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Health and Safety Executive
Safety advice for bulk chlorine installations
This is a free-to-download, web-friendly version of HSG28 (Second edition, published 1999). This version has been adapted for online use from HSE’s current printed version.
Youcanbuythebookatwww.hsebooks.co.ukandmostgoodbookshops.
ISBN 978 0 7176 1645 2 Price £14.00
Thisbookletgivesguidanceonthesafehandlingofchlorineatsiteswhichreceivebulkdeliveriesofchlorinebyroadorrailtanker.
Itisaimedatthemanagersoftheseinstallations,butitisalsorelevantforplantsupervisors,designandmaintenanceengineersandsafetyprofessionals.
HSE Books
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Health and Safety Executive
© Crown copyright 1999
Firstpublished1987
ISBN9780717616452
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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Health and Safety Executive
ContentsForeword 5
Introduction 6
Management of health and safety and risk assessment 7Riskassessment 8Design and location of installations 10Potentialincidents 10Sitingofinstallations 10Unloadingarea 12 Design and location 12 Deliveries of liquid chlorine by road tanker or ISO tank container 13 Interlocks 14 Deliveries of liquid chlorine by rail tanker 15Connectionsbetweenthetankerandthefixedlinestothestorageinstallation 16 Types of connection 16 Flexible couplings (semi-rigid loading arms) 16 Flexible hoses 17 Articulated arms 17 Pipeworkforliquidchlorine 17 Permanent pipework at the unloading point 18 Design criteria for pipework transferring liquid chlorine to storage tanks or from storage to point of use 18 Protection of pipework 19 Marking 20 Protectionofliquidchlorinepipeworkagainstoverpressure 20 Provision of relief systems 20 Valves 21 Types of valve 22 Vertical globe valves 22 Conical plug valves (PTFE-sleeved) 22 Ball valves 23 Remotely controlled valves 23 Storagevessels 23 Design criteria 24 Connecting pipework and means for isolation of storage tanks 25 Liquid chlorine inlet 26 Liquid chlorine outlet 26 Vent and compressed dry gas lines 28 Relief system 28 Instrumentation and chlorine detector systems 28 Chlorine detectors and alarms 29Protectionofstoragevesselsagainstoverpressure 30 Relief system 31 Bursting discs 31 Arrangements for relief systems 31 Expansion vessels 33 Pressure alarms 33Arrangementsforunloadingofliquidchlorinefromroadtankerstostorage 34 Unloading using dry compressed air or dry nitrogen 34 Supply of dry padding gas to the system 35 Unloading using chlorine gas pressure 35 Use of re-compressed chlorine vapour 35 Chlorinevaporisers 36
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Types 36 Regulation of throughput 37 Methods of heating 37 General installation 38 Hazards 38 Routine and emergency isolation 40 Pressure control valve 41 Corrosion 41Chlorineabsorptionsystem 42 Vent collection system 43 Absorption equipment 43 Instrumentation 43 Disposal of effluent from the chlorine absorption plant 44
Operating and maintenance procedures, training and PPE 45Operatinginstructions 45Maintenance,inspectionandinstallation 45 General maintenance requirements 45 Maintenance of connections 46 Inspection and commissioning of chlorine tank installations 46 Inspection procedure 47 Testing 48Modificationofthechlorinesystemandclearanceprocedures 48Unloadingofliquidchlorinefromroadtankerstostorage 49 UseofISO(demountable)tankcontainers 50Transferofchlorinetotheconsumingunits 51 Transfer of gaseous chlorine 51 Transfer of liquid chlorine using vapour pressure 51 Transfer of liquid chlorine by padding with dry compressed gas 51 Transfer of liquid chlorine using a separate pumping tank 51 Precautions 52 Training 53 Competency and audit 53PersonalProtectiveEquipment(PPE) 54 Selecting suitable respiratory protective equipment (RPE) 54
Emergency arrangements 57 Emergencyequipment 57Controlofleakages 58 Releases inside buildings 59
Appendices 601Toxicologicalpropertiesandfirstaid 602Characteristicsofchlorine 613RelevantlegislationandHSEguidance 644Usefulcontactsandstandards 725Outsideinstallationsandinsideinstallations 756Proceduresfordischargingroadtankersofchlorine 777Typesofvaporiser 808Emergencyplans 83
References 85
List of acronyms and abbreviations 90
Further information 91
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ForewordTheaimofthisguidancenoteistohelpthoseresponsibleforthesafeuseofchlorinefrombulkcontainerstomeettheirobligationsunderhealthandsafetylaw.
Thisguidance,likethedocumentthatprecededit,waspreparedwiththehelpofthechlorineproducers,users,tradeunions,theWaterServicesAssociation(WSA),andtheChemicalIndustriesAssociation(CIA).
Wearegratefultothosewhocontributedfortheirassistanceandco-operationinpreparingthisadvice,andtoShawValvesandtoDescoteLtdforpermissiontousethephotographslinkedtoparagraph74,toWestonPointStudiosforpermissiontousethephotographslinkedtoparagraph216andtoZenecaplcforpermissiontotaketheremainingphotographs.
Theguidelinesmaybeappliedtoanybulkchlorineinstallationbuttheyarenotintendedtobeadetaileddesigncode.Someexistinginstallationsmaynotatpresentmeetalltherecommendationsand,insomecases,notalltherecommendationsmaybeappropriate.Itisfortheoccupier,usuallyinconsultationwiththechlorinesupplierand/orspecialistadvisers,tojudgetheneedforfurtherriskcontrolmeasures,followinganassessmentoftheactualrisks.Ifimprovementsareshowntobeneeded,aresponsibledecisionisrequiredfromtheoperatingcompanyonthenatureandtimingofchangessothattheycanbemadesafely.
WherereferencetoBritish,Europeanandotherstandardsismadeinthisdocumentequivalentstandardsareequallyacceptablealternatives.
Youmayneedhelpbeyondthatgiveninthisguidance.Ifyoudo,tradeandemployerassociations,suchastheChemicalIndustriesAssociationandEuroChlor,oryourchlorinesuppliercanofferarangeofadviceandsupport.TheseandothersourcesofinformationaregiveninAppendix4.
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Introduction1 Thispublicationgivesguidanceonthesafehandlingofbulkliquidchlorineatsiteswhichreceiveliquidchlorinebyroadorrailtanker,orbyISOtankcontainer.Theguidanceisaimedprimarilyatmanagersoftheseinstallations,butitisalsorelevantforplantsupervisors,designandmaintenanceengineers,andsafetyprofessionals.Applicationoftheguidancewillhelptoensurethattheriskstopeopleon-siteandoff-siteareminimisedsofarasisreasonablypracticable.
2 Therisksarisebecausechlorineisahighlytoxic(seeAppendix1)andreactivesubstance(seeAppendix2).Itformsflammableandexplosivemixtureswithsomeorganicandinorganicsubstances.Whenreleasedfromcontainmentitformsagascloudthatisheavierthanairandwhichmaintainscontactwiththegroundasitdisperses,possiblyendangeringpeopleinitspath.
3 Despitetheserioustoxicandreactivehazards,andthepotentialtoharmpeopleoff-site,thechlorineindustryhasestablishedaverygoodsafetyrecord.Thishasbeenachievedthroughthedevelopmentandpracticeofeffectiveproceduresforhandlingchlorinesafely.Thisguidance,likethedocumentitreplaces,isissuedtohelpmaintainandenhancethatrecord.Guidanceonthesafehandlingofchlorinesuppliedindrumsandcylindersisgivenelsewhere.1
4 TheguidanceisbasedonthecombinedexperienceofthefourUKmanufacturersofchlorine,theircustomers,tradeunionsandassociationsandHSE.Itcoversthesafetyandhealthrequirementsatallstages,fromthereceiptoftheliquidchlorinetothepointofuse,includingthelocation,design,testing,operationandmaintenanceofequipment.Proceduresfordealingwithemergenciesarealsooutlined.
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Management of health and safety and risk assessment5 EmployershavealegalresponsibilityunderSections2and3oftheHealthandSafetyatWorketcAct1974(HSWAct)2toensure,sofarasisreasonablypracticable,thehealthandsafetyoftheiremployeesandotherswhomaybeaffectedbytheiractivities.Otherpeople,suchasdesigners,installersandsuppliers,alsohavesimilardutiesundertheHSWActwithrespecttoproducts.Since1974variousregulationshavebeenmaderequiringspecificcontrolsforparticularhazards(egpressuresystems),oractivities(egmanualhandling).Alistoftheseandothercurrenthealthandsafetylegislation,codesofpracticeandguidanceispublishedannually.3Thislistalsocoversamendmentstotheregulations.Referencesinthisdocumentaretothebaseregulations.Appendix3givesanoverviewofthemainlegislationandregulationsrelatingtothesafehandlingofchlorine.
6 YoumustobtainplanningpermissionfornewinstallationsintheusualwayfromtheLocalPlanningAuthority,whowill,whenappropriate,refertoHSEforadvice.Ifyoustore,orplantostore,morethan10tonnesofchlorine,yoursitewillbesubjecttoanumberofspecificregulations.
7 TheNotificationofInstallationsHandlingHazardousSubstancesRegulations19824requireyoutonotifyyouractivitytoHSEifmorethan10tonnesofchlorineisliabletobekept.Youmustalsonotifysubsequentchangestoyouractivity.Newinstallationsover10tonneschlorinecapacity,orproposalstoincreasethenotifiedcapacitytomorethanthreetimestheoriginalcapacity,mustbenotifiedthreemonthsinadvance.TheformofthenotificationisintheRegulations.
8 TheControlofIndustrialMajorAccidentHazardsRegulations1984(CIMAH)5alsoapplytositesstoringorprocessingchlorine.Theseregulationsapplyattwolevels.Thelowerlevelrequirementsapplytositeswhichstore10ormoretonnes.Theyalsoapplyatsiteswherechlorineisinvolvedinaprocessinanyquantity,unlesstheprocessoperationisincapableofproducingamajoraccidenthazard.Youneedtocomplywithtwogeneralrequirements:
(a) todemonstratetoHSE,atanytime,thatmajoraccidenthazardshavebeen identifiedandadequatelycontrolled;and(b) toreportanymajoraccidentstoHSE.
Forsiteswhichstore75ormoretonnes,orwhichprocesschlorineandhaveinventoriesof25ormoretonnes,unlesstheprocessoperationisincapableofproducingamajoraccidenthazard,morestringentregulationsapply.Theserequirethepreparationofasafetyreport,thepreparationofon-siteandoff-siteemergencyplansandtheprovisionofinformationtomembersofthepubliclikelytobeaffectedbyamajoraccident.CIMAHwillbereplacedinFebruary1999bytheControlofMajorAccidentHazardRegulations(COMAH)whichimplementtherequirementsoftheSevesoIIDirective6onthecontrolofmajoraccidenthazards;thethresholdforthelowertierrequirementsis10tonnes,and25tonnesforthetoptier.
9 ThePlanning(HazardousSubstances)Regulations19927applytositeswith10ormoretonnesofchlorine.Undertheseregulationsthe‘consent’ofthelocalHazardousSubstancesAuthority(HSA)isneededforthepresenceofchlorineinsuchquantities.TheHSAmustconsultHSEontheassociatedrisklevels.Toquantifytheoff-siterisksHSEmayrequesttechnicalinformationabouttheinstallation.8
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10 Inaddition,anyprocesswhichinvolvesthemanufactureoruseofchlorineoranyprocesswhichislikelytoresultinthereleaseofchlorineintotheairorwater,isaprescribedprocessundertheEnvironmentalProtection(PrescribedProcessesandSubstances)Regulations1991.9OtherprocessesarealsoprescribedintheRegulations.UndertheEnvironmentalProtectionAct199010nopersonshallcarryonaprescribedprocessexceptunderanauthorisationgrantedbytheenforcingauthorityandinaccordancewiththeconditionsintheauthorisation.ApplicationsfortheauthorisationofaprescribedprocessinEnglandandWalesmustbemadetotheEnvironmentAgency(EA)andinScotlandtotheScottishEnvironmentalProtectionAgency(SEPA).InadditioninScotlandwheretheAlkaliandWorksRegulationAct1906,11asamendedbytheHealthandSafety(EmissionsintoAtmosphere)Regulations1983,12isstillinforce,suchprocessesarelistedasScheduledworksandmustberegisteredannuallywithSEPA.
11 Ifyoufillcontainersfromyourbulkinstallationandtransportthemoff-site,youwillneedtocomplywiththeCarriageofDangerousGoods(Classification,PackagingandLabelling)andUseofTransportablePressureReceptaclesRegulations1996,13andtheCarriageofDangerousGoodsByRoadRegulations199614(inthecaseoftransportationbyroad).TherelevantlegislationisoutlinedinanHSEbooklet.15Note:The(legal)termforgascylindersisnow‘transportablepressurereceptacles’.
12 Althoughyoumustcomplywithhealthandsafetylegislation,regulatorycontrolcannotcompensatefordeficienciesinthewaythatsafetyismanaged.Effectivehealthandsafetymanagementismainlyaboutmanagement(atalllevels)takingaproactiveapproachtominimisethechanceofincidentsoccurringratherthanputtingthingsrightaftertheyhavegonewrong.Guidanceoneffectivehealthandsafetymanagementisgivenelsewhere16,17whichadvocatesandelaboratesonthefollowinggeneralprinciplesofgoodmanagementpractice:
(a) setyourpolicyanddemonstratecommitmenttoit;(b) organiseandtrainyourstafftoensureeffectivecommunications,co-operation, andtheircompetencetocontrolrisks;(c) planwhatyouneedtodo,setperformancestandards,andestablishsystems andproceduresforcontrollingrisks;(d) measureyourperformancetoassesswhethertherisksarebeingadequately controlled;(e) conductsafetyauditstoensurethatyoursystemsareworkingasintended; reviewyourfindingsandtakeanycorrectiveaction.
AriskassessmentisessentialtothisproactiveapproachtosafetymanagementandisastatutoryrequirementoftheManagementofHealthandSafetyatWork(MHSW)Regulations1992.18GuidanceontheseRegulationsandriskassessmentiscontainedinanApprovedCodeofPractice.19
RISK ASSESSMENT
13 TheMHSWRegulationsrequireyoutoconductafullriskassessmenttoidentifyallthehazardsandassesstheassociatedrisks.Theriskassessmentneedstoincludeallsourcesofhazards,includingthoseassociatedwithtransportaroundthesite,accesstoplantandsecurity.Theneedforriskassessmentisalsoarequirementofotherregulations(egTheControlofSubstancesHazardoustoHealthRegulations1994(COSHH)20andtheFirePrecautions(Workplace)Regulations1997.21
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14 Inoutline,ariskassessmentforyourchlorineoperationsrequiresyouto:(a) lookforthehazardsiepotentialsourcesofchlorinereleases;(b) decidehowseriouseachoftheseloss-of-containmenteventscouldbe,iewho couldbeharmedandhowseriously;(c) decidethelikelyfrequencyofeachofthesehazardousevents;(d) evaluatetheassociatedrisksandconsiderwhethertheprecautionstoprevent releasesofchlorineandtomitigatetheireffectsareadequate,orifmore shouldbedone(thisguidanceandthesourcesofadvicelistedinAppendix4 isrelevanthere;particularlythepublicationsofEuroChlor;22(e) recordyoursignificantfindings;thisisastatutoryrequirementifyouhavefive ormoreemployees;and(f) updateyourriskassessmentatleasteverythreeyears,andbeforemaking significantmodifications.Checkthatyouroperationalexperienceaccordswith anysignificantassumptionsyoumadetocarryoutyourriskassessment. Safetyaudits,aswellasday-to-daymanagementarrangements,should addresstheneedtocheckassumptions.
15 Eachsitewillhaveitsownspecialfeaturesandyouneedtotaketheseintoaccountwhenconductingyourriskassessment.Aproperriskassessmentwillhelpyouto:
(a) decidewhethertherisksarebeingcontrolledsofarasisreasonably practicable;and,ifnot,to:(b) establishadequatecontrolsandsafeworkingproceduresbasedontheadvice inthisnote.
16 Yourriskassessmentwillneedtoconsiderthemainpotentialcausesof releasesofchlorine.Forbulkchlorineinstallationstheseare (seeparagraph20):
(a) plantdamagecausedbyexternalsources(vehicles,hoists,flyingdebrisfrom nearbyaccidents,firesetc);(b) incorrectoperation;and(c) inadequateinspectionandmaintenance.17 Thepeopleconductingyourriskassessmentmusthaverelevantexperienceandknowledge.Ifnecessary,youmust18seekassistancefromexperiencedandknowledgeablepeople.Yourchlorinesupplierwillbeabletoidentifycompetentpeopleabletoconducttheriskassessmentonyourbehalf,andsupplyinformationtohelpyoucarryoutyourriskassessmentandtomanagesafety.
18 Theremainingsectionsofthisbookletprovideguidanceonthearrangementsforpreventionandmitigationofchlorineleaksandspillagesthroughgooddesign,operation(includingemergencyprocedures)andmaintenance.Theguidanceappliesonlytoinstallationsstoringliquidchlorineunderpressureinbulktanksortankcontainers.YoushouldthereforepayparticularattentiontotherequirementsofthePressureSystemandTransportableGasContainerRegulations1989(PSTGC).23Precautionsforthestorageofliquidchlorineinrefrigeratedtanksatlowpressureareoutsidethescopeofthisguidance.AdditionalsourcesofadviceandinformationarelistedinAppendix4.
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Design and location of installations19 Bulkchlorineinstallationsoperateunderpressure.Consequently,thedesign,installationandoperation(includingperiodicexaminationandmaintenance)ofthesepressuresystemswillneedtomeettherequirementsofPSTGC.23Pipework,equipmentandprotectivedevicesforliquidchlorinearepartofthesystem.Theregulationsdonotapplytosystemsoperatingatorbelowpressuresof0.5bargauge,exceptforsteamsystems.GuidanceonPSTGCiscontainedinanApprovedCodeofPractice24andthepublicationA guide to the Pressure Systems and Transportable Gas Containers Regulations 1989;25seeAppendix3forbriefdetails.
POTENTIAL INCIDENTS
20 Whendesigningormodifyingyourinstallation,youshouldincludeprovisionstopreventthefollowingpotentialincidentswhichcouldresultinareleaseofchlorine:
(a) Damagetochlorinelinesfromexternalsourcesegbyhoistsorvehicles- includingtheroadtankerwhileitismovingtoorfromtheunloadingpoint. Whenthetankerispositionedforunloadingyouneedtoprovideadequate clearanceforthevalvedomewhenitisopen.Youalsoneedtomake allowanceformovementofthedeliveryvehicleduringthetransferoperation, egthenormalupwardmovementofthetankeronitssuspensioncancause damageifthereisinadequateflexibilityintheconnection,ormovement causedbyinadequatebrakingorwheelchockingorcarelessoperationbythe driver.(b) Damagetotheliquidchlorinedeliveryvehicle,storagetankorconnecting pipeworkcausedbyimpactfromothervehicles.(c) Jointandgasketfailuresduetofailuretotightenjoints,over-tighteningof joints,incorrectlyfittedortheuseofunsuitablejointrings,ortheuseof hydrocarbonbasedlubricantswhichmayburnwhenattackedbychlorine(see Appendix2).(d) Errorsinoperatingprocedures,includingover-fillingofthestoragetankand overloadingoftheventscrubber,failuretoclosevalveswhenremoving containers,orbreakingintothesystemformaintenance.(e) Plantandequipmentfailureduetoinadequatemaintenance,eg‘passing’ valves,orleakscausedbycorrosionorerosion,oruseofplantandequipment beyondtherecommendedlife.(f) Damagecausedbyfireorexplosion.
SITING OF INSTALLATIONS
21 Theguidanceinthissectionrelatestogeneralfeatureswhichaffectthelocationoftheinstallation.Morespecificfactorsarereviewedinthedetailedsectionsdealingwithoff-loading(seeparagraphs134-147)andemergencyprocedures(seeparagraphs247-263).Whendecidingthelocationofyourinstallationanimportantconsiderationisthepotentialriskstopeopleandtheenvironment.Theserisksdecreaseastheseparationdistanceincreases.Thesizeofsuchseparationdistanceswilldependuponanumberoffactors,including:
(a) thenumberandsizeofstoragetanks;(b) whetherthestorageisindoorsoroutside;(c) theoperationalconditionsandthetypeofprocess;(d) thefrequencyofchlorinedeliveries;
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(e) thedesignoftheinstallation,eglengthanddiameterofliquidandvapourlines; and(f) thesize,distribution,andtype(egsensitivegroups)ofthesurrounding population.
22 Youshouldcarefullyconsiderthesefactorswhendesigninganddecidingthelocationofyourinstallationandwhenconductingyourriskassessment(seeparagraphs13-17).Youshouldinvolveyourchlorinesupplieratanearlystage.Considerationshouldbegiventomaximisingthedistancebetweenthesiteboundaryandthechlorineinstallation.Itshouldbeemphasisedthatyourriskassessmentandindividualcircumstances(seeparagraph21)willdeterminetheseparationdistances.Thesameconsiderationsalsoapplywhenmakingsignificantchangestoanexistinginstallationwithinasite.
23 Whenchoosingthelocationforyourchlorinearea,youneedtoconsiderthelocationofotheron-sitebuildingsinrelationtotheprevailingwinddirection.Itisrecommendedthatthechlorineareashouldbelocateddownwindofbuildingsthatareregularlyoccupied.Ventilationintakestooccupiedroomsshouldbeatleast25mfromthechlorineinstallation,andpreferablyatahighlevel.
24 Youalsoneedtotakeaccountoftheprevailingwinddirectionwhendecidingthelocationsofemergencyassemblypoints.Twoassemblypointsarerecommended;theseshouldbelocatedsothatatleastonewillbeavailableregardlessofthewinddirectionwhenareleaseoccurs.Forcomplexsites,indoorassemblypointsarerecommended;openairassemblypointsmaybesuitableforsimplesites.
25 Foranewinstallation,fullaccountwillhavetobetakenofanyrequirementsattachedtotheplanningpermissiongrantedbythePlanningAuthority.InadditionthelocalPlanningAuthorityneedstoensurethattheoverallplanwillavoidproblemsarisinginthefuturefromdevelopmentsleadingtoahighdensityofpopulationneartheinstallation,orfromtheintroductionofotherpotentialhazardsinanadjacentarea(seeAppendix3:Planning(HazardousSubstances)Regulations1992).ForsiteswhichmaypresentsuchhazardsHSEmayrecommendthatthehigheststandardsareapplied,beforeconsentcanbegrantedbytheHSA.Insomecasestheconsiderationofoff-siterisklevelsbyHSEmayrequirecontrolmeasuresinadditiontothoserecommendedinthisguidance.
26 Forexistinginstallations,controlofneighbouringpopulationdensitiesisnotpossibleintheshortterm.However,proposeddevelopmentsnearbywhichwouldincreasethenumberofpeoplearecontrollableandwouldbepermittedbythelocalPlanningAuthorityonlyafterdetailedconsideration.SuchconsiderationwillincludetheadvicereceivedfromHSEontherisksfromchlorinereleasestothosewhomayoccupyorusetheproposeddevelopment.
27 Thelocationofanewchlorineinstallationwithinasiteshouldbedecidedfollowingariskassessment.Inmakingyourdecisionyoushouldtakeintoaccountpossibledamagefromfloodingorsubsidence,andthepossibledamagetotheinstallationifneighbouringplantorfactoriessufferacatastrophebyfireorexplosion.Installationsshouldbesitedatasufficientdistance(25mminimum)frompublicroadsormainrailwaylinestoreducetheriskofdamagetotheinstallationifthereisanaccident.Protectivebarriersshouldbeinstalledwherenecessary.
28 Inallcases,suitablefences,togetherwithadequatesecuritysupervision,shouldbeprovidedtominimisethepossibilityofunauthorisedaccess.
29 Hazardsarisingfromaircraftmaynormallyberegardedasminimalwithprobabilitiesbelowthelevelofsignificancerequiredforanyspecialconsideration.
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However,attentionmaybenecessaryinexceptionalcircumstances,egiftheinstallationisattheendofanairportrunwayorclosetoabusyairfield.Insuchcircumstancesliaisonwiththeairfieldoperatoronsuitableriskreductionmeasuresisessential.
