BSR/IIAR 2-201x - IIAR ORG - International Institute of ... Standards/Review/2-3... · R1 BSR/IIAR 2-201x Standard for Safe Design of Closed-Circuit Ammonia Refrigeration Systems

R1

BSR/IIAR 2-201x

Standard for Safe Design of Closed-Circuit Ammonia Refrigeration Systems

November 14, 2014

Public Review #3 Draft

Notes on the Standard Text

Metric Policy

The IIAR metric policy for ANSI standards, bulletins and all IIAR publications is to use the common

engineering “inch-pound” (IP) unit system as the primary unit of measure, and the International System

of Units (SI), as defined in United States National Institute of Standards and Technology Special

Publication 330 “The International System of Units,” for secondary units.

Normative/Informative Elements

This standard includes normative (required) provisions. The Foreword and Appendices are non-

mandatory. Informative material shall never be regarded as a requirement.

Notice

The information contained in this Standard has been obtained from sources believed to be reliable.

However, it shall not be assumed that all acceptable methods or procedures are contained in this document,

or that additional measures may not be required under certain circumstances or conditions. The Standards

Committee and Consensus Body that approved the Standard were balanced to assure that individuals from

competent and concerned interests have had an opportunity to participate. The proposed Standard was

made available for review and comment for additional input from industry, academia, regulatory agencies

and others.

The IIAR makes no warranty or representation and assumes no liability or responsibility in connection

with the use of any information contained in this document.

Use of and reference to this document by private industry, government agencies and others is intended to

be voluntary and not binding unless and until its use is mandated by authorities having jurisdiction.

The IIAR does not “approve” or “endorse” any products, services or methods. This document shall not be

used or referenced in any way which would imply such approval or endorsement.

Note that the various codes and regulations referenced in this document may be amended from time to

time and the versions referenced herein are the versions of such codes and regulations set forth in Chapter

3 of this Standard.

The IIAR uses its best efforts to promulgate Standards for the benefit of the public in light of available

information and accepted industry practices. However, the IIAR does not guarantee, certify, or assume

the safety or performance of any products, equipment or systems tested, installed, or operated in

accordance with IIAR’s Standards or that any tests conducted under its Standards will be nonhazardous

or free from risk.

This Standard is subject to periodic review. Up-to-date information about the status of the Standard is

available by contacting IIAR.

Copyright

This document may not, in whole or in part, be reproduced, copied or disseminated, entered into or stored

in a computer database or retrieval system, or otherwise utilized without the prior written consent of the

IIAR.

Copyright © 2014 by

INTERNATIONAL INSTITUTE OF AMMONIA REFRIGERATION

All Rights Reserved

Copyright ©2014 International Institute of Ammonia Refrigeration. All Rights Reserved Page i

Foreword (Informative)

This document is a standard for the safe design of closed-circuit ammonia refrigeration systems. The

safety focus is on persons and property located at or near the premises where the refrigeration systems

are located. Additional precautions may be necessary because of particular circumstances, project

specifications or other jurisdictional considerations. This standard is not intended to serve as a

comprehensive technical design manual and shall not be used as such.

Experience shows that ammonia is very stable under normal conditions and rarely ignites when a release

occurs because the flammability range in air is narrow and the minimum flammable concentration in air

is very high as compared to other ignitable gases. Ammonia has a published flammability range of

160,000 ppm to 250,000 ppm. This concentration far exceeds ammonia’s odor detection threshold and

the 50 ppm permissible exposure limit (PEL) published by OSHA.

Ammonia’s strong odor alerts those nearby to its presence at levels well below those that present either

flammability or health hazards. This “self-alarming” odor is so strong that a person is unlikely to

voluntarily remain in an area where ammonia concentrations are hazardous.

The principal hazard to persons is ammonia vapor, since exposure occurs more readily by inhalation

than by other routes. As with any hazardous vapor, adequate ventilation will dilute the vapor and greatly

reduce exposure risk.

Ammonia in vapor form is lighter than air. Typically, ammonia vapor rises and diffuses simultaneously

when released into the atmosphere. It is biodegradable, and when released, it combines readily with

water and/or carbon dioxide to form relatively harmless compounds. Ammonia may also neutralize

acidic pollutants in the atmosphere. Additional information regarding the properties of ammonia is

published in the IIAR Ammonia Data Book.

This standard was first issued in March of 1974 by the International Institute of Ammonia Refrigeration

(IIAR) as IIAR 74-2. The standard was first approved as an American National Standard by the

American National Standards Institute (ANSI) in March 1978 as ANSI/IIAR 74−2−1978. A revision of

the standard, ANSI/IIAR 2−1984 was approved by ANSI in July 1985, as were subsequent revisions in

December 1992, August 1999, October 2005, June 2008, August 2010, and December, 2012.

This standard was prepared using the ANSI Consensus Method; whereby, organizations and individuals

recognized as having interest in the subject of the standard were contacted prior to the approval of this

revision for participation on the Consensus Body and in public reviews. The standard was prepared and

approved for submittal to ANSI by the IIAR Standards Committee and the IIAR Board of Directors.

Copyright ©2014 International Institute of Ammonia Refrigeration. All Rights Reserved Page ii

BSR/IIAR 2-20XX: Changes for this new edition

IIAR 2 has undergone extensive revision since the 2008 (with Addendum B) edition, published

December 3, 2012. Some of the more significant revisions are highlighted here to assist users of this

document. A major focus of changes made to the 2014 edition has been incorporating topics

traditionally addressed in other codes and standards so that IIAR 2 can eventually serve as a single,

comprehensive standard covering safe design of closed-circuit ammonia refrigeration systems. As part

of the update process, a gap analysis was performed that compared information in IIAR 2, ASHRAE

Standard 15 - Safety Standard for Refrigeration Systems, the Uniform Mechanical Code, the NFPA 1

Fire Code, the International Mechanical Code and the International Fire Code.

Where differences were identified, the IIAR 2 rewrite drafting committee either included or revised the

information in this standard, or determined that the information was not necessary to meet minimum

safe design standards for ammonia refrigeration systems. In addition to the changes brought about by the

gap analysis, this standard has been revised to clarify provisions that previously existed in IIAR 2. In

some cases, information previously included in IIAR 2 was deemed unnecessary and was deleted from

the 2014 edition. Additionally, new provisions not previously addressed by any code or standard have

been added based on public proposals or at the recommendation of the rewrite drafting committee.

Some of the major changes to the 2014 edition of IIAR 2 are summarized in the following paragraphs.

However, users of this standard are cautioned that there are many other revisions that can only be

identified and understood by reviewing the standard in its entirety. It should be noted that the title of the

standard has been changed. The new title attempts to convey that the scope of IIAR 2 has been expanded

to include safety topics that were previously unaddressed by the standard. In addition, the standard is

now organized into Parts and Chapters. There are four Parts:

Part 1 - General, includes Chapter 1 through Chapter 3.

Part 2 - Design and Installation Considerations Affecting Construction, includes Chapter 4

through Chapter 7.

Part 3 - Equipment includes Chapter 8 through Chapter 17.

Part 4 - Appendices includes Appendix A through Appendix N.

The Chapter numbers remain sequential, and the four Parts are simply provided as an aid for users in

understanding the layout of chapters in the standard.

Chapter 1 – General, includes sections on Purpose, Scope, and Applicability. The scope now

clarifies that the standard applies only to stationary closed–circuit refrigeration systems.

Chapter 2 – Definitions, has fewer definitions than were included in previous editions. Definitions

that appeared in previous editions that were not changed have been relocated to IIAR 1, Definitions

and Terminology Used in IIAR Standards. New or revised definitions applicable to this standard are

included in Chapter 2. It is intended that, once this standard has been published, definitions for

these new terms will also be relocated to IIAR 1 in a future update.

Chapter 3 – Reference Standards, includes numerous reference standards that have been updated.

References included in Chapter 3 are now limited to those that are mandatory for compliance with

this standard. Informative references are now in Appendix N.

Chapter 4 – Location and Use of Ammonia Refrigeration Machinery, is new. This chapter includes

restrictions on the use of ammonia refrigeration systems, as applicable, based on the occupancy

classification of the area where the system or equipment will be located.

Copyright ©2014 International Institute of Ammonia Refrigeration. All Rights Reserved Page iii

Chapter 5 – System Design, largely retains information that was included in previous editions.

Notable changes include a revision when selecting system design pressures. Requirements that

apply to selecting system design pressures were provided. The minimum low-side and high-side

design pressure is 250 psig; however, individual pieces of equipment might require higher design

pressures. Requirements for the removal of oil from oil pots have been changed such that there is no

longer a requirement to temporarily install a rigid-piped connection. Direction for the provision of

maintenance and functional testing was added. Information on field leak tests has been removed,

and a reference to IIAR 5 was added in its place. Minimum valve tagging standards for system

emergency shut-down procedures have been added, as well as a section on equipment enclosures.

Chapter 6 – Machinery Rooms, largely retains information that was included in previous editions.

Notable changes have been made to alarm and detection requirements. Ventilation requirements

have been modified and ventilation alternatives have been added. A section on ventilation

requirements for systems located outdoors, which are sometimes partially or fully enclosed, has

been added, as has a section regulating site considerations. Changes have been made to the

requirements for eyewash/safety showers to harmonize the standard with OSHA and ANSI/ISEA

requirements. Also, there is a new allowance for machinery rooms that do not exceed 500 square

feet in floor area to not require a direct means of egress to the outside, which will accommodate

small machinery rooms supporting process equipment to be located close to that equipment.

Chapter 7 – Areas Other than Machinery Rooms, is new material. Previously, regulations

concerning certain types of refrigeration equipment located in areas other than machinery rooms

have not been provided. For example, in industrial occupancies, it is often necessary to have

evaporators located outside of a machinery room in storage and production areas. This chapter

provides minimum safety requirements for locating refrigeration equipment in areas other than

machinery rooms, but only where allowed by Chapter 4.

Chapters in Part 3 – Equipment, primarily cover major equipment categories, with one chapter for

each category. Most of the information has been retained from previous editions.

Chapter 8 – Compressors, includes a notable change specifying a ¾-inch minimum size for relief

connections.

Chapter 9 – Refrigerant Pumps, provides requirements for refrigerant pumps, which are different

from those that are specified for compressors.

Chapter 10 – Condensers, includes a significant change establishing that the minimum design

pressure for condensers is now 250 psig. This is consistent with the minimum design pressure

requirement for all high-side equipment. However, higher pressure might be required based on

environmental conditions.

Chapter 11 – Evaporators, includes a significant change establishing that the minimum design

pressure for evaporators is now 250 psig, or alternatively, the high-side design pressure if hot gas is

used to defrost the evaporator. New sections on scraped (swept) surface heat exchangers and

jacketed tanks have been added.

Chapter 12 – Pressure Vessels, provides minimum design pressure requirements that are consistent

with those described above. In addition, like Chapter 8, the chapter establishes that the minimum

size for a relief connection is ¾-inch for vessels that are over 6 inches in diameter and 1 inch for

vessels that are 10 cubic feet or larger.

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Chapter 13 – Piping, includes requirements for piping, tubing, fittings, flanges, valves and

strainers.

Chapter 14 – Packaged Systems and Equipment, covers a new topic. This chapter was added in

recognition of a need for regulations related to pre-assembled systems, subsystems and equipment,

which are becoming increasingly common.

Chapter 15 – Overpressure Protection Devices, is expanded versus previous editions. The chapter

includes methods for evaluating and designing for worst-case scenarios to avoid over-pressurizing

equipment. Direction regarding pressure relief piping termination has been added to address

adjacent roofs in the vicinity of the relief termination. Further, requirements for termination of relief

piping above evaporative condensers have been clarified. An option addressing the voluntary use of

diffusion tanks has also been included, and requirements for hydrostatic overpressure protection

have been clarified. Also, Appendix A of previous editions has been relocated to the body of the

standard in Section 15.5.1.1.1. Given that the prior edition’s appendix was normative, compliance

was mandatory in all cases, so there was no reason for this material to be in an appendix versus

being located in the body of the main standard. As compared to previous editions, provisions for

venting have been modified by deleting the single-relief vent line sizing tables. The size of relief

vents must now always be calculated using the formula provided.

Chapter 16 – Instrumentation and Controls, includes clarified requirements for automated controls

and their functionality.

Chapter 17 – Ammonia Detection and Alarms, establishes the requirements for detection and

system response functions. This chapter standardizes requirements that have historically varied

depending on jurisdiction, designer, contractor, supplier and end-user interpretations.

Informative Appendix A has been added to provide explanatory information related to provisions

in the standard. Sections of the standard that have associated explanatory information are marked

with an asterisk “*” after the section number, and the associated appendix information is located in

Appendix A with a corresponding section number preceded by “A.”

Informative Appendix B has been revised to cover methodologies for calculating relief valve

capacity for various heat exchangers. The former Appendix B, Minimum Values of Design Pressure

and Leak Test Pressure, has been removed. Design pressure information can now be found in the

main body of this standard. Leak pressure information can now be found in IIAR 5, Start-up and

Commissioning of Closed-Circuit Ammonia Refrigeration Systems.

Information pertaining to insulation found in prior editions of this standard has been relocated to

IIAR 4, Installation of Closed-Circuit Ammonia Mechanical Refrigeration Systems.

Information pertaining to purging found in prior editions of this standard has been relocated to

IIAR 5, Start-up and Commissioning of Closed-Circuit Ammonia Refrigeration Systems.

Appendix K provides guidance on calculating ventilation rates for newly-recognized alternative

ventilation methods.

Appendix L includes guidance information on pipe, fittings, flanges, and bolting that have been

commonly used historically in ammonia industrial refrigeration systems.

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Appendix M provides guidance on operational containment as an optional but uncommon

alternative to the traditional ventilation approach to release incidents.

Appendix N includes non-mandatory references, which were relocated out of the main body of the

Standard. Appendix N of the previous edition, dealing with guidance related to site considerations,

has been deleted.

At the time of publication of this edition of the standard, the IIAR Standards Committee included the

following members:

Robert J. Czarnecki, Chair - Campbell Soup Company

Don Faust, Vice Chair - Gartner Refrigeration & Mfg., Inc.

Eric Brown - ALTA Refrigeration, Inc.

Dennis R. Carroll - Johnson Controls

Eric Johnston - ConAgra Foods, Inc.

Gregory P. Klidonas - GEA Refrigeration North America, Inc.

Thomas A. Leighty - Freije-RSC

Brian Marriott - Marriott and Associates

Rich Merrill - Retired, EVAPCO, Inc.

Ron Worley - Nestlé USA

Trevor Hegg - EVAPCO, Inc.

Joseph Pillis - Johnson Controls

Dave Schaefer - Bassett Mechanical, Inc.

Peter Jordan - MDB Risk Management Services, Inc.

John Collins - Zero Zone, Inc.

The subcommittee responsible for rewriting this standard had the following members at the time of

publication:

Thomas A. Leighty, Subcommittee Chair – Freije-RSC

Dave Schaefer, Subcommittee Vice Chair - Bassett Mechanical, Inc.

Trevor Hegg - EVAPCO, Inc.

Don Faust - Gartner Refrigeration & Mfg., Inc.

Peter Jordan - MDB Risk Management Services, Inc.

Glen Heron - Tyson Foods, Inc.

Eric Johnston - ConAgra Foods, Inc.

John Collins - Zero Zone, Inc.

Carl Burris - Tyson Foods, Inc.

Robert A. Sterling - Sterling Andrews Engineering, P.L.

Luke Facemyer - Stellar

Eric Smith - IIAR Staff

Tony Lundell - IIAR Staff

Copyright ©2014 International Institute of Ammonia Refrigeration. All Rights Reserved Page vi

Contents

Notes on the Standard Text ........................................................................................................................................ i

Metric Policy .............................................................................................................................................................. i

Normative/Informative Elements ............................................................................................................................... i

Notice ......................................................................................................................................................................... i

BSR/IIAR 2-20XX: Changes for this new edition .................................................................................................... ii

Contents .................................................................................................................................................................... vi

Part 1 General .......................................................................................................................................1

Chapter 1. Purpose, Scope and Applicability ..............................................................................................1

1.1 Purpose. ......................................................................................................................................1

1.2 *Scope. .......................................................................................................................................1

1.3 Applicability ...............................................................................................................................1

Chapter 2. Definitions .................................................................................................................................2

2.1 General. ......................................................................................................................................2

2.2 *Defined Terms. .........................................................................................................................2

Chapter 3. Reference Standards ..................................................................................................................5

3.1 American Society of Mechanical Engineers (ASME), ...............................................................5

3.2 American Society of Testing and Materials (ASTM), ................................................................5

3.3 Compressed Gas Association (CGA), ........................................................................................5

3.4 International Institute of Ammonia Refrigeration (IIAR), .........................................................5

3.5 International Safety Equipment Association (ISEA), .................................................................5

3.6 National Fire Protection Association (NFPA), ...........................................................................5

3.7 Occupational Safety and Health Administration (OSHA), U.S. Department of Labor, .............5

Part 2 Design and Installation Considerations Affecting Construction ................................................6

Chapter 4. Location of Ammonia Refrigeration Machinery .......................................................................6

4.1 General. ......................................................................................................................................6

4.2 *Permissible Equipment Locations. ...........................................................................................6

Chapter 5. General System Design Requirements .......................................................................................7

5.1 General. ......................................................................................................................................7

5.2 Anhydrous Ammonia Specifications ..........................................................................................7

5.3 Machinery location. ....................................................................................................................7

5.4 *Volume Calculation for Determining Concentration of an Ammonia Release. .......................7

5.5 Use of Ammonia Refrigeration with Secondary Coolants. ........................................................8

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5.6 *System Design Pressure. ...........................................................................................................8

5.7 System Design Temperature. ....................................................................................................10

5.8 Materials ...................................................................................................................................10

5.9 *Purging. ..................................................................................................................................10

5.10 Oil Management .......................................................................................................................10

5.11 Insulation ..................................................................................................................................11

5.12 Condensation Control for Piping and Fittings. .........................................................................11

5.13 Foundations, Piping, Tubing, and Equipment Supports ...........................................................11

5.14 Service Provisions ....................................................................................................................12

5.15 Testing ......................................................................................................................................12

5.16 Signage, Labels, Pipe Marking and Wind Indicators ...............................................................13

5.17 Emergency Shutdown Documentation. ....................................................................................15

5.18 Equipment Enclosures ..............................................................................................................15

5.19 General Safety Requirements ...................................................................................................15

Chapter 6. Machinery Rooms ....................................................................................................................16

6.1 General. ....................................................................................................................................16

6.2 Construction. ............................................................................................................................16

6.3 Access and Egress ....................................................................................................................16

6.4 Combustible Materials. .............................................................................................................17

6.5 Open Flames and Hot Surfaces.................................................................................................17

6.6 Piping ........................................................................................................................................17

6.7 Eyewash/Safety Shower ...........................................................................................................18

6.8 Electrical Safety ........................................................................................................................18

6.9 Drains .......................................................................................................................................19

6.10 Entrances and Exits ..................................................................................................................19

6.11 Lighting ....................................................................................................................................20

6.12 Emergency Control Switches. ..................................................................................................20

6.13 Ammonia Detection and Alarm ................................................................................................20

6.14 Ventilation ................................................................................................................................21

6.15 Signage. ....................................................................................................................................24

Chapter 7. Refrigeration Equipment Located in Areas Other Than Machinery Rooms ............................25

7.1 General. ....................................................................................................................................25

7.2 Requirements for Non-machinery Room Spaces. ....................................................................25

7.3 Ventilation ................................................................................................................................26

Part 3 Equipment ................................................................................................................................28

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Chapter 8. Compressors.............................................................................................................................28

8.1 General. ....................................................................................................................................28

8.2 Design Pressure. .......................................................................................................................28

8.3 Positive-Displacement Compressor Protection ........................................................................28

8.4 Procedures/Testing. ..................................................................................................................29

8.5 Equipment Identification ..........................................................................................................29

8.6 Compressor Installation. ...........................................................................................................29

Chapter 9. Refrigerant Pumps ...................................................................................................................31

9.1 General. ....................................................................................................................................31

9.2 Design .......................................................................................................................................31


9.4 Equipment Identification. .........................................................................................................31

Chapter 10. Condensers ...............................................................................................................................33

10.1 *General. ..................................................................................................................................33

10.2 Air-Cooled Condensers and Air-Cooled De-superheaters. .......................................................33

10.3 Evaporative Condensers. ..........................................................................................................34

10.4 Shell-and-Tube Condensers. .....................................................................................................35

10.5 Plate Heat Exchanger Condensers. ...........................................................................................36

10.6 Double-Pipe Condensers. .........................................................................................................38

Chapter 11. Evaporators ..............................................................................................................................40

11.1 General. ....................................................................................................................................40

11.2 Forced-Air Evaporator Coils ....................................................................................................40

11.3 Shell-and-Tube Evaporators .....................................................................................................41

11.4 Plate Heat Exchanger Evaporators. ..........................................................................................43

11.5 Scraped (Swept) Surface Heat Exchangers. .............................................................................44

11.6 Jacketed Tanks. .........................................................................................................................45

Chapter 12. Pressure Vessels .......................................................................................................................47

12.1 General. ....................................................................................................................................47

12.2 Design .......................................................................................................................................47


12.4 Equipment Identification ..........................................................................................................48

12.5 Pressure Vessel Installation Considerations. ............................................................................49

Chapter 13. Piping .......................................................................................................................................50

13.1 *General. ..................................................................................................................................50

13.2 Pipe, Tubing, Fittings, and Flanges ..........................................................................................50

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13.3 *Refrigerant Valves and Strainers. ...........................................................................................51

13.4 *Piping, Hangers, Supports Isolation .......................................................................................52

13.5 *Location of Refrigerant Piping ...............................................................................................53

Chapter 14. Packaged Systems and Equipment...........................................................................................54

14.1 General .....................................................................................................................................54

14.2 Design .......................................................................................................................................54

14.3 Fabrication ................................................................................................................................55

14.4 Alarms and Detection. ..............................................................................................................55

Chapter 15. Overpressure Protection Devices .............................................................................................56

15.1 *General. .................................................................................................................................56

15.2 *Pressure Relief Devices ..........................................................................................................56

15.3 Pressure Relief Protection ........................................................................................................57

15.4 Pressure Relief Device Piping. .................................................................................................62

15.5 Discharge from Pressure Relief Devices ..................................................................................63

15.6 Equipment and Piping Hydrostatic Overpressure Protection ...................................................66

Chapter 16. Instrumentation and Controls ...................................................................................................68

16.1 General .....................................................................................................................................68

16.2 Visual Liquid Level Indicators: ................................................................................................68

16.3 *Electric and Pneumatic Sensor Controls.................................................................................69

Chapter 17. Ammonia Detection and Alarms .............................................................................................70

17.1 Scope. .......................................................................................................................................70

17.2 Power for Detectors and Alarms...............................................................................................70

17.3 Testing ......................................................................................................................................70

17.4 Detector Placement. ..................................................................................................................70

17.5 *Alarms. ...................................................................................................................................70

17.6 Signage. ....................................................................................................................................70

17.7 Detection and Alarm Levels. ....................................................................................................70

Part 4 Appendices...............................................................................................................................72

Appendix A. (Informative) Explanatory Material ..........................................................................................72

Appendix B. (Informative) Ammonia Characteristics and Properties ...........................................................82

Appendix C. (Informative) Methods for Calculating Relief Valve Capacity for Heat Exchanger Internal

Loads ........................................................................................................................................84

Appendix D. (Informative) Duplicate Nameplates on Pressure Vessels ........................................................92

Appendix E. (Informative) Method for Calculating Discharge Capacity of a Positive Displacement

Compressor Pressure Relief Device .........................................................................................93

Appendix F. (Informative) Pipe Hanger Spacing, Hanger Rod Sizing, and Loading ...................................95

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Appendix G. (Informative) Hydrostatic Overpressure Relief ........................................................................97

Appendix H. (Informative) Stress Corrosion Cracking ................................................................................105

Appendix I. (Informative) Emergency Pressure Control Systems..............................................................107

Appendix J. (Informative) Machine Room Signs .......................................................................................112

Appendix K. (Informative) Alternative Ventilation Calculation Methods ..................................................116

Appendix L. (Informative) Pipe, Fittings, Flanges, and Bolting .................................................................120

Appendix M. (Informative) Operational Containment .................................................................................122

Appendix N. (Informative) References and Sources of References .............................................................123

Copyright ©2014 International Institute of Ammonia Refrigeration. All Rights Reserved Page 1

Part 1 General

Chapter 1. Purpose, Scope and Applicability

1.1 Purpose. This standard specifies minimum requirements for the safe design of closed-circuit

ammonia refrigeration systems.

1.2 *Scope. Stationary closed-circuit refrigeration systems utilizing ammonia as the refrigerant shall

comply with this standard. This standard shall not apply to:

1. Ammonia absorption refrigeration systems.

2. Replacements of machinery, equipment or piping with functionally equivalents.

3. Equipment and systems and the buildings or facilities in which they are installed that existed

prior to the legal effective date of this standard. Such equipment, systems and buildings and

facilities shall be maintained in accordance with regulations that applied at the time of

installation or construction.

1.3 Applicability

1.3.1 Conflicts. Where there is a conflict between this standard and the Building Code, Fire Code,

Mechanical Code or Electrical Code, the Code requirements shall take precedence over this

Standard unless otherwise stated in such Code.

1.3.2 Alternative Materials and Methods. The AHJ is authorized to approve the use of devices,

materials or methods not prescribed by this standard as an alternative means of compliance,

provided that any such alternative has been shown to be equivalent in quality, strength,

effectiveness, durability and safety.

1.3.3 *Installations in Locations Without an AHJ. Where a system is installed in a jurisdiction

without an AHJ, the designer is authorized to specify an alternative, and the alternative shall

be documented in the design documents.


Chapter 2. Definitions

2.1 General. Definitions shall be in accordance with this chapter and ANSI/IIAR-1.

2.2 *Defined Terms. The following words and terms, which are used in this standard, shall be defined

as specified in this chapter.

AHJ (Authority Having Jurisdiction): The organization, office, or individual responsible for enforcing

the requirements of this standard, or for approving equipment, materials, an installation, or a procedure.

Authorized Personnel: Persons who have been specifically granted permission to enter a restricted

area.

Building Code: The building code adopted by the jurisdiction.

Building Opening: A permanent or operable area that allows outdoor air into the building envelope

including operable doors (e.g. swinging doors, slide doors, roll-up doors, fire doors, access hatches),

operable make-up air intakes (where the intakes are not equipped with the ability to close automatically

when ammonia is present), and other vents with a permanent opening.

Combustible: A material that does not meet the definition of noncombustible material.

*Commercial Occupancy: A premises or portion thereof where people transact business, receive

personal service, or purchase food or other goods.

Double-Indirect Open-Spray System: A system in which the secondary substance for an indirect open

spray system is heated or cooled by the secondary coolant from a second enclosure.

Electrical Code: The electrical code adopted by the jurisdiction.

Equipment: An assembly, subassembly, accessory or component of a refrigeration system.

Equipment Enclosure: An enclosure designed to house refrigeration equipment and devices associated

with a closed-circuit refrigeration system, or both, that is not intended for occupancy.

Fire Code: The fire code adopted by the jurisdiction.

Indicating Device: An instrument that measures and registers certain operating conditions used for

monitoring and control, such as temperatures and pressures, which can be read on a gauge, control

display screen, or both.

Indirect System: A system in which a secondary coolant that is cooled or heated by the refrigeration

system is circulated to the air or other substance to be cooled or heated.

Indirect-Closed System: A system in which a secondary coolant passes through a closed circuit in the

air or other substance to be cooled or heated.

Indirect Open-Spray System: A system in which a secondary coolant is in direct contact with the air or

other substance to be cooled or heated.


Industrial Occupancy: A premises or a portion thereof that is not open to the public, where access is

controlled such that only authorized personnel are admitted and that is used to manufacture, process, or

store goods.

Large Mercantile Occupancy: A premises or portion thereof where more than 100 persons congregate

to purchase merchandise.

Machinery: Refrigeration equipment forming a portion of a refrigeration system, including but not

limited to compressors, condensers, pressure vessels, evaporators and refrigerant pumps.

Machinery Room: An enclosed space that, where required by this standard to contain equipment, must

comply with the requirements set forth in Chapter 6.

Mechanical Code: The mechanical code adopted by the jurisdiction.

Monitored: A means of continuous oversight, such as notification of on-site staff, a third party alarm

service or a responsible party.

Noncombustible Material: A material that, when tested in accordance with ASTM E136, has at least

three of four specimens tested meeting all of the following criteria:

1. The recorded temperature of the surface and interior thermocouples shall not at any time during

the test rise more than 54°F (30°C) above the furnace temperature at the beginning of the test.

2. There shall not be flaming from the specimen after the first 30 seconds.

3. If the weight loss of the specimen during testing exceeds 50 percent, the recorded temperature of

the surface and interior thermocouples shall not at any time during the test rise above the furnace

air temperature at the beginning of the test, and there shall not be flaming of the specimen.

Occupied Space: A portion of a premises that is routinely accessible to or occupied by people on a part-

time or full-time basis.

*Packaged System: A fabricated and assembled self-contained closed-circuit refrigeration system, or a

large portion thereof, either enclosed within its case or framework or unenclosed.

