NFPA 651Standard for the

Machining and Finishingof Aluminum and the

Production and Handlingof Aluminum Powders

1998 Edition

National Fire Protection Association, 1 Batterymarch Park, PO Box 9101, Quincy, MA 02269-9101An International Codes and Standards Organization

Copyright ©

National Fire Protection Association, Inc.

One Batterymarch Park

Quincy, Massachusetts 02269

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651–1

Copyright © 1998 NFPA, All Rights Reserved

NFPA 651

Standard for the

Machining and Finishing of Aluminum and the Production and Handling of Aluminum Powders

1998 Edition

This edition of NFPA 651, Standard for the Machining and Finishing of Aluminum and the Pro-duction and Handling of Aluminum Powders, was prepared by the Technical Committee on Com-bustible Metals and Metal Dusts and acted on by the National Fire Protection Association,Inc., at its Annual Meeting held May 18–21, 1998, in Cincinnati, OH. It was issued by the Stan-dards Council on July 16, 1998, with an effective date of August 5, 1998, and supersedes allprevious editions.

This edition of NFPA 651 was approved as an American National Standard on August 6,1998.

Origin and Development of NFPA 651NFPA 651, Manufacture of Aluminum Powder, was originally prepared by the Committee on

Dust Explosion Hazards in 1938 and 1939. It was first adopted in 1939, and revised in 1946,1952, 1959, 1963, 1967, and 1972. The 1967 edition was approved by the American NationalStandards Institute in 1967 and designated ANSI Z12.11.

NFPA 652, Plants Producing or Handling Magnesium Powder , was originally prepared by theCommittee on Dust Explosion Hazards in 1942 and was first adopted in 1944. Amendmentswere adopted in 1945, 1946, 1952, 1959, and 1968. The 1968 edition was approved by theAmerican National Standards Institute in 1968 and designated ANSI Z12.15.

In 1973, NFPA 651 and 652 were combined into a single standard, NFPA 651-T, and ten-tatively adopted at the 1973 Annual Meeting and officially adopted at the 1974 Annual Meet-ing. Revisions were adopted in 1980 and 1987.

For the 1993 edition, the Committee added definitions; clarified the requirements for thelocation of aluminum powder production plants; and revised the requirements for electricalpower, machinery, and operations, and for in-plant conveying of aluminum powder includingthe provisions for inert conveying. The requirements for explosion venting, manual fire fight-ing, and automatic sprinkler protection were also updated. This included the change in ter-minology from “light metal powder” to “aluminum powder” to emphasize that therequirements for the manufacture of magnesium powder were incorporated into the 1993edition of NFPA 480, Standard for the Storage, Handling, and Processing of Magnesium Solids andPowders. The Committee also incorporated various style and editorial revisions to comply withthe NFPA Manual of Style and to assist in making the document more usable, adoptable, andenforceable.

This edition of NFPA 651 represents a complete revision that incorporates the require-ments of NFPA 65 and 651 into a combined document. This new edition reduces redundancyand ensures that a consistent approach is applied to protecting against similar hazards. Thenew format also provides users with a single reference source for requirements in these oper-ations.

651–2 MACHINING AND FINISHING OF ALUMINUM AND THE PRODUCTION AND HANDLING OF ALUMINUM POWDERS

199

Technical Committee on Combustible Metals and Metal Dusts

Waldemar Seton, Chair SJO Consulting Engr, OR [SE]

Roy E. Adams, TIMET, NV [M]Rep. Int’l Titanium Assn.

Tom Christman, Lockheed Martin Energy Systems, TN [U]R. Thomas Currin, Postin Products, Inc., NC [U]Joseph A. Domanico, U.S. Dept. of the Army, MD [RT]John A. Gatchell, Wah Chang, Albany, OR [M]

Ralph W. Hawk, Cyprus Foote Mineral Co., NC [U]Kevin M. Laporte, Uni-Wash/Polaris, MI [M]John E. McConaghie, Reade Mfg. Co., NJ [U]David L. Oberholtzer, Valimet, Inc., CA [M]

Rep. The Aluminum Assn.John Valiulis, Factory Mutual Research Corp., MA [I]

Alternates

W. Anthony Major, Silberline Mfg. Co., Inc., PA [M](Alt. to D. L. Oberholtzer)

Larry J. Moore, Factory Mutual Research Corp., CO [I](Alt. to J. Valiulis)

Nonvoting

Thomas J. Matesic, Reactive Metals & Alloys Corp., PA Albert Muller, Lebanon, NJ(Member Emeritus)

Martha H. Curtis, NFPA Staff Liaison

This list represents the membership at the time the Committee was balloted on the text of this edition. Since that time, change s inthe membership may have occurred. A key to classifications is found at the back of this document.

NOTE: Membership on a committee shall not in and of itself constitute an endorsement of the Association or anydocument developed by the committee on which the member serves.

Committee Scope: This Committee shall have primary responsibility for documents on safeguards against fire andexplosion in the manufacturing, processing, handling, and storage of combustible metals, powders, and dusts.

8 Edition

CONTENTS 651–3

1998 Edition

Contents

Chapter 1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . 651– 4

1-1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651– 4

1-2 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651– 4

1-3 Equivalency . . . . . . . . . . . . . . . . . . . . . . . . . . . 651– 4

1-4 Applicability . . . . . . . . . . . . . . . . . . . . . . . . . . . 651– 4

1-5 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651– 4

Chapter 2 Aluminum Powder Production Plants . . . . 651– 5

2-1 Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651– 5

2-2 Building Construction . . . . . . . . . . . . . . . . . . . 651– 5

2-3 Machinery and Operations . . . . . . . . . . . . . . . 651– 6

2-4 Handling and Conveying of AluminumPowder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651– 6

2-5 Powder Collection . . . . . . . . . . . . . . . . . . . . . . 651– 7

2-6 Storage of Aluminum Powder . . . . . . . . . . . . . 651– 8

Chapter 3 Aluminum Powder Handling and Use . . . . 651– 8

3-1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651– 8

3-2 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651– 8

3-3 Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651– 8

3-4 Machinery and Operations . . . . . . . . . . . . . . . 651– 8

3-5 Transfer Operations. . . . . . . . . . . . . . . . . . . . . 651– 8

3-6 Prevention of Fugitive Dust Accumulations . . . . . . . . . . . . . . . . . . . . . . . . . 651– 8

Chapter 4 Processing and Finishing Operations . . . . 651– 9

4-1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651– 9

4-2 Dust-Producing Operations . . . . . . . . . . . . . . . 651– 9

4-3 Dust Collection Ducts and Ductwork. . . . . . . . 651– 9

4-4 Wet-Type Dust Collectors . . . . . . . . . . . . . . . . . 651– 9

4-5 Dry-Type Dust Collectors . . . . . . . . . . . . . . . . . 651–10

4-6 Recycling of Exhaust Air . . . . . . . . . . . . . . . . . 651–10

4-7 Machining and Sawing Operations . . . . . . . . . 651–10

4-8 Electrical Equipment . . . . . . . . . . . . . . . . . . . . 651–10

Chapter 5 Housekeeping . . . . . . . . . . . . . . . . . . . . . . 651–105-1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651–105-2 Cleanup Procedures for Fugitive Dust

Accumulations. . . . . . . . . . . . . . . . . . . . . . . . . 651–105-3 Vacuum-Cleaning Systems . . . . . . . . . . . . . . . 651–115-4 Compressed Air Cleaning Requirements . . . . 651–115-5 Water Cleaning Requirements . . . . . . . . . . . . 651–115-6 Cleaning Frequency . . . . . . . . . . . . . . . . . . . . 651–11

Chapter 6 Fire Prevention, Protection, and Procedures . . . . . . . . . . . . . . . . . . . . . . . . 651–11

6-1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651–116-2 Extinguishing Agents and Application

Techniques for Use on CombustibleAluminum Dusts . . . . . . . . . . . . . . . . . . . . . . . 651–11

6-3 Solvent-Wetted Powders . . . . . . . . . . . . . . . . . 651–116-4 Automatic Sprinkler Protection . . . . . . . . . . . 651–126-5 Fire-Fighting Organization . . . . . . . . . . . . . . . 651–126-6 Employee Training Program . . . . . . . . . . . . . 651–126-7 Control of Ignition Sources . . . . . . . . . . . . . . 651–126-8 Compressed Air Fittings . . . . . . . . . . . . . . . . . 651–12

Chapter 7 Safety Procedures . . . . . . . . . . . . . . . . . . . 651–127-1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651–127-2 Personal Protective Equipment. . . . . . . . . . . . 651–127-3 Emergency Procedures . . . . . . . . . . . . . . . . . . 651–137-4 Safety Inspection . . . . . . . . . . . . . . . . . . . . . . . 651–137-5 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . 651–13

Chapter 8 Referenced Publications. . . . . . . . . . . . . . 651–13

Appendix A Explanatory Material . . . . . . . . . . . . . . . 651–13

Appendix B Electrically Conductive Floors . . . . . . . . 651–20

Appendix C Referenced Publications. . . . . . . . . . . . . 651–20

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651–21

651–4 MACHINING AND FINISHING OF ALUMINUM AND THE PRODUCTION AND HANDLING OF ALUMINUM POWDERS

NFPA 651

Standard for the

Machining and Finishing of Aluminumand the Production and Handling

of Aluminum Powders

1998 Edition

NOTICE: An asterisk (*) following the number or letter des-ignating a paragraph indicates that explanatory material onthe paragraph can be found in Appendix A.

Information on referenced publications can be found inChapter 8 and Appendix C.

Chapter 1 General

1-1 Scope.

1-1.1* This standard shall apply to manufacturing facilitiesthat produce aluminum flake powder, aluminum paste, atom-ized aluminum powder or aluminum granules, or any alumi-num alloy powder that is combustible or explosible in anambient atmosphere.

1-1.2 This standard also shall apply to operations where alu-minum or aluminum alloys are subjected to processing or fin-ishing operations that produce fine metallic powder or dust.Such operations include, but are not limited to, machining,sawing, grinding, buffing, and polishing.

1-1.3 This standard also shall apply to the handling and stor-age of combustible aluminum dusts, aluminum powders, oraluminum pastes by users of such material.

1-1.4 This standard does not apply to the transportation ofcombustible aluminum dusts, aluminum powders, or alumi-num pastes on public highways, waterways, or by air or rail.

1-1.5 This standard does not apply to the primary productionof aluminum metal.

1-2 Purpose. The objective of this standard is to minimize theoccurrence of and resulting damage from fire and explosionin areas where combustible aluminum dusts, aluminum pow-ders, or aluminum pastes are manufactured, produced, han-dled, and stored.

1-3 Equivalency. Nothing in this standard shall be intendedto prevent the use of systems, methods, or devices of equiva-lent or superior quality, strength, fire resistance, effectiveness,durability, and safety over those prescribed by this standard,provided technical documentation is made available to theauthority having jurisdiction to demonstrate equivalency, andthe system, method, or device is approved for the intendedpurpose.

1-4 Applicability.

1-4.1 The provisions of this document shall be considerednecessary to provide a reasonable level of protection from lossof life and property from fire and explosion. They reflect situ-ations and the state-of-the-art prevalent at the time the stan-dard was issued. Unless otherwise noted, it shall not beintended that the provisions of this document be applied tofacilities, equipment, structures, or installations that were

existing or approved for construction or installation prior tothe effective date of the document, except in those caseswhere it is determined by the authority having jurisdiction thatthe existing situation involves a distinct hazard to life or adja-cent property.

1-4.2 Existing plants, equipment, structures, and installationsthat do not comply strictly with the requirements of this stan-dard shall be considered to be in compliance if it can be shownthat an equivalent level of protection has been provided orthat no specific hazard will be created or continued throughnoncompliance.

1-4.3 This standard is not intended to prevent use of systems,methods, or devices that provide equivalent protection fromfire and explosion. NFPA 69, Standard on Explosion PreventionSystems, shall be referred to when considering the use ofoptional systems.

1-5 Definitions.

Aluminum Chips.* Particles produced from a cutting,machining, or grinding operation that are not oxidized andthat are not diluted by noncombustible materials.

Aluminum Flake. See Aluminum Powder.

Aluminum Granules. Aluminum powders, generally largerthan 200 mesh (i.e., material not passing a U.S. No. 200 Stan-dard Sieve, 75 microns).

Aluminum Paste. Aluminum flake pigment homoge-neously incorporated in a solid or liquid carrier in such away so as to have a nonflowing product without a free-flowing liquid.

Aluminum Powder. Aluminum powder can be divided intothree broad classifications: atomized, flake, and granules. Thelength, width, and thickness of an atomized particle or gran-ule are all of approximately the same order; the length dimen-sion probably not exceeding two or three times the thicknessdimension. The length or width of a flake particle can be sev-eral hundred times its thickness. Granules are generally pow-ders larger than 75 µm (microns) (i.e., 200 mesh).

Aluminum Powder Production Plant. Facilities or buildingsin which the primary product is aluminum powder. Facilitiesor buildings in which aluminum powder or combustible alu-minum dust is produced incidental to operations shall not beconsidered a powder production plant.

Approved.* Acceptable to the authority having jurisdic-tion.

Authority Having Jurisdiction.* The organization, office, orindividual responsible for approving equipment, an installa-tion, or a procedure.

Combustible Aluminum Dust.* Any finely divided alumi-num material 420 µm (microns) or smaller in diameter (i.e.,material passing a U.S. No. 40 Standard Sieve) that presents afire or explosion hazard when dispersed and ignited in air.

Labeled. Equipment or materials to which has beenattached a label, symbol, or other identifying mark of an orga-nization that is acceptable to the authority having jurisdictionand concerned with product evaluation, that maintains peri-odic inspection of production of labeled equipment or mate-rials, and by whose labeling the manufacturer indicatescompliance with appropriate standards or performance in aspecified manner.

1998 Edition

ALUMINUM POWDER PRODUCTION PLANTS 651–5

Listed.* Equipment, materials, or services included in a listpublished by an organization that is acceptable to the author-ity having jurisdiction and concerned with evaluation of prod-ucts or services, that maintains periodic inspection ofproduction of listed equipment or materials or periodic eval-uation of services, and whose listing states that either theequipment, material, or service meets identified standards orhas been tested and found suitable for a specified purpose.

Shall. Indicates a mandatory requirement.

Should. Indicates a recommendation or that which isadvised but not required.

