Enterprises, Inc., NJ Toshio Koyanagi, Mitsubishi Heavy Industries America, Inc., CA Steven A. Lefton, Aptech Engineering Services, CA Robert M. Lundberg, Los Altos, CA Francis X. Maskol, Honeywell, Inc., PA Peter B. Matthews, Hartford Steam Boiler Imp & Ins Co., CT Russell N. Mosher, American Boiler Manufacturers Assn., VA
{~ seph A. Nitzken, Henry Vogt Machine Co., KY artin C. Nygard, Nooter/Eriksen Cogeneration Systems Inc., MO
Owen M. Preston, Florida Power & Light Group, Inc., FL GregoryJ. Reitz, Mission Operations & Maintenance Inc., NV
l ohn Van Name, Ebasco Services Inc., NY oseph M. Vavrek, Sargent & Lundy Engr, IL ames M. Witt, Southern Company Services Inc., AL
Alternates
Dale R. Feidmann,John Zink Co., OK (AlL to A. W. Grusi)
Gregory Lee Gould, Burns & McDonnell Engr, MO (Alt. to R. P. Kattenbach)
Kevin C. Hazelbaker, Mission Operations & Maintenance Inc., NV (Alt. To G.J. Reitz)
Barry Smith, Henry Vogt Machine Co., KY (Alt. to.]. A. Nitzken)
StephenB. Statz, Ebasco Service Inc., NY (Alt. toJ. Van Name),
Robert H. Warburtou,J. Makowski Management Co., RI (Alt. to R. S. Clemens)
Technical Committee on
Multiple Burner Boilers
Robert M. Lundberg, Chair Los Altos, CA
Francis X. Maskol, Secretary Honeywell, Inc., PA
Samuel H. Allen, Dow Chemical U.SA, LA Courtney D. Alvey, Lutherville, MD William H. Axtman, Gray Gull Assoc. Inc., VA Eugene S. Bierman, Pleasantville, NY Thomas A. Collette, Commonwealth Edison, IL Dale E. Dressel, Monsanto Co., MO H. C. Gery, Leeds & Northrup, PA David L. Haysley, Petrocon Systems, Inc., TX Bernard Hrul, Allen Bradley Co., OH Robert P. Kaltenbach, Burns & McDonnell Eng, MO ames K. Lafontaine, Pennsylvania Electric, PA aniel J. Lee, Bailey Controls Co., OH
W. Scott Matz, Forney Int'l., Inc., TX Thomas M. MeKee, Bechtel Corp., MD P. McKeana, Stone & Webster., MA Lalit M. Mehta, Coen Co., Inc., CA Edward G. Milone, Consolidated Edison of New York, NY
90
Russell N. Mosher, American Boiler Mfrs. Assn., VA JerryJ. Moskal, Combustion Engineering Inc., CT Richard F. Murphy, Exxon Research & Engr Co., NJ
Rep. American Petroleum InsL Francisco A. Palacios, Riley Stoker Corp., MA Michael C. Polagye, Factory Mutual Research Corp., MA James R. Rutledge,Jacksonville, FL PeterJ. Gore Willso, Industrial Risk Insurers, CT
Rep. Industrial Risk Insurers James M. Witt, Southern Company Services Inc., AL Henry K. Wong, Foster Wheeler Energy Corp., NJ A.J. Zadlraka, Babcock &Wilcox, OH
Alternates
John C. deRuyter, The DuPont Co., DE (AlL to DuPont Rep.)
W. J. Johnson, Dow Chemical Co., TX (Alt. to S. Allen)
Blair E. Kerstetter, Riley Stoker Corp., MA (Alt. to F. A. Palacios)
John P. O'Rourke, Combustion Engineering Inc., CT (Alt. toJ.J. Moskal)
William L. Smith, Burns & McDonnell Engineering Co., MO (Alt. to R. P. Kahenbach)
Nonvoting
Thomas C. Clayton, Black & Veatch, MO
StaffLiaison: Casey C. Grant
These lists represent the membership at the time these Committees were balloted on the text of this edition. Since that time, changes in the membership may have occurred.
The Report of the Committee on Boiler Combustion System Hazards is presented for adoption in 2 parts.
Part I of this Report was prepared by the Technical Committee on Heat Recovery Steam Generators and proposes for adoption a new document NFPA 8506-1995, Standard on Heat Recovery Steam Generators.
Part I of this Report has been submitted to letter ballot of the Technical Committee on Heat Recovery Steam Generators which consists of 27 voting members; of whom 23 affirmatively, 2 negatively (Messrs. Lundberg and Nitzken), and 2 ballots were not returned (Ms. Brandt and Mr. Koyanagi.)
Mr. Lundberg voted negatively stating: "1. Not ready for public comment, if so voted, please delete my
name from 8506. 9. Many hazards discussed are not disclosed to the public, i.e., two
stacks, fin design, tube leaks, gasification reactions, failure modes of dampers.
3. Chapters 1 to 8 include references to dampers, all should be deleted.
4. Chapter 9 is misleading. 5. Many references in Appendix A should be deleted. They refer
to improper fuels not in the body of the standard."
Mr. Nitzken voted ne!
NFPA 8 5 0 6 - A95 ROP
PART I
(Log #CP1) 8506- 1 - (Entire Document): Accept SUBMITTER: RECOMMENDATION: Adopt a new standard designated as NFPA 8506, Standard on Heat Recovery Steam Generator Systems, as shown following this proposal. SUBSTANTIATION: This document establishes minimum standards for the design, installation, operation, and maintenance of heat recovery steam generators (HRSGs) coupled with combustion turbines and the HRSG fuel burning, air supply, and combustion products removal systems.
NFPA 8506 has been prepared in response to a request to develop criteria that contributes to operating safety and to prevent explo- sions, implosions, and uncontrolled fires in HRSG systems and exhaust ductwork. This request was reviewed by the Technical Correlating Committee on Boiler Combustion System Hazards, which then led to the formation of a new Technical Committee assigned responsibility to develop a new standard.
This proposed standard has been developed over a period of three years involving numerous meetings. The balanced Technical Committee has generated NFPA 8506 in accordance with the NFPA Regulations Governing Committee Projects. C O M M I T ~ E ACTION: Accept.
NFPA 8506
Standard O n Heat Recovery Steam Generator Systems
Chapter 1 Introduction 1-1 Scope 1-2 Purpose
Chapter 2 General 2-1 HRSG Fires and Explosions 2-2 HRSG Implosions 2-3 Manufacture, Design, and Engineering 2-4 Basic Operating Objectives
Chapter 3 Definitions 3q Definitions
Chapter 4 Project Coordination 4.1 General 4-2 Project Inception 4-3 Design 4-4 Construction and Installation 4-5 Initial Training 4-6 Commissioning
Chapter 5 Equipment 5-1 General 5-2 Combustion Turbine 5-3 HRSG Fuel Burning System 5.4 HRSG Enclosure 5-5 Selective Catalytic Reduction 5-6 Electrical 5-7 HRSG Endosure, Fire Protection
Chapter 6 Controls, Monitoring, Alarms and Interlocks 6-1 Control Functions 6-2 Monitoring 6-3 Alarms 6-4 Interlocks 6-5 Burner Management System Logic 6-6 Operator Interface
Chapter 7 Fuel Gas or Fuel Oil Systems 7-1 General 7-2 General Operating Requirements 7-3 Cold Start, Preparation 7-4 Combustion Turbine, Purge and Light-Off 7-5 HRSG, Purge and Lighta3ff 745 Normal Operation 7-7 Normal Shutdown 7-7 Normal Hot Restart 7-9 Duct Burner Emergency Shutdown
Chapter 8 Inspection, Maintenance, Training and Safety 8-1 Equipment Inspection and Maintenance 8-2 Training
Chapter 9 Gas Bypass and Damper Systems 9-1 General 9-2 Combustion Turbine and Unfired HRSG with Bypass Stack 9-3 HRSG Burners with Augmented Combustion Air Supply 9-4 Combustion Turbine and Fired HRSG with Bypass Stack 9-5 Combustion Turbine and HRSG with Fresh Air Firing
Capability
Chapter 10 Fully Fired Systems w Reserved
Chapter 11 Referenced Publications
Appendix A Explanatory Material
Appendix B Industry Experience
Appendix C Referenced Publications
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N F P A 8 5 0 6 m A 9 5 R O P
NFPA 8506
Standard on Heat Recovery Steam Generator Systems
1995 Edition
NOTICE: An asterisk (*) following the number or letter desig natin, g a p aragr pa h .indicates explanatory material on that paragrapn in Appendix ~.
Information on referenced publications can be found in Chapter 11 and Appendix C~
Foreword
Technological advances in recent years, and in particular the Pthervasiveness of microprocessor-based hardware, make it important
at only highly qualified individuals be employed in the translation of these guidelines into operating systems. Each type of hardware has its own unique features and operational modes. It is vital that the designer of the safety system be completely familiar with the features, characteristics, and limitations of the specific hardware, as well as possess a thorough understanding of this standard and its intent.
It is not possible for this standard to encompass the specific hardware applications, nor should it be considered a "cookbook" for the design of a safety system.
When applying any type of equipment to a safety system, the designer carefully must consider all of the possible failure modes and the effect that each might have on the integrity of the system and the safety of the unit and personnel. In particular, no single point failure should result in an unsafe or uncontrollable condition or a masked failure of a microprocessor-based system that could result in the operator unwittingly taking action that could lead to an unsafe condition.
This document is to be used for the design, installation, operation, and maintenance of heat recovery steam generators and their burner management and combustion control systems.
Chapter 1 Introduction
1-1 Scope.
1-1.1 This standard applies to steam generators that recover heat from a combustion turbine firing the following fuels either alone or in combination: natural gas, No. 2 fuel oil, kerosene,JP-4jet fuel, diesel fuel. The heat from the combustion turbine can be fully used by the steam generator, shared to supply heat to other users, or bypassed to permit operation without heat recovery in any combina- tion. The steam generator can be unfired or have supplemental firing from natural gas or fuel oil, as defined in this standard.
1-1.2 This standard does not cover simultaneous firing of more than one fuel in the supplemental firing of the steam generator. Simultaneous firing requires other considerations that are not addressed by this document.
1-1.3 This standard is not retroactive. This standard is applicable to new installations and to major alterations or extensions ot existing equipment for the preparation and burning of fuel contracted for six months subsequent to the date of issue of this document.
1-1.4 This standard does not specifically address the firing of fuels other than as specified in 1-1.1. The intent (see 1-2.2) of this standard shall apply to other fuels not covered by 1-1.1. Other fuels can have unique characteristics requiring specialdesign and operation considerations for fuel handling, purging, and burning.
1-1.5 Since the standard is based on the present state of the art, its application to existing installations is not mandatory. Nevertheless, operating companies are encouraged to adopt those features of this standard that are considered applicable and reasonable for existing installations.
1-1.6 This standard does not address multiple combustion turbines exhausting into a single heat recovery steam generator (HRSG). Any system applying this concept will require special design considerations that are not addressed in this standard.
1-1.7 The standard needs to be taken as a whole. Chapters 1 and 2 are introductory and provide general guidelines and focus for the standard. Where any real or perceived conflict exists, the guidelines outlined in subsequent chapters are to be followed.
1-1.8 Chapters 1 through 8 of this standard address fired or unfired HRSGs directly coupledto combustion turbine exhaust without intervening dampers or a bypass stack.
1-1.9 Chapter 9 of this standard addresses HRSG systems with bypass dampers and systems using supplementary sources of combustion air.
1-1.10 Chapter 10 (reserved) of this standard addresses fired HRSGs where the primary source of heat is from burners rather than from the heat content of the combustion turbine exhaust.
1-2 Purpose.
1-2.1 The purpose of this document shall be to contribute to operating safety and to prevent explosions, implosions, and uncontrolled fires in HRSG sections and exhaust ductwork. It shall establish minimum standards for the design, installation, operation, and maintenance of heat recovery steamgenerators and their fuel burning, air supply, and combustion products removal systems. The standard shall require the coordination of operating procedures and components, control systems, interlocks, andstructural design. The standard shall further require the establishing of training programs in equipment operation and maintenance, for both new and existing personnel, to ensure that minimum standards for operation and maintenance are understood and followed.
1-2.2 No standard can be promulgated that will guarantee the elimination of HRSG explosions and implosions. Technology in this area is under constant development, andthis will be reflected in revisions to this standard. The user of this standard must recognize the complexity of firing with regard to the type of equipment used and the characteristics of the fuel. Therefore, the designer is cautioned that the standard is not a design handbook. The standard does not do away with the need for the engineer or for competent engineering judgment. It is intended that a designer capable of applying more complete and rigorous analysis to special or unusual problems shall have latitude in the development of such designs. In such cases, the designer is responsible for demonstrating the validity of the approach.
1-2.3 Emphasis is placed on the importance of component coordination and on knowledge of expected operating conditions, along with adequate strength of the structure, proper operation and maintenance procedures, combustion and draft control equipment, safety interlocks, alarms, trips, and other related controls that are essential to proper operation.
1-2.4 The effect of gas cleanup systems located within or down- stream of the HRSG shall be considered in the design and operation of the system.
Chapter 2 General
2-1 HRSG F'n'es and Explosions.
2-1.1 The basic cause of uncontrolled fires or explosions in an HRSG system is the ignition of an accumulated combustible mixture within the HRSG enclosure.
2-1.2 A dangerous combustible mixture within the HRSG sections and ductwork consists of the accumulation of combustibles mixed with air in proportions that result in uncontrolled combustion when an ignition source is supplied. An explosion might result from ignition of this accumulation if the quantity of combustible mixture and the proportion of air to fuel are such that an explosive force is created within the HRSG enclosure. The magnitude and intensity of the explosion depends on both the relative quantity of combustibles that have accumulated and the proportion of air that is mixed therewith at the moment of ignition. Explosions, including "puffs," are the result of improper procedures used by operating personnel, improper design of equipment or control systems, or equipment or control system malfunction.
2-1.3 Numerous situations can arise in connection with the operation of an HRSG that produce uncontrolled combustion conditions. These situations include:
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N F P A 8506 m A95 R O P
(a) An interruption of the fuel or combustion air supply or ignition energy to the burners, suffident to result in a momentary loss of flame, followed by the delayed reignition of an accumulation of combustibles.
(b) Fuel leakage into the enclosure and the ignition of the accumulation by a spark or other source of ignition.
(c) Repeated unsuccessful attempts to light-off the combustion turbine or supplementary fired burners without appropriate purging, resulting in the accumulation of an explosive mixture.
(d) The accumulation of an explosive mixture of fuel and combustion air as a result of loss of flame or incomplete combustion at one or more burners in the presence of other burners operating normally or during light-off of additional burners.
(e) The accumulation of an explosive mixture of fuel and combustion air as a result of a complete burner flameout and the ignition of the accumulation by a spark or other ignition source, such as attempting to light-off burners without adequate purge.
2-1.4 An examination of reports of steam generator explosions suggests that the occurrence of small explosions, puffs, or near- misses can be far more frequent than usually is recognized. Improved instrumentation, safety interlocks and protective devices, proper operating sequences, and a l:learer understanding of the problem by designers, operators, and maintenance personnel can reduce greatly the risks and actual incidence of HRSG explosions.
2-1.5 In an HRSG with supplementary firing, upset conditions or control malfunction can lead to an air/fuel mixture that might result in a flameout followed by reignition after a combustible mixture has been reestablished. Deadpockets might exist in HRSG sections and ductwork or other parts of the unit, where combustible mixtures can accumulate under upset conditions. These accumula- tions can ignite with explosive force in the presence ofau ignition s o u r c e .
2-1.6 Statistics indicate that human error is a contributing factor in the majority of explosions. It is important to consider whether the error was a result of:
(a) Unfavorable operating characteristics of the equipment or its control;
(b) Lack of functional coordination of the various components of the steam-generating system and its controls; or
(c) Lack of understanding of, or failure to follow, proper operating procedures, safeguards, and equipment operation recommendations.
2-2 HRSG Implosions.
2-2.1 The HRSG enclosure shall be designed to withstand without damage the maximum draft created by the exhaust stack or induced draft fan, if provided, with all combustion air sources isolated.
NOTE: Due to the supply of combustion turbine exhaust and relatively low HRSG enclosure gas side pressure losses, an implosion ofau HRSG enclosure is an unlikely occurrence.
2-2.2 For HRSGs that use an induced draft fan where the potential exists for excessively low HRSG enclosure gas side pressures, the HRSG enclosure shall conform with the requirements of Chapter 5 on Furnace Implosion Protection of NFPA85C, Standard for the Prevention of Furna~ Explosions~Implosions in Multiple Burner Boiler- Furnaces.
2-3 Manufacture, Design, and Engineering.
2-3.1 The purchaser or the purchaser's agent shall, in cooperation with the manufacturer, ensure that the unit is not deficient in apparatus that is required for proper operation, with respect to pressure parts, fueiburning equipment, combustion air and fuel, and safe light-offand maintenance of stable flame.
2-$.2 All fuel systems shall include provisions to prevent foreign substances from interfering with the fuel supply to the HRSG burners.
2-3.3 An evaluation shall be made to determine the optimum integration of manual and automatic safety features considering the advantages and disadvantages of each trip function.
NOTE: The maximum number of automatic trip features does not necessarily provide for maximum overall safety. Some trip actions result in additional operations that increase exposure to hazards.
2-3.4 This standard shall require a minimum degree of automation. However for more complex plants, plants with increased automa- tion, and plants designed for remote operation, the following minimum provisions shall be provided:
(a) Information about significant operating events permitting the operator to make rapid evaluation of the operating situation;
(b) Continuous and usable displays of variables in the normal control location that will allow the operator to avoid unsafe operation;
(c) Additional automated control points to allow a remotely located operator to safely control the unit;
(d) In-service maintenance and checking of system functions without impairing the reliability of the overall control system;
(e) Control areas environmentally designed to optimize efficient working conditions; and
(f) Visual displays and alarms that are easily identifiable and readable.
2-$.5 The HRSG burner piping and equipment shall be designed and constructed to prevent the formation of hazardous concentra- tions of combustible gases under any operating conditions.
2-4 Basic Operating Objectives.
2-4.1 Basic operating objectives shall include the requirements of this section.
2-4.1.1 Standard operating procedures shall be established that will result in well defined and controlled operations. All operating procedures shall be enforced rigidly at all times.
2-4.1.2 Interlocks shall be used to minimize improper operating sequences and to interrupt sequences when conditions are unsafe for continuation.
2-4.1.3 No interlocks shall be bypassed during start-up or operation of the unit unless the bypass is alarmed and is governed by operating procedures.
2-4.1.4 The mass flow of combustion air to the HRSG burner system shall be maintained at or above its purge rate and within the HRSG burner design operating range during all operations of the HRSG burner system.
2-4.2 Written operating procedures and detailed checklists for operator guidance shall be provided for achieving these basic operating objectives. All manual and automatic functions shall be included in these procedures and checklists.
Chapter 3 Definitions
3-1 Definitions. The following definitions apply to this standard.
Air, Combustion. The air used to fuel combustion process. For HRSG burners thisgenerally is combustion turbine exhaust. (See "Air, Primary" and "Air, Vitiated.")
Air, Excess. Air supplied for combustion in excess of theoretical air.
NOTE: This is not "Air-rich" as later defined.
Air, Primary. The air that is contained in the combustion turbine exhaust.
Air, Furnace Purge. See Purge.
Air, Seal. Air supplied to any device at pressure for the specified purpose of minimizing contamination.
Air, Secondary. The air supplied by a forced draft fan to the burners for combustion.
Air, Stolchiometric. See "Air, Theoretical."
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Air, Tertiary. The air supplied to certain types of burners for cooling the burner meta lo r to improve the combustion process.
Air, Theoretical. The chemically correct amount of air required for complete combustion of a given quantity of a specific fuel.
Air/Fuel Redo. A ratio of air to fuel supplied to a combustion process.
Air-Rich. A ratio of air to fuel supplied to a combustion process that provides more than the minimum excess air required for optimum combustion of the fuel.
Air, Vitiated. Air with less than normal oxygen content; for example, combustion turbine exhaust.
Alarm. An audible or visible signal indicating an off-standard or abnormal condition.
Approved. Acceptable to the authority having jurisdiction.
NOTE: The National Fire Protection Association does not approve, inspect, or certify any installations, procedures, equipment, or materials; nor does it approve or evaluate testing laboratories. In determining the acceptability of installations, procedures, equipment, or materials, the authority having jurisdiction may base acceptance on compliance with NFPA or other appropriate standards. In the absence of such standards, said authority may require evidence of proper installation, procedure, or use. The authority having jurisdiction may also refer to the listings or labeling practices of an organization concerned with product evaluations that is in a position to determine compliance with appropriate standards for the current production of listed items.
Atomizer. The device in a burner that emits liquid fuel in a finely divided state.
Atomizer, Mechanical. That device in an oil burner that emits liquid fuel in a finely divided state without using an atomizing medium.
Atomizing Medium. A supplementary fluid, such as steam or air, that assists in breaking down liquid fuel into a finely divided state.
Augmented Air Firing. Supplementary firing with the addition of air at the HRSG burners to support and stabilize combustion.
Authority Having~uriadiction. The organization, office, or individual responstble for approving equipment, an installation, or a procedure.
NOTE: The phrase "authority having jurisdiction" is used in NFPA documents in a broad manner, since jurisdictions and approval agencies vary, as do their responsibilities. Where public safety is primary, the authority having jurisdiction may be a federal, state, local, or other regionaldepartment or individual such as a fire chief; fi re marshal; chief of a fire prevention bureau, labor department, or health department; building official; electrical inspector; or others having statutory authority. For insurance purposes, an insurance inspection department, rating bureau, or other insurance company representative may be the authority having jurisdiction. In many circumstances, the property owner or his or her designated agent assumes the role of the authority having jurisdiction; at government installations, the commanding officer or departmental official may be the authority having jurisdiction.
Auxiliary lrtring. See "Supplementary Firing."
Availability. The percent of time during a fixed period that a generating unit is capable of providing functional operating service.
Burner. A device or group of devices for the introduction of fuel and air at the required velocities, turbulence, and concentration to maintain ignition and combustion of the fuel.
Burner Management System. The control system dedicated to combustion safety, operator assistance in the starting and stopping of fuel burning equipment, and for preventing misoperation and damage: The burner management system includes the following functions stated in this standard: interlock system, fuel trip system, master fuel trip system, master fuel trip relay, flame monitoring and tripping systems, ignition subsystem, and HRSG burner subsystem.
Combustion Control System. The control system that regulates the fuel input (and air, if applicable) to maintain continuous combus- tion and stable flame. This control system might include drum level, desuperheater spray, or draft control, where applicable.
Combustion Turbine. A turbine in which the rotating element is actuated by the pressure of combustion gases on curved vanes.
Commercial Operation. The date that the full plant capacity is formally added to the power grid.
Commissioning. The time period of plant testing and operation between initial operation and commerdai operation.
Damper, Tight Shutoff. A close-fitting damper to inhibit leakage of air or flue gas into any system component.
Directional Blocking. An interlock that, upon detection of significant error in HRSG process variables, acts to inhibit the movement of all appropriate final control elements in a direction that would increase the error.
Drip Leg. A chamber of ample volume, with suitable clean-out and drain connections, over which fuel gas is passed so that liquids and solids are trapped.
Duct Burners. A burner located in a duct ahead of or within an HRSG section.
Explosive Mixture. A flammable or combustible mixture in a confined space.
Fan, Seal Air. The fan used to supply sealing air.
Fan Test Block Capability. The point on the head versus flow characteristics curve at which the fan is selected. This is the calculated operating point associated with maximum continuous rating of the steam generator furnace plus head and flow margins.
Flame. The visible or other physical evidence of the chemical process of rapidly converting fuel and air into products of combus- tion.
Flame Detector. A device that senses the presence or absence of flame and provides a usable signal.
Flame Detector, Self-Checking. A flame detector that automatically, and at regular intervals, tests the entire sensing and signal process- ing system of the flame detector. This is to ensure that the failure of any single component cannot result in a false indication of flame.
Flame Envelope. The confines (not necessarily visible) of an independent process converting fuel and air into products of comtmstion.
Fresh Air Mode. The operation of an HRSG with atmospheric instead of combustion turbine exhaust.
Fuel Cutback. An action of the combustion control system to reduce fuel flow.
Fuel Gas. See "LP-Gas" and "Natural Gas."
FueI, JP4. A hydrocarbon oil having an API gravity index of 45 degrees and a distillation temperature of 470°F (243°C) and as defined in ASTM D396, Standard Specifications for Fuel Oils.
Fuel, Kerosene. A light distillate fuel oil with an API gravity index of 40 degrees and a distillation temperature range of 256-481°F (124- 249°C).
Fuel Oil. Grades 2, 4, 5, and 6 fuel oils as defined in ASTM D396, Standard Sped.fications for Fud Oils.
Fuel Trip. The automatic shutoffof a specific fuel as the result of an interlock or operator action.
Fuel-Rich. A ratio of air to fuel supplied to a burner that provides less than the minimum excess air required for optimum combustion of the fuel.
Gag See "LP-Gas" and "Natural Gas."
Heat Recovery Steam Generator. A heat exchanger that uses a series of heat transfer sections (e.g., superheater, evaporator, and
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N F P A 8506 - - A 9 5 R O P
economizer) positioned in the exhaust gas flow of a combustion turbine to recover heat and supply a rated steam flow at a required temperature and pressure.
High Fuel (;as Pressure Sensor. A pressure-sensing device arranged to sound an alarm and effect a safety shutdown or prevent starting when the gas pressure exceeds the preset value.
High Fuel Oil Temperature Sensor. A temperature-sensin~ device at initiates a signalwhen oil temperature rises above the hmits
required to maintain the viscosity range recommended by the burner manufacturer.
I-IRSG. See "Heat Recovery Steam Generator."
HRSG Control System. The group of control systems that regulates the HRSG process including the combustion control but not the burner management.
HRSG Enclosure. All ductwork from the combustion turbine exhaust, including any bypass duct connection, through the steam generator to the stack.
HRSG Purge. See "Purge."
HRSG System. The unit assembly from the combustion turbine inlet to the flue gas outlet to the atmosphere.
Igniter. A permanently installed device that provides proven ignition energy for light-off of the main burner.
Igniter, Class 1. An igniter applied to ignite the fuel input through the burner and to support ignition under any burner light-off or operating conditions. Its location and capacity are such that it will provide suRicient ignition energy (generally in excess of 10 percent of full load burner input) at its associated burner to raise any credible combination of burner inputs of both fuel and air above the minimum ignition temperature.
Igniter, Class 2. An igniter applied to ignite the fuel input through the burner under prescribed light-off conditions. The range of capadty of such igniters generally is 4 percent to 10 percent of full load burner fuel input.
Igniter, C/ass 3. A small igniter applied particularly to gas and oil burners to ignite the fuel input to the burner under prescribed light- off conditions. The capacity of such igniters generally does not exceed 4 percent of the full load burner fuel input.
Igniter, Class 3 Spec/a/- A special Class 3 high-energy elec~ical igniter capable of directly igniting the main burner fuel.
Initial Operation. The first coordinated operation of the combus- tion turbine and HRSG.
Interlock. A device or group of devices arranged to sense a limit or off-limit condition or improper sequence of events and to shut down the related equipment or to prevent proceeding in an improper sequence in order to avoid a hazardous condition.
JP4. See "FueI,JP4f
Kerosene. See "Fuel, Kerosene."
Listed. Equipment or materials included in a list published by an organization acceptable to the authority having jurisdiction and concerned with product evaluation that maintains periodic inspection of production of listed equipment or materials and whose listing states either that the equipment or material meets appropri- ate standards or has been tested and found suitable for use in a specified manner.
NOTE: The means for identifying listed equipment may vary for each organization concerned with product evaluation, some of which do not recognize . . . . . . . . equipment as listed unless it is also labeled. The authority hawngjurlsdictaon should utihze the system employed by the listing organization to identify a listed product.
Logic System. The decision-making and translation elements of the burner management system. A logic system provides outputs in a [particular sequence in response to external inputs and internal lOglC.
(a) Hardwired Systems. Individual devices and interconnecting wiring.
(b) Microprocessor-based systems.
1. Computer hardware, power supplies, input/output devices, and interconnections between these.
2. Operating system and logic software.
Low Fuel Gas Pressure Sensor. A pressure-sensing device arranged to sound an alarm and effect a safety shutdown or prevent starting when the gas pressure is below the preset value.
Low Fuel Oil Pressure Sensor. A pressure-sensing device arranged to sound an alarm and effect a safety shutdown or prevent starting when the oil pressure is below the preset value.
Low Fuel Oil Temperature Sensor. A temperature-sensing device arranged to effect a safety shutdown or prevent starting when the oil temperature falls below the limits required to maintain the viscosity range recommended by the burner manufacturer.
Low Water Cutout. A device arranged to effect a master fuel trip when water level in the steam drum(s) falls to a predetermined low level.
LPdga~ A liquefied gas composed of any of the following hydrocar- bons or mixtures of them: propane, propylene, normal butane, isobutane, and butylenes.
Master Fuel Trip. An event resulting in the rapid shutoff of all fuel to the HRSG burners, including igniters.
Master Fuel Trip Relay. An electromechanical relay(s) utilized to trip all required equipment simultaneously.
Monitor. A monitor that senses and indicates a condition without initiating automatic corrective action.
Natural Gas. A gaseous fuel consisting mostly of a mixture of organic compounds (normally methane, ethane, propane, and butane). The Btu value of natural gases varies between 700 and 1500 Btu per ft 3 (26.1 and 55.9 MJ/m3), the majority averaging 1000 Btu per ft 3 (37.3 MJ/m3).
Oil. See "Fuel Oil."
Open Flow Path. A continuous path for movement of an air s(ream through the exhaust to the stack.
Operating Range-Burner. The region between the maximum fuel input and minimum fuel input in which continuous and stable burner flame can be maintained.
Outlet Draft. The flue gas pressure at the outlet of the last convection pass of the steam generator.
Partial Loss of Flame. Loss of flame at any of the separate flame envelopes or burners while flame is maintained at any of the other flame envelopes or burners.
Prove. To establish by measurement or test the existence of a specified condition, such as flame, level, flow, pressure, or position.
Purge, Combustion Turbine. A flow of air at purge rate through the combustion turbine and the appropriate portion of the HRSG enclosure for a sufficient number of volume changes that will effectively remove any gaseous or suspended combustibles and replace them with the purging medium.
Purge, Duct Burner. A flow of combustion turbine exhaust gas or air at purge rate through the HRSG enclosure for a sufficient number of volume changes that will remove effectively any gaseous or suspended combustibles and replace them with the purging medium.
Purge Rate. A constant flow of purging medium at suffident velocity to achieve a purge.
Reliability. The probability that a generating unit or system will perform for at least a given period of time when used under stated conditions.
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Remote Operation. Control from a location removed from the combustion turbine and HRSG.
Repeatability. The ability of a device to maintain a constant set point characteristic.
Runback, Combustion Turbine. The controlled unloading of a combustion turbine to a level required by HRSG control demands.
Scavenging. The procedure by which liquid fuel left in a burner or igniter after a shutdown is cleared by admitting steam or air through the burner passages, typically through a dedicated scavenging medium valve.
SCR. Selective Catalytic Reduction - - a method of reducing NO x in flue gas.
Separator, F'dter, Scrubber. A device incorporated in the main fuel supply line that effectively separates foreign liquids or solids from the fuel.
Set Point. A predetermined value to which a device or system is adjusted and at which it shall perform its intended function.
Shall. Indicates a mandatory requirement.
Should. Indicates a recommendation or that which is advised but not required.
Shutdown, Controlled. The normal unloading and shutdown sequence of plant components based on manufacturer's criteria.
Shutdown, Emergency. An event resulting in the rapid shutoffofall fuel to the combustion turbine along with a master fuel trip.
Stable Flame. A flame envelope that retains its continuity through- out the maximum rate of change within the operating range of the HRSG.
Standard. A document that contains only mandatory provisions using the word %hall" to indicate requirements. Explanatory material may be included only in the form of fine-print notes, in footnotes, or in an appendix.
Start-Up Combustion Control System. A control system used to regulate and maintain proper air/fuel ratio during the start-up period when the customary indexes, such as pressure, temperature, load, or flow, that motivate the normal automatic combustion control system are not available or suitable.
Steam Generator. A closed vessel in which water is converted to steam, steam is superheated, or any combination thereof.
Steam Generator Enclosure. The physical boundary for all steam generator pressure parts and the combustion process.
Supervise. To sense a condition requiring attention and automati- cally initiate corrective action.
Supplementary Firing. The provision of duct burners in an HRSG to increase the temperature of the combustion turbine exhaust gases.
Unit. The confined spaces of the combustion turbine, HRSG, and the associated ducts that convey the air and combustion gases from the air intake to the stack outlet.
Valve, Charging. A small valve bypassing the main safety shutoff valve used for charging the fuel headers and piping and for testing for leaks.
Valve, Check. A valve used to prevent reverse flow.
Valve, Flow Control. Avalve capable of regnlating quantity of throughput to a controlled range.
Valve, Safety Shutoff (Fuel Trip Valve). A fast-closing valve that automatically and completely shuts off the fuel supply to main burners or igniters in response to a fuel trip.
Valve, Supervisory Shutoff. A manually ol~erated shutoff valve with a means to provide a "valve closed position signal.
Valve, Vent. A valve used to permit venting of air or gas from the system to the atmosphere.
Watch-Dog Timer, External. A timer external to a microprocessor- based control that is used to compare the microprocessor cycle timing against itself and that will fail safely if microprocessor timing stops or exceeds the watch-dog time interval.
Chapter 4 Project Coordination
4-1 General.
4-1.1 Project coordination shall be the responsibility of the owner or the owner's designated representative from system inception through commercial operation to enhance equipment reliability and personnel safety.
NOTE: An HRSG is a complex system, often involving numerous components, multiple steam pressure levels, emission control systems, and auxiliary, augmented air or supplementary firing.
4-1.1.1 The ability of the combustion turbine to satisfy the purge requirements in Section 7-4 shall be considered in the basic design phase.
NOTE: As the range of inlet guide vane control is extended for combustion turbines, particularly aero-derivatives, the start-up air flows can be very low (approximately 5percen t of full load mass flow). The combustion turbine purge flow might reqfiire additional considerations to satisfy purge requirements prior to firing the combustion turbine.
4-1.1.2 An HRSG system shall be designed to meet the user's specified modes of operation.
4-1.1.$ System components and control loops shall be compatible and capable of stable operation and control during both steady state and transient conditions.
4-1.1.4 Control and protective systems and operating sequences shall prohibit the operators from bypassing interlocks except as allowed by 2-4.1.$.
4-1.1.5 Training shall ensure operator understanding of the relationships between components; the proper start-up, operation, and shutdown procedures; and the significance of alarms and proper action in response to those alarms.
4-1.2 Explosions and fires have occurred in fuel-fired steam- systems as a result of incomplete functional designs.
estigations have revealed human error but often overlooked the chain of events contributing to the operating error. Therefore, the design, installation, and functional objectives of the overall system components and their controls shall be integrated. Ergonomics and an environment conducive to efficient operator actions and decisions shall be provided.
4-1.3 The planning and engineering phases of plant design and construction shall be coordinated with operating personnel. When this is notpossible, the needs of operating personnel shall be consideredand anticipated.
4-1.4 The proper integration of the various system components, operator functions, maintenance activities, and training shall be the responsibility of the operating company.
4-1.5 Periodic analysis to compare the existing plant to current technology shall be performedso that modifications can be made to enhance plant safety and reliability. (See 1-1.5.)
4-1.6 Documentation of plant equipment, system, and maintenance activities shall be updatedas necessary to accurately reflect current status of equipment and operating procedures.
