Fuel cells – Understand the hazards, control the risks · PDF fileFuel cells Understand...
Transcript of Fuel cells – Understand the hazards, control the risks · PDF fileFuel cells Understand...
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Health and Safety Executive
Fuel cells Understandthehazards,controltherisks
This is a free-to-download, web-friendly version of HSG243 (First edition, published 2004). This version has been adapted for online use from HSE’s current printed version.
Youcanbuythebookatwww.hsebooks.co.ukandmostgoodbookshops.
ISBN 978 0 7176 2766 0Price £8.50
Thisbookprovidesanintroductiontothehazardsassociatedwithfuelcellsandthefuelsthattheyuse.Itgivessimple,straightforwardtechnicaladvicetomakedesignersandusersmoreawareofthehazardsandthetechniquesavailabletocontroltherisksfromthisrapidlydevelopingtechnology.Italsoprovidesguidancetoenableeveryoneworkingon‘hydrogeneconomy’projectstobemoreawareoftheirresponsibilitytoprotectpeople,andshouldhelptopreventanincidentthatcouldjeopardisetheacceptanceofthesenewtechnologies.
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© Crown copyright 2004
Firstpublished2004
ISBN9780717627660
Allrightsreserved.Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,ortransmittedinanyformorbyanymeans(electronic,mechanical,photocopying,recordingorotherwise)withoutthepriorwrittenpermissionofthecopyrightowner.
Applicationsforreproductionshouldbemadeinwritingto:TheOfficeofPublicSectorInformation,InformationPolicyTeam,Kew,Richmond,SurreyTW94DUore-mail:[email protected]
ThisguidanceisissuedbytheHealthandSafetyExecutive.Followingtheguidanceisnotcompulsoryandyouarefreetotakeotheraction.Butifyoudofollowtheguidanceyouwillnormallybedoingenoughtocomplywiththelaw.Healthandsafetyinspectorsseektosecurecompliancewiththelawandmayrefertothisguidanceasillustratinggoodpractice.
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ContentsIntroduction 4How fuel cells work 5Typesoffuelcell 5Hazards associated with fuel cell installations 8Fireandexplosionhazards 8Electricalhazards 12Controlling the risk from fire and explosion 13Avoidingflammablemixtures 13Avoidingignitionsources 18
Controlling the risk from exposure to harmful chemicals 21
General safety considerations 22Manualhandling 22Training 22Emergencyprocedures 22Legal requirements 23Generallegislation 23Legislationdealingwiththefireandexplosionhazardsoffuelcells 23Legislationdealingwiththeinstallationandmaintenanceoffuelcells 24Appendix 1: Fuel cell types and electrochemistry 26
Appendix 2: Minimum separation distances 27
Glossary 28
References 30
Further information 32
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Introduction1 Sincethestartofthenewmillennium,interestandactivityinhydrogenandfuelcelltechnologyhasbeenacceleratingrapidly.Thoughtheinventionofthefuelcellcanbetracedbacktoworkcarriedoutin1839byWilliamGrove,itwastheworkdonebyNASAthatreallyestablisheditspotential.
2 Theuseoffuelcellstoprovidethein-flightelectricalpowerfortheApollospacecraftinthe1960sinitiatedglobalindustrialresearchanddevelopmentprogrammes.Fuelcelltechnologyhasnowreachedapointwherethesedevicescanbeconsideredviableoptionsformanyapplications,includingcombinedheatandpowersources,back-uppowersupplies,remotelocationelectricityprovisionetc.
3 Thepotentialforpollution-freetransportthroughtheuseoffuelcellshasexcitedpeopleformanyyears.Itnowseemslikelythatfuelcell-poweredbusesand,ultimately,carswillbeafeatureofurbantransportintheforeseeablefuture.
4 Thepurposeofthisguidanceistoprovideanintroductiontothehazardsassociatedwithfuelcellsandthefuelsthattheyuse.Itgivessimple,straightforwardadvicetohelpdesignersandusersbecomemoreawareofthehazardsandunderstandhowtherisksfromthisrapidlydevelopingtechnologycanbeminimised.Everyoneworkingon‘hydrogeneconomy’projectsshouldbeawareoftheirresponsibilitytoprotectpeopleandpreventanincidentthatcouldjeopardisetheacceptanceofthesenewtechnologies.
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How fuel cells work5 Afuelcellisadeviceforharnessingtheenergyliberatedwhenhydrogen,orahydrogen-richfuel,reactswithoxygentoproducewater.Normally,whenhydrogenandoxygenreact,aflameandheatenergyareproduced.Inafuelcellaflameisnotproduced;thereactionproducesonlyelectricityandheat.
Hydrogen+oxygen fuelcell
water+electricity+heat Hydrogen+oxygen
combustion water+heat
6 Insomewaysafuelcellissimilartoabattery.Bothareelectrochemicaldevicesinwhichanelectriccurrentisproducedfromchemicalreactionsthattakeplaceattheelectrodes.Abattery,however,storeselectricityandneedsregularrechargingorreplacement,whileafuelcellcontinuesproducingelectricityaslongasitissuppliedwithfuel.
7 Asinglefuelcellconsistsofanelectrolytesandwichedbetweentwothinporouselectrodes-theanodeandthecathode.Theanodeofthecellisusuallycoatedwithaspecialcatalystwhichsplitseachhydrogenmoleculeintotwoprotons(H+ions)andtwonegativelychargedelectrons.Theelectronsleavetheanodeandprovidetheelectricalcurrentintheexternalcircuittowhichthefuelcellisconnected.Oxygen,usuallyfromair,isfedtothecathodeofthecellwhereitreactswithprotonsandtheelectronsreturningfromtheexternalcircuit,toproducewater.
Types of fuel cell
8 Althoughthereactionbetweenhydrogenandoxygenisthebasisofalmostallfuelcells,themannerinwhichthisreactionisharnessedvariesconsiderably.Thewaythecellworksisheavilydependentuponthenatureoftheelectrolyte.Thecharacteristicsandhalf-cellreactionsofthemostcommontypesoffuelcellaresummarisedinAppendix1.
9 Fuelcellscanbelooselygroupedintothosewithacidicelectrolytes,thosewheretheelectrolyteisalkaline,andthosethatoperateathightemperatures.
Acidic electrolyte fuel cells: PEMFCs and PAFCs 10Successfulexamplesofacidicelectrolytefuelcellsaretheprotonexchangemembraneorpolymerelectrolytemembrane(PEM)andthephosphoricacid(PAFC)fuelcell.Inbothofthesecellstheprotonsproducedattheanodemovethroughtheelectrolytetothecathodewherewaterisproducedfromtheirreactionwithoxygenandthereturningelectrons.
11TheelectrolyteinthePEMcellisaspecialfluorocarbonpolymerthatisimpervioustohydrogengasandelectronsbutwillreadilyallowthepassageofprotonsfromtheanodetothecathode.InthePAFCtheelectrolyteisathinfilmofphosphoricacidheldinafluorocarbon-bondedmatrix.TheelectrodesofbothPEMandPAFCunitsareusuallymadefromporouscarbonimpregnatedwithplatinum.Inbothofthesedevicestheelectrolyteisnothickerthanafewsheetsofpaper,allowingalargenumberofcellstobearrangedinseriestoproduceacellstack.
g
g
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12PEMandPAFCdevicesarecompactandcangeneratequitealotofpowerfromarelativelysmallunit.PEMcellsarecurrentlybeingusedinlargetransportvehiclessuchasbusesandtractionunits.PAFCunitsareoftenassembledintoverylargestacksandagreatmanyPAFCassemblieswithelectricalpoweroutputsinexcessof200kWareinusearoundtheworldforstationarypowergeneration.Thehightoleranceoftheseunitstoimpuritiessuchascarbonmonoxideandcarbondioxideenablesthemtoberunonhydrogengeneratedfromnaturalgasorotherhydrocarbonsusingareformer.