PPM: Parts per million concentration in air.

Principal Machinery Room Door: An exterior door that has been designated as a primary emergency

egress door for a machinery room.

*Public Assembly Occupancy: A premises portion thereof where large numbers of people congregate

and from which occupants cannot quickly vacate.

Restricted: Open to access by only authorized personnel and specifically excluding public access.

Self-Contained: Having all essential equipment, piping and devices to form a complete closed-circuit

mechanical refrigeration system, except energy and control connections, and contained in a case or

framework.


Surge Drum: A receiver installed on the low-pressure side of a refrigeration system that is close-

coupled to one or more evaporators and provides liquid feed and a liquid-from-vapor disengagement

space to ensure that dry vapor is returned to the compressor.

Tight Construction: Solid construction with holes or openings that are either sealed or provided with

tight-fitting doors to control the transfer of liquid, moisture, air and vapor.

Tight-Fitting Door: A tightly constructed door with seals to minimize gap clearances between the entire

door perimeter and its fixed door frame, which is intended to control the transfer of liquid, moisture, air

and vapor.

Trained Operator: An individual having training and experience, which qualify that individual to

operate and perform basic system inspections on a closed-circuit refrigeration system with which he or

she has become familiar.

Unoccupied Area: A portion of premises accessible to only authorized personnel performing scheduled

walk-throughs for operational checks or maintenance service on equipment.


Chapter 3. Reference Standards

3.1 American Society of Mechanical Engineers (ASME), standards as follows:

ASME B&PVC, Boiler and Pressure Vessel Code, Pressure Vessels, Section VIII, Division 1

(2013).

ASME B31.5 (2013), Refrigeration Piping and Heat Transfer Components.

3.2 American Society of Testing and Materials (ASTM), standards as follows:

ASTM A53/A53M (2012), Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-

Coated, Welded and Seamless.

ASTM A197/A197M-00 (2011), Standard Specification for Cupola Malleable Iron.

ASTM E136 (2012), Standard Test Method for Behavior of Materials in a Vertical Tube Furnace

at (750°C).

3.3 Compressed Gas Association (CGA), Standard G-2 (1995), Eighth Edition.

3.4 International Institute of Ammonia Refrigeration (IIAR), standards as follows:

ANSI/IIAR 1 (2012), Definitions and Terminology Used in IIAR Standards.

ANSI/IIAR 3 (2012), Ammonia Refrigeration Valves.

ANSI/IIAR 5 (2013), Start-up and Commissioning of Closed-Circuit Ammonia Refrigeration

Systems.

ANSI/IIAR 7 (2013), Developing Standard Operating Procedures for Closed-Circuit Ammonia

Mechanical Refrigerating Systems.

3.5 International Safety Equipment Association (ISEA), ANSI/ISEA Z358.1, World Safety

Standard for Emergency Eyewash and Shower Equipment (2009).

3.6 National Fire Protection Association (NFPA), NFPA Standard 70, National Electrical Code

(NEC) (2011).

3.7 Occupational Safety and Health Administration (OSHA), U.S. Department of Labor, regulations as follows:

29 CFR 1910.212 (2012), General Requirements for All Machines.

29 CFR 1910.219 (2012) Mechanical Power Transmission Apparatus.


Part 2 Design and Installation Considerations Affecting Construction

Chapter 4. Location of Ammonia Refrigeration Machinery

4.1 General. The location of ammonia refrigeration machinery shall comply with this chapter.

Ammonia refrigeration machinery located in a machinery room complying with Chapter 6 or

located outdoors in accordance with Section 4.2.2 shall be permitted in conjunction with a

secondary coolant that serves any occupancy in accordance with Section 5.5.

4.2 *Permissible Equipment Locations. Ammonia refrigeration machinery shall be located in a

machinery room complying with Chapter 6 unless otherwise permitted by this section.

4.2.1 Listed Equipment. Listed equipment containing not more than 6.6 lbs (3 kg) of ammonia

and installed in accordance with the listing and the manufacturer’s instructions shall be

permitted in any occupancy without a machinery room.

4.2.2 Outdoor Installations. Ammonia refrigeration machinery shall be permitted to be installed

outdoors. Ammonia refrigeration machinery, other than piping, installed outdoors shall be

located not less than 20 feet from building openings, except for openings to a machinery

room or openings to an industrial occupancy complying with Section 7.2.

4.2.3 *Industrial Occupancies. The following ammonia refrigeration machinery shall be

permitted to be installed outside of a machinery room in industrial occupancies complying

with Chapter 7.

1. Evaporators used for refrigeration or dehumidification.

2. Condensers used for heating the space in which they are located.

3. Valves, including but not limited to control and pressure-relief valves, and connecting

piping, any of which are associated with Items 1 and 2.

4. An ammonia refrigeration system or portions thereof with a total connected compressor

power not exceeding 100 HP (74.6 kW).

4.2.4 *Public Assembly, Commercial and Large Mercantile Occupancies. Where approved,

ammonia refrigeration machinery shall be permitted outside of a machinery room for

applications other than human comfort in a public assembly occupancy, commercial

occupancy or large mercantile occupancy. The quantity of ammonia shall be limited such

that a complete discharge from any independent refrigerant circuit will not result in an

ammonia concentration exceeding 320 ppm in any room or area where equipment containing

ammonia is located. The calculation procedure for determining the concentration level shall

comply with Section 5.4.


Chapter 5. General System Design Requirements

5.1 General. The design of closed-circuit ammonia refrigeration systems shall comply with this

chapter.

5.2 Anhydrous Ammonia Specifications

5.2.1 *Refrigerant-Grade Ammonia. Refrigerant-grade anhydrous ammonia that meets or

exceeds the minimum requirements of CGA Standard G-2 shall be used for the initial charge

and subsequent top-off to fill the system to the operating intended inventory.

5.2.2 Purity Requirements. Ammonia refrigerant shall comply with Table 5.2.

Table 5.2

Purity Requirements

Ammonia Content 99.95% minimum

Non-Basic Gas in Vapor Phase 25 ppm maximum

Non-Basic Gas in Liquid Phase 10 ppm maximum

Water 33 ppm maximum

Oil (as soluble in petroleum ether) 2 ppm maximum

Salt (calculated as NaCl) None

Pyridine, Hydrogen Sulfide, Naphthalene None

5.3 Machinery location. The location of ammonia refrigeration machinery shall comply with Chapter 4.

5.4 *Volume Calculation for Determining Concentration of an Ammonia Release. For the purpose

of applying Section 4.2.4 and Section 7.3.1.2, the volume used to calculate the potential ammonia

concentration in the event of a release shall comply with this section. The volume used to calculate

the potential ammonia concentration shall be the gross volume of a room or space into which

released ammonia will disperse based on the smallest gross volume in which the release could

accumulate.

5.4.1 *Wall Openings Permanent wall openings between rooms or spaces containing a

refrigeration system, or equipment, shall not be considered when determining the volume.

EXCEPTION: Where the designer determines, based on the size and elevation of

permanent wall openings or a mechanical ventilation system, that migration

and dilution of a release over the combined spaces will occur, the volume

shall be the combined space, provided that the openings or mechanical

ventilation are clearly identified as the basis for the design analysis.

5.4.2 Spaces Above Suspended Ceilings. The space above a suspended ceiling shall not be used

in determining the volume of the area in which the ceiling is located unless the space above

the ceiling is used as part of the air distribution system.


5.4.3 *Interconnected Floor Levels and Mezzanines. Where a refrigeration system, or portion

thereof, is located in a room or space containing multiple floor levels connected through an

open atrium or where there is a mezzanine open to a room or space, the combined volume of

interconnected floors and mezzanines shall be used.

5.4.4 *Mechanical Ventilation Considerations. Where a refrigeration system, or portion thereof,

is located: 1) In an area served by a mechanical ventilation system, 2) Within an air handler

or 3) In an air distribution duct system, the volume of the rooms or spaces connected by the

ventilation or duct system, including the volume of the connected supply and return air ducts

and any connecting plenum, shall be used.

EXCEPTION: The smaller of the volumes on either side of a damper shall be used where

portions of the ventilation or duct system are subject to being isolated by

dampers, other than: 1) Fire dampers, 2) Smoke dampers, 3) Combination

fire and smoke dampers, or 4) Dampers that continuously maintain not less

than 10-percent airflow.

5.5 Use of Ammonia Refrigeration with Secondary Coolants. Ammonia refrigeration machinery

located in a machinery room complying with Chapter 6 or outdoors in accordance with Section

4.2.2 shall be permitted to be used in conjunction with a secondary coolant that serves any

occupancy, provided that the system is one of the following types and that use of the secondary

coolant is in accordance with the Mechanical Code:

1. Indirect closed system.

2. Indirect open-spray system with the pressure of the secondary coolant always exceeding

the pressure of the ammonia system, regardless of whether the system is in operation or

standby and considering all temperature conditions to which equipment could be exposed.

3. Double-indirect open-spray system.

5.6 *System Design Pressure. Design pressure shall be in accordance with this section.

5.6.1 General

*Allowance for Pressure-limiting and Pressure-relief Devices. In determining the

design pressure, an allowance shall be provided for setting pressure-limiting devices

and pressure-relief devices to avoid equipment shutdown or loss of ammonia during

normal operation.

Systems Not Exceeding 22 pounds of Ammonia. For systems containing not more

than 22 pounds of ammonia, portions of the system that are protected by a pressure-

relief device shall not be required to have a design pressure that exceeds the set

pressure of the pressure relief protection.

Equipment and Piping Connected to a Pressure Vessel. Equipment and piping

connected to pressure vessels and subject to the same pressure as the pressure vessel

shall have a design pressure that is equal to or greater than the set pressure of the

pressure relief protection for the pressure vessel.


Compressors Used as Boosters. Compressors used as boosters and discharging into

the suction side of another compressor shall be considered as part of the low-pressure

side for the purpose of determining the design pressure.

Connecting to Existing Low-pressure Equipment. Where new low-pressure side

equipment is connected to an existing system that was in operation prior to the

adoption of this Standard, the design pressure of the new low-pressure-side portion of

the system shall be permitted to equal the design pressure of the existing low-pressure

side, provided that the new low-pressure side operates under the same conditions as

the existing system.

5.6.2 Pressure Developed During Operation, Standby or Shipping Conditions. The design

pressure shall be equal to or greater than the maximum pressure that could occur during

operating, standby or shipping conditions.

Normal Operating Conditions. The design pressure shall be equal to or greater than

the maximum pressures that could occur during normal operating conditions,

including conditions created by expected fouling of heat exchange surfaces.

*Standby Conditions. The design pressure shall be equal to or greater than the

maximum pressure that could occur during standby conditions, which shall include

conditions that can normally occur when the system is not in operation. For low-

pressure side equipment, the design pressure shall be equal to or greater than the

pressure developed in the low-pressure side of the system from equalization or heating

due to changes in ambient temperature after a system has stopped.

Shipping. The design pressure for both low-pressure side and high-pressure side

equipment that is shipped as part of a gas- or ammonia-charged system shall equal or

exceed the maximum internal pressures associated the highest anticipated temperature

exposure during shipment.

5.6.3 Saturation Pressure and Minimum Permissible Design Pressure. The design pressure

shall not be less than the saturation gauge pressure corresponding to the following

temperatures and shall not be less than the specified minimum.

1. Low pressure side: 10°F (5.6°C) greater than the 1% ambient dry bulb temperature for

the installation location or 114.6°F (45.9°C), whichever is greater. The minimum design

pressure shall be 250 psig (1724 kPa).

2. High-pressure side of water-cooled or evaporatively-cooled systems: 30°F (16.7°C)

higher than the highest summer 1% wet-bulb temperature for the location, 15°F (8.3°C)

higher than the highest “design leaving condensing-water temperature” for which the

equipment is designed, or 114.6°F (45.9°C), whichever is greater. The minimum design

pressure shall be 250 psig (1724 kPa).

3. High-pressure side of air-cooled systems: 30°F (16.7°C) higher than the highest

summer 1% design dry-bulb temperature for the location, but not less than 122°F

(50°C). The minimum design pressure shall be 250 psig (1724 kPa).

5.6.4 Vacuum. Refrigeration equipment shall be designed for a vacuum of 29.0 inches (737 mm)

of mercury.


5.7 System Design Temperature. Equipment shall be designed to operate within the full range of

temperatures associated with the system design and for the full range of ambient temperatures to

which equipment will be exposed at the installation location.

5.8 Materials

5.8.1 General

Materials used in the construction of an ammonia refrigeration system shall be suitable

for ammonia refrigerant at the coincident temperature and pressure to which the

system will be subjected.

*Materials that deteriorate in the presence of ammonia, refrigerant lubricating oil, a

combination of both, or any expected contaminant shall not be used.

5.8.2 Metallic Materials

Cast iron, malleable iron, nodular iron, steel, cast steel, and alloy steel shall be

permitted in accordance with ASME B31.5 or ASME B&PVC, Section VIII,

Division 1, or international equivalent as applicable. Other metallic materials,

including but not limited to aluminum, aluminum alloys, lead, tin, and lead-tin alloys

shall be permitted in accordance with Section 5.8.1. Where tin and tin-lead alloys are

used, the alloy composition shall be verified as suitable for temperature exposures, as

specified in Section 5.7.

Zinc, copper, and copper alloys shall not be used to contain or be in contact with

ammonia. Copper-containing anti-seize and lubricating compounds shall not be used.

Copper, as a component of brass alloys, shall be permitted in rotating shaft bearings

and other non-refrigerant containment uses.

5.8.3 Non-Metallic Materials

Non-metallic materials shall be permitted in accordance with Section 5.8.1.

Non-metallic materials shall be permitted in accordance with ASME B31.5 or ASME

B&PVC, Section VIII, Division 1, or international equivalent as applicable.

5.9 *Purging. Means shall be provided to remove air and other non-condensable gases from the

refrigeration system. Atmospheric discharge from vents shall comply with Section 15.5.1.

5.10 Oil Management

5.10.1 General. Provisions shall be made in the design for removing oil from locations in piping

and equipment where oil accumulation is expected.

5.10.2 Compressors. Compressor packages shall have a means to sample oil for periodic oil

analysis in accordance with the manufacturer’s recommendations.


5.10.3 Oil Removal. Oil removal shall be accomplished by one or more of the following:

1. A rigid-piped oil return system.

2. A vessel equipped with an oil drain valve in series with a self-closing emergency stop valve.

3. Piping which provides the capability to isolate and remove ammonia to another portion of the

system.

4. A valve and piping assembly at the draining point where oil is removed from the system. At a

minimum, an oil drain valve in series with a self-closing emergency stop valve is required.

5.10.4 Temporary Piping. Where draining of oil requires the use of temporarily-attached rigid

piping, such piping shall be supported and shall have tight connections.

5.11 Insulation

5.11.1 *General. Equipment surfaces, not intended for heat exchange, shall be insulated to prevent

or control condensation. See Section 5.12 for condensation control for piping and fittings.

EXCEPTIONS: 1. Valve groups and other equipment shall be permitted to be

uninsulated where necessary for service access provided that the vapor

retarder is sealed to the piping or equipment where insulation of

adjoining piping terminates.

2. Piping and fittings constructed of corrosion-resistant materials or

protected with a corrosion-resistant treatment shall be permitted to be

uninsulated if they are routinely defrosted or are otherwise managed to

limit ice accumulation. Where defrost will be the method of ice

control, a means to control and drain condensate shall be provided.

5.11.2 Hot Discharge Lines. Hot discharge lines having an external surface temperature of 140

degrees F (60 degrees C) or higher and are located less than 7.25 feet (2.2 m) above the floor

or are located adjacent to passageways, aisles, walkover stairs or landings shall be provided

with: 1) Warning signs, 2) Insulation, or 3) Guards to prevent contact.

5.12 Condensation Control for Piping and Fittings. Piping and fittings that convey brine, refrigerant,

or coolants shall be insulated in accordance with Section 5.11, treated, or otherwise protected to

mitigate condensation where, during normal operation, the surface temperature could fall below the

dew point of the surrounding air in an area where condensation could develop and become a hazard

to occupants or cause damage to the structure, electrical equipment or other equipment.

5.13 Foundations, Piping, Tubing, and Equipment Supports

5.13.1 General. Supports and anchorage for refrigeration equipment shall be designed in

accordance with the Building Code.

5.13.2 Combustibility. Structural supports shall be noncombustible. Base supports located on the

roof beneath piping or equipment stands shall be permitted to be constructed with pressure-

treated lumber.

5.13.3 Seismic Joints and Restraints. Seismic joints and restraints shall be provided as required by

the Building Code.


5.13.4 Manufacturers’ Recommendations and Expected Loads. Supports and foundations shall

meet or exceed the manufacturers’ recommendations and shall be designed to carry expected

loads.

5.13.5 Vibration and Movement Resistance. Supports and foundations shall be designed to

prevent excessive vibration or movement of piping, tubing and equipment.

5.14 Service Provisions

5.14.1 *General. Equipment shall be accessible for maintenance, as required by the Mechanical

Code.

5.14.2 Charging Connection Security. Refrigeration system charging connections located outdoors

shall be locked or otherwise restricted to access by only authorized personnel.

5.14.3 *Maintenance and Functional Testing. Design provisions for maintenance and functional

testing of safety controls shall be provided. Such provisions shall be permitted to include but

are not limited to shut-off valves and capped or plugged connection points that comply with

this Standard. Provisions for functional testing shall not require disassembly of ammonia-

containing portions of the system.

5.14.4 Pressure Gauges. Where a pressure gauge is installed on the high-side of the refrigeration

system, the gauge shall be capable of measuring and displaying not less than 120-pecent of

the system design pressure.

5.14.5 *Serviceability. Serviceable equipment shall be designed so that it can be serviced.

5.14.6 *Service Isolation Valves. Serviceable equipment shall have manual isolation valves.

EXCEPTION: Packaged systems and portions of built-up systems shall be permitted

to have pump-down arrangements that provide for the removal or

isolation of ammonia for servicing one or more devices in lieu of

isolation valves.

5.15 Testing

5.15.1 Strength Testing. Equipment containing ammonia shall be strength tested to the minimum

pressure exceeding the design pressure specified in Chapter 8 through Chapter 16,

subsequently leak tested, and proven tight at a pressure not less than the design pressure.


5.15.2 Ultimate Strength. Pressure-containing equipment shall comply with Sections 5.15.2.1 and

5.15.2.2.

EXCEPTION: The following shall be permitted to comply with Section 5.15.2.3 in lieu

of complying with this section:

1. Pressure vessels.

2. Provided that they are not part of a pressure vessel: piping including

valves; evaporators; condensers; and heating coils with ammonia as

the working fluid.

3. Pressure gauges.

4. Refrigerant pumps.

5. Control mechanisms.

Pressure-containing equipment shall be in accordance with one of the following:

1. Listed individually.

2. Listed as part of the complete refrigeration system.

3. Listed as a subassembly.

4. Designed, constructed and assembled to have an ultimate strength sufficient to

withstand three times the design pressure for which it is rated.

5. Designed in accordance with Section VIII, Division 1, ASME B&PVC or

international equivalent, as applicable.

*Secondary coolant sides of equipment exempted from ASME B&PVC, Section VIII,

Division 1, or international equivalent shall be designed, constructed and assembled to

have ultimate strength sufficient to withstand the greater of 150 psig [1724 kPa gauge]

or two times the design pressure for which they are rated.

Equipment designed based on the exception to Section 5.15.2 shall be required to

comply with additional requirements in Chapter 8 through Chapter 16 and ASME

B31.5, as applicable.

5.16 Signage, Labels, Pipe Marking and Wind Indicators

5.16.1 Machinery Room Signage. Machinery room signage shall comply with Section 6.15.

5.16.2 Machinery Labels. Refrigeration machinery shall be provided with permanent labels. For

refrigeration machinery having an internal volume of more than three cubic feet (0.085 cubic

meters) containing ammonia, the permanent label shall include the state of the contained

ammonia, being liquid, vapor, or both; the type of machinery; and a title that matches the

system drawings.

5.16.3 Emergency Shutdown Valve Identification and Tagging. Valves required for emergency

shutdown of the system shall be clearly identified on a diagram that is available to personnel

onsite. The procedures and diagram shall be reviewed and updated, as necessary, when

changes are made that affect emergency shutdown procedures. Valves used for emergency

shutdown of the system shall also be uniquely identified on the actual system.


5.16.4 Nameplates

Equipment shall have a nameplate with minimum data that describes or defines the

manufacturer’s information and design limits and purpose as specified in Chapter 8

through Chapter 16.

*The original nameplate for pressure vessels shall be affixed as specified in ASME

B&PVC, Section VIII, Division 1, Section UG-119(e) or international equivalent.

*Duplicate nameplates shall comply with the following:

1. Where duplicate nameplates are required for pressure vessels and heat

exchangers constructed in accordance with ASME B&PVC, Section VIII,

Division 1or international equivalent, the duplicate nameplate shall comply with

ASME B&PVC, Section VIII, Division 1, Section UG-119(e) or international

equivalent.

2. A duplicate nameplate, if used, shall be installed on the skirt, support, jacket, or

other permanent attachment to a vessel.

3. Duplicate nameplates shall be permanently marked “DUPLICATE.”

4. Duplicate nameplates shall be obtained only from the original equipment

manufacturer or the manufacturer’s assignee.

5. The installer shall certify to the manufacturer that the duplicate nameplate has

been applied to the proper vessel, in accordance with the governing edition of

ASME B&PVC, Section VIII, Division 1 Section UG-119(d) or international

equivalent. The installer shall provide a copy of the certification to the owner,

who shall retain the copy with the U1A form, or equivalent, for the vessel.

5.16.5 *Pipe Marking. Ammonia piping mains, headers and branches shall be identified with the

following information. The marking system shall either be one established by a recognized

model code or standard or one described and documented by the facility owner.

1. “AMMONIA”

2. Physical state of the ammonia, being liquid, vapor, or both.

3. Relative pressure level of ammonia, being low or high as applicable.

4. Name of the pipe, which shall be permitted to be abbreviated.

5. Direction of flow.

5.16.6 *Wind Indicator. Where a sock, pennant or other wind indicator is provided, it shall in

accordance with specifications and locations prescribed by emergency planning documents.


5.17 Emergency Shutdown Documentation. It shall be the duty of the person in charge of the

premises on which the refrigeration system is installed to provide a schematic drawing or sign

giving directions for the emergency shutdown of the system at a location that is readily accessible

to trained refrigeration system staff and trained emergency responders who are familiar with the

system. Schematic drawings or signage shall include the following:

1. Instructions with details and steps for shutting down the system in an emergency.

2. The name and contact telephone numbers of the refrigeration operating, maintenance and

management staff, emergency responders, and safety personnel.

3. The names and telephone numbers of all corporate, local, state, and federal agencies to be

contacted as required in the event of a reportable incident.

4. Type of ammonia in the systems.

5. Type and quantity of lubricants in the systems.

6. Field test pressures applied.

5.18 Equipment Enclosures

5.18.1 General. Enclosures shall be suitable for the installation location and shall be provided with

protection from physical and environmental damage, as required for the installed location.

Where the installation location requires a specified level of cleanliness, the enclosure shall be

designed to meet applicable requirements.

5.18.2 Egress. Operational and maintenance service egress shall be provided by access panels or

doors or the design shall provide for remote service by removal of the enclosure or the

contents from the installed location.

5.19 General Safety Requirements

5.19.1 Protection from Physical Damage. Where installed in a location subject to physical

damage, guarding or barricading shall be provided.

5.19.2 *Rotating Parts. Exposed rotating parts shall be protected with screens or guards in

accordance with OSHA 29 CFR 1910.212 and 29 CFR 1910.219.

5.19.3 Ammonia Storage. Ammonia shall be stored in cylinders or vessels designed for ammonia

containment.

5.19.4 *Used Equipment. Used equipment to be installed in connection with an existing system

shall comply with the requirements of the standard that regulated the installation of the

existing system, including the minimum design pressure. Used equipment to be installed in

connection with a new system shall meet the requirements of this Standard.

5.19.5 *Static and Dynamic Loads. Equipment shall be designed to structurally withstand the

expected static and dynamic loads.

5.19.6 *Illumination of Construction Areas. During construction, illumination shall be available

for outdoor refrigeration equipment work areas.

5.19.7 *Means of Egress. Means of egress shall comply with the Building Code


Chapter 6. Machinery Rooms

6.1 General. Where a machinery room is required by Chapter 4 to contain machinery, the machinery

room shall comply with this chapter.

6.2 Construction. Machinery rooms shall be constructed in accordance with the Building Code and

the requirements of this section.

6.2.1 *Separation and Fire Protection. The machinery room shall be separated from the

remainder of the building by tight-fitting construction having a one-hour fire-resistance

rating. Doors shall comply with Section 6.10.

EXCEPTION: The one-hour fire-resistance rating shall not be required where the

machinery room is equipped with an automatic fire sprinkler system.

Tight fitting construction must still be provided.

6.2.2 Piping Supports. Where piping is supported by the floor, roof or ceiling structure, the

structure or foundation supporting the piping shall be designed to support the expected static

and dynamic loads, including seismic loads. Foundations and supports shall be in accordance

with the Building Code.

6.2.3 Equipment Supports. Foundations, floor slabs, and supports for compressor units and other

equipment located within the machinery room shall be of noncombustible construction and

capable of supporting the expected static and dynamic loads imposed by such units, including

seismic loads. Foundations and supports shall be in accordance with the Building Code.

A compressor or condenser supported from the ground shall rest on a concrete pad or

base or shall be furnished with a support base for setting directly on and anchoring to

the foundation.

6.2.4 Vibration Control. Machinery shall be mounted in a manner that prevents excessive

vibration from being transmitted to the building structure or connected equipment. Isolation

materials shall be permitted between the foundation and equipment.

6.2.5 Airflow from Occupied Spaces. Air shall not flow to or from an occupied space through a

machinery room unless the air is ducted and sealed to prevent ammonia leakage from

entering the airstream. Access doors and panels in ductwork and air-handling units located in

a machinery room shall be gasketed and tight-fitting.

6.3 Access and Egress

6.3.1 General. Equipment installed in machinery rooms shall be located in such a manner as to

allow egress from any part of the room in the event of an emergency, as required by Section

5.19.7, and to provide clearances required for maintenance, operation and inspection

according to manufacturers’ instructions.

6.3.2 Maintenance Access. Maintenance access shall comply with Section 5.14.1.


6.3.3 Access to Valves.

*Manually-operated valves that are inaccessible from floor level shall be operable

from portable platforms, fixed platforms, ladders, or shall be chain-operated.

Manually operated isolation valves identified as being part of the system emergency

shutdown procedure shall be directly operable from the floor or chain-operated from a

permanent work surface. Emergency valve identification shall comply with

Section 5.16.3.

6.3.4 Restricted Access. Access to a machinery room shall be restricted to authorized personnel.

Signage on machinery room doors shall comply with Section 6.15.

6.4 Combustible Materials. Combustible materials shall not be stored in machinery rooms.

EXCEPTION: This provision shall not apply to spare parts, tools and incidental

materials necessary for the operation and maintenance of the

refrigeration system.

6.5 Open Flames and Hot Surfaces. Fuel-burning appliances and equipment and surfaces having

temperatures exceeding 800°F (427°C) shall not be installed in a machinery room.

EXCEPTIONS: 1. Fuel-burning appliances and equipment shall be permitted in a machinery

room where combustion air to the fuel-burning appliance is ducted from

outside of the machinery room and sealed to prevent ammonia leakage from

reaching the combustion chamber.

2. Fuel-burning appliances and equipment shall be permitted in a machinery

room where an ammonia detector automatically shuts off the combustion

process upon detection of ammonia.

3. The use of matches, lighters, sulfur sticks, welding equipment and similar

portable devices shall be permitted except when charging is being performed

and when oil or ammonia is being removed from the system.

4. Internal combustion engines powering compressors shall be permitted in a

machinery room.

6.6 Piping

6.6.1 Insulation. Piping and fittings shall be insulated as required by Section 5.11 and

Section 5.12.

6.6.2 Pipe Penetrations. Pipes penetrating the machinery room separation shall be sealed to the

walls, ceiling, or floor through which they pass in accordance with Section 6.2.1. Where

Section 6.2.1 requires that the separation have a fire rating, pipe penetrations shall be fire

stopped in accordance with the Building Code.

6.6.3 Pipe Marking. Piping shall be marked as required by Section 5.16.5.


6.6.4 Connection of Ammonia Cylinders. Ammonia cylinders shall not be connected a

refrigeration system unless ammonia is in the process of being transferred by authorized

personnel.

6.7 Eyewash/Safety Shower

6.7.1 General. Each machinery room shall have access to a minimum of two eyewash/safety

shower units, one of which shall be located inside the machinery room and one of which shall

be located outside of the machinery room. Additional eyewash/safety shower units shall be

installed such that an identified hazard in the machinery room is no more than 55 feet from an

eyewash/safety shower unit.

EXCEPTION: A single permanent eyewash/safety shower unit, located either inside

or outside of a machinery room shall be permitted provided that an

operational procedure has been developed to make an additional

eyewash/safety shower unit available whenever maintenance

procedures with an ammonia exposure risk are performed. The

additional eyewash/safety shower unit shall be located not more than

55 feet from the identified hazard associated with the maintenance

work. The additional eyewash/safety shower unit shall be permitted to

be portable or temporary and located either: 1) Outside of the

machinery room, where the permanent installation is located inside, or

2) Inside of the machinery room where the permanent installation is

located outside of the room.