4-2 Project Inception. In the project inception phase, the following shall be accomplished to ensure a plant design that meets expected operating modes and reliability needs:
(a) Establish plant operating parameters;
(b) Identify site-related constraints;
(c) Review steam cycle, including generating a family of heat balance diagrams for the expected operating ranges and modes;
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(d) Conceptualize plant layout to provide for personnel safety, operability, and maintenance needs;
(e) Define and verify requirements of worst case operating transients, including start-ups;
(f) Define required test program;
(g) Define start-up criteria and goals; and
(h) Identify the authority having jurisdiction. If multiple authorities having jurisdiction are identified, the scope of each authority having jurisdiction shall be defined.
4-$ Design.
4-$.1" The project approach shall include full evaluation of all systems and components to ensure compatibility, interface require- ments, system dynamics, and the ability to meet all plant operating parameters.
NOTE: Safety in any plant is the direct result of an extensive up- front effort in the engineering, design, and selection of equipment for each individual application.
4-$.2* This evaluation shall consider use of dynamic simulation or prior operating experience, or both, before equipment is selected.
4-3.$ Electrical area classifications shall be established. (&e5-6.4.)
4-4 Construction and Installation. The constructor and owner/ operator responsible for the erection and installation of the equipment shall verify that all equipment is properly installed and connected. "
4-5 Initial Training. The training program shall be specific to the equipment being installed and all applicable design data shall be made available.
4-5.10peratorTraining. ( See also 8-2.1.)
4-5.1.1 Prior to commissioning, a formal training program shall be established to prepare personnel to safely and effectively operate equipment.
4-5.1.2 Operator training shall include:
(a) Start-up procedures;
(b) Normal operating procedm'es;
(c) Normal shutdown procedures;
(d) Emergency shutdown procedures; and
(e) Control and safety system check-out and test procedures.
4-5.1.$ Where different modes of operation arepossible, the procedures identified in 4-5.1.2 shall be prepared for each operating mode. Procedures also shall be prepared for switching from one mode to another.
4-5.2 Maintenance Training. (See also 8-2.2.)
4-5.2.1 A formal maintenance training program shall be established to prepare personnel to safely and effectively perform any required maintenance tasks. This program shall be permitted to consist of review of maintenance manuals, videotapes, programmed instruc- tion, testing, field training, and equipment manufacturer training, among others.
4-5.2.2 Maintenance procedures shall be established to cover routine and special technicjues. Any potential safety factors, such as temperature, dust, contaminated or oxygen-deficient atmosphere, internal pressures, and limited access or confined space conditions, shall be included.
4-5.2.$ Procedures shall be consistent with safety requirements and manufacturer's recommendations.
4-6 Commissioning.
4-6.1 The HRSG system shall not be operated until safeguards have been tested and demonstrated to operate properly as a system. Because it might be necessary, in some instances, to install tempo-
rary interlocks and instrumentation, such temporary system shall be reviewed by the purchaser, the engineering consultant, the equipment manufacturer, and the operating company, and agreement shall be reached on its suitability in advance of stact-up. All temporary modifications shall be documented, and permanent resolution shall be accomplished prior to commercial operation.
4-6.2 The safety interlock system and protective devices shall be jointly tested by the organization with the HRSG system design responsibility, along with those who are to operate and maintain the system and devices during the normal operating life of the plant. After installation, coordinated tests of all systems shall be accom- plished before initial operation.
4-6.3 The HRSG system shall not be released for commercial operation before the installation and check of the required safeguards and instrumentation system has been signed-off by those responsible for design and commercial operation.
Chapter 5 Equipment
5-1 General. Equipment required by this standard for safe operation of the HRSG system shall be approved for its intended service.
NOTE: The use of equipment, when available and listed for the intended service, should be considered. When such equipment does not exist, is not available, or is not selected, the selected equipment should have a demonstrated history of satisfactory and reliable operation for the intended service.
5-2 Combustion Turbine.
NOTE: The intent of this standard is not to dictate the methods or particular details of the combustion turbine manufacturer's product or control system. Instead, particular functional considerations are identified for proper interfacing related to the safety aspects of the combined combustion turbine and the HRSG.
5-2.1 Fuel Supply.
5-2.1.1 For fuel oil, two stop or equivalent valves in series, each with proof of closure, shall be provided in the oil line to the combustion turbine.
CAUTION: Means shall be provided to prevent or relieve excess pressure between these valves.
5-2.1.2 For fuel gas, two stop or equivalent valves in series, each with proof of closure, shall be providedin the gas line to the combustion turbine. An automatic vent valve shall be provided between the two valves.
5-2.2 Purge.
5-2.2.1 The combustion turbine shall have means for purging in accordance with Section 7-4.
Exception: In the event the combustion turbine cannot provide purge in accordance with Section 7-4, other means shall be provided.
5-2.2.2 During the purge sequence, means shall be provided to ensure that fuel does not enter the combustion turbine system downstream of the combustion turbine fuel stop valves.
NOTE: The volume between the combustion turbine stop valves should be minimized.
5-2.$ Interlocks.
5-2.$.1 Interlocks shall be provided toprevent starting the combus- tion turbine unless HRSG safety relatedconditiorm are satisfied. Additional interlocks might be required for unusual intended plant operating scenarios. Typical of permissives that shall be considered are"
(a) Water in drum(s) within defined start-up range;
(b) Feedwater supply system available to respond to demand;
(c) Pressure in steam or water spaces not high;
(d) Exit temperature of duct burner(s) not high;
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(e) Position of stack closure (if provided) correct; and
(0 Pressure in ducting system not high.
5-2.3.2 Signals shall be provided to the combustion turbine control system to initiate a change in combustion turbine operating mode, if HRSG safety-related conditions deviate beyond preset acceptable safety-related limits. Typical HRSG conditions warranting a combustion turbine operational response, and the type of response warranted, shall include:
CAUTION: A combustion turbine trip is very costly in terms of combustion turbine life expectancy and shall only be performed under severe conditions that can result in a safety hazard or significant equipment damage.
(a) Water in drum(s) below minimum allowable level - - reduce load;
NOTE: Some steam drum and generating bank designs might require a combustion turbine trip if water level falls below a defined level.
(b) Gas pressure in combustion turbine exhaust plenum high - - trip combustion turbine; or
(c) Position of stack closure (if provided) not cor rec t - - trip combustion turbine.
5-2.4 Operating Interfaces.
5-2.4.1 HRSG design might limit its allowable rate ofwarmup, starting, and rate-of-increase in steam generation. The necessity for slower-than-capable loading and low load hold/soak periods shall be evaluated for the following parameters:
(a) Tube and drum metal temperatures;
(b) Differential metal temperatures within a particular component (i.e., steam drum);
(c) Rate of change of cridcal temperatures; or
(d) Drum water level.
5-2.4.2 In the event HRSG system conditions deviate beyond alarm levels to the interlock limit, the control system shall alarm the condition and initiate a duct burner trip as well as a combustion turbine runback to reduce thermal energy input to the HRSG to a safe level.
5-2.4.3 The control system or operator shall trip the combustion turbine in an emergency that would lead to a safety hazard or catastrophic failure after the actions of 5-2.4.2 have been accom- plished. (See also 5-2.3.Z)
5-2.4.4 Consideration shall be given to taking pre-emergency action automatically in the event tripping parameters deviate beyond alarm levels in order to minimize thermal stress duty cycles on the combustion turbine. Runback parameters shall be permitted to initiate fTom the HRSG or other plant subsystems.
5-3* HRSG Fuei-Burnlng System.
5-3.1 General.
5-3.1.1 The fuel-burning system shall contain the following subsystems as applicable: fuel supply, main burner, igniter, atomizing media supply (if included), and combustion products removal.
5-8.1.2 The fuel-burning system shallprovide means for proper start-up, operation, and shutdown of the combustion process. This shall include appropriate openings and configurations in the component assemblies to permit suitable observation, measurement, and control of the combustion process.
5-3.1.3 Each igniter/burner element shall have a purged and cooled flame scanner port embodied in the design.
5-8.1.4 A sufficient observation port that is conveniently located and of a size to permit visual inspection of the igniter and main burner flames shall be provided.
5-3.2 Fuel Supply.
5-3.2.1 General.
5-3.2.1.1 The fuel supply equipment shall be sized and arranged to ensure a continuous fuel flow adequate for all operating require- ments of the unit. This includes coordination of main fuel control valve, burner safety shutoffvalves, and associated piping volume to ensure against fuel pressure transients that might result in exceeding burner limits for stable flame as a result of placing burners in or taking them out of service.
5-3.2.1.2 The fuel supply equipment shall be designed to inhibit contamination of the fuel. Convenient access to important fuel system components shall be provided. Drains shall be provided at low points in the piping.
5-3.2.1.3 The fuel supply equipment shall be capable of continuing the proper fuel flow during anticipated HRSG pressure pulsations.
5-3.2.1.4 The fuel supply equipment shall be designed with careful consideration of operating environment and ambient conditions, including severe external conditions such as fire or mechanical damage.
5-3.2.1.5 Requirements of the design to facilitate good housekeep- ing shall be recognized.
5-3.2.1.6 Particular attention shall be given to integrity of flexible hoses or swivel joints.
5-3.2.1.7 Fuel piping materials and system design shall be in accordance with ASME B31.1, Code for Pressure Piping - - Power Piping.
5-$.2.1.8 As much of the fuel supply subsystem as practical shall be located away fi"om the burner fxont. A manual emergency shutoff valve shall be provided that is accessible in the event of fire in the HRSG area~
NOTE: Protection for burner front exposed equipment might justify installation of fire protection as indicated in NFPA 850, Recommended Practice for Fire Protection for Electric Generating Plants.
5-3.2.2 Additional Requirements for Fuel Gas.
5-3.2.2.1 The portion of the fuel-supply system upstream of the fuel control valve shall be arranged to prevent excessive fuel gas pressure in the fuel-burning system, even in the event of failure of the main supply constant fuel pressure regulator(s). Where full relieving capacity is not installed, the piping system shall be designed for the full supply pressure up to and including all individual burner and igniter safety shutoff valves.
NOTE: Usually this can be accomplished by providing full relieving capacity, vented to a safe location.
5-3.2.2.2* Positive means to prevent leakage of fuel gas into an idle HRSG shall be provided. An atmospheric vent shall be installed between redundant shutoff valves in any header for main gas or igniter fuel supply.
5-3.2.2.3 Provisions shall be made in the gas piping to allow testing for leakage and subsequent repair. This shall include providing a permanent and ready means for making easy, accurate, _Peri°di'~ tightness tests of the main safety shutoffvalves and indivadual burner safety shutoff valves.
5-$.2.2.4 The discharge from atmospheric vents shall be located so that there is no possibility of the discharged gas being drawn into the combustion turbine air intake, ventilating system, or windows of adjacent buildings and shall be extended sufficiently above the HRSG and adjacent structures so that gaseous discharge does not present a fire hazard.
5-$.2.2.4.1 Header vent lines shall each be run independently.
5-$.2.2.4.2 The igniter vent subsystem shall be run independently of the burner vent subsystem.
5-$.2.2.4.8 There shall be no cross connection between venting systems of different steam generators.
5-8.2.2.5 All burner safety shutoffvalves shall be located as close as
~ ractical to the burner to minimize the volume of fuel left in the urner lines, downstream of the valves.
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5-3.2.3 Additional Requirements for Fuel Oil.
5-3.2.3.1 Fill and recirculation lines to storage tanks shall discharge below the liquid level to avoid free fall, whicfi might generate static electrical charges as well as increase vaporization. (S~NFPA 77, Recommended Practice on Static Electricity, and API - RP 2003, Recom- mended Practice for Protection Against Ignitions Arising Out of Static, Lightning and Stray Currents.)
5-3.2.3.2 Adequate strainers, filters, traps, sumps, etc., shall be provided to remove harmful contaminants where practical; materials not removed shall be accommodated by special operating and maintenance procedures.
NOTE: Contaminants in fuel oil might include salt, sand, sludge, water, and other abrasive or corrosive constituents. Some fuel oils contain waxy materials thatprecipitate out, clogging filters and other elements of the fuel system.
5-3.2.3.3 Special attention shall be given to routes of piping, valve locations, etc, to minimize exposure to high-temperature or low- temperature sources. Low temperature might increase viscosity, inhibit flow, or precipitate waxy materials. High temperatures might cause carbonization or excessive pressures andleakage due to fluid expansion in "trapped" sections of the system.
5-$.2.$.4 Means shall be provided to prevent or relieve excess pressure from expansion of entrapped oil in the fuel system.
5-3.2.$.5 Relief valve discharge passages, vents, and tell-tales shall be provided with suitable piping to permit safe discharge of oil or vapors. This piping might have to be heat traced.
5-3.2.3.6 All instruments and control piping and other small lines containing oil shall be rugged, capable of withstanding the expected range of external temperatures, suitably protected against damage, and maintained at the proper tern erature. The use of interface fluids or sealing diaphragms shall ~e used when necessary.
5-3.2.3.7 Positive means to prevent leakage ofoil into an idle HRSG shall be provided.
5-3.2.3.8* Provisions shall be made in the oil supply system to allow testing for leakage and subsequent repair.
5-3.2.$.9 Fuel oil shall be delivered to the burners at proper temperature and pressure as recommended by the burner manufac- turer, to ensure that the oil is at the viscosity necessary for proper atomization.
5-3.2.3.10 If heating of oil is necessary, it shall be accomplished without contamination or coking.
5-$.2.$.11 For heated systems, adequate recirculadon provisions shall be incorporated for controlling the viscosity of the oil to the burners for initial light-offand for subsequent operation. These systems shall be designed and operated to prevent excessively hot oil from entering fuel oil 'pumps that could cause them to vapor-bind with subsequent interruption to the fuel oil supply.
5-3.2.3.12 Positive means shall be provided to prevent fuel oil from entering the burner header system through recirculating valves, particularly from the fuel supply system of other equipment.
NOTE: Check valves for this function have not proven depend- able in heavy oil service.
5-3.2.3.13 Atomizing media, when required, shall be supplied free of contaminants that could cause an interruption of service. In addition, adequate insulation and traps shal lbe included for steam atomizing to ensure dry atomizing steam to the burners.
5-3.2.3.14 The atomizing medium shall be provided and maintained at the pressure required for proper operation.
5-3.2.3.15 Provisions shall be made to ensure that fuel cannot enter the atomizing medium line at any time.
5-$.2.$.16 The atomizing subsystem shall be designed for conve- nient cleaning and maintenance.
5-3.2.3.17 All burner safety shutoffvalves shall be located as dose to the burner as practical, to minimize the volume of oil that might be left downstream of the burner valve in the burner lines or that might flow by gravity into the HRSG on an emergency trip or burner shutdown.
5-3.3 Ignition.
5-3.3.1 The ignition subsystem shall be sized and arranged to ignite the main burner fuel input within the limitation of the tgniter classification. Igniters are designated by use as Class 1, Class 2, or Class 3 as defined in Chapter 3. Igniters shall be tested to verify that they meet the requirements of the class specified in the design.
5-3.$.1.1 Class 1 igniters shall be permitted to operate as Class 2 or Class 3 igniters.
5-3.3.1.2 Class 2 Igniters.
5-$.$.1.2.1 Class 2 igniters shall be permitted to operate as Class 3 igniters.
5-$.3.1.2.2 When Class 2 igniters are provided, the burner shall be operated under controlled conditions to limit the potential for abnormal operation, as well as to limit the charge of fuel into the duct in the event that ignition does not occur during light-off.
5-3.3.1.2.3 Class 2 igniters shall n o t b e used to ignite main fuel under uncontrolled or abnormal conditions.
5-3.3.1.2.4 Class 2 igniters shall not be used to extend the turn down range, but shall be permitted to be used to support ignition under low load or adverse operating conditions.
5-$.$.1.3 Class $ Igniters.
5-3.3.1.$.1 When Class $ igniters are provided, the i~rniter shall be turned off when the trial for ignition period has expired.
5-3.3.1.3.2 Class $ igniters shall not be used to support ignition nor to extend the burner turn down range.
5-3.3.1.4 Class 3 igniters shall not be used unless supervision of the individual main burner flame is provided.
Exception.. The Class 3 special igniter shall be permitted to be used without supervision of the individual main bu,wr flanw while scavenging the main burtwr.
5-$.3.2 Permanently installed igniters shall be required, and they shall be individually supervised.
5-3.$.3 The ignition equipment shall be located in an appropriate environment with convenient access for maintenance.
5-3.3.4 All igniter safety shutoffvalves shall be located close to igniters to minimize the volume of fuel that is downstream of the valves.
5-3.3.5 Igniter parts exposed to combustion turbine exhaust gas, radiation, or flame shall be designed and fabricated of materials to withstand the operating conditions.
5-3.3.6 Igniters shall be suitably shielded from the effects of the combustion turbine exhaust gas to ensure a stable flame under all operating conditions.
5-3.3.7 Ignition devices shall be removable for maintenance with the HRSG in service.
CAUTION: Precautions shall be taken for personnel protection in the removal of such parts during operation as they will be hot and hot gases will exit the opening left by the removed part.
5-3.3.8 Ignition transformers shall be housed in an enclosure complying with the relevant NFPA 70, NationalEla:trical Code@, requirements regarding electrical classification and environment, bolted to the duct burner frame and adjacent to the igniter, thereby minimizing the length of high voltage cable.
5-3.$.9 The ignition transformer shall not be energized before the HRSG enclosure purge is completed. The ignition transformer shall be deenergized at the end of the igniter trial for ignition period.
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5-3.4 Main Burner.
5-3.4.1 General.
5-3.4.1.1 Burner Elements. The burner elements shall be designed for operation with the fuel(s) specified. The burner shall be designed to produce a stable flame over the operating range.
5-3.4.1.2 Burner parts exposed to turbine exhaust gas, radiation, or flame shall be designed and fabricated of materials to withstand the operating conditions.
5-$.4.1.$ Provision shall be made for visual observation of the burner flame including the ignition zone.
5-3.4.1.4 The burner equipment shall be located with convenient access to the burner components and hardware.
5-8.4.1.5 The main burner subsystem shall be designed so that the burner fuel inputs are supplied to the HRSG continuously and within their stable flame limits.
NOTE: Variations in burning characteristics of the fuel and the normal variations in fuel-handling and fuel-burning equipment introduce an uncertainty to the lower operating limits of the main fuel subsystem in any given HRSG design. In these circumstances, Class 1 or Class 2 igniters, as demonstrated by test, can be used to maintain stable flame.
5-$.4.1.6 The limits of stable flame for each burner subsystem PwirOducing a separate flame envelope shall he determined by tests
thout the ignition subsystem in service. These tests shall verify that transients generated in the fuel and combustion turbine exhaust gas subsystems or maldlstribution of the combustion turbine exhaust gas do not adversely affect the burners in operation. These tests shall include the expected range of available fuels.
NOTE: Such transients are generated by burner shutoffvalves, dampers, etc., that operate at speeds faster than the speed of response of other components in the system.
t apply to tmrnersysterns that require the igniter to be in service any time the burner is being operated.
5-$.4.1.7 When Class 1 or Class 2 igniters are used, the tests in 5- 3.4.1.6also shall be performed with the ignition subsystem in service to verify that the igniters furnished meet the requirements of the class specified in the design. Any resulting extended turndown range shall be available only when Class l igniters are in service and flame proven.
5-3.4.2 Additional Burner Requirements for Fuel Oil.
5-3.4.2.1 Provisions shall he made for cleaning of the burner nozzle and tip.
5-$.4.2.2 Provisions shall be included for clearing (scavenging) the passages of an oil burner into the HRSG with that burner's igniter in service. If the igniter is not operational, the burner shall be removed for clearing.
5-4* HRSG Enclosure.
5-4.1" The HRSG, ducts, and stack shall be sized and arranged to maintain acceptable combustion turbine exhaust gas hackpressure and to remove the products of combustion at the same rate that they are generated by the fuel-burning process during operation of the unit.
5-4.2 The HRSG and ducts shall be capable of withstanding a transient pressure without permanent deformation due to yield or buckling of any support member.
5-4.$* Proper expansion provision shall be made for the movement of the turbine exhaust duct and the HRSG ducts. Any expansion joints so provided shall at least withstand the design pressure that applies to the highest pressure to which either duct is designed.
5-4.4* Convenient access and drain openings shall be provided.
5-4.5 The HRSG ducts shall be designed so that they will not contribute to flame pulsations.
5-4.6 Components common to more than one steam generator shall not limit the rate of removal of products of combustion.
5.4.7 The HRSG ductingbetween the combustion turbine outlet and the HRSG burners shall be designed to provide proper distribution of combustion turbine exhaust gas for stable burner operation.
5-4.8 All HRSG units that utilize liquid or gaseous fuels that are heavier than air shall have a duct design that meets the criteria of 5- 4.8.1 through 5-4.8.$.
5-4.8.1" All low points shall have sufficient slopes to ensure that no dead pockets exist in the bottom of the ducts at other than a designed low point.
5-4.8.2* Drains shall be installed as appropriate at the low points to facilitate clearing fuel from the HRSG enclosure.
5-4.8.3 Provisions shall be included in the design to prevent liquid fuels fi, om being absorbed into the insulation.
5-5* Selective Catalytic Reduction.
5-5,1 When required for NO x emission control, selective catalytic reduction (SCR) systems shall be integrated into the HRSG design so as to operate in the flue gas temperature range required.
5-5.2 Areas in which either anhydrous or aqueous ammonia is stored or piped shall be ventilated adequately to preclude toxic or flammable concentrations.
5-5.3 Anhydrous or aqueous ammonia vessels shall be designed to contain their contents at expected elevated ambient temperatures. Overpressure relief valves vented to a safe location shall be provided.
CAUTION: Precaution shall be taken when selecting a storage area for ammonia as the pressure in storage vessels can rise significantly when exposed to elevated temperatures.
5-6 Electrical.
5-6.1 Electrical equipment shall be protected against transient voltages according to the manufacturer's specification. As a minimum the system shall function at voltages up to 10 percent above the nominally rated voltage and 10 percent below the nominally rated voltage.
5-6.2 All wiring shall comply with the requirements of NFPA 70, National Electrical Code.
5-6.3 All high voltage equipment shall be marked in accordance with the requirements of NFPA 70, NationalElectrical Code.
5-6.4 Where an area is identified as a hazardous location under NFPA 70, NationalElectrical Code, Article 500, the type of equlpment enclosure and the wiring methods to be used are specified by that code and shall be followed.
NOTE: For guidance in determining area classification, see NFPA 496, Standard for Purge d and Pressurized Enclosures for E/ectr/ca/Equipment; NFPA 497A, Recommended Practice for Classification of Class I Hazardous (Classified) Locations for E~cal Installations in Chemical Process Areas,, NFPA 497B, Recommended Practice for Classification of Class II Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas; NFPA 497M, Manual for Classification of Gases, Vapors, and Dusts for Electrical Equipment in Hazardous (Classified) Locations; NFPA 70, National Electrical Code, Article 500; API RP 500A, Classification of Locations for Electrical Installations in Petroleum Refiner/es;, and OSHA 1910.145.
5-6.5 The electrical supply to the burner management system and important subeircuits shall he protected by circuit breakers or fuses.
5-6.6 Upon initiation of a master fuel trip, failure of an electrical power supply shall not impede the orderly and rapid shutdown process.
5-7 HRSG Enclosure, lrtre Protection.
NOTE: Thepossibility of tube fin metal fires in HRSGs is a demonstratedreality. Fire protection and suppression for the HRSG enclosure should be considered.
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Chapter 6* Controls, Monitoring, Alarms, and Interlocks
6-1 Control Functions.
6-1.1 General.
6-1.1.1 A single component failure shall not cause loss of the control system's critical functions identified in Section 6-4.3.
6-1.1.2 Equipment shall he designed and procedures established to permit on-line maintenance of the control equipment. Proper lockout or tagout procedures shall be followed.
6-1.1.3 Procedures for calibrating and testing of controls and interlocks shall be provided.
6-1.2 Fuel Control.
6-1.2.1 Fuel input shall be conn'olled to maintain stable firing conditions. Remote manual operation shall be permitted.
6-1.2.2 Minimum and maximum limits on the fuel input shall be established to prevent fuel flow beyond the stable iinuts of the fuel- burning system.
6-1.3 Primary Air Flow Control. Combustion turbine exhaust flow that is supplied as combustion air to the HRSG shall not be subject to control. (See Chapter 9.)
NOTE: Air flow control for configurations utilizing secondary or tertiary air is addressed in Chapter 9.
6-1.4 Feedwater/Drum Level Control. The water level in each drum shall be maintained automatically. Remote manual operation of the feedwater control device shall be available.
6-2 Monitoring.
6-2.1 Information about significant operating events shall be displayed to permit the operator to make a rapid evaluation of the operating situation.
6-2.2 Recording or trend displays of critical parameters taken at intervals no greater than 5 seconds shall be available to the operator at the operator location. (See 6-2.3.)
6-2.2.1 When accessed through a GRT display in response to an alarm condition, the trend displays shall be available with not more than two keystrokes.
6-2.2.2 When GRT trend displays are used, the displays shall be for a period of not less than the prior $0 minutes from data stored at intervals not exceeding 1 second.
6-2.$ The following HRSGparameters shall be continuously chart recorded or data-logged and trended in accordance with 6-2.2.1 and 6-2.2.2:
(a) Water level in each steam drum;
(h) Fuel pressure at the duct burner(s);
(c) Steam pressure at each pressure level;
(d) Duct burner exit temperature before the first tube bank;
(e) Atomizing medium pressure (for oil only);
(f) Gas temperature upstream of emissions control catalyst(s); and
(g) HRSG flue gas exit temperature.
6-2.4 Consideration shall be given to monitoring the following additional HRSG parameters:
(a) Fuel flow,
(b) Fuel supply header pressure;
(c) Feedwater pressure at each pressure level;
(d) Feedwater fl0w at each pressure level;
(e) Economizer inlet water temperature;
(f) Economizer outlet water temperature;
(g) Steam temperature at each level;
(h) Steam flow at each pressure level; and
(i) Oxygen in flue gas at HRSG outlet.
6-3 Alarms.
6-3.1 Functional Requirement&
6-3.1.1 The functional requirement of any alarm system is to bring a specific abnormal condition to the attention of the operator.
6-3.1.2 Alarms shall be provided to indicate equipment malfunction, hazardous conditions, misoperation, or abnormalconditions that might lead to impending or immediate hazards.
6-$.1.$ The design shall make it difficult to manually defeat the alarm.
6-$.1.4 When equipment malfunction makes it necessary to defeat an alarm, it shall be done by authorized personnel, and the alarm shall be tagged as inoperative.
6-$.1.5 Alarm systems shall be designed so that, for the alarms required by 6-3.2, the operator receives audible as well as visual signals indicating an abnormal condition. The operator shall be permitted to silence the audible signal.
6-$.2 Required Alarms.
6-$.2.1 General. The alarms indicated in 6-$.2.1.2 through 6-3.2.1.9 shall be required.
6-$.2.1.1 All interlock trips shall be individually alarmed.
6-3.2.1.2 HRSG Steam Pressure (High). This shall be measured near the normal HRSG pressure tap location of each pressure level. It shall warn the operator of a pressure, in excess of normal operation, and an approach to HRSG trip conditions.
6-$.2.1.3 Loss of Interlock Power. This shall be sensed and alarmed and shall include all sources of power required to complete interlock functions. For example, if both a 125-V DC electric circuit and a compressed air circuit are required for an interlock scheme, then loss of either shall be annunciated.
6-$.2.1.4 Loss of Control Power. This shall be sensed and alarmed to include any sources of power for the control systems. For example, if both a 125-V DC electric circuit and a compressed air circuit are required for control, then loss of either shall be armunci- ated.
6-3.2.1.5 BuruerValves Not Closed. The dosed position of individual burner safety shutoff valves shall be monitored, and failure O f any valve to close following a trip shall he alarmed.
6-3.2.1.6 Drum Water Level (Low). The water level in the steam generator drums shall be monitored and alarmed when the level in any drum drops below the normal operating range.
6-3.2.1.7 Loss of Generator.
6-3.2.1.8 Duct Irtring Temperature (High).
6-3.2.1.9 Scanner Cooling Air Pressure (Low).
6-3.2.2 Additional Alarms for Fuel Gas.
6-3.2.2.1 Fuel Gas Supply Pressure (High and Low). The gas pressure supplied to the plant shall he monitored at a point as far upstream of the final constant fuel pressure regulator, main fuel control, and main safety shutoffvalves as practicable. This is to warn the operator of unnsualpressure conditions that might result in damage to equipment or indicate a complete loss of gas supply.
6-3.2.2.2 Fuel Gas Burner Header Pressure (High and Low). The burner header gas pressure shall be monitored as dose to the burners as possible in order to warn the operator of abnormal fuel pressures in advance of duct burner trip conditions.
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6-3.2.2.3 Fuel Gas Meter Pressure (High and Low). The pressure at the fuel gas meter shall be monitored at the upstream tap if the fuel gas flow meter is part of the combustion control system and is not pressure compensated. This shall warn the operator if significant error is present in the flow signal to the control system.
6-$.2.2.4 Ignition Fuel Header Pressure (High and Low). The ignition fuel header pressure for Class 1 and Class 2 igniters shall he monitored as close to the burners as possible in order to warn the operator of high or low pressure in advance of conditions that lead to a trip.
6-3.2.3 Additional Alarms for Fuel Oil.
6-$.2.$.1 Main Oil Supply Pressure (Low). The oil supply pressure shall be monitored at a point as far upstream of the main fuel control and safety shutoffvalves as practicable. This is to warn the operator of unusual pressure conditions that might result in damage to equipment or to indicate a complete loss of supply.
6-$.2.$.2 Fuel Oil Burner Header Pressure (Low). The burner header oil pressure shall be monitored as close to the burners as possible in order to warn the operator of low pressure in advance of conditions that lead to a trip.
6-3.2.3.3 Atomizing Medium Pressure (Low). An alarm shall be provided to warn that the atomizing medium pressure is outside of normal operating range and that poor oil atomization might result.
6-4 Interlocks.
6-4.1 Functional Requirements.
64.1.1 The basic requirements of an interlock system for an HRSG are that it protect personnel from injury and protect the equipment from damage. The interlock system functions to protect against improper HRSG operation by limiting action to a prescribed operating sequence or by initiating trip devices when approaching an unstable or undesirable operating condition.
CAUTION: It is possible to achieve conditions conducive to an explosion without them being detected byany of the mandatory automatic trip devices, even though they are properly adjusted and maintained. Therefore, operating personnel shall he made aware of the limitations of the interlock system.
64.1.2 Periodic testing and maintenance shall be performed to keep the interlock system functioning properly.
64.1.$ Whenever a safety interlock device has been temporarily removed from service for maintenance, testing, or repair, this action shall be noted in the log and annunciated if practical. Other means shall be substituted to supervise this interlock function.
64.1.4 The design of an interlock system shall be based on the following fundamentals:
(a) Supervise starting procedure and operation to ensure proper operating practices and sequences;
(b) Trip the minimum amount of equipment in the proper sequence when the safety of personnel or equipment is jeopardized;
(c) Indicate the initiating cause of the trip and prevent starting any portion of the process until proper conditions are established;
(d) Coordinate the necessary trip devices into an integrated system;
(e) Where automatic equipment is not available to accomplish Me intended function, provide sufficient instrumentation to enable the operator to complete the proper operating sequence;
(f) Retain in the design as much flexibilitywith respect to alternate modes of operation as is consistent with good operating practice;
(g) Provide for proper preventive nmi'ntenance;
(h) Shall not require any deliberate "defeating" of an interlock in order to start or operate equipment;
(i) The mandatory master fuel trip sensing elements and circuits shall be independent of all other control elements and circuits; and
E • f o r t i O n : Individual burner flame detectors also shall be permitted to be initiating duct burner master fuel trip systems.
(j) Misoperatinn of the interlock system due to an interruption or restoration of the interlock energy supply shall he prevented.
6-4.1.5 Interlock functions shall be initiated by one or more of the following:
(a) Switches independent of control functions and signals;
(b) Derived from analog signal, provided two analog signals are available with divergence alarm; or
(c) Derived from three analog signals employing an auctioneering system and divergence alarm, or other appropriate fault diagnostic alarm.
6-4.2 Flame Detection.
6-4.2.1 Each burner element or zone shall be individually super- vised. Upon detection of loss of flame the associated individual burner safety shut offvalves shall automatically close.
6-4.2.1.1 Where two flame detectors are fitted to each firing element the flame scanners shall be arranged to alarm on loss of flame from one scanner and to trip the system on loss of flame from two scanners. With one detector out of service, the remaining detector shall trip the system upon loss of flame detection.
6-4.2.1.2 When Class 1 igniters are provided, the main burner flame shall be proven either by the flame scanner or by the igniter being
~ roven. At least one flame detector shall be provided for each urner to detect the burner flame or igniter flame when a Class 1
igniter is provided.
6-4.2.1.3 Burners with Class 2 igniters shall have at least two flame detectors. One detector shall detect main bumer flame and shall not detect igniter flame. The second detector shall detect igniter flame during prescribed light-off conditions.
6-4.2.1.4 Burners with Class 3 igniters shall have at least one flame detector. The detector shall detect igniter flame. It also shall detect main burner flame after the igniter is removed from service at the end of the main burner trial for ignition.
6-4.2.1.5 Where a self-checking flame scanner is provided to each burner, a burner trip shall occur rfthe scanner exhibits a serf-check fault. Where two self-checking flame scanners are fitted to each burner, the flame scanners shall alarm on loss of flame or self-check failure of one scanner and trip the burner on loss of flame or self- check failure from two scanners. With one detector out of service, the remaining detector shall trip the burner upon loss of flame or self-check failure.
6-4.2.2 When a hazardous condition results from loss of flame in more than one burner element or zone, a master fuel trip shall be initiated.
6-4.9.3 It is recognized that any fuel input that does not ignite and burn will create a hazard. Regardless of the number or pattern of flame loss indications used for tripping, loss of flame indication on a firing element shall initiate an alarm, warning the operator of a potential hazard.
6-4.2.4 Field testing is required to validate basic flame tripping concepts. These tests shall be performed on representative units. The results of these tests might be applied to other units of similar size and arrangements, including firing elements/nozzles of substantially the same capacity using similar fuels. These tests are not intended to replace an acceptance test relating to proof of design, function, and components.
6-4.2.5 Flame detector sighting shall be considered in the initial duct burner design. Fieldtests shall be performed to establish optimum sighting angles of firing elements or igniters and also to check angular range of the flame detector in relation to firing elements or igniters.
6-4.$ Duct Burner Master Fuel Trip. A duct burner master fuel trip shall be initiated by the following conditions:
(a) Low fuel pressure;
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(b) Total combustion turbine exhaust flow drops below the minimum required for safe operation of the duct burner as specified by the burner manufacturer or proven by trial;
(c) Combustion turbine trip;
(d) Loss of all burner flame;
(e) Partial loss of flame sufficient to introduce a hazardous accumulation of unburned fuel;
(f) Last individual burner safety shutoffvalve closed;
(g) High fuel pressure, i fa pressure above the operating limits of the burner(s) can occur;,
(h) Low water level on high pressure section of HRSG;
(i) Loss of energy supply for boiler control, burner management, or interlock system;
(j) Atomizing media supply pressure low; or
(k) Burner management system malfunction detected.
6-5 Burner Management System Logic. This section provides requirements for the use of logic systems in burner management.
6-5.1 General. Asingle failure in the burner management s~tem shall not prevent a required shutdown.
NOTE: Some items are not applicable to specific types of logic systems (e.g., relay).