Standard. A document, the main text of which containsonly mandatory provisions using the word “shall” to indicaterequirements and which is in a form generally suitable formandatory reference by another standard or code or for adop-tion into law. Nonmandatory provisions shall be located in anappendix, footnote, or fine-print note and are not to be con-sidered a part of the requirements of a standard.

Chapter 2 Aluminum Powder Production Plants

2-1 Location.

2-1.1 Aluminum powder production plants shall be locatedon a site large enough so that the buildings in which powderis manufactured are at least 300 ft (90.9 m) from public roadsand from any occupied structure, such as public buildings,dwellings, business or manufacturing establishments, otherthan those buildings that are a part of the aluminum powderproduction plant.

2-1.2 A hazard analysis shall be conducted to determine theminimum separation distance for individual buildings andoperations within aluminum powder production plants.

2-2 Building Construction.

2-2.1 All buildings used for the manufacture, packing, orloading for shipment of aluminum powders shall be con-structed of noncombustible materials throughout and shallhave nonload-bearing walls. The buildings shall be designedso that all internal surfaces are readily accessible to facilitatecleaning.

2-2.2 All walls of areas where fugitive dust can be producedshall have a smooth finish and be sealed so as to leave no inte-rior or exterior voids where aluminum powder can infiltrateand accumulate. The annulus of all pipe, conduit, and ventila-tion penetrations shall be sealed.

2-2.3 Floors shall be hard-surfaced and installed with a mini-mum number of joints in which aluminum powder or dust cancollect. The requirements of this section shall also apply to ele-vated platforms, balconies, floors, or gratings. (See Appendix B.)

2-2.4 Roofs of buildings that house combustible aluminumdust–producing operations shall be supported on girders orstructural members designed to minimize surfaces on whichdust can collect. Where such surfaces are unavoidably present,they shall be covered by a smooth concrete, plaster, or non-combustible mastic fillet having a minimum slope of 55degrees to the horizontal.

2-2.5 Roof decks and basements shall be watertight.

2-2.6* Explosion venting shall be provided for buildingswhere aluminum powder is processed.

Exception: Deflagration venting shall not be required for areas wherealuminum powder is only stored or moved in covered or sealed contain-ers.

2-2.7 Doors and Windows.

2-2.7.1 All doors in interior fire-rated partitions shall be listed,self-closing fire doors, installed in accordance with NFPA 80,Standard for Fire Doors and Fire Windows.

2-2.7.2 Emergency exits shall be provided in compliance withNFPA 101®, Life Safety Code®. (See Section 5-11 and Chapter 28 ofNFPA 101.)

2-2.8 Enclosed Passageways.

2-2.8.1* Where buildings or process areas are interconnectedby enclosed passageways, the passageways shall be designed toprevent propagation of an explosion or fire from one unit toanother.

2-2.8.2 All enclosed passageways that can be occupied andthat connect with one or more processing areas shall be pro-vided with means of egress in accordance with NFPA 101, LifeSafety Code.

2-2.9 Grounding and Lightning Protection.

2-2.9.1* All process equipment and all building steel shall bebonded and grounded in accordance with NFPA 70, NationalElectrical Code®.

2-2.9.2 All buildings shall be provided with a lightning protec-tion system in accordance with NFPA 780, Standard for theInstallation of Lightning Protection Systems.

Exception: Lightning protection systems shall not be required for officebuildings and buildings that are used for storage and handling ofclosed containers.

2-2.10 Electrical Power and Control.

2-2.10.1 All electrical equipment and wiring shall be installedin accordance with NFPA 70, National Electrical Code.

2-2.10.1.1* Powder-manufacturing areas shall be classified,where applicable, in accordance with Article 500 of NFPA 70.

Exception No. 1: Offices and similar areas within the aluminumpowder–manufacturing building that are segregated and reasonablyfree from dust shall not be classified.

Exception No. 2: Control equipment meeting the requirements ofNFPA 496, Standard for Purged and Pressurized Enclosures for Elec-trical Equipment, shall be permitted.

2-2.10.2 One or more remotely located control stations shallbe provided to allow the safe and selective shutdown of pro-cess equipment in an emergency.

2-2.10.3 All manufacturing buildings shall be provided withemergency lighting systems in accordance with Section 5-9 ofNFPA 101, Life Safety Code.

2-2.10.4 Preventative maintenance for electrical equipmentshall be established commensurate with environment andconditions. Electrical equipment shall be inspected andcleaned at least once each year or more frequently if condi-tions warrant it.

2-2.10.5 Flashlights and other portable electrical equipmentshall be listed for the locations where they are used.

1998 Edition

651–6 MACHINING AND FINISHING OF ALUMINUM AND THE PRODUCTION AND HANDLING OF ALUMINUM POWDERS

2-2.11 Heating and Cooling of Aluminum Powder Production Buildings.

2-2.11.1 Buildings shall be permitted to be heated by indirecthot air heating systems or by bare pipe heating systems usingsteam or hot water as the heat transfer medium, or by listedelectric heaters. Indirect hot air shall be permitted if the heat-ing unit is located in a combustible aluminum dust–free area,adjacent to the room or area where heated air is required.

2-2.11.2 Fans or blowers used to convey the heated or cooledair shall also be located in a combustible aluminum dust–freelocation. The air supply shall be taken from outside or from alocation that is free of combustible aluminum dust.

2-2.11.3 Make-up air for building heating or cooling shallhave a dew point low enough to ensure that no free moisturecan condense at any point where the air is in contact with com-bustible aluminum dust or powder.

2-2.11.4 The requirements of 2-2.11.1, 2-2.11.2, and 2-2.11.3shall not apply to areas where aluminum metal is melted.

2-3 Machinery and Operations.

2-3.1 General Precautions.

2-3.1.1 This section shall be applied to new and existing facil-ities where aluminum powder is produced or handled.

2-3.1.2 In aluminum powder handling or manufacturingbuildings and in the operation of powder conveying systems,precautions shall be taken to avoid the production of sparksfrom static electricity, electrical faults, or impact (e.g., iron orsteel articles on stones, on each other, or on concrete), orother energy sources.

2-3.1.3 Water leakage inside or into any building where thewater can contact aluminum powder shall be prevented toavoid possible spontaneous heating.

2-3.1.4* Frictional heating shall be minimized by the use oflubrication, inspection programs, and maintenance programsand techniques set forth by the equipment manufacturer’srecommendation.

2-3.2 Requirements for Machinery.

2-3.2.1 All combustible aluminum dust–producing machinesand conveyors shall be designed, constructed, and operated sothat fugitive dust is minimized.

2-3.2.2 All machinery and equipment shall be installed inaccordance with NFPA 70, National Electrical Code.

2-3.2.3* All machinery shall be bonded and grounded to min-imize accumulation of static electric charge.

2-3.2.4 Bearings.

2-3.2.4.1* Ball or roller bearings shall be sealed against dust.

2-3.2.4.2 Where exposed bearings are used, the bearings shallbe protected to prevent ingress of combustible aluminum dustand shall have a lubrication program.

2-3.2.5 Clearances between moving surfaces that are exposedto paste, powder, or dust shall be maintained to prevent rub-bing or jamming.

2-3.2.6 Permanent magnetic separators, pneumatic separa-tors, or screens shall be installed ahead of mills, stamps, or pul-verizers wherever there is any possibility that tramp metal or

other foreign objects can be introduced into the manufactur-ing operation.

2-3.3 Start-Up Operations. All areas of processing machinerythat will be in contact with aluminum powder shall be free offoreign material and water before being placed into opera-tion.

2-4 Handling and Conveying of Aluminum Powder.

2-4.1 Where aluminum powder is present, good housekeep-ing practices shall be maintained.

2-4.2 Aluminum powder shall be handled so as to avoid spill-age and the creation of airborne dust.

2-4.3 Scoops, shovels, and scrapers used in the handling ofaluminum powder shall be electrically conductive and shall begrounded when necessary. Hand tools shall be made of spark-resistant materials.

2-4.4 Each container for aluminum powders shall be conduc-tive and covered while in storage or transit.

2-4.5 When charging aluminum powders to (or dischargingfrom) machines, the containers shall be bonded to thegrounded machine.

2-4.6 When transferring aluminum powder between contain-ers, the containers shall be bonded and at least one of the con-tainers shall be grounded.

2-4.7 Portable Containers.

2-4.7.1 Transport of aluminum powders shall be done in cov-ered conductive containers as described in 2-4.4.

2-4.7.2 Powered industrial trucks shall be selected in accor-dance with NFPA 505, Fire Safety Standard for Powered IndustrialTrucks Including Type Designations, Areas of Use, Conversions,Maintenance, and Operation.

2-4.8 Ductwork for Pneumatic Conveying Systems.

2-4.8.1 Conveyor ducts shall be fabricated of nonferrousspark-resistant metal or spark-resistant stainless steel. Plasticsor other nonconductive ducts or duct liners shall not be used.

2-4.8.2* Ducts shall be electrically bonded and grounded tominimize accumulation of static electric charge.

2-4.8.3* Where the conveying duct is exposed to weather ormoisture, it shall be moisture-tight.

2-4.8.4 A minimum conveying velocity of 4500 ft/min (1364m/min) shall be maintained throughout the conveying systemto prevent the accumulation of dust at any point and to pickup any dust or powder that can drop out during unscheduledsystem stoppages.

2-4.8.5* If the conveying gas is air, the aluminum-to-air ratiothroughout the conveying system shall be held below the min-imum explosible concentration (MEC) of the combustiblealuminum dust at normal operating conditions.

2-4.8.6* Deflagration venting (e.g., rupture diaphragms)shall be provided on ductwork. Deflagration vents shall relieveto a safe location outside of the building.

Exception: Ductwork provided with explosion isolation systems identi-fied in NFPA 69, Standard on Explosion Prevention Systems, that canprevent propagation of a deflagration into other parts of the process.

1998 Edition

ALUMINUM POWDER PRODUCTION PLANTS 651–7

2-4.8.7 Whenever damage to other property or injury to per-sonnel can result from the rupture of the ductwork, or wheredeflagration relief vents cannot provide sufficient pressurerelief, the ductwork shall be designed to withstand a suddenlyapplied pressure of at least 100 psig (690 kPa gauge).

Exception: If a portion of the ductwork is so located that no damage toproperty or injury to personnel will result from its bursting, that por-tion shall be permitted to be of lightweight construction so as to inten-tionally fail, thereby acting as an auxiliary explosion vent for thesystem.

2-4.9 Conveying Using an Inert Medium.

2-4.9.1* Inert gas–conveying systems shall be permitted, ifdesigned in accordance with Chapter 2 of NFPA 69, Standardon Explosion Prevention Systems.

2-4.9.2* The inert gas used shall be based on such gases asargon, carbon dioxide, helium, nitrogen, or flue gas and shallhave a limiting oxygen concentration determined by test to beappropriate to the inert gas.

Exception:* Where the aluminum powder is never exposed to air, theoxygen content can be zero.

2-4.9.3 The inert gas shall have a dew point such that no freemoisture can condense or accumulate at any point in the sys-tem.

2-4.9.4 The inert gas stream shall be continuously monitoredfor oxygen content and shall be arranged to sound an alarm ifthe oxygen content is not within the prescribed range.

2-4.9.5 A minimum conveying velocity of 4500 ft/min (1364m/min) shall be maintained throughout the conveying systemto prevent the accumulation of dust at any point and to pickup any dust or powder that can drop out during an unsched-uled system stoppage.

2-4.9.6 If the conveying gas is inducted into the system in a rel-atively warm environment and the ducts and collectors are rel-atively cold, the ducts and collectors shall be either insulatedor provided with heating so that the gas temperature does notfall below the dew point, causing condensation.

2-4.10 Fan and Blower Construction and Arrangement.

2-4.10.1* Blades and housings of fans used to move air orinert gas in conveying ducts shall be constructed of conduc-tive, nonsparking metal such as bronze, nonmagnetic stainlesssteel, or aluminum.

2-4.10.2 The design of the fan or blower shall not allow thetransported aluminum powder to pass through the fan beforeentering the final collector.

Exception: Where the aluminum powder–conveying system is inerted,the aluminum powder shall be permitted to pass through the fan.

2-4.10.3 Personnel shall not be permitted within 50 ft (15 m)of the fan or blower while it is operating. No maintenanceshall be performed on the fan until it is shut down.

Exception No. 1: If personnel approach the fan or blower while it isoperating, such as for a pressure test, the test shall be done under thedirect supervision of competent technical personnel and with theknowledge and approval of operating management and with the flowof aluminum powder cut off.Exception No. 2: Where the aluminum powder–conveying system isinerted, personnel shall be permitted to be closer than 50 ft (15 m).

2-4.10.4* Fans or blowers shall be located outside of all man-ufacturing buildings and shall be located so that entrance ofdust into the building from the fan exhaust shall be mini-mized.

2-4.10.5* Fans or blowers shall be equipped with ball or rollerbearings. Bearings shall be equipped with temperature-indi-cating devices and shall be arranged to sound an alarm in caseof overheating.

2-4.10.6 Fans or blowers shall be electrically interlocked withpowder-producing machinery so that the machines are shutdown if the fan stops.

2-5 Powder Collection.

2-5.1* Collectors.

2-5.1.1 Dry-type collectors shall be located outside in a safelocation and shall be provided with barriers or other meansfor protection of personnel.

2-5.1.2* The area around the collector shall be posted with asign as follows:

CAUTION

This dust collector can contain explosible dust. Keepoutside the marked area while equipment is operating.

2-5.1.3 Collectors shall be constructed of metal to allow dissi-pation of static electricity.

2-5.1.4 Ductwork shall comply with the provisions of 2-4.8.

2-5.1.5* The entire collection system, including the collector,shall be completely bonded and grounded to minimize accu-mulation of static electric charge.

2-5.1.6 Recycling of air from powder collectors into buildingsshall be prohibited.

2-5.1.7* Where an explosion hazard exists, dry dust collectorsshall be provided with deflagration vents. Extreme care shallbe taken in the selection of the type and location of vents orweak sections of the collector to minimize injury to personneland blast damage to nearby equipment or structures. Defla-gration vents shall be positioned so that a potential blast shallnot be directed towards any combustible or frangible struc-ture.

2-5.1.8 Where repairs on dry dust collectors are necessary, thecollectors shall be emptied and residual accumulations of dustthoroughly removed. (See Section 5-2.) Ductwork leading intothe collector shall be disconnected and blanked off beforerepair work shall be permitted to be started.

2-5.2 High Temperature Warning.