Alkaline electrolyte fuel cells: AFCs13Thesecellsoftenuseanaqueoussolutionofpotassiumhydroxideastheelectrolyteandoperateatquitehightemperatures,100–250ºC.Thisallowsthemtousenon-preciousmetalcatalystsattheelectrodes.However,thesepotentialadvantagesareoffsetbytheneedforveryhigh-purityhydrogenfeed.Traceamountsofcarbondioxidereactwiththeelectrolyteandcauseirreparabledamagetothecell.
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14AFCsdifferconsiderablyinthewayinwhichtheygenerateelectricity.Oxygen,fromairsuppliedtothecell,reactswithwateratthecathodeofthecell,producinghydroxideions.Thesemovetowardstheanodewheretheircatalysedreactionwithhydrogenproduceswaterandliberateselectronsintotheexternalcircuit.Consequently,inthesecellswaterisproducedattheanoderatherthanthecathode,asisthecasewithotherfuelcells.
High-temperature fuel cells: MCFCs and SOFCs15Moltencarbonatefuelcells(MCFCs)operateattemperaturesaround650ºCanduseamoltenmetalcarbonatesuspendedinaporousceramicmatrixfortheelectrolyte.Atthecathode,oxygenandcarbondioxideareconvertedtocarbonateions,whichthenmovethroughtheelectrolytetotheanodeandreactwithhydrogentoproducecarbondioxideandwater.
16Thehighoperatingtemperatureofthesecellsenableslessexpensivecatalyststobeusedandtheydonotrequireaseparatereformer.Suitablehydrocarbonfuelscanbefeddirectlyintothecellwhereinternalreformingtohydrogentakesplace.Moltencarbonatefuelcellsarenotdamagedbythepresenceofcarbondioxideinthefeedgases,allowingawiderangeoffuelstobeused.
17Solidoxidefuelcells(SOFCs)useahard,non-porousceramicmaterialastheelectrolyte.Theveryhighoperatingtemperature,around1000ºC,enablesthesecellstocarryoutinternalreformingofsuitablehydrocarbonfuelsandtheuseoflessexpensivecatalysts.SOFCshavequitegoodresistancetopoisoningbysulphurorcarbonmonoxide,enablingawiderangeoffuelstobeused.
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Hazards associated with fuel cell installations18Thissectiondiscussesthehazardsofthesubstancesandtechnologyassociatedwithfuelcells.Everyoneinvolvedinthedesign,installation,useandmaintenanceoffuelcellsshouldhaveanappropriateunderstandingofthesehazards.Withoutthisknowledgeitisnotpossibletocarryoutasuitableriskassessment.
19Inmanysituationsthemajorhazardsassociatedwithafuelcellinstallationmaybeputintothefollowingcategories:
n dangeroussubstances:1
– fireandexplosion;– harmfuleffectsofexposure;
n electricshock;n generalsafetyhazards,forexamplemanualhandling.
20Thisguidanceconcentratesoncontrollingtheriskfromfireandexplosion,particularlywhenhydrogenisthefuel.Generalguidancedescribinghowriskintheworkplacefromtheothersignificanthazardsshouldbecontrolledisalreadyavailable.2
Fire and explosion hazards
Fuels21Allthefuelssuitableforuseincellsreadilycatchfireandsopresentasignificantfireandexplosionhazard.Materialssuchasthesearecalled‘dangeroussubstances’undertheDangerousSubstancesandExplosiveAtmospheresRegulations2002(DSEAR).1TheseRegulationsintroducenewdutieswhichincludeavoidingsourcesofignitionandthereleaseofdangeroussubstancesintotheworkplace.
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22DSEARalsoreinforcesthegeneralrequirementforemployersundertheManagementofHealthandSafetyatWorkRegulations1999toidentifythesignificanthazardspresentintheworkplaceandtocarryoutasuitableandsufficientassessmentoftheriskfromthosehazards.2Appropriatemeasuresmustthenbetakentoreducethoseriskstoanacceptablelevelthatisas low as is reasonably practicable.
23Allfuels,suchashydrogen,petrol,methane,LPGetc,willcatchfireandmayproduceanexplosion.Beforeanexplosioncanoccur,aflammablemixtureofthefuelandairmustformandasourceofignitionmustbepresenttoigniteit.
24Petrolandmethanearefuelsroutinelyusedbymillionsofpeopleeveryday.Mostusersareawareofthepropertiesofthesefuelsandwhatneedstobedonetohandlethemsafely.Thepropertiesofhydrogenareoftennotwidelyappreciatedandthiscanresultintherisknotbeingproperlycontrolled.
25Thehazardsofhydrogenarediscussedinsomedetailbelow,followedbyabriefsummaryoftheimportantdifferentoradditionalhazardsofotherfuels.Someofthewaysinwhichsourcesofignition,theotherrequirementforanexplosion,maybeavoidedarediscussedlater(seeparagraphs82–90).
Hazardous properties of hydrogen and its storage26Hydrogenhassomeunusualproperties.Ifthesearenotappreciatedandappropriatemeasuresnottaken,thenthelikelihoodofhydrogenescapingandafireorexplosionoccurringmaybegreaterthanwithmanyotherfuels.Someoftheimportantpropertiesofhydrogenthatmaycontributetowardsthisare:
n verywideflammabilityrange;n verylowignitionenergy;n possibilityofdetonation;n lowviscosity;n highdiffusivity;n verymuchlighterthanair;n causestheembrittlementofsomemetals;n condensationofoxygen-richliquidaironcryogenicstoragesystems.
27Hydrogenisagasthatcatchesfireveryeasily.Itburnswithaflamethatisalmostinvisibleandreadilyformsanexplosivemixturewithair.Therangeofhydrogen/airconcentrationsthatwillexplodeisextremelywide,muchwiderthanalmostanyotherfuel.Mixturescontainingfromaslittleas4%v/vhydrogen,whichisthelowerexplosionlimit(LEL),uptoasmuchas75%v/v,theupperexplosionlimit(UEL),willreadilyigniteandexplode.3
28Ifaflammablemixtureofhydrogenandairisallowedtoform,thelikelihoodofanexplosionoccurringisveryhigh.Thisisbecausetheenergynecessarytoinitiateahydrogen/airexplosionisverysmall.Theignitionenergyfora2:1hydrogen/oxygenmixtureisonlyabout0.02mJ.Thisislessthanonetenththatofothercommonfuelssuchasmethane,LPGorpetrol.Evenverysmallsparks,suchasthoseproducedbywearingcertaintypesofclothing,arecapableofignitinghydrogen/airmixturesandcausinganexplosion.4
29Asignificantdifferencebetweenhydrogenandothercommonflammablefuelsisthatforthebulk(18–69%v/vhydrogen)ofitsflammablerangethereisapossibilitythatahydrogen/airmixtureinaconfinedandheavilycongestedsituationmaydetonate.4,5
30Detonationscausemuchmoredamageandarefarmoredangerousthanordinaryexplosions(deflagrations).Consequently,theriskfromdetonationshould
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alwaysbeconsideredintheriskassessmentofsystemshandlingorstoringhydrogen.
31Hydrogengashasaverylowviscosityandsoitisverydifficulttopreventhydrogensystemsfromdevelopingleaks.Pipeworkthatwas‘leak-tight’whenpressure-testedwithnitrogenwilloftenbefoundtoleakprofuselywhenusedonhydrogenduty.Thispropertyincreasesthelikelihoodofaflammablemixtureforming.
32Hydrogenisverymuchlighterthanair,muchmoresothannaturalgas(methane),andisalsoverydiffusive.Whenitescapesitmovesupwardsveryrapidly.Ifaleakoccursinanopenorwell-ventilatedareaitsdiffusivityandbuoyancywillhelptoreducethelikelihoodofaflammablemixtureforminginthevicinityoftheleak.