6.7.2 Path of Travel. The path of travel from an identified hazard to at least one eyewash/safety

shower unit shall be unobstructed and shall not include intervening doors.

EXCEPTION: Where a single eyewash/safety shower unit is provided outside the

machinery room in accordance with the exception to Section 6.7.1, a

single machinery room exit door shall be permitted in the path of

travel.

6.7.3 Installation Standard. Emergency eyewash/safety shower unit installations shall comply

with ANSI/ISEA Z358.1-2009.

6.8 Electrical Safety

6.8.1 General. Electrical equipment and wiring shall be installed in accordance with the Electrical

Code.

6.8.2 Hazardous (Classified) Locations. Machinery rooms shall be designated as Ordinary

Locations, as described in the Electrical Code, where the machinery room is provided with

emergency ventilation in accordance with Section 6.14.8.

Machinery rooms not provided with emergency ventilation shall be designated as not less

than a Class I, Division 2, Group D Hazardous (Classified) Locations, and electrical

equipment installed in the machinery room shall be designed to meet this requirement.


6.8.3 Design Documents. Electrical design documents shall indicate whether the machinery room

is designated as an Ordinary Location or as a Hazardous (Classified) Location. Where the

machinery room is designated as a Hazardous (Classified) Location, the Class, Division and

Group of the electrical classification, as required by the Electrical Code, shall be indicated in

the documentation.

6.9 Drains

6.9.1 General. Floor drains shall be provided to dispose of wastewater.

6.9.2 Contaminant Control. Where a drainage system is not designed for handling oil, secondary

coolants or other liquids that might be spilled, a means shall be provided to prevent such

substances from entering the drainage system.

6.9.3 Control of Ammonia Spills. A means shall be provided to limit the spread of a liquid

ammonia spill such that liquid ammonia that has entered a machinery room drainage system

does not expose occupied areas outside of the machinery room.

6.10 Entrances and Exits

6.10.1 General. Machinery rooms exceeding 1,000 square feet (93 m2) in area shall have not less

than two exit- or exit-access doors. Where two doors are required, one door shall be

permitted to be served by a fixed ladder or an alternating tread device. Doors shall be

separated by a horizontal distance equal to or greater than one-half of the maximum

horizontal dimension of room. All portions of a machinery room shall be within 150 feet

(45,720 mm) of an exit- or exit-access door, unless an increased travel distance is permitted

by the Building Code.

6.10.2 Door Features. Machinery room doors shall be self-closing and tight-fitting. Doors that are

part of the means of egress shall be equipped with panic hardware and shall be side-hinged to

swing in the direction of egress for occupants leaving the machinery room. Where the

machinery room is not provided with fire sprinklers, doors communicating with the building

interior shall be 1-hour fire-rated. Doors to the outdoors shall be fire-rated where required by

the Building Code based on the fire-rating required for exterior wall openings.

6.10.3 *Required Exterior Door. Machinery rooms shall have a minimum of one exit door that

opens directly to the outdoors or to a vestibule that leads directly to the outdoors.

EXCEPTION: Machinery rooms equipped with a fire sprinkler system and having a

floor area of 500 square feet (46.5 m²) or less shall not be required to

have a door that opens directly to the outdoors or to a vestibule leading

directly to the outdoors.

6.10.4 Separation from Fire Escapes and Stairways. Exit doors leading to the outdoors shall not

be located beneath a fire escape or open stairway.


6.11 Lighting

6.11.1 General. Machinery rooms shall be equipped with light fixtures delivering a minimum of 30

foot-candles [320 lumens/m2] at the working level, 36 inches (0.91 m) above a floor or

platform.

6.11.2 Light Control. A manual control for the illumination source shall be provided. Occupancy

sensors shall be permitted as an additional control for lighting, but not in lieu of a manual

control.

6.12 Emergency Control Switches.

6.12.1 Emergency Stop Switch. A clearly-identified emergency shutoff switch with a tamper-

resistant cover shall be located outside and adjacent to the designated principal machinery

room door leading to the outdoors. The switch shall provide off-only control of refrigerant

compressors, refrigerant pumps, and normally-closed automatic refrigerant valves located in

the machinery room. The function of the switch shall be clearly marked by signage near the

controls.

6.12.2 Emergency Ventilation Control Switch. A clearly-identified control switch for emergency

ventilation with a tamper-resistant cover shall be located outside and adjacent to the

designated principal machinery room door leading to the outdoors. The switch shall provide

“ON/AUTO” override capability for emergency ventilation. The function of the switch shall

be clearly marked by signage near the controls.

6.13 Ammonia Detection and Alarm

6.13.1 General. Machinery rooms shall be provided with Level 3 detection and alarm in accordance

with Section 17.7.3. The detection and alarm system shall comply with Chapter 17.

6.13.2 Alarm Response

Detection of ammonia concentrations less than 25 ppm requires no alarm or response.

*Detection of ammonia concentrations equal to or exceeding 25 ppm shall activate

visual indicators, activate an audible alarm, and stop fans and close dampers to prevent

inadvertent spread of ammonia vapor as specified in Section 6.14.2. The visual

indicator and audible alarm shall be permitted to automatically reset if the ammonia

concentration drops below 25 ppm.

*Detection of ammonia concentrations equal to or exceeding 160 ppm shall activate

visual indicators and an audible alarm and shall activate emergency ventilation, where

required, in accordance with Section 6.14.8. Once activated, emergency ventilation

continue to operate until being manually reset by a switch located in the machinery

room.


Detection of ammonia concentrations that exceed a detector’s upper detection limit or

40,000 ppm (25% LFL), whichever is lower, shall activate visual indicators and an

audible alarm and shall activate emergency ventilation, where required, in accordance

with Section 6.14.8. Once activated, emergency ventilation continue to operate until

being manually reset by a switch located in the machinery room. In addition, the

following equipment in the machinery room shall be automatically de-energized:

1. Refrigerant compressors.

2. Refrigerant pumps.

3. Normally-closed automatic refrigerant valves.

6.14 Ventilation

6.14.1 *Occupant Breathing Air. During occupied conditions, outdoor air shall be provided at a

rate of not less than 0.5 cfm per square foot (0.0025 m3/s • m2) of machinery room area or 20

cfm (0.009 m3/s) per occupant, whichever is greater.

6.14.2 General Exhaust and Air Conditioning Equipment. Machinery room exhaust fans and air

conditioning equipment that is not intended for exhausting ammonia vapor shall be de-

energized and fan dampers, where provided, shall close upon detection of ammonia in

accordance with Section 6.13.2.2.

6.14.3 Exhaust Ventilation. Machinery rooms shall be vented to the outdoors by means of a

mechanical exhaust ventilation system.

Mechanical exhaust ventilation system shall be automatically activated by ammonia

leak detection or temperature sensors, and the system shall also be manually operable.

Mechanical exhaust ventilation systems shall be designed to produce not less than the

temperature control ventilation rate required by Section 6.14.7 and the emergency

exhaust ventilation rate required by Section 6.14.8.

6.14.4 Fan Options. Multiple fans or multispeed fans shall be permitted to provide both

temperature control exhaust ventilation in accordance with Section 6.14.7 and emergency

exhaust ventilation in accordance with Section 6.14.8. Fans used for both temperature control

and emergency ventilation shall be controlled in a manner that provides the emergency

ventilation rate when emergency ventilation is activated.


6.14.5 Inlet Air

Outdoor make-up air shall be provided to replace air being exhausted and shall be

designed to maintain negative pressure in the machinery room, not to exceed 0.25 in.

(6.4 mm) water column.

Make-up air supply locations in the machinery room shall be positioned to prevent

short-circuiting of the make-up air directly to the exhaust.

Make-up air openings shall be covered with a corrosion-resistant screen of not less

than ¼” mesh or equivalent protection.

Intakes for make-up air shall be positioned to draw uncontaminated outdoor air and

avoid recirculation of exhausted air.

Intakes for make-up air to the machinery room shall only serve the machinery room.

Motorized louvers or dampers, where utilized, shall fail to the open position upon loss

of power.

Where direct openings or openings with ducts are not provided to supply make-up air,

make-up air shall be provided by fans or fans with ducts.

6.14.6 Exhaust

*Machinery room exhaust shall be to the outdoors not less than 20 feet (6 m) from a

property line or openings into buildings, measured horizontally, vertically, or a

combination of both.

Machinery room exhaust shall discharge vertically upward with a minimum discharge

velocity of 2,500 feet-per-minute (762 M/min.) at the required emergency ventilation

flow rate.

Exhaust air ducts from the machinery room shall only serve the machinery room.

Machinery room exhaust fans, regardless of function, shall be equipped with non-

sparking blades.

*Emergency exhaust fan motors located in the air stream or inside the machinery room

shall be of the totally-enclosed type. Fan motors meeting this requirement are not

required to be listed for use in hazardous (classified) locations.


6.14.7 Temperature Control Ventilation

*Temperature control mechanical ventilation design capacity shall be the volume

required to limit the room dry bulb temperature to 104°F (40°C), taking into account

the ambient heating effect of machinery in the room and with the make-up air entering

the room at a 1% design dry bulb temperature. The emergency ventilation system shall

be permitted to be used to supplement temperature control ventilation, and vice-versa.

EXCEPTION: A reduced temperature control ventilation rate shall be permitted

where a means of cooling is provided or room electrical

equipment is designed to accommodate temperatures exceeding a

dry bulb temperature of 104°F (40°C), in accordance with UL

Listings and the Electrical Code.

Partial operation of a multiple-fan system or multi-speed fans shall be permitted to

deliver the temperature control ventilation design capacity.

Temperature control mechanical ventilation shall be continuous or shall be activated

by both of the following:

1. A thermostat measuring space temperature.

2. A manual control provided in accordance with Section 6.12.2, where temperature

control ventilation is designed to contribute to emergency ventilation.

6.14.8 Emergency Ventilation

*Emergency mechanical ventilation systems shall provide not less than 30 air changes

per hour based on the gross machinery room volume. The emergency ventilation

system shall be permitted to include temperature control ventilation fans that meet the

requirements of Section 6.14.6.5 and Section 6.14.7.3, Item 2.

EXCEPTION: Where approved, emergency mechanical ventilation shall not be

required for a limited-charge refrigeration system that will not

yield an ammonia concentration exceeding 40,000 ppm in the

machinery room following a release of the entire charge from the

largest independent refrigerant circuit, based on the volume

calculation determined in accordance with Section 5.4. The

designer shall provide a copy of the calculations to be retained at

the site.

Emergency mechanical ventilation shall be activated by both of the following:

1. Ammonia leak detection complying with Section 6.13.

2. A manual control provided in accordance with Section 6.12.2.


Emergency ventilation shall be powered independently of the equipment within the

machinery room and shall continue to operate regardless of whether emergency

shutdown controls for the machinery room have been activated.

A monitored location shall be notified upon loss of power to or failure of the

emergency mechanical ventilation system.

6.14.9 Ventilation Remote Controls. Emergency control switches for ventilation shall comply

with Section 6.12.2.

6.14.10 Testing

*A schedule for testing the mechanical ventilation system shall be established based

on manufacturers’ recommendations, unless modified based on documented

experience. Testing shall include operation of the ventilation system based on

ammonia detection at the concentration set forth in Section 6.13.2 and by manual

controls required by Section 6.12.2.

Where manufacturers’ recommendations are not provided, the mechanical ventilation

system shall be tested not less than twice per year.

Alarm testing shall comply with Section 17.3.

6.15 Signage. Signage shall be provided in accordance with this section.

6.15.1 *NFPA 704 Placards. Buildings and facilities with refrigeration systems shall be provided

with placards accordance with NFPA 704 and the Mechanical Code.

6.15.2 Alarm Signage. Alarm signage shall be provided in accordance with Section 17.6.

6.15.3 Restricted Access Signage. Each machinery room entrance doors shall be marked with a

permanent sign in accordance with Section 6.3.4 to indicate that only authorized personnel

are permitted to enter the room.


Chapter 7. Refrigeration Equipment Located in Areas Other Than Machinery Rooms

7.1 General. Industrial, public assembly, commercial and large mercantile occupancies that are

permitted by Section 4.2 to contain ammonia refrigeration systems or equipment outside of a

machinery room shall comply with this chapter.

7.2 Requirements for Non-machinery Room Spaces. Where an ammonia refrigeration system or

equipment is installed outside of a machinery room, the area containing the system or equipment

shall comply with this section.

7.2.1 Separation. The area shall be separated from other occupancies by tight construction with

tight-fitting doors.

7.2.2 Access. Access to the refrigeration equipment shall be restricted to authorized personnel.

7.2.3 Egress. A means of egress directly to the outdoors, an enclosed exit stairway, or to a

horizontal exit or exit passageway complying with the Building Code shall be provided.

EXCEPTIONS: 1. Rooms or areas that are 500 ft² or less in area shall not be required

to have a means of egress directly to the outdoors.

2. Rooms or areas that are equipped with a fire sprinkler system shall

not be required to have a means of egress directly to the outdoors.

3. Where a minimum of 100 ft² (9.3 m²) of floor area is provided for

each occupant.

7.2.4 *Detection and Alarms. Level 1 detection and alarm shall be provided in accordance with

Section 17.7.1. The detection and alarm system shall comply with Chapter 17.

EXCEPTIONS: 1. Unoccupied areas with only continuous piping that does not include

valves, valve assemblies, equipment, or equipment connections.

2. Where approved, alternatives to fixed detection systems shall be

permitted for rooms or areas in industrial occupancies that are always

occupied.

7.2.5 Physical Protection. Equipment shall be protected where there is a risk of physical damage.

Where equipment containing ammonia is located in an area with heavy vehicular traffic

during normal operations and there is a risk of impact, vehicle barriers or alternative

protection shall be provided in accordance with the Fire Code.

7.2.6 Temperature Control Ventilation. Where necessary to maintain dry bulb temperature in

the area at or below 104°F (40°C), temperature control ventilation shall be provided.

7.2.7 Environmental Compatibility. Equipment shall be designed to operate in the environmental

conditions of the area in which it is to be installed.


7.2.8 Illumination. The refrigeration equipment shall be equipped with lighting, or the area with

refrigeration equipment shall be equipped with light fixtures delivering a minimum of 30

foot-candles [320 lumens/m2] at the working level, 36 inches (0.91 m) above a floor or

platform.

7.2.9 Service Provisions. Service provisions shall comply with Section 5.14.

7.2.10 Penthouses. Penthouses that are open to an interior space shall be regulated as part of the

interior space. Penthouses that are isolated from an interior space shall be regulated as an

equipment enclosure in accordance with Section 5.18.

7.3 Ventilation

7.3.1 Refrigeration Systems and Portions Thereof with a Total Connected Compressor Power

Not Exceeding 100 HP (74.6 kW)

*Industrial occupancies containing ammonia refrigeration systems or portions thereof

with a total connected compressor power not exceeding 100 HP (74.6 kW), located

outside of a machinery room in accordance with Section 4.2.3 Item 4, shall comply

with this section.

*Emergency mechanical ventilation shall be in accordance with this section.

7.3.1.2.1 Where the quantity of ammonia in a refrigeration system would yield an ammonia

concentration exceeding 40,000 ppm in the in the room or space containing the

equipment following a release of the entire charge from the largest independent

refrigerant circuit, based on the volume calculation determined in accordance with

Section 5.4, emergency ventilation at a rate of 30 air changes per hour shall be

provided.

EXCEPTION: Where approved, alternatives to emergency mechanical exhaust

ventilation of the entire room that will maintain the

concentration below 40,000 ppm shall be permitted.

7.3.1.2.2 When calculations performed in accordance with Section 5.4 are used as a basis for

omitting emergency mechanical ventilation, the designer shall provide a copy of

the calculations to be retained at the site.

7.3.1.2.3 Where an emergency mechanical ventilation system is required, Level 3 ammonia

detection and alarm in accordance with Section 17.7.3 shall be provided, and the

system shall comply with Sections 6.14.8.3 and 6.14.8.4. Emergency detection and

alarms shall comply with Chapter 17.

7.3.2 Outdoor Systems. Where a refrigeration system or equipment is located outdoors and is

enclosed or partially enclosed by a penthouse, lean-to, or other structure, the refrigeration

system or equipment shall be located not less than 20 feet from building entrances and exits

and natural ventilation shall be provided as follows or mechanical ventilation shall be

provided in accordance with Section 6.14.


The free-aperture cross section for natural ventilation shall be not less than:

F = G0.5 (I-P)

F = 0.138G0.5 (SI)

Where:

F = the free opening area, ft² (m²)

G = the mass of ammonia in the largest independent circuit, any part of which is

located within the enclosure or structure, lb (kg)

7.3.3 Equipment Pits Located Indoors

Where refrigeration equipment containing ammonia is located in an indoor pit that is

5 feet (1.52 m) or more in depth, emergency ventilation at a rate of 30 air changes per

hour shall be provided and Level 3 ammonia detection and alarm complying with

Section 17.7.3 shall be provided. The emergency mechanical exhaust ventilation

system shall comply with Sections 6.14.8.3 and 6.14.8.4.

Make-up air shall be supplied near the floor of the indoor pit. Air shall be directed

toward the equipment and away from the pit exit.

Where pit ventilation is arranged to exhaust through a room that is open to the pit, the

combined volume of the pit and the room shall serve as the basis for calculating

emergency mechanical exhaust ventilation.


Part 3 Equipment

Chapter 8. Compressors

8.1 General. Ammonia refrigeration compressors shall comply with this chapter.

8.2 Design Pressure. The minimum design pressure shall comply with Section 5.6.

8.3 Positive-Displacement Compressor Protection

8.3.1 *Where a stop valve is provided in the discharge connection, a positive-displacement

compressor shall be equipped with a pressure relief device selected to prevent the discharge

pressure from increasing to more than 10% above the lowest of the maximum allowable

working pressures of the compressor or any other equipment located in the path between the

compressor and the stop valve, or in accordance with Section 15.3.7, whichever is larger. The

pressure relief device shall discharge into the low pressure side of the system or in

accordance with the requirements of Section 15.5.1 for atmospheric discharge.

The relief device shall be sized based on compressor flow at a minimum of 50°F (10°C)

saturated temperature at the compressor suction or at design saturated suction temperature,

whichever is greater.

The minimum size compressor pressure vessel relief connection shall be in accordance with

Section 12.2.3.

The area of the opening through piping, fittings, and pressure relief devices, where installed,

including 3-way valves for dual reliefs, between a compressor pressure vessel, such as an oil

separator, and its pressure relief valve, shall be not less than the area of the pressure relief

valve inlet. See Section 15.4.2.

EXCEPTIONS 1. For compressors capable of operating only when discharging to the

suction of a higher-stage compressor, flow shall be calculated at the

saturated suction temperature equal to the design operating

intermediate temperature.

2. For compressors equipped with automatic capacity regulation which

actuates to minimum flow at 90% or below of the pressure-relief

device setting and a pressure-limiting device is installed and set in

accordance with Section 8.3.2, the discharge capacity of the relief

device shall be allowed to be the minimum regulated flow rate of the

compressor.


8.3.2 *Compressors shall be provided with high-discharge-temperature, low-suction-pressure, and

high-discharge-pressure limiting devices to shut-down the compressors when the safe ranges

are exceeded. Compressors using forced feed oil lubrication shall be provided with an

indicating-type lubrication failure control for low oil pressure shut-down. Except for booster

compressors, high-pressure-limiting devices shall be of the manual-reset type. The setting of

high-pressure-limiting devices shall not exceed the lower of the compressor manufacturer’s

recommendation or 90% of the setting of the pressure-relief device on the discharge side of

the compressor. The setting of low-pressure-limiting devices shall be the higher of:

1. The system’s minimum design pressure to protect against freeze-up or other damage.

2. The compressor manufacturer’s recommendations.

8.3.3 Protection from exposed rotating parts shall be in accordance with Section 5.19.2.

8.3.4 If rotation is to be in only one direction, a rotation arrow shall be cast in or permanently

attached to the compressor frame using an attached label or plate or equivalent means.

8.3.5 Ultimate strength requirements shall be in accordance with Section 5.15.2.

8.4 Procedures/Testing. Compressors shall be strength tested to a minimum of 1.5 times the design

pressure, subsequently leak tested, and proven tight at a pressure not less than design pressure.

8.5 Equipment Identification

8.5.1 The following data shall be provided on nameplates or labels affixed to compressors:

1. Manufacturer’s name

2. Manufacturer’s serial number

3. Manufacturer’s model number

4. Year manufactured (encoded with serial number is permissible)

5. Maximum allowable working pressure (MAWP)

6. Maximum rotation speed in rpm

7. Direction of rotation; comply with Section 8.3.4 if applicable.

8.5.2 A compressor without a nameplate per the requirements of Section 8.5.1 shall not be used

unless the applicable compressor operating limitations have been verified through the

identification of the manufacturer and the manufacturer’s model number of the compressor

from casting numbers or similar positive identification.

8.6 Compressor Installation. Design for compressor installation shall comply with this section.

8.6.1 Compressors shall have one or more valved pump-out connections for removal of ammonia.

Compressors that are packaged with other equipment shall be permitted to have pump-out

connections located elsewhere on the package.

8.6.2 The design shall account for the impact on the compressor if operating in low ambient

temperatures, to avoid condensation of ammonia in the compressor package or piping during

operation or standby.


8.6.3 At a minimum, designs shall include provisions for installing compressor foundations

according to manufacturers’ instructions, grouting, or for installing isolation from the floor or

structure of the building, where required.

8.6.4 Where a variable frequency drive is used to operate a compressor, the manufacturer’s

instructions shall be followed and the compressor using the variable frequency drive shall be

stable at frequencies during its operation.

If resonant harmonics are encountered, identified, and cannot be isolated from the

system, frequencies shall be permitted to be skipped, if applicable.

8.6.5 Refrigeration compressors shall be selected to operate within the design limitations specified

by the compressor manufacturer.

8.6.6 *Compressors shall be fitted with a discharge check valve, a suction check valve or both as

necessary to avoid backflow of refrigerant and the accumulation of liquid from the

condensation of gas in the discharge piping when the compressor is shut down. Other means

of avoiding backflow and accumulation of liquid shall be permitted. Stop valves shall be in

accordance with Section 13.3.1.

EXCEPTION: Self-contained systems designed to equalize on shutdown shall not be

required to have a suction or discharge check valve.

8.6.7 Before being applied in a new design, any previously used compressor shall be inspected for

signs of alteration, modification, or physical repair that might affect the integrity of the

compressor casing. Any compressor integrity issue shall be corrected and verified before

operation.

Where a compressor casing has been altered, modified or repaired, the casing shall be

recertified prior to operation for pressure compliance by the manufacturer or insurance

underwriter and recertification papers shall be maintained on site with the refrigeration

management program.

8.6.8 The compressor shall be fitted with pressure and temperature indicating devices, including

but not limited to gauges or readouts on a control display screen that allow an observer to

visually determine the compressor’s suction pressure; discharge pressure; oil pressure, if the

compressor uses forced feed lubrication; and discharge temperature.

8.6.9 *High-liquid Level Alarm. Where a compressor suction line is directly connected to a

vessel, the compressor suction line shall be equipped with a sensor to activate an alarm and

cause the associated compressors to shut down if a high ammonia liquid level is detected.


Chapter 9. Refrigerant Pumps

9.1 General. Refrigerant pumps shall comply with this chapter.

EXCEPTION: Liquid ammonia transfer employing pressure differential to move liquid

ammonia, such as pumper drum systems.

9.2 Design

9.2.1 Minimum design pressure shall be in accordance with Section 5.6, or greater where required

by a specific application design requiring higher pressure.

9.2.2 A means of protecting refrigerant pumps and connected piping from hydrostatic overpressure

shall be provided.

Permissible means of protection shall include, but not be limited to, either:

1) A hydrostatic or differential pressure relief device, or 2) A vent pipe containing a

normally-open isolation valve. The inlet connection for the relief device or vent pipe

shall be located on the pump casing or piping between the stop valves or stop check

valves at the pump inlet and outlet, except that when a check valve is located between

the pump and its outlet stop valve, the relief device or vent pipe inlet shall be

connected to the pipe between the discharge check valve and stop valve. The

discharge of this relief or vent pipe shall connect either to the pump suction line

upstream of the pump suction stop valve or to the vessel to which the pump suction is

connected. This pressure relief device or vent pipe shall be external to the pump

housing.

9.2.3 Ultimate strength requirements shall be in accordance with Section 5.15.2.

9.2.4 Protection from exposed rotating parts shall be in accordance with Section 5.19.2.

9.2.5 Refrigerant pumps shall be suitable for the service in which they are being applied.

9.2.6 Refrigerant pumps shall be provided with isolation valves.

9.2.7 Refrigerant pumps shall be installed on a foundation designed for expected loads.

9.3 Procedures/Testing. Refrigerant pumps shall be strength tested to a minimum of 1.5 times the

design pressure, subsequently leak tested, and proven tight at a pressure not less than design

pressure.

9.4 Equipment Identification. Manufacturers producing refrigerant pumps shall permanently affix a

nameplate to the pump providing not less than the following:





9.4.1 Pump data sheet submittals shall include the following information from the manufacturer:

1. “Ammonia”

2. Operating condition data

3. Performance data

4. Construction data – including maximum allowable pressure at operating temperature,

test pressure, bearing type, and impeller data

5. Head – differential pressure (ft, m, or psi)

6. Impeller identification (diameter size)

7. RPM (Speed) - for fixed-speed pumps and minimum, maximum, & operating RPM’s

for adjustable speed pumps

8. Capacity (maximum rated gpm or liters/min) with identified impeller

9. Materials – metals and gaskets

10. Motor (Driver) information

11. Electric motor ratings if applicable - volts, full load amps (FLA), frequency (Hz),

phase, output (HP and/or KW)

12. Electric heater ratings if applicable - volts, amps, phase, output (KW)

13. Insulation classification

14. Piping connections schematic

15. Pump operating procedure description

16. Inspections & tests verification – performance and pressure test

17. Minimum Circuit Amps (MCA) and Maximum Over-Current Protection (MOCP) – if

applicable

18. Weight

19. Direction of rotation - confirmed and documented, Mark or Label a directional arrow

on the unit

20. Year manufactured

9.4.2 Pumps shall be capable of being pumped out for removal of ammonia.


Chapter 10. Condensers

10.1 *General. Condensers shall comply with this chapter.

10.2 Air-Cooled Condensers and Air-Cooled De-superheaters. Tube-and-fin and micro-channel type

air-cooled condensers and air-cooled de-superheaters shall comply with this section.

10.2.1 Design

Minimum design pressure shall be in accordance with Section 5.6.

Ultimate strength requirements shall be in accordance with Section 5.15.2.

Where the refrigerant inlet and outlet piping of air-cooled condensers and de-

superheaters can be automatically isolated, they shall be protected from hydrostatic

overpressure in accordance with Section 15.6.

Protection from exposed rotating parts shall be in accordance with Section 5.19.2.

Fan speeds shall not exceed the design speed limit recommended by the manufacturer.

10.2.2 Procedures/Testing. Air-cooled condensers and de-superheaters shall be strength tested to a

minimum of 1.1 times the design pressure, subsequently leak tested, and proven tight at a

pressure not less than design pressure.

10.2.3 Equipment Identification. The following data shall be provided on nameplates or labels

affixed to equipment:

EXCEPTION: Nameplate data is not required on air-cooled de-superheaters that are

integral with condensers.





5. Design pressure

6. Direction of fan rotation

7. Electric motor power

8. Electric supply: volts, full load amps, frequency (Hz), phase.

9. At a minimum, if not on the nameplate, the condenser submittal sheets shall have the

MDMT (Minimum Design Metal Temperature).

10.2.4 Clearances. Air-cooled condensers shall be installed with manufacturer-recommended

minimum clearances for position of the units and their respective air inlets and air outlets to

avoid short-circuiting and to ensure unobstructed air flow.

10.2.5 Design for Ambient Temperature. Shell-and-tube condensers shall be designed for the

range of ambient temperatures at the installed location.


10.3 Evaporative Condensers. Evaporative condensers shall comply with this section.

10.3.1 Design



Pressure vessels incorporated into evaporative condensers shall comply with

Chapter 12.

Where the refrigerant coil inlet and outlet piping of evaporative condensers can be

automatically isolated, the condenser shall be protected from refrigerant hydrostatic

overpressure in accordance with Section 15.6.



Evaporative condensers shall be adequately anchored and supported.

10.3.2 Procedures/Testing Evaporative condensers shall be strength tested to a minimum of 1.1

times the design pressure, subsequently leak tested, and proven tight at a pressure not less

than design pressure.

10.3.3 Equipment Identification The following data shall be provided on nameplates or labels






5. Design pressure

6. Direction of fan rotation, and water circulating pump, if supplied

7. Electric motor rating for fans, and water circulating pump, if supplied

8. Electric supply: volts, full load amps, frequency (Hz), phase.

10.3.4 Clearances. Evaporative condensers shall be installed with manufacturer-recommended

minimum clearances for position of the units and their respective air inlets and air outlets to

avoid short-circuiting and to ensure unobstructed air flow.