2-5.2.1 Cyclone or other dry-type collectors shall be equippedwith instruments for recording the surface temperature. Anoverheating alarm or warning device shall be included, andthe limit setting shall be below the maximum service tempera-ture of the filter medium or 90°F (32°C) below the ignitiontemperature of the powder cloud, whichever is lower.

2-5.2.2 All such instruments shall give audible and visualalarms at normally attended locations.

2-5.3* Collector Filter Medium. Collector filter medium madefrom synthetic fabrics that accumulate static electric chargesshall not be used.

1998 Edition

651–8 MACHINING AND FINISHING OF ALUMINUM AND THE PRODUCTION AND HANDLING OF ALUMINUM POWDERS

2-6 Storage of Aluminum Powder. When aluminum powderis stored in sealed containers, the following procedures shallapply.

(a) Containers from which a portion of powder has beenremoved shall be carefully covered and resealed.

(b) Containers shall be kept free of contact with water ormoisture.

(c) Aluminum powder packed in sealed containers shallbe permitted to be stored in commercial or public warehousesif they are of fire-resistive, noncombustible, or limited-com-bustible construction as defined in NFPA 220, Standard onTypes of Building Construction, or other construction types pro-tected with an automatic sprinkler system.

(d)* Aluminum powder shall be segregated from incom-patible materials and combustible materials.

(e) When storing aluminum powder in sealed containers,storage shall be limited to one drum tiers per pallet with aheight of no more than four pallet loads. Stacked storage shallbe arranged to ensure stability. Aisles shall be provided formaneuverability of material handling equipment, for readyaccessibility, and to facilitate incipient fire-fighting operations.

(f) Leakage or condensation from roof, floor, walls,drains, steam, water lines, or radiators shall be avoided.

(g) Smoking and open flames shall be prohibited in areaswhere aluminum powder is stored.

Chapter 3 Aluminum Powder Handling and Use

3-1 Scope. The provisions of this chapter shall apply to oper-ations including, but not limited to, the use of aluminum pow-der in the production of paste, flake powders, powderedmetallurgy component manufacturing, fireworks, and pyro-technics, propellants, plasma spray coating, chemical process-ing, and refractories.

3-2 Storage. Dry aluminum powder and aluminum pasteshall be stored in accordance with the provisions of Section2-6.

3-3* Handling. The requirements of this chapter shall applyto both regular and “nondusting” grades of aluminum pow-der, as well as aluminum paste.

3-3.1 Where aluminum powder or paste is used or handled,good housekeeping practices shall be maintained.

3-3.2 Aluminum powder and paste shall be handled so as toavoid spillage and the creation of airborne dust.

3-3.3 Scoops, shovels, and scrapers used in the handling ofaluminum powder and paste shall be electrically conductiveand shall be grounded when necessary. Hand tools shall bemade of spark-resistant materials.

3-3.4 Powered industrial trucks shall be selected in accor-dance with NFPA 505, Fire Safety Standard for Powered IndustrialTrucks Including Type Designations, Areas of Use, Conversions,Maintenance, and Operation.

3-4 Machinery and Operations.

3-4.1* Wet Milling of Aluminum Powder.

3-4.1.1 This section shall not apply to machining and rollingoperations.

3-4.1.2* Where aluminum is added to a mill in the presenceof a liquid that is chemically inert with respect to the metal,the milling shall be done in air in a vented mill or in an inert-ing atmosphere containing sufficient oxygen to oxidize anynewly exposed surfaces as they are formed.

3-4.1.3* Where aluminum is slurried in tanks or processed inblenders or other similar equipment in the presence of a liq-uid that is chemically inert with respect to the metal, the oper-ation shall be carried out in air or in an inerting atmospherecontaining sufficient oxygen to oxidize any newly exposed sur-faces as they are formed.

3-4.1.4 The dew point of the atmospheres in 3-4.1.2 and3-4.1.3 shall be maintained below the point where con-densation occurs.

3-4.1.5 Bearings of wet mills shall be grounded across thelubricating film by use of current collector brushes, a conduc-tive lubricant, or other applicable means.

3-4.1.6* Ventilation in accordance with NFPA 30, Flammableand Combustible Liquids Code, shall be maintained in areaswhere flammable or combustible solvents are handled, partic-ularly in areas where combustible aluminum dusts or powdersare present.

3-4.1.7 Solvent or slurry pumps shall be installed with controlsthat ensure that a flow exists and that ensure the pumps runwith safe operating temperatures.

3-4.2 Electrical Equipment.

3-4.2.1 All electrical wiring and equipment shall conform tothe provisions of NFPA 70, National Electrical Code.

3-4.2.2* All components of collector systems shall be electri-cally bonded and grounded in an acceptable manner. Whencontinuous contact is interrupted, metallic jumpers shall beinstalled for effective bonding.

3-4.2.3* Wet solvent milling areas shall be classified whereapplicable, in accordance with Article 500 of NFPA 70.

Exception No. 1: Offices and similar areas so occupied and segregat-ed as to be reasonably free from solvent vapors.

Exception No. 2: Control equipment meeting the requirements ofNFPA 496, Standard for Purged and Pressurized Enclosures for Elec-trical Equipment.

3-4.3 Plasma Spray Operations.

3-4.3.1 For plasma spray operations, media collectors, if used,shall be located at a distance from the point of collection toeliminate the possibility of hot metal particles igniting the fil-ter medium in the collector.

3-4.3.2 Metal overspray temperatures at the dust collectorshall be compatible with the limiting temperature of the filtermedium element.

3-5* Transfer Operations. Operations involving the transferof combustible aluminum dusts or powders from one con-tainer to another shall be designed and operated to protectpersonnel, equipment, or buildings from the fire or dustexplosion hazard produced by airborne suspensions of com-bustible aluminum dusts or powders.

3-6 Prevention of Fugitive Dust Accumulations. See Chapter 5.

1998 Edition

PROCESSING AND FINISHING OPERATIONS 651–9

Chapter 4 Processing and Finishing Operations

4-1* Scope. This chapter shall apply to operations where alu-minum or aluminum alloys are subjected to processing or fin-ishing operations. Such operations include, but are notlimited to, grinding, buffing, polishing, sawing, and machin-ing of solids.

4-2 Dust-Producing Operations.

4-2.1* Machines that produce fine particles of aluminumshall be provided with hoods, capture devices, or enclosuresthat are connected to a dust collection system having suctionand capture velocity to collect and transport all the dust pro-duced. Hoods and enclosures shall be designed and main-tained so that the fine particles will either fall or be projectedinto the hoods and enclosures in the direction of airflow. Dustshall be collected by means of suitable hoods or enclosures ateach operation.

4-2.2* Special attention shall be given to the location of alldust-producing machines with respect to the location of thedust collection system to ensure that the connecting ducts willbe as straight and as short as possible.

4-2.3 Grinding operations shall not be served by the samedust collection system as buffing and polishing operations.

4-2.4* Dry-type dust collectors shall be located outside ofbuildings.

Exception:* Individual machines with portable dust collection capa-bility shall be permitted to be used indoors when the object being pro-cessed or finished is incapable of being moved to a properly arrangedfixed hood or enclosure.

The following safeguards shall be incorporated:

(a) The operation of portable dust collection devices shall be sub-ject to a process hazard analysis to ensure that the risk to personnel andoperations from flash fire and shrapnel shall be minimized.

(b) Personnel protective clothing shall comply with Section 7-2.(c) The collector shall be designed to dissipate static electricity.(d) Collector retention capacity shall be limited to 1 lb (0.45 kg).

4-2.4.1* Dry-type collectors shall be provided with barriers orother means for protection of personnel.

4-2.4.2* The area around the collector shall be posted with asign as follows:

CAUTION

This dust collector can contain explosible dust.

4-2.5* Dust collection systems shall be dedicated to collectionof aluminum or aluminum alloy dust only. Grinders, buffers,and associated equipment with dust collectors utilized for pro-cessing aluminum shall be provided with a placard as follows:

WARNING

Aluminum Metal Only — Fire or Explosion Can Resultwith Other Metals.

Exception: If the combustible aluminum dust collection system is to beused for other materials, the system shall be disassembled and thor-oughly cleaned of all incompatible materials prior to and after its use.

4-3 Dust Collection Ducts and Ductwork.

4-3.1 All dust collection systems shall be installed in accor-dance with NFPA 91, Standard for Exhaust Systems for Air Convey-ing of Materials.

4-3.2 Ducts shall be designed to maintain a velocity of not lessthan 4500 ft/min (1364 m/min) to ensure the transport ofboth coarse and fine particles and to ensure re-entrainment if,for any reason, the particles can fall out before delivery to thecollector (e.g., in the event of a power failure).

4-3.3* Ducts shall be designed to handle a volumetric flowrate that maintains dust loading safely below the minimumexplosible concentration (MEC).

4-3.4* Ducts shall be as short as possible and shall have as fewbends and irregularities as possible to prevent interferencewith free airflow.

4-3.5 Duct Construction.

4-3.5.1 Ducts shall be constructed of conductive material andshall be carefully fabricated and assembled with smooth inte-rior surfaces and with internal lap joints facing the directionof airflow.

4-3.5.2 There shall be no unused capped outlets, pockets, orother dead-end spaces that might allow accumulations of dust.

4-3.5.3 Duct seams shall be oriented in a direction away frompersonnel.

4-3.5.4 Additional branch ducts shall not be added to an exist-ing system without redesign of the system. Branch ducts shallnot be disconnected nor unused portions of the system beblanked off without providing means to maintain required air-flow.

4-3.6* Duct systems, dust collectors, and dust-producingmachinery shall be bonded and grounded to minimize accu-mulation of static electric charge.

4-4 Wet-Type Dust Collectors.

4-4.1* The exhaust vent shall terminate outside the buildingand be securely fastened. The duct shall be as short andstraight as possible and shall be designed to withstand thesame explosion pressure as the wet-type dust collector.

Exception: The cleaned air shall be permitted to be returned to the workarea where tests conducted by an approved testing organization provethe collector’s efficiency is great enough to provide both personnel andproperty safety in the particular installation, with regard to particulatematter in the cleaned air and accumulations of particulate matter andhydrogen in the work area. (See 5-2.1.)

4-4.2* The exhaust vent shall be inspected and cleaned fre-quently to prevent buildup of highly combustible deposits ofmetal dusts on the interior surfaces of the duct.

4-4.3 The dust collector shall be arranged so that contactbetween dust particles and parts moving at high speed is pre-vented. The blower for drawing the dust-laden air into the col-lector shall be located on the clean air side of the collector.

4-4.4* The dust collector shall be arranged so that the dust-laden air stream shall be thoroughly scrubbed by the liquidto achieve the desired efficiency. [See Figures A-4-4.4(a)through A-4-4.4(c).] The use of additional dry filter mediumeither downstream or combined with a wet collector shall notbe permitted.

1998 Edition

651–10 MACHINING AND FINISHING OF ALUMINUM AND THE PRODUCTION AND HANDLING OF ALUMINUM POWDERS

4-4.5* Sludge shall be removed from the collector on a regu-lar schedule to ensure proper and safe operation of the equip-ment. Sludge shall be disposed of in accordance with therequirements of Section 4-4.8.

4-4.6 Collector Sump Venting.

4-4.6.1* The sump of water wet-type dust collectors shall beventilated at all times.

4-4.6.2 Vents shall remain open and unobstructed when themachine is shut down.

4-4.6.3 When the dust collector is not in operation, ventila-tion shall be permitted to be provided by an independentblower or by an unimpeded vent.

4-4.7 The power supply to the dust-producing equipmentshall be interlocked with the airflow from the exhaust blowerand the liquid level controller of the separator so thatimproper functioning of the dust collection system will shutdown the equipment it serves. A time delay switch or equiva-lent device shall be provided on the dust-producing equip-ment to prevent starting of its motor drive until the separatoris in complete operation.

4-4.8 Disposal of Sludge from Water Wet-Type Dust Collec-tors.

4-4.8.1 Sludge from water wet-type dust collectors shall beremoved at least once each day or more frequently if condi-tions warrant.

4-4.8.2 Covered, vented metal containers, preferably holdingnot more than 50 lb (23 kg) each, shall be used to transportthe collected sludge for disposal.

4-4.8.3 Sludge shall be permitted to be mixed with inert mate-rials in a ratio of at least 5 parts inert material to 1 part sludgeand then shall be recycled or discarded in accordance withlocal, state, and federal requirements.

4-4.8.4 Smoking or open flames shall be prohibited in the dis-posal area and throughout the disposal process.

4-5 Dry-Type Dust Collectors.

4-5.1 Electrostatic collectors shall not be used.

4-5.2* Dust-collecting filter medium shall be designed to beconductive so as to dissipate static electric charges.

4-5.3 Dry dust collection systems shall be designed and main-tained so that internal cleanliness is ensured. The accumula-tion of material inside any area of the collector other than inthe discharge containers designed for that purpose shall notbe permitted.

4-5.4 Accumulation or condensation of water at any point inthe dry dust collection system shall be prevented.

4-5.5 Dust shall be removed from dry collectors at least onceeach day and at more frequent intervals if conditions warrant.Extreme care shall be taken in removing dust from the collec-tors to avoid creating dust clouds. The material shall be dis-charged into metal containers that shall be promptly andtightly covered to avoid the creation of airborne fugitive dust.Waste material shall be mixed with an inert material in a vol-ume ratio of 5 parts inert material to 1 part metal dust andshall be recycled or disposed of in accordance with local, state,and federal regulations.

4-5.6* Dry collectors used for combustible aluminum dustshall be provided with deflagration vents. The selection of thetype and location of vents or weak sections of the collectorshall be designed to minimize injury to personnel and to min-imize blast and fire damage to nearby equipment or struc-tures.

4-5.7 Where repairs on dry dust collectors are necessary, thecollectors shall be emptied and residual accumulations of dustthoroughly removed. (See Section 5-2.) Ductwork leading intothe collector shall be disconnected and blanked off beforerepair work shall be permitted to be started.

4-5.8 The interior of hoods and ducts shall be regularlycleaned wherever there is the possibility of buildup of wax,lint, aluminum fines, or other combustible material.

4-5.9 The dust collector shall be arranged so that contactbetween dust particles and parts moving at high speeds shallbe prevented. The blower for drawing the dust-laden air intothe collector shall be located on the clean air side of the col-lector.

4-6 Recycling of Exhaust Air. Recycling of air from dry dustcollectors into buildings shall be prohibited.

4-7 Machining and Sawing Operations.