33However,whenleaksoccurwithinpoorlyventilatedorenclosedareas,theconcentrationofhydrogeninthehigherregionsmayrapidlyreachdangerouslevels.Ifunprotectedelectricalequipmentorothersourcesofignitionarepresent,theriskfromexplosionwillbeconsiderable.
34Almostallhydrogeniscurrentlystoredinhigh-pressurecylinders.Thecryogenicstorageofliquidhydrogenforfuelcellusemay,however,becomemorewidespreadinthefuture.Thehazardsfromtheverylowstoragetemperaturesusedforliquidhydrogen,around-250ºC,includeseverecold-burnsandthecondensationofoxygen-enrichedliquidaironunprotectedpipework.
35Liquidhydrogenboilsat-253ºCatatmosphericpressureandsohydrogenleakingfromcryogenicstoragewillbeverycoldandmaybeheavierthanair.Asaresult,leakinggaswilloftensinkinitially,formingaflammableatmosphereatlowlevel,beforewarmingup,becomingbuoyantandrising.Thisisinmarkedcontrasttoaleakofcompressedhydrogenwheretheaccumulationofaflammableconcentrationofhydrogenisalwaysathighlevel.
36Researchanddevelopmentworkonthestorageofhydrogeninmetalhydrideshasbeeninprogressformanyyears.Therearetwomaintypesofhydridestoragesystem.‘Traditionalhydrides’usethereversibleabsorptionofhydrogenintothemolecularlatticeoftransitionmetals.6Thefinelydividedmetaliscontainedinsideapressurevesselandisoftenaflammableorpyrophoricsolid.
37‘Complexhydrides’storehydrogenthroughreversiblereactionsinvolvingsodiumaluminiumhydrideandsimilarmaterials.7Thesematerialsareflammablesolidsthatalsoreactvigorouslywithwatertoproducehydrogenandacorrosiveaqueoussolution.
38Thepressureofhydrogeninthesetypesofstoragesystemdependsonstoragetemperatureandthestateofcharge/discharge,butmayoftenbeinexcessof10barg.
The hazards of fuels other than hydrogen39Manycellsusehydrogenproducedfromhydrocarbonfuelsusingreformer-typetechnologylocatednearthefuelcellstack.Somehigh-temperaturefuelcellsareabletorunonsuitablehydrocarbonfuelswithoutaseparatereformer.
40Thereactionsthattakeplacewithinthereformer,orwithinhigh-temperaturefuelcells,convertthehydrocarbonfuelintohydrogenforuseinthecellandcarbondioxide,whichisvented.Useappropriatemeasures,suchascontainmentandventilation,toensurethatthecarbondioxideeffluentstreamfromlargercellsiseffectivelydischargedanddoesnotproduceanasphyxiationrisk.
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41Naturalgas(methane)islighterthanairandwilltendtodiffuseupwards,thoughmuchmoreslowlythanhydrogen.Theexplosionlimitsfornaturalgas(5–15%v/v)arealsomuchnarrowerthanthoseforhydrogen.8Considerthecharacteristicsofbothfuelsfullywhendesigningandoperatingdualfuelsystems.Thepipeworkandequipmentusedtosupplynaturalgastothefuelcellshouldbesuitableandbedesignedtoanappropriatestandard.9
42LPGvapourisconsiderablyheavierthanair,especiallywhencold,forexamplewhentakendirectlyfromaliquidstoragevessel.Intheeventofaleak,LPGvapourwillusuallypercolatedownwardsandmayaccumulateonthefloororinlow-lyingsumps,rapidlyproducingaflammableatmosphere.Mixturescontaining2–10%v/vLPGinairwillreadilyigniteandexplode.10ThesignificantdifferencesinthebuoyancyanddispersioncharacteristicsofthetwofuelsshouldbecarefullyconsideredinsystemswhereLPGandhydrogenmaybothbepresent.ThepipeworkandequipmentusedtostoreandsupplyLPGtothefuelcellshouldbesuitableandbedesignedtoanappropriatestandard.9
43Methanolcanbeuseddirectlybysometypesoffuelcell.Thisfuelhassomehazardsthatdemandparticularattention.Inadditiontobeingahighlyflammableliquid,methanolisalsotoxicbyinhalation,ingestionand,notably,byskinabsorption.11Appropriateprecautionssuchascontainmentandventilationshouldbetakentopreventspillagesandtheaccumulationofhazardousmethanol/airmixtureswheneveritisused.
44Ignitionsourcesshouldbeavoidedthroughthemeasuresdescribedlater(seeparagraphs82–90)wherethereisthepotentialforflammablemethanol/airmixturestoform.12,13MoredetailedadviceontheseissuesiscontainedinSafe use and handling of flammable liquids.14
Sources of ignition45Aflammablefuel/airmixturewillnotexplodeunlessitisexposedtoasufficientlypowerfulignitionsource.Commonsourcesofignitioninclude:
n nakedflamesandsparksfromwelding,burningorgrinding;n electrostaticsparksfrompoorlyearthedornon-conductivepipework;n electricalsparksfrommotors,switches,relaysormobilephones;n sparksfrommechanicalimpacts;n hotsurfaces,forexamplebearings.
46FurtherguidanceonsourcesofignitionmaybefoundinSafe use and handling of flammable liquids.14
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Electrical hazards
47Electricshockcanbealife-threateninghazardandmustnotbeoverlookedinthedesign,operationandmaintenanceofthefuelcellanditsassociatedequipment.15
48Electricalhazardsusuallyarisefromtwodistinctareaswithinfuelcellinstallations-thenormal240or415voltmainsa.c.supplyintotheareaandthed.c.electricaloutputofthefuelcellstack.Withlargerunitstheremaybeathirdarea-thea.c.outputofaninverterconnectedtothefuelcell.
49Thevoltageandcurrentproducedbyeachelementinthestackisusuallyquitesmall;however,thetotaloutputfromthestackmaybeoftheorderof200–400voltsandlargeelectricalcurrentsareoftenavailable.Theelectricaloutputfromquitemodestfuelcellscanbelifethreatening.
50Largefuelcellstacksmayalsoprovidelargecurrentsaswellaslethalvoltages.Ifametalobjectisinadvertentlyplacedacrosstheoutputbusbarsofsuchacellthena‘shortcircuit’willbeproducedandalargeelectricalcurrentwillflowthroughtheobject.Thisislikelytogethotveryquicklyandmayproduceashowerofsparks.
51Theelectricalequipmentassociatedwiththefuelcellshouldbedesignedandinstalledtoanappropriatestandard,andsuitablearrangementsshouldbeinplacetoensurethatonlycompetentpersonnelareabletogainaccesstotheequipment.
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Controlling the risk from fire and explosion52Considerthefollowingapproacheswhendevelopingthestrategytominimisetheriskfromfireandexplosion:
n investigatethereplacementofhydrogenwithalesshazardousfuel;n avoidtheformationofflammablemixtures;n avoidsourcesofignition;n usesuppression,containmentormitigationoftheexplosion.
53Inmanysituationsavoidingflammableatmospheresandsourcesofignitionwillbethemostusefulapproach.
Avoiding flammable mixtures
54Thelikelihoodofaflammableatmospherebeingproducedmaybereducedusingthefollowingtechniques:
n containment;n segregation;n separation;n ventilation.
Containment55Measurestopreventthereleaseofdangeroussubstancesshouldbegiventhehighestpriority.Ifyoucanpreventarelease,aflammableatmospherecannotformandtheriskfromexplosioniseliminated.