30 Theinstallationispreferablylocatedintheopenair;butundersomecircumstancesanindoorinstallationmaybeappropriate.Indecidingthis,itisimportantthatariskassessmentismade,takingintoaccountthefactorslistedinAppendix5.Youneedtoconsiderthefollowingpossibleriskreductionmeasuresatanearlystage:
(a) thescopeforreducingthechlorineinventory,egreschedulingofdeliveries;(b) interlockingarrangements(seealsoparagraphs35,39-41)fortheautomatic isolationofleaksandtopreventthedeliveryvehiclemovingduringtransfer operations;(c) minimisingthelengthanddiameterofpipeworkcarryingliquidchlorineand ensuringoverpressureprotection;(d) mechanicallyventilatingchlorinebuildingsanddischargethroughafume scrubbingsystem;theassociatedairinletductsshouldbeatalowlevel;(e) improvingtheleak-tightnessofanychlorinebuildingagainstmajorleaks;and(f) restrictingtransfersofchlorinetodaylighthoursornormalworkinghours(8.00 amto5.00pm)astheweatherconditionsarelikelytobemorefavourablefor thedilutionofchlorineconcentrationsifthereisarelease.
UNLOADING AREA
Design and location
31 Youshouldaimtominimisethepossibilityofchlorineescapeduringthetransferofliquidchlorinefromthedeliveryvehiclestothestoragetank.Detailedattentiontothesiting,designandlayoutoftheunloadingequipmentandoperatingprocedureisessential.
32 Theunloadingareashouldbeonreasonablylevelgroundwithadequatesurroundingspaceprovidinggoodaccessfromdifferentdirections.Thelocationshouldminimisetheriskofimpactdamagefromvehicles,mobileequipmentorfallingobjectsfromliftingequipment.
33 Theunloadingpointshouldbereasonablyclosetothestorageinstallation.Toavoidimpactdamageaprotectivebarrierbetweenthetankerbayandthestorageinstallationisrecommended.Theunloadingpointshouldalsobesitedatasafedistancefromdrains,rivers,drainagecollectionpointsandanyplantorequipmentwhichmightgiverisetofireorexplosion.
34 Satisfactoryaccessshouldbeprovidedtothepermanentpipeworkfordischargeofthechlorinetankersandtoensurethatconnectionstothetankerscanbemadesafely.Wherethisinvolvesworkingfromaplaceabovegroundlevel,apermanentstructureshouldbeprovided.Thisshouldbedesignedsothat,incaseofemergency,escapeispossiblewithminimumrisk.Youcanachievethisbyinstallingasubstantialandnon-flammable(egsteel)structureandensuringthatplatformsarefreeofobstructionsandhavenon-slipsurfaces,adequatetoe-boardsandguard-rails.Alternativeescapewaysshouldbeprovidedwithstairwaysofstandardslope.Verticalladdersorsteepstairwaysshouldbeavoided.Ifverticalladdersareunavoidable,ensurethatsafetyhoops,etc,donotimpedeaccessforpeoplewearingbreathingapparatus.Thedesignofmoveableplatformsgivingaccesstothetopofthetankersneedstominimisethepossibilityofaccidentsduetocollisionwiththetankers.Interlocksystemsmaybeusedforthispurpose,seeparagraphs39-41.
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Awelldesignedunloadingarea
35 Youneedtoprovideforthesafeisolationofanyleaksthatmayarise,particularlyfrompipeworkcarryingliquidchlorine.Itisrecommendedthatremotelyorautomaticallycontrolledvalvesshouldbeinstalledonthetransferlinetothestoragetanks.Whenautomaticisolationisemployed,operatedbychlorinesensorsintheunloadingarea,thedetectorsystemneedstocloseboththestoragetankisolationvalveandthatonthetanker.Thepossibilityofliquidchlorinebeingtrappedbetweenclosedvalvesandtheneedforpressurerelief(seeparagraphs61-67)needstobeconsidered.
36 Itisalsogoodpracticetoprovide:
(a) protectionagainsttheweatheronfixedgantriesatunloadingpoints,egby windbreaksoroverheadcanopies;(b) storagespaceforconnectorsusedfortransferoperationssothattheycanbe keptdryandprotectedfromdirtandmoisturegettingin,andpossibleimpact damage;(c) storagespaceforemergencyequipment(egfilterrespirators,breathing apparatus,protectiveclothingandspareequipment)inasafelocationsothat theequipmentisreadilyavailableinanemergency;(d) adequatelightingandemergencylightingcoveringtheunloadingarea,andall escaperoutes;(e) sufficientmanuallyoperatedalarmstationstoenablewarningtobegivenin theeventofachlorineescape.Furtherdetailsonemergencyproceduresare giveninparagraphs247-263.
Deliveries of liquid chlorine by road tanker or ISO tank container
37 TheCarriageofDangerousGoods(CDG)byRoadRegulations199614andtheCDG(DriverTraining)Regulations199626apply.ForsafetyreasonsallUKroadtankersarefittedwithair-operatedshut-offvalvesforthepaddingair(seeparagraphs134-141)andthechlorinedeliveryconnections.Itisalsostronglyrecommendedthatthefollowingmeansofminimisingpotentialrisksareadoptedwhereverpossible:
(a) Provisionofaseparateandprotectedunloadingareaforthesoleuseof chlorinetankers(egbyerectingsideprotectionofthemotorway-typecrash barrier).(b) Restrictionbysuitablemeansofthespeedoftrafficonadjacentroads.(c) Unauthorisedaccessofvehiclesandpersonneltotheunloadingareashould beprevented,egbyplacingwarningbarriers,notices,moveablebarriersor roadcones,orclosinggateswhenthechlorinetankersareinposition.(d) Provisionofaninterlock(seeparagraphs39-41)systemtopreventcoupling ofliquidchlorinelinestothetankersandopeningofthedischargevalve untilthetankerisimmobilised.Inaddition,theair-operatedtankervalves
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shouldbeinterlockedwiththechlorinedetectionandshut-downsystem,orbe remotelyoperablefromtheemergencystoppoints.(e) Asystemofworkwherebyoneperson(thedriverforroaddeliveries)ispresent throughouttheunloading(seeparagraphs214-215,andAppendix6),anda secondispresentduringconnectionanddisconnection.Thesecondperson shouldbenearbyandavailablethroughoutunloadingtoprovidehelpon request.(f) Routingofchlorinepipeworkintheareatominimisetheriskofdamagefrom impactbythetanker,othervehiclesormobileequipment.
Tankerwaitingtoenterunloadingarea
38 Whereaseparateunloadingareacannotbeprovided,andtheunloadingpointisonafactorythroughroad,suchroadsshouldbephysicallyclosed(seeparagraph37c)toothertrafficduringthetransferofliquidchlorine.Yourriskassessmentwilldeterminewhetheradditionalmeasuresareneeded.
Interlocks
Thedischargearmandthepadding-airarmconnectorscannotbereleasedfromtheiranchorpointsuntilthebarriersarelockedinpositionandthemechanicalinterlockkeysremovedandusedtounlock
thearms
39 Interlocksshouldbeusedtopreventseriousincidents.Forexample,interlockscanbeusedtoensurethatthevehiclebrakesarefullyappliedbeforetheunloadingpipeisfinallyconnectedupandthetankervalveopened;or,abarrierontheunloadingplatformcanbeinterlockedtotheloadingconnector,sopreventinginadvertentmovementofatankerstillconnectedup.Alternativelythepressureintheunloadingpipecanactivateaflashingsigntoremindthedriverthatthetankerisstillconnected(thelattersystemmaybeappropriateataproducerplantoraconsumerplantwithalargethroughput).
40 Themanoeuvringnecessarytolocatearoadtankerpreciselyinrelationtoasolidpipeconnectormaymakeitmoredifficulttodeviseaninterlocktothehigheststandardofsecurity.Insuchcases,aninterlocktopreventaccessofothertankersisstronglyrecommended,andspecialattentionmustbepaidtothesystemofworkwhicheffectivelypreventsaccidentalmovementofthetanker,andtodrivertraining.Alternativelymovementdetectorsofthelightbeamandreflectortypecanbeusedandinterlockedtoclosetheisolationvalvesandsoundtheaudiblealarm.
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41 Interlocksmaybeusedtopreventsomereleasesduetooperatorerror.Forexampletoensurethatliquidchlorineisnottransferredtotheventabsorber,inadditiontoaprocedure(step9ofAppendix6)requiringtheclosureofthemanualventvalveontheliquidchlorinedeliverylinebeforestartingthetankerdischargeprocedure,theventvalveshouldbeinterlockedwiththedeliverypointorthetankeroff-loadingvalve.
Theairsupplytothetruck’sbrakeshastobedisconnectedbeforetheinstrumentair(neededtooperate
thetankerpaddingairandchlorinedischargevalves)canbeconnected
Deliveries of liquid chlorine by rail tanker
42 TheCarriageofDangerousGoodsbyRailRegulations199627apply.Itisstronglyrecommendedthatyouadoptthefollowingmeansofminimisingpotentialrisks.Yourriskassessmentwilldeterminewhetheradditionalmeasuresareneeded.
(a) Closethesidingstoothertrafficduringtransferofchlorinefromtankersto storage,bylockingthepoints.Alternatively,frictionbuffersorade-railermay beused.(b) Controlbysuitablemeansthevolumeandspeedofadjacenttraffic.(c) Closewarningbarriersand/orplacewarningnoticeswhenthechlorinetankers areinposition.(d) Provideaninterlock(seeparagraphs39-41)systemtopreventcouplingor uncouplingoftheliquidchlorinelines,unlessbarriersorwarningnoticesare inposition.Itisrecommendedthattheinterlocksystemextendstoensure thatappropriatepointsontherailsidingsarelockedandwheelstopsraised beforetransferofliquidchlorinecanstart.(e) Establishasystemofworkwherebyonepersonisresponsibleforthe wholeoperationofunloading,andasecondiswithincallduringconnection anddisconnection.Thesecondpersonshouldbeintheareaandavailable throughoutunloading.(f) Routechlorinepipelinesintheareatominimisetheriskofdamagefrom collisionbythetanker,othervehiclesormobileequipment.
Owingtotheverylimiteduseofrailtransport,therestofthisguidancefocusesonchlorinedeliverybyroadtanker.Whenrailtransportisused,thesamegeneralprinciplesforthesafehandlingofbulkdeliveriesofchlorineapply.
Flexiblecouplingstothetankerforliquidchlorineandpaddingair.Noticetheswiveljointandthespring
loadedpipeworksuspensionforthepaddingairandliquidchlorinelines
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CONNECTIONS BETWEEN THE TANKER AND THE FIXED LINES TO THE STORAGE INSTALLATION (see also paragraphs 134 -147)
43 Totransferliquidchlorinetostorage,itisnecessarytocoupletheliquidchlorineoutletlineonthetankertotheinletlinetostorage.Itisalsonecessarytoincreasethetankerpressurebyabout1.7barabovethatinthestoragetankbyconnectingasupplyofdrycompressedair,nitrogenorchlorinevapourtothetanker.Theassociatedpipework(seeparagraphs53-79)shouldbeassimpleaspossibletominimisetheriskofpotentialloss-of-containmentaccidents.
44 Connectionsforthetransferofliquidchlorinerequireverycarefulconsideration,astheyareapotentialsourceofloss-of-containmentleadingtoareleaseofchlorinetotheenvironment.Failureoftheunloadingconnectionscanresultfrominadequatedesign,poorweatherprotection,incorrectmaterialsofconstruction,inadequatepipeworksupport,improperuse,orinadequateinspectionandmaintenance.Therefore,youneedtoensurethatthedesignstandardsareadequate,thattestingandinspectionproceduresareregularlycarriedoutandthattheequipmentissatisfactorilymaintained.
Types of connection
45 Threetypesofconnectionareavailable:
(a) Flexiblecouplings(sometimescalledsemi-rigidloadingarms)have: (i)asolidconnectionpipewithswiveljointstofacilitateconnectiontothe tanker;and (ii)adegreeofflexibilitybuiltintothesupportsandhangertoallow movementwhencoupledup,ieacrankedfreelengthofpipeoracoiled pipe.(b) Flexiblehoses.(c) Articulatedarms.
Flexiblecouplingsarenormallyused,butflexiblehosesorarticulatedarmsmaybeusedbyagreementwith,orrecommendationof,thechlorinesupplier.
Flexible couplings (semi-rigid loading arms)
46 Flexiblecouplingsarenormallyconstructedfromsteelpipe.However,HastelloyC(notB)pipeisrecommendeduptothefirstisolationvalve.Thisoffersgreaterlifeinsituationswherethepipeisrepeatedlyexposedtoverysmallamountsofatmosphericmoisturebytheconnection/disconnectionprocess.Flexibilityisprovidedbyacrankedfreelengthofpipe(lessusuallybyacoil)toallowforverticalmovementofthetankerduringdischarge.Screwedconnectionsareusedfortheconnectionstotheroadtanker;screwedconnectionstoBS2128arecommonlyusedateitherendoftheflexiblecoupling.‘Swivel’jointsinthepaddinggaslineandtheliquidchlorinelinefacilitateconnectiontothetanker.Thesejointsaretightenedoncetheconnectionsaremade.Flangedconnectionsareusedforconnectingtorailtankers.
47 Pipinglocaltothetankerberthshouldnotbefixedforthefirst5-7mbutitneedstobesupported.Thesystemofsupportusedshouldensurethatthepipeworkiskeptabovetheheadroomrequiredbythetankerwhenitisbeingputinposition.Thesupportshouldalsoallowthepipeworksufficientverticalmovementtoaccommodatethatinthedeliveryvehicle’ssuspensionsystemduringtheunloadingoperation-typicallyabout150mm.Aminimuminternalpipediameterof25mmisrecommended.
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48 Thedesigncriteriaforflexiblecouplingsconstructedfrompipeworkaresimilartothoseforfixedpipework(seeparagraphs56-60).Wheretheconnectionsarescrewedconnections,thegasketshouldbeatrappedjointring,whichisrenewedateveryconnection(seealsoparagraph215).
Flexible hoses
49 Thedesignofflexiblehoses29,30shouldbeagreedwithyourchlorinesupplier.Theyrequiremorefrequenttestingthanflexiblecouplingsandtheirlifeisshorter,butpositioningoftankersiseasier.FlexibleMonelbraidedhoseconnectionsarenormallyconstructedupto50mm(2in)sizefortheliquidchlorinedischarge,and25mm(1in)sizeforthecompressedgasconnectiontothetanker.
50 Theoperatinginstructionscoveringunloadingshouldensurethatvisualinspectionandleaktestingoftheflexiblehosesiscarriedoutbeforecommencingtransferofliquidchlorine(seealsoparagraph215).
Articulated arms
51 Articulatedarms,withswivelledjoints(knuckles),areusuallyusedonhighvolumeinstallations.TheyshouldbedesignedtomeettherequirementsspecifiedintheEuroChlorpublicationGEST75/4431andcertifiedasmeetingthisoranequivalentstandard.Theyshouldbeoperatedandmaintainedasadvisedbythemanufacturer.Armsshouldbevisuallyinspectedfordefectsandtestedforgastightnesseverytimetheyareused.Suspectarmsshouldbeimmediatelywithdrawnfromserviceformaintenance.
52 Wherethesealsatknucklejointsarepurgedbyaflowofdry(dewpointlessthan-40oC)airornitrogen,thisgasshouldbecontinuouslysampledbyachlorinedetectorsystemwithanalarm.Anisolationvalvesuitableforusewitharticulatedarmsshouldbeattachedtothedischargeendofthearmtopreventairenteringthearmafteroperation.Itshould:
(a) ensureagastightsealwhenthearmisnotinusetopreventmoisturegetting in-anendcapshouldalsobeused;and(b) permittheventingdownofthearmanddepressurisationofanyconnection adapter.Thearmshouldbeventedaftereachoperationandpurgedwitha suitabledrygas.
Whenanarmisoutofservicethepurgegasshouldbemaintainedunderasmallpressure(eg0.5bargauge).
Youneedtokeeparegistershowingeachoperationandthequantity(egtonnes)ofchlorinetransferred.
PIPEWORK FOR LIQUID CHLORINE
53 Indesigningyourpipeworkyoushouldtakestepstoguardagainstthefollowingcausesoffailure:
(a) impact;(b) heating,egfire(resultinginareactionbetweenthesteelandchlorine);(c) severeinternalorexternalcorrosion;(d) overpressure(seeparagraphs61-67);and(e) erosionduetorelativelyhighliquidvelocitiesandinadequateinspectionand maintenanceprocedures.Liquidvelocitieslessthan2m/sarerecommended.
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54 Routingofpipeworkforliquidchlorineshouldnormallybeabovegroundandshouldbesuchastomaximiseprotectionfrommechanicaldamage,corrosionandfire.Aminimuminternaldiameterof25mm(1in)isrecommendedtoensureadequatemechanicalstrength.
Permanent pipework at the unloading point
55 Thepermanentpipeworkattheunloadingpointusuallyconsistsofthefollowinglines:
(a) pipeworkforpressurisingthetankerwithdryair,nitrogenorchlorine(see alsoparagraph134-147);(b) pipeworkforthetransferofliquidchlorinetostorage;and(c) pipeworkforinstrumentairlines,egtooperatetheremotelycontrolledvalves onthetanker.
Thesourceofcompressed‘padding’airneedstobeindependentfromthatsupplyingotherservices.Detaileddesignrequirementsforthepipeworkandfittingsaredescribedinparagraphs56-79.Thesystemforoff-loadingofliquidchlorineisdescribedinparagraphs134-147.
Design criteria for pipework transferring liquid chlorine to storage tanks or from storage to point of use
56 YourpipeworkwillbepartofapressuresystemandsubjecttotherequirementsofthePSTGCRegulations.23-25Itthereforeneedstobeproperlydesigned,fabricated,inspectedandtestedinaccordancewitharecognisedCode,egANSI/ASMEB31.332,33andshouldbesufficientlyrobustforallforeseeableconditionsofwork.
(a) Designpressure.Shouldnotbelessthan12bargauge(174psig), correspondingtoadesigntemperatureof+45oC.Anypartofthesystem whichmayoperateatahighertemperatureshouldbedesignedtowithstand thecorrespondingvapourpressure(seeAppendix2,FigureA2.1).
(b) Designtemperature.Shouldbelessthantheminimumatwhichthepipeis intendedtooperate,orthetemperaturetowhichitwillbecooledifliquid chlorineboilsoffatatmosphericpressure(-35oC).Thenormaldesignrange is-35oCto+45oC.Incertainuncommonsituationslowertemperatures arepossibleduetochlorinecoolingbelowitsboilingpoint,egwhenpurging systemswithdrygas-locationswhereliquidchlorinehascollectedmay cooltotemperaturesaslow-50oCduetoevaporativecooling.Yourchlorine suppliershouldbeabletoprovideadviceontheneedtodesignforsuchlow temperatures.(c) Materialsofconstruction.Careisneededinselectingsuitablematerials(see Appendix2).Seamlesscarbonsteeltubingisrecommendedforpipework. Allcomponentsofpipes,valvesandfittingsshouldberesistanttotheaction ofchlorinebetweentheextremesofoperatingtemperaturesandpressures. Originalmaterialcertificatesshouldbekeptthroughouttheplant’slife.(d) Corrosionallowance.1mm.(e) Radiusofcurvatureofanyformedbends.Threepipediametersminimum (weldelbowsmustbeusedwheretighterbendsarenecessary).Elbows,tees andreducingpiecesshouldbeforgedorhot-formedwithoutreductioninwall thickness.(f) Bolting.ShouldbedesignedtotherequirementsofBS4882.34
(g) Flanges.Thenumberofflangesshouldbelimitedasfaraspossibleand thoseusedshouldbetotherequirementsofarecogniseddesigncodeeg
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BS156035orASME/ANSIB16-5.36Steelusedforfabricationofflangesor weldedconnectionstothepipemustbecompatiblewiththatofthepipeitself.(h) Gaskets.Theuseofincorrectmaterialsforgasketscanbedangerous;ifin doubtyoushouldseektheadviceofyourchlorinesupplier.Rubbergaskets shouldneverbeusedforliquidchlorineservice.Allpackings,gasketsand diaphragmsshouldberesistanttotheactionofchlorinebetweentheextremes ofoperatingtemperaturesandpressures.Provenmaterialssuchasspiral woundMonel,Kel-ForAramidfibrearesuitable.Compressedasbestosfibre (CAF)gasketstoBS1832,37gradeAorO,preferablygraphite-treatedoneach facetofacilitatedismantling,aresuitableforjointsthatareexpectedto remaininserviceforseveralyearswithoutbeingdisturbed.Anyusedasbestos componentsshouldbecollectedanddisposedofsafely.Wherejointsare madeandremaderelativelyfrequentlyCAFisnotrecommendedfor environmentalreasons.Alternativejointingmaterialsuchasaramidfibre shouldbeused.Polytetrafluoroethylene(PTFE)toBS656438gradeUA1/1 maybesuitableprovidedthejointisofanencapsulatedtype(egaspigotted joint)topreventthePTFE‘creeping’.Someusershavefoundleadtobe suitableonsmalldiameterpipework(lessthan25mm).Whereavarietyof gasketmaterialsareusedjointsshouldbetabbedforeasyidentification.(i) Manufacturers’instructionsneedtobestrictlyadheredto.Avoidover- tighteningfittingsasthiscanresultinleaksduetothesubsequentfailureof thefixingnutsorpacking.(j) Lubrication.Normallyinassemblingpipeflanges,boltsandgaskets,no lubricantsarerequired.Wherelubricationisneeded,onlyfullyinertoilsand greasesrecommendedforchlorinedutyshouldbeused.Onnoaccountmust hydrocarbon-basedlubricantsbeusedastheyreactwithchlorineandmay ignite.Theheatgeneratedmaybesufficienttocauseachlorine-ironfire(see Appendix2)whichwouldresultinapipeworkfailureandareleaseofchlorine.
57 Thefollowingcontrolsshouldbeappliedduringconstruction:
(a) Stressrelief.Allfabricateditemsandbuttweldsshouldbestress-relieved beforefinalinspectionandtesting.(b) Inspectionandpressuretesting.Allweldspatter,scaleandotherforeign mattershouldberemoved.Allbuttweldsshouldbefullyradiographedor ultrasonicallyexamined.Allpipeworkshouldbepressure-testedinaccordance withthedesigncode.Wherehydrostatictestsaremadeitisessentialthatthe completepipingsystemisthoroughlycleanedanddriedtoadewpointless than-40oCbeforeintroducingchlorine.Alltracesofoil,greaseandsolvents mustberemoved(egwithsteamoraqueousdetergentsorboth)forthe reasonsstatedunder‘Lubrication’inparagraph56.Ifahydrostatictestis madeafterinstallationitwillbenecessarytochangeallgasketstoensure dryness.Appropriateleaktestswillthenberequiredtocheckthenewlymade joints.(c) Modifications.Anyextension,modificationorrepairstopipeworkshouldbe carriedouttoastandardatleastequivalenttotheoriginaldesignand constructioncodeincludingstressrelief,inspectionandtesting.
Protection of pipework
58 Youshouldinstallpipeworkconveyingchlorinesothatitis:
(a) protectedfromimpactbyvehiclesbydistanceorwithbarriers;(b) protectedfromfallingobjectsegnooverheadhoists.Canopyroofsforweather protectionshouldbeconstructedoflightweightmaterials;(c) separatedfrompipeworkcarryingcorrosiveorflammablematerialsorother sourcesofheat,egsteam-theseparationwilldependonthenatureofthe othermaterialandanestimateofthehazard;
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(d) adequatelysupported;(e) accessibleformaintenanceandinspection;(f) preferablyunlagged;and(g) regularlyinspectedunderanylaggingtodetectcorrosionduetofailureof weather-sealing.
Marking
59 Thechlorineareaneedstobeclearlyidentified,marked39-41-seealsotheDangerousSubstancesRegulationsinAppendix3-andsecuredagainstunauthorisedentry.ItisrecommendedthatchlorinepipeworkshouldbeclearlylabelledandpaintedyellowinaccordancewithBS171042(egto08E51-BS480043).TheHealthandSafety(SafetySignsandSignals)Regulations199644requireclearlabellingwheneverriskstoemployeescannotbeavoidedoradequatelyreducedbyothermeans;adviceisgivenintheassociatedguidance.45
60 Itisgoodpracticetomarkvalveswhicharerequiredtooperateinanemergency.Theyshouldbemarkedwithaclearindicationoftheirfunctionandthedirectioninwhichtheyopenandclose.Thesemarkingsneedtobeconsistentwiththemarkingsonanyflowdiagramsoroperationalinstructions.Valvekeysforoperatingtheemergencyvalvesshouldbelocatedneartothevalve.
