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1、Acetylene Cylinders,Scope today,Cylinders in firesAcetylene a special problemWhy is UK different?What can be done about it?Research,Cylinders in Fires,All gas cylinders may explode in fires Increasing gas pressure overcomes reducing steel cylinder shell strength at 300oCCooling restores shell streng
2、th and reduces gas pressureBut Acetylene might re-heat,Acetylene is fuel gas of choiceFlame temperature of 3150oC and lighter than airCarbon-Carbon triple bond reactive,not unstable3 x Acetylene reactions of interest in fire Decomposition not spontaneous!-needs 350oCC2H2+HEAT 2C+H2+more HEATSevere s
3、hock to a HOT cylinder?,Acetylene(C2H2),Acetylene Cylinders,Porous monolithic massAcetylene dissolved in a solventsmall cells act as flame arrestorDesigned to stop decompositionSteel heat treatedLow fill pressureBut mass is a heat insulator,Acetylene cylinders have a hard life!the myth of cold impac
4、t effect,Acetylene cylinder testing,Drop testElevated temperature testBackfire testImpact resistance test90g Plastic explosive charge,Impact stability of Acetylene cylinders,Impact resistance testTest protocol requires cylinder to dent by 25%of its diameter.Example shown about 50%Porous mass not dam
5、agedNo damage other than dent itself No cracksNo sharp-edged deformationsNo indication of decomposition,Cold Shock,Gas expert opinion For F+RS,Police and Highways Agency“Mechanical shock alone to a cold Acetylene cylinder,which remains intact and has not been exposed to fire,cannot initiate decompos
6、ition.”,Acetylene vs Propane,Propane AcetyleneCylinder content(Typical)47Kg 8KgGas density 1.55 0.9Flame temp with O2 2500 3200Flammability limits in air 2.2-9.5%2.5-81%Max fill pressure(Bar)10 18Cylinder burst pressure(Bar)67 105Relative BTU yield 1 4Cu Metres Oxygen needed 4 1Special risk BLEVE De
7、compositionCutting?Yes YesBrazing?Yes YesWelding No Yes,UK protocol for DA in Fires is different!,Since 2003/2004Initial 200m hazard zone whilst facts establishedZone reduction based on dynamic risk assessment24 hour precautionary coolingAcetylene cylinder may not be moved or ventedBUT often 200m EX
8、CLUSION zone held for 24hours causes massive disruption!,Why the UK protocol became so?,Death of John Wixey 1987HSL Experiments in 1994Fire Service training contentMyth and folklore!,The London improvement,In 6 years 04 to 09 London had:-543 Cylinder incidents102 incidents really involved Acetylene
9、after all4 DA cylinders exploded ALL IN FIRE,NOT AFTER.NO cylinder re-heated after 1 hour cooling 437 wet tests passed on 140 cylinders all found at ambient temperature!From August 07 to Oct 09:-London F+RS reduced incident frequency from 14 to 25 days and average disruption time from 19 to 2.67 hou
10、rs!Problem solved!why not elsewhere?,BAM Research,German Federal Institute of Materials ScienceWorld renowned acetylene expertsIndependent contract researchcommissioned by BCGA,HSE,DfT,TfLWhat cooling period is required for an Acetylene cylinder to be sure any decomposition is over and cannot re-sta
11、rt?,Screening:Acetylene only,Explosive decomposition occurs at about 350 Cruining the pressure transducer,Conditions as before,but start pressure 10 bar,Research,What conclusions to date?Model works and can be interrogatedMass type makes no differenceNo decomposition until 350cPolymerization occurs
12、300c but is pressure reducingWe assume DA cylinders which explode in fire do so because of decomposition?More likely simple over pressure,research Phase III work,Full scale cylinder tests(at Horstwalde!),Summary,Acetylene cylinders present a special hazardUK procedures have been over-cautiousGood research progressing on heat transferCold impact case provenAcetylene is needed and is safe if stored,transported and used correctly,