6-5.2 Failure Effects. The logic system designer shall recognize the failure modes of components when considering the design application of the system. As a minimum the following failures shall be evaluated and addressed:
(a) Interruptions, excursions, dips, recoveries, transients, and partial loss of power;
(b) Memory corruption and losses;
(c) Information transfer corruption and losses i
(d) Inputs and outputs "fall on" or ~fail off";
(e) Signals unreadable or not being read;
(0 Addressing errors;
(g) Processor faults; and
(h) Common mode failures.
6-5.3 Diagnostics. Diagnostics shall be included in the design to monitor processor logic functionability.
6-5.4 Logic failure shall not preclude proper operator intervention.
6-5.5 Logic shall be protected from unauthorized changes. A written procedure shall be provided to control and document authorized upgrades, additions, and deletions.
6-5.6 L%ic shall not be changed when the associated equipment is in operation.
6-5.7 System response time (through-put) shall be sufficiently short to prevent negative effects on the application.
6.5.8 Noise immunity shall be adequate to prevent false operation.
6-5.9 No single component failure within the logic system shall prevent a mandatory duct burner f a d trip.
6-5.10 The operator shall beprovided with a dedicated manual switch (es) that shall independently and directly activate the master fuel trip relay.
6-5.11 No momentary contact or automatic resetting device, control, or switch that can cause chattering or cycling of the safety shutoff valves shall be installed in the wiring between the load side (termi- nal) of the primary or programming control and the main or ignition fuel valves.
6-5.12 Requirements for Independence. The logic system perform- ing the safety functions for burner management shall not be combined with any other logic system. This logic system shall be physically separate and visually identifiable. These burner manage- ment safety functions shall include purge interlocks and timing, mandatory safety shutdowns, wial timing for ignition, and flame monitoring.
6-5.15 Software shall reside either in some form of nonvolatile storage or other memory that retains information on the loss of system power.
6-5.14 Application software and input /output devices that support safety logic shall be physically separate from all other software and input /output devices.
6-5.15 System operation shall be verified for compliance with the standard whenever a controller is replaced, repaired, or updated.
6-5.16 Documentation shall be provided to the owner and operator verifying that all safety devices and logic meet the requirements of the application. Functional testing (simulation) of the system shall be performed before it is put into operation.
6-5.17 Programmable logic controllers, if used, shall be monitored by external watch dog timers. Ira timer trips, then a duct burner trip shall occur.
6-6 Operator Interface.
6-6.1 Alarms and indicators shall be operationally grouped and visible to the operator to allow rapid access to operational devices.
6-6.2 All emergency alarm indicators, push buttons, and selector switches shall be readily visible to the operator and shall be clearly labeled. Theyshail be protected to avoid inadvertent actuation.
6-6.3 All control functions shall be grouped for easy access and in relatively close proximity to their associated alarm and indication devices.
6-6.4* Where CRT displays are used, informational data shall be displayed on monitor screens in a logical, operational grouping to minimize the number of keystroke operations to respond to system upsets. Alarm functions shall be prioritized to appear on the monitor screen upon being sensed regardless of any information already displayed.
6-6.5 Personnel shall be trained to understand and interact with the control systems.
Chapter 7 Fuel Gas or Fuel Oil Systems
7-1 General.
, 7-1.1 This chapter contains requirements when burning fuel gas or fuel oil in duct burners. This includes certain interlocks for preventing improper action, certain safety trips and flame supervi- sions, and an indication of the status of the start-up sequence.
7-1.2 This chapter provides minimum standards for design, installation, and operation of duct burners in the exhaust ductwork of a combustion turbine coupled to an HRSG. No specific degree of automation beyond the minimum specified safeguards is defined or required, as this is the subject of many factors such as, but not limited to, physical size of the unit, use of central control room, degree of reliability required, and availability of experienced operating personnel. All devices as required in the text shall be provided. The requirements of the operating system that shall be used with these limitations are as follows:
(a) A trained operator shall be available at an appropriate location to take required safety-related actions;
(b) The start-up of the burner as a first-tlme function shall be accomplished with an operator at the burner location, with a direct view of the burner. Recycling of the burner in response to steam demand as long as the combustion turbine has not tripped shall be permitted to be an automatic sequence; and
(c) Suitable equipment shall be provided to control HRSG inputs and their rate of relative change wRhln the limits of stable flame through the operating range.
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7-2 General Operating Requirements.
7-2.1 Prior to starting a unit, action shall be taken to prevent fuel from entering the HRSG.
7-2.2 The associated igniter for a burner shall always be used unless the burner is specifically designed to be lit from an adjacent burner. Burners shall no t be lit f rom any hot surface.
7-$.3 When operating at low capacity, burner fuel pressure shall be maintained above min imum by reducing the number of burners in service as necessary.
7-2.4 Gas. Before maintenance is performed on the gas header, the header shall be purged. (SeeA-7-1.1.)
7-2.4 Oil. Before maintenance is per formed on the oil header, it shall be drained and purged as necessary.
7-2.5 Oil - - Scavenging of Oil Burner Passageg
7-2.5.1 Oil burner passages shall no t be scavenged into a nonopera t ing HRSG. Combustion turbine exhaust flow shall be present and maintained during the scavenging process.
7-2.5.2 Igniters shall be in service, with ignition established, when scavenging oil passages into the HRSG.
7-2.6 Sequencing.
7-2.6.1 Sequencing is required to ensure that operating events occur in proper order. Written procedures shall be provided to properly sequence the start-up and shutdown of the entire unit (combustion turbine and HRSG). Sequencing also is utilized when removing burners from operation or adding burners to operation.
7-2.6.2 The starting and shutdown sequence outl ined in this chapter shall be followed.
NOTE: This provides a continuous air or flue gas flow through the HRSG at least at the rate that existed during the purge operation. The objective of this practice is to ensure min imum velocities through the unit to prevent hazardous accumulations of unburned fuel.
7-2.6.3 Burners shall no t be placed in service or removed in a random pattern but in a sequence defined by operating instructions and verified by actual experience with the unit in order to minimize laning or stratification of fuel or combustion products. Burners shall be placed in service as required, with fuel flows that ensure proper light-off.
NOTE: Automatic start systems might establish igniter flame on multiple burner elements simultaneously with proper supervi- sion. Similarly, main burner elements can be conf ignredto operate as one with proper supervision.
7-2.6.4 If the fuel pressure at the burner header is used as a guide in maintaining the required fuel flow per burner, it shall be main- tained automatically within prescribed limits as additional burners are placed in service.
7-2.6.5 Duct burners shall be operated in accordance with the manufacturer 's spedfications and operating procedures.
7-2.6.6 This procedure shall incorporate the following operating objectives:
(a) Complete purge in accordance with Sections 7-4 and 7-5; and
(b) No light-off of the duct burner(s) shall occur until after the combustion turbine has established stable operation with an exhaust gas flow not less than that required for duct burner operation.
7-2.6.7 Each unit shall be tested during initial start-up to determine whether any modifications to the basic procedures are required to obtain satisfactory ignition and system operation. However, the number of equipment manipulations shall be minimized.
7-2.6.8 The unit shall be operated within the specified parameters. Any modifications or deviations shall be made only after the need for such changes has been de termined by operating experience and system review.
7-3 Cold Start, Preparation. Preparation for starting shall include a thorough inspection, particularly for the following=
(a) Units in good repair and free of foreign material;
(b) (oil) Inspect the unit for accumulated fuel oil, and drain and dean as necessary;
(c) Al lpersonnel evacuated f rom the uni t and associated equip- ment andal l access and inspection doors closed;
(d) All safety shutoffvalves proved dosed and all ignition sources deenergized;
(e) (gas) Fuel gas system vents open and venting to a safe outside location. Fuel gas lines drained of condensate;
(e) (oil) Circulating valves open to provide and maintain oil in the burner headers;
(f) Proper drum water levels established in natural and forced circulation HRSGs and flow established in forced circulation HRSGs;
(g) Burner elements and igniters positioned in accordance with manufacturer 's specification;
(h) Energy supplied to control systems and to safety interlocks;
(i) Meters or gauges indicating fuel header pressure to the unit;
(j) Instrumentation tested and functional;
(k) A complete functional check of the safety interlocks performed after an overhaul or other significant maintenance; and
(1) Verification of an open flow path f rom the inlet of the combustion turbine through the HRSG unit to the stack discharge.
7-4 Combustion Turbine Purge and Light-Off.
7-4.1 The purge of the combustion turbine shall be in accordance with the manufacturer 's instructions and the requirements of 7-4.2 and 7-4.3.
7-4.2 Initial Combustion Turbine Purge and Light-Off.
7-4.2.1 Purge prior to the light-off of the combustion turbine shall be accomplished by at least 5 volume changes and for a duration of not less than 5 minutes. This volume shal lbe calculated based on the following:
(a) The combustion turbine operating at full load with no supplementary HRSG firing; a n d
(b) The volume from the combustion turbine inlet to the portion of the HRSG where the combustion turbine exhaust gas temperature is reduced to at least 100°F (38°C) below the lowest autoignition temperature of the fuel(s) for which the system has been designed.
7-4.2.2 The combustion turbine purge shall have a flow rate as near as possible to 25 percent of full load mass air flow but no t less than 15 percent.
7-4.3 Failure to Start. On failure to start, the combustion turbine shall be retried in accordance with 7-4.3.1 through 7-4.3.3.
7-4.3.1 When firing any liquid fuel or any heavier than air gas, verification shall be made that the duct low point is cleared of combustibles. This shall be accomplished by one of the following methods:
(a) For a system firing any liquid fuel, the drains shall be checked to verify that they are clear and that no fuel is present (seeS-4.8); or
(b) For a system firing any gas that is heavier than air, the vents shall be checked to verify that no combustible gas is present (see5- 4.8).
7-4.3.2 The second trial to start the combustion turbine with the same or alternate fuel shall be permit ted following a repurge in accordance with 7-4.2.
7-4.3.3 Subsequent trials to start the combustion turbine with the same or alternate fuel shall be permit ted following a repurge in accordance with 7-4.2, and after it has been proven that combus-
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tibles have been removed. This verification shall be accomplished using a combustibles analyzer.
CALrrION 1: Stratification of gases shall be considered when analyzing for combustibles.
CAUTION 2: Excessive retries shall be avoided. When operating experience indicates there are problems in combus- tion turbine light-off, the light-off attempts shall be terminated and the cause investigated and corrected.
7-4.4 After completing the purge, the air flow through the combus- tion turbine shall be permitted to be dropped below the purge rate if required by the design to accomplish combustion turbine ignition.
7-4.5 After successful light-off of the combustion turbine, the combustion turbine shall be brought to speed and loaded as required to meet system demands.
NOTE: The loading of the combustion turbine might be restricted by HRSG parameters.
7-5 HRSG Purge and Light-Off
7-5.1 The purge of the HRSG enclosure shall be accomplished with a flow utilizing air or combustion turbine exhaust at not less than 25 percent of full load mass flow rate or the minimum flow required for operation of the HRSG burners, whichever is greater.
7-5.$ The HRSG enclosure purge shall accomplish at least 8 volume changes of the HRSG enclosure after combustion turbine exhaust flow in accordance with 7-5.1 has been achieved.
NOTE: Purge prior to light-off of the combustion turbine should not be considered a purge of the HRSG enclosure unless the requirements of %5.1 and 7-5.2 have been satisfied.
7-5.$ An HRSG burner trip or failure to successfully light-off HRSG burners shall require a repurge in accordance with 7-5.1 and 7-5.2 prior to attempting a relight.
7-5.4 Duct Burner.
7-5.4.1 Testing igniters for duct burners shall be conducted in accordance with the following:
(a) A complete periodic operational test of each igniter shall be made. The frequency of testing depends on the design and operation history of each individualHRSG and ignition system. As a minimum, the test shall be made during every start-up following an overhaul or other significant maintenance.
NOTE: The importance of reliable igniters and ignition systems cannot be overstressed.
(b) Individual igniters or groups of igniters also shall be permitted to be tested while the unit is in service. Such tests shall be made with no main fuel present in the igniters' associated burner.
7-5.4.2 Starting Sequence.
7-5.4.2.1" The operating sequences described in 7-5.4.2 assume the use of multiple element duct burners operated independently of each other. For installations with a duct burner (single element or multiple element) operated as a single unit, procedures similar to that outlined in 7-5.4.2 shall be followed with the exception that sequences unique to multiple burner operations shall not apply.
NOTE: For typical fuel supply systems for duct burners that .rate as a single unit, see Figures A-%5.4.2.1 (a), (b), (c), and
7-5.4.2.2* These starting sequences shall be performed in the following order consistent with the manufacturer's instructions:
NOTE: The sequences are based on the typical fuel supply systems shown in Figures A-7-5.4.2.2(a), (b), (c), (d), (e), and (f).
(a) All duct burner main fuel safety shutoffvalves shall be proven to be closed. Also, all duct burner igniter fuel safety shutoff valves shall be proven to be closed.
(b) The main fuel header and the igniter fuel header shall be pressurized up to the individual main burner and igniter safety shutoffvalves in accordance with established operating procedures.
(c) The first individual igniter safety shutoffvalve shall be opened, and the ignition transformer shall be energized. Ifflmne on the first igniter is not established within 10 seconds, the individual igniter safety shutoff valve shall be closed. The cause of failure to ignite shall be determined and corrected. With turbine exhaust flow maintained, repurge is not necessary, but a waiting period of at least 1 minute shall elapse before attempting a retrial of this or any other igniter.
(d) The main fuel control valve shall be set to the burner light-off position.
(e) The first individual main burner safety shutoff valve shall be opened. If the main burner flame is not proven within 5 seconds after main fuel enters the duct, a duct burner master fuel trip shall occur.
(f) After each stable main burner flame is established, the igniter shall be shut off unless classified as Class 1 or Class 9. The stability of the main burner flame shall be verified.
(g) The associated igniter for a burner al-,~rays shall be used to light the burner unless the burner is specifically designed to be lit from an adjacent burner. Burners shall not be lit from any hot surface.
(h) Second or succeeding igniters shall be lit in accordance with (c). I fa second or succeeding burner igniter does not light off within 10 seconds after its individual igniter safety shutoff valve has been opened, the individual igniter safety shutoff valve shall close. The cause for failure to light shall be determined and corrected. A waiting period of at least 1 minute shall elapse before the next light- off is attempted.
(i) Second or succeeding burners shall be lit in accordance with (e). If second or succeeding main burner flame is not established, the individual burner safety shutoff valve and individual igniter safety shutoff valve shall close. The cause for failure to ignite shall be determined and corrected. Awaiting period of at least 1 minute shall elapse before the next light-off is attempted.
(j) After each successive burner light-ofl~ the operator shall verify flame stability of all operating burners.
7-6 Normal Operation.
7-6.1 The HRSG steamingrate shall be regulated by combustion turbine loading and duc tburne r exhaust temperature.
7-6.$ The firing rate shall be regulated by varying the fuel to individual burners by means of a fuel control valve(s) or by staged firing where burners are brought in or taken out of service. Individual burner safety shutoffvalves shall not be used to vary the fuel rate of the b t imer elements. All safety shutoffvalves shall be fully open or completely closed; intermediate settings shall not be used.
7-6.$ The burner fuel shall be maintained within the range between the maximum and minimum limits specified by the burner and HRSG manufacturer, or as determined by trial. These trials shall test for minimum load and for stable flame: (1) with all burners in service and combustion control on automatic, and (2) with different combinations of burners in service and combustion control on automatic. Where changes occur to the minimum and maximum limits because of various burner combinations and fuel conditions, retesting shall be required.
7-6.4 On loss of an individual burner flame, that burner 's indi- vidual safety shutoff valve and the associated igniter safety shutoff valve shall dose.
7-7 Normal Shutdown.
7-7.1 Burners shall be shut down sequentially as load is reduced by closing the individual burner safety shutoffvalves.
7-7.$ The duct burners shall be taken out of service with verification that the safety shutoffwalves are secured in the closed position.
7-7.$ When taking the unit (combustion turbine and duct burner) out of service, the combustion turbine load shall be reduced in accordance with the manufacturer's shutdown procedures.
7-7.4 Steam flow shall be maintained through the superheater as necessary.
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N F P A 8 5 0 6 - - A 9 5 R O P
7-7.5 The normal coast down of the combustion turbine shall be considered to provide a post purge of the unit.
7-7.6 After completion of the post purge in 7-7.5, consideration shall be given to maintaining air flow through the unit to prevent accumulation of combustible gases.
7-7.7 Leakage of fuel into the unit shall be prevented.
7-8 Normal Hot Restart.
7-8.1 When restarting a hot combustion turbine, the requirements for cold start preparation as described in 7-3(d) through 7-3(i) shall be followed.
7-8.2 The starting sequence of Sections 7-4 and 7-5, if required, shall be followed.
7-9 Duct Burner Emergency Shutdown.
7-9.1 A duct burner master fuel trip shall be initiated by the conditions identified in Chapter 6.
7-9.2 Gas. A duct burner master fuel trip shall stop all fuel flow to the HRSG from all burners by tripping the main and individual burner safety shutoffvalves. All vent valves shall be opened. The igniter safety shutoffvalve and individual igniter safety shutoffvalves shall be tripped and igniter sparks deenergized. Master fuel trips shall operate to stop all fuel flow to the burners within a period of time that will not permit a dangerous accumulation of fuel in the HRSG. All igniters or other ignition sources shall be tripped.
7-9.2 Oil. A duct burner master fuel trip shall stop all fuel flow to the HRSG from all burners by tripping the main and individual burner safety shutoffvalves. The igniter safety shutoffvalve and individual igniter safety shutoff valves shall be tripped and igniter sparks deenergized. Master fuel trips shall operate to stop all fuel flow to the burners within a period of time that will not permit a dangerous accumulation of fuel in the HRSG. All igniters or other ignition sources shall be tripped.
7-9.$ The burners shall not be reignited until the initiating trip condition has been investigated and corrected, and a unit purge has been completed.
Chapter 8 Inspection, Maintenance, Training, and Safety
8-1 Equipment Inspection and Maintenance.
8-1.1 The owner or his or her designated agent shall be responsible for ensuring that there is a comprehensive inspection and mainte- nance program for the equipment. The program shall provide for the maintenance of equipment at intervals consistent with the type of equipment, its service requirements, industry practice, and the manufacturers' recommendations.
8-1.2 As a minimum, the maintenance program shall include the following:
(a) In-service inspections to identify conditions requiring corrective action or further study;
(b) Detailed, knowledgeable planning for effecting repairs or modifications using qualified personnel, established procedures, and appropriate equipment;
(c) Use of detailed equipment history that records conditions found, maintenance work done, changes made, and date of each;
(d) Written comprehensive maintenance procedures incorporat- ing manufacturers instructions to define tasks and skills required. Any special techniques, such as nondestructive testing or tasks requir-ing special tools, shall be defined. Special environmental factors shall be covered, such as temperature limitations, dust, contaminated or oxygen-deficient atmosphere, internal pressures, and limited access or confined space requirements;
(e) Shutdown maintenance inspections, thorough in scope, to cover all areas that have been identified during operation as requiring attention, in addition to the routine check-list items; and
(f) Maintenance of adequate spare parts meeting specifications that provide reliable service without necessitating makeshift repairs.
8-1.3 An inspection and maintenance schedule shall be established and followed.
8-1.4 Inspections, adjustments, and repairs shall be performed by trained and qualified personnel, using tools and instruments suitable for the work. Maintenance and repairs shall be accom- plished in accordance with the manufacturers' recommendations and applicable standards, codes, and safety regulations.
8-1.5 Operation set-point and adjustments shall be verified periodically, with the results documented.
8-1.6 Defects shall be reported and corrected, with the repairs fully documented.
8-1.7 Inspection or maintenance personnel shall not make any changes to the system confgurafion, including logic, set-points, and sensing hardware, without the effects on operation and safety being evaluated and the changes authorized in advance. All changes shall be documented.
8-1.8 In pressurized (positive-pressure) installations, inspection or maintenance personnel shall check for and report any combustion- ~d~arnleakage through casings, ductwork, expansion joints, or
pers.
8-1.9 When a unit firing liquid fuel is out of service and available for inspection, personnel shall check for any accumulation of unburned fuel in the HRSG enclosure, especially in the finned-tube area.
8-1.10 During planned maintenance outages, stack dampers shall be inspected for proper operation and position indication.
8-2 Training.
8-2.1 Operator Training.
8-2.1.1 The owner or his or her agent shall be responsible for establishing a formal and ongoing program for training operating personnel. The training program shallbe established to prepare personnel to safely and effectively operate the equipment. This program shall consist of study or review of operating manuals, videotapes, programmed instruction, examinations, computer simulation (if available) and supervised hands-on field training. The training program shall be consistent with the type of equipment and the hazard involved.
8-2.1.2 The owner or his or her agent shall certify that operators are trained and competent to operate the equipment under all possible conditions prior to them operating it.
8-2.1.3 The owner or his or her agent is responsible for periodic retraining of operators, including review of their competency.
8-2.1.4 The training program and manuals shall be reviewed periodically to keep them current with changes in equipment or operating procedures. The training program and manuals covering operation and maintenance procedures shall be readily available for reference and use at all times.
8-2.1.5 Operating procedures that cover both normal and emer- gency conditions shall be established. Start-up and shutdown Phrocedures, normal operating conditions, and lockout procedures
all be covered in detail in operating manuals and the associated training programs.
8-2.1.6 Operating procedures shall be direcdy applicable to the equipment involved and shall be consistent with safety requirements and the manufacturers' recommendations.
8-2.1.7 Operators shall be trained in the proper procedures for reducing load or tripping the system whenever there is a potential for an unsafe condition that can lead to danger to personnel or property damage. The operator shall be authorized to take aPcaP~lliropriate action including reducing load, tripping equipment, or
ng for outside assistance in case of emergency.
8-2.2 Maintenance Training.
8-2.2.1 The owner or his or her agent shall be responsible for establishing a formal and ongoingprogram for training mainte- nance personnel. The program shall prepare personnel to safely and effectively perform any required maintenance tasks. This program shall be permitted to consist of study review of mainte- nance manuals, videotapes, programmed instruction, examinations,
107
NFPA 8506 - - A95 ROP
field training, and training by the equipment manufacturers, among others. The training program shailbe specific to the equipment and potential hazards involved.
8-2.2.2 Maintenance procedures and their associated training programs shall be established to cover routine and special tech- niques. Any possible environmental factors such as temperature, dust, contaminated or oxygen-deficient atmosphere, internal ~ressures, and limited access or confined space requireme~ats shall
e included. - - -
8-2.2.3 Maintenance procedures shall be consistent with safety requirements and manufacturers' recommendations. The proce- dures contained in the training programs shall be reviewed periodically to keep them current with changes in equipment. They shall be used in the indoctrination and training of new maintenance personnel.
8-2.2.4 Maintenance personnel shall be trained to notify operating personnel in writing of any changes made in safety and control devices.
8-2.2.5 Maintenance personnel shall be trained to be knowledgeable of and to adhere to all Occupational Safety and Health Act (OSHA) safety procedures.
8-2.2.6 Procedures shall be reviewed periodically to keep them current with changes in equipment and personnel.
Chapter 9 Gas Bypass and Damper Systems
9-1 General. The requirements in Chapters 1 through 8 shall apply to other combustion turbine and HRSG configurations (see Figures 9- 2 through 9-5) except as amended or supplemented in subsequent sections of this chapter. There are additional safety considerations and requiremems when these configurations are used.
NOTE: Chapters 1 through 8 of this standard have been written based on a directly coupled combustion turbine and HRSG either with or without HRSG burners. Combustion turbine exhaust is the oniysource of heat to the HRSG when no HRSG burners are supplied and is the only source of combustion air for the HRSG burners when the HRSG system is so equipped. [See Figures 9-If a) and (b ). ]
Stack
L. . J
Combustion turbine
letgure 9-1 (a) Combustion turbine with direcdy coupled unrwed HRSG.
HRSG Stack
Combustion turbine Burners
Fgere 9-1(b) Combustion turbine and directly coupled HRSGwith burners.
9-2 Combustion Turbine and Unfired HRSG with Bypass Stack. (See Figure 9-2.)
Bypass stack
[ . / Stack
HRSG
Combustion turbine
Figure 9-2 Combustion turbine and unfired HRSG with bypass stack.
9-2.1 Gas Bypass Stack and Damper System.
9-2.1.1 The gas bypass stack and damper housing shall be capable of withstanding a transient design pressure without permanent deformation due to yield or buckling of any support member. This minimum design pressure shall be two times the design pressure of the HRSG iniet duct but not less than +20 in. of water (+5.0 kPa).
9-2.1.2 Means shall beprovided for recognizing leakage of combustion turbine exhaust gas past the closed damper and into the HRSG bygas analysis or some other means. Alternatively, a sealing air fan and double damper system shall be provided.
9-2.1.3 Convenient access to the inside of the ducts shall be provided.
9-2.1.4 The damper system for the gas bypass stack shall be either fully open to the HRSG or fully open to the bypass stack. Intermedi- ate positions of the damper(s) shall be permitted only if combustion turbine exhaust or air flow quantity and direction through the HRSG are monitored and alarmed.
9-2.1.5 During planned maintenance outages the following shall be accomplished:
(a) The damper system shall be inspected for tightness when the damper(s) is fully closed;
(b) The damper operating devices shall be checked for proper operation and positioning; and
(c) Correct damper system positioning during purge, start-up, and shutdown shall be verified by simulation.
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NFPA 8506 - - A95 ROP
9-2.2 Monitoring.
9-2.2.1 In addition to the requirements in 6-2.3, combustion turbine exhaust or air flow through the HRSG shall be continuously recorded and trended if the bypass stack damper(s) can be maintained in an intermediate position.
9-2.2.2 In addition to the requirements in 6-2.3, the position of the bypass stack damper(s) shallbe continuously monitored.
9-2.3 In addition to the required alarms in 6-3.2, reverse flow through an HRSG (air flow from exhaust stack through HRSG to bypass stack) shall be alarmed if the bypass damper system can be maintained in an intermediate position. (See 9-2.1.4.)
9-2.4 Interlocks.
9-2.4.1 As a supplement to the combustion turbine starting permissive interlock in 5-2.3.1 (e) [position of the stack closure damper (if provided) ], the gas bypass stack damper(s) in the bypass position shall be interlocked to permit combustion turbine start-up regardless of stack closure damper position.
9-2.4.2 As a supplement to the combustion turbine tripping interlock in 5-2.3.1 (e) [position of stack closure (if provided) not correct], it shall be permitted to position the gas bypass damper(s) to the bypass position as an alternative to tripping the combustion turbine.
9-2.5 Purge.
9-2.5.1 Following a combustion turbine shutdown, a unit purge shall be completed as required in Section 7-4 prior to admitting combus- tion turbine exhaust gas into the HRSG.
9-2.5.2 Following the purge as required in 9-2.5.1, it shall be permitted to interrupt the flow through the HRSG using the gas bypass stack, provided there is no fuelsource in the HRSG. Combustion turbine exhaust flow shall be permitted to re-enter the HRSG at a later time without repurgin~, provided the combustion turbine has been in continuous operauon with no trips or misfires.
9-2.5.3 The combustion turbine shall be permitted to purge and operate with combustion turbine exhaust through the bypass stack without purging the HRSG. However, combustion turbine exhaust gas shall not be directed into the HRSG unless a purge as required by 9-2.5.1 and 9-2.5.2 has been performed.
9-3 HRSG Burners with Augmented Combustion Air Supply. (See Figure 9-3.)
Stack Burners
k.._
Combustion turbine ~ " ) F a n . . ~ k.XN..~ HSRG
Figure 9-3 HRSG burners with augmented combustion air supply.
9-3.1 The fan(s) supplying augmented combustion air to the HRSG burners shall be operated in accordance with the manufacturer's instructions.
9-3.2 Interlocks.
9-3.2.1 The fan(s) supplying augmented combustion air to the HRSG burners shall be proven to be operating prior to initiating and during a unit purge. (See Section 7-4.)
9-3.2.2 In addition to the master fuel trip requirements in 6-4.3, an HRSG burner master fuel trip shall be initiated by loss of air from fans supplying augmented combustion air to the HRSG burners.
94 Combustion Turbine and F'n'ed HRSG with Bypass Stack. (See Figure 94.)
Bypass s t . ~ 1 1 L HSRG Stack
.
Burners
Combustion turbine
Figure 94 Combustion turbine and fired HRSG with bypass stack.
9-4.1 Gas Bypass Stack and Damper System. The requirements in 9- 2.1 shall be satisfied.
94.2 In addition to the requirements in 6-2.3, combustion turbine exhaust or air flow through the HRSG shall be continuously recorded and trended.
94.3 In addition to the required alarms in 6-3.2, low flow and reverse flow through an HRSG (air flow from exhaust stack through HRSG to bypass stack) shall be alarmed if the bypass damper system can be positioned in an intermediate position. (See 9-2.1.4.)
94.4 Interlocks.
94.4.1 As a supplement to the combustion turbine starting permissive interlock in 5-2.$.1 (e) [position of the stack closure damper (if provided)], the gas bypass stack damper(s) in the bypass position shall be interlocked to permit combustion turbine start-up regardless of stack closure damper position.
9-4.4.2 As a supplement to the combustion turbine tripping interlock in 5-2.$.1 (e) [position of stack closure (if provided) not correct], it shall be permitted to position the gas bypass damper(s) to the bypass position as an alternative to tripping the combustion turbine.
94.4.3 In addition to the required interlocks in 64.3, an HRSG burner master fuel trip shallbe initiated if the bypass stack damper is not closed.
Exception: I f the HRSG system is designed for maintaining the stack bypass damper(s) in an intermediate position, the interlock in 9-4.3 shall not be required provided HRSG burner operation is interlocked with turbine exhaust gas flow through the HRSG burners.
94.5 Purge.
9-4.5.1 Following a combustion turbine shutdown, a unit purge shall be completed as required in Section 7-4 prior to admitting combus- tion turbine exhaust gas into the HRSG.
94.5.2 Following thepurge as required in 9-4.5.1, interruption of the flow through the HRSG using the gas bypass stack shall cause loss of purge of the HRSG. Combustion turbine exhaust flow shall not be permitted to re-enter the HRSG at a later time without repurging the HRSG as required in 9-4.5.1.
9-4.5.3 The combustion turbine shall be permitted to purge and operate with combustion turbine exhaust through the bypass stack without purging the HRSG. However, combustion turbine exhaust gas shall not be directed into the HRSG unless a purge as required by 9-4.5.1 and 9-4.5.2 has been performed.
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N F P A 8 5 0 6 m A 9 5 R O P
9-5 Combustion Turbine and HRSG with Fresh Air Firing Capabil- ity. ( See Figure 9-5.)
Bypass stack
turbine ~f ~ _ J ' HRSG
Fan
Note: Fan could alternately be located between HRSG outlet and stack with combustion turbine
exhaust or fresh air or both to burners and HRSG.
lr~,mre 9-5 Combustion turbine and HRSG with fresh air firing capability.
9-5.1 Gas Bypass Stack and Damper System. The requirements in 9- 2.1 shall be satisfied.
9-5.2 In addition to the requirements in 6-2.$, combustion turbine exhaust or air flow through the HRSG shall be continuously recorded and trended.
9-5.3 In addition to the required alarms in 6-3.2, low flow and reverse flow through the HRSG (air flow from exhaust stack through HRSG to bypass stack) shall be alarmed if the bypass damper s~tem can be posiu' "oned in an intermediate position. (See 9-2.1.4)
9-5.4 Interlocks.
9-5.4.1 As a supplement to the combustion turbine starting permissive interlock in 5-2.3.1 (e) [position of the stack closure damper (if provided) ], the gas bypass stack damper(s) in the bypass position shall be interlocked to permit combustion turbine start-up regardless of stack closure damper position.
9-5.4.2 As a supplement to the combustion turbine tripping interlock in 5-2.3.1 (e) [position of stack closure (if provided) not correct], it shall be permitted to position the gas bypass damper(s) to the bypass position as an alternative to tripping the combustion turbine.
9-5.4.3 A combustion turbine trip shall cause a master fuel trip of the HRSG burners as required in 6-4.3 unless adequate flow through the HRSG burners can be maintained by the fresh air supply.
9-5.5 Purge.
9-5.5.1 Following a combustion turbine shutdown, a unit purge shall be completed as required in Section 7-5 prior to admitting combus- tion turbine exhaust gas into the HRSG.The fan for supplying combustion air for fresh air firing shall be in operation prior to and during the unit purge.
9-5.5.2 Following the purge as required in 9-5.5.1, interrupting the flow through the HRSG using the gas bypass stack shall cause loss of purge of the HRSG. Combustion turbine exhaust flow shall not be permitted to re-enter the HRSG at a later time withOUt repurging the HRSG as required in 9-5.5.1. It shall be permitted to perform this purge with fresh air supplied by the fan used for fresh air firing in accordance with 9-5.6.2.
9-5.5.3 The combustion turbine shall be permitted to purge and operate with combustion turbine exhaust through the bypass stack without purging the HRSG. However, combustion turbine exhaust gas shall not be directed into the HRSG unless the requirements of 9-5.5.1, 9-5.5.2, or 9-5.6.3 have been satisfied.
9-5.5.4 Purge of the HRSG burners and HRSG using fresh air shall be permitted without operation or purging of the combustion turbine provided the gas bypass dampers are in the bypass position.
9-5.6 Sequence of Operations for Fresh Air F'n'ing.
9-5.6.1 The sequence of operations defined in Section 7-3 shall be followed with the exception that fresh air supply rather than combustion turbine exhaust shall be used.
9-5.6.2 Unit purge as required in Section 7-5 shall be performed with an air flow of not less than 25 percent of the full load fresh air mass flow. Unit purge shall provide not less than 5 volume changes of the HRSG enclosure and shall be for a period of not be less than 5 minutes.
9-5.6.$ A later start-up of the combustion turbine shall be permitted only by purging and start-up of the combustion turbine with exhaust flow through the bypass stack. Once stable operation of the combustion turbine is achieved, combustion turbine exhaust shall be permitted to flow through the operating HRSG with or without supplementary fresh air.
9-5.6.4 Normal shutdown using flesh air supply shall follow the reverse procedure of that used during start-up. A unit post purge shall be performed at an air flow not less than the purge rate mass air flow for a period of not less than 5 minutes.
Chapter 10 Fuilylrtred Systems
Reserved
Chapter 11 Referenced Publications
11-1 The following documents or portions thereof are referenced within this standard and shall be considered part of the require- ments of this document. The edition indicated for each reference is the current edition as of the date of the NFPA issuance of this document.
11-1.1 NFPAPublication~ National Fire Protection Association, 1 Batterymarch Park, P.O. Box 9101, Quincy, MA 02269-9101.
NFPA 70, NationalElevtrical Code, 1993 edition.
NFPA 85C, Standard for the Prevention of Furnace Explosions~Implosions in Multiplo Burner Boiler-Fumaces, 1991 edition.
11-1.2 ASME Publication. American Society of Mechanical Engineers, 345 East 47th Street, New York, NY 10017.
ASME B31.1-1992, Code for Preesure Piplng-- Power Piping.
Appendix A Explanatory Material
This Appendix is not a part of the requirements of this NFPA document but is included for informational purposes only.