PROTECTION OF LIQUID CHLORINE PIPEWORK AGAINST OVERPRESSURE
61 Trappingofliquidchlorinebetweenclosedvalves,followedbyariseintemperature,increasestheriskofoverpressure.Evenasmalltemperaturerisecancauseaveryhighhydraulicpressure,becauseofthehighcoefficientofexpansionofliquidchlorine(seeAppendix2).
62 Theriskofliquidchlorinebeingtrappedbetweenclosedvalvesisincreasedbythefollowingfactors:
(a) Isolationvalvesthatarecontrolledbydifferentoperators.Thismaybeaspecial riskwheretherearelonglinesorcomplexpipeworkbetweenunits.(b) Thesimultaneousclosureofautomaticallyoperatedvalvesthathavebeen installedforplantisolation.Thisriskshouldbeassessed.Insome circumstancesitmaybepreferabletoemployatleastonemanuallyinitiated remotelycontrolledvalve.
63 Youshoulddesignyoursystemandoperatingprocedurestominimisetherisksofoverpressurisation.Whenappropriate,pressurereliefdevicesshouldbefitted.
Provision of relief systems
64 Reliefsystemscomplicatepipeworkandintroduceotherpotentialhazards,andshouldingeneralbeavoided.However,ifthecapacityofyoursystemissuchthatreleaseofthechlorinepresentcouldleadtoaseriousincident,automaticmeansofreleasingexcessivepressureinthepipeworkneedstobeprovided.Itfollowsthattheconfigurationofthepipework,positioningofvalves,andvalve-closingmethods(seeparagraph62)havetobestudiedtoseewhetherthehazardcanoccur.
65 Pressurereliefsystemsshouldbedesignedtomeetyouroperatingconditions.Itisrecommendedthattheneedfor,andthedesignof,reliefsystemsisfullydiscussedwithyourchlorinesupplier.
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66 Acommonmethodofpressurereliefforprotectionofliquidchlorinelinesisviaaburstingdiscinstalledinaverticalteeonthepipework,dischargingtoasuitablecollectingsystem(seeFigure1)Thereliefvolumeofthepressurevesselshouldbeatleast20%ofthelinevolume.Anyexpansionvesselshouldberegisteredasapressurevesselforexaminationandrecordingpurposes.23
Figure 1 PressurereliefsystemforchlorinepipelinesNote:ValveAshouldbesecuredopenandvalveBclosed.Lockingmechanismsshouldbedefeatableifthevalvepositionneedstobechangedunder
emergencyconditions.
67 Thepressurevesselshouldbefittedwithasuitablealarmwhichoperatesasaresultoftheriseinpressureinthevessel,iftheburstingdiscleaksorruptures.Thevesselandlinecanthenbeventedtoprocess,ortothechlorineabsorptionsystemviaanormallylocked-closedvalve.Theheated‘bottle’systemoriginallyusedonolderinstallationsisnowobsoleteandnotrecommended.
VALVES
68 ItisstronglyrecommendedthatEuroChlorapprovedvalvesareusedonnewinstallations.Careisessentialinthechoiceofvalves(egseethepublicationsonvalvesinreference22)astheyhavetoberesistanttochlorineandabletocopewiththestressestowhichtheymaybesubjected.Thevalvebodyshouldpreferablybemadeofforgedsteel;castironisnotacceptable.Ifthevalvedesignissuchthatliquidchlorinecouldbetrappedwithinthebodywhenthevalveisclosed,provisionshouldbemadetoavoidexcesspressurewhichmaydevelopwithtemperaturerise.Inothersituationstheevaporationofliquidchlorinemaycauseoperatingtemperaturestofallbelow-35oC(seeparagraph56(b));thevalvesshouldbeselectedsoasnottofailifthisoccurs.Problemswhicharespecifictocoldortoliquidchlorinelimittheapplicationofcertaindesignsofvalve.
69 Theselectionoftheappropriatetypeofvalveforeachapplicationshouldbereviewedwithyourchlorinesupplierwhowillbeabletosuggestmanufacturersofvalveswhoseequipmenthasgivensatisfactoryservicewithliquidchlorine.Thiswillreducethepossibilityofunsatisfactoryvalvesbeingusedwhichwillrequirereplacementafterashortperiodandcouldbeapotentialsourceofhazard.
70 Valveswhichare‘permanently’open(egtopreventinadvertentisolationofpressurealarms),or‘permanently’closed(egemergencyventlines)shouldbesecuredinthesepositions.Thelockingmechanismsshouldbecapableofbeingbrokenintheeventofanemergency,egtheleadorplasticsealtype.
Pressure alarm gauge
Locked open valve
Locked shut valve
Vent line to processor to absorption plant
Pressure vessel
Chlorine pipeline
Bursting disc assembly
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71 Itisemphasisedthat,duringmaintenanceoperations,relianceonvalvesofwhatevertypeforisolationisinsufficient.Thedesignofthesystemshouldbesuchthatcompleteisolationofthesectionconcernedispossible.Suitablemethodsforachievingthisincludetheinstallationofspoolpiecesinthelineswhichcanberemovedandsubstitutedbyblanks,ortheinsertionofslipplates.46
Types of valve
72 Valvesofthefollowingtypeshavebeendevelopedforusewithliquidchlorineordrychlorinegasunderpressure:
(a) verticalglobevalves;(b) conicalplugvalves;(c) ballvalves.
73 Valveshavetobedegreasedusingsteamordetergentsandthencompletelydriedbeforeuse.Alltracesofanysolventusedshouldberemovedasitcouldreactwithchlorine(seeparagraph57(b)).Itisrecommendedthatafterthistreatmentthevalvesshouldbestoredinindividualgas-tightplasticbagsreadyforinstallationwhenrequired.
Vertical globe valves
74 Thistypeofvalveispreferredtoothertypesandisusedforisolationofliquidchlorinestocktanksorforlargeflowsofchlorinegas.Thebillet-globevalveisrecommendedforinstallationontheliquidchlorineoutletlinefromchlorinestoragetanks(seeparagraph96).Thegassealaroundthevalvespindleinglobevalvesmaybeformedbyapackedgland(preferablyusingringsorchevronsofPTFE)orbyabellowsseal.Thebellowsshouldbebackedupbyasecondaryglandseal.Globevalvesmay,withadvantage,befittedwithabackseatingarrangementwhichisolatestheglandfromlinepressurewhenthevalveisfullyopen.
Glandpackedglobevalve(typical Bellowssealedglobevalve Anglepatternglobevalvesizesavailable15mmto250mm) withpneumaticactuator. Hydraulicandelectrical actuatorsarealsoavailable
Conical plug valves (PTFE-sleeved)
75 Conicalplugvalves,PTFE-sleeved,aresatisfactoryforisolationofliquidchlorinelines,particularlywhenquickisolationmayberequired,buttheprimaryvalveonthestoragetankispreferablyaglobevalve.Rapidisolationcancausepressuresurgesandyouneedtoconsiderthesewhendesigningyourinstallation(seealsoparagraph79).
76 Conicalplugvalvesforusewithliquidchlorinerequireprovisionfortheavoidanceofproblemsarisingfromliquidchlorinetrappedintheborewhenthevalveisclosed.Ifthismakesthevalvesuni-directional,theyneedtobemarkedwithanindicationoftherequireddirectionofliquidflowtoensurecorrectinstallation.Gas-tightnessisprovidedbyaPTFEsleeveinsertedintothebodyofthevalveand
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byasupplementarysealalongthelengthofthespindlebetweenthevalvebodyandhead.Careshouldbetakentoavoidtheapplicationofsidethrusttothespindlesofplugvalves.
Ball valves
77 Thistypeofvalvecanbeusedforisolationinliquidchlorinelinesandshouldincorporatethefollowing:
(a) sphericalturninglimitedtoaquarter-turn;(b) straight-throughflanging;(c) PTFEseals.
78 Ballvalvesshouldbeavoidedwhenoperatingconditionsinvolvelargeandfrequenttemperaturechanges.Ifusedwithliquidchlorine,youshouldmakeprovisionforavoidingproblemsarisingfromliquidchlorinetrappedintheborewhenthevalveisclosed.Liquidtrappedintheballshouldbereleaseddownstreamviaasmallholeintheball.Ifthismakesthevalveuni-directionalitneedstobemarkedwithanindicationoftherequireddirectionofliquidflowtoensurecorrectinstallation.(Ballvalvesmaynotsealwhenthesealingpressureandthesystempressureareinoppositedirections).Theremarksaboutpressuresurgesinparagraphs75and79alsoapply.
Remotely controlled valves
79 Therateofclosureofanyactuatedvalveshouldnotbesorapidthatitcausesunduepressuresurgesinthesystem.Thestandardrateofclosureshouldbesatisfactoryforpipeworkupto50mmdiameter.Longrunsoflargerdiameterpipeworkmayrequirelowerratesofclosuretopreventliquidhammer.Youshouldseekadvicefromyourvalvesupplier.
STORAGE VESSELS (see also paragraphs 190-229)
80 Tominimisethedangerofover-fillingyourstoragevessel,itscapacityneedstobesignificantlygreaterthanthatofthelargestdeliveryvehicle.Thechosencapacitywilldependontherateofconsumptionandthefrequencyofdeliveries.InstallationofbulkstoragefacilitiesshouldbeconsideredonlyiftheannualconsumptionofchlorineissufficienttojustifybulksuppliesratherthanpurchaseofliquidchlorineindrumsorISOcontainers(seeparagraphs216-221).Aninstallationconsistingofsmallertankswhichwouldrequiresplitloadsisnotrecommended.NewsitesshouldinvolveHSEatanearlystage.
81 Inconsideringthenumberofindividualstoragetanksforarequiredtotalstoragecapacity,takethefollowingpointsintoaccount:
(a) Theminimumworkingcapacityofthetankshouldbeadequatetosafely accommodatetheworkingstockresidueandthemaximumforeseenunit delivery.(b) Ifcontinuityofsupplyisessential,atleasttwotankswillberequiredtoallow timefornecessaryinspectionsandtofacilitatemaintenance.Thisalsoprovides greaterflexibilityofoperation.(c) Increasingthenumberofstoragetanksleadstoanincreaseintheancillary plantandequipmentwithacorrespondingincreaseincomplexityofoperation.
82 Thedistancebetweenadjacentstoragetanksshouldbeadequatetoprovidegoodaccesstothetanksunderallcircumstances.Thisincludesthoseinwhichbulkyprotectiveequipment(suchasself-containedbreathingapparatus)isbeingused.
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Chlorinestoragevesselandbund.Notetheemergencystopbutton(oneofseveral)attheedgeof
thebund.
83 Allchlorinestoragetanksshouldbeinstalledinabundwhichisimpervioustoliquidchlorine.Thebundshouldbecapableoftakingthecontentsofthelargeststoragetankwithadequatefreeboardandasump.Ifthereisasub-divisiontogiveaseparatesectionundereachtank,eachsectionshouldhaveaslopingfloorleadingtoasump,whichmayservemorethanonetank.Sumpsshouldnotbeconnectedtothedrain.Provisionshouldbeincludedforremovalofrainwateroverthebundwall,notviathedrainorthroughvalvesinthebund.
84 Leaksofliquidchlorinearepotentiallymuchmoredangerousthanleaksofgaseouschlorine.Yoursystemthereforeneedstobedesignedsothatsourcesofleakageofliquidarereducedtoaminimum,egbyavoidingjointswhicharecontinuouslyexposedtoliquidchlorinesuchasbottomoutlets,seeparagraph88.
85 Theseverityofaleakisreducedbyloweringthepressurewithinthesystemandthereforeitisimportantthatfacilitiesfortransferringgaseouschlorinetoaconsumingprocessortoawaste-chlorineabsorptionplantareavailable.Youshouldalsoconsiderinyourriskassessmenttheneedforarrangementstotransferliquidchlorinefromaleakingtanktoanothertankwhichcanbeisolated.
86 Layoutofthechlorineareashouldbeplannedtoprovideallfacilitiesnecessaryforgoodhousekeepingandemergencyresponse.Chlorinestoragetanksshouldthereforebeerectedabovegroundlevel.Installationindeeppitsisnotrecommendedbecauseitincreasesthedifficultiesoftreatmentanddispersalofachlorineescapeandofaccessformaintenanceorrepair.Amplestoragespaceisneededformaintenanceandsafetyequipment,whichhastobereadilyaccessibleinanemergency.
87 Thermalinsulationofthestoragetanksisnotnormallyrequired.However,ifyourvesselisrelativelyclosetoafirehazardandlaggingisrequired,thematerialshouldbefire-resistant,chemicallyinerttoliquidorgaseouschlorineandresistanttoatmosphericmoisturegettingin.Periodicinspectionbeneaththelaggingisessentialwhencheckingforcorrosion.
Design criteria
88 Designcriteriafornewliquidchlorinestorageandexpansionvesselsareoutlinedbelow.
(a) Designpressure.12bargauge(174psig)minimum.(b) Designtemperature.Whenliquidchlorineevaporatesatatmosphericpressure itstemperaturefallsto-35oCandthereforetheminimumdesigntemperature shouldnotbeanyhigher,butlowertemperaturesarepossibleifevaporative coolingofliquidchlorineoccurs,seeparagraph56(b).Thenormaldesign rangeis-35oCto+45oC.
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(c) Fillingratio.Fillingratiosfortransportableliquidchlorinecontainersare detailedinBS535547forvarioussizerangesofmobilecontainersandfor differenttemperatures.Althoughthereisnoequivalentstandardforfixed tanks,forsimplicityafigureof1.25kgofliquidchlorine/litrecapacityis normallyusedtofixthemaximumleveltowhichthetankmaybefilledand thesettingchosenforthehighlevelalarm.Thisensuresthatthevolume ofliquidchlorinedoesnotexceed95%ofthetotalvolumeofthevessel,even foramaximumtemperatureof50oC.(d) Designcode.NewvesselsshouldbedesignedandmanufacturedtoBS 550048Category1(oranequivalentstandard).(e) Corrosionallowance.Minimum1mm.(f) Supportsandloadcells.Thevesselsupportsshouldbedesignedin accordancewiththedesigncodetopermitthermalexpansionor contractionoverthedesigntemperaturerange.Specialconsiderationmay benecessary(checkwithyoursupplier)whereloadcellsareusedfor determiningthecontentsofthetank,egcertaintypesofweighingdevice requiresecondarysupports.(g) Branches.Dimensionsshouldbelimitedtotheminimumrequired,particularly fortheliquidlines.Allbranchesshouldbemounted,wherepossible,onthe manholecoverorcovers.Manholeaccessshouldbeprovidedontopofthe vessel.Theopeningshouldpreferablybe600mmdiameter,butinnocase shoulditbelessthan460mmdiameter.Bottomoutletsshouldnotbe providedexceptwhererequiredforchlorinetransferbypumping.Any bottomoutletshouldhaveaninternalvalve,preferablyremotely-operable, plusaback-upisolatingvalve(seeparagraph97).(h) Bolting.ShouldmeettherequirementsofBS4882.34
(i) Gaskets.Useofincorrectmaterialsforgasketscanbedangerous,see paragraph56(h)forsuitablematerials.(j) Documentation.Regulation5ofPSTGC23-25requiresdesigners,manufacturers andsuppliersofpressuresystemstoprovidesufficientwritteninformation concerningthedesign,construction,examination,operationandmaintenance toenabletheregulationstobecompliedwith.Youmustretainthisinformation togetherwithanyCertificateofCompliance(egBS550048orsimilar documentationifotherstandardsarebeingused).(k) Marking.ThevesselmustbemarkedwiththedetailsspecifiedinSchedule4 ofthePSTGCRegulations.Allvalvesandpipeworkassociatedwithchlorine storagetanksshouldbelabelledandcolourcoded(seealsoparagraphs59 and60).
89 Paragraph88appliestonewsystemsdesignedandconstructedinaccordancewithacurrentstandard.Whereanexistingtankhasbeenprovidedinaccordancewithadifferentstandard,thesystemsshouldbeassessedaccordingtotherequirementsofthoseoriginalstandards.Inparticular,ifthevessel’ssafeworkingpressureislessthan12bargauge(174psig),thentheairsystempressure,reliefdevicesetcallhavetobealteredtosuit,andthedeliverysystemhastobearrangedsoastobecapableofworkingwithinthestoragetankconditions.Itisrecommendedthatsuchtanksarereplacedwithtanksmeetingtherequirementsofparagraph88.Thetimingofthereplacementshouldbeagreedwithyourchlorinesupplierandthecompetentpersonwhoexaminesyourvessels.
Connecting pipework and means for isolation of storage tanks
90 Themainconnectionstothestoragetanksare:
(a) liquidchlorineinlet;(b) liquidchlorineoutlet;(c) ventlinesandcompresseddrygaslines;
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(d) reliefsystem;(e) instrumentationandpressuregauges.
Connectionsatthetopofthechlorinestoragetank.Notethepressuresreliefsystemwithinterlocked
valves(seeparagraphs120to127)
91 Youneedtokeepthenumberofconnectionstoaminimumtoreducethepotentialsourcesofleakage.Thearrangementsofvalvesandpipeworkshouldbemadeassimpleaspossibletominimiseerrorsinoperation.Pipeworkisolationvalvesshouldbefitteddirectlytothebranchesonthemanlidorthetankitself.Thesystemshouldbedesignedandoperatedsothat,ifthejointsbetweenthevalvesandthestoragetanksfail,gaseouschlorineonlywillbereleased(seeparagraphs94-96).
92 Whenevertwovalvesareinstalledinseriesforisolation,itisrecommendedthatthesystemofoperationisplannedsothateachvalveisusedexclusivelyforadefinedperiodduringnormaloperation.Thisensuresthatbothvalvesarekeptinoperableconditionatalltimes.
93 AnapplicationoftheprinciplesinthissectionisshowndiagrammaticallyinFigure2.Notallinstallationswillbetothispattern,andvariations(someofwhicharedescribedinthetext)maybeappropriate.
Liquid chlorine inlet
94 Theliquidchlorineinletshouldnotnormallyextendfurtherintothetankthanthemaximumliquidlevel.Someolderinstallationsuseadip-pipeontheinletline.Toavoidliquidchlorineflowingbackifthefillinglinefails,holesaredrilledinthetopofthedip-pipesothatliquidwillnotsiphonback.Afulldip-pipemaybeprovidedasaninlettoavesselusedforbothimportationandexportation.Suchvesselsneedtobefittedwiththeadditionalcontrolsappropriatetoaliquidchlorineoutlet.Youshoulddiscussthecontrolsneededwithyourproposedchlorinesupplieratanearlystage.
95 Theisolationvalveonthechlorineinletline,directlyboltedtotheflangeonthestoragetank,shouldpreferablybeabilletorhighintegrityglobevalve.Aback-upvalveshouldbeprovided,whichmayberemotelyoperated.Ifamanualback-upvalveisused,theisolationvalveatthedeliverypointendofthepipeworkshouldberemotelyoperablefromtheemergencystoppoints.
Liquid chlorine outlet
96 Theremovalofliquidchlorinefromthestoragetankisbymeansofadip-pipe.Youthereforeneedtomakearrangementstopreventchlorinereleasescausedbythejointbetweentheisolationvalveandstoragetankfailing.Thisismost
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satisfactorilyachievedonnewplantbyuseofabillet-typeglobevalve,boltedtotheflangedbranchonthestoragetank,withthedip-pipescrewedintothebottomofthevalve.
97 Youneedtobackupthemainisolationvalvewithanadditionalvalvetoenableisolationifonevalvefailstoseateffectively.Dependingonthelocalpipingarrangement,provisionofoneormoreremotelycontrolledvalvesisrecommendedforemergencycontrol.Aremotelyoperatedvalvewhichisdesignedtogivepositiveisolationandwhichissuitablypositionedmayalsoserveasoneofthetwoisolationvalvesrequired.
98 Inaddition,itisstronglyrecommendedthatyouincorporatearestrictingorificeinthelinetotheconsumingplant.Theobjectofthisistoreducethesizeofareleasefromamajorfailuretoaslowasreasonablypracticable,ieappreciablylessthanthefull-boreflowthroughthepipe.Thesizeandlocationoftheorificeneedscarefulconsideration.Theorificeshouldnotbesosmallastoleadtoproblems,suchaspronenessoftheorificetoblocking,etc.Insomecasesitmaybepracticabletolimittheflowinthelinetothemaximumrequiredbytheprocess.Theorificeshouldnotbelocatedwithinthedip-pipebecauseoftheproblemofremovingtheliquidchlorinefromthetankintheeventofablockageoftheorifice.Insomeplants,theflowrestrictioncanbereplacedbytheremotelyoperableshut-offvalves(seeparagraph111)controlledbyasuitablefloworpressuresensor.Excessflowvalvesmaybeadvisableforlinesnormallytakingaflowofchlorinemuchlessthantheflowwhichcouldpassthroughinfaultconditions.Theyarenotsuitableforlinesinwhichthenormalflowrateishigh,andforwhichothermeansoffaultdetectionandflowisolationshouldbeused.
WIA
All UK road tankers have air-operated shut-off valves.Where practicable theseneed to be linked into theautomatic gas detection and shut down system(para 113 et seq) and /orbe remotely operable from the emergency stop points (para 37d)
Expansion vessel, paras 128-133see para 96
Storage vessel
H
The parts within the dotted line are repeated on every storage vessel
see paras119 -127
H'B' L
H
H
H
H
One of these valves shouldbe remotely operablefrom emergency stoppoints (para 97)
Uilage pipe (paras 107 and 108)
see para 99
Liquid CI to consuming plant(para 98)
2
2
Restricting orificeIf there is any risk of liquid from the vent being suckedback this line should includea preventive device (107, 174)
Vent absorber(para 171-189)
'A'
Dry air or dry Nsupply system atcontrolled pressure(para 134-141)
Valve A or B shouldbe remotely operablefrom emergency stop points (para 95)
Figure 2 AnexampleofthearrangementsfromchlorinetankerstoliquidchlorinestoragevesselsNote:Notallinstallationswillbetothispattern
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Vent and compressed dry gas lines
99 Ventlinesandcompresseddrygaslinescanbeconnectedtothestoragetankeitherthroughseparateinletsorthroughacombinedsingleinlet.Ineithercase,thevalvedirectlyconnectedtothestoragetankshouldbebackedupbyasecondvalve.
100 Thepreventionofsuck-backofaqueousliquorintotheventlinerequiressimilarprecautionstothosedescribedforvaporisers(seeparagraph161).Thepreventionofback-diffusionofmoistureisdescribedinparagraphs178-181.Theinlettothescrubbingsystemshouldincludealutepipe(barometricleg)topreventliquidfromthescrubbingsystementeringthechlorinesystem.
101 Theprocedurefortransferringliquidchlorinetothestoragetanksshouldprovidefortheventvalvetobeopenedslightlyattheendofdischargeforaboutaminute(seeAppendix6,paragraph17)toconfirmthatthetankhasnotbeensignificantlyover-filled,ieabovetheextra-highlevelalarm(seeparagraph104).Overfillingisindicatedbyfrostingontheventline,inwhichcasepressurereliefmaybenecessary(seeparagraphs102-132).
Relief system
102 Thespecialrequirementsfortheisolationvalvesonthepressurereliefsystemonthestoragetanksarecoveredinparagraphs123-133.
Instrumentation and chlorine detector systems
103 Controlinstrumentationonstoragetanksandelsewhereintheinstallationshould,whereverpossible,bedesignedtofailsafe.Electricalandelectronicequipment,unlessspeciallyprotectedagainstcorrosion,shouldnotbeplacedinareaswhereitcouldbeaffectedbygasleaks.
104 Storagetankcontents.Thequantityofliquidchlorineineachstoragetankispreferablydeterminedbyinstallingthetankonloadcellsoronaweighbridge.Loadcellsshouldberecalibratedwheneverthevesselisinspectedandpressure-testedwithwater.Accuracycheckscanalsobemadeagainsttheweightofchlorinesuppliedwheneveradeliveryismade,providedtheplantisoff-line.Itisrecommendedthatloadcellsarerecalibratedatintervalsnotexceedingthreeyears.Theweightofliquidchlorineineachtankshouldbeindicatedlocallyandmayberepeatedintheplantcontrolroom.Thecontents-measuringdevicesneedtooperateahigh-contentsalarminthecontrolroom(andoncomplexplants,possiblyanextra-highcontentsalarm)forsafetyreasons.Theextra-highlevelalarmneedstoberunindependentlyofthesystemgivingthehigh-contentsalarm,forreliabilityreasons.Whenfitted,itisrecommendedthattheextra-highlevelalarmisusedtoautomaticallyclosethetankinletvalveandthetankeroutletvalve,seeparagraph105.