4-7.1* Cutting tools shall be of proper design and shall bekept sharp for satisfactory work with aluminum.

4-7.2* Sawing, grinding, and cutting equipment shall begrounded.

4-7.3 All aluminum chips, oily crushed lathe turnings, rawturnings, and swarf shall be collected in closed-top containersand removed daily, at a minimum, to a safe storage or disposalarea.

4-7.4 Nonflammable coolants shall be used for wet grinding,cutting, or sawing operations. The coolant shall be filtered ona continuous basis, and the collected solids shall not be per-mitted to accumulate in quantities greater than 5 gal (19 L)and shall be removed to a safe storage or disposal area.

4-8 Electrical Equipment.

4-8.1 All electrical wiring and equipment shall conform to theprovisions of NFPA 70, National Electrical Code.

4-8.2* All components of the dust collection systems shall beelectrically bonded and grounded in an acceptable manner.When continuous contact is interrupted, metallic jumpersshall be installed for effective bonding.

Chapter 5 Housekeeping

5-1 Scope. This chapter shall apply to new and existing facil-ities where combustible aluminum dusts, pastes, and powdersare present.

5-2 Cleanup Procedures for Fugitive Dust Accumulations.

5-2.1* Fugitive dust shall not be permitted to accumulate.

5-2.2 Periodic cleanup of fugitive dusts shall be accomplishedby using conductive, nonsparking scoops and soft brooms,brushes that have natural fiber bristles, or vacuum-cleaningsystems designed for handling combustible metal powders inaccordance with Section 5-3.

5-2.3 Cleanup of Spilled Aluminum Powder.

1998 Edition

FIRE PREVENTION, PROTECTION, AND PROCEDURES 651–11

5-2.3.1 Preliminary cleanup of the bulk of the powder shall beaccomplished by using conductive, nonsparking scoops andsoft brooms, as well as brushes that have natural fiber bristles.

5-2.3.2 Vacuum cleaners shall be permitted to be used onlyfor small amounts of residual material remaining after prelim-inary cleanup.

5-3* Vacuum-Cleaning Systems.

5-3.1 Vacuum-cleaning systems shall only be used for removalof dust accumulations too small, too dispersed, or inaccessibleto be thoroughly removed by hand brushing.

5-3.2* Vacuum-cleaning systems shall be effectively bondedand grounded to minimize accumulation of static electriccharge.

5-3.3 Due to the inherent hazards associated with the use offixed and portable vacuum-cleaning systems for finely dividedcombustible aluminum dust, special engineering consider-ations shall be given to the design, installation, maintenance,and use of such systems.

5-3.4* Portable vacuum cleaners shall only be used if listed orapproved for use with combustible aluminum dust.

5-3.5 Vacuum cleaner hose shall be conductive, and nozzlesor fittings shall be made of conductive, nonsparking material.Assembled components shall be conductive and bondedwhere necessary. Periodic tests for continuity shall be per-formed.

5-3.6 Combustible aluminum dust picked up by a fixed vac-uum-cleaning system shall be discharged into a container orcollector located outside the building.

5-4 Compressed Air Cleaning Requirements. Compressed airblowdown shall not be permitted.

Exception: In certain areas, impossible to clean otherwise, compressedair blowdown shall be done under carefully controlled conditions withall potential ignition sources prohibited in or near the area and withall equipment shut down.

5-5 Water Cleaning Requirements. The use of water forcleaning shall not be allowed in manufacturing areas unlessthe following requirements are met:(a) Competent technical personnel have determined that

the use of water will be the safest method of cleaning inthe shortest exposure time.

(b) Operating management has full knowledge of and hasgranted approval of its use.

(c) Ventilation, either natural or forced, is available to main-tain the hydrogen concentration safely below the lowerflammable limit (LFL).

(d) Complete drainage of all water and powder to a safe,remote area is available.

5-6 Cleaning Frequency.

5-6.1 The accumulation of excessive dust on any portions ofbuildings or machinery not regularly cleaned in daily opera-tions shall be minimized.

5-6.2 Regular periodic cleaning of buildings and machinery,with all machinery idle and power off, shall be carried out asfrequently as conditions warrant.

Chapter 6 Fire Prevention, Protection,and Procedures

6-1* Scope. This section shall apply to new and existing facil-ities where combustible aluminum dusts, pastes, and powdersare present.

6-2 Extinguishing Agents and Application Techniques for Use on Combustible Aluminum Dusts.

6-2.1* An incipient fire shall be ringed with a dam of dry sand,dry inert granular material, or a listed Class D extinguishingpowder in accordance with the manufacturer’s instructions.Application of dry extinguishing agent shall be conducted insuch a manner so as to avoid any disturbance of the combusti-ble aluminum dust, which could cause a dust cloud.

6-2.2 The dry extinguishing agent shall be stored in such amanner that it remains clean and dry.

6-2.3* The dry extinguishing agent shall be carefully appliedwith a nonsparking metal scoop or shovel or applied from alisted Class D fire extinguisher equipped with a low-velocitynozzle.

6-2.4 Drafts shall be eliminated by shutting off fans andmachinery and by closing doors and windows.

6-2.5 Portable or wheeled fire extinguishers shall be providedin accordance with NFPA 10, Standard for Portable Fire Extin-guishers. Areas where dry combustible aluminum dust ispresent shall not have fire extinguishers rated for Class A, B,or C fires.

Exception: Where Class A, B, or C fire hazards are in the combustiblealuminum powder area, extinguishers suitable for use on such firesshall be permitted, provided they are marked “Not for Use on Alumi-num Powder Fires.”

6-2.6* Extinguishers listed for use on Class B fires shall be pro-vided in areas where solvent cleaning and washing is per-formed. Conspicuous signs shall be placed adjacent to suchextinguishers stating that these extinguishers shall not be usedfor combustible aluminum dust fires.

Exception: Halogenated extinguishing agents shall not be used.

6-3* Solvent-Wetted Powders.

6-3.1 An incipient fire occurring while the aluminum powderis in slurry form shall be permitted to be fought using listedClass B extinguishing agents.

Exception: Halogenated extinguishing agents shall not be used.

6-3.2* An incipient fire occurring in semi-wet material or fil-ter-cake shall be fought using a listed Class B extinguishingagent.

6-3.3* Where carbon dioxide is used to extinguish fires involv-ing solvent-wetted aluminum, the residual material shall beimmediately covered with dry sand, dry inert granular mate-rial, or with other listed Class D extinguishing agent, and theentire mass shall be allowed to cool until it reaches ambienttemperature. When the material has cooled and it has beendetermined that there are no hot spots, the covered materialshall be carefully removed for disposal. It shall be handled insmall quantities in covered containers, preferably not morethan 3 gal (11 L) each in 5-gal (19-L) containers.

1998 Edition

651–12 MACHINING AND FINISHING OF ALUMINUM AND THE PRODUCTION AND HANDLING OF ALUMINUM POWDERS

6-3.4 Manual water application shall only be used on a sol-vent–metal powder fire as a last resort, when other methods ofcontrol have failed and the fire shows evidence of going out ofcontrol. Only low-velocity spray or fog nozzles shall be used.Manual application of water shall be conducted in such a man-ner so as to avoid creating a dust cloud. Once water is used, itsuse shall be continued until the fire is extinguished or untilthe area becomes untenable.

6-3.4.1 After extinguishment, the area shall be immediatelycleaned of all wetted powder, paste, or slurry.

6-3.4.2 Ventilation shall be provided during cleanup to avoidconcentrations of hydrogen from the exothermic reaction ofthe aluminum with water.

6-3.4.3* Fire flow containment shall be provided for new facil-ities.

6-4 Automatic Sprinkler Protection.

6-4.1 Automatic sprinkler protection shall not be permittedin areas where dry aluminum powders are produced or han-dled.

Exception:* Where both dry aluminum and other combustibles (e.g.,solvents) are present, automatic sprinkler protection shall be permittedif a hazard analysis acceptable to the authority having jurisdiction in-dicates that automatic sprinkler systems could reduce the risk to lifeand damage to property. The hazard analysis shall consider the possi-bility of fires and explosions involving both dry aluminum and the oth-er combustibles.

6-4.2 The special hazards associated with aluminum powderin contact with water shall be considered in the selection,design, and installation of automatic sprinkler systems.

6-4.3 Automatic sprinkler systems shall be designed andinstalled in accordance with NFPA 13, Standard for the Installa-tion of Sprinkler Systems, and where applicable NFPA 231C, Stan-dard for Rack Storage of Materials.

6-4.4 Employee training and organizational planning shall beprovided to ensure safe evacuation of the sprinkler protectedarea in case of fire.

6-5 Fire-Fighting Organization.

6-5.1 Only trained personnel shall be permitted to engage infire control activity. All others shall be evacuated from thearea. Training shall emphasize the different types of firesanticipated and the appropriate agents and techniques to beused.

6-5.2 Fire-fighting personnel shall be given regular and con-sistent training in the extinguishment of test fires set in a safelocation away from manufacturing buildings. Training shallinclude all possible contingencies.

6-5.3* If professional or volunteer fire fighters are admittedonto the property in the event of a fire emergency, their activ-ity shall be directed by the on-site ranking officer of thetrained plant fire fighters.

6-6* Employee Training Program. Training programs shallbe instituted to properly inform employees about the hazardsinvolved in the manufacture of aluminum powder, paste, orgranules, and the hazards involved in processing or finishingoperations that generate fine combustible aluminum dust, asappropriate to the operation.

6-7 Control of Ignition Sources.

6-7.1* No smoking, open flames, electric or gas cutting orwelding equipment, or spark-producing operations shall bepermitted in the section of the building where combustiblealuminum dust is produced or handled. This type of workshall be allowed only in the areas where all machinery is shutdown, and the area is thoroughly cleaned and inspected toensure the removal of all accumulations of combustible alumi-num dust. Lockout/tagout procedures shall be followed forthe shutdown of machinery. Hotwork operations in facilitiescovered by this standard shall comply with the requirements ofNFPA 51B, Standard for Fire Prevention in Use of Cutting and Weld-ing Processes.

6-7.2 Smoking materials, matches, and lighters shall not becarried or used by employees or visitors about the premisesadjacent to or within any building in which combustible alumi-num dust is present.

6-7.3 Propellant-actuated tools shall not be used in areaswhere a dust explosion can occur unless all machinery in thearea is shut down and the area and machinery are properlycleaned.

6-7.4* Nonsparking tools shall be used when making repairsor adjustments on or around any machinery or apparatuswhere combustible aluminum dust is present.

6-7.5 Dressing of grinding wheels shall not be conductedwhen the airflow across the grinding wheel is entering a com-bustible aluminum dust collection system.

6-7.6 Spark-producing operations shall be separated from anycleaning equipment using flammable or combustible solventsand shall comply with NFPA 30, Flammable and Combustible Liq-uids Code.

6-7.7 Brooms and brushes used for cleaning shall have naturalfiber bristles. Synthetic bristles shall not be used. Scoops, dust-pans, and so forth used for collecting sweepings shall be madeof nonsparking, conductive material.

6-7.8 Dry aluminum sweepings shall not be returned to themain process stream for processing.

6-8 Compressed Air Fittings. To prevent potential explo-sions caused by inadvertently using compressed air in place ofinert gas, fittings used on compressed air and inert gasline out-lets shall not be interchangeable.

Chapter 7 Safety Procedures

7-1 Scope. This section shall apply to new and existing facili-ties where combustible aluminum dusts, pastes, and powdersare present.

7-2 Personal Protective Equipment.

7-2.1 Outer clothing shall be clean, flame retardant, and non-static–generating where combustible aluminum dust ispresent and shall be designed to be easily removable. Tightlywoven, smooth fabrics treated with a flame-retardant chemi-cal, and from which dust can readily be brushed, shall be used,if necessary. Woolen, silk, or synthetic fabrics that can accumu-late high static electric charges shall not be used.

7-2.2 Work clothing shall be designed to minimize the accu-mulations of combustible aluminum dust (e.g., trousers shallnot have cuffs).

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APPENDIX A 651–13

7-2.3* Safety shoes shall be static dissipating, where necessary,shall have no exposed metal, and shall be appropriate for thetype of operation taking place.

7-2.4* Emergency procedures for handling clothing firesshall be established. If deluge showers are installed, they shallbe located away from dry aluminum powder processing andhandling areas.

7-3* Emergency Procedures. Emergency procedures to befollowed in case of fire or explosion shall be established. Allemployees shall be trained in these procedures.

7-4 Safety Inspection. A thorough inspection of the operat-ing area shall take place on an as needed basis to help ensurethat the equipment is in good condition and that proper workpractices are being followed. This inspection shall be con-ducted at least quarterly but shall be permitted to be donemore often. The inspection shall be conducted by a person(s)knowledgeable in the proper practices, who shall record thefindings and recommendations.

7-5 Maintenance. Regular and periodic maintenance checksand calibration on equipment critical to employee safety andplant operation shall be performed.

Chapter 8 Referenced Publications

8-1 The following documents or portions thereof are refer-enced within this standard as mandatory requirements andshall be considered part of the requirements of this standard.The edition indicated for each referenced mandatory docu-ment is the current edition as of the date of the NFPA issuanceof this standard. Some of these mandatory documents mightalso be referenced in this standard for specific informationalpurposes and, therefore, are also listed in Appendix C.

8-1.1 NFPA Publications. National Fire Protection Associa-tion, 1 Batterymarch Park, P.O. Box 9101, Quincy, MA 02269-9101.

NFPA 10, Standard for Portable Fire Extinguishers, 1998 edi-tion.

NFPA 13, Standard for the Installation of Sprinkler Systems,1996 edition.

NFPA 30, Flammable and Combustible Liquids Code, 1996 edi-tion.

NFPA 51B, Standard for Fire Prevention in Use of Cutting andWelding Processes, 1994 edition.

NFPA 69, Standard on Explosion Prevention Systems, 1997 edi-tion.

NFPA 70, National Electrical Code®, 1999 edition.NFPA 80, Standard for Fire Doors and Fire Windows, 1995 edi-

tion.NFPA 91, Standard for Exhaust Systems for Air Conveying of

Materials, 1995 edition.NFPA 101®, Life Safety Code®, 1997 edition.NFPA 220, Standard on Types of Building Construction, 1995

edition.NFPA 231C, Standard for Rack Storage of Materials, 1998 edi-

tion.NFPA 496, Standard for Purged and Pressurized Enclosures for

Electrical Equipment, 1998 edition.NFPA 505, Fire Safety Standard for Powered Industrial Trucks

Including Type Designations, Areas of Use, Conversions, Mainte-nance, and Operation, 1996 edition.