A-4-3.1 The following provides a minimum list of areas that should be considered during the design evaluation:
(a) Single vs. multiple steam pressure levels;
(b) Allowable combustion turbine exhaust back pressure;
(c) Supplementary, auxiliary, or augmented firing;
(d) Combustion turbine exhaust bypass system;
(e) Corrosiveness and fouling of by-products of combustion (fin vs. bare tube, metallurgy, cold end metal temperature);
(f) Single or multiple fuels;
(g) SCR or other environmental control systems;
(h) Heat transfer surface cleaning (during operation and shutdowns) and inspection;
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(i) Freeze protection;
(j) Rapid start, operating transients, thermal shock;
(k) Dry operation;
(1) Protective systems;
(m) Degree of automation and complexity of control systems;
(n) Operator interface;
(o) Overall system performance evaluation, feedback, and iteration (expert system data base consideration);
(p) Description of start-up validation test program (reference test cases and simulator data library when available);
(q) Combustion turbine (purge exhaust);
(r) Bypass stack, damper;
(s) Duct burner, fuel oil-fired or fuel gas-fired or both;
(t) HRSG and interconnecting ducts;
(u) Forced draft fan, induced draft fan, or discharge stack, in any combination;
(v) Burner management system logic;
(w) Flame monitoring and tripping systems;
(x) Combustion control system;
(y) Power supplies configuration and codes;
(z) Piping system configuration and codes;
(aa) Operating information;
(bb) Input /output selection;
(cc) Detail design;
(dd) Information displayed;
(ee) Data transmission (noise accuracy considerations);
(if) Programmable logic controller software and hardware considerations;
(gg) Requirements for operation from a remote location; and
(hh) Initial control tuning.
A-4-$.2 Dynamic simulation, when utilized, should include development of the following:
(a) Configuration and data" initialization;
(b) Plant behavior knowledge development;
(c) Preliminary control system design and tuning;
(d) Validation of operating requirements (system performance); and
(e) Transients and ramps for intended and unintended operation.
A-5-$ General. The operation of a combustion turbine HRSG is fundamentally different from its equivalent power or process steam generator. Fundamental differences exist between the two typesof equipment that calIfor a different approach to the operating procedure. These differences are as follows:
(a) The combustion turbine is an internal combustion engine. The engine burns a lean mixture of fuel with compressed air. The hot pressurized combustion gasses expand from the combustion chamber, through a series of rotating turbine wheel and blade assemblies, resulting in shaft power output and hot turbine exhaust gas discharge to the HRSG. Turbine exhaust gas will be hot with a reduced oxygen content relative to air.
(b) The design of the HRSG differs from that of a regular steam generator in that in most cases the HRSG is designed to utilize the residual heat from the combustion turbine exhaust gas, with some supplementary firing by the duct burner, if so required.
(c) Because the combustion turbine is a volumetric machine, combustion turbine exhaust gas is discharged within closely prescribed limits, with the oxygen content varying as a function of load.
(d) Purge is a function of precombnsfion turbine start and usually is accomplished by a variety of methods. Duct burner purge will be limited to a one-time requirement as long as the combustion turbine has not ~ipped.
(e) Duct burner controlled air fuel ratios are neither possible nor desired. As vast quantities of turbine exhaust gas are utilized, far in excess of the stoichiometric requirements of the fuel, fuel-rich conditions cannot inherently occur under normal controlled operating conditions.
(f) Many types of burners are available for HRSG systems. The burner may consist of a number of parallel tubes or runners placed in the duct to give the required heat release. This is commonly used for gaseous fuels and is referred to as a "grid" burner. Alternatively, wail-mounted burner systems with parallel flame holders within the duct may be used for liquid fuels. In-line register type burners manufactured in Europe also have been used. Ignition systems for either of these burner types can be Class 1, Class 2, or Class igniters.
A-5-$.2.2.2 Aunospheric vent valves located between shutoffvalves are intended to relieve any gas pressure that may build up due to failure of the first (upstream) shutoffvaive. This minimizes the potential for leakage into an idle HRSG. To perform properly, these valves should be large enough to relieve gas to aunosphere at a rate equal to the potential leakage rate. In absence of other justification, vent pipe sizes and vent valve port diameters should conform to Table A-5-3.2.2.2. When vents are manifolded fi'om safety shutoff systems, the cross-sectional area of the manifold pipe should be equal to, or greater than, the sum of the cross-sectional areas of the two largest vents involved.
Table ~5-$.2.2.2
Mh*imnm Shutoff S ~ t m Veat Port
< 1 1/2" 3/4" 2" 1"
2 1/2" to 3" 1 1/4" 31/2" 1 1/2"
4" to 5" 2" 5 1/2" to 6" 2 1/2"
8" 3 1/2" > 8" 15% of supply line
CFOLq-~C. a t i l t
~b5-$.2.$.8 A permanent and ready means for making easy, accurate periodic tightness tests of the main safety shutoffvalves and individual burner safety shutoff vaives generally is not feasible for fuel oil systems. However, visual checking of the burners and -combustion area prior to starting operation can determine ffleakage has occurred. Also, pressurizing the oil supply header with the individual burner safety shutoffvaives and the recirculating valves closed will indicate if leakage is present. [foil pressure remains within defined limits, it can be concluded that the individual burner safety shutoffvaives are not leaking.
A-5.4 Proper design considerationshould be given to internal insulation and cover plates such that detailing is provided for the following."
(a) Insulation thickness and external casing temperature calculations;
(b) Internal plate thickness and material;
(c) Pin pitch, diameter, and fixing methods; and
(d) Welding procedures.
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A-54.1 HRSG Enclosure. The external skin temperature and acoustical design should comply with the requirements of OSHA standards, local regulations, or other applicable regulations.
A-5-4.3 Any through-duct penetrations should have proper provision for expansion and sealing. Where pipes, tubes, headers, or drums make a through-duct penetration, calculations should be provided showing that the differential expansion and the sealing make proper provision for such expansion.
A-5-4.4 Access should be provided for proper maintenance and repair. This should include personnel access where the ducting allows. All pressure parts should have access for periodic inspection and for mandatory hydraulic tests.
A-5-4.8.1 Consideration should be given in design to minimize pockets that could trap combustible materials.
A-5-4.8.2 Drains should be provided in all ducts or enclosures where fluid accumulation is possible.
A-5-5 Some HRSG systems are required by air-permitting authorities to install selective catalytic reduction systems to reduce the emissions of NO x. As this system has a narrow range of optimum operating temperature and is subject to maximum temperature limitations lower than many combustion turbine full load exhaust temperatures, it usually is installed between heat transfer surfaces within the HRSG.
The chemical process of reduction requires the addition of ammonia to reduce NO x to nitrogen and water in the presence of the catalyst. Additionally, ffthe fuel contains sulfur, a reaction that results in the formation of ammonium bisulfate can occur. This material tends to deposit on both catalyst and metallic surfaces downstream of the reactor section, primarily at low temperatures. Although troublesome from a corrosion, fouling, and material life standpoint, ammonium bisulfate does not directly affect flame safety.
For use in a selective catalytic reduction (SCR) system, common practice is to use either anhydrous or aqueous ammonia as the reducing agent. These chemicals are not interchangeable, requiring specific system design for the form to be used at a particular installation. Both forms, on release, are considered a potential health hazard. Ammonia gas is flammable in air at concentrations between 16 to 25 percent by volume. Such concentrations usually are not encountered. The system should provide the necessary features to assure such concentrations cannot occur during abnormal conditions.
Aqueous ammonia usually is stored in a closed vessel to prevent the release of vapor. Such vessels are designed for low (less than 50 psig) pressures and only approach the design pressure under high ambient temperature conditions. Due to the corrosive nature of ammonia, material selection is an important consideration.
Anhydrous ammonia is stored in a concentrated liquid/vapor form within closed vessels. Under ambient temperature conditions, higher pressures, than observed can result with aqueous ammonia. Vessels built to the ASME, Steam Generator and Pressure Vessel Code are required with design pressures of 250 psig or higher. The following sources provide additional information and requirements for storage and handling of anhydrous ammonia: Pamphlet G-2, Anhydrous Ammonia; 29 CFR 1910.111, Storage and Handling of Anhydrous Ammonia; ANSI K61.1-1981, Safety Requirements for the Storage & Handling of Anhydrous Ammonia.
A-6 Guidelines for the Application of Distributed Control Systems.
NOTE: The user of NFPA 8506 is encouraged to use judgement in the application of these guidelines for all process and safety functions contained in the distributed control system. This appendix section is not intended to apply specifically to burner management systems.
(1) Data Transmission.
(a) Every input should be sampled at an interval no longer than 1 second. Every output should be updated at an interval no longer than 1 second.
(b) For protective actions, the system should be able to convert a changed input sensor value to a completed output control action in less than 250 milliseconds.
(c) Changes in displayed data or status should be displayed within 5 seconds.
(d) Data acquisition and transmission systems should be protected from noise plck-up and electrical interference.
(e) In redundant systems the data links should be protected from common mode failures. When practical, redundant data links should be routed by separate paths to protect against physical damage that disables both data links.
(2) Hardware.
(a) The hardware selected should have adequate processor capacity to perform all the functions required for start-up sequenc- ing, normal operation alarming, monitoring, and shutdown of the controlled equipment. Capacity also shouldbe available for data storage and sorting; this may be in a separate processor.
(b) Selection should take into consideration the requirements of reliability, maintainability, and electrical classification.
(c) The hardware should provide for automatic tracking between auto/manual functions to allow for immediate bumpless transfer.
(d) The hardware should be capable of stable dynamic control.
(e) The hardware should be capable of thorough serf-diagnosis.
(f) Gonsideration should be given to all levels and types of electrical interference that canbe tolerated by the hardware without compromising its reliability or effectiveness.
(3) Software.
(a) The software package should be designed to include all logic to provide a safe and reliable control system. When the software calls for the operation of a field safety device, a feedback signal should be provided to prove that the requested operation has taken place, and an alarm should be actuated if the action is not con- firmed in a specified time.
(b) The software package should be checked to ensure that no unintended codes or commands are present (e.g. viruses or test breaks). The software package should be tested and exercised before being loaded into the plant site computers or processors.
(c) Failsafe operation should be obtained through a thorough and complete analysis of each control loop and by making provisions for failure of that loop (i.e., valve/actuator) to go to a fail safe position.
(d) The software system should be protected from inadvertent actions from operators and also should be tamper-proof.
(e) Written procedures should define the functions the operator can and cannot access, and the functions that require additional authorization to access.
(f) The software may allow provision for authorized on-line changes of the timers and set-points without compromising the safety of the operating equipment.
(g) The software should implement and enhance the self- diagnostic hardware that has been provided.
A-6-6.4 A sequence of events recorder, when provided, should time- tag events with a resolution of 10 milliseconds or less.
A-7-1.1 Special Problems. Common hazards are involved in the combustion of solid, liquid, and gaseous fuels. Additionally, each of these fuels has special hazards related to its physical characteristics.
(1) Gas Firing. The following items should be considered in the design of the fuel gas firing systems:
(a) Gas is colorless; therefore, a leak usually cannot be visually detected. Also, reliance cannot be placed on detection of a gas leak by the presence of odor.
(b) Potentially hazardous conditions are most likely to occur within buildings, particularly where the gas piping is routed through confined areas. In the latter instance, adequate ventilation shouldbe provided. Outdoor steam generators tend to minimize confined area problems.
(c) Natural gas may be either ~wet" or "dry." A wet gas usually implies the presence of clistillate, which may be characteristic of a particular source. In the case of such a wet gas, the carryover of
112
N F P A 8506 - - A 9 5 R O P
distillate into the burners could result in a momentary flameout and possible reignition. Reignition could result in an explosion. Therefore, special precautions should be taken with wet gas supply systems. (For details see NFPA 54, National Fuel Gas Coda)
(d) Discharges from relief valves or from any other form of atmos?heric vents can become hazardous unless special precautions are taxen.
(e) Maintenance and repair of ~ piping can be hazardous unless proper methods are used for purgqng and recharging the line before and after making the repairs. (See NFPA 54, National Fuel Gas Code.)
(2) Oil Firing. The following items should be considered in the design of the fuel oil firing systems:
(a) Firing of oil fuel into an HRSG can create a special hazard by causing soot accumulations in low temperature sections.
(b) Small oil leaks can result in serious fire damage.
(c) Water or sludge in fuel oil storage tanks or improperly located suction takeoffs from the storage tank may result in hazardous interruptions or pulsations of the fuel supply to the burners. A flame-out, either immediately or at a later time, may result because of plugged strainers or burner tips.
(d) Widely different characteristics offuel oil from either asingle source or multiple sources may result in a significant change in Btu input rate to the burner(s). Different shipments of fuel oil with dissimilar characteristics can cause a precipitation of sludge that can lead to hazards as described in A-7-1.L
(e) There is the ever-present hazard of inserting an oil gun in the burner assembly without a tip, new gaskets, or sprayer plate. This can result in an unsafe operating condition.
(f) Clear distillate fuels have low rates of conductivity and will ( l~era te static electrical charges in the fuel stream that may be
gerous unless flowing velocities are limited. (See NFPA 77, Recommended Practice on Static Electricio, and API-RP 2003, Recom- mended Practice for Protection Against Ignitions Arising Out of Statlc Lightning and Stray Currents).
(g) Maintenance and repair of oil piping can be hazardous unless proper methods are used for purging and recharging the line before and after making repairs (see NFPA 31, Standard for the Installation of Oil-Burning Equlpmen O.
(h) The incompressibility of fuel oil can create very rapid transients in oil flow through operating burners upon:
(i) Rapid operation ofoil supply valve;
(ii) Rapid operation of individual burner shutoffvalves; and
(iii) Rapid operation of regnlatingvalve in the return oil line from the burner header (on systems using this type of control).
($) Fuel Oil--General Considerations.
(a) The term fuel oil refers to liquid fuels with widely differing characteristics. Afuel oil burning system is designed for a specific range of oil characteristics. Attempting to bum an oil whose characteristics differ widely from those for which the system was designed can cause serious operating difficulties and potential safety hazards. Hence, care must be exercised to ensure that fuel oil received at a plant is within the specific range of the handling and burning equipment.
(b) The more important characteristics of fuel oils are defined in ASTM specifications. It is relatively simple to identify oils that require special provisions for storing, heating, pumping, atomizing, etc. Generally speaking, grades 2 and 4 havelower viscosities and less water and sediment than grades 5 or 6 and hence require fewer special provisions to ensure proper handling and burning. However, most boiler fuel oil systems are designed for the heavier grades 5 and 6; hence, such systems include provisions for preheating these usually viscous fuels. Furthermore, more care is required in design and operation of fuel oil systems supplied with grade 6 oil than with the other ASTM grades is needed to avoid flame-outs attributable to interruptions or pulsation of the fuel supply, or plugging of strainers or burner tips.
(c) All of the followinl[ characteristics may have a bearing upon properly and safely burmng fuel oils:
(i) Fuel oil is a complex mixture of hydrocarbons of differing molecular weights, and boiling and freezing points. When subjected to sufficiently high temperature, accumulations of the fuel will partially decompose and volatilize, thus creating new liquid, gaseous, and solid fuels with unpredictable properties.
(ii) Fuel oil should be introduced into the furnace as an extremely fine mist to intimately mix with the combustion air in order to burn quickly and completely. In boilers, this is accom- plished by spraying through small orifices with high pressure drops (mechanical atomization) or by using steam or air to break up small oil streams. Viscosity and volatility are characteristics of the oil that indicate ease of atomization.
(iii) Viscosity affects ease of pumping and atomization. Tempera- ture significantly affects viscosity.
(iv) Flash point is an indicator of volatility and, thus, of potential for combustible vapors.
(v) Some fuel oils contain constituents that, when overheated, may decompose and form solids or may solidify when exposed to low ambient temperatures. The presence of such solids in the fuel may cause interruptions.
(4) Hazards peculiar to crude oil firing.
(a) Nature of Crude Oils. "Crude oil" signifies petroleum that is withdrawn from the ground and treated in separators as needed to remove most of the dirt and water and enough gaseous constituents to permit safe and convenient shipping.
(b) With regard to safety, the basic difference between crude oils and the grades of fueis defined in ASTM D396, Standard Speci.t.Fwation for Furl Oils, is that crude oils contain dissolved light combustible hydrocarbons. These light volatile materials may be released during storage, handling, or upon heating. Because of this nature of crude oils, appropriate and adequate provisions should be made to safely handle, store, and burn crude oils in steam boiler plants. Failure to observe the necessary design, installation, operating, and mainte- nance procedures can result in disastrous fires or explosions, or even personal injury, including possible inhalation of toxic (hydrogen sulfide) gas.
(c) Crude oil properties vary considerably. Therefore, it is desirable that flexibdity be built into the facility to accommodate the expected range of properties.
(d) Crude oil characteristics are classified from laboratory tests, and all limitations must be agreed to by the seller and buyer. This is in contrast to fuel oils, whose properties are controlled within limits by "refining" to meet internationally recognized standards.
(e) The flash points of crude oils can range from below zero to over 150°F (65.6°C). Most crude oils contain volatile light ends not present in fuels meeting the requirements of ASTM D396, Standard Specification for Fuel Oils. Some of these volatile hydrocarbons, such as propane, butane, and pentane, may volatilize upon leakage or other release of crude oil to the atmosphere; because this vaporized material is heavier than air, it may travel for considerable distances and accumulate as a hazardous concentration.
(f) Storage and Handling of Crude Oils. Extensive treatment of this subject is beyond the scope of this standard. However, the safety aspects are so broad that some clarification is essential. Special attention is directed to the following considerations:
(i) Adequate ventilation is essential in areas where oil leakage may occur, such as at pumps, heaters, strainers, and burner fronts, or where maintenance may be performed. Confined fuel-handling areas and burner fronts should be adequately ventilated and forced air ventilation used where necessary.
(ii) Crude oil storage tanks usually conform to either API-620, Recomraended R u ~ for Design and Construction of Larg~ Welded, Low- Pressure Storage Tanks, or API-650, Welded Steel Tanks for Oil Storage.
Open top or covered floating-roof tanks are recommended to minimize possible fires and explosions and to reduce combustible vapor losses, particularly when the flash point is below 100°F (37.8°C).
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N F P A 8506 - - A95 R O P
In fixed-roof tanks the internal space above the liquid may contain an explosive vapor when used with crude oil service. For protection a fixed-roof tank can be provided with an internal cover floating on the oil and the space between cover and roof adequatelyvented in accordance with API-650, Appendix H, Spacing. Fire protection should be based upon fixed-roof tank requirements. (S~ a/so API- 2003, Section 3.5.1.) Existing fixed-roof tanks without internal floating covers can be inert-gas blanketed if the flash point might be below 100°F (37.8°C).
Tanks should be spaced and storage areas graded, drained, and diked in accordance with NFPA 30, F/ammabb and CombustiblsLiquids Cod~ to contain spills in the event of tank rupture or overflow.
(iii) Plant layout and tank location should indude consideration of "boil-over" hazards, particularly with fixed-roof tanks. Diking is not a complete protection against the boil-over fire phenomenon. Therefore, adequate fire protection and provisions for emergency flow paths should be included.
(iv) Consideration should be given to agitation or other means to prevent settling of sludge in crude oil storage tanks.
(v) Crude oil piping and valves should be steel. Steel-cased pumps and strainers, etc., are. recommended to resist possible fire damage and release of fuel into the flames.
(vi) Pump selection criteria should include consideration ofoil vapor pressure, abrasive and corrosive contaminants, mechanical shaft-seals to minimize leakage, lubricity of the oils. In particular, pump suction pressures must be high enough to preclude vaporiza- tion and cavitation with the oils to be handled.
(vii) Ignition sources should be minimized. All piping should be properly bonded and grounded in accordance withNFPA 77, Rm,nnmu~ Practice on Static E / ~ c / 9 .
(viii) Consideration should be given to detecting and monitoring combustible gases in areas where they may accumulate.
(ix) Access to crude oil handling areas should be restricted; smoking should be prohibited in designated locations. Work likely to involve flame, sparks, etc., such as welding or burning, should be done only after a safety check has been performed on the area. For cutting and welding precautions, refer to NFPA 51, Standard for the Design and Installation of Oxygen-Fud Gas Systems for Wddin~ Cutting, and A///ed Proce~es, and NFPA 51B, Standard for Fire Prevention in Uss of Cuttingand WddingProcess~ Each areashould be checked with a portable combustible gas tester before work that may involve possible flames or ignition sources is started.
(x) Where potential toxic gas hazards may exist, personnel should be provided with protection when cleaning strainers, replacing pumps, gauging or sampling tanks, etc. Appropriate operating procedures and personnel training are essential.
s
Supply T F (
C l
Igniter
C5 Igniter ShutoffAtmospheric Vent Valve E Igniter Safety ShutoffValve F Igniter Fuel Control Valve S Fuel Pressure Gauge T Manual.Shutoff Valve
Figurn A-7~.4.2.1(a) Typical duct burner gas i~,nition system of a single dement or multiple dements f'wed mmultaneously.
S
i i ugh, Supply " " " T ' % ' f (
Igniter
E Igniter Safety ShutoffValve F Igniter Fuel Control Valve (optional) O Cleaner or Strainer S Fuel Pressure Gauge T Manual Shutoff Valve
lrlgure A-7-5.4.2. It]b) Typical duct burner oil ignition system of a single burner or multiple burners fired simultaneously.
114
N F P A 8506 - - A95 R O P
Supply
Vent Io Almosphere
O. J M A A ~
To IgnJllon Syslem F
See Fig. ~ 7 ~.-'.~.~,~
$
v ~ ~ llain Burner
A Main Burner Safety Shutoff'Valve C 2 Main Burner ShutoffAtmospheric Vent Valve D Main Fuel Control Valve J Fuel Pressure Regulator (optional) M Flow Meter O Cleaner or Strainer Q High Fuel Pressure Interlock R Low Fuel Pressure Interlock S Fuel Pressure Gauge T Manual Shutoff Valve
Figure A-7-5.4.2.1 (c) Typical main gas duct burner system of a single element or multiple elements Frred simultaneously.
115
N T P A 8506 ~ A95 R O P
Ihkarn t~
Q - ¢mdlan: ~ e sh411 be IH'Qvlded IQ pFeVq.ltl or re l i eve O~II:OS$ pressur~ between lhalm valves
011
S R U qQ S
A A Y
I
. Z,
Trap
U ~ b~mDr
A Main Burner Safety ShutoffValve D Main Fuel Control Valve H Recirculating Valve (optional for unheated oil) M Flow Meter N Low Atomizing Pressure Interlock 0 Cleaner or Strainer R ~ Low Temperature or High Viscosity Alarm Interlock (optional for unheated oil)
Low Fuel "Pressure Interlock S Fuel Pressure Gauge T Manual Shutoff Va'lve T5 "" • Atonatzing Medium Individual Burner Shutoff Valve, Automatic U Temperature Gauge (optional for unheated oil) W scavenging Valve Y Check Valve Z Differential Pressure Control Valve Z1 Differential Pressure Alarm and Trip Interlock
lr~ure A.7-S.4.2.1(d) Typical single main oil duct burner system--.steam or air atomizing.
116
NFPA 8506 - - A95 RO P
Supply T F"
Ro I~
G
Ignller (Typical)
Cs
£
Other
C4 Igniter Header Atmospheric Vent Valve (optional) C5 Individual Igniter Atmospheric Vent Valve E Igniter Header Safety ShutoffValve F Igniter Fuel Control Valve G Individual Igniter Safety Shutoff Valve K Pressure Relief Valve RQ High Fuel Pressure Interlock
Low Fuel Pressure Interlock R1 Low Fuel Pressure Interlock (alternate location) S Fuel Pressure Gauge T Manual Shutoff Valve
lr~gure A-7-5.4.2.2(a) Typical duct buruer gas igniter system.
117
N F P A 8506 - - A95 R O P
0•CI - 3 ~ - . - ~ ~"" . ~ ~ T - ] I - "- \ (Typ,0o,)
Supply :
o., , i~;~'o'~, . . Room
[ ~ To Ignit Ion System See F'lg. ~ : : . : . : ' _ )
A Main Safety Shutoff Valve B Individual Burner Safety ShutoffValve CI Main Burner Header Charging AtmospherlcVent Valve (optional) C2 Main Burner Header Shutoff Atmospheric Vent Valve D Main Fuel Con~'ol Valve D1 Main Fuel Bypass Control Valve (optional)
Fuel Pressure Regulator (optional) JK Pressure Relief Valve M Flow Meter O Cleaner or Strainer QQ2 Burner Header High Fuel Pressure Interlock
High Fuel Supply ~ressure Interlock R Burner Header Low Fuel Pressure Interlock R I Burner Header Low Fuel Pressure Interlock (alternate location for R) sR Low Fuel Supply Pressure Interlock
Fuel Pressure Gauge T Manual Shutoff Valve
Ir~ure A-7-5.4.2.2(b) Typical main gas duct burner system.
118
NFPA 8506 - - A95 R O P
o i i . . . , ol, ~ V Supply T
Sc:avmglng umk~m Y W
S ~ I1 Igni l t r " Y (Typical)
!~Pe Other
.m':~l~%.,ol,..)
E Igniter Safety ShutoffValve F Igniter Fuel Control Valve G Individual Igniter Safety Shutoff Valve O Cleaner or Strainer R Low Fuel Pressure Interlock S Fuel Pressure Gauge T Manual Shutoff Valve W Scavenging Valve Y Check Valve
lr~ure A-7-~.4.2.2(c) Typical duct burner mechanical atomizing light oil igniter system.
119
N F P A 8506 - - A95 R O P
Scavenging Medlu'n
Supply T
.®
Y w
z <
, < Igniter (Typical)
E Igniter Safety ShutoffValve F Igniter Fuel Control Valve G Individual Igniter Safety Shutoff Valve 0 Cleaner or Strainer R Low Fuel Pressure Interlock S Fuel Pressure Gauge T Manual Shutoff Valve W Scavenging Valve Y Check Valve Z Differential Pressure Control Valve Z1 Differential Pressure Alarm and Trip Interlock
Ftgure A-7-~.4.2.2(d) Typical duct burner steam or air atomizing light oil igniter system.
120
N F P A 8 5 0 6 m A 9 5 R O P
o,, Supply
Return H
S RI
If I)I
R | PSL v o01TSL } ~ -
~ ~ Other Moin Rurners
A Main Safety ShutoffValve B Individual Burner Safety ShutoffValve D Main Fuel Conu'ol Valve D1 Main Fuel Bypass Control Valve (optional) H Redrculating Valve (optional for unheated oil) II Circulating Valve (optional for unheated oil) M Flow Meter O Cleaner or Strainer RQQ Low Temperature or High ViscosityAlarm Switch
Burner Header Low Fuel Pressure Interlock R 1 Low Fuel Pressure Interlock S Fuel Pressure Gauge T Manual Shutoff Valve W Scavenging Valve Y Check Valve
F'~rure A-7-5.4.2.2(e) Typical main oil duct burner system--mechanical atomizing.
121
N F P A 8506 - - A95 R O P
f
h l u r n N
5 R~
I t DI
Main Ikarne¢ (v~col)
2.22 If Y I~tlum
Z!
®
Stsam M r t t t a d , r
~Jlgm Ig I1~ td~l|um ~ v
A Main Safety ShutoffValve B Individual Burner Safety ShutoffValve D Main Fuel Control Valve
Main Fuel Bypass Control Valve (optional) D1 Recirculatlng Valve (optional for unheated oil) II Circulating Valve (optional for unheated oil) M Flow Meter O Cleaner or Strainer RQQ Low Temperature or High Viscosity Alarm Interlock (optional for unheated oil)
Burner Header Low Fuel Pressure Interlock R1 Low Fuel Pressure Interlock S Fuel Pressure Gauge T Manual Shutoff Valve T5 Atomizing Medium Individual Burner ShutoffValve, Automatic T6 Atomizing Medium Header ShutoffValve, Automatic (alternate to T5) W Scavenging Valve Y Check Valve Z Differential Pressure Control Valve Z1 Differential Pressure Alarm and Trip Interlock
F'~ure A-7-5.4.2.2(f) Typical main oil duct burner symem--steam or air atomizing.
122
N F P A 8 5 0 6 w A 9 5 R O P
Appendix B Industry Experience
(This space is reserved/or future devdopm~L )
Appendix C Referenced Publications
C-I The following documents or portions thereof are referenced within this Standard for irfformational purposes only and thus are not considered part of the requirements of this document. The edition indicated for each reference is the current edition as of the date of the NFPA issuance of this document.
C-2 NFPA Publications. National Fire Protection Association, 1 Batterymarch Park, P.O. Box 9101, Quincy, MA 02269-9101.
NFPA 30, Flammable and Combustible Liquids Code, 1993 edition.
NFPA 31, Standard for the lnstallation of Oil-Burning Equipmen~ 1992 edition.
NFPA 51, Standard for the Design and Installation of Oxygen-Furl Gas Systems for Weldin~ Cuttin~ and Allied Processes, 1992 edition.
NFPA 51B, Standard for Fire Prevention in Use of Cutting and Welding Processes, 1994 edition.
NFPA 54, NationalFuel Gas Cod~ 1992 edition.
NFPA 70, NationalElectrical Code, 1993 edition.
NFPA 77, Recommended Practice on Static Electrido, 1993 edition.
NFPA 496, Standard for Purged and Pressurized Enclosures for Electrical Equipment, 1995 edition.
NFPA 497A, Recommended Practice for Classification of Class I Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, 1992 edition.
NFPA 497B, Recommended Pracace for the Classification of Class H Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, 1991 edition.
NFPA 497M, Manual for Classification of Gases, Vapors, and Dusts for Electrical Equipment in Hazardous (Classified) Locations, 1991 edition.
NFPA 850, Recommended Practice for Fire Protection for Electric Generating Plants, 1992 edition.
C-3 Other Pubfications.
C-3.1 API Pubfications. American Petroleum Institute, 1220 L Street, Northwest, Washington, DC 20005.
API RP 500A, Classification of Locations for Electrical lnstallations in Petroleum Refineries, 1987 edition.
AP1620, Recoramended Rules for Design and Construction of Large, Welded, Low-Pressure Storage Tanks, 1990 edition.
API 650, Welded Steel Tanks for Oil Storag~ 1993 edition.
API RP 2003, Recommended Practice for Protection Against Ignitions Arising Out of Static, Lightning and Stray Currents, 1991 edition.
C-3.2 Federal Government lubrications. U.S. Government Printing Office, Superintendent of Documents, Washington, DC 20402.
OSHA 1910.145.
Code of FederalRegulations, Title 29, Part 1910.111, "Storage and Handling of Anhydrons Ammonia."
C-3.3 k~TM lubrication. American Society of Testing and Materials, 1916 Race Street, Philadelphia, PA 19103-1187.
ASTM D396, Standard Specification for Fuel Oil~ 1992 edition.
C-3.4 CGA Pubfication. Compressed Gas Association, Crystal Gateway 1, Suite 501, 1235 Jefferson Davis Highway, Arlington, VA 22202-4100.
Pamphlet G-2, Anhydrous Ammonia, 1984 edition.
C-3.5 ANSI Publication. American National Standards Institute, 11 West 42nd Street, New York, NY 10036.
ANSI K61.1, Safety Requirements for the Storage and Handling of Anhydrous Ammonia, 1981 edition.
C-3.6 ASME Pubfication.
Steam Generator and Pressure Vessel Code, 1992 edition.
NFPA 8 5 C ~ A95 ROP
P ~ T H
(Log #I 6) 85C- 1 - (Tide): Accept in Principle SUBMITTER= Michael C. Polagye, Factory Mutual Research Corp. RECOMMENDATION: Change title of standard to: "NFPA 8502 Multiple Burner Boiler Operation."
S~ANTIATION: I. Provides consistency with new numbering system for the NFPA 85 series of documents. 2. Simplifies standard tide as was done for 8501 and 8504.
COMMITTEE ACTION: Accept in Principle. Change the title of Standard to: "NFPA 8502 Standard for the Prevention of Furnace Explosions/
Implosions in Multiple Burner Boilers." COMMIq[q'EE STATEMENT: The proposed title does not reflect the content of the document, which addresses more than operation. This new fide is more descriptive.
(Log #47) 85C- 2 - (Tide): Accept in Principle SUBMI'VrER: PeterJ. Gore Wilise, Industrial Risk Insurers RECOMMENDATION: Revise the title to "NFPA 8502 Multiple Burner Boiler Operation." SUBSTANTIATION: Due to the restructuring of the committee, the document numbers have been changed. COMMITrF.AE ACTION: Accept in Principle. COMMITrEE STATEMENT: Refer to Committee Action on Proposal 85C-1 (Log #16).
(Log #156) 85G $ - (Foreword): Accept in Principle SUBMITTER= Bob Lundberg, Los Altos, CA RECOMMENDATION: Repeat the Section in 85G, 1980 Foreword: History and problem. BTM Page 5, and paragraphs on Page 6.
SUI~;TANTIATION: It is considered that high drafts are sole problems. There are special operating, control, and design problems which are not understood. This material should be discussed thoroughly. There is misunderstanding of the trade-offs between explosion and implosion. COMMrVrEE ACTION: Accept in Principle.
Insert a new appendix section as follows: A-5-1 Furnace Implosion Protection. No standard can be
promulgated which will guarantee the elimination of furnace implosions. Chapter 5 involves a balance between complications of reinforcement of eguipment, limitations and reliability of operating procedures, control systems, and interlocks to minimize the occurrence of the conditions leading to furnace implosions.
If worst case conditions are assumed (cold air, high head induced draft fan, forced draft fan flow shutoff, induced draft control dampers open with induced draft fan operating), the furnace cannot be protected by reasonable structural design. With provisions outlined in Chapter 5, the likelihood of furnace
damage is believed to be remote as long as the induced draft fan has reasonable head capability. If the induced draft fan head capability is increased significantly, then special consideration of induced draft fan characteristics or special duct arrangements or special instru- mentation or control should be investigated. COMMrrrEE STATEMENT: This information is more appropri- ately included in Appendix A.
(Log #6) 85C- 4 - (1-1.3): Accept in Principle SUBMITTER: Ray E. Henry, Sargent & Lundy RECOMMENDATION: Add the following new text:
"Units designed in accordance with earlier version of NFPA 85 do not have to upgrade the design pressure of the furnace if the alternation does not increase the risk of a furnace implosion." SUBSTANTIATION: Many units have been designed to previous version of NFPA 85G and have furnace design pressure of-25 in. of water in accordance with the earlier version of the standard code. Some of these units have included draft fans with a test block capability at ambient temperature that is greater than -25 in. of water and even -$5 in. of water which meet the earlier version's of the standard code. NFPA 85C, 1991, would require an increase in furnace design pressure to -55 in. of water i fa "major alteration or extension of exlsting equipment" is made. However, the risk of a furnace implosion may not be any greater, and in many cases, may be lower after the modification. - -
COMMITTEE ACTION: Accept in Principle. COMMITrEE STATEMENT: Refer to action Proposal 85C-5 (Log #44).
(Log #44) 85C- 5 - (1-1.5): Accept in Principle SUBMITTER: PeterJ. Gore Wifise, Industrial Risk Insurers RECOMMENDATION: Remove "major" before alterations, and add: "This standard is not applicable to repairs. If an alteration from
the original design criteria is p,erformed on a subsystem, a complete design analysis of the system shall be performed to verify that the
SUBSTtem has not been altered." ANTIATION: What constitutes a "major" alteration?
COMMrVrEE ACTION: Accept in Principle. Revise text as follows: 1-1.3" This standard is not retroactive. This standard is applicable
to new installations, and to major alterations or extensions that are contracted subsequent to the effective date of this standard. Add.$ In existing units, it is not always practical to strictly apply
the provisions of this standard. Physical limitations may require disproportionate effort or expense with little increase in protection. In such cases, the authority having jurisdiction must be satisfied that reasonable protection is assured.
In existing units it is intended that any condition that represents a serious boiler combustion system hazard be mitigated by application of appropriate safeguards. It is not intended to require modification for conditions that do not represent a si~nificant threat, even though such conditions are not literally m conformance with these requirements. COMMITTEE STATEMENT: The use of the term "major" should not be deleted because it provides clarification of the intent of this paragraph. Appendix information has been added and this paragraph modified for further clarification and to address the concerns of the submitter.
