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SafetyBulletinU.S. Chemical Safety and Hazard Investigation Board

EXPLOSIONAT ASCO: DANGERSOF FLAMMABLE GAS ACCUMULATION

No. 2006-01-B | January 2006

ASCO History

ASCO, a family-owned business,began generating and packagingacetylene in 1982 for sale in theNew York and Philadelphiametropolitan areas. At the time ofthe incident, the company

employed 14 workers. ASCOmanufactured acetylene at thePerth Amboy site. In July 2004,ASCO also began purchasingacetylene directly from apetrochemical

1facility to

supplement their production.

Figure 1. North side of ASCOfacility. Damage to building 46and debris around the decant

water tanks.

Facility LayoutThe ASCO manufacturing facilitywas located in an industrial areanorthwest of the OutercrossingBridge which connects New Jersey

to Staten Island, NY. Theacetylene generating processequipment (manufactured byRexarc2), cylinder fillingoperations, offices, and break roomwere housed in Building 46 (Figure2). Directly outside Building 46were six decanting tanks thatsurrounded a wood-framed shed.The shed contained water pumpsand related piping. Receivingdocks used to offload purchasedacetylene, an adjacent building

used for cylinder refurbishing, andan acetone storage tank were alsopart of the operation at ASCO.

1 Acetylene is also a by-product of certainpetrochemical processes and may bepurchased from such sources when theeconomics are favorable.

2 Rexarc International, Inc. is a manufacturerand provider of compressed gasprocessing equipment.

Summary

Accumulation of flammable gas in an enclosed space can produce apowerful explosion, destroying lives and property. OnJanuary 25, 2005, acetylene flowed into the lime shed at Acetylene ServicesCompany (ASCO), a Perth Amboy, New Jersey, acetylene manufacturer andpackager. This resulted in just such an explosion, which killed threeworkers and seriously injured a fourth (Figure 1). The shed was destroyedand the nearby manufacturing building severely damaged.

The U.S. Chemical Safety and Hazard Investigation Board (CSB) issues thisSafety Bulletin to focus attention on flammable gas hazards. It recommendsspecific actions that companies generating acetylene, and others, shouldtake to prevent similar incidents, which include:

Maintain up-to-date operating procedures and checklists for the entire

operating process.

Train staff on the operating procedures and require them to

demonstrate their ability to correctly follow them.

Relocate drains and vents connected to flammable gas-containing

equipment to safe, preferably outside, locations.

Ensure that buildings and enclosures that could potentially contain

acetylene meet the requirements of National Fire Protection

Association (NFPA) Standard 51A.

Inspect, test, and maintain check valves and block valves.

Provide positive isolation on lines connected to the process to ensure

that back flow of explosive gases cannot occur.


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CSB Investigation Reports are

formal, detailed reports onsignificant chemical accidents andinclude key findings, root causes,and safety recommendations. CSBHazard Investigations are broaderstudies of significant chemicalhazards. CSB Safety Bulletins areshort, general-interest publications

that provide new or noteworthyinformation on preventing chemicalaccidents. CSB Case Studies areshort reports on specific accidentsand include a discussion of relevant

good pract ices for prevention. All

reports may contain include safetyrecommendations whenappropriate. CSB InvestigationDigests are plain-languagesummaries of InvestigationReports.

Acetylene

Acetylene is a colorless, highlyreactive, and extraordinarilyflammable gas. It has a sharpgarlic-like odor and is slightlylighter than air. It is flammableover a wide range ofconcentrations, from about 2.5% to82% in air. Gaseous acetylene canexplosively decompose3withextreme violence if pressurized tomore than 14.5 psig. It is also

unstable and prone to explosivedecomposition if liquefied.Consequently, acetylene isdistributed in steel cylinders thatare packed with a high surface areaporous media and filled with liquidacetone.

4The acetylene is

dissolved in the acetone at lowpressure, stabilizing it againstdecomposition.