10.3.5 Freeze Protection. Freeze protection shall be provided as needed for the sump and water

piping.

10.3.6 Drainage of Overflow and Waste Water. Drainage of overflow and waste water shall be

provided, as needed.


10.3.7 Design for Ambient Temperature. Shell-and-tube condensers shall be designed for the

range of ambient temperatures at the installed location.

10.4 Shell-and-Tube Condensers. Shell-and-tube condensers shall comply with this section.

Equipment covered by this section includes horizontal and vertical shell-and-tube condensers with

closed water passes and vertical shell-and-tube condensers with open water passes.

10.4.1 Design


Secondary coolant side ultimate strength requirements shall be in accordance with

Section 5.15.2.

Pressure vessels incorporated into shell-and-tube condensers shall comply with

Chapter 12.

Where the refrigerant inlet and outlet piping of shell-and-tube condensers can be

isolated, the refrigerant side shall be pressure-relief protected in accordance with

Section 15.3.

EXCEPTION: Where the condenser is not a pressure vessel, the condenser shall

be protected from hydrostatic overpressure in accordance with

Section 15.6.

Where the secondary coolant inlet and outlet piping of shell-and-tube condensers can

be automatically isolated, protection from hydrostatic overpressure shall be in

accordance with Section 15.6.

10.4.2 Procedures/Testing. Shell-and-tube condensers shall be tested in accordance with ASME

B&PVC, Section VIII, Division 1 or international equivalent, if applicable, but at a

minimum, shall be strength tested to a minimum of 1.1 times the design pressure,

subsequently leak tested, and proven tight at a pressure not less than design pressure.


10.4.3 Equipment Identification. Manufacturers producing shell-and-tube condensers shall

provide the following minimum data on a nameplate affixed to the equipment:

1. ASME stamp, where applicable

2. National Board Number, where applicable

3. Manufacturer’s name, preceded by the words “certified by” on nameplates of integral

ASME-stamped vessels

4. Shell-side maximum allowable working pressure (MAWP) _____ at _____

temperature

5. Tube-side maximum allowable working pressure (MAWP) _____ at _____

temperature

6. Shell-side minimum design metal temperature (MDMT) _____ at _____ pressure

7. Tube-side minimum design metal temperature (MDMT) _____ at _____ pressure


9. Manufacturer’s model number, where applicable


11. Type of construction in accordance with ASME B&PVC, Section VIII, Division 1 or

international equivalent, where applicable.

Manufacturers producing shell-and-tube condensers with integral pressure vessels,

such as condensers with refrigerant in a shell qualifying as a pressure vessel, shall

provide data in accordance with the relevant “UG” sections of ASME B&PVC,

Section VIII, Division 1 or international equivalent.

10.4.4 Shell-and-Tube Condenser Installation Considerations

Clearance shall be provided as necessary to accommodate maintenance or replacement

of the condenser tubes.

Shell-and-tube condensers shall be designed for the range of ambient temperatures at

the installed location.

10.5 Plate Heat Exchanger Condensers. Plate heat exchanger condensers shall comply with this

section. Equipment covered by this section includes plate heat exchanger condensers of the plate-

and-shell type and of the plate-and-frame type.

10.5.1 Design



Pressure vessels incorporated into plate heat exchanger condensers, such as the shell

of a plate-and-shell condenser with refrigerant in a shell qualifying as a pressure

vessel, shall comply with Chapter 12.


Where the refrigerant inlet and outlet piping of ammonia-containing plate packs can

be isolated, the ammonia side of the plate pack shall be pressure-relief protected in


EXCEPTION: Where the condenser is not a pressure vessel, it shall be protected from

hydrostatic overpressure in accordance with Section 15.6.

Where the non-refrigerant process fluid inlet and outlet lines of plate packs can be

automatically isolated, they shall be protected from hydrostatic overpressure in


10.5.2 Procedures/Testing. Plate heat exchanger condensers shall be tested in accordance with

ASME B&PVC Section VIII, Division 1 or international equivalent, if applicable, but at a



10.5.3 Equipment Identification. Manufacturers producing plate heat exchanger condensers shall

provide the following minimum data on a nameplate affixed to the equipment.



3. Manufacturer’s name, preceded by the words “certified by,” if the heat exchanger is

ASME-stamped

4. Hot-side maximum allowable working pressure (MAWP) _____ at_____ temperature,

where applicable

5. Cold-side maximum allowable working pressure (MAWP) _____ at _____

temperature

6. Hot-side minimum design metal temperature (MDMT) _____ at_____ pressure, where

applicable

7. Cold-side minimum design metal temperature (MDMT) _____ at _____ pressure




11. Test pressure, note test type; hydraulic or pneumatic

12. Type of construction (in accordance with ASME B&PVC, Section VIII, Division 1 or

international equivalent, where applicable)

Manufacturers producing plate heat exchanger condensers with integral pressure

vessels, such as plate-and-shell heat exchangers with refrigerant in a shell qualifying

as a pressure vessel, shall provide data in accordance with ASME B&PVC, Section

VIII, Division 1 or international equivalent.

10.5.4 Plate Heat Exchanger Condenser Installation Considerations.

Clearance shall be provided as necessary to accommodate removal and replacement of

the condenser plates if this service is to be done in the installed location.

Plate heat exchanger type condensers shall be designed for the range of ambient

temperatures at the installed location.


10.6 Double-Pipe Condensers. Double-pipe condensers shall be in accordance with this section.

Equipment covered by this section is double-pipe condensers with closed-water passes.

10.6.1 Design.


Secondary coolant side ultimate strength requirements shall be in accordance with

Section 5.15.2.

Pressure vessels incorporated into double-pipe condensers shall comply with

Chapter 12.

Where the refrigerant inlet and outlet piping of double-pipe condensers can be

isolated, the refrigerant side shall be pressure-relief protected in accordance with

Section 15.3.

EXCEPTION: Where the condenser is not a pressure vessel it shall be protected from

hydrostatic overpressure in accordance with Section 15.6.

Where the secondary-coolant inlet and outlet piping of double-pipe condensers can be

automatically isolated, they shall be protected from hydrostatic overpressure in


10.6.2 Procedures/Testing. Double-pipe condensers shall be tested in accordance with ASME

B&PVC, Section VIII, Division 1 or international equivalent, if applicable, but at a



10.6.3 Equipment Identification

Manufacturers producing double-pipe condensers shall provide the following

minimum data on a nameplate affixed to the equipment:



3. Manufacturer’s name, preceded by the words “certified by” on nameplates of

integral ASME-stamped vessels

4. Shell-side maximum allowable working pressure (MAWP) _____ at _____

temperature

5. Tube-side maximum allowable working pressure (MAWP) _____ at _____

temperature

6. Shell-side minimum design metal temperature (MDMT) _____ at _____ pressure

7. Tube-side minimum design metal temperature (MDMT) _____ at _____ pressure




Type of construction in accordance with ASME B&PVC, Section VIII, Division 1 or

international equivalent, where applicable.


Manufacturers producing double-pipe condensers with integral pressure vessels, such

as condensers with refrigerant in a shell qualifying as a pressure vessel, shall provide

data in accordance with the relevant “UG” sections of ASME B&PVC, Section VIII,

Division 1 or international equivalent.

10.6.4 Double-Pipe Condenser Installation Considerations.

Clearance shall be provided as necessary to accommodate removal and replacement of

condenser pipes if this service is to be done in its installed location.

Double-Pipe condensers shall be designed for the range of ambient temperatures at the

installed location.


Chapter 11. Evaporators

11.1 General. Evaporator coils and micro-channel heat exchangers shall comply with this chapter.

11.2 Forced-Air Evaporator Coils

11.2.1 Design


Ultimate strength shall be in accordance with Section 5.15.2.

Where refrigerant coil inlet and outlet lines can be automatically isolated, they shall be

protected from hydrostatic overpressure in accordance with Section 15.6.



Pressure vessels coupled to evaporators shall comply with Chapter 12.

11.2.2 Procedures/Testing. Evaporator coils shall be strength tested to a minimum of 1.1 times the

design pressure, subsequently leak tested, and proven tight at a pressure not less than design

pressure.

11.2.3 Equipment Identification. The following data shall be provided on nameplates or labels






5. Design pressure

6. Direction of fan rotation, if supplied

7. Electric motor size for fans, if supplied

8. Electric defrost heater and drain pan heater ratings, as applicable

9. Electric supply: volts, full load amps, frequency (Hz), phase

10. Minimum Design Metal Temperature (MDMT), if applicable, or at a minimum,

submitted with the equipment manufacturer’s data sheets.

11.2.4 Installation Considerations.

Manufacturer’s recommended clearances for unobstructed airflow at the inlet and

outlet of the forced-air evaporator shall be provided.

A means for preventing freezing inside condensate drain lines, such as but not limited

to slope to drain, heat tracing, insulation, or clean-outs, shall be provided where lines

are exposed to freezing temperatures.


11.3 Shell-and-Tube Evaporators

11.3.1 Shell-and-Tube Evaporators with ammonia in shell. Shell-and-tube evaporators shall

comply with this section.

Design

11.3.1.1.1 Minimum design pressure shall be in accordance with Section 5.6.

11.3.1.1.2 Pressure vessels coupled to shell-and-tube evaporators shall comply with

Chapter 12.

11.3.1.1.3 Where the tube-side inlet and outlet lines of shell-and-tube evaporators with the

refrigerant in the shell are automatically isolated, the tube-side shall be protected

from hydrostatic overpressure in accordance with Section 15.6.

Procedures/Testing. Shell-and-tube evaporators shall be tested in accordance with

ASME B&PVC, Section VIII, Division 1 or international equivalent, where

applicable, but at a minimum, shall be strength tested to a minimum of 1.1 times the

design pressure, subsequently leak tested, and proven tight at a pressure not less than

design pressure.

Equipment Identification. Manufacturers producing shell-and-tube evaporators for

refrigerant in the shell shall provide data in accordance with the relevant “UG”

sections of ASME B&PVC, Section VIII, Division 1 or international equivalent, but in

any case shall provide the following minimum data on a nameplate affixed to the

equipment:



3. Manufacturer’s name, preceded by the words “certified by,” if the vessel is

ASME-stamped

4. Shell side maximum allowable working pressure (MAWP) _____ at _____

temperature

5. Tube side maximum allowable working pressure (MAWP) _____ at _____

temperature

6. Shell side minimum design metal temperature (MDMT) _____ at _____ pressure

7. Tube side minimum design metal temperature (MDMT) _____ at _____ pressure





12. Type of construction (in accordance with ASME B&PVC, Section VIII,

Division 1 or international equivalent, where applicable

Installation Considerations. Installation considerations shall be in accordance with

Section 11.3.2.4.

11.3.2 Shell-and-Tube Evaporators with ammonia in tubes. Shell-and-tube evaporators shall be

in accordance with this section.


Design

11.3.2.1.1 Minimum design pressure shall be in accordance with Section 5.6.

11.3.2.1.2 Pressure Vessels coupled to shell-and-tube evaporators with ammonia in the

tubes shall comply with Chapter 12.

11.3.2.1.3 Where the tube-side inlet and outlet lines of shell-and-tube evaporators, with

ammonia in tubes, can be isolated, the tube-side shall be hydrostatic over-

pressure-relief protected in accordance with Section 15.6.

EXCEPTION: Where the tube-side of the evaporator is built and stamped in

accordance with ASME B&PVC, Section VIII, Division 1 or

international equivalent, it shall protected from overpressure

in accordance with Section 15.3.

11.3.2.1.4 The tube-side shall comply with ASME B31.5 Section 5, ASME B&PVC,


11.3.2.1.5 Heat loads from cleaning operations and process loads shall be considered when

designing the relief capacity and control of process heat exchangers.

Procedures/Testing. Shell-and-tube evaporators shall be tested in accordance with

ASME B&PVC, Section VIII, Division 1 or international equivalent, if applicable, but

at a minimum, shall be strength tested to a minimum of 1.1 times the design pressure,


Equipment Identification. Manufacturers producing shell-and-tube evaporators for

refrigerant in the tubes shall provide the data in accordance with the relevant “UG”

section of ASME Boiler and Pressure and Vessel Code, Section VIII, Division 1 or

international equivalent, where applicable, and in any case shall provide the following

minimum data on a nameplate affixed to the equipment:



3. Manufacturer’s name,(preceded by the words “certified by,” if the vessel is

ASME-stamped

4. Shell side maximum allowable working pressure (MAWP) _____ at _____

temperature

5. Tube side maximum allowable working pressure (MAWP) _____ at _____

temperature

6. Shell side minimum design metal temperature (MDMT) _____ at _____ pressure

7. Tube side minimum design metal temperature (MDMT) _____ at _____ pressure





12. Type of construction, in accordance with ASME B&PVC, Section VIII,



Installation Considerations.

11.3.2.4.1 Clearance shall be provided for the maintenance or replacement of evaporator

tubes.

11.3.2.4.2 The ambient temperatures in the area the shell-and-tube evaporator is installed

shall be considered in the design of the secondary-coolant side of the evaporator.

11.4 Plate Heat Exchanger Evaporators. Plate heat exchanger evaporators shall comply with this

section. Equipment covered by this section includes plate heat exchanger evaporators of the plate-

and-shell type, and of the plate-and-frame type in which the heat transfer plate stack is axially

contained between two pressure plates and where the plate joints may be fully elastomeric, paired

plate sets welded with adjacent sets elastomeric, fully welded, or fully nickel brazed.

11.4.1 Design



Pressure vessels coupled to plate heat exchanger evaporators, such as plate-and-shell

designed with the ammonia in a shell qualifying as a pressure vessel, shall comply

with Chapter 12.

Where the refrigerant inlet and outlet lines of ammonia-containing plate packs can be

isolated, the ammonia side of the plate pack shall be overpressure-relief protected in


EXCEPTION: Where the evaporator is not a pressure vessel, it shall be protected

from hydrostatic overpressure in accordance with Section 15.6.

Where the non-refrigerant process fluid inlet and outlet lines of plate packs can be

isolated, they shall be protected from hydrostatic overpressure in accordance with

Section 15.6 on the process side.

Heat loads from cleaning operations or process loads shall be considered when

designing the relief capacity and control of process heat exchangers.

11.4.2 Procedures/Testing. Plate heat exchanger evaporators shall be tested in accordance with

ASME B&PVC, Section VIII, Division 1 or international equivalent, if applicable, but a




11.4.3 Equipment Identification.

Manufacturers producing plate heat exchanger evaporators shall provide the

following minimum data on a nameplate affixed to the equipment:




ASME-stamped

4. Hot-side maximum allowable working pressure (MAWP) _____ at _____

temperature, where applicable

5. Cold-side maximum allowable working pressure (MAWP) _____ at _____

temperature

6. Hot-side minimum design metal temperature (MDMT) _____ at _____

pressure, where applicable

7. Cold-side minimum design metal temperature (MDMT) _____ at _____

pressure






Division 1 or international equivalent where applicable

Manufacturers producing plate heat exchanger evaporators incorporating pressure

vessels (e.g., plate-and-shell evaporators with ammonia in a shell qualifying as a

pressure vessel) shall provide data in accordance with the “UG” section of ASME

B&PVC, Section VIII, Division 1 or international equivalent, where applicable.


Clearance shall be provided for maintenance or replacement of evaporator plates.

The ambient temperatures in the area the plate heat exchanger evaporator is installed

shall be considered in the design of the secondary-coolant side of the evaporator.

11.5 Scraped (Swept) Surface Heat Exchangers. Scraped (swept) surface heat exchangers shall


11.5.1 Design


Pressure vessels coupled to scraped (swept) surface heat exchangers shall comply with

Chapter 12.


designing the relief capacity and control of scraped surface heat exchangers.


11.5.2 Procedures/Testing. Scraped (swept) surface heat exchangers shall be tested in accordance

with ASME B&PVC, Section VIII, Division 1 or international equivalent, if applicable, but

at a minimum, shall be strength tested to a minimum of 1.1 times the design pressure,


11.5.3 Equipment Identification. Manufacturers producing scraped (swept) surface heat

exchangers for refrigerant in the shell shall provide data in accordance with the relevant

“UG” sections of ASME B&PVC, Section VIII, Division 1 or international equivalent, but in

any case shall provide the following minimum data on a nameplate affixed to the equipment:



3. Manufacturer’s name, preceded by the words “certified by,” if the vessel is ASME-

stamped

4. Shell maximum allowable working pressure (MAWP) _____ at _____ temperature

5. Shell minimum design metal temperature (MDMT) _____ at _____ pressure




9. Test pressure, note test type; hydraulic or pneumatic)

10. Type of construction, in accordance with ASME B&PVC, Section VIII, Division 1 or

international equivalent, where applicable


Clearance shall be provided for the maintenance or replacement of equipment.

The ambient temperatures in the area the scraped (swept) surface heat exchanger is

installed shall be considered in the design.

11.6 Jacketed Tanks. Jacketed tanks shall comply with this section.

11.6.1 Design



Pressure vessels coupled to jacketed tanks evaporators shall comply with Chapter 12.

Where the refrigerant inlet and outlet lines of the jacketed tank ammonia-containing

evaporator can be isolated, the ammonia side of the evaporator shall be overpressure-

relief protected in accordance with Section 15.3.

EXCEPTION: Where the jacketed tank evaporator is not a pressure vessel, it shall

be protected from hydrostatic overpressure in accordance with

Section 15.6.


designing the relief capacity and control of jacked tanks.


11.6.2 Procedures/Testing. Jacketed tanks shall be tested in accordance with ASME B&PVC,

Section VIII, Division 1 or international equivalent, if applicable, but at a minimum, shall be

strength tested to a minimum of 1.1 times the design pressure, subsequently leak tested, and

proven tight at a pressure not less than design pressure.

11.6.3 Equipment Identification.

Manufacturers producing jacketed tanks shall provide the following minimum data on

a nameplate affixed to the equipment:




ASME-stamped

4. Maximum allowable working pressure (MAWP) _____ at _____ temperature,

where applicable

5. Minimum design metal temperature (MDMT) _____ at _____ pressure, where

applicable







Manufacturers producing jacketed tanks incorporating pressure vessels, such as plate-

and-shell evaporators with ammonia in a shell qualifying as a pressure vessel, shall

provide data in accordance with the “UG” section of ASME B&PVC, Section VIII,

Division 1 or international equivalent, where applicable.


The ambient temperatures in the area the jacketed tank is installed shall be considered

in the design.


Chapter 12. Pressure Vessels

12.1 General. Pressure vessels shall comply with this chapter.

12.2 Design

12.2.1 Minimum design pressure shall be in accordance with Section 5.6.

EXCEPTION: Where ammonia liquid is to be transferred from pressure vessels by

pressurized ammonia gas, the pressure vessel design pressure shall

accommodate the maximum possible transfer pressure and take into

account the lowest possible coincident metal temperature.

12.2.2 Pressure vessels exceeding 6 in [15 cm] inside diameter shall comply with ASME B&PVC,

Section VIII, Division 1 or international equivalent covering the requirements for design,

fabrication, inspection and testing during construction of unfired pressured vessels. Pressure

vessels having inside diameters less than 6 in [15 cm] shall require ultimate strength in

accordance with Section 5.15.2.

12.2.3 For vessels larger than 6” [15.24 cm] inside diameter but less than 10 cubic feet [0.28 m³] in

internal volume, the pressure relief valve connection shall not be less than ¾” [1.91 cm]

piping or a ½” [1.27 cm] coupling. For vessels with an internal volume of 10 cubic feet [0.28

m³] or larger, the pressure relief valve connection shall not be less than 1” [2.54 cm] piping

or a ¾” [1.91 cm] coupling.

12.2.4 Pressure vessels shall be provided with one or more openings for the attachment of pressure

relief devices, as required by Section 15.4.2.

12.2.5 The heads of pressure vessels shall be hot-formed or stress relieved after cold-forming.

EXCEPTION: Vessels primarily containing oil, including but not limited to oil

separators, oil filters, oil coolers and oil pots.

12.2.6 *The designer shall specify whether pressure vessels are required to be treated to prevent

stress corrosion cracking.

12.2.7 A vessel shall be designed and stamped with a minimum design metal temperature no higher

than its lowest expected operating temperature.

12.2.8 In applications where pressure vessels are subject to external corrosion as determined by the

owner or his designated agent, the vessels shall be designed and specified with a minimum of

1/16" [1.6 mm] corrosion allowance. The external corrosion allowance is in addition to the

minimum vessel thickness as required by ASME B&PVC, Section VIII, Division 1 or

international equivalent.


12.2.9 Pressure vessel shall be piped for compliance with the pressure and temperature limitations

specified on the name plate data.

12.2.10 Alterations to pressure vessels shall be allowed only as directed by the AHJ. The alterations

shall only be performed by a qualified service approved by the AHJ. A re-stamping shall be

applied as required by the AHJ when the modification is completed.

12.3 Procedures/Testing. Pressure vessels shall be tested in accordance with ASME B&PVC, Section

VIII, Division 1 or international equivalent, if applicable, but at a minimum, shall be strength

tested hydrostatically to a minimum of 1.3 times the design pressure or air tested to a minimum of

1.1 times the design pressure, subsequently leak tested, and proven tight at a pressure not less than

design pressure.

12.4 Equipment Identification

12.4.1 Manufacturers producing pressure vessels shall provide data in accordance with the

requirements of the relevant “UG” sections of ASME B&PVC, Section VIII, Division 1 or

international equivalent, but in any case shall provide the following minimum data on a

nameplate affixed to the equipment as specified in Section 12.4.2:



3. Manufacturer’s name, preceded by the words “certified by,” if the vessel is ASME

stamped

4. Maximum allowable working pressure (MAWP) _____ at _____ temperature

5. Minimum design metal temperature (MDMT) _____ at _____ pressure


7. Year of manufacture


9. Type of construction, in accordance with ASME B&PVC, Section VIII, Division 1 or

international equivalent, where applicable

10. A stamp shall be affixed to the equipment that includes the minimum design metal

temperature (MDMT) that it is operated at in accordance with ASME B&PVC,


12.4.2 Nameplate Mounting

Nameplates shall comply with Section 5.16.4.

If any pressure vessel is insulated, the name plate shall be mounted on an approved

stand-off so it is not covered or the insulation at the nameplate location on the pressure

vessel shall be removable to allow for name plate inspection.


12.5 Pressure Vessel Installation Considerations.

12.5.1 Clearance shall be provided for maintenance.

12.5.2 Physical protection shall comply with Section 7.2.5.

12.5.3 Pressure vessels supported from the ground shall rest on a concrete or other foundation or

shall come with a support for sitting directly on and anchoring to the foundation.


Chapter 13. Piping

13.1 *General. Piping shall comply with this chapter. The design, fabrication, examination, and testing

of the piping, whether fabricated in a shop or as a field erection, shall comply with ASME B31.5,

unless otherwise provided by this chapter.

13.2 Pipe, Tubing, Fittings, and Flanges

13.2.1 *Material. Piping materials shall comply with ASME B31.5 except as specified in this

section.

ASTM A53-Type F pipe and cast iron or wrought iron pipe shall not be used for

closed-circuit ammonia refrigeration systems.

Zinc, copper, and copper alloys shall not be used in contact with or for containment of

ammonia. Copper-containing anti-seize and/or lubricating compounds shall not be

used in ammonia piping joints.

13.2.2 *Minimum Pipe Wall Thickness. Minimum pipe wall thickness shall be based on the

properties of the selected pipe material, the design working pressure and shall comply with

the requirements of ASME B31.5.

EXCEPTIONS: 1. Carbon and stainless steel threaded pipe shall be minimum

Schedule 80 for all sizes.

2: Carbon steel pipe 1-1⁄2 inch and smaller shall be minimum

Schedule 80.

3. Stainless steel pipe 1-1⁄2 inch and smaller shall be minimum

Schedule 40.

13.2.3 *Minimum Tubing Wall Thickness

Minimum tubing wall thickness shall be based on the properties of the selected

material and the greater of the design working pressure or the requirement specified by

the manufacturer of the compression ferrule used for the fitting connection.

The use of carbon steel tubing and compression fittings shall be limited to

compressors, compressor packages, and packaged systems.

13.2.4 Pipe Fittings

Butt weld fittings shall match pipe schedules.

EXCEPTION: The schedule of butt weld fittings joining pipe at a wall

thickness change shall match the schedule of the thicker wall

pipe. The internal diameter of the end of the fitting connecting

to the thinner wall pipe shall be machined or ground to match.


All socket weld and screwed fittings shall be minimum Class 3000 and manufactured

from forged or cast steel.

Threaded joints shall not be used for refrigerant piping larger than 2 inches in

diameter.

Threaded piping shall be minimum Schedule 80.

13.2.5 Pipe Flanges

Flanges in accordance with ANSI ASME Standard B16.5 shall comply with the

requirements of ASME B31.5, be raised face type and the flange class shall be based

on the design working pressure and the maximum working temperature at the design

working pressure.

Gaskets shall be correctly dimensioned for the flange set.

13.3 *Refrigerant Valves and Strainers. Valves used in ammonia-containing and lubricant-containing

service shall comply with this section.

EXCEPTIONS: 1. Valves within the ammonia-containing envelope of other equipment, such

as slide valves in screw compressors.

2. Safety relief valves.

13.3.1 Required Shut-off Valve Locations. Shut-off valves shall be installed in the refrigerant

piping at the following locations:

1. At the inlet and outlet of a positive-displacement-type compressor, compressor unit, or

condensing unit.

2. At the main feed inlets and outlets of individual refrigeration equipment loads.

3. At the refrigerant inlet and outlet of a pressure vessel containing liquid ammonia and

having an internal gross volume exceeding three (3) cubic feet (0.085 cubic meters).

EXCEPTIONS: 1. In lieu of providing shut-off valves at each piece of serviceable

equipment, packaged systems and portions of built-up systems shall be

permitted to have pump-down arrangements that permit the safe removal

or isolation of ammonia for servicing one or more pieces of equipment.

2. Shut-off valves are not required between a refrigeration equipment load

and a pressure vessel containing liquid ammonia where a single load is

piped into a single pressure vessel, such as a surge-fed evaporator piped

into a surge drum.

3. Packaged systems that incorporate subsystem isolation valves shall not

require more than one shut-off valve on each ammonia-containing pipe

connecting any two parts of a system.


13.3.2 Valves in Equipment and System Design

Where the manufacturer’s specifications indicate that a particular vertical, horizontal

or rotational orientation is required for proper operation of a valve, the system design

shall indicate the required orientation.

EXCEPTION Where the system design provides for a valve to be installed with

a different orientation.

*Where a valve is deliberately specified for use with the directional indicator marked

by the manufacturer being opposite of the normal direction of flow, the system design

shall specify the intended installation direction.

Valve gasket materials shall match valve manufacturer’s specifications and be of the

thickness specified.

13.3.3 * Where a check valve is installed upstream of other automatic valves, pressure relief shall be

provided. Provision for liquid removal to facilitate maintenance shall be located downstream

of the check valve. Hydrostatic overpressure protection shall comply with Section 15.6.

13.3.4 Strainers shall be fitted with provision for ammonia removal to facilitate maintenance.

13.3.5 *Shut-off valves used to isolate equipment or devices from other portions of the system for

the purpose of maintenance or repair shall be capable of being locked out.

13.3.6 Shut-off valves connecting ammonia-containing equipment or piping to atmosphere shall be

capped, plugged, blanked, or locked closed during shipping, testing, operating, servicing, or

standby conditions when they are not in use, in accordance with IIAR 5.

13.3.7 Valves required for system emergency shutdown procedures shall be readily accessible and

identified in accordance with Sections 5.16.3 and 6.3.3.2. Other valves shall be accessible in

accordance with Section 6.3.3.1 if installed in a machinery room.

13.4 *Piping, Hangers, Supports Isolation

13.4.1 *Piping hangers and supports shall carry the weight of the piping and any additional expected

loads.

13.4.2 Refrigerant piping shall be isolated and supported to prevent damage from vibration, stress,

corrosion and physical impact.

13.4.3 Sway bracing shall be included required by the Building Code.

13.4.4 Threaded hot rolled steel hanger rods shall be permitted.

13.4.5 Anchors, their attachment points and attachment methods shall designed to support applied

loads.

13.4.6 Mechanically expanded concrete anchor bodies shall not be adjusted or axially spun after

being set.


13.4.7 For piping that is insulated, supports shall be designed or the insulation shall be selected to

avoid damage to the insulation from compression.

13.5 *Location of Refrigerant Piping

13.5.1 Refrigerant piping crossing walkway areas in a building shall be not be less than 7.25 feet

(2.2 m) above the floor.

EXCEPTION: Where approved, piping shall be permitted to be located less than7.25

feet (2.2 m) above the floor provided that it is placed against the ceiling

of such space.

13.5.2 Refrigerant piping shall not obstruct a means of egress.

13.5.3 Refrigerant piping shall not be placed in an elevator shaft, dumbwaiter shaft, or other shaft

containing a moving object.

13.5.4 Refrigerant piping shall not be installed in a stair, landing, or means of egress that is enclosed

and is accessible to the public.

13.5.5 Refrigerant piping shall be permitted to be installed underground provided that the piping is

protected from corrosion.