NFPA 780, Standard for the Installation of Lightning ProtectionSystems, 1997 edition.

Appendix A Explanatory Material

Appendix A is not a part of the requirements of this NFPA docu-ment but is included for informational purposes only. This appendixcontains explanatory material, numbered to correspond with the appli-cable text paragraphs.

A-1-1.1 Certain “nondusting” grades of aluminum flake pow-der are being produced. Although they exhibit less tendencyto be dispersed into a dust cloud, the same precautionsdescribed in this standard should be observed.

A-1-5 Aluminum Chips. Aluminum chips vary in ease of igni-tion and rapidity of burning, depending on their size andgeometry. A light, fluffy chip can ignite easily and burn vigor-ously, whereas a heavy, compact chip ignites with difficulty andburns quite slowly.

A-1-5 Approved. The National Fire Protection Associationdoes not approve, inspect, or certify any installations, proce-dures, equipment, or materials; nor does it approve or evalu-ate testing laboratories. In determining the acceptability ofinstallations, procedures, equipment, or materials, the author-ity having jurisdiction may base acceptance on compliancewith NFPA or other appropriate standards. In the absence ofsuch standards, said authority may require evidence of properinstallation, procedure, or use. The authority having jurisdic-tion may also refer to the listings or labeling practices of anorganization that is concerned with product evaluations and isthus in a position to determine compliance with appropriatestandards for the current production of listed items.

A-1-5 Authority Having Jurisdiction. The phrase “authorityhaving jurisdiction” is used in NFPA documents in a broadmanner, since jurisdictions and approval agencies vary, as dotheir responsibilities. Where public safety is primary, theauthority having jurisdiction may be a federal, state, local, orother regional department or individual such as a fire chief;fire marshal; chief of a fire prevention bureau, labor depart-ment, or health department; building official; electricalinspector; or others having statutory authority. For insurancepurposes, an insurance inspection department, rating bureau,or other insurance company representative may be the author-ity having jurisdiction. In many circumstances, the propertyowner or his or her designated agent assumes the role of theauthority having jurisdiction; at government installations, thecommanding officer or departmental official may be theauthority having jurisdiction.

A-1-5 Combustible Aluminum Dust. Any time a combustibledust is processed or handled, a potential for explosion exists.The degree of explosion hazard will vary depending on thetype of combustible dust and processing methods used.

A dust explosion has four requirements:(a) The dust is combustible. One method of determining

combustibility of dusts is testing in accordance withASTM E 1226, Standard Test Method for Pressure and Rate ofPressure Rise for Combustible Dusts.

(b) The dust particles form a cloud at or exceeding the mini-mum explosible concentration (MEC).

(c) A source of ignition is present.

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651–14 MACHINING AND FINISHING OF ALUMINUM AND THE PRODUCTION AND HANDLING OF ALUMINUM POWDERS

(d) Oxygen is present in sufficient quantities to support com-bustion.

Evaluation of a combustible dust explosion hazard and theprevention techniques employed should be determined bymeans of actual test data. All combustible dusts that can pro-duce a dust explosion should be tested so as to determine thefollowing data:(a) Particle size distribution(b) Moisture content as received and dried(c) Minimum dust concentration to ignite(d) Minimum energy required for ignition (joules)(e) Maximum rate of pressure rise at various concentrations(f) Layer ignition temperature(g) Maximum explosion pressure at optimum concentration

The following data can be determined by optional testing:(a) Dust cloud ignition temperature(b) Maximum permissible oxygen content to prevent igni-

tion(c) Electrical resistivity measurement

Samples to be submitted for testing should not be allowedto oxidize significantly more than their degree of oxidationwould be where the hazard exists. This usually involves takingsamples as soon as possible after the aluminum dust is pro-duced, and then storing and shipping the samples in an air-tight container purged with an inert gas.

A-1-5 Listed. The means for identifying listed equipmentmay vary for each organization concerned with product evalu-ation; some organizations do not recognize equipment aslisted unless it is also labeled. The authority having jurisdictionshould utilize the system employed by the listing organizationto identify a listed product.

A-2-2.6 For information on deflagration venting, see NFPA68, Guide for Venting of Deflagrations.

A-2-2.8.1 For information on deflagration venting, see NFPA68, Guide for Venting of Deflagrations.

A-2-2.9.1 For information on static electricity, see NFPA 77,Recommended Practice on Static Electricity .

A-2-2.10.1.1 For additional information on classification ofdusty locations, see NFPA 499, Recommended Practice for the Clas-sification of Combustible Dusts and of Hazardous (Classified) Loca-tions for Electrical Installations in Chemical Process Areas.

A-2-3.1.4 Temperature-sensing elements connected to alarmsor machine stop switches should be employed for locationswhere overheating of bearings or other elements could beanticipated.

A-2-3.2.3 This requirement shall be applicable to stamp mor-tars, mills, fans, and conveyors in all areas where dust is pro-duced or handled, such as in finishing and polishingequipment, filters, driers, dust screens, fixed storage bins, anddust collection and transport systems of all types. For furtherinformation on bonding and grounding, see NFPA 77, Recom-mended Practice on Static Electricity .

A-2-3.2.4.1 Journal bearings should not be used because ofthe difficulty of maintaining proper lubrication to preventoverheating. Outboard bearings are used where practicablebecause it is easier to check for overheating. In those instanceswhere dust tends to penetrate bearings, a continuous flow of

inert gas (11/2 percent to 5 percent oxygen) can be employedto pressurize the bearings and seals.

A-2-4.8.2 For information on static electricity, see NFPA 77,Recommended Practice on Static Electricity.

A-2-4.8.3 Any moisture entering the system can react with thealuminum powder, generating heat and hydrogen. Hydrogenis extremely flammable and very easy to ignite. It should notbe trapped in nonventilated areas of buildings, equipment, orenclosures.

A-2-4.8.5 Typical margins of safety used for pneumatic dusthandling are 25 percent to 50 percent of the MEC. Publisheddata indicates an MEC of 45 g/m3 (0.045 oz/ft3) for atomizedaluminum powder. MEC data for aluminum with varying par-ticle size distributions can be found in U.S. Bureau of Mines,RI 6516, “Explosibility of Metal Powders.” Although the alumi-num powder–air suspension can be held below 25 percent to50 percent of the MEC in the conveying system, the suspen-sion will necessarily pass through the explosible range in thecollector at the end of the system unless the dust is collectedin liquid, such as in a spray tower. Also, the powder in the con-veying line from the atomizer to the collector will, of necessity,approach the MEC.

A-2-4.8.6 For information on spacing and sizing of ductworkdeflagration vents, see NFPA 68, Guide for Venting of Deflagra-tions.

A-2-4.9.1 Aluminum and aluminum alloy powders are pro-duced by various means. These processes, as well as certain fin-ishing and transporting operations, tend to expose acontinuously increasing area of new metal surface. Most met-als immediately undergo a surface reaction with availableatmospheric oxygen that forms a protective coating of metaloxide that serves as an impervious layer to inhibit further oxi-dation. This reaction is exothermic. If a fine or thin light-weight particle having a large surface area of “new” metal issuddenly exposed to the atmosphere, sufficient heat will begenerated to raise its temperature to the ignition point.

Completely inert gas generally cannot be used as an inert-ing medium since the aluminum powder would eventually, atsome point in the process, be exposed to the atmosphere, atwhich time the unreacted surfaces would be oxidized; enoughheat would be produced to initiate either a fire or an explo-sion. To provide maximum safety, a means for the controlledoxidation of newly exposed surfaces is provided by regulatingthe oxygen concentration in the inert gas. The mixture servesto control the rate of oxidation, while materially reducing thefire and explosion hazard.

A completely inert gas can be used if the powder so pro-duced will not be exposed to air.

A-2-4.9.2 Oxygen limits of 3 percent to 5 percent have beenmaintained in aluminum powder systems using a controlledflue gas. Other limits are applicable where other inert gasesare used. Refer to U.S. Bureau of Mines, RI 3722, “Inflamma-bility and Explosibility of Metal Powders.”

A-2-4.9.2 Exception. A completely inert gas can be used if thepowder so produced will not be exposed to air. Aluminumpowder produced without oxygen is more highly reactive thanaluminum powder produced by conventional means.

A-2-4.10.1 Information on spark-resistant fans and blowerscan be found in Air Movement and Control Association(AMCA) Standard No. 99-0401-91.

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A-2-4.10.4 Ultimately, all fans or blowers in dust collection sys-tems accumulate sufficient powder to become a potentialexplosion hazard.

A-2-4.10.5 Fans or blowers can also be provided with vibra-tion-indicating devices, arranged to sound an alarm or to pro-vide shutdown, or both, in the event of blade or rotorimbalance, or bearing or drive problems.

A-2-5.1 A high-efficiency cyclone-type collector presents lesshazard than a bag- or media-type collector and, except forextremely fine powders, will usually operate with fairly highcollection efficiency. Where cyclones are used, the exhaust fandischarges to atmosphere away from other operations. Itshould be recognized that there will be some instances inwhich a cyclone collector can be followed by a fabric- or bag-type, or media-type collector or by a scrubber-type collectorwhere particulate emissions are kept at a low level. The haz-ards of each type of collector should be recognized and pro-tected against. In each instance, the fan will be the lastelement downstream in the system. Because of the extremehazard involved with a bag- or media-type collector, consider-ation should be given to a multiple-series cyclone with a liquidfinal stage.

Industry experience has clearly demonstrated that an even-tual explosion can be expected where a bag- or media-type col-lector is used to collect aluminum fines. Seldom, if ever, canthe source of ignition be positively identified. In those unusualinstances when it becomes necessary to collect very small finesfor a specific commercial product, it is customary for the pro-ducer to employ a bag- or media-type collector. With theknowledge that strong explosive potential is present, the pro-ducer will locate the bag- or media-type collector a safe dis-tance from buildings and personnel.

If a bag- or media-type collector is used, the shaking systemor dust removal system can be such as to minimize sparkingdue to frictional contact or impact. Pneumatic- or pulse-typecleaning is more desirable because no mechanical movingparts are involved in the dusty atmosphere. If the bags are pro-vided with grounding wires, they can be positively groundedthrough a low-resistance path to ground. Where bags are used,it is customary that the baghouse be protected by an alarm toindicate excessive pressure drop across the bags. An excess airtemperature alarm is also frequently employed. A bag- ormedia-type collector is customarily located at least 50 ft (15 m)from any other building or operation. It is not customary topermit personnel to be within 50 ft (15 m) of the collector dur-ing operation or when shaking bags. Explosion vents are usu-ally built into the system, as described in NFPA 68, Guide forVenting of Deflagrations. Care is customarily exercised in locat-ing the vents because of the possibility of blast damage to per-sonnel or adjacent structures.

A-2-5.1.2 For the method to calculate the length of a fireballissuing from a vented collector, see NFPA 68, Guide for Ventingof Deflagrations.

A-2-5.1.5 For information on precautions for static electricity,see NFPA 77, Recommended Practice on Static Electricity.

A-2-5.1.7 Explosion venting is especially important for com-bustible aluminum dust, due to the high maximum explosionpressures reached and the extremely high rate of pressurerise. For information on design of explosion vents and predict-ing the size of the fireball, see NFPA 68, Guide for Venting ofDeflagrations. Dust collectors, when provided by a manufac-

turer, seldom have properly sized venting to handle a combus-tible aluminum dust explosion.

A-2-5.3 Some collector bags or other types of media or screenshave fine, noninsulated wire enmeshed into or woven with thecloth or otherwise fastened to it. These are always securelygrounded. It should be pointed out that this is not a positiveguarantee of static charge removal because there is nodependable force to cause the charges to move across the non-conducting area of the fabric to the grounded wires. Often, asubstantial potential difference can be measured. Also, it ispossible that a wire in the cloth could break in such a way thatit is no longer grounded. Such a wire serves as a capacitor andcould store a static charge.

A-2-6(d) Materials incompatible with aluminum powderinclude, but are not limited to, oxidizers, organic peroxides,inorganic acids, and materials identified in the Material SafetyData Sheet (MSDS).

A-3-3 Certain nondusting grades of aluminum flake powderare being produced. These tend to reduce the hazard of inad-vertently caused dust clouds. They are as combustible as regu-lar grades of flake powder, and once levitated into a cloud,exhibit the same explosibility characteristics. For these rea-sons, the same precautions must be observed as for normalgrades of powder.

A-3-4.1 When aluminum is milled in a ball, rod, or similar typeof mill, in the presence of a liquid that is chemically inert withrespect to the metal, the air–dust explosion hazard is elimi-nated. When the resulting product is subsequently exposed toair, any unoxidized surfaces produced during milling willreact and could generate enough heat to cause ignition. Toprevent this, it is imperative that a controlled amount of oxy-gen be present in the milling operation and in slurries aheadof filters and blenders, so that new surfaces are oxidized asthey are formed. The addition of a milling agent, such asstearic acid, does not eliminate the need for this added oxy-gen.

A-3-4.1.2 See A-3-4.1.

A-3-4.1.3 See A-3-4.1.

A-3-4.1.6 Of particular note in the aluminum paste–manufac-turing process are the risks associated with hybrid mixtures. Ahybrid mixture is a mixture of a dust with one or more flam-mable gases or vapors. The presence of the flammable gas orvapor, even at concentrations less than their lower flammablelimit (LFL), will not only add to the violence of the dust–aircombustion but will drastically reduce the ignition energy. Insuch cases, electrical equipment should be specified that issuitable for simultaneous exposure to both the Class I (flam-mable gas) and the Class II (combustible dust) hazards.

A-3-4.2.2 For information on bonding and grounding, seeNFPA 77, Recommended Practice on Static Electricity.

A-3-4.2.3 For additional information on classification of areascontaining solvent vapors, see NFPA 497, Recommended Practicefor the Classification of Flammable Liquids, Gases, or Vapors and ofHazardous (Classified) Locations for Electrical Installations in Chem-ical Process Areas.

A-3-5 See Figures A-3-5(a) and A-3-5(b) for examples of bagdump-station dust collection.

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651–16 MACHINING AND FINISHING OF ALUMINUM AND THE PRODUCTION AND HANDLING OF ALUMINUM POWDERS

A-4-1 There are two recognized methods of collecting alumi-num dust in industrial operations. They are wet dust collec-tors, which can be located indoors near the point of dustgeneration, or dry-type collectors located outdoors, as close aspossible to the point of dust generation.