In the ASCO operation, gaseousacetylene (C

2H

2)

was made by

mixing calcium carbide, (CaC2)

with water (H2O). Lime (Ca(OH)

2)

was a by-product of the reactionwhich also liberated heat.

CaC2 + 2H2O JJJJJ C2H2 (acetylene

gas) + Ca(OH)2 (lime) + heat

The mixing took place in a

horizontal vessel called agenerator (Figure 3). The generatorwas partially filled with water.Calcium carbide was metered in ata controlled rate based ongenerator pressure. The processwas partially automated. If thecalcium carbide hoppers feedingthe generator were kept full the

3 Decomposition is the breakdown of achemical into less complex molecules.

Acetylene can decompose violently to a

mixture of hydrogen, simple hydrocarbons

and carbon soot.

4 Examples of porous media include: balsawood, charcoal , finely shredded asbestos,corn pith, and calcium silicate.

process could run continuously.

Compressors transferred theacetylene through additionalequipment where impurities wereremoved. The purified gas thenflowed to the filling room where itwas packaged in cylinders. The by-product lime (Ca(OH)

2) slurry was

continuously drained from thegenerator to a pit located outsidethe building. The lime slurry wasthen pumped from the pit into thedecanting tanks.

Figure 2. ASCO layout. Drawing is not to scale.

Acetylene

Generation


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Decanting Tanks The water that accumulated intanks #5 and #6 was pumped backto the generator as needed. Thisrecycled water was the lowest-costsource for the generator, althoughcity water could also be used andwas required to make up losses.

Figure 4. Decant Tank Arrangement.

The shed housed two electricallydriven pumps: one to off-load

settled lime sludge from thedecanting tanks and the other torecycle the decanted water to thegenerator. It also containedelectrical breakers, pump controlswitches and an overheadfluorescent light. The shed washeated by a wall mounted propanespace heater that preventedfreezing of the pumps andassociated piping. The shed hadno mechanical ventilation.

Propane Heater

A direct-vent propane space heaterrated for residential use wasmounted on the wall of the shed(Figure 5).5 The heater drew inoutside air for combustion throughthe outer of two concentric pipes.Exhaust gases exited through theinner pipe. The combustionchamber was completely sealedfrom the shed interior. The air inthe shed did not come in contactwith the flame or the products ofcombustion.

The heater warmed the room bynatural convection.6 The outer skinof the combustion chamber wasapproximately 1100F duringoperation. The heater was alsoequipped with an automatic shut-off valve designed to stop thesupply of propane to the

combustion chamber if the pilotlight went out. Testing after theincident found that this automaticshut-off valve functioned asdesigned.

Figure 3. A. ASCO acetylene generator. The area (circle) enlarged in B

shows a check valve on the water supply line.

5 The heater was rated for residential use bythe Canadian Standards Association.

6 Natural convection is the transfer of heatdue to buoyancy-induced flow across a

heated surface.

Wooden Shed(Lime Shed)

The ASCO facility included a

wooden shed constructed in-between the six decant tanks.Itwas approximately 15 feet wide by28 feet long and had a roof thatsloped from 8 feet to 6 feet inheight. The shed was constructedusing the tank shells to make upportions of the walls, as shown inFigure 2. The concrete pad thatsupported the tanks served as theshed floor.

The lime slurry was pumped from

the lime pit into tank #1. The limeparticles settled and the wateroverflowed into tank #2. Furtherseparation of lime and watercontinued in subsequent tanks.When the water reached tanks #5and #6 it contained minimalamounts of lime (Figure 4). Settledlime sludge was pumped from thebottom of the tanks, from time totime, and removed by a contractor.

ASCO used six open-top decantingtanks, connected in series, to holdlime by-product and also toprepare and store water for re-usein the generator. The six steelatmospheric storage tanks wereapproximately 20 feet tall by 10 feetin diameter and were arranged intwo rows of three tanks, alignednorth to south.