13.5.6 Refrigerant piping installed in concrete floors shall be encased in pipe duct.


Chapter 14. Packaged Systems and Equipment

14.1 General

14.1.1 Packaged systems and equipment shall comply with this chapter. Such packages shall be

permitted to be enclosed or unenclosed. Equipment enclosures shall comply with

Section 5.18.

14.1.2 Packaged systems and equipment shall be designed, constructed and installed in

accordance with the applicable provisions of Chapter 4 through Chapter 7.

14.1.3 *Packaged systems shall be ventilated based on the intended operation of the equipment,

as specified by the manufacturer. In addition, emergency mechanical ventilation shall be

provided where required by any of the following:

1. Package systems located in machinery rooms shall be included as machinery room

equipment. Emergency ventilation for machinery rooms shall be in accordance with

Section 6.14.

2. Package systems located indoors and outside of a machinery room in accordance with

Section 4.2.3 Item 4, shall comply with Section 7.3.1.

3. Package systems located outside that are designed for human occupancy shall comply

with Section 7.3.2. Package systems located outside that are not designed for human

occupancy shall not require ventilation.

14.1.4 Equipment and devices incorporated into packaged systems shall comply with the

applicable provisions of Chapter 8 through Chapter 17.

14.2 Design

14.2.1 The structure of the package shall be designed to support the operating weight of included

equipment.

14.2.2 The structure of the package shall be designed to withstand the stresses caused by shipping

and rigging. Temporary supports and bracing shall be permitted. Rigging instructions shall be

provided to accommodate the install of the structure.

14.2.3 The structure of the package shall be designed to withstand loads or stresses that will be

imposed on the package after installation and start-up, including environmental factors such

as snow, ice, wind, and seismic forces.

14.2.4 Packaged equipment shall have valved pump-out connections for removal of ammonia.

14.2.5 Packages shall be designed for use in the lowest expected ambient temperatures in which

they will operate.

14.2.6 Packages shall be designed for use in the highest expected ambient temperatures in which

they will operate.

14.2.7 *Access shall be provided for manually operated valves. Isolation valves identified as being

part of a system emergency shutdown procedures shall be directly operable or chain-operated

from a permanent work surface. Valve tagging shall comply with Section 5.16.3


14.2.8 Pipes shall be marked in accordance with Section 5.16.5.

14.2.9 Equipment shall be labeled in accordance with Section 5.16.2.

14.2.10 Packages shall be equipped with lighting, or the area with refrigeration equipment shall be

equipped with light fixtures delivering a minimum of 30 foot-candles [320 lumens/m2] at the

working level, 36 inches (0.91 m) above a floor or platform.

14.2.11 Enclosed packages that require entrance for service, maintenance, inspection or operation

shall have lighting control located at entrances.

EXCEPTION: Where continuous lighting exists, the lighting control does shall not be

required to be located at the entrances.

14.3 Fabrication

14.3.1 Equipment shall be set on the package in accordance with the manufacturer’s

recommendations, including proper support and clearances.

14.3.2 Equipment and piping shall be supported to withstand transporting and rigging. Temporary

supports and bracing shall be permitted.

14.3.3 Stationary or temporary rigging points shall be provided as required to position the package.

14.3.4 Piping shall be pressure tested after fabrication, and leaks shall be repaired. The package

shall be shipped with a holding charge of dry nitrogen or provided with another means

approved by the manufacturer to allow validation that leakage has not occurred during

shipping or subsequent storage prior to installation.

14.3.5 Electrical equipment and wiring shall be installed in accordance with the Electric Code.

14.3.6 Gas fuel devices and equipment used with refrigeration systems in the package shall be

installed in accordance with Mechanical Code.

14.4 Alarms and Detection. Detection and alarms for packaged systems shall comply with the

following. Where required, the detection and alarm system shall comply with Chapter 17.

1. Package systems located in machinery rooms shall be included as machinery room

equipment. Detection and alarms shall be comply with Section 6.13

2. Package systems located indoors and outside of a machinery room, as permitted by Section

4.2, shall be provided with Level 2 detection and alarms in accordance with

Section17.7.2.7.2.4

3. Package systems located outdoors that are not intended for human occupancy shall not

require ammonia detection or alarms.


Chapter 15. Overpressure Protection Devices

15.1 *General. Pressure relief devices provided for the purpose of relieving excess pressure due to fire

or other abnormal conditions shall comply with this Chapter.

15.2 *Pressure Relief Devices

15.2.1 Refrigeration system shall be protected by not less than one pressure relief device.

15.2.2 Pressure relief devices provided for vessels constructed in accordance with ASME B&PVC,

Section VIII, Division 1 or international equivalent shall comply with that code or equivalent

and other applicable requirements of this Standard.

15.2.3 The system design shall specify that pressure relief devices is accessible for inspection and

repair.

15.2.4 *Pressure relief devices intended for vapor service shall be connected above the highest

anticipated liquid ammonia level.

EXCEPTIONS: 1. Hydrostatic overpressure relief protection shall comply with

Section 15.6.

2. The connection to oil drain pot vessels and similar applications,

connect shall be at the highest point.

15.2.5 Where relief valves are located in refrigerated spaces, precautions shall be taken to prevent

moisture migration into the valve body or relief vent line.

15.2.6 The seats and discs of pressure-relief devices shall be constructed of material that resists

ammonia corrosion and other chemical action caused by the ammonia. Seats and discs shall

be limited in distortion, by pressure or other cause, to a set pressure change of not more than

5% from the set pressure relief.

15.2.7 Setting of Pressure Relief Devices

The set pressure for a pressure relief valve shall not exceed the design pressure of

equipment protected by the valve.

The set pressure of a rupture member used in series with a relief valve shall not exceed

the design pressure of the equipment protected by the rupture member.

*Provision shall be made to detect pressure build up between the rupture member and

the relief valve due to leakage through the upstream relief device.

15.2.8 Marking of Relief Devices

Pressure relief valves for ammonia-containing equipment shall be set and sealed by

the manufacturer. Pressure relief valves shall be marked by the manufacturer with the

data required in ASME B&PVC, Section VIII, Division 1 or international equivalent.

Resetting of a pressure relief valve shall be performed by the manufacturer or a

company holding a valid testing certificate for this work.


The capacity in SCFM [m3/s] or in lb air/min [kg air/min] shall be stamped on valves

or available on request.

Rupture members for ammonia-containing pressure vessels shall be marked with the

data required in ASME B&PVC, Section VIII, Division 1 or international equivalent.

15.3 Pressure Relief Protection

15.3.1 Pressure vessels and other types of equipment built and stamped in accordance with ASME

B&PVC, Section VIII, Division 1 or international equivalent shall be provided with pressure

relief protection.

15.3.2 Pressure vessels intended to operate completely filled with liquid ammonia and that are

capable of being isolated by stop valves from other portions of a refrigeration system shall be

protected with a certified hydrostatic service relief device as required by ASME B&PVC

Section VIII, Division 1 or international equivalent. Hydrostatic overpressure relief shall


15.3.3 Pressure relief devices shall be sized in accordance with Section 15.3.7.

15.3.4 Pressure vessels less than 10 ft3 [0.3 m3] internal gross volume shall be protected by one or

more pressure relief devices.

15.3.5 Pressure vessels of 10 ft3 [0.3 m3] or more internal gross volume shall be protected by one or

more of the following:

1. One or more dual pressure relief devices installed with a three-way valve to allow

testing or repair. Where dual relief valves are used, each valve shall comply with

Section 15.3.7. Dual relief valves shall be set to a fully seated position, with one side

open and one side closed.

Where multiple dual relief valve assemblies are used, the sum of the capacities of the

pressure relief devices actively protecting the vessel shall be required to equal or

exceed the requirements set forth in Section 15.3.7.

2. A single pressure relief device, provided that: 1) The vessel can be isolated and

pumped out; 2) The relief valve is located on the low side of the system; and 3) Other

pressure vessels in the system shall be separately protected in accordance with Section

15.3.7.


15.3.6 Where pressure relief valves are discharged into other portions of the refrigeration system,

the portion of the system receiving the internal discharge shall be equipped with pressure

relief devices capable of discharging the increased capacity in accordance with Section 15.3.7

and the pressure relief valves discharging into the system shall be with one of the following

types:

1. A pressure relief valve not appreciably affected by back pressure, or

2. A pressure relief valve affected by back pressure, in which case the valve’s set

pressure added to the set pressure of the system pressure relief device shall not exceed

the maximum allowable working pressure of any equipment being protected and shall

comply with the following:

2.1. The pressure relief valve that protects the higher pressure vessel shall be

selected to deliver capacity in accordance with Section 15.3.7 without

exceeding the minimum design pressure of the higher pressure vessel

accounting for the change in mass flow capacity due to the elevated back

pressure.

2.2. The capacity of the pressure relief valve protecting the part of the system

receiving a discharge from a pressure relief valve protecting a higher pressure

vessel shall be at least the sum of the capacity required in Section 15.3.7 plus

the mass flow capacity of the pressure relief valve discharging into that part of

the system.

2.3. The design pressure of the body of the relief valve used on the higher pressure

vessel shall be rated for operation at the design pressure of the higher pressure

vessel in both pressure containing areas of the valve.

EXCEPTION: Where hydrostatic overpressure protection relief devices are discharged

into other portions of a refrigeration system that are protected by

pressure relief devices design to relieve vapor in accordance with

Section 15.3, the capacity of the hydrostatic overpressure protection

relief devices shall not be required to be summed with the vapor

capacity required in Section 15.3.7.

15.3.7 Pressure Relief Device Capacity Determination

*Pressure relief devices shall have sufficient mass flow carrying capacity to limit the

pressure rise in a protected equipment to prevent its catastrophic failure. The minimum

required relief capacity shall depend on the equipment being protected and the

scenarios under which overpressure is being created.

The following scenarios shall be considered when determining the pressure relief

device capacity for ammonia containing equipment. It is permissible to use

manufacturer’s data when determining relief requirements. All applicable scenarios

shall be considered and the capacity of the pressure relief device shall be based on the

scenario with the largest capacity requirements:


15.3.7.2.1 Overpressure due to External Fire

i. Pressure Vessels:

The required discharge capacity of a pressure relief device for each pressure vessel shall

be determined by the following equation:

C = ƒ ∙D∙L (lbm/min)

[C = ƒ∙ D∙L [kg/s]]

Where

C = required discharge capacity of the relief device, lbm air/min [kg/s]

ƒ = capacity factor of the relief device which is 0.5 [0.04] for ammonia

[0.5 is in inch-pounds (IP), 0.04 is in International System of Units (SI)]

D = outside diameter of vessel, ft [m]

L = length of vessel, ft [m].

When one pressure relief device is used to protect more than one pressure vessel, the

required capacity shall be the sum of the capacities required for each pressure vessel.

ii. Oil Separators:

The required discharge capacity for each oil separator shall be determined by the

following equation:

Cr,os = ƒ·D∙L (lbm/min)

[Cr,os = ƒ∙ D∙L [kg/s]]

Where

Cr,os = required discharge capacity of the relief device, lbm air/min [kg/s]


D = outside diameter of the oil separator, ft (m)

L = length of the oil separator, ft (m)


iii. Plate Heat Exchangers

The capacity of the pressure relief device for plate heat exchangers shall be based on the

largest projected area of the exchanger using the following equation:

Cr,plate HX = ƒ · √𝐿2 + 𝑊2 ∙ H (lbm/min)

[Cr,plate HX = ƒ · √𝐿2 + 𝑊2 ∙ H, [kg/s]]

Where

Cr,plate HX = Minimum required relief device capacity for plate heat exchanger (lbm/min

of air) [kg/s]

ƒ = relief device capacity factor which is 0.5 [0.04] for ammonia

L = length of the plate pack (ft) [m]

W = width of the plate pack (ft) [m]

H = Height of the plate pack (ft) [m]

iv. Shell and Tube Heat Exchangers

The capacity of the pressure relief device for shell and tube heat exchangers shall be

based on the sum of the capacities required for the heat exchanger and the surge drum, if

provided, as follows:

C = ƒ∙(Dv ∙ Lv + Ds ∙ Ls) (lb/min)

[C = ƒ∙(Dv ∙ Lv + Ds ∙ Ls) [kg/s]]

Where

C = required discharge capacity of the relief device, lb air/min [kg/s]


Dv = outside diameter of the main vessel portion of the shell and tube heat exchanger,

ft [m]

Lv = length of main vessel portion of the shell and tube heat exchanger, ft [m].

Ds = outside diameter of the surge drum, ft [m]

Ls = length of the surge drum, ft [m].


v. Product Storage Tanks

For product storage tanks with cooling jackets, the capacity of the pressure relief device

shall be based on the diameter of the storage tank and the height of the cooling jacket as

follows:

Cr,tank = ƒ · D ∙ H (lbm/min)

[Cr,tank = ƒ · D ∙ H [kg/s]]

Where

Cr,tank = required discharge capacity of the relief device, lb air/min [kg/s]


D = outside diameter of the tank, ft (m)

H = height of the active portion of the heat exchanger (distance between ammonia

supply and return) ft (m)

15.3.7.2.2 *Potential for Overpressure due to Blocked Outlet

i. Positive Displacement Compressor Protection. Pressure relief protection for

positive displacement compressors shall comply with Section 8.3.1.

ii. Oil Cooling Heat Exchangers*The designer shall evaluate potential overpressure

scenarios.

iii. Hydrostatic overpressure relief Protection.*Hydrostatic overpressure relief shall


15.3.7.2.3 Potential for Overpressure due to Internal Heat Load.* The designer shall

evaluate potential overpressure scenarios.

15.3.7.2.4 Other Potential Overpressure Scenarios. The designer shall evaluate other

potential overpressure scenarios as applicable to the specific equipment being

protected.

15.3.8 *Where combustible material is stored within 20 feet (6.1 m) of a pressure vessel, the relief

device capacity factor, f, in the formulas shall be increased to f = 1.25 [f = 0.1].

15.3.9 The rated discharge capacity of a pressure relief valve shall be determined in accordance with

ASME B&PVC, Section VIII, Division 1 or international equivalent. The capacity marked on

the nameplate shall be in lb/min air or in standard ft3/min (SCFM) of air at 60°F (SCFM x

0.0764 = lb/min of dry air).


15.3.10 The rated discharge capacity of a rupture member discharging under critical flow conditions

shall be determined by the following equations:

C = 0.64 P1d2 (lb/min)

d = 1.25 (C/P1)0.5 (in)

[C = 1.1 x 10-6 P1d2 (kg/s)]

[d = 959 (C/P1)0.5 (mm)]

Where

C = rated discharge capacity in lb/min [kg/s] of air

d = smallest of the internal diameter of the inlet pipe, retaining flanges or rupture

member in inches [mm]

P1 = rated pressure (psig) x 1.1 + 14.7 psi

[P1 = rated pressure [kPa gauge] x 1.1 + 101.3 kPa]

There shall be provisions to prevent plugging the piping in the event the rupture member

relieves.

15.4 Pressure Relief Device Piping. Piping for relief of vapor shall comply with this section. Relief

valve piping that discharges external to the refrigeration system is not part of the refrigeration

system.

15.4.1 Stop valves shall not be installed in the inlet piping of pressure relief devices. Where installed

in the outlet piping of pressure relief devices, the pressure drop effects of full area stop valves

shall be taken into account in the engineering of the relief vent piping system. Where used,

stop valves shall be locked open whenever any upstream relief device is in service.

15.4.2 The area of the opening through pipe; fittings; and pressure relief devices, if installed,

including 3-way valves; between a pressure vessel connection as provided in Section 12.2.3

and its pressure relief valve shall be not less than the area of the pressure relief valve inlet.

This upstream system shall be such that the pressure drop will not reduce the relieving

capacity below that which is required. Compressor vessel connections shall comply with

Section 8.3.1.


15.4.3 Discharge piping from pressure relief devices shall be steel pipe minimum schedule 40 for

pipe sizes up to 6” and minimum schedule 20 for pipe sizes 8” and larger. The relief piping

shall comply with the ferrous material requirements of ASME B31.5.

EXCEPTIONS: 1. Relief piping shall be permitted to be galvanized or un-galvanized

ASTM A53-Type F. When these grades of un-galvanized pipe are used,

the pipe shall be clearly identified using paint striping or another method

or shall be segrega3ted to prevent use in a refrigeration system.

2. Malleable iron ASTM A197 fittings shall be permitted for discharge

relief piping.

15.4.4 The size of the discharge pipe from a pressure relief device shall not be less than the outlet

size of the pressure relief device. The minimum size and total equivalent length of common

discharge piping downstream from each of two or more relief devices shall be determined

based on the sum of the discharge capacities of all relief devices that are expected to

discharge simultaneously, with due allowance for the pressure drop in downstream sections.

15.4.5 Where piping in the system and other equipment required to comply with this section could

contain liquid ammonia that can be isolated from the system during operation or service,

Section 15.6 shall apply.

15.4.6 Discharge piping shall be supported in accordance with Section 13.4.

15.4.7 Relief piping shall be used only for relieving vapor from refrigerant relief valves. Relief

piping shall not be used to relieve discharge from hydrostatic overpressure-relief devices or

any other fluid discharges, such as secondary coolant or oil.

15.5 Discharge from Pressure Relief Devices

15.5.1 *Atmospheric Discharge Pressure relief devices shall discharge vapor directly to the

atmosphere outdoors in accordance with this section.

EXCEPTION. In lieu of relieving directly to atmosphere, the following methods of

discharging ammonia from pressure relief devices shall be permitted

where approved by the AHJ:

1. Discharge through a treatment system.

2. Discharge through a flaring system in accordance with Section

15.5.2.

3. Discharge through a water diffusion system in accordance with

Section 15.5.3.

4. Discharge using other approved means.

The maximum length of the discharge piping installed on the outlet of pressure relief

devices and fusible plugs discharging to the atmosphere shall be determined in

accordance with this section.


15.5.1.1.1 *The design back pressure due to flow in the discharge piping at the outlet of

pressure relief devices and fusible plugs, discharging to atmosphere, shall be

limited by the allowable equivalent length of piping determined by Equation

15.5.1.1(1) or 15.5.1.1(2).

Equation 15.5.1.1.1(1): Allowable relief discharge piping length, English units

f

PP

d

fC

PPdL

o

r 6

ln2146.0 2

2

2

2

2

0

5


Equation 15.5.1.1.1(2): Allowable relief discharge piping length, SI units

f

PP

d

fC

PPdL

o

r 500

ln104381.7 2

2

2

2

2

0

515

Where

L = equivalent length of discharge piping, ft [m];

Cr = rated capacity as stamped on the relief device in lb/min [kg/s], or in SCFM

multiplied by 0.0764, or as calculated in ANSI/ASHRAE 15, Section 9.7.7 for a rupture

member or fusible plug, or as adjusted for reduced capacity due to piping as specified by

the manufacturer of the device, or as adjusted for reduced capacity due to piping as

estimated by an approved method;

ƒ = Moody friction factor in fully turbulent flow (See Appendix A.15.5.1.1.1);

d = inside diameter of pipe or tube, in [mm];

ln = natural logarithm;

P2 = absolute pressure at outlet of discharge piping, psi [kPa];

P0 = allowed back pressure (absolute) at the outlet of pressure relief device, psi [kPa].

For the allowed back pressure (P0), use the percent of set pressure specified by the

manufacturer, or when the allowed back pressure is not specified, use the following

values, where

P is the set pressure:

a. for conventional relief valves, 15% of set pressure, P0 = (0.15 P) + atmospheric

pressure;

b. for balanced relief valves, 25% of set pressure, P0 = (0.25 P) + atmospheric

pressure;

c. for rupture members, fusible plugs, and pilot operated relief valves, 50% of set

pressure, P0 = (0.50 P) + atmospheric pressure.

For fusible plugs, P is the saturated absolute pressure for the stamped temperature

melting point of the fusible plug or the critical pressure of the ammonia, whichever is

smaller, psi [kPa] and atmospheric pressure is at the elevation of the installation above

sea level. A default value is the atmospheric pressure at sea level, 14.7 psi [101.325 kPa].

The termination of pressure relief device discharge piping relieving to atmosphere

shall be not less than 15 feet [4.6 m] above grade and not less than 20 feet [6.1 m]

from windows, ventilation intakes, or exits.


The discharge termination from pressure relief devices relieving to atmosphere shall

not be less than 7.25 feet [2.2 m] above the roof. Where a higher adjacent roof level is

within 20 feet [6.1 m] horizontal distance from the relief discharge, the discharge

termination shall not be less than 7.25 feet [2.2 m] above the height of the higher

adjacent roof.

Discharge piping shall be permitted to terminate 7.25 feet [2.2 m] above platform

surfaces, such as upper condenser catwalks, and roofs that are occupied only during

service and inspection.

The termination of the discharge shall be directed vertically upward and arranged to

avoid spraying ammonia on persons in the vicinity.

The termination point of the relief vent discharge shall have a provision to block

foreign material or debris from entering the discharge piping.

Discharge piping from pressure relief devices discharging to atmosphere shall have a

provision for draining moisture from the piping.

15.5.2 Flaring Systems. Flaring systems, if installed, shall be tested to demonstrate compliance

with the design.

15.5.3 Discharge Through a Water Diffusion Tank. Where pressure relief devices discharge to a

water tank, the tank shall be sized for containing one gallon of water for each pound of

ammonia (8.3 liters of water for each kilogram of ammonia) that would be released in one

hour from the largest relief device connected to the discharge pipe. The water shall be

prevented from freezing. The discharge pipe from the pressure-relief device shall distribute

ammonia in the bottom of the tank but no lower than 33 feet (10 m) below the maximum

liquid level. The tank shall be large enough to contain the volume of water and ammonia

without overflowing.

15.6 Equipment and Piping Hydrostatic Overpressure Protection

15.6.1 *Protection Required. Protection against overpressure due to thermal hydrostatic expansion

of trapped liquid ammonia shall be provided for equipment and piping sections that can be

isolated and can trap liquid ammonia in an isolated section in any of the following situations:

1. Automatically during normal operation.

2. Automatically during shut down by any means, including alarm or power failure.

3. During planned isolation for standby or seasonal conditions.

4. Due to an equipment or device fault.

Exception: If trapping of liquid with subsequent thermal hydrostatic expansion is only

possible during maintenance or service operations, engineering or

administrative controls, or both, shall be permitted as the means of relieving or

preventing overpressure.


15.6.2 Protection Method. Where protection against overpressure due to thermal hydrostatic

expansion of trapped liquid ammonia is required, one or both of the following mitigations

methods shall be used:

1. Provide a static relief device or check valve relieving to another part of the closed-circuit

system.

2. Provide an expansion compensation device.

15.6.3 Manual Isolation. Manual isolation of equipment and piping sections shall only be

performed by personnel who are authorized to perform this service. Prior to and during the

service, precautions shall be taken to protect against overpressure due to thermal hydrostatic

expansion of trapped liquid ammonia.

Where a Lockout/Tagout procedure is required for the energy control, the procedure

and training shall be in compliance with 29 CFR 1910.147.

15.6.4 Use of Static Pressure-relief Valves. As required by Section 13.3.5, static pressure-relief

valves shall not be used as shut-off valves.


Chapter 16. Instrumentation and Controls

16.1 General

16.1.1 Scope. Instrumentation and controls shall comply with this chapter.

16.1.2 Operating Parameter Monitoring. Instruments and controls shall be provided to indicate

operating parameters of the refrigeration system and equipment and provide the ability to

manually or automatically control the starting, stopping and operation of the system or

equipment. The instruments and controls shall provide notice if the system’s critical

operating parameters, as determined by the owner or operator have been exceeded.

16.1.3 Documentation. The function, sequence and operating design parameters of each provided

control shall be obtained or documented by the owner or operator. The owner or operator

shall maintain such documentation in a location that is accessible at the site.

16.1.4 *Monitoring an Ammonia Release During a Power Failure A means shall be provided for

monitoring the concentration of an ammonia release in the event of a power failure.

16.1.5 *Restricted Access to Safety Settings. Changing of safety settings shall be limited to

authorized personnel only. Changing of system operational settings shall not permit or affect

changes to safety settings.

16.1.6 Electrical Control Systems. Electrical control systems shall comply with the Electrical

Code.

16.1.7 Ultimate Strength. The pressure-containing envelope maximum allowable working pressure

of instruments and visual liquid level indicators shall be equal to or greater than the design

pressure of the system or subsystem in which they are installed.

16.2 Visual Liquid Level Indicators: Visual liquid level indicators, including but not limited to glass

bull’s eyes, flat “armored glass” linear sight glasses or sight columns and pressure gauges, shall


16.2.1 Design and Selection

*Design of visual liquid level indicators shall be in accordance with one or more of the

following:

1. Comply with the ultimate strength requirement in Section 16.1.7.

2. Use a performance-based pressure-containment design substantiated by either

proof tests as described in ASME B&PVC, Section VIII, Division 1, Section

UG-101 or international equivalent, or an experimental stress analysis.

The design pressure shall not be less than the pressure required by Section 5.6.

Sight glasses and linear liquid level indicators shall not be installed in areas with a risk

of repeated thermal expansion or where there is a risk of liquid hammer.


16.2.2 Damage Protection. Visual liquid level indicators used to observe ammonia level, such as in

a vessel or heat exchanger, shall be designed and specified for installation in a manner that

provides protection from physical damage.

16.2.3 *Linear Liquid Level Indicators. Linear liquid level indicators shall be fitted with internal

check-type shutoff valves. Protection against accidental breakage of the glass tube from any

direction shall be provided for the entire length of the tube.

EXCEPTION: Liquid-level-indicators using bull's-eye type sight glasses.

16.2.4 Bull’s Eye Sight Glasses. Bull’s eye sight glasses shall be verified as compatible for use

with ammonia, and the thickness, diameter and type of glass used shall be verified as

appropriate for the intended application. Bull’s eye sight glasses shall be provided with a

traceable serial number or other form of identification that does not compromise the glass

structure or integrity.

16.3 *Electric and Pneumatic Sensor Controls. Sensing devices that initiate control pulses or signals

for refrigeration systems shall comply with this section.

16.3.1 Design. Sensing devices which initiate control pulses or signals shall have a design pressure

that is not less than the design pressure required by Section 5.6. In addition, the sensing

devices shall be in accordance with one or more of the following:

1. Comply with the ultimate strength requirement in Section 16.1.7.

2. Document a successful performance history for devices in comparable service

conditions.

3. Use a performance-based pressure-containment design substantiated by either proof

tests as described in ASME B&PVC, Section VIII, Division 1, Section UG-101 or

international equivalent, or an experimental stress analysis.

16.3.2 Equipment Identification. Manufacturers producing electrical or pneumatic controls shall

provide the following minimum nameplate data:


2. Manufacturer’s serial number, where applicable


4. Electric supply: volts, full load amps, frequency (Hz), phase, where applicable

5. Pneumatic system: control range: maximum supply air pressure, minimum supply air

pressure, required ACFM, where applicable

6. Flow direction, where applicable

7. Any special characteristics of a control device shall be noted either on the name tag or

in the accompanying literature


Chapter 17. Ammonia Detection and Alarms

17.1 Scope. Ammonia leak detection and alarms shall comply with this chapter.

17.2 Power for Detectors and Alarms. The power supply for the ammonia detectors and alarms shall

be a dedicated branch circuit. In the event of a loss of power on other circuits or an emergency

shutdown of refrigeration equipment, the ammonia detection and alarm system shall remain on. In

the event of a loss of power to the ammonia detection and alarm system, a power failure trouble

signal shall be sent to a monitored location.

17.3 Testing

17.3.1 Schedule. A schedule for testing ammonia detectors and alarms shall be established based on

manufacturers’ recommendations, unless modified based on documented experience.

17.3.2 Minimum Test Frequency. Where manufacturers’ recommendations are not provided,

ammonia detectors and alarms shall be tested not less than once per year.

17.4 Detector Placement. A leak detection sensor, or the inlet of a sampling tube that draws air to a

leak detection sensor, shall be mounted in a position where ammonia from a leak is expected to

accumulate. In rooms equipped with continuous exhaust ventilation, the location of leak detection

sensors and sampling tubes shall take into account the air movement towards the inlet of the

ventilation system. Leak detection sensors and sampling tube inlets shall be positioned where they

can be accessed for maintenance and testing.

17.5 *Alarms. The audible alarms providing notification shall provide a sound pressure level of 15

decibels (dBA) above the average ambient sound level and 5 dBA above the maximum sound level

of the area in which it is installed.

17.6 Signage. Ammonia leak detection alarms shall be identified by signage adjacent to visual and

audible alarm devices.

17.7 Detection and Alarm Levels. Where an ammonia detection and alarm level is specified by this

standard, the operational criteria shall be as specified in this section.

EXCEPTION: Where approved, alternatives to fixed ammonia leak detectors shall be

permitted for areas with high humidity or other harsh environmental

conditions that are incompatible with detection devices.

17.7.1 Level 1 Ammonia Detection and Alarm. Level 1 ammonia detection and alarm shall have

the following features:

1. At least one ammonia detector shall be provided in the room or area.

2. The detector shall activate an alarm that reports to a monitored location so that

corrective action can be taken at a level no higher than 25 ppm.



the following features:




3. Audible and visual alarms shall be provided inside the room to warn that, when the

alarm has activated, access to the room is restricted to authorized personnel and

emergency responders.


the following features, and for machinery rooms shall comply with Section 6.13.2:




3. Audible and visual alarms shall be provided inside the room to warn that, when the

alarm has activated, access to the room is restricted to authorized personnel and

emergency responders. For machinery rooms, additional audible and visual alarms shall

be located outside of each entrance to the machinery room.