(Log #163) 85C- 6 - (1-1.3): Reject SUBMITrER= William E. Cunningham, United Engineers & Constructors, lnc~ RECOMMENDATION: Add the words:
"This standard shall apply to any retrofit program that involves any of the following: Firing of a new fuel (oil, gas or coal) into a furnace. Addition of
new flue gas cleaning system." SUBSTANTIATION: NFPA 8505 paragraph 1-2.4 outlines what a
ACTION: Reject. COMM1TrEi~. STATEMENT: The proposed wording is too restrictive to all the retrofits and alterations to which this standard applies. Refer to Proposal 85C-20 (Log #45).
(Log #36) 85C- 7 - (1-1.4): Reject SUBMITr~R: David Haysley, Sr., Beaumont, TX RECOMMENDATION: Add new text to read as follows:
"NFPA 86 should be referred to for such furnaces." SUBSTANTIATION: This would benefit users of the standard. COMMITTEE ACTION: Reject. COMMITrEE STATEMENT: NFPA 86 does not address these furnaces. This would be an incorrect reference.
(Log #172) 85C- 8 - (ld.10 (New)): Accept in Principle SUBMITrE~ Michael Ck Polagye, Factory Mutual Research Corp. RECOMMENDATION: Add new text to read:
1-1.10 Sections 6-8 and 7-8 of this standard addressing Boiler Front Control (Supervised Manual) shall not be applied to new construc- tion. These sections shall apply to existing h6ilers with boiler fxont control and to the alteration of manual boilers. SUBSTANTIATION: The primary reason the Supervised Manual section was written was to apply the important features of the combustion safety requirements of the standard to existing boilers where no such systems had been installed. Supervised Manual with the fuel piping as shown in Figure A-6-5.1.2(c) and A-7-5.1.2(d) is inappropriate for new construction. Following the requirements in the other sections and chapters of the standard permit a wide range
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of automatic/operator actions that fully encompass all intended modes of operation. COMMITrEE ACTION: Accept in Prindple.
Revise 6-8.1 as follows: 6-8.1 General. Section 643 shall not be applied to new construc-
tion. Section 6-8 shall only apply to existing boilers with boiler front control and to the alteration of manual boilers.
Revise 7-8.1 as follows: 7-8.1 General. Section 7-8 shall not be applied to new construc-
tion. Section 7-8 shall only apply to existing boilers with boiler front control and to the alteration of manual boilers. COMI~TrEE STATEMENT: This is more appropriately located in sections 6-8 and 7-8 which is where the subject is addressed.
(Log#48) 85C- 9 - (2-1): Reject SUBMYrrER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Relocate this section (2-1.1 to 2-1.5) to the "Forward". SUBSTANTIATION: The section is general information and does not have any mandatory statements and therefore does not belong in the body of the standard. COMMITrEE ACTION: Reject. COMMITrEE STATEMENT: This information is important and more appropriately belongs in the body of the document. This was deliberately placed at thislocation to provide emphasis.
(Log #49) 85C- 10 - (2-2): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Relocate this section (2-2.1 to 2-2.3) to the "Forward". SUB,.gI'ANTIATION: The section is general information and does not have any mandatory statements and therefore does not belong in the body of the standard. COMMITrEE ACTION: Reject. COMMrFrEE STATEMENT: See Committee Statement on Proposal 85C-9 (Log #48).
(Log #53) 85C- 14- (2-4.3): Reject SUBMITTER: PeterJ. Gore Willse, industrial Risk Insurers RECOMMENDATION: Revise the last sentence to state:
"Any such temporary system shall be reviewed by the purchaser, the engineering consultant, the equipment manufacturer, tm~ the operating company and the authority havin~ Jurisdiction. and agreement shall be reached on its suitability]n advance of start-up." SUBSTANTIATION: The anthorityhavingjurisdiction should also be notified and review any derivations or temporary interlocks that will be installed. COMMITIT..E ACTION: Reject. COMMITrEE STATEMENT: Requiring the authority having
jurisdiction for temporary systems is beyond the intent of the document. Boiler technology is complex compared to other industries, and requires special overview. It is not appropriate for this committee to determine the activities of the authority having jurisdiction.
(Log #54) 8 5 0 15 - (2-5.1, 2-5.2): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Relocate these sections to the Forward. SUBSTANTIATION: There is nothing in this section that is mandatory that is not covered in other sections of this standard. Beside does anybody have a "crystal ball" to see into the future? COMMITrEE ACTION: Reject. COMMITrEE STATEMENT: See Committee Statement on Proposal 85C-9 (Log #48).
(Log #140) 85G 16- (2-6, 4-3, 4-4, 8-3.2): Accept in Principle SUBMITTER: Joe Vavrek, Chicago, IL RECOMMENDATION: Was it intended that the numbering format for these sections not match other headings of similar importance? SUBSTANTIATION: None. COMMITrEEACTION: Acceptin Principle. COMMITYEE STATEMENT: This will be editorially handled by NFPA staff according to the Manual of Style
(Log #50) 85C- 11 - (2-3.4): Reject SUBMITFER: PeterJ. GoreWillse, Industrial Risk Insurers RECOMMENDATION: Relocate this to the Appendix under 2-3.1. SUBSTANTIATION: There is nothing in this section that is mandatory that is not covered in other sections of this standard. COMMITTEE ACTION: Reject. COMMITrEE STATEMENT: This section contains requirements and belongs at its present location.
See Committee Statement on Proposal 85G-9 (Log #48).
(Log #51) 85G- 12 - (2-3.6): Reject SUBMITTER: PeterJ. Gore Wilise, Industrial Risk Insurers RECOMMENDATION: Relocate the first sentence to the Appendix. SUBSTANTIATION: The sentence is informational only, it does not have any mandatory requirements. COMMIITEE ACTION: Reject. COMMITYEE STATEMENT: See Committee Statement on Proposal 85G-9 (Log #48).
(Log #52) 85C- 13 - (2-3.7): Reject SUBMITTER: Peter]. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Relocate the first sentence to the Appendix. SUBSTANTIATION: The sentence is informational only, it does not have any mandatory requirements. COMMITI~E ACTION: Reject. COMMITTEE STATEMENT: See Committee Statement on Proposal 85G-9 (Log #48).
(Log #154) 85C- 17 - (Chapter 3): Accept in Principle SUBMITrER: Bob Lundberg, Los Altos, CA RECOMMENDATION: Delete "(Continuous Igniter)."
Add: Note: A continuous igniter must be a Class 1 igniter.
SUBSTANTIATION: A. A Class 1 igniter need not be operated continuously.
B. By definition of Class 1 a continuous igniter becomes a Class 1 ~OMMI iter"
TrEE ACTION: Accept in Principle. COMMITrEE STATEMENT: See Committee Action on Proposal 85G25 (Log #17).
(Log #168) 85G- 18 - (Chapter 3): Accept in Principle SUBMITTEI~ Bob Kaltenbach, Kansas City, MO RECOMMENDATION: Add new definitions: Atmospheric Vents, Header Vent Lines, Igniter Vent Subsystem.
SUBSTANTIATION: Wording for definition depends on commit- tee action on paragraph 6-3.1.8. There is a need to clarify to permit a more clear interpretation in the area of gas vents. COMMrITEE ACTION: Accept in Principle. COMMITTEE STATEMENT: Refer to the Committee Action on Proposals 85G-72 (Log#166) and 85G-19 (Log#173). These actions meet the intent of the submitter.
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(Log #173) .85C- 19 - (Chapter 3 (New)): Acceptin Principle SUBMITTER= Steven D. Marshall, City of Lakeland, FL Dept. of Electric & Water Utilities RECOMMENDATION: Add a definition for "Header" to read:
Header. A line in which either the fuel flow or pressure is controlled and supplies fuel to any number of branching lines or other headers. SUBSTANTIATION: Refer to 6-3.1.8 and C.O.L letter dated 10/4/93 to Mr. Casey Grant. Confusion has occurred regarding when a line is considered to be a "header" and when it is not. This classification is important because it determines the applicability of 6-3.1.8 regarding independent header vent lines. A system can have multiple headers. Code should be modified to clearly define what a "header" is.
NOTE: Supporting material is available for review at NFPA Headquarters. COMMITI'EE ACTION: Acc~l~t in Principle. Add a definition for "Header to read: Header. A pipe or duct through which fluid is supplied to any
number of branches. COMMITTEE STATEMENT: This definition meets the intent of the submitter and addresses headers for all fuel and air systems.
(Log #45) 85C-20- (3-1 Alteration (New) and Repair (New)): Accept in Principle SUBMITTER= PeterJ. Gore Wilise, Industrial Risk Insurers RECOMMENDATION: Add the following definitions: Alteration. Any change in a system or subsystem from the original
design criteria- Repair. Any work performed, or required, to restore the existing
eqmpment used for the preparation and burning of fuel to its original design criteria. SUBSTANTIATION: None. COMMITTEE ACTION: Accept in Principle. • Add new definitions as follows:
Alteration. A change or modification in a boiler system or subsystem that results in a deviation from the original design specifications or criteria.
Extension. An addition to the boiler system or additional subsystems such as, but not limited to, air quality control.
Repair. A process that returns the boiler system or subsystem to its odginal design specifications or criteria. COMMITTEE STATEMENT: This addresses the concerns of the submitter.
(Log #8) 85C- 21 - (3-1 Alteration/Extension (New)): Accept in Principle SUBMITTER: L. Duffield Rawlings II, Babcock & Wilcox Fossil Power Div. RECOMMENDATION: Add to Chapter 3 Definitions the following:
Alteration/Extension, major A change which requires that a safety-relevant section of the "Logic
System" or "Burner Management System" is alterated. SUBSTANTIATION: The Chapter 1 Introduction states in 1-1.3:
"This standard is applicable to new installations and to major alterations or extenslom of existing equipment for the preparation and burning of fuel contracted for subsequent to June 1, 1991." A definition of major alteration or extension is needed I A system or program is not l~roven until 2 years of numerous, varied applications without any changes with no or only insignificant errors have been detected. COMMITTEE ACTION: Accept in Principle. COMMITTEE STATEMENT: See Committee Action on Proposal 85C-20 (Log #45).
(Log #I 53) 85C- 22 - (3-1 Automatic System (New) and Manual System (New)): Accept in Principle in Part SUBMITTER: Edward G. Milone, Consolidated Edison of NY RECOMMENDATION: Add to definitions: Automatic System. A system in whichproper startup, operation
and normal shutdown are accomplished by an automated burner management control system as defined by this document.
Manual System. A system in which a trained operator has primary responsibility for the proper start-up, operation, and shutdown of a boiler following specific operating instructions for each boiler. A key feature of this system is the provision for safety shutoffvalve
assemblies, in the main and igniter fuel piping supplying the boiler. The system includes interlocks to actuate these assemblies in order to accomplish an emergency shutdown. SUBSTANTIATION: These terms are used/implied throughout publication in text and sketches but are not defined in this section. "Automatic System" is not defined anywhere in this standard. COMMrFI'EEACTION: Accept in Principle in Part.
1. Revise A-6-7.2(m)I title to: "All Systems Except Supervised Manual (Sections 6-5 through 6-7)" 2. Revise A-7-7.2(g)I title to: "All Systems Except Supervised Manual (Sections 7-5 through 7-7)" 3. Revise Figures A-6-5.1.2(a), A-6-5.1.2(d), A-7-5.1.2(c), and
A-7-5.1.2(e) to delete "-automatic" in the figure captions. COMMITI'EE STATEMENT: Manual systems are not recom- mended, and inserting a definition implies their use. Refer to 2-3.3, 2-3.4 and A-7-8(1) (A). A definition of automatic system is not required based on removal
of all references to this term through the standard.
(Log 09) 85C- 23 - (3-1 Burner Management System): Reject SUBMITTER: L. Duffield Rawlings II, Babcock & Wilcox Fossil Power Div. RECOMMENDATION: Revise text to read as follows:
"The Burner Management System includes the following functions stated in this standard; interlock system, fuel trip system, master fuel trip system, master fuel trip relay, flame monitoring and tripping systems, ignition subsystem (main burner subsystem and alarm system.)" SUBSTANTIATION: The alarm system is usually not supplied meeting the NFPA system and not integrated with the Burner Management System. COMMITI~EE ACTION: Reject. COMMITTEE STATEMENT: This change is too all-encompassing since it would include all alarms.
The burner management system does not include all alarms, and alarms can be independent of the burner management systems.
(Log #CP$) 85C. 24 - (3-1 Feed-Forward Signal): Accept SUBMITTER: Technical Committee on Multiple Burner Boilers, RECOMMENDATION: Provide a definition of "Feed-Forward Signal" as follows:
A signal used to anticipate a change in the measured variable." SUBSTANTIATION: This is a useful definition that was inadvert- ently omitted. Refer to Section 5-2.2.2. COMMITI'EE ACTION: Accept.
(Log #17) 85C, 25 - (3-1 Igniter, Class 1): Accept in Principle SUBMITTER: Michael C~ Polagye, Factory Mutual Research Corp. RECOMMENDATION: 1. Delete "(Continuous Igniter)" in the first line.
2. Add to end of definition: "Class 1 i~,w)iters can be operated as continuous, intermittent, or interrupted igniters." SUBSTANTIATION: Class 1 refers to the ability of the igniter to light off any credible air-fuel mixture entering through the burner under any operating condition. Although many Class 1 igniters are operated continuously, this is not a crucial factor in being consid- ered a Class 1 igniter. COMMITrEEACTION: Accept in Principle.
1. Revise the definition of Igniter, Class 1 (Continuous Igniter) as follows:
Igniter, Class 1. An igniter applied to ignite the fuel input through the burner and to support ignition under any burner lightoff or operating conditions. Its location and capacity are such that it will provide sufficient ignition energy (generally in excess of 10 percent of full load burner |nput) at its associated burner to raise any credible combination of burner inputs of both fuel and air above the minimum ignition temperature. Class I igniters shall be permitted to also operate as Class 2 or Class 3 igniters.
2. Revise the definition of Igniter, Class 2 (Intermittent Igniter) as follows:
Igniter, Class 2. An igniter applied to ignite the fuel input through the burner under prescribed lightoff conditions. The range of capacity of such igniters is generally 4 percent to 10 percent of full load burner fuel input.
3. Revise the definition of Igniter, Class $ (Interrupted Igniter) as follows:
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Igniter, Class 3. A small igniter applied particularly to gas and oil burners to ignite the fuel input to the burner under prescribed llghtoff conditions. The capadty of such igniters generally does not exceed 4. percent of the. fulHoad, burner fuel in put.
4. Revise the defitution of Igniter, Class 3 Special (Direct Electric Igniter) and delete its Exception as follows: Igniter, Class 3 Special. A special Class 3 high energy electrical
igniter capable of directly igniting the main burner fuel. 5. Revise 4-2.2.2(d) to read as follows: (d) Ignition Subsystem. 1. The ignition subsystem shall be sized and arranged to ignite the
main burner input within the limitation of the igniter classification. It shall be testedto verify that the igniters furnished meet the requirements of the class specified in the design. Igniters are designated as Class 1, Class 2, or Class 3 as defined in Chapter 3 and as verified by test. Many factors affect the classification of the igniters, including the characteristics of the main fuel, the furnace and the burner design, and the igniter capacity and location relative to the main fuel burner.
2. Class 1 igniters can also be used as Class 2 or Class 3 igniters. Class 2 igniters can also be used as Class 3 igniters.
3. When Class 2 igniters are used the burner shall be operated under controlled conditions to limit the potential for abnormal operation, as well as to limit the charge of fuel to the furnace in the event that ignition does not occur during lightoff. They shall not be used to ignite main fuel under uncontrolled or abnormal condi- tions.
4. When Class 3 igniters are used, the igniter is turned offas a part of the burner llghtoff procedure when the time trial for ignition of the main burner has expired. This practice will ensure that the main flame is not dependent upon tgnition support from the igniter.
5. Class 2 igniters shall not be used to extend the turn down range but can be used to support ignition under low load or adverse operating conditions.
6. Class 3 igniters shall not be used to support ignition nor to extend the burner turn down range.
7. Glass 3 special igniters shall not be used unless supervision of the individual main burner flame is provided. Exception: The Class 3 special igniter shall be permitted to be used without supervision of the individual main burner flame while scavenging the main burner.
8. When Class 1 and Glass 2 igniters are used, the tests described in 6-3.2.2, %3.2.2, and 8-3.3.2 shall also be performed with the ignition subsystem in service to verify that the igniters furnished meet the requirements of the class specified in the design. The resulting extended turndown range shall be available when Class 1 igniters are in service and flame proven.
9. Tests shall be performed to determine transient limits in the ignition air and fuel supplies or the main air and fuel supplies that will not extinguish the igniter flame or reduce the igniter's ability to perform its intended function or adversely affect other burners and igniters in operation. (See also 6-3.2.2, %3.2.2, and 8-3.3.2.)
10. Permanently installed igniters are required. They shall be individually supervised to verify that the requirements of 4-2.2.2(d) 1 and 2 are complied with. This supervision shall include igniter flame and capacity.
11. The ignition equipment shall be located in an appropriate environment with convenient access for maintenance.
12. All igniter safety shutoffvalves shall be located as close as pdractical to igniters so as to minimize the volume of fuel that is
ownstream of the valve in the individual igniter fuel lines or that mayflow by gravity into the furnace after an emergency shutdown or burner shutdown. COMMITTEE STATEMENT: The terms continuous, intermittent, and interrupted will no longer be used in this standard to refer to igniters. The definitions and related section on Igniters have been editorially revised to address the concerns of the submitter.
(Log #18) 85C- 26 - (3.1 Igniter, Class 2): Accept in Principle in Part $UBMITTER: Michael C. Polagye, Factory Mutual Research Corp. RECOMM]gNDATION: 1. Delete "(Intermittent Igniter)" in the first line.
2. Replace the last sentence of definition with: ~A Class 2 Igniter may be operated as an intermittent or inter-
rupted igniter. When used as an intermittent igniter, a flame detector dedicated to sensingonly the main burner flame associated with that igniter, as well as af lame detector for sensing the igniter flame, is required." SUBSTANTIATION: A Class 2 igniter can only reliably ignite any credible fuel input to its burner under prescribed light-off condi- tions. During light-offa scanner is required to detect igniter flame at the point it will ignite main fuel. This critical point may or may
not be the same during normal burner operation and flame detection at this point may not prove main burner flame. A separate detector that does not see igniter flame is required for this purpose. COMMITrFAE ACTION: Accept in Principle in Part.
1. Accept. 2. Reject.
COMMITrFAg STATEMENT: The reason for rejecting the submitter's item 2 is that Class 2 is adequately defined and does not require further clarification. The terms continuous, intermittent, and interrupted will no longer be used in this standard to refer to igniters.
(Log #19) 85G 27- (3-1 Igniter, Continuous (New)): Accept in Principle $UBMITTER= Michael C. Polagye, Factory Mutual Research Corp. RECOMMENDATION: Add new text to read as follows:
Igniter, Continuous. An igniter that must be proved on at the end of the igniter trial for ignition period and must remain in service during the entire operating cycle of its burner. Continuous igniters must be Class 1 igniters. Burners with continuous Class 1 Igniters do not require independent main burner flame supervision, provided igniter flame supervision is within main burner flame envelope. SUBSTANTIATION: Existing definition of "Igniter, Class 1 (Continuous Igniter)" causes confusion. A continuous igniter must be Class 1, but a Class 1 size igniter does not have to be operated continuously.
If igniter is Class 1 it will reliably ignite any credible fuel input to the burner under all operating conditions. Therefore, if flame is detected by igniter detector within main burner flame envelope, main fuel is/will be ignite(d). COMMITrFAg ACTION: Accept in Principle. COMMITrEE STATEMENT: See Committee Action on Proposal 85C-25 (Log #17).
(Log #20) 85C- 28 - (3-1 Igniter, Intermittent (New)): Accept in Principle SUBMITrRR: Michael C. Polagye, Factory Mutual Research Corp. RECOMMi~NDATION: Add new text to read as follows:
Igniter, Intermittent. An igniter that must be proved on at the end of the igniter trial for ignition period and that may remain on at the end of the main burner trial for ignition period or be placed in service at any time during the normal operation of its burner. A Class 1 or Class 2 size igniter may be used as an intermittent igniter. SUBSTANTIATION: "Intermittent Igniter" is not clearly defined in the standard. COMMITI'RE ACTION: Accept in Principle. COMMITTEE STATEMENT: See Committee Action on Proposal 85G25 (Log #17).
(Log #CP9) 85C- 29 - (3.1 Purge Rate, Coal and Purge Rate, Gas/Oil): Accept $UBMITTER: Technical Committee on Multiple Burner BoRers, RECOMMENDATION: 1. Revise the definitions as follows:
Purge Rate, Coal. A constant flow of not less than 25 percent nor more than 40 percent of the full load mass airflow.
Purge Rate, Gas/Oil. A constant flow of not less than 25 percent of the full load mass airflow.
2. Revise "volumetric airflow" to "airflow" in 2-7.1 (c), 6-5.1.5, Table 6-5.2.5.2(a) item (b), 7-5.1.5, 8-5.1.5, and Table 8-5.2.5.2(a) item (b).
3. Revise "volumetric flow" to "airflow" in Table %5.2.5.2(a) item (b). SUBSTANTIATION: This addresses concerns that were originally raised by NFPA 8504-A95 Public Comments.
Based on these revised definitions, it was determined that there is no need to place within NFPA 85C a definition for Ambient Temperature. COMMITrEE ACTION: Accept.
(Log #55) 85C- 30 - (4-1.1.1): Acceptin Part SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Remove the words: "design" from the first sentence, "plus" from (a), and "minus" from (b). SUBSTANTIATION: Editorial. COMMITTEE ACTION: Accept in Part.
Accept the proposed changes except for removing the word "design."
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COMMITTEE STATEMENT: Removing the word "design" is not editorial.
(Log #34) 85C- 31 - (4.1.1.1(a) and (b)): Accept in Principle SUBMITI~R: Lou DeCuir, Texas Air Control Board RECOMMENDATION: Revise text to read as follows:
(a) The test block capability of the forced draft fan at ambient temperature or at least plus (+) 35 in. of water (+ 8.7 kPa), which- ever is greater, and
(b) The test block capability of the induced draft fan at ambient temperature, but at least more negative than minus (-) 35 in. of water (- 8.7 kPa). SUBSTANTIATION: The wording is ambiguous and doesn't make sense. The ~ design pressures should a t l ~ t exceed a certain amount. To saya ~ value should not exceed a certain amount is confusing. Since 4-1.1.1 is addressing minimum structural furnac e strength, any minimum design pressure in excess of (+ 35 in. W.C. would result in an additional safety margin. COMMITTEE ACTION: Accept in Principle. Revise text to: 4-1.1.1" The furnace shall be capable of withstanding a transient
design pressure without permanent deformation due to yield or buckling of any support member. This minimum design pressure (see section 5-1) shall be: (a) The test block cal?ability of the forced draft fan at ambient
temperature or (+) 35 inches of water (+8.7 kPa), whichever is less, and
(b) The test block capability of the induced draft fan at ambient temperature or (-) 35 inches of water (-8.7 kPa), whichever is less negative. Add a new appendix section as follows: A-4.1.1.1 For example, if the test block capability of the forced
draft fan at ambient temperature is +25 inches of water (+6.2 kPa), then the minimum positive design pressure would be +25 inches of water (+6.2 kPa).
If the test block capability of the induced draft fan at ambient temperature is -15 inches of water (-3.7 kPa), then the minimum negative design pressure would be -15 inches of water (-3.7 kPa).
If the test block capability of the forced draft fan at ambient temperature is +40 inches of water (+9.9 kPa), then the minimum positive design pressure would be +35 inches of water (+8.7 kPa).
If the test block capability of the induced draft fan at ambient temperature is -40 inches of water (-9.9 kPa), then the minimum negative design pressure would be -35 inches of water (-8.7 kPa). COMMITTEE STATEMENT: The submitter's interpretation of this section is incorrect. The revised wording reduces the chance for misinterpretation and thereby meets the needs of the submitter.
(Log #56) 85C- 32 - (4-2.2.2(d) 1): Reject SUBMITTER: PeterJ. Gore Wiltse, Industrial Risk Insurers RECOMMENDATION: 1. Revise the third sentence to state:
"Igniters are designated by use as Class 1, Class 2, or Class 3 as defined in Chapter 3 and shall be as verified by test."
2. Make the last sentence a "Note" or Appendix item. SUBSTANTIATION: None. COMMITI'EE ACTION: Reject. COMMITI'EE STATEMENT: See Committee Action on Proposal 85C-25 (Log #17). The current wording is sufficient.
(Log #57) 850 33 - (4.2.2.2(d)$): Accept SUBMITTER: PeterJ. GoreWillse, Industrial Risk Insurers RECOMMENDATION: Rewrite the first sentence to state:
"Igniters shall be permanently installed." SUBSTANTIATION: To conform to the Manual of Style. COMMITTEE ACTION: Accept.
(Log #58) 85C- 34- (4-2.2.2(e)1): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Add the following to the end of the paragraph:
"The ducts shall be permitted to be rectangular or square."
SUBSTANTIATION: With the present wording, NFPA 91 Exhaust Systems for Air Conveying of Materials will dictate the exhaust ducts be round. COMMITTEE ACTION: Reject. COMMITrEE STATEMENT: This is not relevant to the document and NFPA 91 is not referenced.
(Log #59) 85C-35 - (4.3, 4-3.1): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Relocate the sentence in 4-3 and the first sentence of 4-3.1 to the Appendix, relocate the second sentence of 4- 3.1 to 4-3, and renumber 4-3.2 as 4.3.1. SUBSTANTIATION: These two sentences are informational and are not mandatory, therefore, should not be in the body of the standard. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: See Committee Statement on Proposal 85C-9 (Log #48).
(Log #37) 85C- 36 - (4.3.2.1): Accept in Principle SUBMITTER: David Haysley, St., Beaumont, TX RECOMMENDATION: Revise text to read as follows:
43.2.1 should cover Hardwired and Microprocessor Logic Systems. 4-3.2.1 (a) through (g) should be under 4-3.2.1.1 Microprocessor
Systems. Add: 4-3.2.1.2 Hardwire Systems: (a) same as 4.3.2.1(a); (b) same
as 4.3-2.1 (d); (c) relay coil failure (d) relay contact failure-fail-on, "fail-off", (e) timer failure. SUBSTANTIATION: The concept of accomplishing the FMEA is excellent. It should however be done on all systems not just microprocessor based systems. This paragraph supports the process hazards analysis. (PHA) requirements of OSHA's new 29CFR1910.119. COMMITTEE ACTION: Accept in Principle. Add the following new items to 4.3.2.1 (h) relay coil failure; (i) relay contact failure (fail-on, or fail-off); and (j) timer failure. Add semicolons after items (a) through (g).
COMMITTEE STATEMENT: This clarifies this section and meets the intent of the submitter.
(Log #60) 85C- 37 - (4-3.2.1): Accept in Principle SUBMITTKR: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Replace the word "recognize" with "review" in the first sentence. SUBSTANTIATION: How do you enforce recognition? Having them review the modes will be better. COMMITrEE ACTION: Accept in Principle. Substitute "evaluate for "recognize."
COMMITI'EE STATEMENT: This wording more accurately clarifies the intent of the paragraph.
(Log #170) 85C- 38- (4.3.2.2(d) Note (New)): Reject SUBMITI~R: Bill Bass, Forney International, Inc. RECOMMENDATION: Add a new Note to read:
NOTE: Many programmable control systems allow on-line logic modifications. In this case, it is the responsibility of the authorized programmer(s) to ensure that the specific equipment in question is not in operation. SUBSTANTIATION: Unless all logic resides in ROM, PROM, or EPROM, few, if any, programmable systems programming capabili- ties can be interlocked with equipment status. If the system logic resides in RAM, EEPROM, or EAPROM, then the logic can likely be modified on-line and is therefore a human function to ensure off- line status. COMMI'['rEE ACTION: Reject. COMMITrEE STATEMENT: As a minimum standard, the present text clearly addresses the intent of the paragraph and does not require further clarification.
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(Log #38) 85C- 39- (4-3.2.2(h)): Reject SUBMITTER: David Haysley, Sr., Beaumont, TX RECOMMENDATION: Add text to read as follows:
" . . . actuate the master fuel trip relay systemf SUBSTANTIATION: Do not infer a single relay can be used for the master trip in that it would be "a single source of failure" to prevent failure to a safe condition. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: A single relay may be used for the master fuel trip relay, hut it cannot be the only means of tripping fuel on a mandatory master fuel trip. Also refer to the definition of master fuel trip relay.
(Log #31) 85C-40- (4-3.2.3): Accept in Principle SUBMITrER: William Cunningham, United Engineers & Construc- tors
I RECOMMENDATION: In Section 4-3.2.3 add the words: "The logic system shall be limited to one boiler only."
SUBSTANTIATION: Please offer clarification to this section of the code, may the logic for more than one boiler be permitted within the same burner management system? COMMIT[EE ACTION: Accept in Principle. Accept the submitter's wording as a newparagraph 4-3.2.3.3.
COMMITrEE STATEMENT: Editorial. Refer to the Committee Action on Proposal 85C-41 (Log #39).
(Log #30) 85C- 41 - (4-3.2.3): Accept in Principle SUBMITTER: David Haysley, Sr., Beaumont, TX RECOMMENDATION: Add more detail to define the expression "shall not be combined with any other logic system." Is complete independence required i.e., can the Burner Management Logic be in the Dist. Control System? Is a separate DC_~ or PLC required? Can communications exist between the senarate s~tems. SUBSTANTIATION: Major conflicts are ~urrenfiygoing on within users as this standard is to what degree of independence is needed. COMMITrEEACTION: Accept in Principle.
Revise 4-3.2.3 as follows: 4-3.2.3 Requirement for Independence. 4-3.2.3.1 The logic system performing the safety functions for
burner management shall not be combined with any other logic system.
4-3.2.3.2 These burner management safety functions shall include, but not be limited to, proper purge interlocks and timing, manda- tory safety shutdowns, trial timing for ignition, and flame monitor- ing. 4-3.2.3.3 The logic system shall he limited to one boiler only. 4-3.2.3.4 The burner management system shall be provided with
independent logic, independent input/output systems, and independent power supplies, and shall be functionally and physically separate from other logic systems (i.e., boiler control system).
4-3.2.3.5 The same hardware type shall be permitted to be used for Burner Management Systems as is used for other logic systems.
4-3.2.3.6 Data highway communications between the Burner Management System and other systems shall be permitted. Signals that initiate mandatory master fuel trips shall be hardwired. COMMITTEE STATEMENT: The changes to 4-3.2.3 address the concerns of the submitter and clarify this section.
(Log #61) 85C- 42 - (4-4.2.1): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Revise the second sentence to state:
"Field tests shall be reformed a.c ~,.,luL~ to establish optimum
SUBSTANTIATION: Making this a mandatory requirement. COMMrFrEE ACTION: Reject. COMMITrEE STATEMENT: The current wording is sufficient.
(Log #62) 85C- 43 - (4-4.2.4): Reject SUBMITTER: PeterJ. Gore Wilise, Industrial Risk Insurers RECOMMENDATION: Relocate this section to the Appendix under 4-4.2.1. SUBSTANTIATION: There is nothing mandatory in the section, only informational. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: See Committee Statement on Proposal 85C-9 (Log #48).
(Log #141) 85C- 44- (4-4.2.4): Accept in Principle SUBMITTER: Joe Vavrek, Chicago, IL RECOMMENDATION: Appendix D is referenced here but is not a
g art of this edition of 85C. UBSTANTIATION: None.
COMMITrEE ACTION: Accept in Principle. Chang~e parenthetical reference to "see A-6-5.2.1.2(c)."
COMMITrEE STATEMENT: Editorial.
(Log #164) 85G- 45 - (4-5.1.3 (New)): Reject SUBMITTER: William E. Cunningham, United Engineers & Constructors, Inc. RECOMMENDATION: Add new text as follows:
4-5.1.3 Where two or more boilers are connected to a common stack, each connection shall be equipped with a damper system. All boiler outlet dampers shall be equipped with accessible operating and locking devices. This equipment shall be compatible with the combustion control system of the boiler. Interlock shall be provided to prevent firing against a closed damper. SUBSTANTIATION: NFPA 8501 paragraph 4-4.6.2 this information should also apply to 85C. COMMITTEE ACTION: R~ect. COMMITrEE STATEMENT: This requires a change in philosophy to include allpoints requiring isolation. The submitter's recommen- dation is too design specific.
(Log #63) 85G- 46 - (4-6): Accept SUBMITTEI?,; PeterJ. Gore Willse, Industrial Risk Insurers RECOMMF.aNDATION: Revise to state: d]vicPOWer o_ supply (elec c or pneumatic) to all co. ol and
SUBSTANTIATION: Indicates which devices we want to have failure-free power. COMMITrEE ACTION: Accept.
(Log #157) 85C- 47 - (4.6(a) (New)): Accept in Principle SUBMITTER: William Axtman, Manassas, VA RECOMMENDATION: Add new text as follows:
4-6(a) No automatic resetting interlock shall be installed in the power supply that directly connects to the main or ignition fuel ~alve(s). SUBSTANTIATION: It has recently come to my attention that some automatic resetting interlocks have been installed in the power supply to the main fuel valves. When such interlocks trip the fuel valves close and the fuel supply is interrupted but a safety shutdown is not initiated until the flame detector senses the loss of flame which action may take several seconds to respond, ff the interlock resets in the meantime fuel can be admitted to the furnace after a flame interru, ption . This action, can take place . without igniters, bein g energized. The fuel hghts offthe hot brick work with a resultant furnace explosion. COMMITTEE ACTION: Accept in Principle.
Insert new text to read as follows: 4-$.2.4 Logic sequences or devices intended to cause a safety
shutdown, once initiated, shall cause a burner or master fuel trip, as applicable, and shall require an operator action prior to resuming operation of the affected burner(s). No logic sequence or device shall be permitted that allows momentary closing and subsequent inadvertent reopening of main or ignition fuel valves. COMMITTEE STATEMENT: This new paragraph addresses the concerns of the submitter and more appropriately belongs in the section on Burner Management System Logic.
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NFPA 85C-- A95 ROP
(Log #161) 85C, 48 - (4-8 (New)): Reject SUBMITTER: William E. Cunningham,Jr., Raytheon Engineers & Constructors, Inc. RECOMMENDATION: Add new text as follows:
4-8 Electrical Equipment. 4-8.1 All electrical equipment and wiring shall conform to NFPA
70, National Electrical Code. 4-8.2 Locations where completely dusttight pulverized fuel, gas or
fuel oil systems are installed in compliance with this standard shall not be considered a hazardous location for electrical equipment as defined in NFPA 70, National Electrical Code.
4-8.3 Special fuels or applications may require components for hazardous location and shall be reviewed during the design of the system. SUBSTANTIATION: We address the relationship of NFPA 70 hazardous locations for coal firing equipment in NFPA 8503. Natural gas and fuel oil applications of the same NFPA 70 standard are not addressed. The number of boilers which have explosion proof electrical enclosures are indeed few. The inclusion of this paragraph will offer a clear view of the position of NFPA on this I s s u e .
COMMITrEE ACTION: Reject. COMMITTEE STATEMENT: This issue is already covered in NFPA 497A and is beyond the scope of NFPA 85C.
(Log #64) 85C- 49 - (5-1): Reject SUBMITTER= PeterJ. GoreW'fllse, Industrial Risk Insurers RECOMMENDATION: Revise to state:
"Considerations shall be ¢dven to one or both of the followin~ methods to minimize the ~mk of necrative furnace draft. " SUBSTANTIATION: Make this a r~andatory statement. COMMITTEE ACTION: Reject. COMMITI?EE STATEMENT: The existing wording properly conveys the intent of this chapter.
(Log #65) 85C- 50 - (5-2.1): Reject SUBMITI'ER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Replace "desired" with "manufacturer's recommended." SUBSTANTIATION: Indicates which set point should be used. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: Other criteria exists besides the manufacturers recommendations.