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The Incident

During the early morning hours ofJanuary 25, ASCO employees filledcylinders with purchasedacetylene. At approximately 9:30am, with the depletion of thesupply of purchased acetylene,

they began to produce acetylenefrom calcium carbide in thegenerator.

Because of heavy snowfall, workerswere shoveling snow in the areasouth of the decant tanks near theloading dock. At 10:36 am, anexplosion occurred, centered in theshed. Two of the workersimmediately south of the shed werekilled instantly. A third workerfarther south, closer to the loading

dock, was severely injured and waspronounced dead shortly afterarriving at the Newark MedicalCenter. A fourth worker who wasin the loading dock/lime pit areawas very seriously injured by theblast.

The medical examiner identifiedextensive fragmentation, laceration,and pulverization of internalorgans, bones, and muscles in thevictims. Injuries of this type areconsistent with exposure to a shockwave from a high-speeddeflagration or detonation.7

The shed was completelydestroyed. Its walls were highlyfragmented, essentially reduced tosplinters. Debris was hurled as faras 450 feet from the site. Theexplosion blew two large holes inthe masonry wall of Building 46,toppling several cylindermanifolds and scattering acetylenecylinders across the filling roomfloor. Windows were shatteredand several doors were blown into

the building or knocked off theirhinges or rails. No fire occurredafter the explosion.

7 A detonation is a rapid explosion thatgenerates supersonic pressure waves (shockwaves) in the surrounding area. Pressurewaves from a deflagration are subsonic.

Fuel Source

The two explosive materialspotentially present were acetyleneand propane. Acetylene from thegenerator could have reached theshed via a drain valve on thedecanted water line at the southend of the shed. This valve wascommonly opened and left open atthe end of work each day during

the winter months to protect thewater line from freezing. Propanecould have leaked from thepropane heater located at the northend of the shed or from the propanesupply tubing. Analysis of thedamage pattern indicated that theexplosion was a detonation or atthe least a high-speed deflagration.The evidence overwhelminglysupports acetylene as the explosive

material in this incident (Table 1).

INCIDENTSCENARIO

Acetylene produced in thegenerator flowed back past thecheck valve through the recycledwater line into the shed by way ofthe open drain valve (Figures 6 and7). The acetylene gas accumulated

inside the shed, ignited, andexploded.

Figure 5. A. An exemplar of the ASCO shed heater (same make and model).B. Schematic diagram of the heater.


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8 The Baker-Strehlow-Tang (BST) methodpredicts vapor cloud explosioncharacteristics based on the reactivity of

the fuel and the degree of confinement andcongestion in the area of the explosion.The reactivity is related to the flame speed

of the material being evaluated. Acetyleneis classified as a high-reactivity material,

while propane is considered to be ofmoderate reactivity. Confinement andcongestion are key geometrical parametersin the BST method. Low confinementmeans that the gases produced in anexplosion are free to expand, while highconfinement means they are constrained, asinside a pipe. Low congestion is associated

with open rooms, such as the shed atASCO, while highly congested areas aretypically packed with pipes, equipment, orstructural supports, few of which were

present in this case.

9 Flow testing conducted by the CSB andOSHA after the explosion demonstrated

that acetylene could flow from thegenerator into the shed through the waterrecycle line.

10 The acetylene generator was startedapproximately 66 minutes before theexplosion. This produced a pressurizedsource of acetylene that could then flow to

the shed through the open or leakingvalves on the recycle water line.

Figure 6. Simplified acetylene system flow diagram. The red line shows the

leak path of acetylene from the generator into shed.11

Acetylene

Easily capable of detonation or high-speeddeflagration in the shed by BST Method.8

Leak path into shed demonstrated by post-incident testing.9History of reverse flowthrough check valve.

.

Explosion shortly after start-up of acetylenegenerator.10

Leakage into shed at location remote fromheater facilitated gas cloud accumulation.