105 Asanalternativetothemeasurementofthequantityofliquidchlorinebyweight,measurementbyliquidlevelinthetanksisalsoacceptable.However,selectionofsuitableequipmentisdifficultandyoushoulddiscussitwithyourchlorinesupplier.Suchdevicesarepreferredasthemeansoftriggeringtheextra-highlevelalarm.
106 Tolimittheliquidvolumeinthestoragetanktothatpermittedbythefillingratio(seeparagraph88(c)),anullagepipecanbescrewedintothebottomofthevalveontheventline.Thelengthofthisullagepipeneedstobeconsistentwiththefillingratiosothat,ifliquidchlorinerisesabovethecorrectlevel,itwillflowthroughtheullagepipewhentheventvalveisopenedattheendofadelivery(seeAppendix
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6)orinresponsetoanalarm.Theullagepipeshouldbecheckedwhentheroutineinspectionofthestorageinstallationismade.Alowtemperatureorotheralarm(seeparagraph107)shouldbefittedontheventlinefromthestoragetankstowarnifliquidchlorineisenteringtheullagepipeontheventline.
107Onasimpleinstallation,withgoodstaffingandattendanceatthetanks,anullagepipe(seeparagraph106)mayserveastheextra-highlevelalarm.Youneedtobeawarethatthismethodrequirestheventlinetobeleftopen,whichisnotnecessarilythecaseforalternativemethods,seeAppendix6.Ifahighcontentsalarmisignoredduringfillingofthetank,theliquidreachesthebottomoftheullagepipeandevaporatesinthevent-lineabovetheventcontrolvalve,producingfrostingofthepipe.Anullagepipethereforepresentstheriskofliquidchlorinebeingpassedtothescrubberunlessthelinecontainsaknock-outdevicefittedwithahighlevelalarm.Aknock-outpotintheventlinewithlevelalarmsisalsorecommendedforotherreasons(seeparagraph157).Theminimumprotectionfittedshouldbearestrictionorificeplate(seeparagraph98)andalowtemperaturealarm.
108 Ullagepipesarenotrecommendedforcontentsindicationonnewinstallations;insteadanextra-highlevelalarmonthetankshouldbeinstalled,seealsoparagraph105.
109 Alowcontentsalarmmaybeusefulforoperationalreasonsandmayhavesafetyimplicationsif,egtherecouldbeprocessupsetsonfailureofchlorinesupplyorpassageofpaddingair(seeparagraph226)intoadownstreamvessel.
110 Storagetankpressure.Thepressureinthechlorinestoragetanksisusuallymeasuredbygaugesspeciallydevelopedforusewithliquidchlorine;thesehavesilverortantalumdiaphragms.Beforeuse,thegaugesneedtobecompletelydegreased(egwithsteamand/oradetergent),driedandalltracesofsolventremoved,andbepressure-testedusingonlyclean,dry,oil-freecompressedair.Thepressuregaugesmaybefittedwithswitchestogiveanalarmifthepressureexceeds,orfallsbelow,apre-setvalue.Alternatively,pressureswitchesmaybeusedtogiveanindependentsignalforthehighandlowpressurealarms.
111 Wherereferenceismadetofloworpressuresensors‘operating’valves(seeparagraph98)thereisachoicewhethertheoperationisautomaticorviamanualintervention(seeparagraph62(b)).Attheextremes,operationshouldbeautomaticinanunstaffedplant,andmaybeindirectinawell-instrumentedplantwithacontinuouslystaffedcontrolroom.
112 Equipmentassociatedwiththeautomaticpressurereliefsystemisdescribedinparagraphs120and128-133.
Chlorine detectors and alarms
113 Theairinabuildinghousingchlorinestoragetanksshouldbecontinuouslymonitoredusingproprietarychlorinedetectorsystemstogivewarningofchlorineleakage.Detectorsarestronglyrecommendedinbuildingswhicharenotcontinuouslystaffedtoprovideearlywarningofleaks,allowingpromptremedialaction.Foroutdoorinstallations,thevalueofdetectorsystemsneedstobeassessedbyconsideringfactorssuchasthesizeoftheinstallation,thestaffinglevelsandtheresponsetimesachievable.Ondetectingaleak,thedetectorshould:
(a) raiseanaudiblealarminacontinuouslystaffedareaorcontrolcentre;(b) activateaudiblealarmsintheaffectedarea;(c) operatetheautomaticisolationvalves;and(d) controlthemechanicalventilation,iffitted.
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114 Audiblealarmsneedtohaveadistincttone.Inaddition,warninglightsoftheamberflashingortrafficlighttypemaybefittedoutsideeachchlorinebuilding.Whereappropriate,egatlarge,remoteorsensitivesites,alarmsshouldbeconnectedtoatelemetrysystemtoprovidewarningatastaffedcontrolpoint.Thecontrolpointshouldbeabletoisolatethechlorinesupply,preferablyviaaremotelyoperablevalvefittedtotheoutletofthetank.
115 Chlorinedetectorsmaybeplacedinstorageandplantareas.Themanufacturerorsupplierofthesystemshouldadviseonthebestlocationforthesensors;typicallysensorsaremountedbetween0.3mand0.5mabovegroundlevel,andattheoutletfromfumescrubbers.Forindoorinstallations,sensorsmayneedtobelocatedinorneartheentrancetoductscarryingchlorinepipework,andtheairintakestoextractorfans.Whereforcedventilationsystemshavebeeninstalled,thedetectorshouldbelocatedattheoutletofthesystem;wherethisisnotreasonablypracticablethedetectorshouldbeplacednearthestorageanduseareas.
116 Detectionsystemsshouldprovideacontinuousmonitoringfunctionwhenchlorineisinstorageorinuse.Chlorinegassensorsshouldbetestedregularlyinaccordancewiththemanufacturer’sinstructionstodemonstratethatthedetectoranditsassociatedcircuitsarefunctioningcorrectly.Arecordofsuchtestsisrecommended.Thedetectionsystemshouldoperatethealarmcircuitsintheeventofpowerloss,sensorfailure,orlowconditionofthestandbybatteries.Allalarmrelayoperationsshouldbeprotectedbyabatteryback-upfacility.
117 Thedetectorsystemshouldactivatethelowlevelalarmatachlorineconcentrationof1-5ppm.Lowersettingsareliabletoactivatethesystemateverytank-fillingoperation,unlessadurationrequirementisalsoimposed.Forexample,somecompaniessetthelowlevelalarmat0.5ppm,butrequirethesensortoregisterthisconcentrationforatleast30seconds,toavoidspurioustripsofthealarmsystemduringfillingoperations.Forindoorinstallations,thelowalarmlevelshouldactivatetheventilationfan,opentheintakelouvers,andactivatelocalaudioalarmsandanyremotetelemetryalarm.
118 Multi-stagedetectorsystemsaresometimesusedtogiveanindicationoftheseverityofthemalfunctiontopersonneloutsideachlorineroom.Itissuggestedthatthehighlevelalarmoperatesataboutthreetimesthelevelofthefirst-stagealarm,ie3-15ppm,dependingonthedurationthatthesensorneedstoregisterthislevel.However,somecompaniessetthehighlevelalarmat2ppmwitha30seconddurationrequirement.
Onactivationofahighlevelalarmtheventilationsystemshouldbeshutoff,theauto-shutdownsystemactivated(wherefitted)andthehighlevelalarmsounded.Thetoneofthealarmatlowandhighlevelsshouldbedifferentandoperatorstrainedtorecognisethedifferenceandhowtorespondineachcase.Localalarmsmaybesupplementedbytelemetrylinkstocontrolrooms,whereappropriate.Theresponsetoalarmsiscoveredinparagraphs247-263.Somesensorscanbedamagedbyhighchlorineconcentrations;detectorsystemsshouldthereforebecheckedafteranyhighlevelalarm.
PROTECTION OF STORAGE VESSELS AGAINST OVERPRESSURE
119 Highpressureontheliquidchlorinestoragetankisindicatedbyahighpressurealarm(paragraph110).Overpressureintheliquidchlorinestoragetankscanresultfromover-fillingorexcessivepaddingpressure.Over-fillingwithliquidchlorineisindicatedbyalarmsontheweighsystemusedtodeterminetheliquidchlorinecontentofthestoragetanks(paragraphs104-109).Overpressureonthecompressedairornitrogensupplytothestoragetankispreventedbythe
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installationofareliefvalveonthesupplysourceofthecompressedgas.Thesupplysourceshouldbewellupstreamofthetankandseparatedfromitbyisolationvalves(paragraph139).
Relief system
120 Thestoragetanksneedtobeprotectedagainstoverpressurebyasuitableautomaticpressurereliefsystemwhichissettooperateatapressurebelowthedesignvalue.Thepreferredpressurereliefsystemconsistsoftwoburstingdiscsplacedbacktoback.Aburstingdiscfollowedbyareliefvalvemayalsobeused,butisalwayssubjecttotheriskofcorrosionofthereliefvalve.Protectionofthereliefvalvefromcorrosionmustbecarefullyconsiderediftheburstingdiscreliefvalvesystemisused.Theuseofreliefvalvesaloneisnotrecommendedbecauseofthecorrosionorblockagewhichcouldoccurifareliefvalvewereleftcontinuouslyexposedtochlorine.Whicheversystemisused,youshouldprovideapressurealarm/indicatorbetweenthetwodiscsorbetweenthediscandreliefvalve(seeparagraph133).Inthelatterarrangementitisgoodpracticetoremoveandoverhaulthereliefvalvewhenevertheburstingdiscisreplaced.
121 Thedischargelinefromthepressurereliefsystemnormallyentersaclosedexpansionvessel(exceptinafewspecialisedarrangements).Anypressureintheexpansionvesselorbetweencomponentsinthereliefsystemreducestheprotectiongiventothestoragevessel(seeparagraphs85,128-133).Specialreliefarrangementsareusuallyrequiredwhenthereisasignificantriskofoverpressurefromcontinuouspressuresourcessuchasradiantheatorbypumpingchlorine.Underthesecircumstancesreliefintoaclosedexpansionvesselmaybeinadequate.Reliefarrangementsbasedonreliefvalvesintoan‘open’system(egaventscrubber)maybepreferabletoburstingdiscs,asthevalvesreseatoncethesourceofoverpressurehasbeenremoved.Thisarrangementisnormallyonlyfoundonlargerinstallations;youshouldconsultyourchlorinesupplier.
Bursting discs
122 Burstingdiscs(whicharedesignedtofailatorbelowthedesignpressureofstoragetanks)arecommonlymadeofnickel,althoughtantalum,silverorothercompatiblematerialsmaybeused.Uncoatedgraphiteisnotrecommended.DiscsshouldcomplywithBS291549(orequivalentstandard)andshouldbecarefullyselectedfortheoperatingtemperaturerange,astherupturepressureistemperature-dependent.
Arrangements for relief systems
123 Onsimpleinstallations,suchasthosewithasinglestoragevesselandassociatedexpansionvessel,asingleburstingdiscsystemwithoutanyisolatingvalves,installeddirectlyonthestoragevessel,maybeacceptable.Inpractice,however,itismoreconvenienttoinstallavalvedsystemtoallowreplacementofdiscsunderacontrolledsystemofwork,withoutneedingtocompletelyemptyandpurgethesystem.Wheretwoormorestoragevesselsshareanexpansionvessel,thereliefarrangementsshouldallowpromptreplacementofdiscsandventingofallexcesspressureoutoftheexpansionvessel.
124 ThepreferredarrangementsareshowninFigures3and4andshouldbeusedonallnewinstallations.Theisolatingvalvesmaybemechanicallyinterlocked(recommendedfornewinstallations)sothatonepairofdiscsisalwaysoperative,ortheisolatingvalvesmaybeindividuallylocked.TobeeffectivetheburstingdiscsneedtobeofthesimpledomedunsupportedtypewiththeconcavesidefacinginthedirectionsshowninFigures3,4,and5.Theidentifyingtagsshouldbeleftattachedtoeachdiscsothattheycanbeidentifiedashavingbeeninstalled
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correctly.ExistingolderinstallationsusingthearrangementshowninFigure5shouldreplaceitwithapreferredarrangement(Figure3or4)whenmajormodificationsareinhand.
125 Thevalveswhichremainopenmustpermittheoperationaldevicestodischargeattherequiredratetoanexpansionvessel.Pipeworkbeforetheisolatingvalvesshouldbeasshortandsimpleaspossibletominimisetheriskofchlorineleakagefromjointsandpipework;theisolationusingvalvesbeforetheburstingdiscsshouldpreferablybefitteddirectlyonflangedconnectionsonthemanlidofthestoragetanks.
Figure 3 Pressurereliefsystem(preferred Figure 4 Pressurereliefsystem.Doublearrangement).Doublestreamwithinterlocked streamwithlocked-openvalvesvalves
Figure 5 Pressurereliefsystem.Singlestreamwithlocked-openvalves
126 Yourproceduresfordealingwithafailureofaburstingdiscshouldbeclearlydefined.Basethemontheprinciplethatatnotimeshouldpressuresbeyondthedesignrangebeallowedtodevelop(seealsoparagraph127).
127 Atanyinstallationwherea‘locked’-openisolatingvalveprecedesaburstingdisc,asafesystemofworkshouldbedefinedtopreventunacceptablepressuresfromanysourceoccurringinthevesselwhiletheisolatingvalveisclosed.Theproceduresneedtocoverthesaferemovalofthevesselfromnormalservice,stabilisingthepressure,changingtheburstingdisc,ventingtheexpansiontankandreturningthevesseltonormaluse.Suchsafesystemswillvarywithplantdesignbutshould:
To expansion vessel
Mechanicalinterlock
Bursting discs Bursting discs
Pressure alarm gauge Pressure alarm gauge
(Test connections for pressure gauge not shown)
To expansion vessel
Locked open valve
Pressure alarm gauge
Locked open valve
Bursting discs
To expansion vessel
at least one lineneeds to be locked open
Locked valves
Locked valves
Bursting discs Bursting discs
Pressure alarm gauge Pressure alarm gauge
(Test connections for pressure gauge not shown)
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(a) beinawrittenform,unambiguousandreadilyavailable;(b) includeapermit-to-worksystem;(c) beincludedinplantpersonneltrainingprogrammes;(d) beproperlysupervisedwithresponsibilitiesclearlyallocated;(e) beregularlyupdatedandperiodicallysubjectedtoHAZOP50review, particularlywhenplantdesign,operatingproceduresormanagementsystems aremodified;and(f) berigidlyadheredto.
Expansion vessels
Expansionvesselmountedinabund
128 Thedesignrequirementsfortheconstructionoftheexpansionvesselaresimilartothoseforthestoragetanks;thecapacityoftheexpansionvesselshouldbeatleast10%ofthelargeststoragevessel.
129 Theexpansionvesselshouldbecapableofbeingventedmanuallytoanabsorptionsystem;theventvalveisnormallylockedclosed.Controlledventingshouldbethroughasuitableflowrestrictiondevice,eganorificeplatetopreventoverloadoftheabsorptionsystem.
130 Theexpansionvesselshouldbeprovidedwithapressure-sensingdevicewhichgivesanalarmifpressurebuildsupinthevessel.Thealarmsystemneedstobecapableofbeingtestedregularlytoensurethatitisoperable(seeparagraph133).
131 Arrangethecompressedairornitrogenconnectiontotheexpansionvesseltoavoidthepossibilityofinadvertentlypressurisingthevessel.Thismaybeachievedbyphysicaldisconnection,isolatingblankingplates,orbydoubleblockvalvessupportedbyasafesystemofwork.Ifanexpansionvesselservesmorethanonestoragevessel,makearrangementsforpromptresponsetoapressurealarmsignalfromit.
132 Whiletheriskoftheexpansionvesselitselfbeingover-pressurisedwithchlorineisminimalbecauseoftheprecautionsdescribedinparagraphs128-131,youshouldestablishproceduralormechanicalmeanstoensurethatthiscannotoccur.
Pressure alarms
133 Thereshouldbeahigh-pressurealarmoneverystoragevessel,andanadditionalpressureindicator/alarmateachimportantsafetylocationonthereliefarrangement.Thismeansthatoneadditionalpressurealarmmaysufficeoneachstoragevesselthathasitsownexpansionvessel,andthatalarmmaybeeitherinthereliefline(ifthereisasingleburstingdisc)orontheexpansionvessel.Whenoneexpansionvesselservesseveralstoragevessels,thereshouldbeanadditional
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pressurealarmwithineachreliefassemblyandalsooneontheexpansionvessel.Testalarmsregularly(atleastmonthly)bygasinjectionormovingcontacts.
ARRANGEMENTS FOR UNLOADING OF LIQUID CHLORINE FROM ROAD TANKERS TO STORAGE
Unloading Using Dry Compressed Air or Dry Nitrogen
Aircompressorunit
134Therecommendedsystemfortransferringliquidchlorinefromchlorinetankerstostoragevessels,by‘padding’withdryairordrynitrogen,isoutlinedinFigure2andinAppendix6whichprovidesasoundbasisfordevelopinglocalprocedures.Detailedrequirements,whichsupplementinformationgiveninprevioussections,arereviewedinparagraphs135-147.Youneedtoagreeyourarrangementswithyoursupplieranddesignthemtominimisetheriskofoverpressure.
135Aseparateandindependentdrycompressedairornitrogensystemshouldbeusedforchlorineduty,tominimisethepossibilityofback-diffusionofchlorinewhichcouldleadtodangerousconditionsinotherair-consumingunits,particularlyinstrumentation.Compressednitrogenmaybeproducedinaliquidnitrogenevaporationunit.
136 Ifyouusecompressedair,yoursupplyneedstobeoil-freeandhaveadewpointbelow-40oC.Normally,airshouldbecompressedtoaround10bargaugeusingatrulyoil-freecompressor(1.5m3/minfreeaircapacity);ifanoil-lubricatedcompressorisuseditmustbefittedwithanoilfilterwhichmustberegularlymaintained.
Hygrometeralarm.Atthisinstallationthecompressedairdewpointislessthan-60ºC
137Thecompressedairiscooledtoremovepartofthemoisturecontentandfinallydried,usingaregenerative-typedryingsystem,toadewpointbelow-40oC.Thedewpointshouldpreferablybemonitoredcontinuouslyusingamonitorprovidedwithanalarmthatgiveswarningifthedewpointexceedsapre-setfigure.
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Itisimportanttorechargeorregeneratedryingagentsaccordingtotheequipmentandchlorinesuppliers’advice.
138Aguardtower,filledwithanhydrouscalciumchlorideorothersuitablematerial,maybeinstalledaftertheregenerativesystemasafurthersafeguard.Forsmallinstallationsadrieraloneusinganhydrouscalciumchlorideorotherdryingagentmaybeadequate,providedthatproperchecksontheconditionofthedryingagentaremade.
Supply of dry padding gas to the system
139 Thecompresseddryairordrynitrogenshouldbestoredinapressurereceiver.Thisshouldbefittedwithareliefvalvesettooperateatthechlorinestorageplant’ssafeworkingpressureor10bargauge,whicheverislower.Fromthereceiverthegasshouldpassthroughanon-returnvalve,orapressure-actuatedshut-offvalve,followedbyareducingvalvetogiveasupplyatthepressurerequiredforunloadingthetankers.Thissupplywillalsobesuitableforotherpurposesonthechlorineplant,suchasdryingoutorpurgingofpipelinesandvesselsprovidedprecautionsaretakentopreventbackflowofchlorineintotheairsystem.Pressuregaugesshouldbeinstalledupstreamanddownstreamofthepressurereducingvalvesothatcheckscanbemadethatthepaddinggaspressureisgreaterthanthechlorinepressure.Itisimportanttoprovidesafeguards23-25toensurethatexcessivegaspressurescannotbeappliedtothechlorinesystem.Thismaybeparticularlyimportantifthepaddinggasissuppliedfromhighpressurecylinders.
140 Theliquidchlorinedischargelineonthechlorinetankershouldbeconnectedtothepermanentpipeworkattheunloadingpoint(seeparagraphs43-55).Thepipeworkconnectingtheunloadingpointtotheliquidchlorinestoragevesselsshouldbereasonablyshort(seealsoparagraphs(53-60).Ifitisnecessarytousealongliquidchlorinelinetostorage,youmustconsidertheneedtoprotectthislineagainstoverpressure(seeparagraphs61-67).
141 Apressuregauge,aventlinetotheabsorberandaconnectionfordrycompressedgasshouldbeinstalledclosetotheendofthepermanentpipeworkattheunloadingpoint,withthenecessaryisolationvalves,asdetailedinFigure2.
Unloading using chlorine gas pressure
142 Liquidchlorinemaybetransferredfromthechlorinetankerstothestoragevesselsbypaddingwithdrychlorinegas.Thegasisnormallytakenfromoneofthestocktanksbutthisshouldpreferablynotbetheoneintowhichthetankerisbeingunloaded.Thesupplyofdrychlorinegasattherequiredpressuremaybeobtainedbyre-compressingchlorinevapourfromastoragetankorbyvaporisationofliquidchlorine.Asourceofdry,compressed,oil-freeairornitrogenisstillrequired,fordryingoutandpurgingthesystem.
Use of re-compressed chlorine vapour
143 Selectionoftheappropriatecompressorforre-compressionofchlorinevapourrequirescarefulconsiderationtoensurethattheequipmentcanoperatesatisfactorilyonanintermittentbasis.Diaphragmcompressorsordrycarbonringreciprocatingcompressorsaresuitableforthisdutyprovidedthatmaintenanceiscarriedoutonaregularbasis.
144 Diaphragmcompressorsshouldusestainlesssteeldoublediaphragmswithinertfluidbetweenthem.Drycarbonringcompressorsshouldpreferablybepurgedwithdryairafteruse,toavoidproblemsresultingfromresidualchlorineinthe
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compressorleakingfromshaftglands.Duringoperationofthecompressor,theshaftglandsshouldbepressurisedwithdry,compressed,inertgas.
145 Ifcoolingofthecompressorbodyisrequired,thisshouldpreferablybeaccomplishedbyaircooling.Ifjacketcoolingisnecessary,thisshouldbeachievedbycirculationthroughanexternalheatexchangerwithprovisiontodetectleakageofchlorineintotheheatexchangefluid.Directwatercoolingshouldbeavoided.
146 Thecompressorneedstobefittedwithabypasssothatthechlorinecanberecycleduntilitstemperatureisraisedsufficientlytopreventliquefactioninthedeliverylines.Thetemperatureofthechlorineshouldbemonitoredusinganindicatorwhichisfittedwithanalarm,settosoundifitexceeds90oC.
147 Apressurereliefsystemonthecompressordeliverylineshouldalsobeprovidedtopreventthedeliverypressureexceedingapre-setfigure(seeparagraph139).
CHLORINE VAPORISERS
148 Vaporisers(alsoknownasevaporators)convertliquidchlorineintogas.Amajoruseofchlorinevaporisersisinwatertreatment,tocontrolweedandalgaeincoolingwaterandtosterilisedrinkingwater.Theseunitsarefrequentlysuppliedaspartofapackagewithotherdosingoranalyticalequipment.Vaporisersarealwaysrequiredwithafixedordemountablebulktank,toobtainaregular,steadysupplyofgastoprocess.Thedrawingofgasfromthevapourspaceofabulktankisunsatisfactoryandunsafe.Thereistheriskofprocessliquidspassingbackintothetank,irregularityofsupplyandthepossibleaccumulationoflessvolatile,dangerousimpurities,suchasexplosivenitrogentrichlorideinthetank.51Thesafehandlingofchlorinecontainingnitrogentrichlorideisdiscussedelsewhere.52
Types
149 Therearefourmaintypesofvaporiser(seealsoAppendix7):
(a) Verticaltubebundle.Theseresembleordinaryheatexchangers,usuallywith thechlorineinthetubes.Alternativeformatsincludethecommonvaporiser usedinwatertreatment(acylinderwithadip-pipeliquidchlorineinlet immersedintheheatingbath)orashellandtubeheatexchangerwiththe chlorineontheshellside.Abayonetvaporiserisverysimilar.(b) Coil.Thechlorineisevaporatedinacoilofsteeltubingrunninginsideawet steambathorawaterbathheatedbysteamorelectricity.(c) Concentrictube.Theheatexchangesurfaceisatube,typicallyfourinchesin diameter,surroundedbyaheatingjacket.(d) Kettle.Kettleevaporatorsareusedonlargecapacitysystems.Theycontaina heatersystem(usuallyatubebundleofhotwaterorheatedfluid-notsteam) passingthroughavesselcontainingliquidchlorine.Kettleevaporatorsdonot superheatthechlorinevapour,othersystemsdo.