56Minimisethelikelihoodofaleakoccurringbyusinghigh-qualityengineering.Payparticularattentiontothedesign,operationandmaintenanceofthehydrogen-handlingequipment.Inthiswaythelikelihoodandsizeofanypotentialleakcanbeminimised,leadingtoagreatlyreducedriskfromexplosion.5Byconsideringtheguidancebelowyouwillbefollowinggoodpractice:
n ensurethatthestorageequipment,pipeworkandconnectionsconformto anapprovedstandardforhydrogenequipment;3
n ensurethatmaintenanceworkiseffectivelycontrolledandisonlycarriedout byauthorisedcompetentpeople;
n minimisethefrequencywithwhichconnectionsaremadeandbroken;n useappropriaterefillablestationarystorageratherthanregularlyreplacing
largenumbersofseparatelyconnectedcylinders;n usetheminimumlengthandsizeofpipeworkthatisappropriate;n minimisethenumberofjointsbyusingcontinuouslengthsofpipework
whereverpracticable;n usefusionjointing(weldingorbrazing)orflanged/threadedconnectorsto
joinpipework;n ensurethatthesystemisleak-testedbeforeuseinamannerappropriatefor
hydrogensystems;3
n carryoutappropriateinspectionsofthesystematsuitableregularintervals andrecordtheresults;
n reviewtheoperationandmaintenancehistoryatsuitableintervals.
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57Whenhigh-pressurestorageisuseditshouldbedesignedandbuilttoanappropriatedesigncodeorstandardandlocatedinasecureopen-aircompound.3
Themeasuresusedtopreventunauthorisedaccess,vandalismandimpactfromvehiclesshouldbeappropriatetothelocation.
58Indoorstorageofcompressedhydrogenisnotrecommended.Itmaybepermissibleinsingle-storey,purpose-designedbuildings,providedappropriatesafetymeasures,suchaseffectiveventilation,fire-resistantconstructionandexplosionreliefaretakenandtheriskshavebeenreducedaslowasisreasonablypracticable.3Inmostsituations,however,indoorstorageshouldusuallybeconsideredinappropriateifanoutdoorlocationispracticable.
59 Cryogenichydrogenstorageinstallationsshouldbeconstructedtoanappropriatecodeandlocatedinasuitableopen-airpositionandnotwithinanoccupiedbuilding.16Low-temperaturestorageinstallationsshouldincorporatesuitablemeasurestopreventoxygen-richliquidair,apowerfuloxidisingagent,fromcondensingonuninsulatedsurfacesexposedtoliquidhydrogentemperatures.16Toavoidtheriskfromfire,potentiallyflammablematerials,includingasphaltandtarmac,shouldnotbepresentbeneathpipeworkwherecondensationmayoccur.
60Useonlyappropriatepipeworkandfittingsforthesupplyofhydrogen.3,17Cupro-nickelandstainlesssteelarepreferredmaterialsforhigh-pressurepipeworkwhereascoppercanbeusedforlowerpressures.Allpipeworkjointsshouldbebrazedorwelded.Flangedorscrewedjointsareacceptablebutavoidusingthemifpossible.
61Compressionjointsaregenerallynotrecommendedforuseonhydrogensystemsasitisdifficulttoachieveandmaintaintheseina‘leak-free’condition.Wheretheiruseisconsideredessential,suchasonsmall-borepipework,theyshouldbesuitableforthedutyandusedinstrictaccordancewiththemanufacturer’sinstructions.
Segregation and separation62Arrangingthecomponentpartsofaninstallationinanappropriatewaycansignificantlyreducethelikelihoodofanexplosion.Theriskfromexplosionwillusuallybemuchlowerwhenthehydrogen-handlingequipmentiswellseparatedfromelectricalequipmentorotherignitionsources.
63Alwaystakeintoaccountthetendencyofhydrogentomigraterapidlyupwards.Itsbuoyancyshouldbefullyconsideredandusedtoreducetheriskfromfireandexplosionwhendesigningorarrangingthecomponentsofafuelcellorinstallation.Thiscanbedonethroughthefollowingmeasures:
n segregateandphysicallyseparateequipmentforhandlinghydrogenfrom foreseeablesourcesofignition;
n separatethehydrogenstorageareafromthefuelcellandthefuelcellfrom equipmentusingitselectricaloutput;
n locateanypotentialsourcesofignitionwellbelowanyequipmentfromwhichhydrogenmayleak;
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n avoidlocatingpotentialsourcesofignition,suchasnon-flameproofelectricallightfittings,immediatelybelowhorizontalbulkheadsorimperviousceilingsunderwhichhydrogenmayaccumulate;
n ensurethatanyarea,enclosureorhousingetc,intowhichhydrogenmayleak,isdesignedtopreventthegasbecomingtrappedandisequippedwitheffectivehigh-andlow-levelventilation;
n donotlocatesystemsusingorstoringhydrogenbeneathunprotectedelectricalequipmentorhigh-voltagepowerlines;3
n usegas-tightcompartmentsorbulkheadsandventilationtoreducethelikelihoodofleakinghydrogenreachingpotentialsourcesofignition.
Separation distances64Recommendedseparationdistancesaretheminimumdistancesconsiderednecessarytomitigatetheeffectsoflikelyforeseeableeventsandpreventaminorincidentescalatingintoamajorone.18Theyareusedtoseparatedifferenthazards,suchashigh-pressurehydrogenstoragefromanignitionsource,orahazardfromvulnerableobjectsorpeople.
65Therecommendeddistancesareintendedtogivepeopleandequipmentasuitabledegreeofprotectionfromaforeseeableeventontheinstallation,suchasahydrogenleakandsubsequentjetfire.Theseparationthattheyprovideshouldensurethattherisktopeoplefromheatradiationorfromflameimpingementontootherflammablematerialsislow.Separationdistancesarealsocalculatedtogiveprotectiontotheinstallationfromoff-siteeventssuchasimpactfromvehiclesormachinery,releasesofflammablematerials,uncontrolledignitionsourcesortheradianteffectsofoff-sitefiresetc.
66Theuseofestablishedseparationdistancesaroundequipmenthandlingorstoringhydrogenorotherdangeroussubstanceshastraditionallybeenconsidered
4 8
4
8
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afundamentalrequirementforthedesignofasafeinstallation.Youshouldmeasurethehorizontalseparationdistancesrequiredfromthosepointsinthesystemwhere,inthecourseofoperation,anescapeofhydrogenmayoccur.Consultthemostrecentversionofanappropriatecodeforadditionalinformationontheappropriateuseofseparationdistances.
67IncircumstanceswhereitisnotpracticabletousetheminimumseparationdistancessummarisedinAppendix2,anacceptablesituationmaybeachievedthroughtheuseofsuitablefire-resistantbarriersorotherriskreductiontechniques.3
68Theremaybesituationswheretherecommendeddistancesareconsideredinappropriate,forexamplewhentheoperatingpressureofthesystemislow.Wheretherecommendedseparationdistancesarenotemployed,theonusisonthedutyholdertodemonstratethroughasuitableassessmentthattheriskisacceptableandhasbeenreducedaslowasisreasonablypracticable.
Ventilation69Ventilationisaveryeffectivewayofloweringtheriskfromexplosion.Whentheconcentrationoffuelinafuel/airmixtureisreducedbelowthelowerexplosionlimit(LEL)anexplosioncannotoccur.
70DSEAR1requiresemployerstoprovideadequateventilationtoensurethatanyforeseeablereleaseofadangeroussubstancedoesnotaccumulatetoaconcentrationthataffectsthesafetyofpeople.Usethefollowingprinciplestoensurethateffectiveventilationisprovided:
n locatehydrogenstorage/handlingequipmentoutside;n estimatethemaximumforeseeableleakrate;n provideadequatehighandlowventilation;n bewareoflowceilings,canopies,coversandroofs;n ensurethedilutionairisdrawnfromasafeplace;n ensureventsandpurgesdischargetoasafeplace;n usecomputationalfluiddynamics(CFD)forcomplexventilationrequirements.