Propane

Not capable of detonation or high-speed deflagrationin the shed by BST method

No evidence of leak path into shed.

Heater had run without evidence of leakage forseveral weeks.

Any leakage from the short length of propane supplytubing would be in close proximity to an ignitionsource (the heater) accumulation unlikely.

Table 1. Fuel source for the Explosion

11 CSB could not positively ascertain theposition of the valve labeled FoundClosed. The plant manager stated after

the incident that he closed some valvesimmediately after the explosion, one of

which may have been the valve labeledFound Closed. This valve was later

tested at OSHAs Utah laboratory. Thetesting confirmed that this valve leakedsignificantly in the closed position.


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INCIDENT

ANALYSIS

designed for the presence ofacetylene. This potential hazard

was not recognized by ASCO.

Figure 6. Post explosion view ofrecycle water line to/from the

generator and open drain. Leak pathhighlighted.

Process hazards analysis (PHA)12

is a team-based technique foridentifying hazards and is arequired element under the OSHAProcess Safety ManagementRegulation (PSM).13 PHAs assist inidentifying potential hazards, thepotential consequences of hazards,

and the safeguards that are inplace to protect against identifiedhazards. They also facilitate thesystematic generation ofrecommendations to help eliminateor control identified hazards.

The ASCO 1996 PHA did notidentify the hazards created by thelocation of the decant water linedrain in the shed. The PHA wasnot updated in 2001, as requiredunder PSM. In failing to update thePHA, a second opportunity toidentify the conditions that led tothe explosion was missed.

The drain valve on the recycledwater line (discussed above) wasfound in the open position followingthe explosion. This indicates that therecycle system was not operating atthe time of the incident. The CSBbelieves that the operators closed thecity water supply valve prior tostarting up the recycled watersystem, leaving the generator with

no source of pressurized water toprevent the reverse flow of acetylene.Closing the drain valve and placingthe recycled water system intoservice before shutting off the citysupply would likely have preventedthe backflow of acetylene into theshed.

ASCO had an operators manual forthe Rexarc generator. However, itdid not address the recycled watersystem. Consequently, the operators

had no written guidance on thecorrect operation of the recyclesystem or on the consequences ofdeviation from the intendedoperating sequence.

Some general procedures wereposted on the wall in the generatorroom. However, they gave noguidance on the appropriatesequence for adding water, city orrecycled, to the generator. Stafftraining was not adequately

documented and the sequence ofhow each worker operated theprocess was not consistent.

13 ASCOs Perth Amboy acetylene generatingfacility contained flammable liquids or gasesin quantities greater than 10,000 pounds(acetylene and acetone). This required

ASCO to comply with the OccupationalSafety and Health Administration (OSHA)29 CFR 1910.119 Standard.

12 Process Hazards Analysis (PHA) is theidentification of undesired events that lead

to the materialization of a hazard, theanalysis of the mechanisms by which theseundesired events could occur, and usually

the estimation of the consequences(CCPS).

Figure 7. Post explosion view of

recycled water line to/from thegenerator and open drain.

Acetylene Leak PathFreeze

protection practices created apotential flow path from theacetylene generator to the shedthrough the open drain valve.

Sequence of OperationsThe

sequence of operation the dayof the incident pressurized thegenerator with acetylene gasbefore establishing the recycle

water supply to the generator.

Check Valve Back FlowThe

check valve, supplied byRexarc Inc., in the water line atthe acetylene generator did notprevent back flow, as it shouldhave done. The design of thecheck valve made it susceptibleto malfunction.

Building Design/Ignition

SourceAcetylene flowed intothe unventilated shed, whichcontained multiple potentialignition sources, accumulated,and exploded. The hot surfaceof the wall mounted propaneheater was the most likelyignition source.