4. Upon activation of the alarm, control valves feeding liquid and hot gas to equipment in

the affected area shall be closed, and pumps, fans, or other motors associated with the

ammonia refrigeration equipment in the room shall be de-energized.

5. Upon activation of the alarm, emergency exhaust systems, where required, shall be

activated.


Part 4 Appendices

Appendix A. (Informative) Explanatory Material

This informative appendix is not a part of the standard. It provides explanatory information related to

provisions in the standard. Sections of the standard that have associated explanatory information in this

appendix are marked with an asterisk “*” after the section number, and the associated appendix

information is located in a corresponding section number preceded by “A.”

A.1.2 It is the intent of this standard to NOT apply retroactively to existing buildings or

facilities that contain ammonia refrigeration systems. This standard is only intended to

apply to cases where ammonia refrigeration systems or equipment are newly installed,

not including in-kind replacement or repair of existing equipment.

A.2.2 Commercial Occupancy: Commercial occupancies include office, work and storage

areas that do not qualify as industrial occupancies.

Packaged Systems: Examples of packaged systems that constitute large portions of a

refrigeration system include recirculator packages, condenser packages, compressor

packages and chiller packages.

Public Assembly Occupancy: Examples of public assembly occupancies include, but

are not limited to, auditoriums, stadiums, arenas, ballrooms, classrooms, passenger

depots, restaurants and theaters.

A.4.2 See Chapter 2 for Occupancy Classifications.

A.4.2.3 ASHRAE 15 and model mechanical codes include a longstanding allowance to install

evaporators in industrial occupancies outside of a machinery room. However, these

documents do not specifically indicate whether equipment that is ancillary to the heat

exchanger portion of an evaporator, such as surge drums or liquid pumps, are or are not

permitted to be considered as part of an evaporator for the purpose of applying this

allowance. This edition of IIAR 2 included the evaporator exception for consistency with

ASHRAE 15 and model mechanical codes without modification, and thereby,

determination of equipment that might or might not be permitted to be considered as part

of an evaporator remains a decision of the designer and the AHJ. In some cases, the type

of equipment, such as a semi-hermetically sealed or hermitically sealed pump, versus an

open-drive pump, will influence the determination.

A.4.2.4 The value of 320 ppm used in IIAR 2 is based on the Immediately Dangerous to Life and

Health (IDLH) value provided by ASHRAE 34 for ammonia, which is consistent with the

value in the International Fire Code. Other sources, including NIOSH and the Uniform

Mechanical Code specify a value of 300 ppm; however, in the scheme of ammonia

refrigeration release incidents, the difference between these values is not considered to be

consequential. Also note that other sections of IIAR 2 that establish regulations based on

½ of the IDLH value use a 160 ppm concentration, rather than 150 ppm, which might be

used by other codes or standards that are based on a 300 ppm IDLH value.


Provided that a system complies with the 320 ppm limit, it is permissible to have some

equipment located outdoors and some inside since this section would permit the entire

system to be inside, and placing some equipment outside further reduces occupant

exposure risk.

A.5.2.1 See Appendix B (Informative) for additional information regarding the characteristics

and properties of ammonia.

A.5.4 The provisions in this section are generally based on ASHRAE 15, however, they are

different in that ASHRAE 15 includes refrigerants that are typically heavier-than-air.

Ammonia is a lighter-than-air gas, and IIAR 2 provisions address this difference.

A.5.4.1 For the purpose of determining how to treat interconnected spaces, as separate or

singular, ASHRAE 15 recognizes permanent wall openings that might include doors,

passages and conveyor openings. However, because ammonia is lighter than air and

tends to rise, as compared to other refrigerants that tend to sink, the determination of

openings that might create interconnected spaces for a facility containing ammonia must

take into account ammonia’s buoyancy. Accordingly, the elevation of the opening must

be considered. In addition, any physical opening that is determined to create

interconnected spaces must be able to reliably remain unobstructed through the life of the

building.

In addition, where the calculation procedure is being performed for the purpose of

determining whether emergency ventilation is needed to reduce the risk of a flammable

concentration, in accordance with Section 7.3.1.2, it is important to be very conservative

in determining interconnected spaces. The threshold for requiring emergency ventilation

is based on a calculated average concentration in the space of 40,000 ppm, which is 25-

percent of the lower-flammable-limit, and this average concentration could be associated

with higher concentrations in local areas. Given that ignition sources such as fueled

heaters and ordinary light fixtures would be permitted at the ceiling level in these areas, it

is important that the calculation provides a high level of confidence that an ignitable

concentration will not exist in any location where ignition sources might be present.

A.5.4.3 Using the smallest volume space for a release event provides a worst case scenario

analysis.

A.5.4.4 Where a damper might be expected to stop airflow between two rooms or spaces, those

spaces should not be considered as connected for purposes of evaluating a worst case

scenario of an ammonia release into the smallest exposed space. Fire dampers, smoke

dampers and dampers that provide both functions are normally open and will only close

in a fire event, not an ammonia release event, and it is not the intent of this section to

require a design that assumes an ammonia release that is simultaneous with a fire.

Adjustable dampers, such as those that might be found on a variable airflow system need

not be considered as stopping the airflow between two rooms or spaces as long as the

damper is not capable of closing more than 90-percent during normal operation.


A.5.6 It should be noted that ASHRAE 15 includes a requirement that the design pressure of

refrigeration systems need exceed the critical pressure for a refrigerant unless higher

pressure is anticipated during operating, standby or shipping conditions. In the case of

ammonia, the critical pressure is 1636 psi, which far exceeds any system design pressure;

therefore, this provision is not relevant in IIAR 2 and was not included.

A.5.6.1.1 The intent of this requirement is to avoid nuisance shutdowns or nuisance releases caused

by the lack of a buffer between normal operational pressure levels and pressure levels

associated with abnormal or emergency conditions that lead to a shutdown or a release.

For information on the appropriate allowances for design pressure, see the ASME

B&PVC, Section VIII, Division 1, Appendix M.

A.5.6.2.2 Examples of standby conditions that would be considered in applying this section include

maintenance, shutdown and power failure.

A.5.8.1.2 Air and water are examples of expected contaminants. Nevertheless, in trace amounts

that might ordinarily be present in an ammonia refrigeration system, significant

deterioration of materials, such as steel piping or vessels, is not expected.

A.5.9 Section 15.5.1 lists a variety of permissible methods for atmospheric release of non-

condensable gases, including an allowance for other approved means that are not

specifically stated. Such other means might include releasing gas through a water

column.

A.5.11.1 Insulation can also be provided for energy conservation purposes, as required by the

owner or local energy conservation requirement. For additional information on insulation

of piping, see the IIAR Piping Handbook.

A.5.14.1 See Chapter 3 of the Uniform Mechanical Code and Chapter 3 of the International

Mechanical Code, which provide requirements for access to all types of mechanical

equipment, including ammonia refrigeration systems. In addition, Chapter 11 of the

Uniform Mechanical Code includes special access provisions for ammonia refrigeration

equipment.

A.5.14.3 Examples of equipment that might require maintenance or functional control testing

include liquid level indicators, float switches and high-pressure cut out switches.

A.5.14.5 This section requires equipment to be designed and installed with serviceability in mind,

including clearances for service tools and similar serviceability provisions. See OSHA 29

CFR 1910.24 for information on providing fixed stairs for access to serviceable

equipment.

A.5.14.6 Where multiple pieces of serviceable equipment are readily isolated by a single set of

hand isolation valves, the use of a single set of valves meets the intent of this section.

A.5.15.2.2 This requirement is consistent with ASHRAE 15, which regulates the secondary coolant.

See ASHRAE 15, Section 9.11.1.


A.5.16.3 A replacement-in-kind change to equipment will not ordinarily require updating of

emergency shutdown procedures.

Examples of unique identification include valve tags and signs.

A.5.16.4.2 An example of an international standard is EN 13445 Parts 1-5 in accordance with

national regulations satisfying the requirements of the European Pressure Equipment

Directive (PED).

A.5.16.4.3 Appendix D (Informative) provides further information on duplicate nameplates.

A.5.16.6 Wind indicators are not required by IIAR 2. However, they are sometimes provided for

use in conjunction with EPA or OSHA emergency planning and response procedures.

See EPA Alert 550-F-01-1999, August 2001.

A.5.16.5 See IIAR Bulletin No. 114 for guidance on identification of ammonia piping and

equipment.

A.5.19.2 Examples of rotating parts that might require protection include shafts, belts, pulleys,

flywheels and couplings.

A.5.19.4 Used equipment includes equipment that is relocated or purchased after previous use.

A.5.19.5 Further information on structural load requirements can be found in the Building Code

and the Mechanical Code. Also see Section 5.13.

A.5.19.6 For additional information, see OSHA 29 CFR 1926.56.

A.5.19.7 The Building Code provides comprehensive regulations for means of egress, but of

particular concern in ammonia refrigeration facilities is the required minimum clear

height and width for access to equipment in areas that contain piping or machinery. The

designer is cautioned to ensure that the minimum clear height and width provisions in the

building code for aisles are maintained in the design. See 2015 International Building

Code Section 1018.5, Exception and Sections 1003.2 and 1003.3.

A.6.2.1 See Section 6.10.2 and 6.10.3 for requirements related to doors and Section 6.6.2 for pipe

penetrations. Also see the definitions of “tight construction” and “tight fitting door” in

Chapter 2.

A.6.3.3.1 See 29 CFR 1910.27 for information regarding ladder access.

A.6.10.3 The allowance to permit a machinery room without direct egress to the outside is

consistent with provisions in model building codes that permit Group H-2 occupancies to

be located without an exterior wall when the room does not exceed 500 square feet in

area.

A.6.13.2.2 Visual alarms can be provided by strobes or other distinctive visual signaling devices.


A.6.13.2.3 The threshold for initiating emergency ventilation has been changed in the 2014 edition

of IIAR 2. Some previous editions and model mechanical codes specify that emergency

ventilation is to be activated at an ammonia concentration not exceeding 1,000 ppm. The

1,000 ppm value had been based on concerns that serious damage to equipment might

occur if a large volume of frigid outdoor air unnecessarily flooded a machinery room in a

cold climate zone because a leak detector sensed a small leak or a small maintenance-

related release. While this remains a valid concern, the concern is overshadowed by two

more important considerations.

First, IIAR 2 no longer requires normal mechanical ventilation to initiate at TLV/TWA

concentrations (25 ppm), as it did in some previous editions. Activation of emergency

ventilation at ½ of the IDLH concentration (160 ppm), rather than 1,000 ppm, retains a

means to quickly ventilate a significant release. Concentrations that might precede

activation of emergency ventilation, those in the range between TLV/TWA (25 ppm) and

½ IDLH (160 ppm), are not acutely hazardous to occupants, and the strong smell of

ammonia associated with such concentrations will be readily noticed by occupants as a

cue to self-evacuate

Second, it is recognized that emergency response by plant personnel is significantly less

complex for releases not exceeding ½ IDLH (160 ppm) concentrations, versus

concentrations of 1,000 ppm or more. Activating emergency ventilation at the lower

threshold increases the likelihood of emergency responders encountering reduced

ammonia concentrations when they arrive at the scene, thereby limiting responders’

exposure risk and increasing the likelihood of an incident being controlled in the early

stages.

To address the cold climate concern discussed above, consideration can be given to

developing alternative solutions for activating the ventilation system or conditioning

supply air before it is introduced into the machinery room, as would be necessary for

activating at the TLV/TWA (25 ppm).

A.6.14.1 This requirement correlates with the minimum breathing air requirements in model

mechanical codes for machinery rooms but has been expanded to permit the use of

natural ventilation where natural ventilation can be demonstrated as meeting the

minimum air exchange requirements.

A.6.14.6.1 When selecting a location for exhaust discharge to the atmosphere it is preferable to

select a location that will minimize the risk of creating a nuisance or hazard in the event

of an ammonia release. Consideration should be given to the natural airflow around the

building, prevailing winds and surrounding structures.

A.6.14.6.5 Fans in a machinery room are not required to be suitable for installation in Class I,

Division 2 atmospheres because the Electrical Code does not require hazardous location

electrical equipment in areas containing ammonia that are provided with adequate

mechanical ventilation. Nevertheless, in an abundance of caution, this Standard requires

an extra level of protection for fan motors in machinery rooms.


A.6.14.7.1 See ASHRAE Handbook, Fundamentals, Chapter 14, Climate Design Information for

determination of dry bulb temperature.

A.6.14.8.1 Appendix K (Informative) provides an example calculation for determining an emergency

ventilation rate.

A.6.14.10.1 It is sometimes considered convenient to schedule testing of emergency ventilation

systems in conjunction with testing and calibration of ammonia detection equipment.

A reduced frequency for testing might be established after enough test data has been

accumulated to support the reliability of the ventilation equipment with less frequent

testing.

A.6.15.1 International Mechanical Code (IMC) Table 1103.1 establishes the degree of severity

designations to be provided on the NFPA 704 placard, which differs for indoor and

outdoor locations based on the risk of ignition. The IMC designates health, fire and

reactivity to be 3-3-0 for indoor locations and 3-1-0 for outdoor locations. See also

Appendix J for further information regarding machinery room signs.

A.7.2.4 Model mechanical codes and ASHRAE 15 require refrigerant leak detection to be

provided where certain refrigeration equipment is located outside of a machinery room.

Nevertheless, because ammonia is self-alarming, with a pungent odor that warns of

ammonia’s presence well before the concentration becomes acutely hazardous, leaks are

readily detected when someone is in the area. For areas that operate on a 24/7 work

schedule that have an emergency plan in place for dealing with an ammonia release, fixed

detection systems are sometimes omitted in favor of relying on occupants to detect and

respond to a leak in accordance with the emergency plan. In jurisdictions where a model

mechanical code has been adopted, use of an alternative to fixed detection will require

approval of the AHJ, as provided in Section 1.3.2 because the mechanical codes

specifically require leak detection for these applications. In jurisdictions where a

mechanical code has not been adopted, the determination of the approach to detection

will be determined by the designer as provided in Section 1.3.3 based on an assessment

of the area to be protected.

A.7.3.1.1 By referencing Section 4.2.3 Item 4, it is specifically intended that this section, and the

associated provisions for ventilation, not apply for equipment that is permitted outside of

a machinery room by Section 4.2.3 Items 1-3.

A.7.3.1.2 If an area includes multiple refrigeration systems, each system is permitted to be

considered individually when calculating release concentration. In some cases, an

enclosure might be provided for equipment containing ammonia, and local ventilation

within the enclosure might be used to meet the emergency ventilation provisions in lieu

of ventilating the entire room or area. See Appendix K. Alternatives to ventilation might

include systems that employ a water mist system or a CO₂ fogging system, where

approved by the AHJ.


A.8.3.1 Appendix E (Informative) describes an acceptable method of calculating the discharge

capacity of positive-displacement compressor pressure-relief devices.

A.8.3.2 The referenced safety controls are commonly referred to as a low pressure cutout and a

high pressure cutout. An indicating-type lubrication failure control is commonly referred

to as a low oil pressure cutout.

A.8.6.6 Compressor designs differ. Sometimes installing a discharge check valve is sufficient to

avoid liquid accumulation and backflow. For example, some designs that use high

pressure ammonia for oil cooling will also require a suction check valve. Other means,

such as automatic shut-off valves, are not often used but can be effective in lieu of check

valves.

A.8.6.9 The requirements in this section are intended to protect compressors from liquid

slugging.

A.10.1 The location of a condenser relative to the receiver should be arranged to provide

sufficient refrigerant head for the ammonia to properly drain.

A.12.2.6 See Appendix H (Informative).

A.13.1 Piping is defined as including both pipe and tubing.

A.13.2.1 The requirement to comply with ASME B31.5 applies to both shop fabricated and field

erected piping. In addition to materials that are specifically mentioned therein, ASME

B31.5 Section 523.1.2 also allows the use of other materials, which can be accepted as

compliant with IIAR 2 where approved by the AJH based on the submittal of

documentation that demonstrates the suitability of the pipe for the intended application.

A.13.2.2 See Appendix L (informative) for criteria historically applied to ammonia piping in

closed-circuit ammonia refrigeration systems.

A.13.2.3 Tubing is used for compressor lubrication lines; small bore pressure sensing lines;

hydrostatic relief lines; etc.

A.13.3 Refer to IIAR 3 for the manufacturing, design and performance requirements of ammonia

refrigeration valves and strainers.

A.13.3.2.2 The exception provides for cases where a designer chooses to install a directional valve in

a backwards orientation, which is a method that is sometimes used to provide a high level

of resistance to backflow.

A.13.3.3 This valve arrangement has the potential to trap liquid.

A.13.3.5 Shut-off valves are also referred to as stop valves. Control valves and other valves

without a manually operable and lockable actuating element intended to stop flow for

isolation purposes, such as solenoid valves and check valves, are not classified as shut-off

or stop valves.


A.13.4 ASME B31.5 provides guidance for certain pipe support and hanger components,

protective coatings, etc. See also Appendix F (Informative) for additional information.

A.13.5 See Section A.5.19.7 for additional information related to clearances required by the

Building Code.

A.13.4.1 Examples of loads include ammonia weight, insulation, frost, ice, seismic, wind, and

thermal.

A.14.1.3 It is the intent of this section to include all packaged systems, regardless of whether the

enclosure is applied at point of fabrication, during installation or after installation.

A.14.2.7 The intent of requiring emergency valves to be directly operable is to have the valve

available for rapid operation in the event of an emergency. Accordingly, a valve

operating wheel needs to be permanently installed on manual emergency valves that are

not chain operated, and access to operate valves cannot require use of a ladder, stool or

similar assistive device.

A.15.1 See Appendix I (Informative) for additional information related to overpressure

protection.

A.15.2 Overpressure protection should be install as close as possible to or directly on the

pressure vessel or other equipment being protected to minimize pressure drop that may

occur in the piping feeding the inlet side of the valve.

A.15.2.4 The connection for pressure relief protection should be positioned at the highest practical

point on a pressure vessel or other equipment being protected.

A.15.2.7.3 See ASME B&PVC, Section VIII, Division 1, Section UG-127.

A.15.3.7.1 Note that SCFM x 0.0764 = lb/min of dry air.

A.15.3.7.2.2 Appendix C (Informative) provides a method to determine the capacity for safety relief

valves to relieve overpressure due to blocked outlets on oil cooling heat exchangers.

Appendix G (Informative) provides a method for determining the size of hydrostatic

overpressure-relief valves.

Appendix C (Informative) provides a method for determining the capacity for safety

relief valves to relieve pressure due to internal heat loads in heat exchangers

A.15.3.8 It should be noted that IIAR 2 requires application of the increased relief capacity factor

for materials that are “stored” within 20 feet of a pressure vessel; whereas, ASHRAE 15

requires application of the increased relief capacity factor for materials that are “used”

within 20 feet of a pressure vessel. The technical concern relates to increased exposure

of the pressure vessel to an external fire, and IIAR 2 takes the position that “storage” of

combustible materials adjacent to a pressure vessel constitutes the more accurate

description of a scenario warranting application of the additional safety factor.


A.15.5.1 For cases where a water diffusion tank is being contemplated, consideration should be

given to using an atmospheric relief discharge, but increasing the termination point to not

less than 30 feet (9.1 m) above the adjacent grade, or roof level. Research indicates that a

high velocity vertical discharge at such elevations is very effective at diffusing ammonia

into air and minimizing the risk of ammonia exposure at ground level.

A.15.6.1 An example of a possible cause of hydrostatic overpressure related to seasonal conditions

is the closing valves in ammonia lines to and from evaporative condensers during cold

weather conditions.

A.16.1.4 One possible means of monitoring ammonia concentration resulting from a leak during a

power failure is a portable ammonia monitoring device.

A.16.1.5 Examples of systems that might be inadvertently impacted by unauthorized personnel

include emergency exhaust and equipment shutdown controls. For these systems and

others, an unauthorized individual might mistakenly change the set points for normal

system operation related to temperature, pressure, flow or vessel levels, but

unintentionally affect alarm or emergency control settings.

A.16.2.1.1 The basis of a performance-based design could be an analysis that is consistent with the

general design philosophy embodied in ASME B31.5.

A.16.2.3 Linear liquid level indicators are sometimes referred to as sight columns. It is

recommended that linear liquid level indicators be of the flat “armored glass” type in

preference to the tubular glass type.

A.16.3 Relay switches, contactors, and starters are not addressed by this section.


A.15.5.1.1.1 Typical Moody friction factors (ƒ) for fully turbulent flow are provided in Tables

A.15.5.1.1.1(1) and A.15.5.1.1.1(2).

Table A.15.5.1.1.1(1)

Typical Moody Friction Factors, Steel Tubing

Tubing

OD (in.) DN ID (in.) ƒ

3⁄8 8 0.315 0.0136

1⁄2 10 0.430 0.0128

5⁄8 13 0.545 0.0122

3⁄4 16 0.666 0.0117

7⁄8 20 0.785 0.0114

11⁄8 25 1.025 0.0108

13⁄8 32 1.265 0.0104

15⁄8 40 1.505 0.0101

Table A.15.5.1.1.1(2)

Typical Moody Friction Factors, Steel Piping

Piping

NPS DN ID (in.) ƒ

1⁄2 15 0.622 0.0259

3⁄4 20 0.824 0.0240

1 25 1.049 0.0225

11⁄4 32 1.380 0.0209

11⁄2 40 1.610 0.0202

2 50 2.067 0.0190

21⁄2 65 2.469 0.0182

3 80 3.068 0.0173

4 100 4.026 0.0163

5 125 5.047 0.0155

6 150 6.065 0.0149

A.17.5 The minimum audibility required for fire alarm signaling devices is normally a sound

pressure level of 15 decibels (dBA) above the average ambient sound level and 5 dBA

above the maximum sound level in the area where the device is installed. This was

determined to be a suitable level for ammonia detection alarms to ensure adequate

audibility. The intent of including a specific sound pressure level in dBA is to provide a

measurable basis for alarm design and to determine adequacy of the audibility where

someone might question if an alarm is reasonably loud when the alarm is commissioned.

A difference of opinion in this regard could be resolved by using a sound meter.


Appendix B. (Informative) Ammonia Characteristics and Properties

This appendix is not part of this standard. It is merely informative and does not contain requirements

necessary for conformance to the standard. It has not been processed according to the ANSI requirements

for a standard and may contain material that has not been subject to public review or a consensus process.

B.1 Ammonia Characteristics

The term ammonia, as used in this standard, refers to the compound formed by combination of nitrogen and

hydrogen, having the chemical formula NH3. It is not to be confused with aqua ammonia, which is a

solution of ammonia gas in water. Whenever the term ammonia appears in this standard, it means

refrigerant-grade anhydrous ammonia.

Experience has shown that ammonia is difficult to ignite and, under normal conditions, is a very stable

compound. It requires temperatures of 840-930°F [450-500°C] [723.2-773.2K] to cause it to dissociate

slightly at atmospheric pressure. The flammable limits at atmospheric pressure are 15.5% to 27% by

volume of ammonia in air. An ammonia-air mixture in an iron flask does not ignite below 1204°F

[651.1°C] [925.3K].

Since ammonia is self-alarming, it serves as its own warning agent so that a person is not likely to

voluntarily remain in concentrations which are hazardous.

B.2 Physical Properties of Ammonia

English Common

Metric

SI

Molecular symbol NH3 NH3 NH3

Molecular weight 17.031 lb/lb-

mol

17.031 g/mol 17.031 g/mol

Boiling point at one atmosphere* -27.99°F -33.33°C 239.82K

Freezing point at one atmosphere* -107.78°F -77.66°C 195.5K

Critical temperature 269.99°F 132.22°C 405.37K

Critical pressure 1644 psig 115.6 kg/cm2

(gauge)

11.34 MPa

(gauge)

Latent heat at -28°F (-33°C)(240.15K) and one atmosphere 588.8 Btu/lb 327.1 cal/g 1.369 MJ/kg

Relative density of vapor compared to dry air at 32°F

(0°C)(273.15K) and one atmosphere

0.5967 0.5967 0.5967


Vapor density at -28°F (-33°C)(240.15K) and one atmosphere 0.05554 lb/ft3 0.8896 kg/m3 0.8896 kg/m3

Specific gravity of liquid at -28°F (-33°C)(240.15K)

compared to water at 39.4°F (4.0°C) (277.1K)

0.6816 0.6816 0.6816

Liquid density at -28°F (-33°C)(240.15K) and one

atmosphere*

42.55 lb/ft3 681.6 kg/m3 681.6 kg/m3

Specific volume of vapor at 32°F (0°C)(273.15K) and one

atmosphere*

20.80 ft3/lb 1.299 m3/kg 1.299 m3/kg

Flammable limits by volume in air at atmospheric pressure 15.5% to 27% 15.5% to 27% 15.5% to 27%

Ignition temperature 1204°F 651.1°C 924.13K

Specific heat, gas at 59°F (15°C)(288.15K) and one atmosphere*

At constant pressure (cp )

At constant volume (cv )

0.5184

Btu/lb°F

0.3928

Btu/lb°F

0.5184 cal/g°C

0.3928 cal/g°C

2.1706 kJ/kg K

1.6444 kJ/kg K

Ratio of specific heats k(cp/cv, also ) at 50°F (15°C)(288.15K)

and one atmosphere*

1.320 1.320 1.320

NOTE: *One standard atmosphere = 14.696 psia [1.0333 kg/cm2 absolute] [101.33 kPa absolute]


Appendix C. (Informative) Methods for Calculating Relief Valve Capacity for Heat Exchanger

Internal Loads

INTRODUCTION

This informative appendix presents approaches for determining the capacity of relief valves for overpressure

scenarios not explicitly covered in Chapter 15. This information can be used to document a basis for relief device capacity

determination for heat exchangers that may be subject to overpressure due to internal heat loads or blocked valves that can

lead to high refrigerant pressures. Pressure relief devices need to have sufficient mass flow carrying capability (capacity)

to limit the pressure rise in protected equipment to prevent its catastrophic failure. The minimum required relief device

capacity will depend on the specific equipment being protected and the scenarios under which overpressure is being

created. The maximum relief device capacity is not limited by codes and standards. However, over-sizing relief valves

shall be avoided to prevent unstable relief device operation.

Although the methods presented in this informative appendix are intended to apply across a wide range of

refrigeration equipment and operating conditions, it is not possible to neatly prescribe relief device sizing and selection

criteria to cover all situations. The approach presented here is intended to be illustrative of the process that can be

followed in establishing pressure relief requirements for specific situations. As such, the use of sound engineering

principles and the application of engineering judgment are expected.

It is important to emphasize that for all of the cases considered, the rate of refrigerant vapor production needs to be

converted to an air mass flow since all of the relief devices are rated on an air basis. In the sections that follow are

methods for relief capacity determination for different types of heat exchangers based on internal heat addition.

NOMENCLATURE

cp,fluid - secondary fluid heat capacity (Btu/lbm-°F)

cpfluid,CIP- clean-in-place fluid heat capacity (Btu/lbm-ºF)

Cr - minimum required discharge capacity of the relief device for a vessel (lbm/min of air)

Cr,plate HX - minimum required relief device capacity for plate heat exchanger (lbm/min of air)

Cr,OS - minimum required discharge capacity of the relief device protecting an oil separator (lbm/min of air)

Cr,tank - minimum required discharge capacity of the relief device protecting a product tank heat exchanger (lbm/min of

air)

D - outside diameter of vessel or product tank (ft)

Ds - outside diameter of surge drum (ft)

Dv - outside diameter of the main vessel portion of the shell-and-tube heat exchanger (ft)

f - relief device capacity factor that depends on refrigerant type and whether combustible materials are in close proximity

to the pressure vessel (see ASHRAE 15 2007 for capacity factor values)

H - height of the plate pack or tank heat exchanger (ft)

hvapor,sat - saturated vapor refrigerant enthalpy at the fully accumulated relief device set pressure (Btu/lbm)

hliquid,sat - saturated liquid refrigerant enthalpy at fully accumulated relief device set pressure (Btu/lbm)

L - length of the vessel or plate pack (ft)


LMTD - Log mean temperature difference (°F)

Ls - length of surge drum (ft)

Lv - length of the main vessel portion of the shell-and-tube heat exchanger (ft)

brinem - secondary fluid mass flow rate (lbm/min)

,fluid CIPm - clean-in-place fluid mass flow rate (lbm/min)

refrigerantm - refrigerant vapor generation rate (lbm/min)

,refrigerant OCm - mass flow rate of refrigerant vapor generated by the oil cooler (lbm/min)

,refrigerant tankm - mass flow rate of refrigerant vapor generated in a tank heat exchanger (lbm/min)

Pr - Prandtl number for fluid used to establish the nominal UA (-)

Pr' - Prandtl number for fluid used to establish the modified UA' (-)

Q - heat exchanger heat flux (Btu/min)

QOC - oil cooling heat exchanger heat load (Btu/min)

Tfluid,CIP,supply - maximum fluid supply temperature during CIP (ºF)

Trefrigerant - refrigerant saturation temperature (°F)

Tref,sat - refrigerant’s saturation temperature at the relief valve set pressure (ºF)

Treturn - load-side heat exchanger secondary fluid return temperature (°F)

Tsupply - load-side heat exchanger secondary fluid supply temperature (°F)

UA - overall heat transfer coefficient-area product (Btu/min-°F)

UA' - modified overall heat transfer coefficient-area product (Btu/min-°F)

W - width of the plate pack (ft)

- refrigerant-to-product tank effectiveness (estimated as 0.2 for bulk tanks)

APPLICATION

If a heat exchanger is built to the requirements of the ASME B&PVC, Section VIII, Division 1 and is physically

stamped as such, it requires pressure relief protection per ASME B&PVC Section VIII, Division 1, Section UG-125. In

cases where conventional pressure relief protection is not required, it is often desirable to size a suitable “process” relief

that will prevent over-pressurizing the heat exchanger during abnormal operation. The first step in determining the

minimum required mass flow for relief protection is defining the scenarios likely to cause the overpressure situation. Heat

exchangers are susceptible to over-pressure by internal heat loads from either product or other secondary fluid flow

streams (e.g. clean-in-place systems). In either situation, the key consideration for relief device sizing is determining the

rate of refrigerant vapor production by evaporation which will be dependent on the heat load and the refrigerant properties

(saturation pressure-temperature relationship and heat of vaporization).