71Thosepartsofthefuelcellinstallationthathandlehydrogenorotherdangeroussubstancesshouldbelocatedintheopenair.Wherethisisnotdone,theonusisonthedutyholdertojustifythatitwasnotreasonablypracticabletouseanoutdoorlocationandthattheriskfromtheequipmentinthechosenlocationisacceptable.
72Whenusinganoutdoorlocationforhydrogenstorageitisstillessentialtoensurethatefficientdilutionofanyleakagewilltakeplace.Followtheguidelinesbelowwhendesigningoutdoorstorageandsupplysystemstoensurethatthelikelihoodofaflammableatmosphereaccumulatingisminimised:
n avoidtheuseoflow,imperviousroofs,canopiesorbulkheads;n avoidlocationsbeloweavesorotheroverhangingstructures;n useasuitable,non-combustiblesecurityfenceratherthanawall;n ensureadequatehigh-andlow-levelventilationapertureswhereawallaround
thestoragesystemisunavoidable.
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73Wheneverhydrogenisusedorstoredinanenclosedorpartiallyenclosedarea,effectiveventilationmustbeusedtopreventtheformationofanexplosiveatmosphere.Thesizeofanyforeseeableleakintotheareashouldbeestimatedandusedasabasisforcalculatingtheventilationrequirements.Theseshouldbesufficienttoensurethattheconcentrationofhydrogeninsideanyoccupiedareaisnormallymaintainedbelow10%LELwithoccasionaltemporaryincreasesupto25%LEL.Insideanunoccupiedenclosure,fuelcellhousingorcompartment,theventilationshouldensurethattheconcentrationcannotexceed1.0%v/v(25%LEL).
74Insituationswhereeffectivemonitoringofthehydrogenconcentrationisprovidedandinterlockedintoasuitableshutdownsystemitmaybeacceptabletooperatecabinetsandhousingatupto2%v/vhydrogen.Consultrelevantguidancetoensurethatthealarm/shutdownarrangementsaresuitablefortheinstallation.19
75Useappropriatemechanicalmeanswhenevernaturalventilationcannotprovidethenecessarydilution.Inthesesituationsasuitablemonitoringandshutdownsystemshouldensurethatthesupplyofhydrogentotheareaissafelyisolatedintheeventofafailureoftheventilationequipmentorwhenabuild-upofhydrogenisdetected.
76Thedesignofanymechanicalventilationsystemmustnotinvolvethelocationofthefanmotorwithinapotentiallyexplosiveairstream.Positionventilationfans
4
8
4
8
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neartheairinletandusethemtoforcecleanairthroughtheenclosure.Donotsitethemneartheoutletorusethemtodrawpotentiallycontaminatedairthroughthesystem.
77Thecooling/air-supplyfanorcompressorpresentinmanyfuelcellmodulesmaysometimesbesuitabletoprovideeffectiveventilation.Wherethisapproachisused,theairmustbedrawnfromasafeplaceandthedirectionoftheforcedairflowshouldbecompatiblewiththeexpectedmovementofanyhydrogenreleaseasaresultofbuoyancy,thermaleffectsetc.
78Thetendencyforhydrogentorisefromleaksandaccumulateagainstimperviousceilingsandhigh-levelbulkheadshasbeenidentifiedpreviouslyasasignificanthazard.Thelocationandtypeofelectricalequipmentusedinareaswherehydrogenmaybepresentandthedesignofventilationarrangementsshouldrecognisethishazardandbeappropriate.
79Internalpartitionsandbulkheadsmaybeusedeffectivelytoseparateignitionsourcesfrompotentialsitesofhydrogenleakage.Differentialpressurisationofseparatecompartmentsmaybeusedtopreventtheingressofhydrogenintoareascontainingsourcesofignition.Wherethistechniqueisused,thepressurisationairshouldbedrawnfromanddischargedtoasafeplace.Installanappropriatealarm/shutdownsystemtodetectandrespondtoanylossofventilationordifferentialpressure.
80Thedilutionairflowandthenumberandlocationofflammableatmospheredetectorsshouldbeappropriateincomplexsystemsorcongestedlocations.Anappropriatemodellingtechniqueshouldbeusedinthesesituationstoensurethatpocketsofflammablemixturewillnotaccumulateandremainundetected.
81Insituationswhereotherfuelssuchasmethane,LPGetcarepresent,inadditiontohydrogen,takeintoaccounttheirdifferentdensitiesanddiffusivitiestoensurethattheventilationarrangementsprovidedareappropriate.
Avoiding ignition sources
82Aflammablemixturewillnotexplodeifasourceofignitionisabsent.Althoughitisextremelydifficulttoeliminateallsourcesofignition,avoidingignitionsourcesshouldbeanimportantpartofyouroverallriskreductionstrategy.Itmustbeusedinallareaswhereapotentiallyexplosiveatmospheremaybepresent.Thefollowingtechniquesshouldbeincludedinyourapproachtoavoidingignitionsources:
n carryoutahazardousareaassessment;n identifythenatureandextentofhazardouszones;n usesuitablesignstodenotetheboundariesofhazardouszones;n locateelectricalequipmentinnon-hazardousareas;n useappropriatelyclassifiedequipmentinhazardousareas;n usecontinuitybonding,earthingandanti-staticclothingtoavoidstatic;n controlhotwork,vehicles,smokingandtheuseofmobilephones;n providelightningprotectionwhereappropriate.
83Whenplanningafuelcellprojectitisimportanttoconsiderwhetheritwillintroducenewfireandexplosionhazardsintoanareawherepreviouslythesewereabsentorwhethertheproposedlocationisalreadyahazardousarea.Inotherwords,doestheneedtocontrolignitionsourcesresultfromthepossibilityofahydrogenleakfromthenewfuelcellinstallationordoesthefuelcellrepresenttheintroductionofapotentialsourceofignitionintoanexistinghazardousarea?
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84Whereapotentiallyexplosiveatmospheremaybepresentintheworkplace,DSEAR1requiresemployerstoassessandidentifythoseareasinwhichignitionsourcesneedtobecontrolled.TheareaswhereexplosiveatmospherescouldbeformedmustbeidentifiedanddesignatedashazardouszonesaccordingtotheprinciplesofHazardousAreaClassification.12,13
85Theresultsfromtheclassificationexerciseshouldbeusedtoensurethattheappropriatecategoryofequipmentisusedinthefuelcellinstallationandthatonlysuitableequipmentispresentinthevicinityofthenewinstallation.
86Forsituationswherehydrogenand/orotherflammablegasesorliquidsmaybepresent,thefollowingclassificationsshouldbeusedwhereappropriate:
n Zone0:Anareainwhichanexplosiveatmosphereispresentcontinuouslyorforlongperiods.Onlycategory1equipmentshouldbeusedintheseareas;
n Zone1:Anareawhereanexplosiveatmosphereislikelytooccurduringnormaloperation.Onlycategory1or2equipmentshouldbeusedintheseareas;
n Zone2:Anareawhereanexplosiveatmosphereisnotlikelytooccurduringnormaloperationand,ifitdoesoccur,islikelytodosoinfrequentlyandwillonlylastforashortperiod.Onlycategory1,2or3equipmentshouldbeusedintheseareas.
87Electricalequipmentappropriateforuseinthedifferentareasoftheworkplaceshouldbedeterminedoncethehazardousareashavebeenidentifiedandclassified.12,13Whenselectingelectricalequipmentforuseinhazardousareas,specifythetemperatureclassandtheapparatusgroupappropriateforthetypeofflammableatmospherelikelytobepresent.
88Youshouldusetheresultsofthehazardousareaclassificationexercisetoensurethatsuitablecontrolsareplacedonallotherforeseeableignitionsources.Theseshouldincludehotwork,smoking,vehicles,mechanicalequipment,mobilephonesandworkclothing.