It was normal practice at ASCO to

leave the decant water line open atnight to drain to the shed floorthrough a low-point valve. Thisprotected the outside section of theline from damage due to freezingduring cold weather. The openvalve created a potential pathwayfor acetylene to flow from thegenerator into the shed; anenclosed space that was not

Acetylene Leak Path

Sequence of

Operations


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Check Valve

Backflow

The valve depends ongravity and back pressureto seal. No springs areused to assist seating of theplug.

The plug is not effectively

guided and is prone tomisalignment.

The check valve internal

surfaces are susceptible tosolids build up, such asscale or from lime particlesentrained in the recycledwater.

a safe location, in addition to thecheck valve to ensure that backflowof explosive gases does not occur.

The shed was not designed orconstructed for the presence ofacetylene. It was not ventilated,contained a heater with surfaceshot enough to ignite acetylene, andwas equipped with electricalequipment suitable only for generalindustrial service. This createdconditions highly conducive to agas cloud explosion in the event ofan acetylene leak.

Due to the extremely cold weatherand the lack of insulation in theshed, the heater was likely runningor frequently cycling on and off atthe time of the incident. Acetyleneis reported to autoignite14 at 580F,well below the heaters combustionchamber surface temperature of1100F.

Figure 8. Diagram of Rexarc-supplied check valve. Left view shows the plug

open and water flowing. Center shows the plug properly seated. Right showsthe probable failure mode with the plug not fully seated because the guide pin is

hung up.

Lime Shed Design

The electrical equipment in theshed was of general industrialconstruction and was not safe foruse in an environment that couldcontain acetylene. As a result, othersources of ignition could have been

present, such as a spark from anelectric switch, or from anunidentified electrical fault. CSBfound no evidence that any of theelectrical equipment in the shedwas energized at the time of theexplosion. Thus, the heater was themost probable ignition source.

14 Autoignition Temperature (AIT): Thetemperature at which an air/fuel mixturewill spontaneously ignite in a standardizedtest apparatus without exposure to aspark or flame. AIT is measured inaccordance with the American Society forTesting and Materials (ASTM) StandardE659.

The Rexarc Inc. designed andsupplied check valve installed inthe recycled water line (Figures 3B,6) failed to prevent backflow ofacetylene from the generator andout the open drain valve in theshed. Testing performed in placeafter the explosion demonstratedreverse gas flow through the valve,while x-rays taken by OSHA

suggest that the valve guide pinwas hung up on the lower pipenipple (see Figure 8). The checkvalve had been observed to leak onat least one occasion in the past byan ASCO employee, whodisassembled, cleaned, andreassembled the valve.

While check valves are valuable inpreventing backflow in processlines, they should not be solelyrelied on in hazardousapplications. It is good practice toprovide a positive means ofisolation, such as a double-blockvalve arrangement with a bleed to


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The lessons learned from the tragicexplosion at ASCO can helpsimilar facilities avoid damagingincidents in the future. Acetylenefacilities should ensure thefollowing:

Examine lines connected to

acetylene containingequipment and piping to

identify vent and drainpoints that could createhazards in the event of anacetylene backflow or leak.Relocate all such vents anddrains to safe locations,preferably to the outside.

At ASCO, a line that couldpotentially containacetylene drained into anenclosed wooden shed.

Ensure that buildings or

enclosures that couldpotentially containacetylene are suitable foracetylene service. Provideventilation, appropriatelyclassified electricalcomponents, and lowtemperature heatingmethods in accordancewith the National FireProtection Association(NFPA) 51A Standard for

Acetylene CylinderCharging Plant; CurrentEdition.15

The shed in this incidentwas not designed or

constructed in accordancewith NFPA 51A.

Maintain check valves and

block valves in goodworking order throughperiodic inspections andtests.

The check valve and blockvalve that failed at ASCOand allowed backflow

were not on a testing orinspection schedule. Thesingle block valve on therecycle water line, whichwas found closed after theexplosion, leaked duringpost-incident testing.

Provide an engineered,

positive means of isolationin addition to check valves,to ensure that backflow ofexplosive gases cannot

occur.