(Log #CP2) 85G 51 - (5-2.2.2(a)): Accept SUBMITTER: Technical Committee on Multiple Burner Boilers, RECOMMENDATION: Revise as follows:
"(a) Three furnace pressure transmitters (B) in an auctioneered median-select system, each on a. . .~ SUBSTANTIATION: This more clearly indicates the need for three furnace pressure transmitters. COMMITTEE ACTION: Accept.
2. Replace "must" with "shall." SUBSTANTIATION: Make the parts mandatory. COMMITTEE ACTION: Reject. COMMI'ITEE STATEMENT: This section is mandatory byvirtue of the opening statement. The use of the term must is appropriate in this particular situation.
(Log #68) 85C- 54- (5-3.1.1): Accept in Principle in Part SUBMITrER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: 1. Relocate the first sentence to the Appendix.
2. Revise the rest to state: "The proper fan start-up and shutdown procedures ~ as defined
by the manufacturers, engineering consultants, and operating companies. T',,..o~ t" G ~ J , . ~'~, shall be integrated wi th . . . " SUBSTANTIATION: Cleans this up and makes it mandatory. COMMITrEE ACTION: Accept in Principle in Part.
Reject the submitter's first recommendation. Accept the submitters second change with the following change:
"The proper fan start-up and shutdown procedures as defined by the manufacturers, engineering consultants, and operating companies shall be coordinated wi th . . . " COMMIT1"EE STATEMENT: For item 1, see Committee Statement on Proposal 85C-9 (Log #48).
For item 2, the submitter's wording has been accepted with minor editorial corrections.
(Log #69) 85C- 55 - (5-3.1.2): Accept in Prindple SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Part (a)2: Delete Note.
Part (c): Replace "discouraged" with "prohibited." SUBSTANTIATION: Part (a) 2 deals with single fans.
Part (c) makes this mandatory. COMMITTEE ACTION: Accept in Principle.
Move the note after (a)2 to (a)l. COMMITrEE STATEMENT: The note more appropriately belongs after (a)l. The use of the word "prohibited" is too restrictive based on the complexities of this technology.
(Log #46) 85C- 56 - (5-4.1.1 (New)): Reject SUBMITI'ER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Add new text to read:
5-4.1.1 Interlocks shall not be manually bypassed at any time during normal operation.
Exception: Interlocks on the low water cutouts shall be permitted to be bypassed for blowdown purposes only. This bypass shall be of a deadman type switch or device which is held during blowdown. SUI~TANTIATION: Editorial. COMMITI'EE ACTION: Reject. COMMITTEE STATEMENT: Refer to Sections 6-6.2.3(h), 7- 6.2.3(h), and 8-6.2.3(h) which adequately covers defeating interlocks during normal operation and maintenance.
(Log #66) 85C- 52 - (5-2.3.1): Accept in Prindple SUBMITTER: PeterJ. Gore Wilise, Industrial Risk Insurers RECOMMENDATION: Revise to state:
" . . . power supply (electric or pneumatic) to all devices..." SUBSTANTIATION: Indicates which devices we want to have failure-free power. COMMITTEE ACTION: Accept in Principle.
Delete 5-2.3.1 and renumber accordingly. COMMITTEE STATEMENT: This section is redundant with 4-6 and is not necessary.
85C- 53 - (5-2.3.2): Reject (Log #67) SUBMITTER: Peterl . Gore Willse, Industrial Risk Insurers RECOMMENDATION: 1. Replace "must" with "shall" on the first [ line, and make the second and third sentence a "Note" or Appendix I item.
(Log #70) 85C- 57 - (5-4.2.2): Accept in Part SUBMITrE~ PeterJ. GoreW'dlsc, Industrial Risk Insurers RECOMMENDATION: I. (a)1 and (b)l Replace the last sentence with: "The airflow shall not be increased by deliberate manual or
automatic control actions." 2. In the NOTE: Under (b) l, replace "maybe necessary" with
"shall be permitted." (b)2 "... a master fuel t r i p ~ all induced draft fans shall be
if... short time delay L, . . ~ c . ~ y ~hall be t~ermi~ed to allow..."
3. (c) and (d): 1. Delete "Provide" 2. Revise to state: "Damper(s) shall be closed on..." 4. Revise to state: "A master fuel t r ip shall be init iated on loss..."
SUBSTANTIATION: Editorial clarification. COMMITTEE ACTION: Accept in Part. Accept the submitter's changes except: 1. Revisions to 5-4.2.2(b)1 Note. 2. Deletion of"Provide" in 5-4.2.2(c) 1 and 5-4.2.2(d) 1.
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N F P A 8 5 C - - A 9 5 R O P
3. Also revise 5-4.2.2(c)2 and 5-4.2.2(d)2 to: "Associated damper(s) shall be closed on loss of..."
COMMITrEE STATEMENT: The note is properly worded in accordance with the NFPA Manual of Style a n d d o e s not require fur ther modification.
The wording of 5-4.2.2(c) 1 and 5-4.2.2(d) 1 is adequate and does not require claange.
The wording of 5-4.2.2(c)2 and 5-4.2.2(d)2 has been further clarified.
( Log #1 ) 85C- 58 - (5-4.2.2(c) (3)): Accept in Principle Note: This proposal appeared as comment 85G-64 which was held
for fur ther study f rom the Annual 91 TCD, which was on proposal 85C-1. SUBMITTER: Charles A. Moore, Stone & Webster Engineering RECOMMENDATION: Revise text to read as follows:
"Where an interlock system is provided to start, stop and trip induced draft and forced draft fans in pairs, the associated induced draft fan shall be t r ipped on loss of an individual forced draft fan (unless FD fan trip was due to high furnace pressure), and the dampers associated with both fans shall be closed unless they are the last fans in service." SUBSTANTIATION: This revision would allow the ID fans to continue running, if you have a majorposifive furnace pressure upset that trip the FD fans in a coupledsystem. This is predicated on revising the high furnace trip as suggested in another submittal. As an example, the uni t is near full load and it suffers a major tube
rupture. The normal Mb"r occurs on high furnace pressure, but the combination for the FD fan flow plus escaping steam is too much for the ID fans causingthe furnace to go very positive and tr ipping the FD fans. This wil lkeep the ID fans running to help evacuate the steam from the furnace setting.
NOTE: We wish to have clarified that the " . . . unless they are the last fans in service. "phrase in this paragraph, (and similar para- graphs), refers to damper action and not. fan. operation. COMMITTEE ACTION: Accept in Prmople .
Revise 5-4.2.2(c) 3 and 5-4.2.2(d)3 as follows: 5-4.2.2(c)3 Where an interlock system is provided to start, stop,
and trip induced draft and forced draft fans in pairs, the associated induced draft fan is t r ipped on loss of an individual forced draft fan and the dampers associated with both fans shall be closed, provided they were not the last fans in service, f f theywere the last fans in service, the induced draft fan shall remain in controlled operation and the dampers associated with that forced draft fan shal l remaln
o~_~.,½.2(d) 3 ~ o n Where an interlock system is provided to start, stop, and trip induced draft and forced draft fans in pairs, the associated forced draft fan shall be t r ipped on loss of an individual induced draft fans. Provided they are not tile last fans in service, the dampers associated with both fans shall be closed. If they are the last fans in service, the dampers associated with both fans shall remain open. COMMITrEE STATEMENT: Based on fur ther review and Committee deliberations, changes to 5-4.2.2(c) 3 and 5-4.2.2(d)3 properly address the concerns of the submitter and clarify the intent of these sections.
(Log #21) 85C- 59 - (5-5.2(b)): Accept in Principle SUBMITrER: Michael C. Polagye, Factory Mutual Research Corp. RECOMMENDATION: 1. Change to read:
"Pluggage of the sensing tap or other maloperation of redundant transmitters within the furnace pressure control system."
2. Add: NOTE: Due to the small changes in furnace pressure at the control
point during normal operation, a deviation alarm among the hxnsmitters may not be a reliable indication of a problem. Other means, such as a constant furnace pressure being recorded over a limited period of time at any one sensor may be a better indication. SUBSTANTIATION: Consider a 3 tap auctioneering system during normal operation, two taps could plug. Since draft is well controlled during steady state and gradual load changes, nei ther tap caused a deviation alarm with respect to the operating tap. ff third tap plugs there is "a big problem. But if . . . . . . third tap is working and pressure deviation occurs the auct loneermg system wall throw out the operating tapl COMMITTEE ACTION: Accept in Principle.
Revise 5-5.2(b) to: "Redundant transmitter malfunctions within the furnace pressure
control system."
COMMITrEE STATEMENT: This clarifies the intent of this paragraph and adequately addresses the concerns of the submitter.
(Log #158) 85G- 60 - (Chapter 6, Chapter 7, and Chapter 8): Reject SUBMITTER: Leo Donovan, Factory Mutual Eng. & Research RECOMMENDATION: State that safety shutoffvalves should be proved closed. Also, a symbol for a proof-of-closure type of safety shutoff valve should be used in the figures. SUBSTANTIATION: The following sections state that safety shutoff valves should be closed before ignition can be attempted, but they do not state that they need to be proved:
Figure 6-3.1.1 6-5.2.1.1(0 6-6.3.1.3 7-5.2.1.1(0 %6.3.1.1 Figure 7-6.3.1.1 8-5.2.1.1(t) 8-6.3.1.1 Figure 8-6.3.1.1
COMMITrEE ACTION: Reject. COMMrITEE STATEMENT: The existing text adequately conveys the in tended wording and the submitter 's recommendat ion does not provide any fur ther clarification. The interlocks and alarms identified in this standard indicate the requirement for proving valve position.
(Log #71 ) 85C- 61 - (6-2, 7-2, 8-2): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Relocate this section to the Appendix. SUBSTANTIATION: This is all informational and not mandatory requirements. COMMITrEE ACTION: Reject. COMMITTEE STATEMENT: See Committee Statement on Proposal 85G-9 (Log #48).
(Log #72) 85C- 62 - (6-3.1.1, 7-3.1.1): Accept SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Revise the second sentence to state:
"This shall include coordination of..." SUBSTANTIATION: Makes these requirements mandatory. COMMITTEE ACTION: Accept.
(Log #73) 85C- 63- (6-3.1.2): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Revise to state:
" . . . supply constant fuel pressure regulator(s), . Uo~,-.'.',y ;LZ. ,-~, bc ac~..;~t,l,~Lcd by providing full relieving capacity, vented to a safe location. ; ;q . . . . . r , ll ,~ l~d , ,g ~av~Z ) io ,,c.:. ~,oh21,:~ or a high
~uBP ressure s,~,ol'l b~ ~., v,;Acd " STANTIATION: Mandates one or the other.
COMMITrEE ACTION: Reject. COMMITrEE STATEMENT: Present wording is sufficient and addresses the concerns of the submitter. Further clarification is not required.
(Log #74) 85C- 64- (6-3.1.3, 7-3.1.2): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Delete the word "Convenient." SUBSTANTIATION: What is "Convenient?" COMMITrEE ACTION: Reject. COMMITTEE STATEMENT: Deleting o f t h e w o r d "convenient" puts no requirements on how access is to be provided. If access is not convenient, then maintenance may become impractical.
131
NFPA 85C-- A95 ROP
85G- 65 - (6-$.1.5): Reject (Log #75) SUBMITrER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Make the last sentence a NOTE. SUBSTANTIATION: This is informational material. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: See Committee Action on Proposal 85C-9 (Log #48).
(Log #'22) 85C- 66 - (6-$.1.6 (New)): Reject SUBMITTER= Michael C. Polagye, Factory Mutual Research Corp. RECOMMENDATION: Revise text to read as follows:
6-$.1.6 Positive means to prevent leakage of gas into a furnace shall be provided. Each burner fuel gas supply line shall be equipped as indicated in the following paragraphs for the applicable input classification or any greater input classification.
6-3.1.6.1 For boilers where the total fuel heat input does not exceed 250 million Btu/hr , two shutoffvalves with proof of closure and valve seal over-travel shall be provided at each burner.
6-3.1.6.2 For boilers where the total fuel heat input is greater than 250 million Btu/hr , two shutoffvalves with proof of closure shall be provided at each burner. Provisions shall also be included to vent the piping upstream of the last shutoffvalve.
6-3.1.6.3 For igniters with heat inputs not exceeding 5 million Btu/ hr, two shutoff valves shall be provided in series or one shutoffvalve with valve seal over-travel and proof of closure shall be provided in any fuel line to the igniter.
6-3.1.6.4 For igniters with heat inputs exceeding 5 million Btu /hr but not exceeding 12.5 million Btu/hr , two safety shutoffvalves in series with valve seal over-travel and proof of closure shall be provided in any fuel line to the igniter.
6-$.1.6.5 For igniters with heat inputs exceeding 12.5 million Btu/ hr, two safety shutoffvalves in series with proof of closure shall be provided in each fuel line to the igniter. Provisions shall also be included to vent the piping upstream of the last shutoffvalve. SUBSTANTIATION: This proposal is aimed at harmonizing the various operating philosophies currently practiced by industry and addressedin ASME CSD-1.
It recognizes that for smaller multi-burner industrial and utility boilers i tmay not be feasible to safelyvent fuel gas. This can be the case in urban or congested industrial park locations where adjacent construction or aesthetic building code limitations (such as maximum stack height) preclude safe venting.
The new sub-paragrapbs related to igniters provide consistency with GSD-1 and also reflect the difficulty of providing safe venting for some smaller boilers. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: Based on extensive Committee deliberations, it is unclear that a problem exists on this issue. It is believed that the existing wording is appropriate and adequate.
(Log #76) 85C- 67 - (6-$.1.6 (New)): Accept in Principle SUBMITI"ER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Add the following:
The vent shall be sized according to Table 6-$.1.6.
Table 6-3.1.6 Vent Line Sizes
_<1 112 314 2 1 2 112 to S 1 114 3112 1 112 4to5 2 5 112 to 6 2 112 6 1/2 to 7 1/2 3 8 3 1/2 >8 15% of the cross sectional area of the
pipe.
SUBSTANTIATION: We require the vents but do not give the vent line sizes. COMMITTEE ACTION: Accept in Principle. COMMITTEE STATEMENT: Guidelines for vent line sizes have been added by a new A-6-3.1.6. See Committee Action on Proposal 85C-181 (Log #175).
(Log #CP8) 85C- 68 - (6-$.1.7): Accept S U B M I T r F ~ Technical Committee on ~Multiple Burner Boilers, RECOMMENDATION: Revise text as follows:
"Periodic tightness tests of the main safety shutoff valves, individual burner safety shutoffvalves and associated vent valves shall be performed. Provisions shall be made in the gas piping to allow for permanent and ready means for making easy, accurate leak tests and subsequent repairs." SUBSTANTIATION: More clearly define the requirement for leak testing. COMMITTEE ACTION: Accept.
(Log #25) 85C- 69 - (6-$.1.7 Note (New)): Reject SUBMITI'ER: Michael C. Polagye, Factory Mutual Research Corp. RECOMMENDATION: Add a Note to read as follows:
NOTE: A manual isolation valve downstream of the last burner shutoff valve should not be provided. Such valves may be placed in an intermediate position and cause flame stability problems that will not be detected by safety limit switches. The last shutoffvalve can be tested by providing pressure through the leak test connection downstream of the upstream shutoff valve. SUBSTANTIATION: At last committee meeting for 8504 (85H) and the last main committee meeting, serious concerns were expressed about locating a manual valve downstream of the last burner shutoff valve. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: The proposed wording does not provide satisfactory clarification. There is no reason against recommending this valve downstream.
(Log #1 $9) 85C- 70 - (6-3.1.7, 7-3.1.11): Accept in Principle SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Make a Appendix item on these showing an example of leak test procedures. SUBSTANTIATION: We need better guidance. COMMITTEE ACTION: Accept in Principle. COMMI'FrFA~ STATEMENT: See Committee Action on Proposal 85G-90 (Log #35).
(Log #77) 85C- 71 - (6-$.1.8): Accept in Principle SUBMITI'ER: PeterJ. Gore Wilise, Industrial Risk Insurers RECOMMENDATION: Add the following before the last sentence:
"The vent lines from the individual burners shall be permitted to be manifolded together. The vent lines from the individual igniters shall bepermi t t ed tu be manifolded together. The cross-sectional area of the manifolded line shall not be less than the largest vent line plus 50 percent of the cross-sectlonal area of the additional vent lines." SUBSTANTIATION: Systems are being installed with manifolded lines but there isn't an)t guidance as to how to size the manifold. COMMITITAgACTION: Accept in Principle. COMMITrEE STATEMENT: Guidelines for manifolded vent lines have been added by a newA-6-$.l.8. See Committee Action on Proposal 85C-181 (Log #175).
(Log #166) 85C- 72 - (6-3.1.8): Accept in Principle SLIBMITrER: Bob Kaltenbach, Kansas City, MO RECOMMENDATION: Clarify the intent, requirement for independence and scope of the 2nd sentence (starting Header vent l ines . . . ) and Srd sentence (starting The igniter ven t . . . ) . SUBSTANTIATION: Rewording c a n n o t be offered since the committee's intent is not dear. COMMITrEE ACTION: Accept in Principle.
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NFPA 8 5 C - - A95 ROP
Revise 6-3.1.8 as follows: 6-3.1.8 The discharge f rom atmospheric vents shall be located so
that there is nopossibili ty of the discharged gas being drawn into the air intake, ventilating system, or windows of the boiler room or adjacent buildings and shall be extended sufficiently above the boiler and adjacent structures so that gaseous discharge does not present a fire hazard.
Insert a new 6-3.1.9 and renumber subsequent paragraphs accordingly:
6-3.1.9 Manifolding of Vents. Manifolding of all vents shall be permitted.
Exception 1: Burner vents shall not be manifolded with igniter vents.
Exception 2: Header vents shall only be manifolded with other header vents.
Exception 3: Vents of headers being served from different pressure reducing stations shall not be manifolded.
Exception 4: Vent systems of different boilers shall not be manifolded.
Exception 5: Vents of systems operating at different pressures shall not be manifolded.
Exception 6: Vents of systems using different fuel sources shall no t be manifolded. COMMITTEE STATEMENT: These changes address the submitter 's concerns.
(Log #176) 85C- 73 - (6-3.1.9): Accept SUBMITTER: Joseph IL Buchanan, ITT Engineered Valves RECOMMENDATION: Delete:
NFPA 54. National Fuel Gas Code. and SUBSTANTIATION: Scope for NFPA 54 specifically excludes fuel gas piping i npow e r plants, refineries, etc. COMMITrEEACTION: Accept.
(Log #78) 85C- 74 - (6-3.2.1, 7-3.2.1): Accept S U B M I ~ Peter J[. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Replace "may" in the last sentence with "shall be permit ted to." SUBSTANTIATION: Eliminates the permissiveness. COMMITTEE ACTION: Accept.
(Log #79) 85C- 75 - (6-3.2.2, 7-3.2.2, 8-3.2.2): Reject SUBMITTER: Peter] . Gore WUlse, Industrial Risk Insurers RECOMMENDATION: Make the third sentence a NOTE. SUBSTANTIATION: This is informational and not mandatory. COMMITrEE ACTION: Reject. COMMITrEE STATEMENT: See Committee Action on Proposal 85C-9 (Log #48).
(Log #24) 85G- 76 - (6-4.1.1 (New)): Accept in Principle SUBMITrER: Michael C. Polagye, Factory Mutual Research Corp. RECOMMENDATION: Add new text to read as follows:
6-4.1.1 At least one flame detectors shall be provided for each burner to detect the burner flame or igniter flame when a Glass 1 size igniter is provided. The flame detector shall be positioned to detect igniter flame at a point that is within the main burner flame envelope. SUBSTANTIATION: Provides clear requi rement for flame detection when a Glass I size igniter is provided. COMMITrEE ACTION: Accept in Principle.
Insert a new paragraph as follows: 6-4.1.1 When Class 1 igniters are provided, the main burner flame
shall be proven either by the flame scanner or by the igniter being proven. At least one flame detector shall be provided for each burner to detect the burner flame or igniter flame when a Class 1 igniter is provided.
Insert a new paragraph as follows: 7-4.1.1 When Class I igniters are provided, the main burner flame
shall be proven either by the flame scanner or by the igniter being proven. At least one flame detector shall be provided for each burner to detect the burner flame or igniter flame when a Glass 1 igniter is provided.
C O M M I T r F ~ STATEMENT: This section has been reworded to clarify its intent.
(Log #25) 85G- 77 - (6-4.1.2 (New)): Accept in Principle SUBMITTEPa Michael C. Polagye, Factory Mutual Research. Corp. RECOMMENDATION: Add new text to read as follows:
6-4.1.2 Burners with Glass 2 size igniters in intermittent service shall have at least two flame detectors. One detector shall be
~ ositioned to detect main burner flame and shall not detect igniter ame. The second detector shall be positioned to detect igniter
flame at the po in t required to ignite main burner fuel during
~ rescribed lightoff conditions. UBSTANTIATION: Provides clear flame detection requirements
for burners using Glass 2 igniters in intermittent service. COMMI'I ' rEE ACTION: Accept in Principle.
Insert a new paragraph as follows: 6-4.1.2 Burners with Class 2 igniters shall have at least two flame
detectors. One detector shall be posit ioned to detect main burner flame and shall not detect igniter flame. The second detector shall be posit ioned to detect igniter flame during prescribed lightoff conditions.
Insert a new paragraph as follows: 7-4.1.2 Burners with Class 2 igniters shall have at least two flame
detectors. One detector shall be posit ioned to detect main burner flame and shall not detect igniter flame. The second detector shall be posit ioned to detect igniter flame during prescribed lightoff conditions. COMMITrEE STATEMENT: This meets the intent of the submitter and fur ther clarifies this section. See Committee Action on Proposal 85C-7fi (Log #24).
(Log #26) 85G- 78 - (6-4.1.3 (New)): Accept in Principle SUBMITTEPa Michael C. Polagye, Factory Mutual Research Corp. RECOMMENDATION: Add new text to read as follows:
6-4.1.3 Burners with interrupted igniters shall have at least one flame detector. The detector shall be posit ioned to detect igniter flame during the Igniter and burner trial for ignition periods and the main burner flame during after the main burner trial for TIrind has expired
ON: Provides clear flame detector requirements for burner equipped with interrupted igniters. COMMITrElg ACTION: Accept in Principle.
Insert a new paragraph as follows: 6-4.1.3 Burners with Class 3 igniters shall have at least one flame
detector. The detector shall be posit ioned to detect igniter flame. It shall also detect main burner flame after the igniter is removed from service at the end of the main burner trial for ignition.
Insert a new paragraph as follows: 7-4.1.3 Burners with Glass 3 igniters shall have at least one flame
detector. The detector shall be posit ioned to detect igniter flame. It shall also detect main burner flame after the igniter is removed from service at the end of the main burner trial for ignition. C O M M I T r g ~ STATEMENT: This meets the intent of the submitter and fur ther clarifies this section. See Gommittee Action on Proposal 85G76 (Log #24).
(Log #80) 85C- 79 - (6-4.2, 7-4.2): Accept in Principle ° SUBMITTER: PeterJ. GoreWillse, Industrial Risk Insurers RECOMMENDATION: Revise to state:
" . . . in the furnace or loss of flame to simaificant number of burners
~ ,~. dr-'- %o0 c, f2--.;;c to the extent that . . 7" UI~TANTIATION: What is partial loss of flame?
C O M M I T r ~ ACTION: Accept in Principle. In paragraph 6.4.2, add to the end "(See 6-6.3.1.1(d)6)". In Table 6-5.2.5.2(a), item (e), add to the end "(See 6-
6.3.1.1(d)6)". In paragraph 6-6.3.1.1 (d) 6, delete in the first sentence: "in the
furnace, with some burners still operating ~. In paragraph 7-4.2, add to the end "(See 7-6.3.1.1 (e)9)". In Table 7-5.2.5.2(a), item (e), add to the end "(See 7-6.3.1.1(e)9)". In paragraph 7-6.3.1.1 (e)9, delete in the first sentence: "in the
furnace, with some burners still operating". In Table 8-5.2.5.2(a), item (f), add to the end "(See 8-6.3.1.I (d)7)". In paragraph 8-6.3.1.1 (d)7, delete in the first sentence: "in the
furnace, with some burners still operating".
NFPA 85C-- A95 ROP
COMMITTEE STATEMENT: The phrase "partial loss of flame" is a defined term. The other committee actions meet the intent of the submitter.
(Log #81) 85C- 80 - (6-4.3, 7-4.3, 8-4.2): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Relocate the first sentence to the Appendix. SUBSTANTIATION: Informational material. COMMITrEE ACTION: Reject. COMMITTEE STATEMENT: See Committee Statement on Proposal 85G-9 (Log #48).
(Log #82) 85C-81 - (6-4.4, 7-4.4, 8-4.3): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Replace "is required" with "shall be performed" in the first sentence, "may" with "shall be permitted to" in the second sentence, and "are not intended to" with "shall not" in the last sentence. SUBSTANTIATION: Makes these requirements mandatory. COMMITrEE ACTION: Reject. COMMITrEE STATEMENT: The present wording is appropriate and properly conveys the intent.
(Log #83) 85C-82- (6-5, 7-5): Accept in Principle SUBMITrER: PeterJ. Gore Willse, industrial Risk Insurers RECOMMENDATION: Add the following:
"6-5 . . . for Automatic Systems. For supervised manual systems, see Section 6-8".
"7-5 ... for Automatic Systems. For supervised manual systems, see Section 7-8". SUBSTANTIATION: Present wording indicates these requirements also apply to supervised manual systems. COMMITTEE ACTION: Accept in Principle.
Revise 6-5 and 7-5 as follows: 6-5 Sequence of Operations. (For supervised manual systems, see
Section 6-8). 7-5 Sequence of Operations. (For supervised manual systems, see
Section 7-8). COMMITTEE STATEMENT: Automatic systems are not limited to sections 6-5 and 7-5 only. The committee action meets the intent of the submitter.
(Log #86) 85C- 85 - (6-5.1.5, 7-5.1.5, 8-5.1.5): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Place all except the first sentence in the Appendix. SUBSTANTIATION: Informational material. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: See Committee Statement on Proposal 85C-9 (Log 048).
(Log #160) 85C- 86 - (6-5.1.5.1(c)): Reject SUBMITTER: DouglasJ. Shaffer, Energy Division of Zurn Indus- tries RECOMMENDATION: Take exception to:
"Components containing sources of ignition energy shall be purged for the greater of either: (1) a period of not less than five minutes, or (2) five volume changes of that component prior to being placed in service."
Exception to be as stated in NFPA 8501, Single Burner Boiler Operation, 1992 edition, Section 6-2.4.1 (h)(i):
"Purge air flow shall reach no less than 70 percent of the air flow required at maximum continuous capacity of the unit. The purge shall be sufficient for at least eight air changes." SUBSTANTIATION: With stricter emission requirements being applied to boilers, new technologies are evolving that have changed the design of burners/boilers. Multiple burners are used on boilers, where technically a single burner is sufficient for heat input, but emission requirements dictate multiple burner application. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: NFPA 8501 does not apply to multiple burner boilers and 6-2.4.1 (h) and (i) in NFPA 8501 addresses different issues than 6-5.1.5.1 (c) in NFPA 85C. Existing text is appropriate and correct.
(Log #87) 85C- 87 - (6-5.1.5.2, 7-5.1.5.2, 8-5.1.5.2): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Place the sentence starting "For example.. ." as a NOTE. SUBSTANTIATION: Informational material. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: This more appropriately belongs in the existing paragraph.
See Committee Statement on Proposal 85C-9 (Log #48).
(Log #84) 85C- 83 - (6-5.1.2, 7-5.1.2, 8-5.1.2): Reject SUBMITTER: Peter.[. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Replace "are" w i th "shall be" a n d a d d the following "and acceptable to the authority having jurisdiction" to the last sentence. SUBSTANTIATION: If there is any derivation from the typical fuel supply system, this should be approved by the authority having jurisdiction. COMMITrEE ACTION: Reject. COMMITTEE STATEMENT: This is an improper use of the word "shall". , See Committee Statement on Proposal 85G-14 (Log #53).
(Log #85) 85C- 84 - (6-5.1.3, 7-5.1.3, 8-5.1.3): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Place the second, fourth, fifth, and sixth sentences in the Appendix. Replace "It shall be so" in the second sentence with "Continuous airflow shall be." SUBSTANTIATION: These sentences are informational material. COMMITTEE ACTION: Reject. COMMITrEE STATEMENT: See Committee Statement on Proposal 85C-9 (Log #48).
(Log #88) 85C- 88 - (6-5.1.6, 7-5.1.6, 8-5.1.6): Accept SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Revise to state:
"Modification to the mode of oneration, resulting from imnroner water, steam, and flue gas temoe'ratures in the economizers anc~ suoerheaters shall be n~ade or;Iv after it has been determined by oderatinff exnerience. " SUBSTAIqTI~ATION: Cleans it up. COMMITTEE ACTION: Accept.
(Log #27) 85C- 89- (6-5.2.1.2(d)): Reject SUBMITTER: Michael C. Polagye, Factory Mutual Research Corp. RECOMMENDATION: Change the first sentence to "Charging valve shall be opened. . . " SUBSTANTIATION: All gas systems should have charging valve (for boilers covered in this standai-d). Without this feature there is no proof that serious leaks are not occurring. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: It is not the Committee's intent to require a charging valve. Such a valve is not mandatory. See Committee Action on Proposal 85C-90 (Log #35).
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NFPA 85C-- A95 ROP
(Log #35) 85C-90- (6-5.2.1.2(d)): Accept in Prindple SUBMITI'ER: Gordon L.Johuson, Bechtel Corp. ,RECOMMENDATION: Add a second paragraph to read as follows:
' If a charging valve is not furnished the main safety shutoffvalve shall be opened by the operator long enough to vent and charge the header. Failure to maintain pressure during the purge period shall prevent completing a successful purge." - SUBSTANTIATION: The present wording is ineffectual as it does not require a successful leak test be performed to complete a purge if a charging valve is not furnished. This change will make the procedure in paragraph 6-5.2.1.2(d) mandatory and satisfy para- grapb 6-3.1.7. I believe this was the intent of the committee. COMMITFEE ACTION: Accept in Principle.
1. Revise to read as follows: 6-5.2.1.2(d)* An operational leak test of the fuel header piping
system shall be performed in accordance with established proce- dures while maintaining purge rate airflow. Successful completion of the leak test shall be part of a completed unit purge.
2. Also add A-6-5.2.1.2(d) as follows: A-6-5.2.1.2(d) ff~charging valve (required serf-closing) on the
main gas supply is furnished, this should be opened to bypass the main safety sbutoffvalve; otherwise open the main safety shutoff valve. Open main fuel control valve as required. Vent the burner header until it is filled with gas. Close burner header atmospheric vent valve. Leave charging or main safety shutoffvaive open to establish a nominal pressure on the burner header. Then close the charging or main safetyshutoffvalve. It may be concluded that the safety shutoffvalves do not leak if this pressure remains within defined limits. COMMITTEE STATEMENT: This addresses the concerns of the submitter and darifies the intent of this paragraph.
(Log #CP1) 85C- 91 - (6-5.2.1.2(d)): Accept SUBMITTER: Technical Committee on Multiple Burner Boilers, RECOMMENDATION: Change the parenthetical at the end of the paragraph to:
"(See Figure A-6-5.1.2(d))" SUBSTANTIATION: Editorial. This is the correct reference. COMMITTEE ACTION: Accept.
(Log #165) 85C- 92 - (6-5.2.1.2(d)): Accept in Principle SUBMITTER: William E. Cunningham, United Engineers & Consuauctors, Inc. RECOMMENDATION: Add the words:
"Pressure testing of the header shall (or may) be required before the startup of any boiler." SUBSTANTIATION: ff a charging valve is not provided, then a pressure test of the header will not be required. This is a common qNFpUeStion, which should be very clear, one way or the other within
A 85C. COMMITrEEACTION: Accept in Principle. COMMITTEE STATEMENT: Refer to action in Proposal 85C-90 (Log #35).
(Log #'2) 85C- 93 - (6-5.2.1.2(g) CAUTION): Reject Note: This proposal appeared as comment 85C-83 which was held
for further study from the Annual 91 TCD, which was on proposal 85G1. SUBMYrTER: Susumu Sato, Mitsubishi Heavy Industries, Ltd.,
a an {~I~OMM~NDATION: Revise the first sentence of the paragraph to read:
"6-5.2.1.2(g) CAUTION: Total furnace air flow including gas recirculation shall not be reduced below purge rate and air flow shall be at least that which is required for complete combustion in the furnace." SUBSTANTIATION: In modern Japanese utility boilers, air flow is minimized and gas recirculation is introduced during start-up period before SCR (Selective Catalytic NOx Reductor) is put into operation to minimize NOx emission. At start up condition, gas recirculation flow contains high 02
concentration similar to air. Therefore, gas recirculation flow should be included in the total furnace flow rate which is used to evaluate the velocity through the furnace. COMMITTEE ACTION: Reject.
COMMIIWEE STATEMENT: The proposed change potentially permits a larger percentage of recirculation of unburned combus- tibles. Also see Committee Action on Proposal 85C-128 (Log #152).
(Log #167) 85C- 94- (6-5.2.1.2(h) and (i)): Accept in Principle SUBMITTER: Bob Kahenbach, Kansas City, MO RECOMMENDATION: Modify 2nd sentence of 6-5.2.1.2(h) to read:
"The burner headers shall be vented to fill them with g~as and shall be closed prior to opening any individual burner valves.
Modify 2nd sentence of 6-5.2.1.2(i) to read: "The igniter headers shall be vented to fill them with gas and shall
be closed prior to opening any individual igniter valves." SUBSTANTIATION: The practice of venting to control flow is not required. Adequate and reliable equipment is available to provide adequate conditions fro light-off. Purposelyventing a gas fuel could be hazardous and is an environmental concern. COMMITrEE ACTION: Accept in Principle.
Insert a caution after 6-5.2.1.2(h) and (i) as follows: CAUTION: The period of time needed to vent for control of
header pressure after header charging shall be evaluated and minimized. COMMITrEE STATEMENT: The existing wording of NFPA 85C allows for indefinite venting. The submitter's concerns are more appropriately addressed as a caution. This statement is more complete and meets the submitter's intent.
(Log #89) 8 5 C - 9 5 - (6-5.2.3.3): Accept in Principle SUBbflTTER: PeterJ. Gore Wilise, Industrial Risk Insurers RECOMMENDATION: Revise the paragraph to state:
"The reverse procedure of that used during start-up shall be followed for normal shutdown. As load is reduced, a sequential shut down of the burners shall be accomplished by the closing of the individual burner safety shutoffvaives, opening of the vent valves, and leaving the registers on these burners in firing position." SUIKtJTANTIATION: Present wording does not conform to the Manual of Style. COMMITTEE ACTION: Accept in Principle.
Revise the paragraph to read as follows: "The reverse procedure of that used during start-up shall be
followed for normal shutdown. As load is reduced, a sequential shut down of the burners shall be accomplished by the closing of the individual burner safety shutoffvalves and opening the vent valves." COMMITTEE STATEMENT: Further changes were made to correct and clarify the intent of the paragraph, and to remove conflict with the preceding paragraph. These changes are consistent with the intent of the submitter.
(Log #9O) 85C- 96 - (6-5.2.3.4): Accept in Principle $UBMITTER~ PeterJ. Gore W'dise, Industrial Risk Insurers RECOMMENDATION: Add the following:
"Venting procedures shall follow the following order." SUBSTANTIATION: To conform to the Manual of Style. COMMITTEE ACTION: Accept in Principle.