A-4-2.1 The maximum concentration of less than 100-meshmagnesium dust should never exceed 0.03 oz/ft3 (0.03 g/m3)(air), which is the minimum explosible concentration.

Minimum explosible concentrations for magnesium dustin air are published in RI 6516, “Explosibility of Metal Pow-ders.” Although the metal dust–air suspension normally canbe held below the minimum explosible concentration in theconveying system, the suspension can pass through the flam-mable range in the collector at the end of the system.

A-4-2.2 Often, individual wet-type dust collectors can be pro-vided for each dust-producing machine so that ductwork con-necting the hood or enclosure of the machine to the collectoris as short as possible.

A-4-2.4 See Figure A-4-2.4.

A-4-2.4 Exception. See Figure A-4-2.4 Exception.

Figure A-3-5(a) Example of manual bag dump station. (Exposes op-erator to potential fire or explosion or both.)

Figure A-3-5(b) Automated bag dump operation only.

Not acceptable

Grate open to atmosphere

Material to be processed

AcceptableFigure A-4-2.4 Example of a fixed media-type dust collector.

Figure A-4-2.4 Exception. Example of a portable media-type dust collector.

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A-4-2.4.1 A high-efficiency cyclone-type collector presents lesshazard than a bag- or media-type collector and, except forextremely fine powders, will usually operate with fairly highcollection efficiency. Where cyclones are used, the exhaust fandischarges to atmosphere away from other operations. Itshould be recognized that there will be some instances inwhich a centrifugal-type collector can be followed by a fabric-or bag-type, or media-type collector or by a scrubber-type col-lector where particulate emissions are kept at a low level. Thehazards of each collector should be recognized and protectedagainst. In each instance, the fan will be the last elementdownstream in the system. Because of the extreme hazardinvolved with a bag- or media-type collector, considerationshould be given to a multiple-series cyclone with a liquid finalstage.

Industry experience has clearly demonstrated that an even-tual explosion can be expected where a bag- or media-type col-lector is used to collect aluminum fines. Seldom, if ever, canthe source of ignition be positively identified. In those unusualinstances when it becomes necessary to collect very small finesfor a specific commercial product, it is customary for the pro-ducer to employ a bag- or media-type collector. With theknowledge that strong explosive potential is present, the pro-ducer will locate the bag- or media-type collector a safe dis-tance from buildings and personnel.

If a bag- or media-type collector is used, the shaking systemor dust removal system can be such as to minimize sparkingdue to frictional contact or impact. Pneumatic- or pulse-typecleaning is more desirable because no mechanical movingparts are involved in the dusty atmosphere. If the bags are pro-vided with grounding wires, they can be positively groundedthrough a low-resistance path to ground. Where bags are used,it is customary that the baghouse be protected by an alarm toindicate excessive pressure drop across the bags. An excess airtemperature alarm is also frequently employed. A bag- ormedia-type collector is customarily located at least 50 ft (15 m)from any other building or operation. It is not customary topermit personnel to be within 50 ft (15 m) of the collector dur-ing operation or when shaking bags. Explosion vents are usu-ally built into the system, as described in NFPA 68, Guide forVenting of Deflagrations. Care is customarily exercised in locat-ing the vents because of the possibility of blast damage to per-sonnel or adjacent structures.

A-4-2.4.2 For the method to calculate the length of a fireballissuing from a vented collector, see NFPA 68, Guide for Ventingof Deflagrations.

A-4-2.5 Under certain circumstances, such as impact withrusted iron or steel, aluminum cannot safely be considered tobe nonsparking, since a minor thermite reaction can be initi-ated. For details, refer to the article by H. S. Eisner, “Alumi-num and the Gas Ignition Risk.”

A-4-3.3 The U.S. Bureau of Mines Report of Investigations6516, “Explosibility of Metal Powders,” reports the results oftests conducted on 89 different samples of aluminum powdersof various grades and sizes. Minimum ignition energies fordust clouds ranged upwards from 15 mJ, whereas minimumignition energies for dust layers ranged upwards from 15 mJ.Ignition temperatures ranged upwards from 608°F (320°C).Minimum explosive concentrations ranged upwards from0.040 oz/ft3 (40 g/m3). Maximum explosion pressures canexceed 90 psig (620 kPa gauge).

A-4-3.4 Short, straight ducts reduce the explosion hazard andminimize the likelihood of accumulations of dry dust. Also,accumulations of tallow, wax, or oil with metallic fines and lintcan be seen readily and more easily removed.

A-4-3.6 For additional information, see NFPA 77, Recom-mended Practice on Static Electricity.

A-4-4.1 Hydrogen is extremely flammable and is very easy toignite. It should not be trapped in nonventilated areas ofbuildings, equipment, or enclosures.

A-4-4.2 The humid air of the wet-type dust collector wets thefine particles that pass through the collector so that the parti-cles agglomerate and tend to build up a cake or a spongelikedeposit (“sludge”), which is highly combustible, on the innerwall of the exhaust duct.

A-4-4.4 Refer to Figures A-4-4.4(a) through A-4-4.4(c) forexamples of liquid precipitation separators.

Figure A-4-4.4(a) Typical liquid precipitation separator for fixed dust-producing equipment.

Figure A-4-4.4(b) Typical liquid precipitation separator for portable dust-producing equipment.

Dust-producingequipment

Power to dust-producing

machine motorinterrupted

by low airflow orlow liquid level

at the liquidprecipitator

Self-openingvent (optional)

Sump vent

Mist eliminatorpacks

Mist eliminatoraccess door

Liquid levelcontrol withinterlock

Inspection andcleanout door

Water level

Sludge levelin tank

Overflow anddrain piping

Mist eliminatorpacks

Mist eliminatoraccess doors

Liquid level controlwith interlock

Water level

Sludge level in tank

¹⁄₂-in. (13-mm)expanded metalaluminum mesh

Nonsparkingwork surface

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651–18 MACHINING AND FINISHING OF ALUMINUM AND THE PRODUCTION AND HANDLING OF ALUMINUM POWDERS

.

A-4-4.5 It should be remembered that wetted dust that is notsubmerged under a cover of water is highly flammable andvery dangerous.

A-4-4.6.1 The reaction of aluminum with water produceshydrogen, which is highly flammable.

A-4-5.2 Some collector bags or other types of media or screenshave fine, noninsulated wire enmeshed into or woven with thecloth or otherwise fastened to it. These are always securelygrounded. It should be pointed out that this is not a positiveguarantee of static charge removal because there is nodependable force to cause the charges to move across the non-conducting area of the fabric to the grounded wires. Often, asubstantial potential difference can be measured. Also, it ispossible that a wire in the cloth could break in such a way thatit is no longer grounded. Such a wire serves as a capacitor andcould store a static charge.

A-4-5.6 Explosion venting is especially important for combus-tible aluminum dust, due to the high maximum explosionpressures reached and the extremely high rate of pressurerise. For information on design of explosion vents and predict-ing the size of the fireball, see NFPA 68, Guide for Venting ofDeflagrations. Dust collectors, when provided by a manufac-turer, seldom have properly sized venting to handle a combus-tible aluminum dust explosion.

A-4-7.1 If a sufficient coolant flow is not used, improperlydesigned or dull tools can produce high temperatures at thetool/workpiece interface, potentially causing ignition of theturnings.

A-4-7.2 For information on bonding and grounding, seeNFPA 77, Recommended Practice on Static Electricity.

A-4-8.2 For information on bonding and grounding, seeNFPA 77, Recommended Practice on Static Electricity.

A-5-2.1 Once ignition has occurred either in a cloud suspen-sion or a layer, an explosion is likely. Often the initial explo-sion is followed by another much more violent explosion,fueled by the dust from accumulations on structural beamsand equipment surfaces that is thrown into suspension by theinitial blast. For this reason, good housekeeping in all areasthat handle dust is vitally important.

A-5-3 Permanently installed vacuum-cleaning systems providethe maximum safety because the dust-collecting device andthe exhaust blower can be located in a safe location outsidethe dust-producing area. The dust collector should be locatedoutside the building, preferably more than 50 ft (15 m) away.If the collector is located closer than 50 ft (15 m), it should besurrounded by a strong steel shield, cylindrical in shape andopen at the top, or closed with a light, unfastened cover. Theshield is closed at the bottom and designed to withstand a blastpressure of 200 psig (1380 kPa gauge). Such a protective bar-ricade will direct an explosion upward and could protect bothproperty and personnel. All suction lines should be providedwith explosion vents and antiflashback valves.

A-5-3.2 For information on static electricity, see NFPA 77, Rec-ommended Practice on Static Electricity.

A-5-3.4 Improper use of vacuum cleaners for aluminum pow-der accumulations can result in fire or explosion. For informa-tion on static electricity, see NFPA 77, Recommended Practice onStatic Electricity.

A-6-1 Since it is almost impossible to extinguish a massive firein dry aluminum powder, the fire problem resolves itself intothe control of fires in the incipient stage. The requirements ofSection 6-2 should be followed if the fire is to be controlledquickly. This is especially true with regard to the application ofthe extinguishing material, as even a minor dust cloud canexplode violently.

A properly ringed fire will develop a hard crust of metaloxide that will ultimately exclude enough oxygen to cause self-extinguishment. It is customary practice, after dispensing theextinguishing material, to leave the area, closing all doorsleading to the area and sealing them with sand. The areashould not be re-entered until combustion has stopped andthe material has cooled.

A-6-2.1 The use of fine, dry sand, preferably less than 20 mesh,or other approved powder is an effective method of isolatingincipient fires in combustible aluminum dust. An ample sup-ply of such material should be kept in covered bins or recepta-cles located in the operating areas where they can be reachedat all times. A long-handled shovel of nonsparking metalshould be provided at each such receptacle to afford a readymeans of laying the material around the perimeter of the fire.

Nearly all vaporizing liquid fire extinguishing agentsreact violently with burning aluminum, usually serving togreatly intensify the fire and sometimes resulting in explo-sion (see A-6-2.6).

Figure A-4-4.4(c) Diagram of five methods of precipitating dust used in precipitators.

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APPENDIX A 651–19

Water hose streams should not be used. The impact of thewater stream can lift enough dust into the air to produce astrong dust explosion. In addition, water reacting with alumi-num can give off highly flammable hydrogen gas.

A-6-2.3 Experience has shown that dry sodium chloride is oneof the most effective chemicals for containing fires involvingaluminum. Fire-fighting salts should be checked periodicallyto ensure that they have not become caked from moisture.Another effective chemical is a nonmetallic flux compoundconsisting of potassium chloride, magnesium chloride, andcalcium fluoride. Commercial dry powder fire extinguishersor agents approved for use on combustible metals are alsoeffective. Covering the fire completely reduces the accessibleoxygen supply, thereby slowing the burning rate so that even-tual extinguishment is reached.

A-6-2.6 Class B extinguishing agents will usually greatly accel-erate combustible aluminum dust fires and can cause theburning metal to explode.

A-6-3 Milling of aluminum with combustible solvents is prac-ticed in the manufacture of aluminum flake used in pigmentsand powders. The material is handled as a slurry during pro-cessing. Some of the product is marketed as a paste; other por-tions are filtered, dried, sometimes polished, and sold as dryflake powder. The solvents employed are generally moderatelyhigh flash-point naphthas. A fire in an aluminum powderslurry is primarily a solvent fire and can be fought using ClassB extinguishing agents, except for halogenated extinguishingagents.

Major producers usually employ fixed extinguishing sys-tems of carbon dioxide or foam in this area. Some Class B por-table extinguishers are provided also. Obviously, judgmentshould be used in determining whether Class B extinguishingagents can be used safely. If the extinguishing agent is care-fully applied, it will be very evident if it accelerates the fire. Ifit does, its use should be discontinued and a dry, inert granu-lar material used. A fire in filter-cake, a solvent-wetted butsemi-dry material containing aluminum, can be a solvent fireor it can at some point exhibit the characteristic of a powderfire, at which time it should be treated as such. If the alumi-num metal has ignited, it can continue to burn under a crustwithout flames.

A-6-3.2 Recent experience has shown that some types ofwater-based foam extinguishing agents can be effective on sol-vent fires.

A-6-3.3 Reignition can occur due to high localized heat orspontaneous heating. To avoid reignition, the residual mate-rial should be immediately smothered.

A-6-3.4.3 For guidance on design criteria for fire flow contain-ment, see NFPA 30, Flammable and Combustible Liquids Code.

A-6-4.1 Exception. For the automatic sprinkler provisions forstorage and use of flammable and combustible liquids, seeNFPA 30, Flammable and Combustible Liquids Code.

A-6-5.3 It is recommended that a practice fire drill be con-ducted once each year to familiarize local fire department per-sonnel with the proper methods of fighting Class D fires.Professional or volunteer fire fighters from outside the plantcannot be expected to be trained for the specific fire and lifehazards associated with aluminum powder and paste fires. In

the interest of their own safety, they should be directed by theplant’s safety officer or fire-fighting officer.

A-6-6 Employees’ health and safety in operations depend onthe recognition of actual or potential hazards, the controllingor eliminating of these hazards, and the training of employeeson safe working procedures.

A-6-7.1 Attention is called to the hazardous conditions thatcould exist both inside and outside the plant if cutting torchesare used to dismantle dust collectors or powder-producingmachinery before all dust accumulations have been removed.

It is a commonly recognized practice that operators of cut-ting or welding torches be required to obtain a written permitfrom the safety or fire protection officer of the plant beforeusing their equipment under any condition around alumi-num powder plants.

A-6-7.4 Under certain circumstances, such as impact withrusted iron or steel, aluminum cannot safely be considered tobe nonsparking since a minor thermite reaction can be initi-ated. For details, refer to “Aluminum and the Gas IgnitionRisk,” by H. S. Eisner and “Fire Hazards in Chemical Plantsfrom Friction Sparks Involving the Thermite Reaction.” (SeeAppendix C.)

A-7-2.3 Safety shoes that meet the following guidelines shouldbe worn by all operating personnel except those persons whoare required to work on electrical circuits or equipment. SeeANSI Z41, Personal Protection — Protective Footwear, for informa-tion.

The following are important elements for safe shoes:(a) Soles should be resistant to embedding particles and to

petroleum solvents, if used.(b) Soles and heels should be attached by sewing or pegging.(c) Nails, metal cleats, or metal plates should not be used.(d) Safety toe caps should be completely covered with a scuff-

resistant material.(e) Soles and heels should be static dissipating.