At ASCO the check valvewas relied upon to preventbackflow.An example ofpositive isolation is adouble-block valvearrangement equippedwith a bleed valve ventingto a safe location.

Confirm that written

operating procedures andchecklists are in place forthe entire operatingprocess, includingauxiliary systems such asrecycled water. Trainoperators on writtenoperating procedures and

15 OSHA has a standard for acetylene,1910.102. However it is out of datebecause it refers to an obsolete CGAstandard. Current industry practice followsNFPA 51A.

The shed did not meet electricalrequirements for areas that could

contain acetylene. The NationalElectric Code (NEC), published bythe National Fire ProtectionAssociation, specifies that electricalequipment meet specificrequirements based on theproperties of the flammablematerials that could be present.Each room, section, or area must beconsidered individually (2002NEC). The NEC has two Divisions(1 and 2) and four Groups (A, B, C,and D) for Class I materials(flammable gases and vapors).NEC defines Division 1 locationsas areas that contain ignitableconcentrations of flammable gas/vapor under normal operatingconditions. Division 2 locationsare defined as areas that handleflammable materials in closedsystems, with ignitableconcentrations present only due tofailures of containment or to theabnormal operation of equipment.

All flammable gases or vapors areassigned to specific groups basedon their explosion characteristics.Acetylene is the only material listedin Group A due to itsextraordinarily explosiveproperties (Table 2). The shedshould have been constructed, andelectrical equipment installed, tomeet NEC Class I, Division 2,Group A requirements.

LESSONS

LEARNED:


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Table 2. Flammable gas/vapor groupings.Group Typical Materials

Acetylene (only member)

Hydrogen, Ethylene Oxide,1,3-Butadiene, and others

Ethylene, Butyl Mercaptan,Acetaldehyde, Carbon Monoxide, andothers

Propane, Methane, Alcohol (ethanol),Gasoline, and others

A

B

C

D

(NFPA 70, Article 500, 500.6 Material Groups)

o Operating instructionsneed to address thesequence for each stepof the operating phase,the operating limits ofthe process, includingthe consequences ofexceeding these limits;relevant safety and

health considerations;and the presence andfunction of any safetysystems.

Operators did not useeither written operatingprocedures or check listsfor start up of the acetylene

require them todemonstrate their ability tocorrectly follow them.

o Procedures and

checklists should becurrent, correct, and ina language that can be

readily understood byoperating personnel.

generator or recycled watersystem at this facility.

Many of these suggested actionsare mandatory for facilities coveredunder OSHA 29 CFR 1910.119,Process Safety Management (PSM)such as the ASCO acetylene

process. These actions areconsidered to be good practice forall facilities handling hazardousmaterials and should beimplemented, even in facilities notcovered under the PSM regulation.

Immediately inform existing

acetylene generator users thatthe check valve did not preventacetylene gas backflow in thisincident. Recommend interimactions be taken to ensure thatRexarc check valves in serviceon acetylene productionequipment will operatereliably. (CSB2006-03-I-NJ-3)

Replace check valves of this orsimilar design supplied byRexarc with valves that willperform more reliably inrecycle water service.(CSB2006-03-I-NJ-4)

Acetylene Services Company

(ASCO)

Improve isolation on acetylenegenerator water lines byincorporating a double-block-and-bleed with a vent to a safelocation, or other isolationmeans of comparableeffectiveness. (CSB2006-03-I-NJ-1)

Recommendations:

Implement an effective ProcessSafety Management program,in accordance with OSHA1910.119. Include writtenoperating procedures andchecklists that are understoodby the workers responsible forusing them. Train workers onthe procedures andperiodically confirm that theyare being properly followed.(CSB2006-03-I-NJ-2)

Update the OSHA 1910.102Acetylene Standard(a. Cylinders, b. Piped Systems,and c. Generators and fillingcylinders) to remove the

existing references tounavailable and obsoleteCompressed Gas AssociationPamphlets (CGA G-1-1966, G1.3-1959, G 1.4-1966). As analternative, considerincorporating by referenceNFPA 51A Standard forAcetylene Cylinder ChargingPlants. (CSB2006-03-I-NJ-5)

Occupational Safety andHealth Administration(OSHA)

Rexarc, Inc.