Revise 6-5.2.3.4 through 6-5.2.3.6 as follows: 6-5.2.3.4 The last burner or group of burners shall be taken out of
service by tripping the main safety shutoffvalve. 6-5.2.3.5 All atmospheric vent valves shall be opened to minimize
the possibility of gas leaking into the boiler-furnace enclosure. 6-5.2.3.6 When all burners and igniters have been removed from
service, the purge rate airflow shall be verified and a unit purge shall be performed.
6-5.2.3.7 After completion of the unit purge, closing the burner air registers and shutting down of the Forced Draft and Induced Draft fans are optional. However, consideration shall be given to maintain- ing airflow through the unit to prevent accumulation of combustible
es Leakage of main or igniter fuel into the furnace or windbox gas . shall be preventecL COMMI'ITEE STATEMENT: This provides further editorial clarification. 6-5.2.3.4(b) is not necessary and has been deleted. Refer to the Committee Action on Proposal 85G-97 (Log #91).
135
NFPA 8 5 C - - A95 ROP
(Log #91) 85C- 97 - (6-5.2.3.5, %5.2.3.6): Accept in Principle SUBMITTER: PeterJ. Gore Wiilse, Industrial Risk Insurers RECOMMENDATION: Revise to state:
"When all burners and igniters have been removed from service, a unit purge shall beperformed." SUBSTANTIATION: To conform to the Manual of Style. COMMITrEE ACTION: Accept in Principle.
Revise text as follows: "When all burners and igniters have been removed from service,
the purge rate airflow shall be verified and a unit purge shall be performed." COMMITTEE STATEMENT: This more appropriately clarifies the intent of this paragraph and maintains the use of the word verify. Note that paragraph 6-5.2.5.5 has been renumbered to 6-5.2.3.6 in the Committee Action on Proposal 85C-96 (Log #90).
SUBSTANTIATION: Present wording does not conform to the Manual of Style. COMMITTEE ACTION: Accept in Principle. Revise to read as follows: 6-5.2.5.3 Procedure for Purging after an Emergency Shutdown.
Fans that are operating after the master fuel trip shall be continued in service. The airflow shall not be increased by deliberate manual or automatic control action. If the airflow is above purge rate, it shall be permitted to be gradually decreased to this value for a post- firing purge. If the airflow is below purge rate at the time of the trip, it shall be continued at the existing rate for five minutes and then gradually increased to purge rate airflow and held at this value for a 1o~ t-nnng tos t - f i r in unit purge.ur e. ~OMMIT1"EE STATEMENT: Further changes have been made to this paragraph for clarity. The concerns of the submitter have been addressed.
(Log #155) 85C-98- (6-5.2.4.1, 7-5.2.4.1, 8-5.2.4.1): Accept in Principle SUBMITTER: Bob Lundberg, Los Altos, CA RECOMMENDATION: Delete "or after it has been bottled up under pressure." SUBSTANTIATION: NFPA recommendations are to maintain air flow through the unit. "Bottled up is inferior" and if the term is used, NFPA should not be its sponsor. There have been numerous explosions starting up after this condition, stokers, gas, oil, coal, fired multi burner units and fluidized bed units. COMMITrEE ACTION: Accept in Principle.
Revise text as follows: 6-5.2.4.1 When restarting a hot unit, the requirements of 6-
5.2.1.1 (f) through 6-5.2.1.1 (m) for a cold start shall be satisfied. 7-5.2.4.1 When restarting a hot unit, the requirements of%
5.2.1.1 (f) through 7-5.2.1.1 (n) for a cold start shall be satisfied. 8-5.2.4.1 When restarting a hot unit, the requirements of 8-
5.2.1.1 (0 through 8-5.2.1.1 (k) for a cold start shall be satisfied. COMMITrEE STATEMENT: This more appropriately clarifies the intent of these paragraphs and addresses the concerns of the submitter.
(Log #92) 85C- 99 - (6-5.2.4.2, 7-5.2.4.2, 8-5.2.4.2): Accept SUBMI'FI'ER: PeterJ. Gore Wiilse, Industrial Risk Insurers RECOMMENDATION: Revise to state:
6-5.2.4.2 The starting sequence in 6-5.2.1.2 shall be followed. %5.2.4.2 The starting sequence in 7-5.2.1.2 shall be followed. 8-5.2.4.2 The starting sequence in 8-5.2.1,2(a) through (r) shall be
followed. SUBSTANTIATION: To conform to the Manual of Style. COMMITrEE ACTION: Accept.
(Log #93) 85C~ 100 - (6-5.2.5.1, %5.2.5.1, 8-5.2.5.1): Accept S U B M I T ~ I ~ PeterJ. GoreWUlse, Industrial Risk Insurers RECOMMENDATION: Revise as follows:
"An emergency shutdown shall initiate a master fuel trip." SLrBSTANTIATION: To conform to the Manual of Style. COMMITTEE ACTION: Accept.
(Log #142) 85C, 101 - (6-5.2.5.2): Reject S U B ~ Joe Vawek, Chicago, IL RECOMMENDATION: Were electrostatic precipitators intention- Sai~%ANClUded in this paragraph for gas-fired units?
TIATION: None. COMMITI?EE ACTION: Reject. COMMITI'EE STATEMENT: Information was included in this section because of the existence of multiple fuel units.
(Log #94) 85G- 102 - (6-5.2.5.3, 7-5.2.5.3, 8-5.2.5.3): Accept in Principle SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Revise to state:
"...shall be continued in service. The airflow shall n o t b e increased by manual or automatic control action. If the airflow is above purge rate, it shall be permitted to be gradually decreased to this value for a post-firing purge."
(Log #95) 85C- 103- (6-5.2.5.4, 7-5.2.5.5, 8-5.2.5.4): Accept in Principle SUBMII~rER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Revise the paragraph to state:
"When the emergency trip has been caused by loss of draft fans, or draft fans have also tripped, all dampers in the air and flue gas passages of the unit shall be slowly opened to the wide open position in order to create as much natural draft as possible to ventilate the unit. Opening fan ... fan coast-down. This condition shall be maintained for at least 15 minutes. At the end of the 15 minutes, the fan(s) shall be started in accordance with Chapter 5, "Furnace Implosion Protection." The airflow shall be gradually increased to the purge rate and a post-firing unit purge completed." $LrI~TANTIATION: Present wording does not conform to the Manual of Style. COMMITrEEACTION: Accept in Principle.
Revise paragraphs 6-5.2.5.4, %~.2.5.5 and 8-5.2.5.4 to read as follows:
"When the emergency trip has been caused by loss of draft fans, or draft fans have also tripped, all dampers in the air and flue gas passages of the unit shall be slowly opened to the wide open position m order to create as much natural draft as possible to ventilate the unit. Opening fan dampers shall be timed or controlled to avoid excessive positive or negative furnace pressure transients during fan coast-down. This condition shall be maintained for at least 15 minutes. At the end of this period, the fan(s) shall be started in accordance with Chapter 5, Furnace Implosion Protection. The airflow shall be gradually increased to the purge rate and a post- firing unit purge completed."
Add a new 6-5.2.5.5 to read as follows: "6-5.2.5.5 Action following purge after an emergency shutdown
(see 6-5.2.5.3 and 6-5.2.5.4) shall be in accordance with the following:
(a) Shut down the unit in accordance with 6-5.2.3.6; or (b) f f the purge following an emergency shutdown is performed at
purge rate and the conditions identified in 6-5.2.1.1 (f) through (m) and 6-5.2.1.2(d) and (e) are satisfied, a relight in accordance with 6-5.2.1.2(g) through (u) is permitted. Add a new %5.2.5.6 to read as follows and renumber subsequent
paragraphs accordingly:. "%5.2.5.6 Action following purge after an emergency shutdown
(see 7-5.2.5.4 and 7-5.2.5.5) shall be in accordance with the following:
(a) Shut down the unit in accordance with 7-5.2.3.7, 7-5.2.3.8 and 7-5.2.5.6; or
(b) If the purge following an emergency shutdown is performed at purge rate and the conditions identified in %5.2.1.1 (f) through (n) and 7-5.2.1.2(d) and (f) are satisfied, a relight in accordance with %5.2.1.2(g) through (t) is permitted. Add a new 8-5.2.5.5 to read as follows and renumber subsequent
paragraphs accordingly: "8-5.2.5.5 Action following purge after an emergency shutdown
(see 8-5.2.5.3 and 8-5.2.5.4) shall be in accordance with the following:
(a) Shutdown the un i t in accordance with 8-5.2.3.5; or (b) If the purge following an emergency shutdown is performed at
purge rate and the conditions identified in 8-5.2.1.1 (f) through (k) and 8-5.2.1.2(d), (f) and (g) are satisfied, a relight in accordance with 8-5.2.1.2(h) through (u) is permitted. COMMITI"EE STATEMENT: This meets the intent of the submitter while retaining the meaning of the existing text. The new para- graphs have been added to provide increased clarity on permissible actions after completing a purge following an emergency shutdown.
136
NFPA 85C-- A95 ROP
(Log #28) 85G- 104- (6-5.3.2): Reject SUBMrI~I'ER: Michael C. Polagye, Factory Mutual Research Corp. RECOMMENDATION: Revise the last sentence to read:
"If fuel flow cannot be reduced, a Master Fuel Trip shall be initiated." SUBSTANTIATION: Normal control is equipped with features to preclude introducing more fuel than can be burned with the existing air supply. IF this is not the case, the unit is out of control and should be tripped. Unburned combustibles can be explosively ignited by glowing material in the boiler enclosure or air heater or by a spark in downstream equipment such as a precipitator. Existing practice is not safe. COMMITI'EE ACTION: Reject. COMMI'ITEE STATEMENT: A trip of the fuel allows a sudden increase in the air/fuel ratio which may create a larger hazard. Refer to Committee Action on Propo.~al 85C-105 (Log #96).
(Log #96) 85C- 105 - (6-5.3.2, 7-5.3.2, 8-5.4.2): Accept in Principle SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Revise the paragraph to state:
"If an air deficiency develops while flame is maintained at the burners, the fuel shall be reduced until proper air/fuel ratio has been restored, if fuel flow cannot be reduced, the airflow shall be slowly increased until proper air/fuel ratio has been restored." SUBSTANTIATION: Present wording does not conform to the Manual of Style. COMMITrEE ACTION: Accept in Principle. Revise these paragraphs to read as follows: "If an air deficiency develops while flame is maintained at the
burners, the fuel shall be reduced until proper air/fuel ratio has been restored, or if fuel flow cannot be reduced, the airflow shall be slowly increased until proper air/fuel ratio has been restored.
NOTE: A trip of the fuel during a fuel rich condition when flame is being maintained will result in a sudden increase in the air/fuel ratio which can create a greater hazard." COMMITrEE STATEMENT: Further editorial clarification has been made.
(Log #41) 85C- 109 - (6-6.1.1): Accept in Principle SUBMITrER: David Haysley, Sr., Beaumont, TX
I ECOMMENDATION: Add at the end of paragraph: "The interlock system must comply with section 4-3 of this
standard." SUBSTANTIATION: Some users go directly to the "fuel" type sections of the standard and miss the importance of section 4-3. COMMITI'EE ACTION: Accept in Principle.
I Accept the submitter's wording, but change must to shall. COMMITTEE STATEMENT: Editorial.
(Log #42) 85C- 110 - (6-6.2.3(h)): Reject SUBMITTER: David Haysley, Sr., Beaumont, TX RECOMMENDATION: Change: "annu ciated if practical" to "alarmed." SUBSTANTIATION: Such bypassing should ~ be alarmed. Somehow, someway. COMMITTEE ACTION: Reject. COMMI'VrEE STATEMENT: The implementation of the proposed change is not practical and has yet to be realistically resolved.
(Log #43) 85C- 111 - (6-6.2.3(h)): Reject SUBMITTER: David Haysley, St., Beaumont, TX RECOMMENDATION: Add: specific acceptable "other means." Suggest one such means: "specific operating instructions to manually monitor the interlock condition having by-passed "defeated" state is an acceptable substitute." SUBSTANTIATION: Users don't understand this paragraph and/ or are confused as to what constitutes an "acceptable substitute." COMMITI'EE ACTION: Reject. COMM]'ITEE STATEMENT: The submitter's recommendation is .t°° desi .gnps ecific and is. more appropriate, as supporting, appendix lnformauon. The subrmtter has not provided specdic recommended appendix wording, and is encouraged to submit such specific wording by public comment.
(Log #97) 85C- 106 - (6-5.4.4, 7-5.4.4): Accept in Principle SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Revise as follows:
"When operating at low capacity, ,,.d.~t,d;~ a the burner fuel pressure ,hall be maintained above minimum by reducing the number of burners in service." SUBSTANTIATION: Cleans this up and makes it mandatory. COMMITrEE ACTION: Accept in Principle. Revise these paragraphs to read as follows: "When operating at low capacity, the burner fuel pressure shall be
maintained above minimum by reducing the number of burners in service as necessary." COMMITI'EE STATEMENT: This provides further editorial clarification.
(Log #143) 85C- 107- (6-5.4.5): Reject SUBMITI'ER: Joe Vavrek, Chicago, IL RECOMMENDATION: Were soothlowers intentinally included here for gas-fired units? SUBSTANTIATION: None. COMMITTEE ACTION: Reject. COMMI'VrEE STATEMENT: Information was included in this section because of the existence of multiple fuel units.
(Log #98) 85G- 108 - (6-5.4.6): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Replace "6-2(g)" with "NFPA 54". SUBSTANTIATION: Editorial. COMMITI'EE ACTION: Reject. COMMr[TEE STATEMENT: The current reference provides further useful information and should remain. Furthermore, the scope of NFPA 54 is not directly applicable for this situation.
(Log #29) 85C- 112- (6-6.2.30) Exception No. 1 and No. 2 (New)): Accept in Principle SUBMITTER: Michael C. Polagye, Factory Mutual Research Corp. RECOMMENDATION: 1. Add "No. 1" after "Exception."
2. Add an "Exception No. 2 to read: "An auctioneered drum level signal or furnace draft signal may be
used for control and interlock purposes." SUBSTANTIATION: These are two cases where the most reliable signal is the signal used for normal control. The standard should not force independence when it results in less reliability of the safety system. COMMITrEE ACTION: Accept in Principle. Make the following changes to 6-6.2.30), 7-6.2.3(i), and 8-6.2.30): 1. Add "No. 1" after "Exception." 2. Add an Exception No. 2 to read: Exception No. 2: Air flow measurement and auctioneered furnace
draft signals from the boiler control system shall be permitted to be used for a master fuel trip if the following conditions are met:
(a) These interlocks are hardwired into burner management system;
(b) Tripping set points shall be protected from unauthorized changes; and
(c) Any single component failure of these sensing elements and circuits shall not prevent a mandatory master fuel trip. COMMITrEE STATEMENT: The paragraph referenced is mandatory master fuel trips. Drum level "trips" are not mandatory master fuel trips. This would be confusing to include in this exception. The sharing of signals is permitted as addressed in Exception No. 2. Changes to Chapter 7 and Chapter 8 are for consistency between
chapters.
137
N F P A 8 5 C - - A95 R O P
(Log #10) 85G 113 - (6-6.2.3(k) (New)): Reject SUBMITTER: C.D. Alvey, Lutherville, MD RECOMMENDATION: Add a new section (k) tO read as follows:
(k) Redundant master fuel trip relays shall be provided. Trip coil monitoring devices shall be included to assure integrity of tripping functions. SUBSTANTIATION: Current 85C-1991 requires only one MFT Relay. Very recently, a 600 MW coal fired boiler was severely damaged when MFI" logic called for tripping but unmonitored trip coil had failed so that M}~r did not occur. Fuel was ultimately tripped when individual pulverizers tripped from flame failure, after F.D. Fans had tripped from high furnace pressure after tubes ruptured. If this proposal is adopted, editorial corrections to change master fuel trip relay to "relays" are also required in 6-6.3.1.1(d)1, 2, 3, 4, 5, 6, and 8 and 6.6.3.1.2 and 006.3.1.3. COMMr[TEE ACTION: Reject. C O ~ STATEMENT: NFPA 85C requires as stated in 4- 3.2.2 (g), any single component failure ... shall not prevent a mandatory master fuel trip."
In the above occurrence, the system was not designed properly since this ~ failure did prevent a master fuel trip.
(Log #1 1) 85C- 114 - (Figure 006.3.1.1): Accept in Principle in Part SuBMrrlT, R: C.D. Alvey, Lutherviile, MD RECOMMENDATION: Add an arrow to line connecting "Master fuel trip logic ~ box and "Master fuel trip relay(s)" box. Also, delete parentheses around "s and make simply "relays" if previous
~ roposal is adopted (6-6.2.3(k)). UBSTANTIATION: Editorial and to conform with proposal for
redundant relays. COMMITTEE ACTION:, Accept in Prindpie in Part.
1. Accept the submitter s first change of adding an arrow to Figure 006.3.1.1. Also make this change to Figures 7-6.3.1.1 and 8-6.3.1.1, and remove the second line between the "Master Fuel trip logic" box and "Master fuel trip relay(s)" box for Figure 8-6.3.1.1.
2. Reject. COMMITTEE STATEMENT: 1. The additional changes for item 1 are editorial.
2. See Proposal 85C-113 (Log#10).
(Log #99) 85C- 115 - (6.6.$.1.1, 7-6.3.1.1): Reject SUBMITTER: PeterJ. Gore W'fllse, Industrial Risk Insurers RECOMMENDATION: Make this all NOTES to the Figures. SUBSTANTIATION: This explains Figure 6-6.3.1.1 and does not contain mandatory material. COMMITIT~E ACTION: Reject_ COMMITIT~ STATEMENT: The figure is referenced in 6-6.3.1. The text does describe required logic and does contain mandatory material.
(Log #100) 85C- 116 - (Figure 6-6.3.1.1, Figure 7-6.3.1.1): Reject SUBMITTER: PeterJ. Gore Wdlse, Industrial Risk Insurers RECOMMENDATION: Add a new block for:
"Individual burner safety shutoff valves failed to close fully." SUBSTANTIATION: Since we do not require a manual shut off on the individual burners, if the safety shut offvalve fails to dose, we could get raw fuel without the requires air into the boiler. COMMITI?EE ACTION: Reject. COMMITTEE STATEMENT: The requirement for the alarmin~ of valves not being fully closed when required is already addressed m 6- 7.2(m). It is too restrictive for this to be a mandatory trip.
(Log #40) 85C- 117- (6-6.3.1.3, 0-6.3.1.7, and 6-6.3.1.8 (New)): Reject SUBMITIT~ David Haysley, Sr., Beaumont, TX RECOMMENDATION: Add details on allowable time for ignition try, and number of ignition tries, prior to the need for a re-purge of system. SUBSTANTIATION: Extensive ignition failure after the permissive could cause excessive gas to be present in boiler and a new purge cycle should be accomplished. COMMITrEE ACTION: Reject.
COMMITrEE STATEMENT: The submitter's concerns are adequately addressed by paragraph 6-5.2.1.2(k) that requires maintaining the purge rate.
(Log #I01) 85C- 118 - (006.3.1.3, 7-6.3.1.4, 8-6.3.1.3): Reject SUBMITTER: PeterJ. Gore W'f l l se , Industrial Risk Insurers RECOMMENDATION: Make the second sentence a NOTE. SUBSTANTIATION: This is informational. COMMITIT~ ACTION: Reject. COMMITTEE STATEMENT: See Committee Action on Proposal 85C-9 (Log #48).
(Log #102) 85C- 119 - (6-7.1.2, 7-7.1.2, 8-7.1.2): Accept SUBMITrER: PeterJ. Gore W'dlse, Industrial Risk Insurers RECOMMENDATION: Replace as well as" in the first sentence with "and", replace "may be provided" with "shall be permitted" in the second sentence. SUBSTANTIATION: Cleans i tup. COMMITTEE ACTION: Accept.
(LOg #103) 85C- 120 - (6-7.2): Accept in Part SUBMITFER: PeterJ. GoreWillse, Industrial Risk Insurers RECOMMENDATION: Place the * after 0-7.2 and not (m).
Make the last sentence of (a), (c), (e), (f), and (j); the part q n order to warn ... (to the end) of (b) and (d); and "so that an evaluation can be made ... (to the end)" of (1); as NOTES. SUBSTANTIATION: This is all informational. COMMITIT.E ACTION: Accept in Part. COMMITTEE STATEMENT: Forpar t I of the submitter's recommendation, refer to Proposal 85C-121 (Log #144). Forepart 2, moving this information into notes would disrupt the continmty and not add to clarification.
(Log #144) 85C- 121 - (6-7.2(n)): Accept in Prindple SUBMITTER: Joe Vawek, Chicago, IL RECOMMENDATION: Reference in the "Note" to A-6-7.2(n) does not agree with Appendix. SUIkgI'ANTIATION: None. COMMITI'EE ACTION: Accept in Prindple.
Change "6-7.2" to "6-7.2*." Change "0o7.2 (m) *" to "007.2 (m)." Change "A-6-7.2 (m)" to "A-6-7.2." In note on 6-7.2(n) and 6.8.1.5(c); change reference to "A-6-7.2"
COMMITTEE STATEMENT: Editorial. Also refer to committee action on proposals 85C-153 (Log#CP5) and 85C-174 (LOg#CP6).
(Log #112) 85C- 1 2 2 - (68.1.1, 8-8.1.2, 7-8.1.1, 7-8.1.2): Reject SUBMITI~R: PeterJ. GoreWillse, Industrial Risk Insurers RECOMMENDATION: Relocate all the text, except the last sentence of 6-8.1.2 and 7-8.1.2 to the Appendix. SUBSTANTIATION: Informational material. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: See Committee Statement on Proposal 85C-9 (Log #48).
( Log #104) 85C- 123 - (6-8.1.4.1): Accept SUBMITTER:-PeterJ. Gore W'dlse, Industrial Risk Insurers RECOMMENDATION: Make this 6-8.1.4 since there is no 6-8.1.4.2. SUBSTANTIATION: To conform to the Manual of Style. C O M M I T r I ~ ACTION: Accept.
138
N F P A 8 5 C m A 9 5 R O P
(Log #105) 85C- 124- (6-8.1.5 Note): Accept SUBMITTERx PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: In the NOTE, delete (m). SUBSTANTIATION: Editorial. COMMITrEE ACTION: Accept.
(Log#151) 85C- 125 - (6-8.2, 7-8.2): Accept in Principle SUBMITTER: Edward G. Milone, Consolidated Edison of NY RECOMMENDATION: Revise text:
6-8.2 (gas): See Figures A-6-5.1.2(a), (b), and (d). 7-8.2 (oil): See Figures A-7-5.1.2 (a) and (c).
SUBSTANTIATION: Figures A-6-5.1.2(b) and (d) and A-7-5.1.2(c) and (e) are for a u t o - - t i c systems but appear in section entided Boiler Front Control (Supervised Manual.) COMMITTEE ACTION: Accept in Principle. COMMITTEE STATEMENT: Refer to Committee Action on Proposal 85C-182 (Log #138).
(Log #106) 85C- 126- (6-8.2.8(a), %8.2.8(a)): Accept SUBMrIq'ER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Revise as follows:
"An emergency shutdown shall initiate a master fuel trip." SUBSTANTIATION: Mandates the trip. COMMITrEE ACTION: AccepL
(Log #107) 85C- 127 - (6-8.2.9, %8.2.9): Reject SUBMITIlgR: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Add the following sentence:
"The following steps shall be followed on an emergency shutdown." SUBSTANTIATION: Indicates what should be done. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: The current wording of 6-8.2.9 and 7- 8.2.9 is consistent with the format of 6-8.2 and 7-8.2, and should not be changed.
(Log #152) 85C- 128 - (6-8.2.9(c), 7-8.2.9(c)): Accept in Principle SUBMITrER: Edward G. Milone, Consolidated Edison of NY RECOMMENDATION: Revise text:
" . . . have also tripped, close gas recirculating fan dampers." SUBSTANTIATION: Existing text in fuel gas and fuel oil sections does not address operator action regarding gas recirculation system in response to an emergency shutdown. COMMITrEE ACTION: Accept in Principle.
1. Add new 6-5.2.1.2, 6-8.2.10, 7-5.2.1.2, %8.2.10, and 8-5.2.1.2 to read as follows:
"When provided, regenerative air heaters and gas recirculation fans shall be operated, during all operations of the unit, in a manner recommended by the boiler manufacturer."
2. Delete 6-5.2.1.2(c), %5.2.1.2(c), and 8-5.2.1.2(c). 3. Renumberparagraphs as required.
COMMITTEE STATEMENT: It is not the intent of this standard to address all operating modes and designs involving gas recirculation fans. The changes made clarify this intent and expand text from the existing edition of this standard to include all modes of operation with gas recirculation fans and regenerative air heaters.
SUBSTANTIATION: Makes it mandatory and the correct refer- ence. COMMITTEE ACTION: Accept.
(Log #110) 85C- 131 - (6-9.2.1, %9.2.1): Accept SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Replace "are required" with "shall be
~ rovided." UBSTANTIATION: Conform to the Manual of Style.
COMMITTEE ACTION: Accept.
(Log #111) 85C- 132 - (6-9.2.1.1 (b), 7-9.2.i.1 (b)): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Place the second and third sentence in the Appendix. SUBSTANTIATION: Informational material. COMMIT]['EE ACTION: Reject. COMMITrEE STATEMENT: See Golnmittee Statement on Proposal 85C-9 (Log #48).
(Log #113) 85G- 133 - (6-9.2.2.1, 7-9.2.2.1): Accept in Principle SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Make this 6-9.2.2 and %9.2.2 and revise as follows:
"The followin~ operating procedures ~]aall be followed to prevent air/fuel ratio u~sets dur ingburner light-off:
(b) . . . burner, ~-ave the registers in the second burner shall be left o p e n . . .
(f) replace "does" with "shall"." SUBSTANTIATION: Conform to the Manual of Style. COMMITrEE ACTION: Accept in Principle. Also, reference in (f) to 6-9.2.2(e) and %9.2.2(e).
COMMITTEE STATEMENT: Editorial.
(Log #114) 85C- 134- (6-9.3.1, 7-9.3.1): Accept SUBMITTER: PeterJ. GoreWilise, Industrial Risk Insurers RECOMMENDATION: Renumber to 6-9.3 and 7-9.3. SUBSTANTIATION: Conform to the Manual of Style. COMMITTEE ACTION: Accept.
(Log #115) 85G- 135 - (7-3.1.5): Accept in Principle SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Make the last sentence of the first para- graph a NOTE. SUBSTANTIATION: Informational material. COMMITTEE ACTION: Accept in Principle.
1. Renumber the second paragraph of 7-3.1.5 as %3.1.6 and renumber subsequent paragraphs accordingly.
2. Change the last two sentences of the first paragraph of %3.1.5 a Note. COMMITTEE STATEMENT: This addresses the concerns of the submitter and includes further editorial clarification.
(Log #108) 85C- 129 - (6-9.1.2, %9.1.2): Accept SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Replace "does" in the first line with "shall." SUBSTANTIATION: Make it mandatory. COMMITrEE ACTION: Accept.
(Log #109) 85C- 130 - (6-9.1.3, %9.1.3): Accept SUBMITrER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Re~lace "does" in the first line with "shall."
Replace "NFPA 85A" with NFPA 8501."
(Log #116) 85C- 1~6 - (7-3.1.6): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Make the last sentence a NOTE. SUBSTANTIATION: Informational material. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: This criteria is concise and accurately portrays the intent of this paragraph.
139
NFPA 85C-- A95 ROP
(Log #117) 85C- 137- (7-3.1.8): Accept SUBMITrER: PeterJ. Gore Wilise, Industrial Risk Insurers RECOMMENDATION: Add in reference to NFPA 31, Liquid Fuel Burning Equipment. SUBSTANTIATION: None. COMMITI'EE ACTION: Accept.
(Log #118) 85C- 138- (%5.1.4): Accept in Principle SUBMITTER: PeterJ. GoreWiilse, Industrial Risk Insurers RECOMMENDATION: Replace "are" in the last sentence with "shall." SUBSTANTIATION: Editorial (See 6-5•1.4.) COMMITTEE ACTION: Accept in Principle.
Replace ~are" in the last sentence with "shall be." COMMITFEE STATEMENT: Editorial.
(Log #145) 85C~ 139- (7-5.2.1.2): Accept in Principle SUBMITrER: Joe Vavrek, Chicago, IL RECOMMENDATION: Was it intended that the second paragraph in %5.2.1.2(0 be designated 7-5.2.1.2(u)? SUBSTANTIATION: None. COMMITrEE ACTION: Accept in Principle. Assign the second paragraph of 7-5.2.1.2(0 as (u).
COMMI'Iq'EE STATEMENT: Editorial.
(Log #162) 85C- 140 - (%5.2.1.2): Reject SUBMITTER: William E. Cunningham, United Engineers & Constructors, Inc. RECOMMENDATION: Add the words from Section 6-5.2.1.2(d):
"Pressure testing of the header shall be required before the startup of any boiler." SUBSTANTIATION: Should we also request the pressure testing of oil headers? COMMITTEE ACTION: Reject. COMMITrEE STATEMENT: Current wording and Committee consensus does not require pressure testing of the oil header at startup.
(Log #ss) 85C- 141 - (7-5.2.1.2 and 8-5.2.1.2): Accept in Prindple S U B ~ William Cunningham, United Engineers & Construc- tors RECOMMENDATION: In Sections 7-5•2.1.2 and 8-5.2.1.2 add the words:
"Start the precipitator as per mannfacmrer's standard." SUBSTANTIATION: Start UP of the Boiler -
Section 8-5.1.5.1 (c) and 8-6.3.1.4. Theprocedure incorporated to meet the current code shall be to complete apurge of the unit before starting a precipitator. "Components (e.g., predpitators, fired reheaters) containing sources of ignition energy shall be pS u rgeck.." _ ~.
ection 8-5.2.1.2(e) Adjust air flow to purge flow rate. ~ection ~-I Purge flow rate (for coal) shall be greater than 25 percent but less than 40 percent full load volumetric air flow. • This was intended to prevent a high flow rate from causing an explosion in the precipitator. A high air flow rate could upset the ash.
The starting of the precipitator is not indicated but should be per manufacturer's requirements. The boiler will not be able to reach any significant load, unless the precipitator is started.
The NFPA code does require a precipitator to trip during a boiler master fuel trip. Sections 8-5.2.5.2. NFPA does require a post purge of the boiler after a master fuel trip. The paragraph which requires a precipitator trip has been a part of
the code from 1985. COMMITTEE ACTION: Accept in Principle.
Revise 6-5.2.1.2 as follows: 6-5.2.1.2" Starting Sequence. Operation of regenerative type air
heaters, precipitators, and gas recirculation fans, shall be included in the startup sequence where appropriate, in accordance with the manufacturers recommendation. The starting sequence shall be performed in the following order:
Delete 6-5.2.1.2(c) and the exception and redesignate subsequent items accordingly. Redesignate A-6-5.2.1.2(c) to A-6-5.2.1.2.
Revise 7-5.2.1•2 as follows: 7-5.2.1.2 Starting Sequence. Operation of regenerative type air
heaters, precipitators, and gas recirculation fans, shall be included in the startup sequence where appropriate, in accordance with the manufacturers recommendation. ~l'he starting sequence shall be performed in the following order:
Delete %5.2.1.2(c) and the exception and redesignate subsequent items accordingly.
Revise 8-5.2.1.2 as follows: 8-5.2.1.2 Starting Sequence. Operation of regenerative type air
heaters, precipitators, and gas recirculation fans, shall be included in the startup sequence where appropriate,, in .acc°rdance with the manufacturers recommendation. The starting sequence shall be PDerformed in the following order:
elete 8-5.2.1.2(c) and the exception and redesignate subsequent items accordingly. COMMITrEESTATEMENT: Reference to precipitators is included in these changes and addresses the concerns of the submitter. Additional changes are made in %5.2.1.2 and 8-5.2.1.2 to clarify the intent of the starting sequence• These changes are.also incorpo- rated in 6-5.2.1.2 for consistency.
(Log #S) 85C- 142 - (%5.2.1.2(p) CAUTION): Reject Note: This proposal appeared as comment 85C-133 which was held
for further study from the Annual 91 TCD, which was on proposal 85G1. SUBMYIWER: Susumu Sato, Mitsubishi Heavy Industries, Ltd., a an
"]~J~COMMENDATION: Revise the first sentence of the paragraph to read:
"%5.2•1.2(p) CAUTION: Total furnace air flow including gas recirculation shall not be reduced below purge rate and air flow shall be at least that which is required for complete combustion in the furnace." SUBSTANTIATION: In modern Japanese utility boilers, air flow is minimized and gas recirculation is introduced during start-up period before SCR (Selective Catalytic NOx Reductor) is put into operation to minimize NOx emission. At start up condition, gas recirculation flow contains high 02
concentration similar to air. Therefore, gas redrculation flow should be included in the total furnace flow rate which is used to evaluate the velocity through the furnace. COMMI'ITEE ACTION: Reject. COMMI'ITEE STATEMENT: Refer to Proposal 85G-93 (Log #2).
(Log #119) 85C- 143 - (7-5.2.3.3): Accept in Principle SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Revise to state:
"The shutdown procedures shall be the reverse of the start-up procedures and be accomplished by shutting down the burners sequentially as load is reduced. The burner shall be shut down in the following sequence." SUBSTANTIATION: To conform to the Manual of Style. COMMITrEE ACTION: Accept in Principle.
Revise paragraph to read as follows: "The shutdown procedures shall be the reverse of the start-up
procedures and be accomplished by shutting down the burners sequentially as load is reduced. Each burner shall be shut down in the following sequence." COMMITTEE STATEMENT: Editorial.
85C- 144- (7-5.2.3.3(e) (New)): Accept (Log #169) SUBMITFER: Bill Bass, Forney International, Inc. RECOMMENDATION: Add a new paragraph to read:
(e) f f the oil passages of the igniter are to be cleared into the furnace, initiate the spark or other ignition source for the igniter before opening the clearing steam or air valve. SUBSTANTIATION: Clearing of igniter oil passages is not addressed, however, large Class 1 igniters or several smaller igniters cleared simultaneously could introduce significant fuel into a furnace and should have an ignition source proven• COMMITTEE ACTION: Accept.
140
NFPA 85C-- A95 ROP
(Log #120) 85C- 145 - (7-5.2.3.4): Accept in Principle SUBMITrER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Revise to state:
"As the load is reduced, the remaining burners shall be cut out sequentially as described in %5.2.3.3 and the registers shall be left in the firing position. The last burner . . . " SUBSTANTIATION: To conform to the Manual of Style. COMMITTEE ACTION: Accept in Principle. Revise the paragraph to read as follows: 7-5.2.3.4 As the load is reduced, the remaining burners shall be
shut down sequentially as described in 7-5.2.3.3. The last burner shall not be scavengedunless associated Class I igniters are in use. COMMITTEE STATEMENT: These changes have been made to provide consistency with changes made to Chapter 6. Refer to Committee Action on Proposal 85C-95 (Log #89).
(Log #121) 85C- 146 - (7-5.2.3.5): Accept in Principle SUBMITTER: PeterJ. Gore Wilise, Industrial Risk Insurers RECOMMENDATION: Revise to state:
"When the last individual burner safety shutoffvalve is dosed, the main safety shutoffwalve shall be checked to determine that it has
shut." TIATION: To conform to the Manual of Style.
COMMITTEE ACTION: Accept in Principle. Revise paragraph to read as follows: 7-5.2.3.5 When the last individual burner safety shutoff valve is
closed, the main safety shutoff valve shall be checked to confirm that it has dosed. COMMITTEE STATEMENT: This provides further editorial daritication.
(Log #122) 85C- 147 - (7-5.2.3.8): Accept in Principle SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Add the following:
"The following shall be completed:" SUBSTANTIATION: Makes these requirements mandatory. COMMITTEE ACTION: Accept in Principle.
Revise as follows: "If fuel recirculation in the burner header is to be established, the
following shall be completed:" COMMITTEE STATEMENT: Editorial.