89Itisimportantnottooverlookthefuelcellitselfwhenensuringthatonlysuitableequipmentispresentinhazardousareas.Whendesigningandconstructingthefuelcellyoushouldconsiderthefollowingpoints:
n ensurethatanyfuelcelllikelytobeusedwhereapotentiallyexplosiveatmospheremaybepresent,ieahazardousarea,complieswiththeATEX(ECDirective94/9/EC)RegulationsandBSEN60079;20,12
n ensurethattheelectricalcomponents,connectors,materialsetcemployedaresuitablefortheirintendeduseandenvironment;
n locatetheelectrical/electroniccomponentsofthefuelcellbelowanyforeseeablesourcesofhydrogenleakage;
n usesuitablegas-tightbarrierstoseparateelectrical/electronicequipmentfromareaswherehydrogenmaybepresent;
n useappropriateventilationtopreventtheformationofpotentiallyexplosivemixtures;
n theuseofexplosion-resistantequipmentorexplosionreliefmaybeappropriateincertainsituations;
n usetheguidanceavailableinrecognisedstandardssuchasIEC62282toavoidbasicdesignflaws.21
90Staticelectricitysparkshaveoftenbeenthesourceofignitioninexplosionsofflammablehydrogen/airmixtures.Effectivearrangementsshouldbeinplacetopreventthebuild-upofstaticchargesthatmayleadtoanincendivedischarge.Considersuitablemeasurestoreducetheriskfromstaticelectricity.Thesemayinclude:
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n ensuringthatallpipeworkisconductiveandhaseffectiveelectricalcontinuity,especiallyacrossmechanicaljointssuchasflanges;
n ensuringthatallpipeworkandequipmentiseffectivelyearthed;n carryingoutanddocumentingappropriateearthing/continuitychecks;n wearingantistaticclothingandfootwearinhazardousareas;n providingappropriateprotectionagainsttheriskfromlightningwhendesigning
outdoorfuelcellorhydrogenstoragefacilities.3
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Controlling the risk from exposure to harmful chemicals91Assessallthechemicalsassociatedwiththefuelcelltoidentifyifanyofthemposearisktohealth.Somefuelcellsmaycontainharmful,corrosiveorirritantchemicalsintheirelectrolytes.However,thesechemicalsaregenerallyinaclosedsystemandposenothreattohealthfromexposureduringnormaluse.Noadditionstoorreplacementoftheelectrolytearenormallyanticipated.Theremaybesomeriskofexposuretothesesubstancesifthefuelcellbecomesdamagedorduringdisposal.Havesuitableproceduresinplacetosafeguardpersonnelfromtheharmfuleffectsofspecificchemicalsandfromthepotentialforsuchanexposure.
92Methanol/airmixturesarehazardoustohealthaswellasbeingpotentiallyexplosive.Consequently,youshoulddoasuitableandsufficientassessmentoftherisktohealthundertheControlofSubstancesHazardoustoHealthRegulations(COSHH)andidentifythestepsthatneedtobetakentopreventoradequatelycontrolexposure.22Tousemethanolsafelytheserisksmustbetakenintoaccountandsuitablecontrolmeasuresincorporatedintoequipmentandprocedures.
93Theconcentrationofmethanolinairconsideredtobeharmfultohealth(TWA200ppm)isverymuchlowerthanonewhichisflammable(LEL6%v/v).11Consequently,forlargeenclosureswhichpeoplemayenter,theventilationarrangementsetcshouldbeappropriatetoensurethataharmful(tohealth)atmospheredoesnotaccumulate.Thesearrangementsshouldeasilyensurethattheriskofexplosioniseliminated.
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General safety considerations94Itisimportantnottoforgetthebasicaspectsofasafesystemofworkwhendesigningandoperatinginahigh-technologyenvironment.Manualhandling,trainingandemergencyproceduresarethreeaspectsofsafetymanagementthatshouldnotbeoverlooked.
Manual handling
95Thoroughlyassesstherisksarisingfrommanual-handlingoperationsassociatedwiththeuseandmaintenanceofthefuelcell.Inparticular,thechoiceoflocationandthemodeoffuelstorage(forexamplecylinders,refillablestaticstorageetc),easeofaccessandtheequipmentprovidedcanhaveasignificantimpactontheoverallriskfromtheinstallation.
Training
96Everyonewhomaybeaffectedbythehazardsassociatedwiththefuelcellinstallationshouldhavebeentrainedtoanappropriatelevel.Theoperationandmaintenanceofthefuelcellinstallationshouldbecoveredbyestablisheddocumentedprocedures.
Emergency procedures
97Documentedproceduresshouldbeestablishedtocoverallforeseeableemergencysituations.Appropriatetrainingontherequiredresponsetoemergencysituationsshouldthenbegiven.Duringtheplanningstageofafuelcellprojectitisgoodpracticetoinformthefirebrigadethathydrogenwillshortlybestoredatthelocation.
98Itislikelythatastheuseoffuelcelltechnologyaccelerates,manyapplicationswillinvolveinstallingequipmentintoexistingworkplaceenvironmentsratherthanintonewpurpose-designedareas.Thesafe‘retro-fitting’offuelcellsintoareaswithlittlepriorexperienceofhydrogen,especiallydomesticenvironments,willraiseamultitudeofnewissues.Manyoftheseissuesmaynothavebeenexaminedpreviouslyastheywerenotconsideredrelevantorwereoflittlesignificanceintheindustrialenvironmentsinwhichhydrogenhashistoricallybeenused.
99Thesenewhydrogenusage/storagesituationswilloftenpresentsignificanttechnicalandengineeringchallengestodutyholders.Oneofthemostsignificantofthesewillbetheverylargedemandforthetechnicalskillsnecessarytoensurethatappropriateriskassessmentsarecarriedout.Itisparticularlyimportantthatpressuretofindsolutionstotechnicalorcommercialproblemsdoesnotresultin‘tunnelvision’wheresafetyisconcerned.
100Themostimportantaspectofdesigningandoperatingafuelcellinstallationistoensurethat:
n the important hazards have been identified and appropriate measures taken so that the risk presented by the fuel cell installation is acceptable and has been reduced as low as is reasonably practicable.
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Legal requirements101Therearetwoareasofhealthandsafetylegislationrelevanttofuelcellinstallations:
n thoseidentifyinggeneralduties;n thoseregulatingparticularfeaturesortechnicalaspects.
General legislation
102EmployersarerequiredundertheHealthandSafetyatWorketcAct1974tosecurethehealth,safetyandwelfareofpeopleatworkandtoprotectthosenotatworkfromriskstotheirhealthandsafetyarisingfromworkactivities.
103TheManagementofHealthandSafetyatWorkRegulations1999,oftenreferredtosimplyasthe‘ManagementRegulations’,requireallemployersandself-employedpeopletoassesstheriskstoworkersandotherssothattheycandecidewhatmeasuresneedtobetakentofulfiltheirstatutoryduty.2
104ThegeneralprinciplesofanappropriateriskassessmentareidentifiedinBSEN1050:1997Safety of machinery. Principles of risk assessment23andintheManagementRegulations.Intheriskassessmentprocessemployersshouldidentifythepotentialhazardsanddeterminetheirsignificance.Theyshouldthentakeappropriateprecautionarymeasurestoreducetheriskfromthehazardstoanacceptablelevelthatisaslowasisreasonablypracticable.