Shell-and-Tube, Plate and Frame, and Scraped (Swept) Surface Heat Exchangers

Most scenarios involve alternate means of thermal energy input to the heat exchanger when the refrigerant side of

the chiller has been isolated from the refrigeration system but the secondary fluid side remains active. Examples of

thermal loads that could generate excessive pressure in a shell-and-tube or plate-and-frame heat exchanger may include

but are not limited to product loads and clean-in-place (CIP) loads.

Of primary concern are those thermal energy sources whose temperatures that exceed the saturation temperature

corresponding to the heat exchanger’s maximum allowable working pressure (MAWP) or pressure relief device set

pressure. If the maximum fluid-side supply temperature is less than the saturation temperature corresponding to the heat

exchanger’s MAWP, the pressure relief capacity can be determined by IIAR 2, Section 15.3. If the maximum fluid-side

temperature is greater than the saturation temperature corresponding to the heat exchanger’s MAWP, vapor generation

rates based on the “internal loads” shall be estimated to determine if a larger relief device capacity requirement results.

The first step in the process of considering an internal heat load scenario that could generate an overpressure

situation is to evaluate the normal capacity of the heat exchanger. The next step is to estimate the heat exchanger’s

capacity under the adverse load condition and determine the corresponding rate of refrigerant vapor generation. Lastly, the

predicted rate of refrigerant vapor generation is converted to an equivalent air mass flow rate to allow relief device

selection.

Determining the rate of refrigerant vapor production can be accomplished by solving a system of equations that

characterize the equipment heat transfer performance, as given by Equation (1), and the balance of both refrigerant-side

and fluid-side energy flows as given by Equations (2) and (3), respectively. The system of governing equations is as

follows:

Q UA LMTD (1)

ln

return supply

return refrigerant

supply refrigerant

T TLMTD

T T

T T

(2)

,fluid p fluid return supplyQ m c T T (3)

, ,refrigerant vapor sat liquid satQ m h h (4)

Where:

Q = heat exchanger heat flux (Btu/min)

UA = overall heat transfer coefficient-area product (Btu/min-°F)

LMTD = Log mean temperature difference (°F)

Treturn = load-side heat exchanger secondary fluid return temperature (°F)

Tsupply = load-side heat exchanger secondary fluid supply temperature (°F)


Trefrigerant = refrigerant saturation temperature (°F)

brinem = secondary fluid mass flow rate (lbm/min)

cp,fluid = secondary fluid heat capacity (Btu/lbm-°F)

refrigerantm = refrigerant vapor generation rate (lbm/min)

hvapor,sat = saturated vapor refrigerant enthalpy at the fully accumulated relief device set pressure (Btu/lbm)

hliquid,sat = saturated liquid refrigerant enthalpy at fully accumulated relief device set pressure (Btu/lbm)

In a liquid-containing heat exchanger, the refrigerant temperature (Trefrigerant) is assumed to be the saturation

temperature corresponding to the pressure relief device set (opening) pressure. The enthalpy of vaporization (hvapor,sat –

hliquid,sat) for the refrigerant-side energy balance is evaluated at the pressure relief device set pressure as well. The return

fluid temperature to the heat exchanger (Treturn) is estimated based on the load which is a function of the fluid flow rate

and return fluid from process, CIP set temperature, etc. The mass flow rate of fluid on the load-side of the heat exchanger

( fluidm ) is required as well as the load-side fluid heat capacity (cp, fluid).

The nominal value of the heat exchanger’s overall heat transfer-area product (UA) is based on design operating

conditions. Equation (1) is used to estimate a nominal or design UA. Once a nominal or design UA is established, it can be

adjusted or corrected for use in estimating the refrigerant vapor production rate arising in an overpressure situation. For

example, if the fluid-side flow rate would be expected to vary from the design condition, the following relationship based

on the Dittus-Boelter turbulent heat transfer correlation could be used to predict a modified UA based on an alternative

fluid-side flow rate.

0.80.4

Pr

Pr

fluid

fluid

mUA UA

m

(5)

Where:

UA = nominal overall heat transfer coefficient-area product (Btu/min-°F)

UA = modified overall heat transfer coefficient-area product (Btu/min-°F)

Pr = Prandtl number for fluid used to establish the nominal UA (-)

Pr = Prandtl number for fluid used to establish the modified UA (-)

In addition, Equation (5) accommodates changes in working fluids when transitioning from a design load condition

to a different working fluid that may arise and create an overpressure situation (e.g. changing from a fluid beverage during

load conditions to a CIP solution during clean-up) that forms the basis for sizing pressure relief protection for the heat

exchanger.

The above-mentioned known information (Trefrigerant, hvapor,sat, hliquid,sat, Treturn, fluidm , cp,fluid, and UA) can be used to

simultaneously solve Equations (1), (3), and (4) to find the remaining three unknown variables: refrigerantm , Tsupply, and Q.


The quantity of interest is the refrigerant vapor flow rate, refrigerantm , which represents the mass flow of vapor generated

during the overpressure scenario. Once obtained, the resulting refrigerant mass flow rate must then be converted to an

equivalent mass flow rate for air using the following relationship (ASHRAE 15 2007 Appendix F):

refrigerant airair

r refrigerant

refrigerant air refrigerant

T MCC m

C T M

(6)

Appendix C of ASHRAE 15 (2013) assumes a refrigerant temperature of 510°R [283 K] and an air temperature of

520°R [289 K]. Appendix C lists values of the constants, Cair and Crefrigerant, for a number of different refrigerants. The

calculated air mass flow based on the estimated refrigerant vapor mass flow represents the minimum required relief

capacity for the internal load scenario.

Example: Scraped (Swept) Surface Heat Exchanger

Heat Exchanger Characteristics for one manufacturer’s scraped (swept) surface heat exchanger:

U ≅ 300 𝐵𝑡𝑢/ℎ𝑟 ∙ 𝑓𝑡2 ∙ ℉

6 𝑓𝑡2 ≤ 𝐴 ≤ 14.5 𝑓𝑡2

150 𝑝𝑠𝑖𝑔 ≤ 𝑀𝐴𝑊𝑃 ≤ 250 𝑝𝑠𝑖𝑔

Heat Load Assumption

Internal Load is created by 160°F CIP fluid

Q UA LMTD ≅ U ∙ 𝐴 ∙ (𝑇𝐶𝐼𝑃 - 𝑇𝑠𝑎𝑡,𝑟𝑒𝑓)

, ,refrigerant vapor sat liquid satQ m h h

Heat Exchanger Characteristics

U = 300 Btu/hr-ft2-°F

A = 14.5 ft2

MAWP = 150 psig [h = 488 Btu/lbm, Tsat,ref = 89.6°F]

TCIP = 160°F

hr

minhh

TTAUm

liquidvapor

refsatCIP

ref

60

,


Heat Exchanger characteristics

U = 300 Btu/hr-ft2-°F

A = 14.5 ft2

MAWP = 250 psig [h = 453 Btu/lbm, Tsat,ref = 120.8°F]

TCIP = 160°F

Oil Cooling Heat Exchangers

Over-pressurization can occur when a thermosiphon oil-cooled screw compressor package is started while the

refrigerant-side of the oil cooler is isolated (valved-out). In this case, the compressor will operate and reject heat to the oil

cooler resulting in an increasing supply oil temperature back to the compressor over time. As the compressor continues to

operate and reject a portion of its heat of compression through its oil to the oil cooling heat exchanger, a point will be

reached when the on-board compressor safeties shutdown the unit on high oil temperature. A typical screw compressor

package high oil temperature cut-out is approximately 205°F [96°C]. The saturation pressure corresponding to a

refrigerant temperature equal to the oil at its high temperature cut-out of 205°F [96°C] is 825 psig for ammonia. Since this

pressure is significantly greater than the oil cooling heat exchanger’s maximum allowable working pressure, the oil cooler

will be subject to overpressure under this scenario.

)(5.10

60488

6.891605.14300 2

2

ammoniamin

lbm

hr

min

lbm

Btu

FftFfthr

Btu

mref

air

airmin

lbmm

8.135.10314.1

)(3.6

60453

8.1201605.14300 2

2

ammoniamin

lbm

hr

min

lbm

Btu

FftFfthr

Btu

mref

air

airmin

lbmm

3.83.6324.1


The mass flow rate of refrigerant vapor generated on the refrigerant-side of an oil cooler in an overpressure situation

is given by:

,

, ,

ocrefrigerant OC

vapor sat liquid sat

Qm

h h

(7)

Where:

QOC = oil cooling heat load generated by the compressor operating at design suction pressure and discharge

pressures with a corresponding supply oil temperature at the compressor high temperature cut-out limit (Btu/min)

,refrigerant OCm = mass flow rate of refrigerant vapor generated by the oil cooler (lbm/min)

hvapor,sat = saturated vapor refrigerant enthalpy at the fully accumulated relief device opening pressure (Btu/lbm)

hliquid,sat = saturated liquid refrigerant enthalpy at the fully accumulated relief device opening pressure (Btu/lbm)

The best source for determining the overpressure condition oil cooling loads, QOC, is by information provided from

the compressor manufacturers. Some compressor manufacturers’ computerized selection programs provide this

information based on users inputting the design suction and discharge pressures along with oil supply temperatures. The

programs return the resulting oil cooling load under the modified (high oil supply temperature) conditions. The oil cooling

load imposed on the oil coolers can be evaluated at these modified conditions or alternatively, the full oil cooling load can

be taken for sizing the relief device.

The resulting oil cooling load at the elevated operating condition (Qoc) can then be used to estimate the refrigerant

mass flow rate using Equation (7). The refrigerant mass flow rate is then converted to an air basis using Equation (9);

thereby permitting the selection of a relief device.

Product Storage Tanks

The scenario for refrigerant vapor generation in the heat exchanger due to internal loads arises during clean-in-place.

The rate of refrigerant vapor generation during clean-in-place can be estimated as follows:

, , , , ,

,

, ,

fluid CIP fluid CIP fluid CIP supply ref sat

refrigerant tank

vapor sat liquid sat

m cp T Tm

h h

(8)

Where:

,refrigerant tankm = mass flow rate of refrigerant vapor generated in the heat exchanger (lbm/min)

= refrigerant to product tank effectiveness (estimated as 0.2)

,fluid CIPm = CIP fluid mass flow rate (lbm/min)

cpfluid,CIP = CIP fluid heat capacity (approximated as 1 Btu/lbm-ºF)

Tfluid,CIP,supply = maximum fluid supply temperature during CIP (ºF)


Tref,sat = refrigerant’s saturation temperature at the relief valve set pressure (ºF)

hvapor,sat = saturated vapor refrigerant enthalpy at fully accumulated relief device set pressure (Btu/lbm)

hliquid,sat = saturated liquid refrigerant enthalpy at fully accumulated relief device set pressure (Btu/lbm)

After determining the refrigerant mass flow rate, the relief device capacity (on an air-equivalent basis) is found by

using Equation (6). The greater of these two capacities forms the basis for relief device selection for a product tank.

References ASHRAE Transactions, “Pressure Relief Device Capacity Determination” Reindl, Douglas T. and Jekel, Todd B., Industrial

Refrigeration Consortium. University of Wisconsin-Madison, Madison, WI and American Society of Heating, Refrigerating,

and Air conditioning Engineers, Atlanta, GA, (2009).

ASHRAE Standard 15, “Safety Standard for Refrigerating Systems”, American Society of Heating, Refrigerating, and Air

conditioning Engineers, Atlanta, GA, (2013).


Appendix D. (Informative) Duplicate Nameplates on Pressure Vessels




Duplicate Nameplates on Pressure Vessels

The ASME B&PVC, Section VIII, Division 1 permits duplicate (or secondary) nameplates on pressure

vessels. Duplicate nameplates may be desirable in certain circumstances, especially where the original

nameplate may be obscured by insulation.

Experience has shown that attempting to access the original nameplate for inspection through windows,

removable insulation sections, stanchion mounting, etc. tends to compromise the integrity of the insulation

system. Moisture ingress into the insulation system follows, with possible damage to the pressure vessel.

The use of duplicate nameplates helps prevent vessel damage from inspection ports and other deliberate

damage to insulation.

Unfortunately, using duplicate nameplates creates the possibility that the wrong (duplicate) nameplate will

be applied to a vessel. The ASME B&PVC, Section VIII, Division 1 specifies that the vessel manufacturer

must ensure that the duplicate nameplate is properly applied. While the easiest way to accomplish this is for

the manufacturer to weld the nameplate to a support or other permanent vessel appurtenance that will not be

insulated, field installation is also permitted. (Some inspection authorities consider the insulation jacket as a

permanent attachment to the vessel, and therefore the duplicate nameplate may be applied to the jacket.)

The manufacturer’s procedures for ensuring a proper match of duplicate to original must be rigorously

followed. It is advisable to record the location of the original nameplate should inspection be necessary.

Various inspection authorities such as State vessel inspectors may demand to inspect and/or approve the

duplicate and original nameplates before insulation is applied. While many inspection bodies will accept a

duplicate nameplate as evidence of ASME B&PVC, Section VIII, Division 1 compliance for an insulated

vessel, authorized inspectors may always demand to inspect the original vessel, including its nameplate. In

particular, when the inspector is concerned about the physical condition of the vessel or questions the

provenance of the duplicate nameplate, he or she may require the entire insulation system or any part to be

removed to permit inspection. Damage to the insulation system must be promptly and professionally

repaired, and due allowance should be made for the shorter service life of the repaired insulation system.


Appendix E. (Informative) Method for Calculating Discharge Capacity of a Positive

Displacement Compressor Pressure Relief Device


necessary for conformance to the standard. It has have not been processed according to the ANSI

requirements for a standard and may contain material that has not been subject to public review or a

consensus process.

Reprinted by permission of The American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE).

The following calculation method provides the required discharge capacity of the compressor pressure relief

device in Section 8.3.1.

g

v

r v

PLQW

Where

Wr = mass flow of refrigerant, lbm/min [kg/s]

Q = swept volume flow rate of compressor, ft3/min [m3/s]

PL = fraction of compressor capacity at minimum regulated flow

v = volumetric efficiency (assume 0.9 actual volumetric efficiency at relieving pressure is known)

vg = specific volume of refrigerant vapor (rated at 50°F [10°C] saturated suction temperature), ft3/lbm [m3/kg]

Next, find the relieving capacity in mass flow of air, Wa, for an ASME B&PVC-rated pressure relief device:

wra rWW (E.2)

r

a

a

r

r

aw

M

M

T

T

c

cr

(E.3)

Where

rw = refrigerant-to-standard-air-mass-flow conversion factor

Mr = molar mass of refrigerant (17.0 for ammonia)

Ma = molar mass of air = 28.97

Ta = absolute temperature of the air = 520 R (289 K)

ca = constant for air = 356

cr = constant for refrigerant (as determined from Equation E.4)

Tr = absolute temperature of refrigerant = 510 R (283 K)

1k

1k

r1k

2k520c

(E.4)


Where

k = ratio of specific heats cp/cv

cp = constant-pressure specific heat of refrigerant at a refrigerant quality of 1 at 50°F (10°C).

cv = constant-volume specific heat of refrigerant at a refrigerant quality of 1 at 50°F (10°C).

Constants for ammonia are listed below:

k = 1.422

Mr = 17.0

cr = 358.0

rw = 1.28

EXAMPLE:

Determine the flow capacity of a relief device for an ammonia screw compressor with a swept volume, Q, of 1665

ft3/min (0.7858 m3/s). The compressor is equipped with capacity control that is actuated at 90% of the pressure

relief device set pressure to its minimum regulated flow of 10%.

Q=1665 ft3/min (0.7858 m3/s)

v=0.90 (assumed)

PL=0.1

vg =3.2997 ft3/lbm (0.206 m3/kg)

min4.45

2997.3

9.01.0min

1665

3

3

m

m

r

lb

lb

ft

ft

W

s

kg

kg

m

s

m

Wr 343.0

206.0

9.01.07858.0

3

3

airlb

rWW mwra

min1.5828.14.45

air

s

kgrWW wra 439.028.1343.0

Converting to standard cubic feet/minute (SCFM), where Va= specific volume of air = 13.1 ft3/lbm

(0.818 m3/kg) for dry air at 60°F (15.6°C),

SCFM = 13.1(58.1) = 761 ft3/min

[SCFM = 0.818(0.439) = 0.359 m3/s].


Appendix F. (Informative) Pipe Hanger Spacing, Hanger Rod Sizing, and Loading




F.1 Recommended maximum spacing of hangers and minimum hanger rod size for steel pipe are set forth in

Table F.1. Spacing does not apply where span calculations are made or where concentrated loads such as flanges,

valves, specialties, etc. are placed between supports. These tables do not account for seismic, thermal, or other

dynamic load considerations.

Table F.1

Nominal

Pipe Size

(in)

Maximum

Span (ft)

Minimum

Rod Diameter

(in)

Up to 1 7 3⁄8

11⁄4 –1

1⁄2 9 3

⁄8

2 10 3⁄8

21⁄2 10 1

⁄2

3 12 1⁄2

4 14 5⁄8

5 16 5⁄8

6 17 3⁄4

8 19 7⁄8

10 22 7⁄8

12 23 7⁄8


14 25 1

16 27 1

18 28 11⁄4

20 30 11⁄4

F.2 The maximum recommended hanger rod loading based on threaded hot rolled steel conforming is shown

in Table F.2.

Table F.2

Rod

Diameter

(in)

Maximum

Load

(lb)

Rod

Diameter

(in)

Maximum

Load

(lb)

3⁄8 610 1

1⁄2 11 630

1⁄2 1 130 1

3⁄4 15 700

5⁄8 1 810 2 20 700

3⁄4 2 710 2

1⁄4 27 200

7⁄8 3 770 2

1⁄2 33 500

1 4 960 23⁄4 41 600

11⁄8 6 230 3 50 600

11⁄4 8 000 3

1⁄4 60 500


Appendix G. (Informative) Hydrostatic Overpressure Relief




NOTE:

This Appendix is presented entirely in the English engineering unit system.

G.1 Background

Hydrostatic overpressures can occur when liquids become confined within enclosed volumes with no gases

present. For this to occur, the temperatures of such liquids must be below their boiling points.

Liquids such as oil, secondary coolants, and sub-cooled primary refrigerants can become entrapped when

certain equipment of a closed-circuit ammonia refrigeration system is isolated from other portions of the

system by valves or other means. If there is an increase in temperature in such confined liquids, rapidly

rising pressures can occur that are functions of the bulk moduli of elasticity of the liquids. While such

increases in temperature and pressure can be very rapid, the corresponding rates of volume increase of the

liquids are relatively low. Therefore, relief devices installed to relieve the resulting pressure need not have

the flow capacity of vapor relief devices.

Practitioners have found that very small relief devices satisfy most requirements for hydrostatic

overpressure relief found in refrigeration service. The technical literature available that quantifies such

requirements, based on empirical test data, is found almost exclusively in areas of practice that are much

more severe than refrigeration service. However, many authorities having jurisdiction require calculations

or other evidence to justify selection and sizing of hydrostatic overpressure-relief devices. In those cases, it

is acceptable good engineering practice to demonstrate that a relief device having adequate capacity for an

extremely severe application will certainly be adequate for less severe circumstances typically encountered

in refrigeration applications. The objective is to provide adequate relief, not necessarily to determine

exactly how much liquid expansion will occur. In most, if not all cases, the smallest relief valves

manufactured for such purposes will have greater flow capacities than the requirements found by

calculation for extremely severe circumstances.

To address the sizing of orifices needed to relieve hydrostatic overpressure as defined above, an equation

for determining the discharge areas of such orifices is stated below:


2138 PP

G

KKK

QA

vwd

Where

A = required effective discharge area, in square inches

Q = flow rate, in US gallons per minute

Kd = effective coefficient of discharge (0.65 for hydrostatic overpressure-relief purposes)

Kw = correction factor due to back pressure (1.0 if back pressure is atmosphere or valve responds only to

pressure differential across its seat)

Kv = correction factor due to viscosity

G = specific gravity of the liquid at the flowing temperature

P1 = upstream relieving pressure in psig

P2 = total back pressure in psig (zero for discharge to atmosphere)

Q is determined by the relation:

GC

BHQ

500

Where

B = cubical expansion coefficient per degree Fahrenheit for the liquid at the expected temperature

H = total heat of absorption to the wetted bare surface of a vessel, pipe or container in BTU per hour

(H = 21,000 A0.82, where A = total wetted surface in square feet)

G = specific gravity of the liquid at the flowing temperature

C = specific heat of the trapped fluid in BTU per lb-°F

Kv is determined as follows:

Refer to Figure G1 below to find Kv as a function of the Reynolds number (R), which is defined by the following

equation:

AU

QR

12,700

Where

Q = flow rate at the flowing temperature in US GPM

U = viscosity at the flowing temperature in Saybolt Universal Seconds

A = effective discharge area, in square inches (from manufacturers’ standard orifice areas)


Figure G1: Capacity Correction Factor K Due to Viscosity

Figure G1 was reprinted by permission from Oil and Gas Journal, November 20, 1978 edition. Copyright 1978, Oil and Gas Journal.

http://ogj.pennnet.com/home.cfm.

G.2 Hydrostatic overpressure Relief of ASME Pressure Vessels

This section pertains to vessels covered by ASME B&PVC, Section VIII, Division 1, herein referred to as

ASME pressure vessels.

When ASME pressure vessels contain liquid refrigerant and can be isolated from the other portions of a

closed-circuit ammonia refrigeration system, the rules of Section 15.6 apply. However, when ASME

pressure vessels contain a non-boiling liquid (i.e., a liquid whose vapor pressure at maximum normal

operational, maintenance or standby conditions is less than the relief valve setting), specific requirements of

the ASME B&PVC, Section VIII, Division 1 for hydrostatic overpressure-relief valves apply:

a. Hydrostatic overpressure- relief valves protecting ASME

pressure vessels must bear an ASME UV Code Symbol Stamp. (Code Case BC94-620)

b. Hydrostatic overpressure-relief valves protecting ASME pressure vessels must be certified and rated for

liquid flow. (Code Case BC94-620)

c. Any liquid pressure relief valve used shall be at least NPS 1/2. (UG-128)

d. The opening through all pipe, fittings, and non-reclosing pressure relief devices (if installed) between a


pressure vessel and its pressure relief valve shall have at least the area of the pressure relief valve inlet. In

this upstream system, the pressure drop shall not reduce the relieving capacity below that required or

adversely affect the proper operation of the pressure relief valve. (UG-135 (b) (1))

e. The size of the discharge lines leaving a hydrostatic overpressure-relief valve shall be such that any

pressure that may exist or develop will not reduce the relieving capacity of the pressure relief valve below

that required to properly protect the vessel. (UG-135 (f))

f. The hydrostatic overpressure-relief valve shall be capable of preventing the pressure from rising more

than 10% above the maximum allowable working pressure during normal service or standby conditions.

G.3 Sample calculations

To illustrate how to apply these concepts and requirements, two examples of sizing hydrostatic

overpressure-relief valves for pressure-containing equipment are provided below.

NOTE:

These examples are for oil in the oil side of oil coolers rather than ammonia on the refrigerant side.

EXAMPLE 1: Sizing a Hydrostatic Overpressure-relief Valve for an ASME Pressure Vessel

Determine the hydrostatic overpressure-relief valve required to protect an oil cooler of diameter 10" and

length 12 feet with MAWP 400 psig.

Assume that the oil temperature is 100°F and that the oil viscosity (U) is 300 Saybolt Universal

Seconds at 100°F. From the oil manufacturer’s data, the cubical expansion coefficient (B) is 0.00043/°F,

specific gravity (G) is 0.87 and specific heat (C) is 0.5.

First, determine the bare wetted external area (A) of the oil cooler, in square feet:

2ft 33.81212

10.75 dlA

Next, determine total heat absorption (H) of the wetted bare surface of the oil cooler when exposed to

maximum normal conditions:

H = 21,000 A0.82

H = 21,000 × (33.8)0.82 = 376,644 Btu/Hr.

Next, determine rate of increase of the oil volume from the relation below:

GC

BHQ

500

𝑄 = 0.00043 𝑥 376,644/500 𝑥 0.87 𝑥 0.5 = 0.74 gpm


This is the volume flow of oil due to heat input. Hydrostatic overpressure relief valves are commonly rated on

water, so this value can be used, along with the design pressure differential and specific gravity, to determine a

required Cv for the relief based on the definition Cv.

DeltaP

avitySpecificGrQCv

Assume the relief valve will discharge into another part of the system having relief protection set at 300

psig. To prevent the pressure in the oil cooler from exceeding 400 psig under all conditions, the hydrostatic

overpressure-relief valve must be selected for 100 psi differential.

The required relief valve Cv is therefore:

100

87.074.0Cv = 0.069

A hydrostatic overpressure relief valve must therefore be selected with a minimum Cv of 0.069.

Note that this does not account for reduction in capacity due to inlet losses.

The equivalent GPM of water would then be 0.69 GPM (determined by solving the Cv equation for Q using

the required Cv, a 100 psi differential, and a specific gravity of 1).

A liquid-rated ASME certified relief valve is commercially available with 1/2" NPT inlet and 3/4" NPT

outlet. The valve’s capacity at 100 psi pressure differential is 25.9 gal per min, 37.5 times the water

equivalent oil volume rate of increase. The valve therefore meets ASME capacity requirements. Per the

ASME code, inlet and outlet pressure losses may total 40 psi and still meet code requirements.

EXAMPLE 2: Sizing a Hydrostatic Overpressure-relief Valve for a non-ASME equipment

Determine the orifice area required to protect an oil cooler with diameter 5" and length 12 feet with MAWP

400 psig.

Assume that the oil temperature is 100°F and oil viscosity (U) is 300 Saybolt Universal Seconds at 100°F.

From the oil manufacturer’s data, the cubical expansion coefficient (B) is 0.00043/°F, specific gravity (G) is

0.87 and specific heat (C) is 0.5.

First, determine the bare wetted external area of the oil cooler, in square feet:

2ft 17.481212

5.563 dlA

Next, determine total heat absorption of the wetted bare surface of the oil cooler when exposed to maximum

normal conditions from the relation:

H = 21,000 A0.82, outlined above.


H = 21,000 × (17.48)0.82 = 219,298 Btu/hr.

Next, determine rate of increase of the oil volume from the relation:

GC

BHQ

500

GC

BHQ

500

Next, determine the viscosity correction factor (Kv) from Figure G1 and the Reynolds number (R) from the

formula below:

AU

QR

12,700

To calculate R in this equation requires a value for A, which represents the orifice area. Interestingly, to

calculate A using the primary equation requires a value for R. To solve this problem, an iterative method

(trial and error) must be used. First, an approximate starting value of A must be estimated to obtain an

initial estimate of R, which can then be used in the primary equation to calculate a new value for A.

Comparing this calculated value of A to the initial approximation for A will enable an even better

approximation for A for the next iteration. This iterative process will converge on a calculated value for A

that is reasonably close to the final approximation for A. If it does not, more sophisticated mathematical

methods are required to solve the equations.

Try a 1/16" orifice having an area of 0.003068 in2.

3310.003068300

0.43312,700

R

From Figure G1, Kv = 0.825

2138 PP

G

KKK

QA

vwd

Assume the pressure differential to another part of the system (P1-P2) is 100 psi.

200198.0

100

87.0

825.0165.038

433.0inA

The required flow area is much smaller (0.00198 in2) than the area assumed in estimating the Reynolds

number (0.003068 in2). Therefore, a relief valve having a 1/16" diameter orifice is more than adequate.


For a second iteration, assume a 3/64" orifice with 0.0017 in2 cross-sectional area. R would then become

4450.0017300

0.43312,700

R

Kv = 0.85

200192.0100

87.0

85.0165.038

433.0inA

This area requirement is approximately 13% greater than that of the 3/64" orifice. Therefore, we can

conclude that an orifice between a diameter of 1/16" and 3/64" would be ideal. A 1/16" orifice will be more

than adequate.