A-7-2.4 Fire blankets have been found to be effective for extin-guishing clothing fires. They should be distributed in areaswhere water is excluded from the plant area.

A-7-3 Employee Training. The following are important ele-ments of employee training:(a) All employees should be carefully and thoroughly

instructed by their supervisors regarding the hazards oftheir working environment and their behavior and proce-dures in case of fire or explosion.

(b) All employees should be shown the location of electricalswitches and alarms, first-aid equipment, safety equip-ment, and fire-extinguishing equipment.

(c) All employees should be taught the permissible methodsfor fighting incipient fires in pastes and for isolating alu-minum fires.

(d) The hazards involved in causing dust clouds and the dan-ger of applying liquids onto an incipient fire should beexplained.

(e) Strict discipline and scrupulous housekeeping should bemaintained at all times.

(f) Attention should be given to employee training and orga-nizational planning to ensure safe and proper evacuationof the area.

1998 Edition

651–20 MACHINING AND FINISHING OF ALUMINUM AND THE PRODUCTION AND HANDLING OF ALUMINUM POWDERS

Appendix B Electrically Conductive Floors

This appendix is not a part of the requirements of this NFPA doc-ument but is included for informational purposes only.

B-1 General.

B-1.1 Electrically conductive flooring is often employed inaluminum powder plants, although it is recognized that it isdifficult to maintain the conductivity of the floor over a periodof time using currently available materials. Careful examina-tion of the details of this standard will disclose the logic of theuse of conductive flooring materials.

B-1.2 The surface of a conductive floor will provide a path ofmoderate electrical conductivity between all persons and por-table equipment making contact with the floor, thus prevent-ing the accumulation of dangerous static electric charges.

B-1.3 The maximum resistance of a conductive floor is usuallyless than 1,000,000 ohms, as measured between two electrodesplaced three feet apart at any two points on the floor. The min-imum resistance is usually greater than 25,000 ohms, as mea-sured between a ground connection and an electrode placedat any location on the floor. This minimum resistance valueprovides protection for personnel against electrical shocks.Resistance values are checked at regular intervals, usually onceeach month.

B-2 Testing for Minimum and Maximum Resistance. Thefollowing equipment and procedures are accepted practice.

B-2.1 Each electrode will weigh 5 lb (2.27 kg) and will have adry, flat, circular contact area 2.5 in. (63.5 mm) in diameter.The electrode will consist of a surface of aluminum foil 0.0005in. (0.013 mm) to 0.001 in. (0.025 mm) thick, backed by alayer of rubber 0.25 in. (6.35 mm) thick and measuring 40 to60 durometer hardness, as determined by a Shore Type ADurometer or equivalent, per ASTM D 2240, Standard TestMethod for Rubber Property — Durometer Hardness.

B-2.2 Resistance can be measured with a suitably calibratedohmmeter that can operate on a nominal open circuit outputvoltage of 500 volts dc and a short-circuit current of 2.5 mA to10.0 mA.

B-2.3 Measurements can be made at five or more locations ineach room and the results can be averaged.

B-2.4 For compliance with the maximum resistance limit, theaverage of all measurements should be less than 1,000,000ohms.

B-2.5 For compliance with the minimum resistance limit, noindividual measurement should be less than 10,000 ohms andthe average of not less than five measurements should begreater than 25,000 ohms.

B-2.6 Where resistance to ground is measured, two measure-ments are customarily made at each location, with the testleads interchanged at the instruments between the two mea-surements. The average of the two measurements is taken asthe resistance to ground at that location. Measurements arecustomarily taken with the electrode or electrodes more than3 ft (0.9 m) from any ground connection or grounded objectresting on the floor. If resistance changes appreciably with

time during a measurement, the value observed after the volt-age has been applied for about five minutes can be consideredthe measured value.

Appendix C Referenced Publications

C-1 The following documents or portions thereof are refer-enced within this standard for informational purposes onlyand are thus not considered part of the requirements of thisstandard unless also listed in Chapter 8. The edition indicatedhere for each reference is the current edition as of the date ofthe NFPA issuance of this standard.

C-1.1 NFPA Publications. National Fire Protection Associa-tion, 1 Batterymarch Park, P.O. Box 9101, Quincy, MA 02269-9101.

NFPA 30, Flammable and Combustible Liquids Code, 1996 edi-tion.

NFPA 68, Guide for Venting of Deflagrations, 1998 edition.NFPA 77, Recommended Practice on Static Electricity, 1993 edi-

tion.NFPA 497, Recommended Practice for the Classification of Flam-

mable Liquids, Gases, or Vapors and of Hazardous (Classified) Loca-tions for Electrical Installations in Chemical Process Areas, 1997edition.

NFPA 499, Recommended Practice for the Classification of Com-bustible Dusts and of Hazardous (Classified) Locations for ElectricalInstallations in Chemical Process Areas, 1997 edition.

C-1.2 AMCA Publication. Air Movement and Control Associ-ation, Inc., 30 West University Drive, Arlington Heights, IL60004-1893.

AMCA Standard 99-0401-91, “Classifications for Spark-Resistant Construction,” AMCA Standards Handbook, 1991.

C-1.3 ANSI Publication. American National Standards Insti-tute, 11 West 42nd Street, New York, NY 10036.

ANSI Z41, Personal Protection — Protective Footwear, 1991 edi-tion.

C-1.4 ASTM Publications. American Society for Testing andMaterials, 100 Barr Harbor Drive, West Conshohocken, PA,19428-2959.

ASTM D 2240, Standard Test Method for Rubber Property —Durometer Hardness, 1995 edition.

ASTM E 1226, Standard Test Method for Pressure and Rate ofPressure Rise for Combustible Dusts, 1994 edition.

C-1.5 U.S. Bureau of Mines Publications. U.S. Bureau ofMines, Pittsburgh Research Center, Cochrans Mill Road, Pitts-burgh, PA, 15236-0070.

RI 3722, “Inflammability and Explosibility of Metal Pow-ders,” I. Hartmann, J. Nagy, and H. R. Brown, 1943.

RI 6516, “Explosibility of Metal Powders,” M. Jacobsen, A.R. Cooper, and J. Nagy, 1964.

C-1.6 Other Publications. Eisner, H. S., “Aluminum and theGas Ignition Risk,” The Engineer, London, February 17, 1967.

Gibson et al., “Fire Hazards in Chemical Plants from Fric-tion Sparks Involving the Thermite Reaction,” Industrial Chem-ists Engineering Symposium Series, No. 25, London, 1968.

1998 Edition

INDEX 651–21

Index

1998 National Fire Protection Association. All Rights Reserved.The copyright in this index is separate and distinct from the copyright in the document which it indexes. The licensing provisions set forth for thedocument are not applicable to this index. This index may not be reproduced in whole or in part by any means without the express written per-mission of the National Fire Protection Association, Inc.

-A-

Air-moving equipment . . . . . . . . . . . . . . . . . . . . . see Fans and blowersAlarms, dust collectors . . . . . . . . . . . . . . . . . . . 2-5.2, A-2-5.1, A-4-2.4.1Aluminum chips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7.3

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5, A-1-5Aluminum dust . . . . . . . . . . . 1-1.2 to 1-1.3, 1-2; see also Dust collection

systemsDefinition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5, A-1-5Dust-producing operations . . . . . . . . . . . . . . . . . . . . . . . . . 4-2, A-4-2Electrical classification of dusty locations . . . . . . . . . . . A-2-2.10.1.1Extinguishing agents and application techniques . . . . . . .6-2, A-6-2From fans and blowers . . . . . . . . . . . . . . . . . . . . . 2-4.10.4, A-2-4.10.4Fugitive dust accumulations, cleanup of . . . . . . . . . . . . . 5-2, A-5-2.1Minimum explosible concentrations. . . . . . . . . . . . . . 2-4.8.5, 4-3.3,

A-2-4.8.5, A-4-2.1, A-4-3.3Prevention of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4.2, 3-3.2Transfer operations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5, A-3-5

Aluminum flake. . . . . . . . . . . . . . . . . . . . . . . . . see Aluminum powderAluminum granules (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Aluminum metal, primary production of . . . . . . . . . . . . . . . . . . . 1-1.5Aluminum paste . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1.1, 1-1.3, 1-2

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Handling of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Chap. 3, A-3

Aluminum powder . . . . . . . . . . . 1-1.1 to 1-1.3, 1-2; see also Conveyingof aluminum powder

Charging and discharging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4.5Containers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4.4 to 2-4.6Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Fans, passing through. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4.10.2Handling . . . . . . . . 1-1.3, 1-2, 2-3.1, 2-4, A-2-3.1, A-2-4, Chap. 3, A-3Incompatible materials. . . . . . . . . . . . . . . . . . . . . . . 2-6(d), A-2-6(d)“Nondusting” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3, A-1-1.1, A-3-3Oxygen in production process. . . . . . . . . .2-4.9.2, 3-4.1.2 to 3-4.1.3,

A-2-4.9.1 to A-2-4.9.2, A-3-4.1Storage . . . . . . . . . . . .see Storage, of aluminum dusts, powders, or

pasteTransfer operations. . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4.6, 3-5, A-3-5Transportation of . . . . . . . . . . . . . . . 1-1.4, 2-4.7.1 to 2-4.7.2; see also

Conveying of aluminum powderAluminum powder production plants . . . . . . . . . . . . 1-1.1, 1-2, A-1-1.1,

Chap. 2, A-2Building construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5Fire prevention, protection, and procedures . . . . . . . . Chap. 6, A-6Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1Safety procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chap. 7, A-7Separation distances . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1.1 to 2-1.2

Applicability of standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4Approved (definition). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5, A-1-5Argon as inerting agent . . . . . . . . . . . . . . . . . . . . . . . . . 2-4.9.2, A-2-4.9.2Authority having jurisdiction (definition) . . . . . . . . . . . . . . . .1-5, A-1-5

-B-

Bag-type dust collectors . . . . . . . . . . . A-2-5.1, A-3-5, A-4-2.4.1, A-4-5.2Basements (production plants) . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2.5Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3.2.4, A-2-3.2.4.1

Fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4.10.5, A-2-4.10.5Sealing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3.2.4.1, A-2-3.2.4.1Wet mills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4.1.5

Blowers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see Fans and blowers

BondingBuilding steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2.9.1, A-2-2.9.1Containers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4.5 to 2-4.6Ducts. . . . . . . . . . . . . . . . . . . . . . . . . 2-4.8.2, 4-3.6, A-2-4.8.2, A-4-3.6Dust collection systems . . . . . 2-5.1.5, 3-4.2.2, 4-3.6, 4-8.2, A-2-5.1.5,

A-3-4.2.2, A-4-3.6, A-4-8.2Machinery . . . . . . . . . . . . . . . . . . . . 2-3.2.3, 4-3.6, A-2-3.2.3, A-4-3.6Process equipment. . . . . . . . . . . . . . . . . . . . . . . . . .2-2.9.1, A-2-2.9.1

Buffing operations, dust collection for . . . . . . . . . . . . . . . . 4-2.3, 4-2.5Buildings . . . . . . . . . . . . see also Aluminum powder production plants

Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2Interconnected . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2.8.1, A-2-2.8.1

-C-

Carbon dioxideExtinguishing agents . . . . . . . . . . . . . . . . . . . . . . . . . . .6-3.3, A-6-3.3As inerting agent . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4.9.2, A-2-4.9.2

Charging and discharging aluminum powder . . . . . . . . . . . . . . . . 2-4.5Clothing

Outer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-2.1Work . . . . . . . . . . . . . . . . . . . . . . . . . 7-2.2 to 7-2.4, A-7-2.3 to A-7-2.4

Collection systems. . . . . . . . . . . . . . . . . . . . see Dust collection systemsCombustible aluminum dust. . . . . . . . . . . . . . . . . . see Aluminum dustCompressed air

Blowdown. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4Fittings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8

ConstructionBuilding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2Ducts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3.5

ContainersAluminum powder. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4.4 to 2-4.6

Portable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4.7Sealed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6, A-2-6(d)

Sludge disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4.8.2Control stations, electrical equipment . . . . . . . . . . . . . . . . . . . 2-2.10.2Conveying of aluminum powder . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

Fans and blowers . . . . . . . . . . . . . . . 2-4.10, A-2-4.10.1, A-2-4.10.4 toA-2-4.10.5

Inert-gas conveying system . . . . . . . . . . . . . 2-4.9, 2-4.10.1, 2-4.10.3,A-2-4.9.1 to A-2-4.9.2, A-2-4.10.1

Pneumatic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4.8Sparks, prevention of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3.1.2

Cooling (production buildings) . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2.11Cutting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7, A-4-7Cyclone-type dust collectors . . . . . . . . . . . . . 2-5.2.1, A-2-5.1, A-4-2.4.1

-D-

Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5, A-1-5Deluge showers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-2.4Doors (production plants) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2.7Dry-type dust collectors . . . . . . . . . . . . 2-5.1.7 to 2-5.1.8, 4-5, A-2-5.1.7,

A-4-5; see also Cyclone-type dust collectorsHigh-temperature warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5.2Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5.1.1, 4-2.4, A-4-2.4Personnel safety . . . . . . . . . . . . . . . . . . . . . . . 2-5.1.1, 4-2.4.1, A-4-2.4

Ducts, conveying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4.8, A-2-4.8Fans and blowers in . . . . . . . . . . . . . . . . . . . . . . . 2-4.10.1, A-2-4.10.1Inert gas systems . . . . . . . . . . . . . . . . . . .2-4.9.6, 2-4.10.1, A-2-4.10.1

Ducts, dust collection . . . . . . . . . . . 2-5.1.4, 2-5.1.8, 4-3, 4-4.1 to 4-4.2,

1998 Edition

651–22 MACHINING AND FINISHING OF ALUMINUM AND THE PRODUCTION AND HANDLING OF ALUMINUM POWDERS

4-5.7 to 4-5.8, A-4-3, A-4-4.1 to A-4-4.2Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3.5Dust collection system location and . . . . . . . . . . . . . . . 4-2.2, A-4-2.2