105TheProvisionandUseofWorkEquipmentRegulations1998(PUWER98)willapplytofuelcellsinmostworksituationsandimposedutiestoensurethattheequipmentprovidedissuitableandappropriate.24
Legislation dealing with the fire and explosion hazards of fuel cells
106Employersandotherdutyholdersshouldensurethatthedesign,installation,operationandmaintenanceoffuelcellinstallationscomplieswiththerequirementsoftheDangerousSubstancesandExplosiveAtmospheresRegulations2002(DSEAR).1
107DSEARisasetofregulationsconcernedwiththeprotectionofpeopleagainsttherisksfromfireandexplosionarisingfromtheuseorstorageofdangeroussubstancesintheworkplace.Dangeroussubstancesincludeallthoseflammablematerialslikelytobeusedasfuelsforcells,forexamplehydrogen,methanol,naturalgasandLPG.UnderDSEARtherisksfromfireandexplosionarisingfromtheuseofdangeroussubstancesmustbeassessedinanappropriatemanner.
108AriskassessmentunderDSEARshouldincludeacarefulidentificationandexaminationofthedangeroussubstancespresentorlikelytobepresentintheworkplace.Itshouldconsiderwhichactivitiesinvolvedangeroussubstances,andhowtheseactivitiesmightgowrongandproduceafireorexplosionthatcouldharmemployeesorthepublic.ThepurposeofDSEARistohelpdeterminewhatneedstobedonetoeliminateorreducethesafetyrisksarisingfromtheuseofdangeroussubstancesinthefuelcellsystem.Theoverallriskassessmentshouldtakeaccountofthehazardsofthedangeroussubstancesusedandanyotherhazardsassociatedwiththeoperationofthefuelcell,forexample:
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Health and Safety Executive
n thelikelihoodofhazardousexplosiveatmospheresoccurring;n allpotentialignitionsources;n allforeseeablefactors,includingaccidentaldamageandvandalism;n controlofanynon-routineoperations;n maintenanceandrepairactivities;n manual-handlingissues;n humanfactorsandtrainingrequirements.
109Wherefiveormorepeopleareemployed,thefindingsoftheriskassessmentmustberecordedandreviewedatasuitablefrequencyorwhensignificantchangesoccurintheworkplace.
Legislation dealing with the installation and maintenance of fuel cells
110Fuelcellsoperatingonhydrogen,methane,ethaneorLPGmaybeclassifiedasgasappliancesundertheGasSafety(InstallationandUse)Regulations1998(GSIURegulations).9,25TheseRegulationsdealwiththesafeinstallation,maintenanceanduseofgassystems,includinggasfittingsandappliances,mainlyindomesticandcommercialsituations.Inmostsituationstheprincipalfunctionofthefuelcellwillbetheproductionofelectricityandnotheat.Whereelectricityistheprimaryoutput,irrespectiveofhowtheelectricalenergyisused,thefuelcellappliancewillnotbecoveredbytheGasApplianceDirective90/396/EEC(GAD).
111Regulation3oftheGSIURegulationsrequiresanyonecarryingoutworkonagasfittingorstoragevesseltobecompetenttodoso.Self-employedpeopleandemployersofpeoplecarryingoutworkongasfittingsandappliancesindomesticsituationsandnon-industrialpremisesarerequiredtobelongtoaclassofpersonsapprovedbytheHealthandSafetyExecutive.Currently,thismeansthatonlymembersoftheCouncilforRegisteredGasInstallers(CORGI)maycarryouttheworkinthesesituations.
112TheGSIURegulationsapplytofuelcellsusingmethane,ethaneorLPGindomesticandcommercialsituations.TheRegulationsalsocoverfuelcellsoperatingonhydrogenthatarelocatedindomesticpremises,butdonotapplytohydrogencellsinnon-domesticpremisessuchascommercialbuildings,warehouses,officesorfactories.
113Unlessthepremisesareusedfordomestic,sleepingoraccommodationpurposesorarehiredoutaspartofabusiness,theGSIURegulationsdonotapplytofuelcellswhentheyarelocatedinfactories,farms,constructionsites,mines/quarries,shipsorvehicles.25InthesesituationsDSEARwillnormallyapply.
114Insummary:
n whereafuelcelloperatesonhydrogeninadomesticsituationallinstallationorrepairworkmustbecarriedoutbya(CORGI)registeredinstallerwhoiscompetentintheworkbeingdone;
n whereafuelcelloperatesonmethane,ethaneorLPGinadomesticsituationorincommercialpremisesallinstallationorrepairworkmustbecarriedoutbya(CORGI)registeredinstallerwhoiscompetentintheworkbeingdone;
n whenafuelcellislocatedinafactoryallinstallationorrepairworkmustbecarriedoutbyapersoncompetenttocarryoutthatwork.TheydonotnecessarilyneedtoberegisteredwithCORGI.
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115TheenforcingauthorityfortheGSIURegulationsisHSEortherelevantlocalauthorityasdeterminedintheparticularcircumstancesbytheHealthandSafety(EnforcingAuthority)Regulations1998.26
116Ingeneral,DSEARandtheGSIURegulationsdonotcoverfuelcellslocatedonvehiclesoperatingonpublicroads.InmostinstancestheVehicleandOperatorServicesAgency(DfT)willbetheleadregulatorinthesesituations.
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Appendix 1: Fuel cell types and electrochemistry
Fuel cell type Electrolyte Operating
temperature
(ºC)
Electrode reactions
PEM:Protonexchange
membrane
Polymerelectrolyte
membrane
Perfluorosulphonicacidpolymer 60–100 Anode:2H2->4H++4e-
Cathode:O2+4H++4e-->2H2O
DMFC:Directmethanolfuel
cell
Perfluorosulphonicacidpolymer 60–100 Anode:2CH3OH+2H2O->2CO2+12H++12e-
Cathode:12H++3O2+12e-->6H2O
PAFC:Phosphoricacidfuel
cell
Liquidphosphoricacidsoakedina
matrix
175–100 Anode:2H2->4H++4e-
Cathode:O2+4H++4e-->2H2O
AFC:Alkalinefuelcell Aqueouspotassiumhydroxide
soakedinamatrix
90–100 Anode:2H2+4OH-->4H2O+4e
-
Cathode:O2+2H2O+4e-->4OH-
MCFC:Moltencarbonate
fuelcell
Moltenlithiumandsodium/
potassiumcarbonatesinamatrix
600–1000 Anode:2H2+2CO32-->2H2O+4e
-+2CO2
Cathode:O2+CO2+4e-->2CO32-
SOFC:Solidoxidefuelcell Solidzirconiumoxidewithtraceof
Yttria
600–1000 Anode:2H2+2O2-->2H2O+4e
-
Cathode:O2+4e-->2O2-
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Appendix 2: MINIMUM SEPARATION DISTANCES
Type of exposure Distance from hydrogen
source (m)
1 Openflame,ignitionsourceincludinguncertifiedelectrical
equipment
5
2 siteboundary,orareaswherepeoplecongregate,such
ascarparks
8
3 Building,woodframeconstruction 8
4 Wallopeningsinofficesorworkshops(installations
shouldnotbedirectlybelowopenings)
5
5 BulkflammableliquidsorLPGaboveground 8
6 BulkflammableliquidsorLPGunderground 5
7 Flammablegascylinderstorageotherthanhydrogen 5
8 Oxygencylinderstorage 5
9 Liquidoxygenstorage 8
10 Liquidnitrogenorargonstorage 5
11 Storedcombustiblematerial,egtimber 8
12 Aircompressorandventilatorintakes(installationsshould
notbedirectlybelowsuchintakes)
8
13 Activityotherthanthatdirectlyrelatedtothehydrogen
installation
5
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GlossaryAnode:Theelectrodeatwhichtheoxidationreactionofthecelloccurs.Thiselectrodeacceptselectronsfromsubstancesinthecell.Catalyst:Asubstancethatspeedsupachemicalreactionbutisnotconsumedinthereaction.
Cathode:Theelectrodeatwhichthereductionreactionofthecelloccurs.Thiselectrodedonateselectronstosubstancesinthecell.