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Center for Chemical Process Safety(CCPS), 1994. Guidelines forEvaluating the Characteristics ofVapor Cloud Explosions, FlashFires, and BLEVEs, AmericanInstitute of Chemical Engineers(AIChE).

Miller, S.A. 1965. Acetylene, ErnestBen Limited, London.

Mine Safety and Health

Administration (MSHA), 2005.Special Hazards of Acetylene,www.msha.gov.

National Fire Protection Association(NFPA), 2001. Standard forAcetylene Cylinder Charging Plants,NFPA 51A.

Reference

For Further Reading

Babrauskas, Vytenis, 2003. Ignition

Handbook, Fire Science Publishers,Society of Fire ProtectionEngineers.

Baker, Quentin, A., et al., 1997.Recent Developments in the BakerStrehlow VCE AnalysisMethodology, 31st Loss PreventionSymposium, American Institute ofChemical Engineering (AIChE),March 1997.

Baker, Quentin, A., et al., 1994.Vapor Cloud Explosion Analysis,28th Loss Prevention Symposium,American Institute of ChemicalEngineering (AIChE), April,1994.Center for Chemical Process

Safety (CCPS), 1993. Guidelines forSafe Automation of ChemicalProcesses, American Institute ofChemical Engineers (AIChE).

FM Global Property LossPrevention Data Sheets, 2001.Compressed Gas in Cylinders.

Green, Dan W. (ed.), 1984. PerrysChemical Engineers Handbook,6th Edition, McGraw-Hill.

Lees, F. P., 1995. Loss Prevention inthe Process Industries (2ndEdition),Section 12.

National Fire ProtectionAssociation (NFPA), 2004.

Recommended Practice for theClassification of FlammableLiquids, Gases, Vapors and ofHazardous (Classified) Locationsfor Electrical Installations inChemical Process Areas, NFPA497.

Occupational Safety and HealthAdministration (OSHA), 1996.Regulation (Standards 29CFR)Acetylene. 1910.102

Occupational Safety and HealthAdministration (OSHA), 1992.Regulation (Standards 29CFR)Process Safety Management. 1910.119.

Pierorazio, Adrian J., et al., 2005. AnUpdate to the Baker-Strehlow-TangVapor Cloud Explosion PredictionMethodology Flame Speed Table,Process Safety Progress, Vol. 24, No.1, pp. 59-65.

No part of the conclusions, findings, or recommendations of CSB relating to any chemical incident may be admitted as evidence or

used in any action or suit for damages arising out of any matter mentioned in an investigation report (see 42 U.S.C. 7412(r)(6)(G)).CSB makes public its actions and decisions through investigation reports, summary reports, safety bulletins, safetyrecommendations, case studies, incident digests, special technical publications, and statistical reviews. More information about CSBmay be found atwww.csb.gov.

CSB publications may be downloaded atwww.csb.govor obtained by contacting:

The U.S. Chemical Safety and Hazard Investigation Board (CSB) is an independent Federal agency whose mission is to ensure thesafety of workers, the public, and the environment by investigating and preventing chemical incidents. CSB is a scientificinvestigative organization; it is not an enforcement or regulatory body. Established by the Clean Air Act Amendments of 1990, CSBis responsible for determining the root and contributing causes of accidents, issuing safety recommendations, and studying chemicalsafety issues.

U.S. Chemical Safety and Hazard Investigation BoardOffice of Congressional, Public, and Board Affairs2175 K Street NW, Suite 400

Washington, DC 20037-1848(202) 261-7600

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