(Log #123) 85C- 148 - (7-5.4.7): Reject SUBMITFER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Relocate this to Appendix A-%3.1.11. SUBSTANTIATION: None. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: See Committee Statement on Proposal 85C-9 (Log #48).
(Log #5) 85C- 149 - (7-6.2.30) Exception): Accept in Principle SUBMITTER= H. C. Gery, Leeds & Northrup Co. RECOMMENDATION: Revise the Exception to read as follows:
Exception: Individual burner flame detectors and the total air flow measurement of the boiler control system may also be used for initiating master fuel trip systems. SUIKqTANTIATION: Figures 6-6.3.1.1, %6.3.1.1 and 8-6.3.1.1 call for a mandatory master fuel trip on "combustion air flow low." Paragraphs 6-6.2.3(i), 7-6.2.30) and 8-6.2.30) state:
"The mandatory master fuel trip sensing elements and circuits shall be independent of all other control elements and circuits."
Many have interpreted these statements to mean that a separate, dedicated "combustion air flow low" signal must be provided. Could such an event be detected by a simple pressure switch, there would be no problem.
However, on most installations, the total combustion air flow measurement is the weighted summation of many temperature compensated primary and secondary air flow measurements. It is not feasible to keep two duplicate systems (one for boiler control and one for burner management) in continuous service and agreement.
Because of dynamic considerations, the total air flow measurement
~ roperly belongs in the boiler control system. Therefore, it should e permissible for the total combustion air flow measurement of the
boiler control system to create the "combustion air flow low" trip signal, provided the design criteria of paragraph &S are observed. COMMITrEE ACTION: Accept in Principle. COMMITrEE STATEMENT: See Committee Action on Proposal 85G112 (Log #29).
(Log #12) 85G- 150- (%6.2.3(k) (New)): Reject SUBMIT'rE]R: C.D. Alvey, Lutherville, MD RECOMMENDATION: Add a new subsection (k) to read as follows:
(k) Redundant master fuel trip replays shall be provided. Trip coil monitoring devices shall be included to assure integrity of tripping functions. SUI~TANTIATION: See proposal for 6-6.2.3(k). If adopted, make "relay" plural to "relays" in sections 7-6.3.1.1 (d) 1, 2, 3, 5, 6, 7, and 8 and 7-6.3.1.2, 7-6.3.1.S, and 7-6.3.1.4. COMMITI'EE ACTION: Reject. COMMITrEE STATEMENT: See Proposal 85C-115 (Log #10).
(Log #13) 85G 151 - (Figure %6.3.1.1): Accept in Part SUBMITTER: C.D. Alvey, LutherviUe, MD RECOMMENDATION: Add an arrow to line connecting "Master fuel trip logic" box to "Master fueld trip relay(s)" box. Also, if proposal for section %6.2.3(k) is adopted, remove parentheses around the "s". SUBSTANTIATION: Editorial. COMMITTEE ACTION: Accept in Part.
1. Accept. 2. Reject.
COMI~TrEE STATEMENT: For item 2, see Proposal 85C-114 (Log #11).
(Log #124) 85C. 152 - (7-7.2): Accept in Part SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Place the * after %7.2 and not (g), replace "(q)" with "(p)".
Make the last sentence of (a), (g), (h), and (l); the part "in order to w a r n . . . (to the end)" of (b), (d), (e), and (f); the last two sentences of (c); and "so that an evaluation can be m a d e . . . (to the end)" of (n) as NOTES. SUBSTANTIATION: None. COMMITTEE ACTION: Accept in Part. COMMITrEE STATEMENT: For part 1 of the submitter's recommendation, refer to Proposal 85C-153 (Log #CP5).
For part 2, refer to Committee Statement on Proposal 85C-120 (Log #103).
(Log #CP5) 85C- 153- (7-7.2): Accept SUBMITTER: Technical Committee on Multiple Burner Boilers, RECOMMENDATION: 1. Add an asterisk after 7-7.2.
2. Delete asterisk after %7.2(g). 3. Change note in 7-7.2(p) to read: NOTE: In addition to the required alarms, recommended alarms
and monitors are listed in A-%7.2. 4. Change note in %8.1.5(c) to read: NOTE: Recommended additional alarms are listed in A-7-7.2. 5. Change "A-7-7.2(g)" to "A-%7.2".
SUBSTANTIATION: These are editorial corrections, plus matching those changes made in Section 6-7.2. Refer to committee action on
(Log #125) 85C- 154- (Chapter 8): Accept $UBMITI~R: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Replace all reference to "NFPA 85F" to "NFPA 850S." SUBSTANTIATION: Editorial. COMMITTEE ACTION: Accept.
141
N F P A 8 5 C B A 9 5 R O P
(Log #126) 85G 155 - (8-2.2, 8-2.3): Reject SUBMITrER: PeterJ. GoreWilise, Industrial Risk Insurers RECOMMENDATION: Place all except the second to last sentence of 8-2.2.2 and the last sentence of 8-2.2.3 in the Appendix. SUBSTANTIATION: This is informational material. COMMITTEE ACTION: Reject. COMMITI'EE STATEMENT: See Committee Statement on Proposal 85C-9 (Log #48).
(Log #128) 85C- 156- (8-3.1.2): Accept in Principle SUBMITTER: PeterJ. Gore W'dise, Indnswial Risk Insurers RECOMMENDATION: Revise the last sentence to state:
"This shall includes the installation..." SUBSTANTIATION: Mandates the installation. COMMYITEE ACTION: Accept in Principle.
Revise the last sentence to state: "This shall include, where necessary, the installation..."
COMMITTEE STATEMENT: This provides editorial dariflcatlon.
(Log #127) 85C- 157- (8-3.2): Accept SUBMrrI'ER: PeterJ. GoreWUlse, Industrial Risk Insurers RECOMMENDATION: Replace "NFPA 85F ~ with "NFPA 8503." SUBSTANTIATION: Editorial. COMMITTEE ACTION: Accept.
85C- 161 - (8-5.2.1.2(q)): Accept SUBM1TTER: Joe Vavrek, Chicago, IL RECOMMENDATION: Second fine should read:
" . . . in service, it i s . . . " SUBSTANTIATION: None. COMMITrEE ACTION: Accept.
(Log#146)
(Log #4) 85C- 162 - (8.-5.2.2.8): Reject Note: This proposal appeared as comment 85C-173 which was held
for further study from the Annual 91 TCD, which was on proposal 85G1. SUBMITIT~ Susumu Sato, Mitsubishi Heavy Industries, Ltd.,
JI~Ca~MMENDATION: Revise paragraph to reach "Total furnace air flow including gas recirculation shall not be
reduced below purge rate and air flow shall be at least that which is required for complete combustion in the furnace." SUBSTANTIATION: In modern Japanese utility boilers, air flow is minimized and gas recirculation is introduced during start-up period before SCR (Selective Catalytic NOx Reductor) is put into operation to minimize NOx emission.
At start up condition, gas recirculation flow contains high 02 concentration similar to air. Therefore, gas recirculation flow should be included in the total furnace flow rate which is used to evaluate the velocity through the furnace. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: Refer to Proposal 85C-93 (Log #2).
(Log #129) 85C, 158 - (8-4.4): Reject SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Place 8-4.4.1 in the Appendix. Make 8-4.4.9 a NOTE to 8-4.4.3 and replace "following" with
"these." Make the last sentence of 8-4.4.$(a) a NOTE to 8-4.4.3(a).
SUBSTANTIATION: Informational material. COMMITrEE ACTION: Reject. COMMITI'EE STATEMENT: Revising this section to include notes as proposed by the submitter confuses the intent of this section. The current wording is appropriate.
(Log #150) 85C- 159 - (8-5.1.2): Accept in Principle SUBMITTER: Joe Vavrek, Chicago, IL RECOMMENDATION: Second line should read:
" . . . Figures A-8-5.1.2(a) through (c)." SUBSTANTIATION: None. COMMITI"EE ACTION: Accept in Principle.
I Make the submitters change, and also replace the " /" symbol throughout the document for each reference to the figures. COMMITrEE STATEMENT: Editorial
(Log #I 30) 85C- 163 - (8-5.2.3.3): Accept SUBMITTER: PeterJ. Gore WUlse, Industrial Risk Insurers RECOMMENDATION: Revise to state:
"As the boiler load is reduced, the following nrocedures shall be ~ u v .
SUBSTANTIATION: Indicate what must be done. COMMITTEE ACTION: Accept.
(Log #131) 85G 164- (8-5.2.3.4): Accept in Principle SUBMITTER: PeterJ. Gore Willse, Industrial Risk Insurers RECOMMENDATION: Revise to state:
'WVhen all pulverizers and igniters have been removed from service, a unit nurse shall be nerformed ." SUBSTANTIATIONf To conform to the Manual of Style. COMMITrEE ACTION: Accept in Principle.
Revise text as follows: "When all pulverizers and igniters have been removed from service,
the purge rate airflow shall be verified and a unit purge shall be performed." COMMITTEE STATEMENT: This more appropriately clarifies the intent of this paragraph and maintains the use of the word verify.
(Log #32) 85C- 160 - (8-5.2.1.2(e)): Reject SUBMITI'ER: W'dliam Cunningham, United Engineers & Construc- tors RECOMMENDATION: In Section 8-5.2.1.2(e) change the words:
(e) Adjust air flow to purge flow rate. Section 3-1 Purge flow rate (for coal) shall be greater than 25 percent but less than 40 percent full load volumetric air flow. This was intended to prevent a high flow rate from causing an explosion in the precipitator. A high air flow rate could upset the ash. SUBSTANTIATION: This wording was found in the old 85E standard for coal fired units. I would like the committee to reconsider including it into the 85C. COMMITrEE ACTION: Reject. COMMITrEE STATEMENT: The information provided concern- ing purge rate is adequately covered in Chapter $ definitions.
(Log #132) 85G 165 - (8-5.3.1): Reject SUBMITTER: PeterJ. Gore Wilise, Indusu'ial Risk Insurers RECOMMENDATION: Place this in the Appendix. SUBSTANTIATION: Informational material. COMMITTEE ACTION: Reject. CoMMrITEE STATEMENT: See Committee Statement on Proposal 85C-9 (Log #48).
(Log #133) 85G- 166 - (8-5.4.3): Accept in Principle SUBMITTER: PeterJ. GoreW'fllse, Industrial Risk Insurers RECOMMENDATION: Revise to state:
"When raw coal hangs up ahead of the feeder, orwet coal or changing coal quality are encountered, the igniters shall be placed in service on all operatin!g burners. If the malfunction can be restored or adequate igmtion energy can be supplied before the
• burner ignition is lost, the pulverizer subsystem shall be permitted to operate provided there is a stable flame. If the flame becomes unstable or is extinguished, then the burner and subsystem shall be shut down. Start-up conditions shall be established before coal feed is restored."
142
NFPA 8 5 C - - A95 RO P
SUBSTANTIATION: None. COMMITrEE ACTION: Accept in Principle.
Revise 8-5.4.3 to read: ~When raw coal hangs up ahead of the feeder, Or wet coal or
changing coal quality are encountered, the igniters shall be placed in service on all operatiog burners. If the malfunction can be restored or adequate ignition energy can be supplied before burner flame is lost, the pulve/'izer subsystem shall be l~ermitted to operate provided there is a stable flame. If the flame becomes unstable or is extinguished, then the burner and subsystem shall be shut down. Start-up conditions shall be established before coal feed is restored.
NOTE: Raw coal hangups ahead of the feeder causing unstable or intermittent firing and wet coal or changing coal quality causing flame instability are common emergendes that may arise when firing up.ulverized coal. These emergencies can create hazardous condi-
ons by allowing unburned fuel to accumulate in the furnace." COMMITrEE STATEMENT: Editorial. The note has been added which includes advisory information that was part of the original paragraph.
( Log #171) 85C- 167- (8-5.4.3): Accept in Principle S U I $ ~ Bill Bass, Forney International, Inc. RECOMMENDATION: Change next to last sentence to read:
~However, if the main burner flame on any burner of any pulver- izer subsystem is extinguished and 1) Class 1 igniters are not in operation or 2) it cannot be proven that there was a loss of coal flow, then that burner or subsystem shall be shutdown.. ." SUBSTANTIATION: This paragraph addresses the loss of flame due to interruption of coal flow. However, due to the first and second sentences, it implies that it is acceptable to continue to deliver ~wet or poor quality ~ coal at full flow with no main flame detected. 1 do not believe that is the intent nor do I believe that is a safe practice. If that is the intent, then it is in contradiction to 8- 5.2.1.2 (m) and (n). COMMrITEE ACTION: Accept in Principle. COMMrrrF_,E STATEMENT: Refer to the action on Proposal 85G- 166 (Log #133).
( Log #134) 85G- 168 - (8-5.5.4): Reject SLrBMITIY.,R: PeterJ. Gore W'dlse, Industrial Risk Insurers RECOMMENDATION: Place all except the first sentence in the Appendix. SUlgb~ANTIATION: Informational material. COMMITrEE ACTION: Reject. COMMITrEE STATEMENT: See Committee Statement on Proposal 85G-9 (Log 048).
(Log #14) 85C- 169 - (8.6.2.3(k) (New)): Reject SUBMITTER: C.D. Alvey, Lutherville, MD RECOMMENDATION: Add a new subsection (k) to read as follows:
(k) Redundant master fuel trip relays shall be provided. Trip coil monitoring devices shall be Included to assure integrity of tripping functions. SU]gb'TANTIATION: See proposal for 6-6.2.3(k). If'adopted, make "relay ~ plural to ~relays" in sections 8-6.3.1.1 (d) 1, 2, 3, 5, 6, and 8- 6.3.1.2 and 8-6.3.1.3. COMMITTEE ACTION: Reject. COMMITTEE STATEMENT: See Proposal 85C-113 (Log #10).
(Log #135) 85C- 170 - (8.6.3.1.1): Reject SUBMrITRR:- PeterJ :Gore Willse, Industrial Risk Insurers RECOMMENDATION: Make this NOTES to Figure 8-6.3.1.1. SUBSTANTIATION: None. COMMITrEE ACTION: Reject. COMMNWEE STATE~F_,NT: See Committee Statement on Proposal 85C-115 (Log #99).
(Log #15) 85G 171 - (Figure 8-6.3.1.1): Accept in Part SUBMITI'ER: G.D. Aivey, Lutherville, MD RECOMMENDATION: Add an arrow to one of the lines connect- ing "Master fuel trip logic ~ box to UMaster fuel trip relay(s)" box and remove the other line. Also, if proposal for 8.6.2.3(k) is adopted, remove the parentheses around the %~. SUBSTANTIATION: Editorial. COMMITTEE ACTION: Accept in Part
1. Accept. 2. Reject.
COMMITTEE STATEMENT: See Proposal 85C-114 (Log #11).
85C- 172 - (8-6.3.1.1 (d) 7.): Accept in Principle (Log #174) SUBMI'IWER: Bill Bass, Forney International, Inc~ RECOMMENDATION: Change last sentence to read:
~The decision as to specific requirements or implementation of this trip shall be a design decision based on furnace configuration, total number of burners, number of burners affected as a percentage of burners in service, interlock system, and load level. ~ SUBSTANTIATION: To be of anyvalue, the flames lost must be continuously compared to the overall unit status (i.e., burners in operation). Simple fixed number does not address the issue. COMMITrEE ACTION: Accept in Principle.
Change last sentence of paragraph 6-6.3.L 1 (d)6 to read: "The decision as to specific requirements or implementation of this
trip shall be a design decision based on furnace configuration, total number of burners, number of burners affected as a percentage of burners in service, arrangement of burners affected, interlock s~ctem, and load level. ~
hangs last sentence of paragraph 7-6.3.1.1(e)9 to read: "The derision as to spedfic requirements or implementation of this
trip shall be a design decision based on furnace configuration, total number of burners, number of burners affected as a percentage of burners in service, arrangement of burners affected, interlock system, and load level. ~
Change last sentence of paragraph 8-6.3.1.1(d) 7 to read: "The decision as to specific requirements or implementation of this
trip shall be a design decision based on furnace configuration, total number of burners, number of burners affected as a percentage of burners in service, arrangement of burners affected, interlock
tem, and load level." MMITFEE STATEMENT: Minor editorial changes have been
made to the submitter's recommendation, and these changes have also been made to Chapters 6 and 7 accordingly.
(Log #136) 85C- 173 - (8-7.2): Accept in Part SUBMI'FrER: PeterJ. Gore W'flise, Industrial Risk Insurers RECOMMENDATION: Place the * after 8-7.2 and not (n).
Make the last sentence of (g), (h), and (I); and ~in order to warn.. ." in (b) into NOTES. SUBSTANTIATION: Editorial and informational material. COMMITrEE ACTION: Accept in Part.
COMMITFEE STATEMENT: For part 1 of the submitter's recommendation, accept and refer to Proposal 85C-174 (Log #CP6).
For part 2, reject and refer to Committee Statement on Proposal 85C-120 (Log#103).
(Log #GP6) 85C- 174- (8-7.2): Accept SUBMI'FFER: Technical Committee on Multiple Burner Boilers, RECOMMENDATION: 1. Add an asterisk after 8-7.2.
2. Delete asterisk after 8-7.2(n). 3. Change note in 8-7.2(0) to read: NOTE: In addition to the required alarms, recommended alarms
and monitors are listed in A-8-7.2. 4. Change "A-8-7.2(n) ~ to "A-8-7.2 ".
SUBSTANTIATION: These are editorial corrections, matching those changes made in Section 6-7.2. Refer to committee action on proposal 8~C-121 (Log#144). COMMFFrEE ACTION: Accept.
143
NFPA 85C-- A95 ROP
(Log #137) 85C- 175 - (9-1.3): Accept in Principle SUBMITTER: PeterJ. Gore Wiilse, Industrial Risk Insurers RECOMMENDATION: Revise to state:
"An inspection and maintenance schedule shall be established and followed. The schedule shall be as follows:
Daily Flame failure detection system, low water level cutout and alarm. Weekly: Igniter and burner operation. Monthly Fan and airflow interlocks, fuel safety shutoffvalves for
leakage, high steam pressure interlock, fuel pressure and tempera- ture interlocks for oil, high and low fuel pressure interlock and gas strainer and drip leg for gas. Semiannually Burner components, flame failure system compo-
nents, piping, wiring, and connections of all interlocks and shutoff valves, calibration of instrumentation, combustion control system." SUBSTANTIATION: None. COMMITTEE ACTION: Accept in Principle. Add to Appendix A as follows: A-9-1.3 An example of an Inspection and Maintenance Schedule is
as follows: Daily Flame failure detection system, low water level cutout and
alarm. Weekly: Igniter and burner operation. Monthly Fan and airflow interlocks, fuel safety shutoffvalves for
leakage, high steam pressure interlock, fuel pressure and tempera- ture interlocks for oil, high and low fuel pressure interlock and gas strainer and drip leg for gas.
Semiannually: Burner components, flame failure system compo- nents, piping, wiring, and connections of all interlocks and shutoff valves, calibration of instrumentation, combustion control system." COMMITTEE STATEMENT: The proposal mandates a mainte- nance schedule. Due to the variety of equipment and operating procedures a maintenance schedule shouldhe recommended only, and thus is included as appendix material.
(Log #147) 85C- 176 - (9-2.1.4): Accept SUBMITTER: Joe Vavrek, Chicago, IL RECOMMENDATION: Suggest 9-2.1.4 begin with word "Operat- ing" to be consistent with previous sections. SUBSTANTIATION: None. COMMITTEE ACTION: Accept.
(Log #148) 85C- 177- (10-1, C-l): Accept in Principle SUBMITTER: Joe Vavrek, Chicago, IL RECOMMENDATION: NFPA 30, NFPA 54, NFPA 85A and NFPA 85F in C-I.1 and API-RP 2003-1982 in C-1.2.1 as stated in C-1 " . . . should not be considered part of the requirements of this docu- ment," yet they are listed in 10-1 as " . . . shall be considered part of the requirements of this document. Which is correct? SUBSTANTIATION: None. COMMITrEE ACTION: Accept in Principle. COMMITrEE STATEMENT: The concerns of the submitter will be editorially handled by NFPA staff.
(Log #CP11) 85C- 178 - (A-1-2.2 (New)): Accept SUBMITTER: Technical Committee on Multiple Burner Boilers, RECOMMENDATION: Revise A-f-5.2.1.2(c)IB as follows:
B. Although NOx and other emissions during startup and very low load operation are low, increasingly stringent emission limits could result in these low levels exceeding allowable limits. Deviation from the open register lightoff procedure, continuous purge and minimum air flow requirements defined in this standard to meet these limits is not recommended. There is insufficient data and operating experience to justify changes to this standard. SUBSTANTIATION: This material is needed to identify the issues and concerns regarding operatio n of boilers at less than 25 percent airflow. See also Proposai85C-179 (Log#CPl0). COMMITrEE ACTION: Accept.
(Log #CP10) 85C- 179- (A-2-7.1 (c) (New)): Accept SUBMITTER: Subcommittee on Multiple Burner Boilers, RECOMMENDATION: Add a new appendix section as follows: A-2-7.1 (c) The minimum air flow (273%) value is based on
historical experience in reducing the occurrence of furnace explosions. This value is based on safety considerations and could be in conflict with economics or emission limits. Factors considered in establishing the minimum air flow include:
- Removal o f combustibles and products of combustion; - Cooling requirements for out of service burners; - Accuracy of total, individual burner, and other air flow measure-
ments; - Accuracy of burner air and fuel distribution; - Effect of thermal and pressure transients within the furnace on
the air and fuel flows; - Impact of air leakage; - Wear and deterioration of the unit and equipment; and - Operational and control margins.
SUBSTANTIATION: This appendix material provides important background support for understanding paragraph 2-7.1 (c). COMMITrEE ACTION: Accept.
(Log #159) 85C- 180 - (A-G2 IIB(c) and A-7-8 liB(c)): Accept in Principle SUBMITTER: Leo Donovan, Factory Mutual Eng. & Research RECOMMENDATION: Needs classification. SUBSTANTIATION: Text is confusing. It states that the igniter header low pressure switch is bypassed when the supervisory shutoff valves are closed, but that it must be proved closed before opening
niter safety shutoff valves. MMI'I'YEE ACTION: Accept in Principle.
In A-6-2 liB(c), delete the last sentence that reads: "Low ignition header pressure trip switch is bypassed by a circuit
completed only when ignitor supervisory shutoffvalves are closed". In A-7-8 lib (c), delete the last sentence that reads: "Ignitor header low fuel pressure trip switch is bypassed by a circuit
completed only when individual ignitor supervisory shutoff valves are closed". COMMI'I'I'EE STATEMENT: These specific changes address the submitter's concerns.
(Log #175) 85C- 181 - (A-6-3.1.6 (New)): Accept in Principle SUBMITTER~ Joseph IL Buchanan, ITT Engineered Valves RECOMMENDATION: Add the following to A-6-3.1.6: A-6-3.1.6 Atmospheric vent valves located between shutoffvalves
are intended to relieve any gas pressure which may build up due to failure of the first (upstream) shutoffvalve. This minimizes the Photential for leakage into an idle furnace. To perform properly,
ese valves shouldbe large enough to relieve gas to atmosphere at a rate equal to the potential leakage rate. In absence of other justification, vent pipe sizes and vent valve port diameters should conform to Table A-6-3.1.6. Vents from safety shutoff systems may be manifolded, in which case the cross-sectional area of the manifold pipe should be equal to, or greater than, the sum of the cross- sectional areas of the two largest vents involved.
Table A-6-3.1.6
Shutoff Swtem Vent Port Size
< or = 1 1/2 in, 3/4 in. 2 in. 1 in.
2 1/2 in. to $ in. 1 1/4 in. 3 1/2 in. 1 1/2 in.
4 in. to 5 in. 2 in. 5 1/2 in. to 6 in. 2 1/2 in.
8 in. 3 1/2 in. > 8 in. 15% of supply line
cro$s-Sec. 2 x e a
144
NFPA 85C-- A95 ROP
SUBSTANTIATION: Paragraph 6-3.1.6 mandates a vent to ensure no leakage into an idle furnace. Clearly, this is in tended to relieve any gas which may leak past the first shutoff valve.
No mandatory vent valve or pipe size is given in the body of the spec, to avoid being too design-s-pecific. While this may be justified, the user should at least be made clearly aware of the intent of the requirement so (s)he can make responsible choices on sizing. While no t preventing users from installing a 1/2 in. solenoid vent falve on a 6 in. main line, the above appendix paragraph and table help guide the reader to appropriate choices. The table is sourced from industrial Risk Insurer s Interpretive Guide IM.4.1.1 for oil and gas fired boilers.
No information is provided on the manifolding of vent lines from muliple burners or igniters. The above useful guidance is drawn from British Standard BS 5885 Part 1, paragraph 4.4. COMMITrEE ACTION: Accept in Principle. Add the following to A-6-3.1.6: A-6-3.1.6 Atmospheric vent valves located between shutoffvalves
are in tended to relieve any gas pressure which may build up due to failure of the first (upstream) shutoff valve. This minimize-s the Pthotential for leakage into an idle furnace. To perform properly,
ese valves s h o u l d b e large enough to relieve gas to a tmosphere at a rate equal to the potential leakage rate. In absence of other justification, vent pipe sizes and vent valve port diameters should conform to Table A-6-3.1.6.
Table A-6-3.1.6
Shutoff SystemMinimum Verlt Port and Line Size
If such a deviation from purge air flow is neccesary at low loads/ start-up operation. The following is recommended:
Three totally independen t CO analyzer trains should be installed before the air heater.
Two out of three analyzers should indicate less than 100 ppm CO. If ' the third analyzer reads over 200 ppm CO, all analyzers should
be leak tested and recalibrated within 24 hours. ff after testing and recalibrating of the analyzer's low CO can' t be
conclusively demonstrated, air flow rate should be slowly increased to purge rate over a period of 5 minutes.
Operators shou l dbe trained to accomplish the above. Extensive testing of the boilers at low loads should be undertaken
prior to effecting regular operation at low air flow. Automatic MFT on high CO (2 out of 3) for operation less than
25 percent air flow. tsontrol/ indication analyzer may also be used for protection•
SUBSTANTIATION: Local and national emission regulations are in a state of flux. It may no longer be possible to meet emissions standards at low load at purge air flow rate. Operation of a uni t at levels above economic dispatch point in order to also meet emission limits is unnecessarily restrictive in a competitive electricity supply market and may be contrary to global warming (CO 2 ) consiffer- ations. Ways need to be found to change operations of utility-scale boilers at opt imum efficiency over the entire load range. COMMITTEE ACTION: Reject. COMMITrEE STATEMENT: Operation at less than 25 percent air flow is hazardous and is no t suppor ted by this standard. Refer to Committee Action on Proposal 85C-179 (Log #CP10) and Proposal 850178 (Log #CP11).
< or = 1 1/2 in. 3/4 in. 2 in. 1 in.
2 1/2 in. to 3 in. 1 1/4 in. 31/2 in. 1 1/2 in.
4 in. to 5 in. 2 in. 5 1/2 in. to 6 in. 21/2 in.
8 in. 31 /2 in. > 8 in. 15% of supply line
CFO$$-$eC, a r e a
Add a new paragraph as follows: A-6-3.1.8 When vents are manifolded from safety shutoff systems, the cross-sectional area of the manifold pipe should be equal to, or greater than, the sum of the cross-sectional areas of the two largest vents involved. COMMITrEE STATEMENT: Reference to manifolded systems is more appropriate in conjunction with paragraph 6-3.1.8. Other changes are editorial.
(Log #138) 85G- 182 - (Figure A-6.5.1.2(b), (c), (d)): Accept in Principle SUBMITTER: PeterJ . Gore Willse, Industrial Risk Insurers RECOMMENDATION: Renumber these figures as follows:
Figure A-6.5.1.g(b) to Figure A-6.8.1.1 (a) Figure A-6-5.1.2(c) to Figure A-6.8.1.1 (b) Figure A-6-5.1.2(d) to Figure A-6.5.1.2(b) Figure A-7-5.1.2 (d) to Figure A-7-8.1.1 (a) Add a Recirculating Valve (H) to Figures A-7-5.1.2(a) and (b).
SUBSTANTIATION: None. COMMITTEE ACTION: Accept in Principle.
~ . Accept renaming Figures. • Reject addition of Recirculation Valve (H) to Figures A-7-
5.1.2(a) and (b). 3. Also rename Figure A-7-5.1.2(e) to Figure A-7-5A.2(d). 4. Revise all references to the r enumbered sections accordingly.
COMMITrEE STATEMENT: A recirculating valve is not typical in light oil systems. Further changes are editorial.
(Log #178) 85C- 183 - (A-6.5.2.1.2(c)): Reject SUBMITTER: John B. Herbert, Generation Victoria RECOMMENDATION: Revise text:
NO x emissions on startup and at low loads, while very low, may exceed increasingly stringent local a n d / o r national regulations. Consequently,. . .the open register light-off and purge rate prncedures specafied m this s tandard for start-up a n d / o r low loads may be affected, particularly for large utility boilers ( > 1.2 x 109 Btu /hr ) .
(Log #177) 8 5 0 184- (A-9-2.1.2 (New)): Accept in Principle SUBMITTER: Shelton Ehrlich, EPRI RECOMMENDATION: Add an Appendix item A-9-2.1.2 to read:
"The cost of simulators has been reduced and their uses as a training aid is recommended. Many unusual emergency situations can be readily simulated. Plant managers should select and train operators so that in emergency situations, requiring quick action, any operator can initiate a main fuel trip on h i s / he r own initiative." SUBSTANTIATION: Explosions have occurred because operators did not feel empowered to take action when they believed an M v r was needed. There are two causes, (1) a lack of training on complex or unusual events and (2) a lack of empowerment of plant person- nel. With down sizing the quality of remaining personnel becomes even more important than in the past. This proposal will be controversial and is offered as an appendix
item to stimulate discussion. COMMITTEE ACTION: Accept in Principle.
Revise the second sentence of 9-2.1.1 to read as follows: "This program can consist of review of operating manuals,
videotapes, p rogrammed instruction, testing, simulators, and field training, among others". Add a new 2-7.3 as follows: "2-7.3 Proper procedures shall be established for taking appropri-
ate and timely action including reducing load, tr ipping equipment, or calling for outside assistance in case of emergency". COMMITrEE STATEMENT: This provides recognition of simulators for operator training. There are a variety of training methods, and there is no reason to highlight one particular training method in the appendix over the other available methods. The addition of paragraph 2-7.3 responds to the submitter 's concern of lack of empowerment of plant personnel.
(Log #CP7) 85C- 185 - (Appendix B): Accept SUBMI'ITER: Technical Committee on Multiple Burner Boilers, RECOMMENDATION: 1. Move cross references for Chapter 7 Fuel Oil Systems one column to the right so that they fall under the old fuel oil standard, NFPA 85D.
2. Move cross references for Chapter 8 Pulverized Coal Systems one colunm to the right so that they fall under the old pulverized coal standard, NFPA85E. SUBSTANTIATION: Editorial. COMMITYEE ACTION: Accept.
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(Log #149) 85C- 186 - (C-I-2.2, 10-1.2.3): Accept in Principle SOBMIT~R: Joe Vawek, Chicago, IL RECOMMENDATION: ASTM D388-1977 and ASTM D396-80 are listed differently in C~1.2.2 and in 10-1.2.3. Which is correct? SUBSTANTIATION: None. COMMITYEEACTION: Accept in Principle. COMMITTEE STATEMENT: The concerns of the submitter will be editorially handled by NFPA staff.
(Log #5O) 85C- 187 - (Appendix D): Reject SUBMITYER: William Gunningham, United Engineers & Construc- tors RECOMMENDATION: Add a new Appendix D to read as follows:
Appendix D General Gonsideratlons for Gontrol Logic
This Appendix is not a part of the requirements of this NFPA document, but is included for information purposes only.
D-1 Requirement for Independence. The logic system performing the safety functions for burner management shall not be combined with any other logic system. These burner management safety functions shall include but not be limited to, proper purge interlocks and timing and flame monitoring.
D-2 A control system shall be designed to permit a safe shut down of the system, if a failure should occur within the system.
D-3 Simulation and testing of the system should be completed before the boiler start up. The testing and simulations should be completed on the entire system to ensure proper coordination between functional logic systems.
D-4 The system should furnish the operator critical information, in the application of proper alarms or alarm outputs from the system.
D-5 The system logic designer should take into consideration two out of three logic for master fuel trips.
D-6 If GRT/Keyboard Control is used in the design of the logic system, the following should be considered.
• A hard wired push button(s) to trip the system. • A redundant GRT and keyboard should be considered during
the design. • The system outputs should be hardwired to devices required to
trip on a master fuel trip. • Inputs which furnish data which may cause a master fuel trip
should also be hardwired. • Communication with other systems should be limited to data
required for graphics, data and start/stop. Backup hard wired trips should also be included.
D-7 A single component failure within the logic system should not prevent a mandatory master fuel trip or any individual safety related, subsystem Irip.
D-8 The designer may consider redundant logic for large boiler logic systems. The logic will have to transfer to the redundant logic and should be so designed to permit transfer back to thepr ime logic. The redundant logic shall be designed so that the back up system will cause a master fuel trip upon logic failure of the prime and redundant modules.
D-9 The designer should consider first out logic to permit an ease of trouble shooting, after a trip. SUBSTANTIATION: This Appendix would be a guide for the proper application of programmable logic controllers for safety system.
Items such as D-1 are contained within the specification, but are listed here as a reminder to the designer.
COMMITYEE ACTION: Reject. COMMITI'EE STATEMENT: An appendix is not the place to include mandatory requirements, which most of these are. They should be in the main body of the standard.
D-1 This requirement is properly stated in 4-3.2.3. D-2 This requirement is properly stated in 4-3.1. 13-3 This requirement is stated in 2-4.1, 2-4.4, 2-5.4, and 6-6.2.4. D-4 The intent of this statement is in 4-7 and 6-7, 7-7, and 8-7. D-5 This is a minimum standard and two out of three logic is not
discouraged by the standard. D-6 The intent of these comment is covered by 4-3.2.2. Also, see
Committee Action on Proposal 85G-149 (Log #5). D-7 This requirement is properly stated in 4-$.2.2(g). D-8 Programmable logic controller redundancy is a way of meeting
the requirements of 4-3. This is design specific. D-0 This requirement is stated in 6-6.2.3(c) and 6-6.3.1.2.
(Log #7) 85C- 188 - (Entire Document): Reject SUBMITI'ER: Ramesh Khanna, United Engineers & Constructors RECOMMENDATION: Would NFPA allow cyclone operation without coal scanners if the gas flame from Class I igniters is continuously monitored dunng coal and gas combination firing? SUBSTANTIATION: Coal/Gas Combination Firin~
v
Cvdone Fired Boiler Does it meet the intent of NFPA 85C code? Gyclone flame out
condition will be established as follows: (1) Class 1 continuous igniter flame scanner shows no flame. (2) Acoustic pyrometer (located above the cyclone) shows rapidly
decaying flue gas temperature in the control room display screen. NOTE: Supporting material is available for review at NFPA
headquarters. COMMITTEE ACTION: Reject. COMMITFEE STATEMENT: This is a design specific application involving the details of cyclones that are beyond the scope of NFPA 85C~ Refer to paragraph 1-2.2 which allows for alternative technol- ogy.
NFPA does not approve devices or applications. This is a function of the authority having jurisdiction involved with a particular application.
No specific change has been recommended by the submitter.
(Log #GP4) 85C~ 189- (Entire Document): Accept SUBMIIITJ~ Technical Gommi~ee on Multiple Burner Boilers, RECOMMENDATION: Change "85A ~ to "8501" throughout document. SUBSTANTIATION: Editorial. COMMITTEE ACTION: Accept.
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