G.4 Inlet and Outlet Piping

ASME B&PVC, Section VIII, Division 1 requires that hydrostatic overpressure-relief valve inlet piping for

ASME pressure vessels must have at least the area of the overpressure-relief valve inlet. Since the same

code requires a minimum NPS 1/2" valve, the minimum inlet piping is established. Inlet piping

requirements on larger hydrostatic overpressure-relief valves would follow suit.

On outlet piping, the B & PV Code simply requires that the relief valve discharge lines are large enough to

avoid reducing the relieving capacity of the pressure relief device below that required to properly protect

the vessel.

For normal over-pressure protection, ASME permits over-pressurization of a vessel to 10% above its

MAWP.

In the previous examples, the flows of liquid created by thermal expansion were very low. Consequently,

outlet piping from commercially available certified ASME liquid relief valves could usually be much

smaller than the nominal outlets of the valves themselves. For instance, consider the ASME vessel example

with a 0.74 gpm relief requirement. The relief valve suggested for this application has a 3/4" NPT

connection on the outlet. If, for example, the discharge piping is reduced to 1/2” in stainless steel tubing, the

Reynolds number for oil having a nominal viscosity of 68 centistokes at 100° F is less than 60 (57.9). In

laminar flow, which by definition is flow at or below Reynolds numbers of 2000, pressure loss to friction in

psi per 100 feet of smooth pipe is given as:

RD

GVh

2

f

43.3

Where

V = fluid velocity in ft/sec

G = specific gravity of fluid

R = Reynolds Number of fluid


D = I.D. of pipe in ft

From the previous example, oil flow due to thermal expansion is 0.74 gpm or 0.1 cfm. The 1/2" stainless

steel tubing has a cross-sectional flow area of 1.0085 x 10-3 ft2. Fluid velocity is therefore:

ft/sec 1.65101.008560

0.1ft/sec

60 3-

A

cfmV

Discharge piping pressure drop through the 1/2" stainless tubing would therefore be:

ft 100 / psi 49.30.035857.9

0.8671.6543.343.3 2

RD

GVh

2

f

For a typical relief valve discharge pipe run of 6 feet, pressure drop due to friction would be less than 3 psi.

Because ASME permits over-pressurization of 10% above the MAWP of a pressure vessel, inlet and outlet

losses could total 40 psi and meet ASME requirements. Therefore, hydrostatic overpressure-relief valve

outlet piping can be greatly reduced below the nominal outlet size of the relief valve selected in many cases.

Inlet and outlet piping for hydrostatic overpressure-relief valves protecting non-ASME equipment

containing incompressible non-refrigerants can be sized using identical techniques. In providing

overpressure protection against ambient warming, 10% over-pressurization above MAWP is permitted,

providing the relief valve is selected at MAWP.

Hydrostatic overpressure-relief devices may be located anywhere on the protected equipment. When used to

protect an ASME vessel, they must bear a UV Code Symbol. When used to protect a non-ASME

equipment, they must be listed by an approved nationally recognized testing laboratory or bear a UV Code

Symbol.


Appendix H. (Informative) Stress Corrosion Cracking




H.1 Background

Stress corrosion cracking (SCC) is a generic term describing the initiation and propagation of cracks that

can occur in metals when subjected to stress in the presence of an enabling chemical environment. The

stress can originate from an externally applied force, thermal stress, or residual stress from welding or

forming.

H.2 Carbon steel is susceptible to SCC when stressed in the presence of ammonia and oxygen. Ammonia SCC

has been recognized as a problem in the agricultural, chemical, and transport industries for many years.

Studies have shown that the following factors contribute to the likelihood of SCC:

• Material yield strength greater than 50 ksi

• Oxygen contamination

• Residual or applied stress

• Water content less than 0.2%

H.3 SCC in Ammonia Refrigeration Systems

SCC in ammonia refrigeration systems is less common, but there have been reports of SCC in vessels and

piping. Vessels seem to be more susceptible to SCC because of their higher material yield strengths and

residual fabrication stresses. High pressure receivers are particularly vulnerable due to their potential for

higher oxygen content (non-condensable) and lower water content but SCC has also been found in low

pressure vessels and piping.

Propagation of cracks via SCC is usually a gradual process. In ammonia refrigeration applications using

carbon steel materials, stress corrosion cracks typically propagate from surface or subsurface discontinuities

at the interior wall of a susceptible vessel or pipe. Sufficiently high stresses can propagate crack(s) through

the material to emerge as a “pinhole leak” on the external surface. Discovery of a “pinhole leak” on a vessel

is indicative of SCC and it is likely that additional cracks will be present in the same vessel. Repair of stress

corrosion cracks

is difficult and often not cost-effective.

H.4 Recommendations to Inhibit SCC in Ammonia Refrigeration Systems

The following recommendations are intended to minimize the likelihood of SCC for vessels constructed

from carbon steel for use in ammonia refrigeration systems.

• The presence of non-condensable gases (specifically, oxygen) increases the probability of SCC. As

such, purging of air from the system during both initial start-up and during operation and maintenance is

important.

• Post-weld heat treat (PWHT) all high temperature vessels, especially vessels such as high pressure


receivers, and intermediate and low temperature water chillers, intercoolers and economizers, to relieve the

residual stress of welding and forming. Where low temperature vessels are critical to the process, or may be

held at temperatures above 23°F (-5°C) for long periods of time, consideration should be given to PWHT.

EXCEPTIONS:

a. compressor oil separators

b. specialized vessels, such as plate heat exchangers, containing internal parts that could be damaged, e.g.

internal bushings, gaskets.

c. all oil recovery vessels, e.g. oil pots.

NOTE: PWHT may produce significant scale, which could cause operating problems in the system.

H.5 Refrigerant-grade anhydrous ammonia shall meet or exceed the requirements of the CGA G-2.


Appendix I. (Informative) Emergency Pressure Control Systems




Emergency Pressure Control System Design and Installation Guidelines

I.1 General

I.1.1 Purpose. This technical guideline describes requirements for Emergency Pressure Control Systems

(EPCS), which provide a means of internally mitigating an overpressure event in a refrigeration system that

is independent of other required safety features and functions prior to operation of a pressure relief device.

I.1.2 Scope. Emergency Pressure Control Systems used as a means to mitigate an overpressure event

involving an ammonia refrigeration system should comply with this technical guideline.

I.1.3 Limitations. An EPCS does not reduce or eliminate requirements for pressure relief devices set forth in

other codes and standards.

I.2 Definitions

Crossover valve is a valve that allows interconnection of two different portions of a refrigeration system

that normally operate at different pressures.

Emergency pressure control system (EPCS) is a system consisting of pressure sensors, independent

compressor cut-off controls and automatically controlled crossover valves that will permit a high-pressure

portion of a system to connect to a lower pressure portion of a system when opened.

Header is a pipe to which other pipes or tubes are connected.

High-side consists of those portions of a mechanical refrigeration system that are subjected to approximate

condenser pressure.

Low-side consists of those portions of a mechanical refrigeration system that are subjected to approximate

evaporator pressure.

Pressure sensor is a mechanical or electronic device that measures ammonia pressure.

Seep is a nuisance loss of refrigerant from a relief valve that can occur when the vessel pressure approaches

the relief pressure setting, or a nuisance loss of refrigerant from a relief valve that can occur after the valve

discharges if the valve does not fully re-seat.

Zone is a general term used to identify a pressure level or temperature level of a refrigeration system. A

zone will be associated with a compressor or group of compressors and the associated vessels serving a

common pressure level. The term does not pertain to individual temperature controlled areas or rooms

served by one or more compressor.


I.3 Referenced Standards

I.3.1 International Fire Code (IFC), Section 606.10.

I.4 EPCS Recommended. Each zone should be provided with an EPCS. Each EPCS, other than the lowest

pressure zone, should include a crossover valve to allow an abnormally high pressure to be discharged to a lower

pressure zone.

I.4.1 Design and Installation Recommendations

I.4.2 Crossover Valve Connections.

I.4.2.1 Crossover valves should be connected to locations that will allow pressure in each high pressure

zone to discharge to a lower pressure zone. Connections between pressure zones should continue in the

above-described manner until all major pressure zones in a system are connected with the EPCS,

always with the intended flow traveling from a high pressure to a lower pressure.

I.4.2.2 Where multiple low-pressure zones are present, low-pressure zones with the highest pressure

should be connected to the next lowest pressure zone.

I.4.2.3 Crossover valve connections should not be to pipes or tubes conveying liquid refrigerant.

I.4.2.4 High pressure crossover valve connections should come from the top of a dry suction header,

compressor discharge header or other main gas header.

I.4.2.5 Low pressure crossover valve connections should discharge to the vapor space in a receiving

vessel or to a common vapor header serving multiple receiving vessels.

I.4.2.6 The designer of a refrigeration system should consider the ability of the low pressure portion of

the system to receive the high pressure discharge from the EPCS crossover valve. Operation of the

crossover valve should not cause a release of refrigerant from pressure relief devices on the low

pressure portion of the system.

I.4.2.7 Crossover valves and connecting piping and valves should have a minimum nominal size of 1-

inch.

I.4.2.8 Piping and tubing associated with a crossover valve should be independent of any other

connections. The connection should not be in the same pipe or tube where a pressure relief device is

connected.

I.4.3 Crossover Valve Type and Status Monitoring. The crossover valve should be of a type that fully opens

when activated. Where the status of power to the valve cannot be readily verified, an indicator light is

recommended to show whether power is supplied to the valve.

I.4.4 Isolation Valves

I.4.4.1 Each crossover valve should be provided with a stop valve on either side to allow isolation of

the crossover valve for maintenance.

I.4.4.2 Isolation valves should be locked in the open position during normal operations.


I.4.5 System Operation

I.4.5.1 The EPCS should be arranged for automatic operation.

I.4.5.2 Where required by the fire department, the EPCS should be provided with a remote switch for

manual activation.

I.4.5.3 An EPCS should be arranged to activate at a pressure not greater than 90 percent of the pressure

relief device setting.

I.4.5.4 A dedicated, independent mechanical pressure switch or a combination of a mechanical and

electronic pressure-sensing device dedicated to the EPCS should be provided to activate each EPCS.

I.4.5.5 Pressure sensing equipment should continuously monitor pressure in the refrigeration system

adjacent to each crossover valve.

I.4.5.6 When a pressure sensor reaches the EPCS activation pressure, all of the following should occur:

1) All compressors supplying the pressure zone that is in an over-pressure condition should be

stopped by a means that is independent of all other safety controls,

2) Associated crossover valves should open, and

3) Condenser fans and pumps should be stopped if the system pressure falls below 90 psig.

I.4.5.7 A means should be provided to signal personnel responsible for refrigeration system

maintenance that an EPCS has been activated.

I.4.5.8 Once an EPCS has been activated, it should remain active until manually reset.

I.4.6 Inspection and Maintenance

I.4.6.1 General. EPCS crossover valves and isolation valves should be inspected and tested on an

annual basis to verify proper operation.

I.4.7 Written Procedures

I.4.7.1 General. Written procedures should be in place to describe the operation of the EPCS.

Procedures should address the importance of maintaining isolation valves in the full open position

unless maintenance is being performed on the crossover valve.

Considerations for Pressure Set Points

Seep through a relief valve is nuisance refrigerant loss due to pressure differential conditions across the valve or dirt

and debris located at the seat. Seep is measured in bubbles per minute and can vary from manufacturer, design, type

of seat material, pressure differential across relief, amount of dirt that is trapped after a relief discharges, and age of

the relief valve. Relief valves are set with a tolerance of +/- 3%, but when these reliefs are stored or left in operation

for a long period of time, the reliefs can begin to seep at larger tolerances. In some cases, seep has occurred when


pressure increases to within 10% of relief set pressure.

One method to prevent seep, is to maintain a pressure on the relief valve of 90% or less of the rated relief valve

pressure setting. When pressures higher than 90% of rated relief valve pressure setting are anticipated, it is

possible to select soft seats that are bubble tight at higher pressures. Rupture disks in combination with a relief

valve will result in tighter tolerances.

The following tables show examples of typical tolerances and pressures associated with relief valves and the

EPCS.

TABLE I-1

Typical Set Point Values and Tolerances

for a 300 psig System

Relief Full Open (+10%) 330 psig

+3% tolerance 309 psig

Relief Valve Set Point 300 psig

-3% tolerance 291 psig

Potential seep point (-10%) 270 psig

EPCS set point 250 psig to 270 psig

(EPCS set point is equal or below the seep point)

Design System Operating Pressure (-25%) 225 psig

(System operating pressure should be

25% lower than the relief valve setting

when selecting relief valves)

Compressor off set point 225 psig


TABLE I-2

Typical Set Point Values and Tolerances

for a 250 psig System

Relief Full Open (+10%) 275 psig

+3% tolerance 257.5 psig

Relief Valve Set Point 250 psig

-3% tolerance 242.5 psig

Potential seep point (-10%) 225 psig

(EPCS set point is equal or below the seep point)

EPCS set point 210 psig to 225 psig

Design System Operating Pressure (-25%) 200 psig

(System operating pressure should be

25% lower than the relief valve setting

when selecting relief valves)

Compressor off set point 200 psig


Appendix J. (Informative) Machine Room Signs

This appendix is not part of this standard. It is merely informative and does not contain requirements necessary

for conformance to the standard. It has not been processed according to the ANSI requirements for a standard and

may contain material that has not been subject to public review or a consensus process.

Key to door signage:

J.1 Refrigeration Machinery Room – Authorized Personnel Only

Color: Black Text, Yellow Background

Location: All entrances to Machinery Room

J.2 Caution – Ammonia R-717



J.3 Caution – Eye and Ear protection must be worn in this area



J.4 Warning – When alarms are activated, ammonia has been detected

1. Leave room immediately when alarms are activated

2. Do not enter except by emergency trained personnel only

3. Do not enter without personal protective equipment


J.5 Refrigeration Machinery Shutdown, Emergency use only

Color: Black Text, Orange Background

Location: Designated principal exterior machinery room door.

J.6 Refrigeration Machinery Room: Refrigeration Ventilation, Emergency use only

Color: Black Text, Orange Background

Location: Designated Principal Exterior Machinery Room Door, also can be used for remote ON / OFF /

AUTO ventilation switch.

J.7. NFPA 704 – Ammonia Fire Diamond

Color: Black Text, White, Blue, Red & Yellow Background


1. Warning for Indoor Ammonia Refrigeration Equipment: 3-3-0

This includes all entrances to a Machinery Room

2. Warning for Outdoor Ammonia Refrigeration Equipment: 3-1-0

This is for equipment located entirely outdoors

The following example of the Principal and Auxiliary Machinery Room doors are provided for reference only.




Appendix K. (Informative) Alternative Ventilation Calculation Methods

This appendix is not part of this standard. It is merely informative and does not contain

requirements necessary for conformance to the standard. It has not been processed according to

the ANSI requirements for a standard and may contain material that has not been subject to

public review or a consensus process.

K.1 General

The Exception to Section 6.14.8 describes alternative ventilation methods which are available for

ammonia (NH₃ ) refrigeration systems. This appendix (informative) contains sample calculations

for the design of alternative ventilation methods.

K.2 Sample Calculation: 30 ACH for Emergency Ventilation Rate

K.2.1 Design the ventilation system for an ammonia refrigeration skid package which contains 450

pounds of anhydrous ammonia (G) and is located in a machinery room which has a volume (V)

of 100,000 cubic feet (ft3).

K.2.2 The emergency ventilation rate equation (30 ACH = 0.5 air changes/minute):

Q = V x 0.5 (changes/min)

Where

Q = airflow in ft3/min

V = room volume in ft3

For this example:

Q = (100,000 ft3) x 0.5 (changes/min) = 50,000 ft3/min

K.3 Sample Calculations: Demonstrate that ammonia concentrations will never exceed 40,000 ppm

[25% of the Lower Flammability Limit (LFL)].

K.3.1 Demonstrate that the ammonia concentrations would never exceed 40,000 ppm if 100 pounds of

anhydrous ammonia (G) were released from an ammonia refrigeration skid package located in a

machinery room which has a volume (V) of 100,000 cubic feet (ft3).

K.3.2 The following equation can be used to demonstrate that the ammonia concentrations would never

exceed 40,000 ppm:

C = G x (Vapor Sp. Vol.) x (100%) / V

Where

C = volumetric concentration of ammonia in %


G = amount of ammonia released in the room in pounds (lbs). For the purposes of these

calculations it is assumed that the entire ammonia inventory is released and vaporized inside the

machinery room.

Vapor Sp. Vol. = the vapor specific volume for anhydrous ammonia in ft3/lb

V = room volume in ft3

Vapor Specific Volumes @ 15 psia

Temperature (°F) Specific Volume (ft3/lb)

40 20.6880

60 21.5641

80 22.4338

100 23.2985

For this example:

C = (100 lbs) x (22.4338 ft3/lb. at 80oF) x (100%) / (100,000 ft3) = 2.24%

The LFL for anhydrous ammonia is typically considered to be to 16% (160,000 ppm). 25% of

the LFL is 4% (40,000 ppm). Thus, under steady state conditions, the ammonia concentration

inside the machinery room (2.24%) would not exceed 40,000 ppm, even if the entire ammonia

charge were released and vaporized within the machinery room.

K.3.3 Even though the calculations demonstrate that under steady-state conditions the ammonia

concentrations would never exceed 40,000 ppm, it is recommended that an emergency

ventilation system be provided in the machinery room in this example. The emergency

ventilation rate used would be at the discretion of the designer(s).

K.4 Sample Calculations: Provide Localized (Spot) Ventilation designed to maintain ammonia

concentrations below 40,000 ppm.

K4.1 Design a localized (spot) ventilation system for an ammonia refrigeration skid package which

contains 250 pounds of anhydrous ammonia (G) and is located in a machinery room which has a

volume (V) of 100,000 cubic feet (ft3) which will maintain the ammonia concentrations below

40,000 ppm. Assume temperature to be 60°F.

K4.2 The following equation can be used to calculate the ventilation rate for a localized (spot)

ventilation system which will maintain the ammonia concentrations below 40,000 ppm. The

derivation of this equation and an explanation of its use can be found in Chapter 4, Section 4.5

(General Industrial Ventilation) from ACGIH®, Industrial Ventilation: A Manual of

Recommended Practice for Design, 27th Edition. Copyright 2010. Reprinted with permission.

Q = [403 x SG x 100% x ER x Sf] / [MW x LFL x B]


Where

Q = airflow in ft3/min

SG = specific gravity of ammonia liquid (SG = 0.62 @ 60°F per IIAR Ammonia Data Book)

ER = evaporation rate of liquid in pounds per minute (lbs/min). For the purposes of these

calculations it is assumed that the entire ammonia inventory is released and vaporized inside the

machinery room over a 10 minute period, i.e. 250 pounds over a 10 minute period (25 lbs/min).

Convert 25 lbs/min to pints/min

1 pint = 0.01671 ft³

NH₃ liquid @ 60°F = 38.54 lbs/ft³

ER = 25 lbs/min x ft³/38.5416 x pint/0.01671 ft³ = 38.82 pints/min

Sf = a safety coefficient that depends on the percentage of the LFL necessary for safe

conditions. Since it has been found desirable to maintain vapor concentrations of not

more than 40,000 ppm, a Sf coefficient of 4 (25% of the LFL) will be used for these

calculations.

MW = the molecular weight of ammonia liquid (MW = 17.03 per IIAR Ammonia Data

Book)

LFL = the lower flammability limit for ammonia (LFL = 16% per IIAR Ammonia Data

Book)

B = a constant that takes into account the fact that the LFL decreases at elevated

temperatures. B = 1 for temperatures up to 250oF; B = 0.70 for temperatures above to

250oF, though it is unlikely that temperatures above 250oF would ever be applicable for

an ammonia refrigeration system.

For this example:

B = 1

Q = [(403) x (0.62 @ 60oF) x (100%) x (38.82 pints/min) x (4)] / [(17.03) x (16%) x (1)]

Q = 14,238.9 ft3/min

K.4.3 Chapter 4 of Industrial Ventilation – A Manual of Recommended Practice for Design provides

guidance dilution ventilation principles that should be followed when designing localized (spot)

ventilation systems. These principles include:

K.4.3.1 Locate the exhaust openings near the sources of contamination, if possible, in order to

obtain the benefit of “spot ventilation.”


K.4.3.2 Locate the air supply and exhaust outlets such that the air passes through the zone of

contamination. The operator should remain between the air supply and the sources of the

contaminant.

K.4.3.3 Replace the exhausted air by use of a replacement air system.

K.4.3.4 Avoid re-entry of the exhausted air by discharging the exhaust high above the roof line

and by ensuring that no window, outdoor air intakes, or other such openings are located near the

exhaust discharge.


Appendix L. (Informative) Pipe, Fittings, Flanges, and Bolting

The following Materials and Minimum Pipe Wall Thickness criteria have historically been

commonly used in the ammonia refrigeration industry for ammonia Pipe, Fittings, Flanges and

Bolting. See Appendix N for cited references.

A. Materials:

1) Pipe

Carbon steel: ASTM A53 — Grade A or B, Type E or S

Carbon steel: ASTM A106 — Grade A or B

Stainless steel: ASTM A312 — Type 304, 304L, 316, or 316L

Carbon steel (low temperature): ASTM A333 — Grade 1 or 6.

Carbon steel pipe, ASTM A53 or A106 is permitted to be used below -20°F if it meets

ASME B31.5.

2) Fittings

Carbon steel: ASTM A105


Stainless steel: ASTM A403

Carbon steel (low temperature): ASTM A420.

3) Flanges



Stainless steel: ASTM A403

Carbon steel (low temperature): ASTM A707

4) Bolting

Cast Iron flanges when used with ring gaskets, or when coupled to a raised-face flange:

ASTM A307 Grade B

Carbon or Stainless Steel Flanges down to -55°F: ASTM A193 Grade B7


Low-temperature applications (-55°F to -150°F): ASTM A320 Grade L7

Nuts for above materials: ASTM A194Appendix N, in accordance with the bolting material

requirements listed in the standards referenced above.

NOTE: The above materials refer to those common materials in joining piping flanges only. These

materials or other commonly used qualifying materials selected for a safe design are permitted for bolts

and studs for equipment closures, valve bonnet-body connection, etc.

B. Minimum Pipe Wall Thickness:

1) Carbon Steel: Welded.

1.1) 1 ½ inch and smaller - schedule 80

1.2) 2 inch through 6 inch - schedule 40 or Perform Engineering Analysis for

Requirement

1.3) 8 inch and larger - Perform Engineering Analysis for Requirement

2) Stainless Steel: Welded.

2.1) 1 ½ inch and smaller - schedule 40

2.2) 2 inch through 6 inch - schedule 40 or Perform Engineering Analysis for

Requirement

2.3) 8 inch and larger - Perform Engineering Analysis for Requirement

3) Carbon and Stainless Steel: Threaded.

3.1) Minimum schedule 80 for all sizes


Appendix M. (Informative) Operational Containment

Operational Containment is defined as an optional control sequence wherein all ventilation for a room is

de-energized so that ammonia vapor is retained in the room.

Operational Containment is a rare strategy as an alternative ventilation method where there are sensitive

off site receptors, such as densely-populated areas, nursing homes, or schools. The design should be

handled on a case-by-case basis for definition of appropriate criteria for application and design as a

variance to the standard practices defined in IIAR 2.

An ammonia detection system meeting the requirements of Chapter 17 and a ventilation system meeting

the requirements of Section 6.14.8 should be provided, at a minimum.

An Operational Containment includes at a detection level determined by the site refrigeration

management designee, emergency responders, and/or owner. A pre-determined procedure should be

developed to ensure that personnel are not located within the machinery room before Operational

Containment is initiated. The procedure should include the following at a minimum:

A. Provide an “ON / OFF / AUTO” override for emergency ventilation at a secured remote location

that can be used for Operational containment shutdown of the ventilation system.

B. Automatically de-energize all unclassified electrical equipment at the detection of ammonia

vapor concentrations that exceeds the detector’s upper detection limit or 40,000 ppm (25% LFL),

whichever is higher or upon stopping ventilation using manual controls.

C. Equipment or controls that must remain energized for monitoring or controlling equipment

should be designed for operation in a hazardous location.

D. Airflow dampers on fans, air inlets and air outlets should close when an Operational

Containment is actuated.


Appendix N. (Informative) References and Sources of References

1.0 Informative References

1.1 American Conference of Governmental Industrial Hygienists (ACGIH), Industrial Ventilation, A

Manual of Recommended Practice for Design, 27th Edition (February 2010), Chapter 4, Section 4.5

(General Industrial Ventilation).

1.2 American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. (ASHRAE),

ASHRAE Handbook (2013), Fundamentals, Chapter 14, Climate Design Information.

1.3 American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. (ASHRAE),

ANSI/ASHRAE Standard 15-2013, Safety Standard for Refrigeration Systems.

1.4 American Society of Testing and Materials (ASTM), editions as shown below:

ASTM A53/A53M-12, Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-

Coated, Welded and Seamless;

ASTM A105/A105M-13, Standard Specification for Carbon Steel Forgings for Piping

Applications;

ASTM A106/A106M-13, Standard Specification for Seamless Carbon Steel Pipe for High-

Temperature Service;

ASTM A181/A181M-13, Standard Specification for Carbon Steel Forgings, for General-

Purpose Piping;

ASTM A193/A193M-12b, Standard Specification for Alloy-Steel and Stainless Steel Bolting

Materials for High-Temperature Service;

ASTM A194/A194M-13, Standard Specification for Carbon and Alloy Steel Nuts for Bolts for

High-Pressure and High-Temperature Service, or Both;

ASTM A234/A234M-11a, Standard Specification for Piping Fittings of Wrought Carbon Steel

and Alloy Steel for Moderate and High Temperature Service;

ASTM A307-12, Standard Specification for Carbon Steel Bolts, Studs, and Threaded Rod

60,000 PSI Tensile Strength;

ASTM A312/A312M-13b, Standard Specification for Seamless, Welded, and Heavily Cold

Worked Austenitic Stainless Steel Pipes;

ASTM A320/A320M-11a, Standard Specification for Alloy-Steel and Stainless Steel Bolting for

Low-Temperature Service;

ASTM A333/A333M-11, Standard Specification for Seamless and Welded Steel Pipe for Low-

Temperature Service;


ASTM A403/A403M-13a, Standard Specification for Wrought Austenitic Stainless Steel Piping

Fittings;

ASTM A420/A420M-13, Standard Specification for Piping Fittings of Wrought Carbon Steel

and Alloy Steel for Low-Temperature Service;

ASTM A707/A707M-13, Standard Specification for Forged Carbon and Alloy Steel Flanges for

Low-Temperature Service.

1.5 Environmental Protection Agency, 40 CFR Part 68, Accidental Release Prevention

Requirements: Risk Management Programs Under Clean Air Act, 2004.

1.6 International Fire Code (IFC), Section 606.10, Emergency Pressure Control System, 2012.

1.7 International Institute of Ammonia Refrigeration (IIAR):

Process Safety Management & Risk Management Program Guidelines, 2012;

The Ammonia Refrigeration Management Program (ARM), 2005;

IIAR Piping Handbook, Insulation for Refrigeration Systems, Chapter 7, 2004.

IIAR Bulletin No. 114 Identification of Ammonia Piping and System Components, 2014.

1.9 Occupational Safety and Health Administration (OSHA), U.S. Department of Labor, 2012:

29 CFR 1910.119, Process Safety Management of Highly Hazardous Chemicals;

29 CFR 1910 Subpart D, Walking-Working Surfaces;

29 CFR 1910.24, Fixed Stairs;

29 CFR 1910.27, Ladders;

29 CFR 1910.147, Control of Hazardous Energy, (“Lockout/Tagout”);

29 CFR 1910.37(b), Maintenance, Safeguards, and Operational Features for Exit Routes.


2.0 Sources of References (Informative)

2.1 American Conference of Governmental Industrial Hygienists (ACGIH).

1330 Kemper Meadow Drive, Suite 600

Cincinnati, OH 45240

www.acgih.org

2.2 American National Standards Institute (ANSI).

25 West 43rd Street, 4th Floor

New York, NY 10036

www.ansi.org

2.3 American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. (ASHRAE).

1791 Tullie Circle, N.E.

Atlanta, GA 30329

www.ashrae.org

2.4 American Society of Mechanical Engineers (ASME).

ASME International

Three Park Avenue

New York, NY 10016-5990

www.asme.org

2.5 American Society of Testing and Materials (ASTM).

ASTM International

100 Barr Harbor Drive

P.O. Box C700

West Conshohocken, PA 19428-2959

www.astm.org

2.6 Environmental Protection Agency

1200 Pennsylvania Avenue, N.W.

Washington, DC 20460

www.epa.gov

2.7 International Institute of Ammonia Refrigeration (IIAR).

1001 North Fairfax Street, Suite 503

Alexandria, VA 22314

www.iiar.org

2.9 National Fire Protection Association (NFPA).

60 Batterymarch Park

Quincy, MA 02169-7471

www.nfpa.org


2.10 U. S. Department of Labor/OSHA.

Publications Department

200 Constitution Avenue, NW, Room N3101


www.osha.gov

2.11 U. S. Department of Transportation (US DoT).

Research and Special Programs Administration

Office of Hazardous Materials Safety

400 7th Street, S.W.


www.dot.gov