Coilinbathvaporiserheatedbylowpressuresteam
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Coilinbathvaporiserheatedbylowpressuresteam
Regulation of throughput
Self-regulating vaporisers
150 Insometypesofvaporisertheliquidchlorineisfedinatthebottomandgasisdrawnoffviaacontrolvalveatthetop.Whendemandishigh,theliquidchlorinelevelrisesinthecontainer,andagreaterheatexchangesurfaceareaispresentedtotheliquid.Whendemandislow,thegreatervapourpressureatthetemperatureoftheheatingmediumdrivestheliquidchlorineoutofthevaporiserbackintothestoragevesselandtheevaporationratefalls.Thissystemisusuallyapplicabletovaporiserswitharelativelysmallchlorinecapacity,ieverticaltubebundles,coiltypesandconcentrictubetypes.Bayonetvaporiserscanbeusedforhighvaporisationrates.Onwatertreatmentplantsaself-regulatingvaporiser,withanelectricallyheatedwaterbathisusuallyused.
Constant level vaporisers
151 Othertypesofvaporisers,usuallyfoundonlyinlarge-capacityplants,sacrificecertainadvantagesoftheself-regulatingtypestoachievemuchlargervaporisationrates.Thesevaporisersrequireseparateinstrumentationandcontrolarrangementstoprovideaconstantlevelofliquidchlorineinthekettleorshellwithhighandlowlevelalarms.Insuchtypes(wheretherecanbepartsoftheliquidchlorinepoolwhicharenotwell-mixed),thereisagreatertendencytoconcentratethelessvolatileimpuritiesthaninaself-regulatingvaporiser.Aseparatepurgeandvaporisercircuitmayberequiredtodealperiodicallywiththeresidues.Thedesignandoperationoftheselarger-capacityvaporisersisaspecialisedtopic,andrequiresconsultationbetweentheuser,thedesigner,andthechlorinesupplierastheriskofnitrogentrichlorideenrichmentandsubsequentexplosionisincreased.51,52Youshouldinvolveyoursupplierwhenassessingthisrisk.
Methods of heating
152 Themethodsofheatingthevaporisershouldminimiseboththeriskofcorrosionandvaporiserfailure.Theseinclude:heatingwithhotwater;heatingwithlowpressuresteam;andusingclosedcircuitheatingwithheattransferfluidsotherthanwater.Directelectricalheatingshouldnotbeusedbecauseoftheriskoflocaloverheatingandchlorine/ironfires(seeparagraph158andAppendix2).
(a) Heatingwithhotwater.Thisisthemostfrequentlyusedmethod;thenormal workingtemperature(60-70oC)iswellbelowthatatwhichanysignificant reactionofcarbonsteeloccurswithdrychlorine.(b) Heatingwithsteam.Thesteamshouldbesaturatedanditspressureshould belimitedtolessthan1bargaugetoavoidoverheating,particularlyifthe vaporiserismadeofmildsteel.Anysmallleaksofchlorinetothewaterside ofhotwaterorsteamtypesleadtoveryrapidcorrosionofthesteelbymoist chlorine(seeparagraph169).Steamsystemsmustmeettherequirements
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ofthePSTGCRegulations.23-25Thegreaterflexibilityofsteamheatingisuseful onplantsusingchlorinegasathighoratveryvariablerates.(c) Heattransferfluids(otherthanwater).Electricalorsteamheatcanbeapplied toaheattransferfluidwhichisrelativelyunreactivetowardschlorine.The availablefluids(eghexachlorobutadiene)arethemselveshazardous,sothat thehazardsofusingwaterasheattransfermediumareinpracticeaccepted, withsuitablesafeguards.
General installation
153 Thevaporisershouldbeinstalledinthestorageareaorinanadjacentspaceascloseaspossibletothechlorinestoragetanksinordertokeeppipelinescarryingliquidchlorineshort.Longpiperunswillrequirepressurerelief(seeparagraphs61-67).Changeoverofliquidchlorinesupplyfromonestoragetanktoanothercanaffectoperatingconditionsinthevaporisersystemandanysuchdifficultieswillbereducedifthespacingisnottoogreat,eglessthan5metres.Nevertheless,thespacebetweenthevaporiserandthestoragesystemshouldbesuchastoallowadequateaccessforemergencyactionintheeventofanincidentatthevaporiser.
Hazards
154 Thequantityofchlorineinachlorinevaporisersystemisrelativelysmallcomparedwiththatnormallycontainedinthemainchlorinestoragetanks.Nevertheless,thesystemdesignshouldbesuchthatfailureofequipmentcanbedetectedandrectifiedquicklyandthatanyconsequentreleaseofchlorinetotheenvironmentisminimised.
155 Potentialhazardsassociatedwithchlorinevaporisersinclude:
(a) Pinholeleaksleadingtorapidcorrosionandincreasedlossofchlorine.(b) Rapidcorrosion,ifanymoistureisallowedintothechlorinesystem.(c) Possibleconcentrationofimpuritiesinthechlorineasitisevaporated,suchas explosivenitrogentrichloride.Thisneedstobediscussedwithyourchlorine supplier.(d) Reverseflowofreactionfluids,causedbyafallinpressureinthevaporiser, orbyexcesspressureintheprocess,orbysolutionofchlorinegasinthe fluid.Thepresenceofthefluid(water,solventorreagent)inthevaporisercan causecorrosionorlocalviolentreactionleadingtorapidoverpressureand possibleruptureofthevaporiser.(e) Carry-overofliquidchlorineasbulkfluidordropletsintothegaslineorinto theprocessitself.Thiscan(dependingonthematerialsofconstructionandon theprocess)causedamageorhazard.(f) Excessivegaspressuretothesystemduetooverheatingavaporiser,since thevapourpressureofchlorinerisesverysteeplywithtemperature (seeAppendix2,FigureA2.1).(g) Excessivehydraulicforces,ifthesystemisclosedupandfullofliquiddueto theexpansionofliquidchlorinewhenheated.
Thesebasichazardsareconsideredinmoredetailinparagraphs156-161,butgroupedaccordingtothetypeofhazard.
Flooding and liquid carry-over
156 Flooding(filling)ofthechlorinevaporiserwithliquidchlorinemayresultfromoperationoftheequipmentaboveitscapacity,inadequateheating,orfoulingoftheheattransfersurfaces.Thetemperatureoftheheatingmediumisusuallycontrolledthermostatically.Ifthetemperatureoftheheatingmediumfallstoolowin
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aself-regulatingevaporator,itispossiblefortheoutgoinggastobeinadequatelysuperheated,orforfloodingtooccur.Floodingresultsincarry-overofliquidchlorineintothevapourlines,andapotentialhazard(dependingontheprocessandplantmaterials).Thesamemayhappenifthelevelofwaterinawaterbathfalls.Intheextreme,ifchlorineisdrawnoffbutnoheatissuppliedtothevaporiser,itispossibleforicetoformontheheatexchangersurfacesanddamagethemseverely.Youshouldconsiderinstallingagasflowrateindicator.Thismaybeofvaluetotheoperatorforroutinepurposes,andwillalsoindicateexcessivewithdrawalrates.
157 Youshouldconsiderfittingaknockoutpot(orspraycatcher)topreventchlorinedropletsandsprayfrompassingintogaspipeworkwhenliquidchlorinemightdamagethematerialofthepipes,orcausetheprocesstobecomeunstable.Inallcaseswherethepossibilityofliquidpassingtoprocessisunacceptable,itisstronglyrecommendedthatalowtemperaturealarmbefittedneartheknockoutpotandarrangedtocutofftheliquidchlorinesupplytothevaporiseror(inself-regulatingtypesonly)thegaseouschlorineoutletmaybeclosed,drivingtheliquidchlorinebackintothestoragevessel(s).Adequateinstrumentationandalarmsshouldalwaysbeprovidedtogiveimmediatewarningofthiscondition.Highandlowbathtemperatureandlevelalarmswithshut-downfacilitiesarerecommended.
Accelerated corrosion and reaction (high temperature)
158 Toavoidrapidcorrosionofthewatersideofheatexchangesurfacesmadefromgalvanisedsteel,operatingtemperaturesshouldnotexceed70oC.Ifoperationathighertemperaturesisrequired,vaporisersmadeofnickelornickelalloys(suchasMonel400orInconel)shouldbeused.Insuchcases,thedownstreamchlorinegaspipeworkmayalsoneedupgradingtoensureadequateresistancetocorrosionatelevatedtemperatures.
159 Iftheheatingmediumissteam,thetemperaturecanbemonitoredbylowpressureandhighpressurealarmsonthesteaminlet.Thepressureofsteamshouldnormallybelimitedto1bargauge(120oCequivalent)andthesteamhastobesaturated,notsuperheated.
High pressure
160 Precautionsmust23beinplacetoprotectthesystemagainstover-pressurisation,egapressurereliefdevice.Pressurereliefdevicesandhighpressurealarms,wherefitted,shouldbeproperlydesignedandinstalled,maintainedinaneffectiveworkingorder,andtestedregularly.Theymustbeperiodicallyexaminedbyacompetentperson.53Atypicalworkingtemperatureforavaporiseris70oC.Thevapourpressureofchlorineat70oCexceeds21bar,(seeFigureA2.1,Appendix2).Itfollowsthatyouneedtotakethefollowingstepsto:
(a) Ensurethatthevaporiserisnotisolatedwhenfullofliquidchlorine.Strict observanceofwrittenproceduresforshut-downisvital.(b) Avoidaccidentallyisolatingthevaporiseronbothsides.Careneedstobe takentoensurethattheclosingarrangementsfortheemergencyvalvestake thisintoaccount(seeparagraphs162-165).(c) Designthevaporisershellandpipestowithstandtheworkingpressureand duty.(d) Implementoperationalcontrolswhichminimisetheriskoftheworkingpressure beingexceeded.
Ifyourchlorinevaporiserisnotsuppliedwithapressurereliefdeviceyouwillneedtoadoptprocedures,orfitsuitablepressurerelief,toensurethattheconditionsin(a)to(d)aremet.
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Reverse flow
161 Youshouldeliminatethepossibilityofsuck-backintothevaporisersbysuitabledesign.Forexample,waterchlorinatingpackagesystemsusuallyincorporateasetofvalvesinthecontrolsystemtopreventsuck-backorpush-back.Thearrangementsvary,andcareneedstobetakentoensurethatthesystemprovideddoesgiveprotectionintheeventof,eg,aleakattheejectornon-returnvalve.Youshouldalsoconsiderfittingalowpressuregasalarmtotheoutletgasline.Thisgiveswarningoflossofsupplytotheprocess,andmayindicateaneedtostartpurgingthesystem,usingdryairorothersuitabledrygas(dewpointlessthan-40oC)topreventsuck-back.Whatevermethodisused,thesystemneedstoberegularlyinspectedandmaintained,andadequaterecordskept.
Emergencyshutdownpushbuttonatthevaporiser.Alsoshowninoneofsixchlorinedetectorsatthis
installationwhichcanalsoautomaticallyshutdownthechlorineinstallation(seeparagraphs113-118)
Routine and emergency isolation
162 Thevaporiserhastobecapableofbeingisolatedformaintenance,orinanemergency,suchasafailureofthevaporiseritselfthroughleakageorafailureofthegaslinedownstream.Inadditiontoamanualvalveontheliquidinletandonthegasoutlet,remotelyorautomaticallyoperablevalvesarestronglyrecommendedonbothinletandoutlet.Apressure-reducingorflowcontrolvalvewillalmostalwaysbefittedontheoutletanditissometimespossibleforthisvalvetobetheremotelyoperableshut-offvalve.
163 Yourriskassessmentshouldconsidertheneedforadditionalprotectionintheeventthatautomaticvalvesfailtooperate(orremotelyoperablevalvesarenotactivated)inanemergency.Forexampleaflowrestrictionintheliquidinlet(typicallyontheexitfromthestoragetank(s)),willlimitthereleasewhichcouldoccurintheeventofamajorplantfailure.
164 Thehazardsoftotallyisolatingthevaporiserareconsiderableandwillbemostseverewhentheevaporatorisfull(egifthevalvesclosetogetherinaconditionofmajorgaslinefailure).Ifthereisagasspaceabovetheliquidchlorinewhenthevaporiserisisolatedandheated,theinternalpressurewillreachthatofchlorineattheheatingmediumtemperature.Thevaporiser,linesandvalvesneedtobedesignedtowithstandsuchpressureorincorporatearrangementstorelievetoasafeplace.Thecontrolofautomaticvalvesneedstobearrangedsothatthevalvesdonotclosetogetherwhenanalarmisraised(seealsoparagraph160).Oneapproachistoarrangeforthegascontrolvalvetocloseonalarmsrelatedtoimproperworkingofthesystem(eglowgaspressure,downstreamprocessalarms,lowtemperature)andtheliquidcontrolvalveatthestoragetanktocloseonchlorinerelease(egdetectorslocaltothevaporiserandstorage,ormanualalarms).Iftheplantiscontinuallystaffed,manualinterventionmaybeasuitablealternativetoprovidingwhollyautomaticoperationofshut-down.However,proceduresneedtobeestablishedtoensurethatthisdoesnotintroducesignificantdelaysintotheresponsetoanalarm.Analternativeapproachistouseapressurecontrolglobevalveforremoteisolationoftheoutletlinesothatexcessivepressureswillliftitslightlyoffitsseat,preventingexcessiveoverpressures.
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Reliefpressuresandvalvedirectionneedcarefulconsiderationandshouldbediscussedwiththevalvesupplier.
165 Isolationofthevaporiserisstillpossible,butinterlocksbetweentheinletandoutletvalvestopreventtotalisolationarerarelyfitted.Thisisbecauseitisoccasionallynecessarytoclosebothvalvesduringcleaningandoverhaul.Asafesystemofworkformaintenanceandoperationisthusavitalpartofthesafetyarrangements,andisarequirementunderthePSTGCRegulations.23
Pressure control valve
166 Allvaporiserdesignsincorporateanelementofsuperheatingofthevapour,eitherinthevaporiseritselforasaseparateunit.Thisisnecessarytopreventchlorinereliquefyinginthecontrolvalves,whereitcouldcauseproblemsofirregularpressureinoperation.Theseproblemsareavoidedbyreducingthegaspressureattheexitfromthevaporiser.Asuitablepressure-reducingcontrolsystemisrecommended.
Corrosion
167 Corrosionofthevaporisertubesorcoilscouldleadtoaloss-of-containmentaccident.Theconsequenceofaminorchlorineleakfromthechlorinesideofavaporiserheatingbathcouldbeveryserioussincethemixtureofchlorineandmoisturewillleadtorapidcorrosionoftheevaporatorsurfacesandasubstantialreleaseofchlorine.
168 Youmustarrangeforacompetentpersontoperiodicallyexamineyourvaporiserandotherpressuresystemsinaccordancewithyourwrittenschemeofexamination.54Acompetentperson53mustcertifythatthewrittenschemeforexaminationissuitableforthepurposeofpreventingreasonablyforeseeabledangertopeoplefromtheunintentionalreleaseofstoredenergyfromthesystem.Thewrittenschemeofexaminationshoulddescribethenatureandfrequencyoftheexamination.Thisshouldbebasedonriskassessmentandgivedueconsiderationtothedutyandtheconditionofthevaporiserwhenitwaslastinspected.Thecompetentpersonwilladviseonsuitableexaminationandtestregimes,andwhenthevaporisershouldbereplaced.Examinationintervalsbetweenoneandfiveyearsaretypical.Coil-in-bathevaporatorsarecommonlygivenarigorousinspectioneverytwoyears,andthecoilsarediscardedifseriouslypitted.Somemanufacturersadvisethatthecoilsshouldberenewedeverytwoyears.Followingexaminationtheequipmentshouldbethoroughlydriedtoadewpointlessthan-40oCbeforerecommissioning.Moistureleftinthesystemcanleadtoveryrapidcorrosion.Theprocedureshouldbecoveredbyawrittenoperatingprocedure.
169 Corrosionoftheheatexchangersurfacesisnotdirectlymonitored.Insteadtheevaporatorvesselortubesarefrequentlyprotectedagainstwatercorrosionbycathodicprotection.Typicallytheanodesshouldbecheckedvisuallyeverythreetosixmonths.Thefrequencyshouldbeestablishedbyexperienceoftherateatwhichtheanodesareconsumedandreplaced.Iftheanodesarefoundwhollyconsumedatinspection,athoroughexaminationofthevaporisershouldbeundertaken.Thewaterbathorcondensateoutletshouldbemonitoredforchlorineleaksbyredoxorconductivitymeasurements.Thisearlywarningofminorleaksishelpfulinallcases,andisverystronglyrecommendedifcathodicprotectionisnotprovidedornotmaintained.
170 Accumulationofsoliddepositsreducestheeffectivenessofavaporiserandcanalsoenhancecorrosion.Thevaporiserneedstobecleanedanddriedtoadewpointlessthan-40oCregularly.Closeattentiontothecleaningprocedurewillminimisecorrosionbuttypically,thechlorineevaporatorcylinderinahotwaterbath
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(seeAppendix7,type1csystem)shouldberenewedafterfiveyears.Theoldonemaybesubmittedtoacompetentinspectionbodyforcertificationforfurtheruseifrequired.
CHLORINE ABSORPTION SYSTEM
171 Youshouldgivedetailedconsiderationtoensurethatinallchlorine-usingoperationschlorinecan,inanemergency,beventedtoanabsorberwithoutemissiontotheenvironment.
172 Controlofchlorineemissionsfromprescribedprocesses(seeparagraph10)mustbethesubjectofconsultationswiththeEnvironmentAgencyinEnglandandWalesandSEPAinScotland.
173 Insomeinstallations,thenatureoftheconsumingprocessissuchthatabsorptionofthechlorineispossiblewithoutaspecialabsorptionunit.However,insuchcircumstancesoperatorsneedtoensurethatduringmaintenanceperiodsadequateabsorptioncapacityisalwayskeptavailabletoaccommodateanychlorineemissions.Aseparateabsorptionplantmaynotbeessentialin,forexamplecooling-watertreatmentplantsandbleachliquorproductionplants.
Lutepipe(baromaetricleg)andventforabsorptionsystem
174 Formostbulkstorageinstallations,however,aseparatechlorineabsorptionplantisrequiredanditshouldalwaysbemaintainedinastateofreadiness.Thequantityofreagentsavailableintheabsorptionsystemneedstobeadequatetodealwithanyforeseeableemergency.Theinlettothescrubbingsystemshouldincludealutepipe(barometricleg)topreventliquidfromthescrubbingsystementeringthechlorinesystem.
175 Theresponsibilityfortheinstallationofanadequatechlorineabsorptionsystemrestswiththeconsumer,butyoushouldobtainthechlorinesupplier’sadviceontheproposedinstallation.
176 Considercarefullytheprovisionofadequateinstrumentationwithalarmsandthedisposalofeffluentfromthechlorineabsorptionplant.
177 Adequatestandbyequipmentshouldbeprovidedtocoverbreakdownsandroutineoverhauls.Essentialcirculatingpumps,fansandinstrumentationshouldbeamongthoseitemswhichareconnectedbothtothemainsandtothefactoryemergencypowersupplyifthereisone.Whentheabsorptionfacilityisrequiredtobecontinuouslyavailable(egventsfromreactors)itisessentialtoprovideemergencypowerandstand-bycirculatingpumpsoranemergencygravity-fedsupplyofabsorbingsolution.
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Vent collection system
178 Thepipelinesforthecollectionoftheventgasescontainingdrychlorinemaybemadeofmildsteelbutback-diffusionofmoisturefromtheabsorptionsystem,whichmayoccurifventingsareintermittent,hastobeprevented.
179 Ventsystemsfromreliefsystems,whicharelikelytooperateonlyinfrequently,maybeprotectedfromback-diffusionofmoisturebytheuseofprotectivemembranes.Insomecasesitmayhelptoprovideacontrolleddrygaspurgethroughtheventlines.
180 Ifthereisanyriskofmoisturecontamination,thepipeworkhastobemadeofrubber-linedorplastic-linedcarbonsteel,orplasticresistanttowetchlorine(egPVC,HetronorAtlac382),orglass.
181 Ifthereisanypossibilityofliquidchlorinecarry-over,liquidgasseparatorsshouldbeinstalledonthelinestoavoidexcesspressureoroverloadingoftheabsorptionsystem;theseseparatorsarefittedwithatemperaturealarmtoindicatethepresenceofliquidchlorineintheseparator.Furthermore,ifitispossibleforliquidchlorinecarry-overtotakeplace,plasticpipeworkshouldnotbeused.Pipeworkshouldbesizedtotakeaccountofthemaximumpossibleflowsunderthemostunfavourableconditions.
Absorption equipment
182 Varioustypesofabsorbersareusedforthetreatmentofventgases;suitableabsorbersmaybebasedontheuseofpackedtowers,ventinjectorsorspargeabsorbers.Itcanbeanadvantageifthesystemselectedgivesasuctionontheplant.
183 Causticsodaliquoristhemostconvenientreagentforabsorptionofchlorineinwastegases.Theconcentrationofcausticsodashouldnotexceed21%NaOHbecauseoftheriskofsaltdepositcausingblockagesintheabsorptionplant.Itisrecommendedthattheflowofchlorineiscontrolledorrestrictedbyanorificeplatetoanacceptablemaximum,sothatthetemperatureriseintheabsorberdoesnotreduceitseffectiveness.
184 Alternatively,forinstallationswherethereisnobulkstorageforcausticsodaliquorandwherelimeorsodaashisavailableonthesite,alimeslurryorasodaashsolutionmaybeused.
Instrumentation
185 Itisessentialthatfaultsaredetectedquickly.Adequateinstrumentationwithalarmsshouldbeprovidedontheventabsorptionplanttoensurethereisawarningifequipmentfails.Significantfaultsare:
(a) Lossofcirculation.(b) Chemicaldepletionoftheabsorbingsolution.Depletionofthesolutioncanbe monitoredbytheuseofredoxorconductivitymeasurement.
186 Considerprovidingapressureindicatorfittedwithanalarmtoshowifthereisexcessiveventingorablockageintheabsorptionsystem.
187 Amonitortodetectchlorineshouldbeinstalledontheoutletfromtheabsorber.Ondetectingchlorinethefollowingactionsareneeded:
(a) raisethealarm.
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(b) isolatetheflowofchlorinetoprocess;and(c) increasetheflowofliquortotheventscrubber.
Theflowfromtheventlinetothescrubbershouldbemaintained.Isolatingtheflowtothescrubbermayputpeopleatrisk.
Chlorinedetectoralarminventlinefromabsorber
Disposal of effluent from the chlorine absorption plant
188 Thedisposaloftheliquorfromthechlorineabsorptionplantrequirescarefulconsideration,asthepresenceofhypochloritemaycreateproblems.Ifthewasteliquorisdischargedwithouttreatment,thepossibilityofinteractionwithothereffluentsshouldbeinvestigated(egamixturewithacideffluentcanleadtoevolutionofchlorineintheeffluentmains,andwithammoniacaleffluentcanleadtoformationofnitrogentrichloride).
189 Undersomecircumstancesitmaybenecessarytotreattheeffluenttoreducehypochloritecontenttoanacceptablelevelbeforedischargingtoasewer.YourchlorinesupplierandyourlocalEnvironmentalHealthOfficershouldbeconsultedonanenvironmentallyacceptablemeansofdisposal.ForhighlycontaminatedeffluentyoushouldconsulttheEnvironmentAgencyorinScotland,theScottishEnvironmentalProtectionAgency.