CFD:Computationalfluiddynamics.Theuseofcomputermodellingtosimulateandpredictthemovementandconcentrationgradientsofgasesandliquids.
Cogeneration:Thesimultaneousproductionofelectricityandheatfromapowersource.
Dangerous substance:Asubstanceormaterialwhich,becauseofitspropertiesorthewayinwhichitisused,couldcauseharmtopeople.
DSEAR:TheDangerousSubstancesandExplosiveAtmospheresRegulations2002.
Direct methanol fuel cell (DMFC):Afuelcellinwhichmethanolisoxidiseddirectlyattheanodewithoutpriorreformingtohydrogen.
Distributed generation:Small-scalepowergenerationequipmentthatprovideselectricalpoweratormuchclosertothecustomer’ssitethancentrallylocatedlarge-scalepowerstations.
Electrode:Asolidelectricalconductorthroughwhichelectricityentersorleavesthecell.
Electrolyte:Anon-metallicconductorinwhichthecurrentiscarriedbythemovementofions.
External reforming:Productionofhydrogenfromahydrocarbonorotherhydrogen-richfuelbeforeentryintothefuelcell.
Fluorocarbon:Chemicalcompoundcomposedalmostentirelyoftheelementscarbonandfluorine.
Fuel:Substanceusedtogenerateheatorelectricalpowerthroughachemicalreactionsuchascombustionorelectrochemistry.
Fuel cell:Anelectrochemicaldevicethatcontinuouslyconvertsthechemicalenergyofafuelandanoxidisingagentintoelectricalenergy.Thefuelandoxidantarestoredoutsidethecellandaretransferredtothecellastheyareconsumed.
Hazardous area/place:Aplaceinwhichanexplosiveatmospheremayoccurinsuchquantities/frequenciesastorequirespecialprecautionstoprotectthehealthandsafetyoftheworkersconcerned.
Hydrocarbon:Achemicalcompoundconsistingofonlytheelementscarbonandhydrogen,forexamplemethane,propane,butaneetc.
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Incendive:Havingsufficientenergytoigniteaflammablemixture.
Ignition source:Asourceofenergy,suchasasparkorhotsurface,thatislikelytocauseaflammablemixturetocatchfire.
Ion:Anelectricallychargedatomormolecule.
Matrix:Thesupportingmaterialintowhichtheactivematerialsareembedded.
Membrane:Theseparatinglayerincertaintypesoffuelcell(PEMandDMFC)thatactsasanelectrolyteaswellasabarrierfilmsegregatingthegasesintheanodeandcathodecompartments.
Oxidation:Thelossofelectronsfromasubstance.Inafuelcellthisisthereactionthatgeneratestheelectriccurrent.
Reformer:Acatalyticdeviceinwhichhydrocarbonfuelsareconvertedintohydrogen-richfuelgasessuitableforuseinafuelcell.
Unprotected electrical equipment:Electricalequipmentwhich,becauseofitsdesignormanufacture,isnotsuitableforuseinapotentiallyexplosiveatmosphere.
Ventilation:Thesupplyofsufficientcleanairtoensurethatreleasesofdangeroussubstancesdonotaccumulatetoaconcentrationthataffectspeople’shealthandsafety.
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References1 Dangerous substances and explosive atmospheres. Dangerous Substances and Explosive Atmospheres Regulations 2002. Approved Code of Practice and guidanceL138HSEBooks2003ISBN07176220272 Management of health and safety at work. Management of Health and Safety at Work Regulations 1999. Approved Code of Practice and guidanceL21 (Secondedition)HSEBooks2000ISBN07176248893 Gaseous hydrogen stationsIGCDoc15/96EuropeanIndustrialGases Association4 Safety standard for hydrogen and hydrogen systemsNSS1740.161997 NationalAeronauticsandSpaceAdministration5 Basic considerations for the safety of hydrogen systemsISO/DPAS15916 20016 Agreement on production and storage of hydrogen. Task 12: Metal hydrides and carbon for hydrogen storage: Final task report InternationalEnergyAgency7 DKSlatteryandMDHamton‘Complexhydridesforhydrogenstorage’ Proceedings of 2002 hydrogen programme reviewUSDoE8 Essential gas safety(Thirdedition)2003CORGITel:087051681119 Safety in the installation and use of gas systems and appliances. Gas Safety (Installation and Use) Regulations 1998. Approved Code of Practice and guidanceL56(Secondedition)HSEBooks1998ISBN071761635510Bulk LPG storage at fixed installationsCodeofpractice1LiquefiedPetroleum GasAssociation11Lewis,RJSax’s dangerous properties of industrial materials(Tenthedition) JWileyandSons2000ISBN047135407412BSEN60079-10:2003Electrical apparatus for explosive gas atmospheres. Classification of hazardous areasandPD60079-14:2000A guide to the application of BS EN 60079-14BritishStandardsInstitution
13Area classification code for installations handling flammable fluids. Model code of safe practice in the petroleum industryPart15InstituteofPetroleum ISBN0852932235
14Safe use and handling of flammable liquidsHSG140HSEBooks1996 ISBN0717609677
15Electricity at work: Safe working practicesHSG85(Secondedition)2003 HSEBooksISBN071762164216Safety in storage, handling and distribution of liquid hydrogenDoc06/02/E EuropeanIndustrialGasesAssociation17Industrial gas cylinder manifolds and distribution pipework/pipelines (excluding acetylene)CodeofPracticeCP4BritishCompressedGasesAssociation
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18Determination of safety distancesIGCDoc75/01/E/revEuropeanIndustrial GasesAssociation19BSEN50073:1999Guidelines for selection, installation, use and maintenance of apparatus for the detection and measurement of combustible gases or oxygenBritishStandardsInstitution20The Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres Regulations 1996SI1996/192TheStationeryOffice 1996ISBN011053999021Fuel cell technologies. Part 2: Fuel cell modulesDraftIEC62282-222COSHH essentials: Easy steps to control chemicals - Control of Substances Hazardous to Health Regulations HSG193(Secondedition)HSEBooks2003 ISBN071762737323BSEN1050:1997Safety of machinery. Principles for risk assessment BritishStandardsInstitution24Safe use of work equipment. Provision and Use of Workplace Equipment Regulations 1998. Approved Code of Practice and guidance1998L221998 HSEBooksISBN071761626625The Gas Safety (Installation and Use) RegulationsSI1998/2451 TheStationeryOffice1998ISBN011079655126The Health and Safety (Enforcing Authority) Regulations 1998SI1998/494 TheStationeryOfficeISBN0110656423
Whileeveryefforthasbeenmadetoensuretheaccuracyofthereferenceslistedinthispublication,theirfutureavailabilitycannotbeguaranteed.
Further informationForinformationabouthealthandsafetyringHSE’sInfolineTel:08453450055Fax:08454089566Textphone:08454089577e-mail:[email protected],CaerphillyBusinessPark,CaerphillyCF833GG.
HSEpricedandfreepublicationscanbeviewedonlineororderedfromwww.hse.gov.ukorcontactHSEBooks,POBox1999,Sudbury,SuffolkCO102WATel:01787881165Fax:01787313995.HSEpricedpublicationsarealsoavailablefrombookshops.
BritishStandardscanbeobtainedinPDForhardcopyformatsfromtheBSIonlineshop:www.bsigroup.com/ShoporbycontactingBSICustomerServicesforhardcopiesonlyTel:02089969001e-mail:[email protected].
TheStationeryOfficepublicationsareavailablefromTheStationeryOffice,POBox29,NorwichNR31GNTel:08706005522Fax:08706005533e-mail:[email protected]:www.tso.co.uk(Theyarealsoavailablefrombookshops.)StatutoryInstrumentscanbeviewedfreeofchargeatwww.opsi.gov.uk.
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