Dust, aluminum. . . . . . . . . . . . . . . . . . . . . . . . . . . . see Aluminum dustDust collection systems. . . . . . . . . . . . . 2-5, 4-2.1, A-2-5, A-3-5, A-4-2.1;

see also Dust collectorsDedicated to use with aluminum only . . . . . . . . . . . . . 4-2.5, A-4-2.5Ducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see Ducts, dust collectionElectrical equipment . . . . . . . . . . . . . . . . . . . . . . . . 3-4.2.2, A-3-4.2.2Fans and blowers . . . . . . . . . . . . . . . . . . . . . . see Fans and blowersLocation . . . . . . . . . . . . . . . . . . . . . . . . . 4-2.2, 4-2.4, A-4-2.2, A-4-2.4Recycling of air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5.1.6, 4-6Safety interlocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4.7

Dust collectors . . . . . . . . . . . . 2-5.1, A-2-5.1, A-4; see also Bag-type dustcollectors; Cyclone-type dust collectors; Dry-type dust collectors; Media-type dust collectors; Wet-typedust collectors

Filter medium . . . . . . . . . .2-5.3, 3-4.3.2, 4-4.4, 4-5.2, A-2-5.3, A-4-5.2High-temperature warning . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5.2Inert gas systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4.9.6Plasma spray operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4.3

-E-

Egress, means of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2.7.2, 2-2.8.2Electrical classification

Hybrid mixtures, electrical equipment used with . . . . . . . A-3-4.1.6Powder manufacturing areas . . . . . . . . . . . . . 2-2.10.1.1, A-2-2.10.1.1Wet solvent milling areas . . . . . . . . . . . . . . . . . . . . . 3-4.2.3, A-3-4.2.3

Electrical systems and equipment . . . . . . . . . . . . . . . . . . . 2-2.10, 3-4.2Dust-producing equipment, shutdown of . . . . . . . . . . . . . . . . . 4-4.7Hybrid mixtures, processing of . . . . . . . . . . . . . . . . . . . . . . A-3-4.1.6Processing and finishing operations . . . . . . . . . . . . . . . . 4-8, A-4-8.2

Electrically conductive floors . . . . . . . . . . . . . . . . . . . . . . . . . . . . App. BEmergency lighting systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2.10.3Emergency procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3, A-7-3Employee training programs . . . . . . . . . . . . . . . . . 6-6, 7-3, A-6-6, A-7-3Enclosed passageways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2.8Enclosures, machine . . . . . . . . . . . . . . . . . . . . . 4-2.1, A-4-2.1 to A-4-2.2Equivalency to standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3, 1-4.2Exit doors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2.7.2Explosion prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2Explosion propagation between building units . . . . . . . . . . . . . 2-2.8.1Explosion venting

Dry dust collectors . . . . . . . . . . 2-5.1.7, 4-5.6, A-2-5.1.7, A-4-2.4.1 toA-4-2.4.2, A-4-5.6

Ductwork . . . . . . . . . . . . . . . . . . . . . . . . . 2-4.8.6 to 2-4.8.7, A-2-4.8.6Enclosed passageways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-2-2.8.1Powder processing buildings . . . . . . . . . . . . . . . . . . . . . 2-2.6, A-2-2.6

Extinguishing agents and application techniquesAluminum dusts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2, A-6-2Solvent-wetted powders . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3, A-6-3

-F-

Fans and blowersConstruction and arrangement . . . . . . . 2-2.11.2, 2-4.10, A-2-4.10.1,

A-2-4.10.4 to A-2-4.10.5Dust collection systems. . . . . . . . . . . 4-4.3, 4-4.6.3, 4-4.7, A-2-4.10.4,

A-4-2.4.1Filter medium, dust collectors . . . . . . . . . . . . . . . . see Dust collectorsFinishing operations . . . . . . . . . . . . . . . . . . 1-1.2, 1-2, 2-3, Chap. 4, A-4Fire blankets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-7-2.4Fire doors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2.7.1Fire prevention, protection, and procedures . . . . . . .1-2, Chap. 6, A-6Fire-fighting organization . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5, A-6-5.3Flakes, aluminum . . . . . . . . . . . . . . . . . . . . . . . see Aluminum powderFlammable and combustible solvents . . . . . . . . . . . . . 3-4.1.6, A-3-4.1.6Flammable gases or vapors . . . . . . . . . . . . . . . . . . . . . . . . . . . A-3-4.1.6Flashlights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2.10.5Floor construction (production plants) . . . . . . . . . . . . . . . . . . . . . 2-2.3

Floors, electrically conductive. . . . . . . . . . . . . . . . . . . . . . . . . . . App. BFlue gas as inerting agent . . . . . . . . . . . . . . . . . . . . . . 2-4.9.2, A-2-4.9.2Frictional heating, prevention of . . . . . . . . . . . . . . . . 2-3.1.4, A-2-3.1.4

-G-

GasesFlammable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-3-4.1.6Inert . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see Inert gas

Grinding operations, dust collection for . . . . . . . . . . . . . . . 4-2.3, 4-2.5Grounding

Building steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2.9.1, A-2-2.9.1Collector bags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-2-5.3Containers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4.5 to 2-4.6Ducts. . . . . . . . . . . . . . . . . . . . . . . . . 2-4.8.2, 4-3.6, A-2-4.8.2, A-4-3.6Dust collection systems . . . . . . . . . . . . . 2-5.1.5, 3-4.2.2, 4-3.6, 4-8.2,

A-2-5.1.5, A-3-4.2.2, A-4-2.4.1, A-4-3.6, A-4-5.2, A-4-8.2Handling equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4.3, 3-3.3Machinery . . . . . . . . . . . . . . . . . . . . 2-3.2.3, 4-3.6, A-2-3.2.3, A-4-3.6Process equipment . . . . . . . . . . . . . . . . . . . . . . . . . 2-2.9.1, A-2-2.9.1Sawing, grinding, and cutting equipment . . . . . . . . . . 4-7.2, A-4-7.2

-H-

Halogenated extinguishing agents . . . . . . . . . . . . . . . . . . . . . . . . . 6-3.1Hand tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4.3, 3-3.3Handling, of aluminum dusts, powders, or paste . . . . . . . . . . . . 1-1.3,

1-2, 2-3.1, 2-4, A-2-3.1.4, Chap. 3, A-3Heating (production plants) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2.11Helium as inerting agent . . . . . . . . . . . . . . . . . . . . . . . 2-4.9.2, A-2-4.9.2High-temperature warning, dust collectors . . . . . . . . . . . 2-5.2, A-2-5.1,

A-4-2.4.1Hoods . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2.1, 4-5.8, A-4-2.1 to A-4-2.2Housekeeping . . . . . . . . . . . . . . . . . . . . . . . . .2-4.1, 3-3.1, Chap. 5, A-5

Compressed air blowdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4Frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6Fugitive dust accumulations, cleanup procedures for . . . . . . . . 5-2,

A-5-2.1Spilled aluminum powder, cleanup of . . . . . . . . . . . . . . . . . . . . 5-2.3Vacuum systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3, A-5-3Water cleaning requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

Hybrid mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-3-4.1.6Hydrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-4-4.1

-I-

Ignition sources, control of . . . . . . . . . . . . . . . . . . .6-7, A-6-7.1, A-6-7.4Industrial trucks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4.7.2, 3-3.4Inert gas

Conveying system. . . . . . . . . . . 2-4.9, 2-4.10.1, 2-4.10.3, A-2-4.9.1 toA-2-4.9.2, A-2-4.10.1

Gasline fittings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8To pressurize bearings and seals . . . . . . . . . . . . . . . . . . . . A-2-3.2.4.1

Inspections, safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4

-L-

Labeled (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Lightning protection (production plants) . . . . . . . . . . . . . . . . . 2-2.9.2Listed (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5, A-1-5

-M-

Machinery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3, 3-4, A-3-4Charging or discharging aluminum powder to . . . . . . . . . . . . . 2-4.5General precautions . . . . . . . . . . . . . . . . . . . . . . . . . .2-3.1, A-2-3.1.4Requirements for. . . . . . . . . . . . . . . . . . . 2-3.2, A-2-3.2.3, A-2-3.2.4.1

1998 Edition

INDEX 651–23

Start-up operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3.3Wet milling of aluminum powder . . . . . . . . . .3-4.1, 3-4.2.3, A-3-4.1,

A-3-4.2.3Machining operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7, A-4-7Magnesium dust, minimum explosive concentrations . . . . . . . A-4-2.1Maintenance

Electrical equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2.10.4Operational equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5Safety equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5

Make-up air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2.11.3Manufacturing facilities . . . see Aluminum powder production plantsMedia-type dust collectors . . . . . . . . 3-4.3.1, A-2-5.1, A-4-2.4.1, A-4-5.2Moisture prevention . . . . . . . . . . . . . . . . . . see Water, protection from

-N-

Nitrogen as inerting agent . . . . . . . . . . . . . . . . . . . . . . 2-4.9.2, A-2-4.9.2“Nondusting” aluminum powder. . . . . . . . . . . . . . . . 3-3, A-1-1.1, A-3-3

-O-

Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3, 3-4, A-2-3, A-3-4Charging and discharging of aluminum powder . . . . . . . . . . . 2-4.5General precautions . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3.1, A-2-3.1.4Oxidation of finished product . . . . . . . . . . . . . . . . 3-4.1.2 to 3-4.1.3,

A-2-4.9.1, A-3-4.1Processing and finishing . . . . . . . . . . . . 1-1.2, 1-2, 2-3, Chap. 4, A-4Wet milling of aluminum powder . . . . . . . . . .3-4.1, 3-4.2.3, A-3-4.1,

A-3-4.2.3Oxygen concentration, inert gas/liquid . . . . . . . . . . . . 2-4.9.2, 2-4.9.4

3-4.1.2 to 3-4.1.3, A-2-4.9.1 to A-2-4.9.2, A-3-4.1

-P-

Passageways, enclosed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2.8Personal protective equipment . . . . . . . . . . 7-2, A-4-2.4(b), A-7-2.3 to

A-7-2.4Plasma spray operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4.3Pneumatic conveying (of aluminum powder) . . . . . . . . . .2-4.8, A-2-4.8Polishing operations, dust collection for . . . . . . . . . . . . . . . . . . . 4-2.3Portable containers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4.7Portable electrical equipment . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2.10.5Powder, aluminum . . . . . . . . . . . . . . . . . . . . . . see Aluminum powderPowder collectors . . . . . . . . . . . . . . . . . . . . . . . . . . see Dust collectorsProcess areas, interconnected . . . . . . . . . . . . . . . . . . . 2-2.8.1, A-2-2.8.1Processing operations . . . . . . . . . . . . . . . . . 1-1.2, 1-2, 2-3, Chap. 4, A-4Production plants . . . . . . . . see Aluminum powder production plants

-R-

Recycling of air, dust collectors . . . . . . . . . . . . . . . . . . . . . . 2-5.1.6, 4-6Referenced publications. . . . . . . . . . . . . . . . . . . . . . . . Chap. 8, App.CRemote electrical equipment control stations . . . . . . . . . . . . . 2-2.10.2Roof construction (production plants) . . . . . . . . . . . . . . .2-2.4 to 2-2.5

-S-

Safety requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chap. 7, A-7Dry-type dust collectors . . . . . . . . . . . . . . . . . 2-5.1.1, 4-2.4.1, A-4-2.4Fan and blower operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4.10.3

Sawing operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7, A-4-7Screens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3.2.6Separators

Liquid precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-4-4.4Magnetic or pneumatic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3.2.6

Shall (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Shoes, safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-2.3, A-7-2.3Should (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Shutdown

Dust-producing equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4.7Fans and blowers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4.10.6

Slurry pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4.1.7Smoking prohibition . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4.8.4, A-2-6(g)Solvent pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4.1.7Solvents, flammable or combustible

Fire-fighting procedures . . . . . . . . . . . . . . . . . . . . . . . . . . .6-3, A-6-3Hybrid mixtures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-3-4.1.6Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4.1.6, A-3-4.1.6Wet solvent milling areas, electrical classification of . . . . . . . 3-4.2.3,

A-3-4.1.6, A-3-4.2.3Sparks, prevention of. . . . . . . . . . . . . . . . . . . 2-3.1.2, A-4-2.4.1, A-4-2.5Spilled aluminum powder

Cleanup of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-2.3Prevention of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4.2, 3-3.2

Sprinkler systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4, A-6-4.1Standard (definition) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Static electricity . . . . . . . . . 2-3.1.2, 7-2.3; see also Bonding; Grounding

Collector filter medium. . . . . . . . . . . . . 2-5.3, 4-5.2, A-2-5.3, A-4-5.2Dust collection systems . . . . . . . . . . . . . . . 2-5.1.3, 2-5.1.5, A-2-5.1.5,

A-4-2.4(b)Storage, of aluminum dusts, powders, or paste . . . . . . . . . . . . . . 1-1.3,

1-2, 2-6, 3-2, A-2-6(d)

-T-

Temperature-sensing elements . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5.2.1Tools

Cutting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7.1, A-4-7.1Hand. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4.3, 3-3.3

Training programs. . . . . . . . . . . . . . . see Employee training programsTramp metal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3.2.6Transfer operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-5, A-3-5Transportation of aluminum powder . . . . . . . . . . . . . . 1-1.4, 2-4.7.1 to

2-4.7.2; see also Conveying of aluminum powder

-V-

Vacuum-cleaning systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-3, A-5-3Ventilation

Wet milling operations . . . . . . . . . . . . . . . . . . . . . .3-4.1.6, A-3-4.1.6Wet-type collector sump . . . . . . . . . . . . . . . . . . . . . . 4-4.6, A-4-4.6.1

Venting, explosions . . . . . . . . . . . . . . . . . . . . . . . see Explosion venting

-W-

Wall construction (production plants) . . . . . . . . . . . . . . . 2-2.1 to 2-2.2Water, protection from

Dry-type dust collection systems . . . . . . . . . . . . . . . . . . . . . . . . . 4-5.4Inert gas-conveying system . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4.9.3Leakage prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3.1.3Moisture-tight ducts. . . . . . . . . . . . . . . . . . . . . . . . .2-4.8.3, A-2-4.8.3Powder containers . . . . . . . . . . . . . . . . . . . . . . . . . . .2-6(b), A-2-6(f)Wet milling operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4.1.4

Water cleaning requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5Wet milling of aluminum powder . . . . . . . . . . . . . 3-4, 6-3, A-3-4, A-6-3Wet-type dust collectors . . . . . . . . . . . . . . . . . . . . . . . 4-4, A-4-2.2, A-4-4

Sludge disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-4.8Sump venting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4.6, A-4-4.6.1

Windows (production plants) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2.7

C-E 1998 Edition