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Operating and maintenance procedures, training and PPEOPERATING INSTRUCTIONS
190 Oneofthemainrisksofchlorineescapetotheenvironmentisfromincorrectoperationoftheplant.Operatingproceduresandtheselectionandtrainingofprocessoperatorsarethereforeextremelyimportantconsiderationsfortheefficientandsafeoperationofchlorineinstallations.Youroperatingproceduresneedtocovereachprocessoperationandmeetlegalrequirementsegseereferences18,23,and55-60andthestandardsrecommendedinindustryguides(seeAppendix4andreference22).191 Writteninstructionsarerequiredfor: (a) plantmaintenance(seeparagraphs193-198);(b) plantcommissioninginspectionandtesting(seeparagraphs199-209);(c) plantmodificationandshut-down(seeparagraphs210-213);(d) allprocessworkandproceduresinvolvedintheunloadingofliquid chlorinetankers(seeparagraphs214,215);(e) operationofthestorageinstallationandutilisationofthechlorine (seeparagraphs214-229);and(f) emergencyactiontodealwithchlorinespillagesandgasescapes (seeparagraphs247-263).
Thesemaytakedifferentformsdependinguponthecomplexityoftheinstallation,egfromsimpleguidecardsforstraightforwardoperationstocompletemanualsforcomplexoperationsandinstallations.
192 Youshouldmakethesitemanagerorotherdesignatedpersonresponsibleforauthorisinganyamendmentstotheproceduresorschedules.Youneedtoensurethatcopiesoftheinstructionsincludeaflowsheetandindicatethevalvestobeclosedinanemergency.Instructionsneedtobeavailableintheworkingareaforoperators,andinthecontrolroomorcontrolcentreforoperatorsandsupervisors.Supervisorsshouldcheckregularlythatoperationsarecarriedoutpreciselyaccordingtothewritteninstructions.
MAINTENANCE, INSPECTION AND INSTALLATION
General maintenance requirements
193 Satisfactorymaintenanceofplant,equipmentandinstrumentationisessentialtominimiserisks.ThemainRegulationsthatyouneedtocomplywithare:COSHHRegulations20,MHSWRegulations18,andPSTGCRegulations(regulation12).23-25TheCIMAHRegulations5(tobereplacedinFebruary1999bytheCOMAHRegulations-seeAppendix3),willalsoapply,dependingonthesizeoftheinstallationandtheoperatingconditions.
194 Youwillneedtopreparemaintenanceschedulesdefiningtherequiredfrequencyforservicing,testingandinspection.Theseschedulesshouldbestrictlyadheredto.AppropriaterecordsoftheresultsmustbekeptasrequiredbythePSTGCRegulations1989andCOSHHRegulations.Theneedforawrittenschemeofexamination(WSE)54isaseparaterequirement(ieregulations8and9)ofthePSTGCRegulations.Otheraspectsofmaintenanceareindicatedinparagraphs19,44,51,56-58,71,81,86-89,98,127,136,143,160-162,165,169,173,174,225,232,233,237,and255.
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195 Youneedtoensurethatdetailedwritteninstructionscoveringallroutinemaintenanceoperationsareavailable.Theseshouldbeformallyapprovedandissuedbytheresponsiblemaintenanceengineer.Supervisorsshouldcheckregularlythatworkiscarriedoutaccordingtotheseprocedures.Payparticularattentiontocorrosion(seealsoparagraphs167-170),especiallywherelaggingisused;andtochlorinedetectorsystemstokeepsuchmonitoringequipmentineffectiveoperation.
196 Closeliaisonisnecessarybetweenthemaintenanceengineerandtheprocessmanager,toensurethatmaintenanceworkisstartedonlyaftertheequipmentconcernedhasbeenadequatelypreparedbyprocesspersonnelandisfreefromchlorine.
197 Adequatetrainingisrequiredforallmaintenancepersonnel.Thisshouldincludebasicinformationonthepropertiesofchlorine,safetyprecautionsandemergencyprocedures(seealsoparagraphs231-234).
Maintenance of connections
198 Theinspectionandreplacementproceduresforhosesandconnectionsmustbedocumentedinaccordancewiththewrittenschemeofexamination.54Recordsoftheinspectionsandreplacementsshouldbekept.Youneedto:
(a) Carryoutengineeringinspectionsofhosesatleastonceayear,orperevery 1000operations.
(b) Renewconnectionsatregularintervals,orasrequiredasaconsequenceof theengineeringinspection.Flexiblehosesshouldberenewedoneitherafixed timescheduleornumberoftransfersasadvisedbythehosesupplier.(c) Hydraulicallypressuretestreplacementflexibleconnectionsanddrythemwith dryairtoadewpointlessthan-40oCbeforeuse.
Inspection and commissioning of chlorine tank installations
199 Itisyourresponsibilitytoorganiseandcontrolinspections,testingandthecommissioningofyourstoragetank.Yourchlorinesupplier,asamatterofpolicy,willgiveadviceifrequestedtodosoandvisittheplantbeforeitiscommissioned.Theydeliverchlorineonlyiftheyconsideryourinstallationtobesatisfactory.YourequipmentinstalleralsohasresponsibilitiesunderSection6oftheHealthandSafetyatWorketcAct.YouandyourinstallerhaveresponsibilitiesunderthePSTGCRegulations;inparticularthewrittenschemeofexamination(WSE)mustbeinplacebeforethepressuresystemgoesintoservice.
200 Youshoulddeterminethescopeoftheschemefortheexaminationofthepressuresystem,withexpertadvicebeingobtainedifrequired.TheWSEmustspecifyallinspectionandtestingtechniquesemployedasrequiredbyRegulation8ofPSTGCRegulations.TheWSEreportmustcontainspecificdetailsofanydeteriorationfoundinthevesselorvesselancillaries(seeRegulations9ofPSTGCRegulations).Itshouldstatewhichpartsofthesystemhavebeenexamined,theconditionofthosepartsandtheresultsoftheexamination.
201 Initialinspectionandtestingshouldbecarriedoutinaccordancewiththedesigncode(seeparagraph88).Thefirstthoroughin-serviceexaminationofavesselspecifiedforliquidchlorinedutyshouldbemadebyacompetentinspectingauthority24withinfiveyearsofcommissioningandpreferablywithintwoorthreeyears.ThereafterthefrequencyoffurtherthoroughexaminationsshouldbedeterminedbytheinspectingauthorityandnotedintheexaminationreportasrequiredbyRegulation9ofthePSTGCRegulations.
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TheWSEcanonlybemodifiedafteranexaminationiscomplete.Theexaminationintervalshouldnotnormallyexceedfiveyears.
202 Acompetentperson53tocarryoutsuchexaminationshouldhavetheknowledge,experienceandresourcestosearchfor,detectandassessparticulardefectsassociatedwithsystemscontainingchlorine.Resourcesshouldincludeaccesstoappropriatenon-destructivetestingandlaboratoryfacilities,togetherwithprofessionaltechnicalabilitytorelateinspectionfindingstoappraisalofvesselintegrity,safeworkingparametersandfutureuse.Thecompetentpersonmustassessthevesselforcontinuedusewithchlorinewithrespectto:
(a) maximumandminimumsafeworkingpressures;(b) maximumandminimumsafeworkingtemperatures;and(c) safeworkingloadsatsupportsandfoundations.
Suchinformationshouldbenotedontheexaminationreport,togetherwiththelatestdateforthenextexamination.
203 Forlaggedtanks,youneedtoremovesufficientlaggingtoenabletheconditionoftheexternalsurfaceofthetanktobeassessed.
204 Routinehydrostatictestingisnotnormallyrecommended.Itis,however,recommendedifanymodificationsaremadetothestoragevessels.Suchmodificationsrequireafurtherexaminationbythecompetentperson.
Inspection procedure
Preparation for internal inspection
205 Beforeopeningthestoragevesselforinspection(seealsoparagraph168),thevesselneedstobeemptiedofliquidchlorineandpurgedtoremovealltracesofchlorine.Proceduresforthisshouldbecoveredbypreciseoperatinginstructions46andnormallyinclude:
(a) breakingofallpipeworkconnectionstothevesselbyremovalofspoolsorby blankingoff;(b) removingthemanlidandfillingthevesselwithwatertowhichsodaashhas beenaddedtoneutraliseacidicmaterialwhichformswhenwaterisadded toferricchloride-thecontentsofthevesselshouldbestirredthoroughly throughouttheprocess;(c) siphoningoffthewaterandcheckingtheatmosphereinthevesselforchlorine andoxygencontent;(d) controllinginternalinspectionofthevesselinaccordancewiththeconditions setoutintheConfinedSpacesRegulations199759andtheCodeof Practice60(seeAppendix3).
Re-assembly after inspection
206 Proceduresforthisinclude:
(a) drainingoffallwater;(b) thoroughlydryingthevesselbydryairornitrogenandremovingandreplacing jointsonallconnectionstothevessel;(c) re-fittingthemanlid;(d) pressurisationofthevesselwithdryairandmeasurementofthedewpointof theairreleased;(e) successivepressurisationwithdryairandreleaseuntilthedewpointoftheair leavingthevesselislessthan-40oC.
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207 Itisgoodpracticetooverhaulallvalvesonthevesselatthetimeofinspection.Followingoverhaultheyneedtobedriedoutandstoredinindividualplasticbagspendingreinstallation.Ancillaryequipmentshouldalsobeoverhauledateachinspection.Burstingdiscsshouldalwaysberenewed.
Testing (See current version of HSE Guidance Note GS 4 Safety in Pressure Testing)61
208 Followingcompletionofre-assemblyoftheequipmentanddryingouttotherequiredlevel,youneedto:
(a) leaktestwithdrycompressedairornitrogenataround8bargaugeforseveral hours;then(b) introduceasmallquantityofchlorinetothestoragevesselandpressurisewith compressedairornitrogentoaround8bargauge;(c) testalljointsforleakagebyreleasingammoniavapourfromanammonia bottleandobservingtheabsenceoftheformationofwhitefumesof ammoniumchloride(thisisaverysensitiveandwell-establishedmethod).
Ifthereisnosignofleakage,youshouldleavethetankunderpressureforaboutafurther12hoursandthenrepeattheleakagetest.
209 Allassociatedpipelines,whichneedtohavebeendriedouttoadewpointlessthan-40oC,arethengas-testedforleakage.Anyleakingjointsneedtobemadegas-tightbeforeintroducingliquidchlorineintothesystem.
MODIFICATION OF THE CHLORINE SYSTEM AND CLEARANCE PROCEDURES
210 Youshouldonlymodifythechlorinesystemafterconductingariskassessment(andpossiblyHAZOP).50Thisensuresthatapprovalisgivenbyresponsiblestaffcoveringtheoperatingandengineeringsectionsinvolved,andthatappropriateproceduresareputinplacetodealwithanyrequiredalterations.Proposedmajormodificationsshouldpreferablybediscussedwithyourchlorinesupplier.
211 ThePressureSystemsandTransportableGasContainersRegulations198923require(Regulation4)youtomakearrangementsforpropercontrolofrepairsandmodificationstopressuresystems.Anymodificationsorrepairswhichcouldaffecttheintegrityofthesystemhavetobedefinedandoverseenbyacompetentperson.
212 Formalclearanceproceduresneedtobeestablishedaspartofapermit-to-worksystem46for:
(a) ensuringthattheplantisinasatisfactoryconditionformaintenanceand internalexamination,appropriatelyisolatedandfreefromchlorine;(b) coveringallworkinthechlorineareawhichrequirestheuseofcranes,mobile equipment,weldingsetsorotherplantwhichcouldleadtoaccidentaldamage tothechlorinesystem.Thissafeguardisnecessaryeveniftheworkdoesnot directlyinvolvethechlorine-containinglinesorequipment;(c) formallyacceptingthattheplantissafeforoperationaftertheworkhasbeen completed.
213 Thestorageinstallationmustbeemptiedofliquidchlorineduringinspectionandmaintenanceoftheexpansionvesselunlessprovisionhasbeenmadeforalternativemeansofreleaseofpressure.
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UNLOADING OF LIQUID CHLORINE FROM ROAD TANKERS TO STORAGE
214 Transferofliquidchlorinefromtankerstoliquidchlorinestoragemaybeachievedeitherbyuseofdrycompressedairordrynitrogenorbyuseofchlorinegaspressure.Themethodsemployingdrycompressedairornitrogenaresimplerandtheuseofchlorinegaspressureisnormallyencounteredonlyinspecialcircumstances.Thegassupplypressureneedstobeabout1.7barabovethepressureinthestoragevessel(iethesaturatedvapourpressureofchlorineatambienttemperature)toeffectthetransferofliquidchlorinefromthetransportvehicletostorage.
215 YoushouldbaseyouroperatingproceduresforunloadingontheoutlinegiveninAppendix6.Theproceduresshouldspecifyrequirementsforinspectionandtestingofcouplingsbeforeuse(seeparagraph198).Someoperationaldetailsaresummarisedinpoints(a)-(f):
(a) Visualinspection,beforeuse,withparticularattentiontothreads.(NB hydrocarbonoilsorgreasesmustnotbeusedonthreadedorother connections-seeAppendix2,andparagraph56(j).)(b) Useofnewgaskets(seeparagraph56(h))eachtimeconnectionsaremade tothetanker.Compressedasbestosfibre(CAF)gasketsarenot recommendedforenvironmentalreasons.IfCAFisusedthediscarded gasketsshouldbecollectedanddisposedofsafely,bearinginmindthatthey containasbestos.(c) Provingofthetightnessofallconnectionsbeforeintroducingliquidchlorine.A gaseouschlorinetestisrecommended(seeparagraph208c)afteradryair/ nitrogentest.(d) Cappingpipesafteruseandprotectingpipestoreducethepossibilityof accidentaldamagetothreadsoringressofmoisture,andprovidean additionalsafeguardagainstanaccidentalreleaseofchlorineduetoanerror invalveoperation.
(e) Considercontinuouspurgingwithdryairornitrogen(dewpointlessthan -40oC).(f) Itisimportanttovent‘paddinggas’totheabsorptionsystem(seeparagraphs 171-184)afterthetransferoperationiscomplete,torestorethepressureinthe tanktoaboutthevapourpressureofchlorineatthetemperatureofthetank contents.Ifthisisnotdone,thetankmayover-pressuriseasitwarmsup,and causethereliefsystemtooperate.
Testingforleakswithammoniabottle(seealsopara208c).Thedriverteststhejointsnearthetankerdome
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USE OF ISO (DEMOUNTABLE) TANK CONTAINERS
ChlorineISOtankcontaineronroute ISOtankcontainer:detailoftheconnectionpoint
216 AnISOtankcontainerisapressurevesselmountedinasubstantialsteelframe.Theyareusedpredominantlyforrailandseatransportandwherecontainersneedtobestacked.Theyvaryincapacity,andinthecaseofchlorinethelargestvesselscanholdabout14tonnes.ISOcontainersareusuallysizedtomeetcustomerrequirementsandinvariablyeachtankisdesignatedtoaspecificcustomer.Ifyourplannedconsumptionofchlorineisnotenoughtojustifyinvestmentinabulktankandtoogreatfortransportablecontainers1tobeused,anISOcontainermaybeappropriate.Ifthecontainerchangeoverperiodexceedsfourweeksyoushoulddiscusstheuseofonetonnedrumswithyourproposedsupplier.
217 ThedriverisresponsibleforensuringthattheISOcontainertraileriscorrectlyberthed,themotiveunitisuncoupled,andthatthelandinglegsonthecornersofthetrailerareinplace.
218 ThedesignoftheISOberthshouldbesimilartotherequirementsforanoff-loadingbayforroadtankers(seeparagraphs31-41)egthegroundmustbelevelandtheareawell-lit,awayfromtrafficetc.Thegroundsurfaceneedstoberesilientenoughtopreventthelocalloadsfromthelandinglegsdamagingthesurfaceorallowingsinking.Considerspillcontainment(egusekerbing,semi-bundingorcollectionsumps)intheeventofanyincident.Althoughtheframeprovidessubstantialimpactresistance,topreventdamagetothetankanditsfittingsyoushouldprovidecrashprotectionsimilartothatrequiredforfixedtanks.Similarly,youshouldprovidecrashprotectionforyourplantagainstinadvertentmovementduringtheberthingoperation.
219 Youwillneedtoprovidesuitableflexiblehoseconnectionstoconnectthetanktoyourprocess.Theseshouldbeofsufficientlengthandunobstructedroutingsothatalegcollapsewouldnotstressthehoseorconnectingjoint.
220 Youwillalsoneedtodrawupproceduresforconnectinganddisconnectingthetanktoyourprocess.Theseproceduresandtheassociatedinterlocksareeffectivelythesameasforroadtankerunloadingoperations(seeparagraphs35,39-41,214,215andAppendix6).Theyneedtobecarriedoutwiththemotiveunituncoupledandalwayswiththedriverpresentasitisthedriverwhoisresponsibleformaking/breakingandtestingtheintegrityofthejoint.BarriersshouldbeloweredwhentheISOisberthedandthebarrierlinkedmechanicallyorbysoftwaresequencetotheflexiblehoseconnectionasdriveawayprotection.AstheISOtankerisnotfittedwithareliefvalve(aregulatoryrequirement14)measuresmustbetakentopreventoverpressurefromradiantheatsourcessuchasstoredflammables,orfrominertgassuppliedtoraisethepressureinthetankertransferringchlorinetotheprocess.
221 YouwillneedtoagreeprecautionswithyoursuppliertoensurethereisnopotentialforreverseflowfromyourplantintotheISOtank(seeparagraphs224-229)andimplementthem.
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TRANSFER OF CHLORINE TO THE CONSUMING UNITS
222 Transferofliquidchlorinefromthestoragetankstotheconsumingunitsmaybeachievedby:
(a) usingthevapourpressureoftheliquidchlorinealone;(b) paddingthechlorinestoragetankwithdrycompressedgas;(c) transferingtheliquidchlorinetoaseparatetankfromwhichitispumpedusing apumpspeciallydesignedforusewithliquidchlorine.
Methods(a)and(b)arenormallythemostsatisfactoryforcustomerinstallations.
223 Underexceptionalcircumstancesandbyagreementwithyourchlorinesupplier,liquidchlorinefromthetankersmaybetransferreddirectlytoyourprocessortoachlorinevaporiser.Thisisaspecialandunusualarrangement;theadequacyofthecontrolsystemsandproceduresshouldbeverifiedbyariskassessment.IfyouseearegularneedforthisarrangementyoushouldconsidertheuseofISOtankcontainers(seeparagraphs216-221).
Transfer of gaseous chlorine
224 Withtheexceptionofventing,youshouldavoidthedischargeofgaseouschlorinefromtankersorstoragevesselsdirectlytoaprocess.Suchaprocedurecancauseapotentialhazard51byconcentratingthetraceamountsoftheunstablesubstance,nitrogentrichloride,normallypresentinthechlorine-seealsoAppendix2,paragraphs15,20.Inaddition,ariskofsuck-backofmoistureorothermaterialsintothevesselortankerexists(seealsoparagraphs100,161).
Transfer of liquid chlorine using vapour pressure
225 Formanyapplications,thevapourpressureoftheliquidchlorineinthestoragetankisadequatetotransfertheliquidchlorinetotheconsumingunit,althoughtheremaybeproblemsincoldweatherwithoutdoorinstallations,asthevapourpressurewillfallastheliquidchlorinecools.Ifthedemandrateislikelytocauseproblemsincoldweatheroneofthemethodsbelow(paragraphs226,227)shouldbeused.Whentheliquidhasbeenremovedfromthetank,itmayalsobeacceptableforpartoftheremaininggastobeusedonprocess.However,aminimumpositivepressureshouldalwaysbemaintainedinthestoragevessels;thisshouldbedefinedforeachsystem.Youshouldbeawarethatthismethodincreasestheriskofnitrogentrichlorideaccumulationinthetankandyoushouldimplementadditionalmonitoring.52
Transfer of liquid chlorine by padding with dry compressed gas
226 Transferbypaddingthestoragetankswithdrycompressedgasisstraightforward;theactionandprecautionswhichwillberequiredaresimilartothosedetailedinparagraphs134-141.
Transfer of liquid chlorine using a separate pumping tank
227 Completelyenclosed‘canned’pumpshavebeendevelopedfortransferofliquidchlorine:theseareusedwhenthechlorineisrequiredathigherpressure,typicallyabove7bargauge,orwhentheuseofdryinertcompressedgasisnotacceptable.Theliquidchlorineisfirsttransferredfromstoragetoaseparatepumpingtankwhichusuallyconsistsofapressurevesselwithabottomconnection.Theliquidchlorineiswithdrawnfromthebottomofthepumpingtanktothesuctionofthepump.Aremotelyoperatedvalveispreferablyinstalledinsidethetankorbetweenthepumpingtankandthepumpforisolationinemergency.Thedesignof
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thissystemshouldensurethatthenett-positive-suctionhead(NPSH)isadequatetomeettheminimumrequirementsforthepumpused.Ifyouseeaneedforthisarrangementyoushouldseekadvicefromyourchlorinesupplieratanearlystage.
Precautions
228 Youshouldmakearrangementstorapidlystoptheflowofliquidchlorinefromthestoragevesselintheeventoffailureatthechlorineconsumingplant(seeparagraphs35,79,95-97).Longliquidchlorinepipelinestoconsumingunitsmayneedtobeprotectedagainstoverpressure(seeparagraphs61-67).
229 Youneedtodesigntheinstallationtoprevent,orminimisetheriskofsuck-backofaqueoussolutionsorprocessliquidsfromanabsorptionsystem.Thisrequiresdetailedconsiderationatthedesignstageandmightinvolvetheinstallationofanon-siphoningbarometriclegorareverseflow/pressure-measuringdevice.
General guidelines for training
Peoplehavelegaldutiestocomplywiththesafetyproceduresassociatedwiththeirwork.However,itisneversufficientsimplytopresumethatstaffwillknowandunderstandwhattodo.Positiveinstructionandtrainingisneeded.Healthandsafetytrainingshouldtakeplaceduringworkinghoursandshouldbepartofthejob.
Trainingisvitalinhelpingtopreventincidentsandtominimisetheconsequencesiftheydohappen.Thinkaboutwhoshouldbetrained,inwhat,andtowhatlevelofcompetence.
Trainingwillhelpemployeesunderstandthehealthandsafetyaspectsoftheirwork.Initialtrainingfornewstaffshouldbefollowedupwithneworrefreshertrainingasrequired.
Trainingmustincludeanyonewhoworksonthesite.Operators,managers,staffandoccasionalvisitors,suchasmaintenancecontractors,mayallneedsometraining.
Trainingcantakemanyforms,rangingfromon-the-jobtraininglinkedtoinformationnotices,writteninstructionsetc,toformaltrainingcourses.Thetypeoftrainingshouldbeappropriatetotheactivitiesanddutiesofthosetobetrainedandthehazardsatthesite.
Involveandconsultstaff.Wherethereisarecognisedtradeunionsafetyrepresentative,theywillneedtobeconsulted.Theywillknowmanyofthehazardsoccurringineverydaysituations.Caterforunusualoccurrences.
Information,instructionandtrainingmustbeunderstoodbythosetowhomtheyaregiven.Ifpoorperformanceshowsthattrainingisnotworking,thetrainingwillneedtobereviewedandimproved.Donotassumethatpreviousexperienceorformalqualificationswillmeanthatnewemployeesdonotneedtraining.(Youareadvisedtokeepatrainingrecordforeachstaffmember,sothatitisclearwhattrainingtheyhavereceivedand,therefore,whichdutiestheycanbeexpectedtoperform.)
230 Itisessentialthatthepersonnelselectedareofadequatephysicalfitnessandtheyshouldpassamedicalexaminationbeforeengagement.Operatorsneedtobecapableofeffectivecommunicationandbereliableunderstressconditions.Previousexperienceinthechemicalorsimilarindustryisverydesirable.
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TRAINING
231 Youneedtoensurethatsitepersonnelareproperlytrainedandpractisedineachprocedure.Youshoulddevelopandimplementatrainingprogrammewhichincludesboth‘off-the-job’and‘on-the-job’aspects.Youshouldregularlyassesstheprogrammeforitseffectiveness.
232 Off-the-jobtrainingneedstoincludebasicinformationonthefollowing:
(a) statutoryrequirements,ACOPsandguidance;(b) Physical,chemical,andtoxicpropertiesofchlorine;(c) safetyprecautions;(d) personalprotectiveequipment;(e) processoperationsandsystemconfigurations;(f) safesystemsofworkincluding‘permits-to-work’;(g) containertypes,methodsofhandlingandsecurity;(h) operationalprocedures;(i) maintenanceprocedures;(j) defectrectification;(k) automaticcontrolsystems;(l) leakagedetectionsystems;(m) emergencyprocedures,includingleakagecontainment;and(n) chlorinesuppliers’supportfacilities.
Maintenanceengineersneedtobeprovidedwithmoredetailedtrainingonthesetopics,togetherwithtrainingonsystemintegritytesting,pressurereduction,andsafetydevices.
233 On-the-jobtrainingneedstobecarriedoutundertheguidanceofanexperiencedoperator/maintenanceengineerwhoisfamiliarwiththeprocess,withanemphasisonsafetyprecautionsandmethodsofdealingwithemergencies.Giveparticularattentiontothefollowingaspects:
(a) thehazardsandcharacteristicsofchlorine;(b) safemethodsofplantoperation,includingconnectiontoanddisconnection fromsupplysystems,andregularmonitoringandverificationoftheadequacy ofthesystemsadopted;(c) methodsofmaintenanceandinspection,inparticulartheapplicationof relevantstandardsandcodes(seealsoparagraphs193-198).(d) specialoperations;eg,plantshut-downandstart-up,methodsofisolation46 andpreparationofequipmentforperiodicmaintenanceandinspection;(e) thelocationandoperationofemergencyshut-offvalves,ventilationequipment, alarms,leakdetectorsetc;(f) theprocedurestobefollowedifareleaseoccurs,theseshouldinclude isolationandcontainmentofthereleaseandemergencyplans;theprocedures willneedtobesite-specificandcoverdifferentscalesofrelease(seealso paragraphs247-263);(g) trainingintheuseofallpersonalprotectiveequipment(PPE)supplied (seeparagraph237).Maintenancestaffshouldalsocoverdefectrectification.
Competency and audit
234 Competenceintheabovetopicsneedstobeassessedthroughpost-trainingassessmentsusingdocumentedprocedures.Itisrecommendedthattrainingandsafetyproceduresareauditedannuallybymanagementoranauditteamwithrelevantexperienceaspartofyourcompany’sauditprogramme.InternalauditsmaybesupplementedbyexternalauditsfromchlorinesuppliersundertheCIA’sinitiativeforresponsiblecareandproductstewardship,orbyothercompetentpeopleatintervalsofapproximatelythreeyears.
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PERSONAL PROTECTIVE EQUIPMENT (PPE)
235 Chlorineisahighlytoxicsubstance;acuteexposurecanbefatal(seeAppendix1).Youthereforeneedtoestablishsafeworkingpracticesandcontrolmeasures(includingPPE)andensurethattheyareunderstoodbyoperatives.Safeproceduresarevitalwhereitisnecessarytoenteranenclosedstoragespaceoraroomwhereachlorineleakhasoccurred.WorkinsuchconfinedspacesissubjecttoTheConfinedSpacesRegulations1997.59GuidanceonhowtocomplywiththeRegulationsisgiveninanApprovedCodeofPractice.60Theprecautionsidentifiedmustbeimplementedandsuitabletraininggiventooperators.
236 Acommonsourceofexposuretochlorineisinoperationsinvolvingthemakingandbreakingofchlorinepipeworkconnections,particularlytocontainers.Stepsshouldbetakentopreventor,wherethatisnotreasonablypracticable,reducepersonalexposuretochlorine20bymeansotherthanpersonalprotectiveequipment.WhenPPE,includingrespiratoryprotectiveequipment,needstobeworn,equipmentmanufacturedafter30June1995shouldcarrythe‘CE’mark,toindicatethattheequipmenthasbeendesignedandtestedtomeetthebasicrequirementsofCouncilDirective89/686/EEC.
237 Respiratoryprotectiveequipment(RPE)thathasbeenapprovedbytheHSEorisclaimedbythemanufacturertoconformtoastandardapprovedbyHSE,andwhichwasmanufacturedbefore1July1995,cancontinuetobeusedatwork,providedthatitisstillsuitableandmaintainedingoodcondition.AllpersonnelwhoarerequiredtouseRPE(eg,respirators,breathingapparatus,orescapebreathingapparatus)mustreceiveadequateinstructionandtraininginitssafeandcorrectuse.TheRPEmustbethoroughlyexaminedandtestedinaccordancewiththemanufacturer’srecommendations(typicallyatleastonceeverymonth)andrecordskept.20
Selecting suitable respiratory protective equipment (RPE)
238WherePPEincludingrespiratoryprotectiveequipment(RPE)needstobeworn,youmustensurethatitisproperlyselectedandthatitprovidesadequateprotection.63,64WhenselectingRPEyoushouldconsultrelevantguidance65,66andbaseyourselectionontheresultsofariskassessment.20TheselectedRPEmust:
(a) provideadequateprotectionforyourparticularcircumstances(egforspecific tasksorforemergencyescape);and(b) becompatiblewithotherdemandsofthejobandtheworkingenvironment.
TheselectedRPEshouldmaketheoverallriskofinjurywhilewearingRPEaslowasreasonablypracticable.
239 WhenselectingRPEforaparticularapplication,atwo-stageselectionprocedureisthereforerecommended:(a) Basedontheresultsofyourexposureriskassessment: (i)decidewhetherarespiratororBA,oreithermaybeused;then (ii) determinetheminimumprotectionrequiredfromtheRPE.Thisisdone usingtheequationbelow.Indecidingthemaximumallowable concentrationinsidethefacepieceyouwillneedtotakeaccountof recognisedexposurelimits(seeAppendix1)ortakeaccountofyourin- houselimits.
MinimumProtectionRequired=WorkplaceconcentrationoutsidethefacepieceoftheRPE
MaximumallowableconcentrationinsidethefacepieceoftheRPE
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Foremergencyescapepurposeswheretheexposurewillbelessthan15minutes,themaximumallowableconcentrationintheaboveexpressionistheShort-TermExposureLmit(STEL)(seeAppendix1).NowcomparetheMinimumProtectionRequiredvaluewiththeAssignedProtectionFactors(APF)indicatedinHSG5366andidentifyaselectionofequipment.(APFsshowninHS(G)53havebeenpublishedbytheBritishStandardsInstitution).67TheseAPFfiguresareaguide,notahardandfastrule.Indeed,itshouldberecognisedthatprotectionlevelsbelowtheAPFarepossiblewhenRPEisunsuitableforthetaskandisnotsuitedtothewearerandtheenvironment.WhereadvicegiveninHSG53isproperlytakenintoaccount,itispossibletoachieveprotectionatorabovethepublishedAPFvalues.YoumayusehigherAPFsifyouhavegoodqualityinformation(egsatisfactoryface-fitresultsforthosewearingRPE)todemonstratethattheyapplyinyourworkplaceconditionsandtotheselectedRPE.YoucanusetheAPFfortheequipmentselectedtoestimateconcentrationinsidethefacepiece.
Concentrationinsidethefacepiece=Workplaceconcentrationoutsidethefacepiece
APF
Note:‘Nominal Protection Factors’ (NPF) values have been used in the past, for identifying a selection of equipment. This procedure is no longer valid because workplace studies have shown that many wearers may not achieve the level of protection indicated by NPFs.
(b) Thenextstageistotakeaccountofthefactorsdetailedinparagraphs36-47ofHSG53tohelpnarrowdownthechoice.Alwaysinvolvethewearersintheselectionprocess,andwherepossibleprovidethemwithachoiceofsuitableRPE.Thiswillhelptoensurethatitissuitedtothemindividually,andincreasethechancesthatitwillbeacceptedandworncorrectly.
Wherethereisdoubtaboutthechoice,youneedtoconfirmwiththemanufacturerorsupplierthatthechosenequipmentissuitableforthetaskandtheconditionsinwhichitistobeused.TheyhavedutiesundertheHealthandSafetyatWorkActetc1974toprovideinformationonthelimitationsandcapabilitiesoftheirRPE.
240 Atsomechlorineinstallationsitiscommonpracticeforpersonneltocarryhalfmaskrespiratorsfittedwithsuitablefilters(eg:typeandclass:B1;colour:grey)forprotectionagainstchlorine.Thepurposeofthistypeofrespiratoristoprovideanimmediateprotectionintheeventofanincidentinvolvinglowconcentrationsofchlorinegassothatthewearercanescapeintofreshair.ThistypeofhalfmaskrespiratorhasanAPF=10,iethemaximumallowableworkplaceconcentration=10xSTEL=10ppm.
Driverwearingfullfacemaskfittedwithafilter.(Helmetremovedfordemonstrativepurposes)
241 AfullfacemaskwithcartridgeorcanisterhasanAPFof40.Theuseofthistypeofrespiratorwouldtypicallybeinorveryneartheopenairduringthe
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connectingupordisconnectingofcontainersorbreakingintopreviouslypurgedchlorinesystems.Theoperatingproceduresspecifictothesiteshouldstatewhethertherespiratorhastobewornforeachoperation,orbe‘attheready’tobeputonincaseofneed.Arespirator(egamaskfittedwithafilterorcanister)isnotsuitableforuseinatmosphereswhichareimmediatelydangeroustolifeorhealth.Inotherwords,respiratorsarenotsuitableforoperationswherethereisapotentialforasignificantreleaseofchlorinegas.Inthesecircumstancesasuitablebreathingapparatus(BA)shouldbeworn.
242 Filtershaveashelf-lifespecifiedbythemanufacturersbeyondwhichtheyshouldnotbeused.Oncefilter-canistersealshavebeenbroken,filterlifewilldependonusage,contaminentconcentrations,breathingrateetc.Yourriskassessment,combinedwithinformationfromthefiltermanufacturer,willdeterminetheusefullifeofrespiratorfilters;yourdecisionsneedtobecommunicatedtothewearers.Onceunsealed,filtersshouldnotbestoredforre-use,buttheymaybeusedoveranumberofconsecutivedays,providedtheyhavenotbeenexposedtoconcentrationsofchlorinesimilartoorabovethosetheyareprovidedfor.
243 AnegativepressuredemandBAwithfullfacemaskhasanAPFof40.FormajorleaksapositivepressuredemandBAwithfullfacemask(ieaself-containedBA)wouldbeappropriate,providedtheminimumprotectionrequiredwasconsistentwiththeAPF(2000),seeparagraph253.Aself-containedbreathingapparatus(SCBA)shouldalwaysbeworn(possiblywithagas-tightchemicalprotectivesuit)whenenteringanenclosedspaceorchlorineroomwhereasignificantleakhasbeendetectedorsuspected.Thisisbecausethechlorinedetectormaybesomedistanceawayfromthesourceoftheleakorpocketsof‘trapped’gaswhicharenotdispersedbytheventilationsystem.Theconcentrationinsuchareasmaybemuchhigherthanthosedetectedbythealarmsystem.
244 Incertaincircumstances,compressedairlinebreathingapparatus(CABA)maybesuitable.However,theserestrictthemovementofthepersonnelandthetrailinghosecanaddtotheriskinareaswithobstructions.Insuchsituationsaself-containedbreathingapparatusmaybeappropriate.
245 Forindoorinstallationswithmulti-stagealarms,theforcedventilationsystemwillhavebeenswitchedoffonactivationofthehigherlevelalarm.PeopleenteringtheareatoidentifyandeliminatethesourceoftheleakshouldwearsuitableBA,seeparagraphs252-255).Nopersonshouldworkaloneinthesecircumstances.Anyback-upstaffinattendanceforemergencyactionshouldwearsuitableBA‘attheready’.
246 EmergencyescapeBAisnotintendedforuseduringnormalworkandthereforeitisnotrecommendedbyHSEforanythingotherthanemergencyescapeuse.
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Emergency arrangementsNote: Further guidance will be available when the COMAH Regulations come into force in February 1999.
247YouneedtoinformtheappropriateFireAuthorityandPoliceForceofthepresenceofchlorineatyoursite.Youshouldalsoinvolvethemandyourchlorinesupplieratanearlystagewhendevelopingandupdatingyouremergencyplanandprocedures.Youremergencyarrangementsshouldbebasedonariskassessmentandincludeproceduresonhowgasreleasesmaybedealtwithsafelybysitepersonnelandonwhethertocallforassistancefrombeyondthesite.68,69,70Yourriskassessmentshouldalsoaddressfiresafetyoftheprocessorinstallationandpossibleimpactsfromneighbouringsites.GeneralfireprecautionsshouldcomplywiththerequirementsoftheFirePrecautions(Workplace)Regulations1997.21248 Youremergencyplanshouldcovertheforeseeablerangeofchlorinereleasesforyoursite;asummaryofsomeoftheimportantelementsofaplanisgiveninAppendix8.Acopyoftheplanshouldbemadeavailabletoallpersonnelinvolvedinitsimplementation.Itisrecommendedthattheplanincludesthenamesorpositionsofthepersonswhowillsoundtheoff-sitealarm.Thismaybesomeoneon-site,oritmayundersomecircumstancesbetheresponsibilityofthefirstFireOfficeronthesiteintheeventofanemergency.Theplanshouldalsoincludefirst-aid(seeAppendix1)andevacuationarrangementsbothon-siteand,ifappropriate,off-site(seeAppendix8).
249 Eachinstallationneedstohavemeansofwarningallworkersthatagasescapehasoccurred.Awinddirectionindicator,mountedinahighlyvisiblelocation,needstobeprovidedtohelppersonneldecidethebestdirectioninwhichtoescape.Theappropriateactiontobetakenfollowingagasescapewarningshouldbedefinedinwritteninstructions,andappropriatetraininggiven.
250 Foraminorgasescape,youmayonlyneedtoplansimpleactions.Inothercircumstanceshowever,afurthersystemofspecialwarningsmayberequired,whichinitiatestheemergencyplanand,ifnecessary,theoff-siteemergencyplan.Thefirstcallforassistanceshouldbetotheemergencyservicesforincidentcontrolandrescue,andthentoChlor-Aid,throughyoursupplierwhowillofferadviceonhowtodealwiththerelease.UnderChlorAidthechlorineproducersandsuppliers(seeAppendix4)collaborateindealingwithchlorineemergenciesatbulkinstallationsthroughouttheUK.ThearrangementsareoutlinedinabookletpublishedbytheCIA71underthechemicalindustry’sResponsibleCareinitiative.
251 Arrangeregularpracticesoftheemergencyplan.Someoftheseshouldinvolvetheemergencyservices,whowilladviseonasuitablefrequency.
EMERGENCY EQUIPMENT
252 Yourriskassessmentshouldconsidertheextent,type,andlocationoftheemergencyequipment,includingtheneedforchemicalprotectionsuitswhichprovidetotalencapsulation.Thesecanbecompressedairlinesuppliedfullsuitsorfullprotectivesuitswornoverself-containedbreathingapparatus(SCBA).
253 SCBAwithfullfacemaskconformingtoBSEN137(SCBA)72orairlineBAconformingtoBSEN13973hasanAPFof2000(butseeparagraphs238-246).Self-containedequipmentwillsupplyairforuptoabout40minutess(seethemanufacturer’sdetails).Thesesetsareprovidedwithawarningsystemtoalertthewearertoleavethecontaminatedareawhentheaircylindersarebecomingempty.
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Compressedairlinebreathingapparatusprovidesthesameprotectionwithoutatimelimit,butdoesrestrictfreedomofmovementinsearchandrescueoperation.254 AswithotherRPE,emergencyescapebreathingapparatusshouldbeCE-markedandincorporatefaceprotection(egintheformofahoodorfullfacemask).SuitableHSE-approvedescapeequipmentmayalsobeusedifitwasmanufacturedbefore1July1995.Suchequipmentisforescapeonlyandnotforuseduringroutinework.
Emergencyandrescueequipment
255 Emergencyandrescueequipmentshouldbeavailableandreadilyaccessibleinallchlorineplantareas,anditslocationsuitablymarked.Suchequipmentneedstoberegularlyinspectedandmaintained.Aninventoryoftheequipmentshouldbekeptandattachedtotheplantoperationalandemergencyprocedures.
CONTROL OF LEAKAGES
256 Localalarmstationstoprovideearlywarningofchlorineescapesareanessentiallinkintheemergencyprocedure.Theuseofchlorinedetectorsandalarmsiscoveredinparagraphs113-118.Localalarmstations(push-buttontypepreferred)shouldbelocatedatstrategicpointsnearchlorinestorageinstallations;generallytwoalarmstationsonconvenientescaperoutesfromthechlorineunloadingterminal/storagetankareaaresufficient.Thelocalalarmstationsmayactuatetheworksemergencyalarmdirectlyorindirectlybyraisinganalarmintheemergencycontrolcentreandthemaincontrolroom.Preferablyinlargeworksthelocalalarmstationshouldactuateadistinctlocalchlorinealarmtowarnpeopleofffromtheaffectedarea.
257 Thealarmstationsmayalsoactuatetheremotelyoperatedshut-offvalvesonthechlorinestoragetankswherethisisconsistentwiththesafeoperationoftheuserplant.
258 Materialsandequipmentincludingsandandplasticsheetstocontainspillsofliquidchlorineshouldbereadilyavailable.Coveringastabilisedspillwithplasticsheetsisoftenthebestaction.Applicationoffoamwouldcauserenewedevolutionofvapourbecauseoftheheatsupplied.Theneedforfoamandwaterspraysshouldbediscussedwiththechlorinesupplierandlocalfireauthority,sincetheuseoffoamandwatermay,incertaincircumstances,aggravatetheproblem.Thefireauthoritymaycarrystocksofsuitablefoam,butthedecisiontouseitshouldbetakeninconjunctionwiththeseniortechnicalmanageronsite.
259 Watershouldneverbeaddedtoaspillageofliquidchlorineorsprayedontoaleakingtank.However,waterhosesorfogspraysdirectedatachlorinegascloudcanhelpdiluteitasaresultoftheairentrainmentgeneratedbythejetsofwater.
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Releases inside buildings
260 Ifthespillisindoorsandcontainedbytheuseofsandorabunditwillrapidlycoveritselfwithacoatingofslushychlorinehydrateandacoldvapourlayer.Suchastabilisedspillshouldbecoveredwithaplasticsheet(seeparagraphs258and259).Forasevereleak,possiblyarisingfromafailureofpipework,thechlorinebuildingwillprovidesomedelaytothereleaseofthegastotheopenair,providedventsandaperturesareclosedorsealed.Thiswillgivemoretimeforthetechnicalstaffandmanagementtoidentifyanddealwiththesourceoftherelease.Indispersingthecontainedreleasefromachlorineroomitisstillessentialtoconsidertheoff-siteconsequencesanditmaybenecessarytosoundtheoff-sitealarm(whenfitted)toalertpeopletogoindoorsandremainthere.Itisfortheemergencyservicestoconsiderclearingpeoplefromtheareaimmediatelydownwindoftheinstallationaftersucharelease.
261 Asignificantreductioninthereleaseofchlorinefromabuildingisonlyobtainediftheleakisquicklycontrolledandtherateofairchangeinthechlorineroomislow.Theventilationsystemshould,therefore,beswitchedoff(unlessascrubbingsystemisinstalledtoremovechlorinefromtheexhaustgas)andallaperturesneedtobeclosedorsealed.262 Considerusinganadditionalsensorcapableofmeasuringconcentrationsupto500ppmandgivingavisualdisplayoutsidethechlorineroomandintheworkscontrolroom.Suchadisplayisusefulforassessingthesignificanceoftheleakandwhetheritcanbeisolatedsafely.Onceconcentrationsexceed1000ppm(thisisaboutthethresholdconcentrationforthecloudtobevisible),personneldealingwiththereleaseshouldtakeadditionalprecautionsandshouldwithdrawtoasafeareaassoonastheyareawarethattheyarebreathingcontaminatedair.
263 Afteraleakorsubstantialreleasehasbeendealtwithitwillbenecessarytoventilatethechlorineroomthoroughly.OperatorsshouldnotremoveanyRPEuntiltheyhaveremovedclothing(whichmaybecontaminatedwithchlorine)andareinasafeenvironment.
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Appendix 1 Toxicological properties and first aidTOXICITY
1 Chlorinehasaperceptibleodourthatcanbedetectedbymostpeopleataconcentrationof0.3ppm(v/v)andbysomeatconcentrationsaslowas0.02ppm.TheOccupationalExposureStandard(OES)74forexposuretochlorineis0.5ppm;thisisatime-weightedaverageconcentrationoveraperiodof8hours.TheShort-TermExposureLimit(STEL)74is1ppm;atime-weightedaverageover15minutes.
2 Itproducesclearsensoryirritationatconcentrationsof0.5-1ppmandabove.75Irritationofthemucousmembranesoftheeyeandnose,andespeciallyofthethroatandlungs,iscausedbyexposuretochlorineatlevelsofaround1-15ppm.Ingeneral,irritationbecomesintolerableatconcentrationsofabout4ppm.76Concentrationsof50ppmormorearedangerousevenforexposuresofabout5-10mins;theymaycauseinflammationofthelungswithaccumulationoffluid.Occasionallythedevelopmentofrespiratorysymptomsmaybedelayedforuptotwodaysafterexposure.However,thereisnoconvincingevidenceofseriouslong-termsequelaefollowingrecoveryfromasingleexposuretochlorine.75
3 Exposureto1000ppmmaybefatalafterafewbreaths.77Deathresultsfromlungdamage.Itcaneitheroccurrapidly(fromwithinhourstoacoupleofdayspost-exposure),duetooedemaandcongestion,oritcanbesomewhatmoredelayed(severaldays)duetosecondarypneumonia.
4 Theharmfromexposuretochlorineisproportionaltothe‘toxicload’definedastheproductofthesquareoftheconcentrationandexposuretime.Forriskassessmentwork,HSEusesa‘dangeroustoxicload’78(DTL)of:DTL=108000ppm2minwhichispotentiallyfataltothemostvulnerablemembersofthepopulation.Thusexposuresto104ppmfor10minutesor73ppmfor20minutesetcarepotentiallyfatal;thechanceoffatalitydependsonmanyfactors.78
FIRST AID
5 Whenliquidchlorinecomesintocontactwiththeskinormucousmembranesitcanproduceseriousburnswhichneedtobetreatedbyamedicallycompetentperson.Peoplewhohaveinhaledchlorinegasshouldbemovedasquicklyaspossibleinto‘freshair’,laidinarestfulpositionwiththeheadandchestraised,andkeptwarm.Itisessentialthatqualifiedmedicalattentionisobtainedquickly,asserioussymptomsmaydevelopupto48hourslater.Anyonewhohasbeenaffectedbychlorinegasshouldbeexaminedlocallybyamedicallycompetentpersonorsenttohospitalbyambulance.
6 First-aidattendantsshouldbeawareofthedangersarisingfromgassingbychlorine.Thefollowingbasicrulesshouldbeobserved:
(a) ifchlorinehasaffectedtheeyes,theyshouldbeirrigatedwithplentyofclean (preferablytap)water;(b) contaminatedclothingshouldberemovedinawell-ventilatedareaandaffectedskin washedwithplentyofwater;(c) mouth-to-mouthresuscitationshouldnotbegivenifthepatientisbreathing, becausethereisariskoftheattendantbeingharmed.However,oxygenmaybe administeredorresuscitationequipmentusedbysuitablyqualifiedpersonnel.
Morecomprehensiveguidanceisgivenelsewhere.79
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Appendix 2 Characteristics of chlorine 1 Chlorineisagreenish-yellowgasatambienttemperatureandpressure.Itissuppliedcommerciallyasaliquidunderpressure.
2 CommercialliquidchlorineconformstoBS3947:1976.80ThisStandardspecifiesaminimumlimitforthechlorinecontentandmaximumlevelsforwatercontentandresidueonevaporation;detailsofthemethodsofanalysisforgaseousimpurities(carbondioxide,oxygenandnitrogen),watercontent,nitrogentrichloride,andresidueonevaporationarealsogiven.
3 Tracesofdissolvedgaseousimpuritiesinchlorinearenotnormallysignificantformostapplications;moisturecontenthoweverisextremelyimportantbecauseofthecorrosivenatureofwetchlorine.
4 Traceresidueswhichareleftonevaporation,usuallychlorinatedorganicproductsorferricchloride,mayleadtoblockageofpipelines,valvesorinstruments.Nitrogentrichloridecanbepotentiallydangerous51,52ifthevaporisationprocessleadstoitsconcentrationinresidues,butthisisgenerallynotconsideredtobeaproblemindrumandcylinderinstallations.
5 Physical properties
Atomicweight 35.46
Molecularweight 70.91
Density liquid 1561kg/m3at-35°C 1468kg/m3at0°C 1410kg/m3at20°C
gas 3.173kg/m3at0°Cand1barabsolute(relative density2.490at20°Crelativetoair)Boilingpointat1.0133barabsolute -34.05°CMeltingpoint -101.6°CCriticaltemperature 144°CCriticalpressure 77.1barsabsoluteVapourpressureat20°C 6.7barsabsoluteViscosity:liquidat20°C 0.35cp
1volumeofliquidchlorine=463volumesofchlorinegasat0°Cand1barabsolute
1kgofliquidchlorine=0.319m3ofchlorinegasat0°Cand1barabsolute
ThevariationofthevapourpressureofliquidchlorinewithtemperatureisgiveninFigureA2.1.
Thermal properties
Specificheat(liquidchlorinebetween1°Cand27°C)0.236kcal/kg/°C
Specificheat(gasatconstantpressureat6.9barsabsoluteorlessandbetween1°Cand27°C)0.113kcal/kg/°C
Ratioofspecificheatatconstantpressuretospecificheatatconstantvolume1.355
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Latentheatoffusion 21.6kcal/kg
Latentheatofvaporisationat0°C 63.2kcal/kg
Coefficientofcubicexpansion(liquidchlorineat20°C)0.0021per°C
Thiscoefficientissufficientlylargetoresultinexcessivepressureshouldliquidchlorinebetrappedinpipeworkbetweentwoclosedvalveswithnogasspace.
Heatofreactionofchlorinegaswithsodiumhydroxideliquor348kcal/kgofchlorine.
6 Whiletheabovedatagiveageneralsummaryofthephysicalandthermalpropertiesofchlorine,moredetailedinformationisneededforuseinplantdesigncalculations.
Figure 1 Variationofchlorinevapourpressurewithtemperature
Solubility of chlorine in water
7 Chlorinedissolvesslightlyinwatertogiveasolutionwhichhasoxidising,bleachingandgermicidalproperties.Thesolubilityofchlorineinwaterincreaseswiththepartialpressureofthechlorine.Thetablebelowgivesthesolubilityofchlorineinwateratdifferenttemperaturesforatotalpressureof1barabsolute:
Temperature °C 10 15 20 25grams of chlorine per litre of water 9.97 8.5 7.29 6.41
Foratotalpressureof1barabsolute,thepartialpressureofchlorinereducesasthewatertemperature(andhencethepartialpressureofwatervapour)increases.
8 Oncoolingbelow9.6°C,crystalsofchlorinehydrate(Cl2.8H20)aredeposited.Forthisreason,wetchlorineinprocessmustalwaysbekeptabovethistemperaturetoavoidtheblockageswhichwouldotherwiseoccurasaresultoftheformationofsolidchlorinehydrate.
9 Asolutionofchlorineinwaterformshydrochloricacidandhypochlorousacid: Cl2+H20HCl+HOC1
g
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Chemical properties
10 Drychlorineatambienttemperaturesreactsdirectlywithmanyoftheelementsproducingchloridesbothofnon-metals(egsulphurorphosphorus)andofmetals(egironinafinelydividedform,aluminiumortitanium).Drychlorineatambienttemperaturedoesnotattacksteel,copperornickel,butthesemetalsareattackedathighertemperatures.Steelcombineswithdrychlorineabove200°Cand,sincethereactionisexothermic,therateofreactionmayincreaserapidly.Reactionwithnickeldoesnottakeplaceuntilthetemperatureexceeds500°C.
11 Tracesofmoistureinchlorineleadtorapidcorrosionofsteel,copperandnickel.12 Titaniumisresistanttowetchlorinebetween15°Cand100°Cbutreactsviolentlywithdrychlorineandshouldnotbeused;butseeparagraph18.
13 Chlorinedissolvesincoolaqueoussolutionsofalkalistoproducesolutionsofhypochlorites;inhotorboilingaqueousalkalis,chloratescanbeproduced.
14 Chlorinereactsvigorouslywithmanyorganiccompoundsincludingmineraloilsandgreases,producingchlorinatedproducts.Themechanismiseitherdirectadditiontounsaturatedbondsorsubstitutionofhydrogen.Inthelattercase,hydrogenchlorideisformedasaby-product.
15 Mixturesofchlorineandhydrogenareexplosiveoveralargerangeofconcentrations;theexplosionmaybeinitiatedbyaspark,byphotochemicalactionorbyacatalyst.Undercertainconditionschlorinereactswithammoniatoproducenitrogentrichloride,whichisspontaneouslyexplosive.Thisisnotariskwhentestingforleakswithabottleofammonia.
Selection of materials of construction
16 Thechoiceofappropriatematerialsofconstructionforchlorinesystemsisconsideredindetailelsewhere.81Youroptionsshouldbeselectedonlyafteradetailedsurveyofallpossiblevariationsinoperatingconditions,andyourpreferredoptiondecidedinconsultationwithyourchlorinesupplier.
17 Asystemconstructedofsteel,whichisappropriatefordrychlorine,mustitselfbedriedadequatelybeforecommissioning.Thismaybedonebypurgingwithdryairorinertgasuntiltheexitpurgehasadewpointbelow-40°C.However,theupperoperatingtemperaturemustbelimited.
18 Theuseoftitaniummetalforwetchlorineissatisfactory,81providedthatthemoisturelevelisalwayskepthighandthatcontrolisexercisedovertheupperandloweroperatingtemperaturelimit.Maintenanceandinspectionproceduresmustincludeawarenessofthepossibilityofcrevicecorrosion.However,wheretitaniumisusedinplantscontainingwetchlorine(gasorliquid)considerationshouldbegiventothepossibilityofafaultconditiongivingrisetocontactbetweentitaniumanddrychlorinegasorliquid.Ifsuchafaultcouldpossiblyariseitmaybebesttoconsideralternativeconstructionmaterials.
19 Materialswhichareresistanttoattackbybothwetordrygaseouschlorineatambienttemperaturesincludeglass,stoneware,porcelain,tantalum,eboniteandcertainplastics.Theuseofplasticmaterialswithliquid chlorineisunsatisfactory.
LEARNING FROM INCIDENTS
20 Aninterestingselectionofincidents,whichillustratesomeoftheabovehazards(includinganitrogentrichlorideexplosion,atitanium/chlorinefireandexternalcorrosion)andthemeansforcontrollingthem,isreviewedinGEST/AP1.82
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Appendix 3 Relevant legislation and HSE guidance1 ThebasisofhealthandsafetylawintheUKistheHealthandSafetyatWorketcAct1974.Thissetsoutgeneraldutieswhichemployershavetowardsemployeesandmembersofthepublic,andthosethatemployeeshavetothemselvesandeachother.ThesedutiesarequalifiedintheActbytheprincipleof‘sofarasisreasonablypracticable’;ietheextentofthemeasurestakentoavoidorreduceaparticularrisktohealthandsafetyneedstobebalancedagainstthetime,trouble,cost,andphysicaldifficultyinvolved.Thisbalancingprocess83isoftenreferredtoasmakingrisks‘aslowasisreasonablypracticable’(ALARP).
2 Inessence,whathealthandsafetylegislationrequiresiswhatgoodmanagementandcommonsensewouldleademployerstodoanyway:thatistolookatwhattherisksareandtakesensiblemeasurestomakethemALARP.ThisbroadrequirementismadeexplicitintheManagementofHealthandSafetyatWorkRegulations199218,19(referredtoastheManagementRegulations).LiketheAct,theseRegulationsapplytoeveryworkactivity.Otherregulationsaremorespecific,egtheManualHandlingOperationsRegulations(MHO)57ortheControlofSubstancesHazardoustoHealthRegulations(COSHH).20
3 Afulllist3ofcurrentlegislation,ApprovedCodesofPracticeandsomeguidanceispublishedannually.Thelistcontainslegislation,which,althoughinexistence,isspentorhaslapsed.Apricelist84ofallavailableHSEpublicationsispublishedannuallybyHSEBooks.Contactdetailsareontheinsideofthebackcover.
4 Anumberofregulations(egCOSHH,MHO,PPE,64ManagementRegulationsetc)specificallyrequireyoutoundertakeariskassessment.Aleaflet85isavailabledescribinghowtheseassessmentsarelinkedtogetherandwhattherequirementsare;however,itdoesnotdealwithhighlyspecialisedriskssuchasmajorhazards.
5 Underthebasiclegalrequirementsyoumust:
(a) haveawritten,up-to-datehealthandsafetypolicyifyouemployfiveormore people;(b) carryoutariskassessment(andifyouemployfiveormorepeople,recordthemain findingsandyourarrangementsforhealthandsafety);(c) notifyoccupationofpremisestoyourlocalinspectorifyouareacommercialor industrialbusiness;(d) displayacurrentcertificateasrequiredbytheEmployers’Liability(Compulsory Insurance)Act1969ifyouemployanyone;(e) displaytheHealthandSafetyLawposterforemployeesorgiveouttheleaflet;86
(f) notifycertaintypesofinjuries,occupationaldiseasesandevents(seeparagraph23); and(g) consultemployeesandanyappointedunionsafetyrepresentatives87oncertain issues,suchasanychangeswhichmightaffecthealthandsafetyandany information,instructionandtrainingwhichhastobeprovided.
6 TheALARPprincipleandtheneedforriskassessmentenablestheHealthandSafetyCommission,whereappropriate,tomakeRegulationsinagoal-settingform:iesettingoutwhatmustbeachieved,butnothowitmustbedone.Sometimesitisnecessarytoprescribeindetailwhatmustbedoneandsetabsolutestandards.
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7 Someactivitiesorsubstancesaresoinherentlyhazardousthattheyrequireadditionalarrangements.Forexample,chlorineinstallationswhichstore10tonnesormoreneedtomeetthegeneralrequirementsoftheCIMAHRegulations(seeparagraph9).
THE NOTIFICATION OF INSTALLATIONS HANDLING HAZARDOUS SUBSTANCES (NIHHS) REGULATIONS 1982 4
8 TheseRegulationsimplementanotificationschemeforinstallationswithinventoriesgreaterorequaltospecifiedquantities(10tonnesforchlorine).NotificationistotheHealthandSafetyExecutiveviayourLocalAreaOffice(seeAppendix4).UnderNIHHSthefollowingrequirementsapply:
(a) beforechlorineisusedorstoredatasite,atleastthreemonthsnoticemust begiventoHSEandcertaindetailsspecified;(b) thenotificationmustbeupdatedwheneverthereisachangeinactivityon siteorthereisanincreaseorreductionintheoperationalquantityofchlorineonsite; and(c) theamountofchlorineonsitemustnotbeincreasedtothreeormoretimesthe quantityoriginallynotified,unlessanewnotificationismade.(Anyincreasesin inventorylevelsmustofcoursecomplywithotherlegislation,inparticularsection3of theHSWAct,iethattheriskstopeopleoff-siteareALARP).
THE CONTROL OF INDUSTRIAL MAJOR ACCIDENT HAZARDS (CIMAH) REGULATIONS 1984 5
9 TheseRegulationsimplementtherequirementsoftheEuropeanDirective(82/501/EEC)onthemajorhazardsofcertainindustrialactivitiescommonlyreferredtoasthe‘Seveso’Directive.Theyapplytothestorageandprocessingofhazardoussubstances.TheRegulationshavebeenamendedanumberoftimes.3Theseincludethe1988amendment(revisionofthresholdquantitiesforcertainsubstances)andthe1990modificationofthecontrolsonstoragefollowingaseriouswarehousefire.Twolevelsofactivityaredefined.Thelowerlevelrequirementsrequirecompaniestotaketheprecautionsthatarenecessarytopreventamajoraccidentandtolimittheconsequences,andgenerallytodemonstratesafeoperation(regulation4),andtoreportanymajoraccident(regulation5).InstallationsinwhichchlorineisinvolvedinaprocessunderSchedule4aresubjecttothesegeneralrequirementsregardlessofthequantitypresent,unlesstheoperationisincapableofproducingamajoraccidenthazard.Larger(ietop-tier)installationswhichstore75ormoretonnes,orinstallationswith25tonnesormorewhichcarryoutprocessactivitiesunderSchedule4,additionallyrequirethepreparationofsafetyreports,emergencyplansandtheprovisionofinformationtothepublic(regulations7-13).GuidanceontheCIMAHRegulationsisavailable.69,88TheseRegulationswillbewithdrawnwhentheproposedControlofMajorAccidentHazards(COMAH)RegulationsareimplementedinFebruary1999.
THE COMAH REGULATIONS
10 TheseRegulationswillimplementtherequirementsofTheControlofMajorAccidentHazardsInvolvingDangerousSubstancesDirective(96/82/EC)whichwasadoptedbytheEUon9December1996.TheDirectiveisreferredtoasthe‘SevesoII’Directive.TheRegulationsfollowtheDirectivecloselyandmirrortheSevesoI/CIMAHregime,inhavingtwolevelsofduties:
(a) generaldutiesonalloperatorssubjecttotheRegulations:tonotifythecompetent authoritiesoftheiractivities,totakeallmeasuresnecessaryforthepreventionand mitigationofmajoraccidents,toprepareamajoraccidentpreventionpolicy,and reportmajoraccidents;
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(b) top-tierdutiesonoperatorsofsiteswherethequantitiesofdangeroussubstances exceedthehigherthresholds.Theseoperatorsmust,inadditiontothedutiesinthe aboveparagraph,submitsafetyreports,prepareandtestemergencyplansand provideinformationtothepublic.
Inthecaseofchlorinethethresholdquantitiesare10tonnesforthegeneraldutiesand25tonnesforthetop-tierduties.Applicationdependssolelyonthepresenceoranticipatedpresenceofthethresholdquantitiesofdangeroussubstances,includingdangeroussubstanceswhichmightbegeneratedinthecourseofanaccidentduetolossofcontrolofanindustrialchemicalprocess,withnodifferentiationbetweenstorageandprocessing.Thegeneraldutyforoperatorstotake‘allmeasuresnecessaryforthepreventionandmitigationofmajoraccidents’issimilartotheCIMAHRegulationswhichrequiremanufacturersto‘takeadequatestepstoprevent...majoraccidents...andlimittheirconsequences...’.Injudginghowthisdutyshouldbecompliedwithinpractice,thecompetentauthoritieswillbasetheirviewonwhetherriskshavebeenreducedtoALARP.Themainnewrequirementsare:
n AlloperatorswithinthescopeoftheDirectivemustproduceamajor-accidentpreventionpolicy(MAPP)andensurethatitisproperlyimplementedtoguaranteeahighlevelofprotectionforhumansandtheenvironmentbyappropriatemeans,structures,andmanagementsystems.
n Land-useplanningisbroughtwithinthescopeoftheDirective.n Safetyreports(top-tiersitesonly)havetobemadeavailabletothepublic,but
companiescanrequestthatcertaininformation,includingcommercialand personalconfidentialinformation,iswithheld.
n Thecompetentauthorities,HSEandtheEnvironmentalAgency(EA)in EnglandandWales,andHSEandtheScottishEnvironmentalProtection Agency(SEPA)inScotland,mustprohibitoperationswherethemeasures takenbyoperatorstopreventandmitigatemajoraccidentsareseriously deficient.
TheSevesoIIrequirementsplacemuchmoreemphasisonthemanagementofsafetyandtheroleofthesafetyreportthanintheoriginalSevesoDirective(implementedbytheCIMAHRegulations).Paragraphs11-23summarisethemainrequirementsofotherlegislationthatisrelevanttothecontrolofrisksposedbyinstallationshandlingchlorine.
THE PLANNING (HAZARDOUS SUBSTANCES) ACT 1990 AND PLANNING (HAZARDOUS SUBSTANCES) REGULATIONS 1992 7
11 TheActandRegulationsintroduceplanningcontrolswhicharedesignedtoensurethathazardoussubstancescanbekeptorusedinsignificantamountsonlyaftertheresponsibleauthoritieshavehadtheopportunitytoassessthedegreeofrisktopeopleinthesurroundingareaandaresatisfiedthattherisksaretolerable.InessencetheActandRegulationsrequiresitestoapplyfor‘hazardoussubstancesconsent’forinventorylevelsatorabovespecificamountsknownasthe‘controlledquantity’-10tonnesinthecaseofchlorine.Neighbouringsiteswithin500m,andcontrolledbythesameperson,mustbetakenintoaccountwhendecidingthemaximuminventory.Newsitesmustobtainhazardoussubstancesconsentatanearlystageinthelifecycle.
12 InEnglandandWalesthecontrolsareenforcedbytheHazardousSubstancesAuthority(HSA),usuallytheDistrictorLondonBoroughCouncilforthelandinquestion,ietheLocalPlanningAuthority(LPA).InScotlandtheequivalentregulationsareTheTownandCountryPlanning(HazardousSubstances)(Scotland)Regulations1993.TheyareenforcedbytheScottishOffice,EnvironmentDepartment(SOED).HSEisastatutoryconsulteeundertheActandadvisesHSAsandSOEDonthenatureandseverityoftheresidualrisk.TheActrecognisesthatsafetymustbeanoverridingcontrol.Thecontrolsapply,regardlessofwhetherplanningpermissionisrequiredunderotherlegislation.
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13 GuidanceonapplyingforhazardoussubstancesconsentinEnglandandWalesisgiveninHazardous Substances Consent: Guidance for Industry(producedbytheDepartmentoftheEnvironmentandtheWelshOffice,92PLAN0001).SOEDhasissuedcircular16/1993Hazardous Substances Consent: Guidance for Industry.
THE DANGEROUS SUBSTANCES (NOTIFICATION AND MARKING OF SITES) REGULATIONS 1990 39,40
14 Wheremorethan25tonnesofdangeroussubstancesarepresentonasite(includingchlorine)notificationmustbemadetothefireauthorityandappropriatesignsplacedatsiteaccesspoints.TheenforcingauthorityisthefireauthorityexceptinspecifiedcircumstanceswhenitisHSE.TheRegulationsrequireallsignstoconformtoBS537841andtobekeptcleanandfreefromobstructions.
THE MANAGEMENT OF HEALTH AND SAFETY AT WORK REGULATIONS 1992 18
15 TheseRegulationsimplementCouncilDirectives89/391/EEC(OJNoL183,29.6.89,p1)and91/383/EEC(OJNoL206,29.7.91,p19)ontheintroductionofmeasurestoencourageimprovementsinsafetyandhealthofworkersatwork.UndertheRegulationsyoumust:
(a) assesstheriskstothehealthandsafetyofyouremployeesandnon-employees arisingin,orfrom,youractivitiesandreviewtheassessmentwhenthereis significantchange.Recordsofsignificantfindingsoftheassessmentmustbekept wheretherearefiveormoreemployees;(b) plan,organise,control,monitorandreviewthepreventativeandprotectivemeasures takenasaresultoftheassessment;(c) appointanycompetentperson(s)neededtohelpyoucomplywithlegalobligations, forexample,whenhavingpressuresystemsexamined;(d) setoutwhatshouldbedoneincaseofseriousandimminentdangeratyour premises,suchasthespillageofanappreciableamountofchlorine;(e) tellemployeesabouttherisksandprecautionsinvolvedintheirwork;and(f) providehealthsurveillancewherenecessary.
THE LIFTING PLANT AND EQUIPMENT (RECORDS OF TEST AND EXAMINATIONS ETC) REGULATIONS 199289,90
16 Youmust:
(a) havecertificatesoftestandexamination(normallyprovidedbymanufacturersand suppliers)specifyingsafeworkingloadsbeforefirstusingchains,ropesandlifting tackle;(b) havechains,ropes,liftingtackle,hoistsandliftsthoroughlyexaminedeverysix monthsbyacompetentperson(oftenemployedbyaninsurancecompany)and obtainandkeepthereport;(c) ensuretestsandthoroughexaminationsofcranesarecarriedoutbeforetheyare firstusedandobtainacertificateoftestandexaminationspecifyingsafeworking loads.Periodicthoroughexaminationsatleastevery12monthsarealsorequired, forwhichareportshouldbeobtainedandkept.
HSEguidanceisavailable.90
Note:TheseRegulationswillberevokedandreplacedinDecember1998bytheLiftingOperationsandLiftingEquipment(LOLER)Regulations(SI1998/2307).GuidancewillbepublishedinanApprovedCodeofPracticeonSafeUseofLiftingEquipment.TheProvisionandUseofWorkEquipmentRegulations1998(seeparagraph19)alsoapplytoliftingequipment.
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THE MANUAL HANDLING OPERATIONS REGULATIONS 1992 57
17 TheseRegulationsimplementthesubstantiveprovisionsofCouncilDirective90/269/EEC(OJNoL156,21.6.90,p9)onthehealthandsafetyrequirementsforthemanualhandlingofloadswherethereisariskofbackinjurytoworkers.Employersmust:
(a) avoidtheneedforhazardousmanualliftingandhandlingifreasonablypracticable;(b) assesstheriskofinjuryfromanyhazardousmanualliftingandhandlingwhich cannotbeavoided;and(c) reducetheriskofinjuryaccordingly.
Employeesmust:
(a) followsafesystemsofworklaiddownbytheiremployers;(b) usemechanicalaidsprovidedbytheiremployersproperly;and(c) remembertousethetrainingprovidedonlifting.
THE CONTROL OF SUBSTANCES HAZARDOUS TO HEALTH REGULATIONS 1994 20
18 Theseregulationsre-enact,withminormodifications,theCOSHHRegulations1988(SI1988/1657).Theyimposerequirementsonemployersusingsubstanceshazardoustohealthtoprotectemployeesandotherpeoplewhomaybeexposedtosuchsubstances.Theyalsoimposecertaindutiesonemployeesconcerningtheirownprotectionfromexposure.
Employersmust:
(a) assessriskstohealth;(b) preventexposure;(c) wherepreventionisnotreasonablypracticable,controlexposureby,forexample, isolatingorenclosingtheprocessor,ifthisisnotreasonablypracticable,local exhaustventilation;(d) maintaincontrolmeasuresinefficientworkingorderandensurethatathorough testandexaminationofengineeringcontrolsarecarriedoutatsuitableintervals. Recordsofsuchmaintenancemustbekeptforatleastfiveyears;(e) wherepreventionorcontrolisinsufficientonitsown,providepersonalprotective equipmentandmaintainit;(f) inform,instructandtrainemployees;and(g) carryoutairmonitoringandhealthsurveillancewherenecessary.
THE PROVISION AND USE OF WORK EQUIPMENT REGULATIONS (PUWER) 1992 55,56
19 TheseRegulationsimposehealthandsafetyrequirementswithrespecttotheprovisionanduseofworkequipment(machinery,appliances,toolsetc).Theyimposerequirementsuponemployers,includingtheneedto:
(a) provideworkequipmentthatissuitableforthepurposeforwhichitisusedor supplied;(b) takestepstoensurethattheequipmentisnotusedunderconditionsforwhichitis notsuitable;(c) maintainworkequipmentinanefficientworkingorderandgoodrepairandthatany maintenancelogiskeptuptodate;(d) providepeoplewhouseworkequipmentwith:
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(i) clearhealthandsafetyinformationand,whereappropriate,written instructions;and (ii) adequatetraining,includingtherisksinvolvedandtheprecautionstobe taken.(Thisalsoappliestosupervisorsandmanagersofsuchpeople.)(e) protectpeoplefromdangerouspartsofmachinerybysuitableprotectiondevices;(f) providesuitableandsufficientlightingatanyplacewhereapersonuseswork equipment;(g) ensurethatworkequipmentismarkedinaclearandvisiblemannerwith appropriatehealthandsafetyinformationandwarnings;and(h) ensurethatanywarningdeviceisunambiguousandeasilyperceivedand understood.
Note:TheseRegulationswillberevokedandre-enactedinDecember1998.ThenewPUWERRegulations(SI
1998/2306)includenewprovisionsformobileworkequipment.
THE CONFINED SPACES REGULATIONS 1997 59,60
20 TheseRegulationsapplywhenitisnecessaryforworkerstocarryoutworkinaconfinedspaceincludingachamber,tank,flueorasimilarspace,which,byvirtueofitsenclosednature,givesrisetoa‘foreseeablespecifiedrisk’.Inthecaseofchlorineinstallationsthemostlikelyforeseeablespecifiedriskis‘thelossofconsciousnessorasphyxiationofanypersonatworkarisingfromgas,fumevapourorthelackofoxygen’.TheRegulationsprohibittheentryintoaconfinedspaceforthepurposeofcarryingoutworkwhereitisreasonablypracticabletocarryouttheworkbyothermeans.Inothersituations(forexample,theisolationofaleakinachlorineroom)theyimposerequirementsonemployersincludingtheneedto:
(a) establishsafesystemsofworkforentryto,orcarryingoutworkin,orleavinga confinedspacethatrenderstheactivitiessafeandwithoutriskstohealth;(b) establishsuitableandsufficientarrangementsfortherescueofpeopleinthe confinedspaceintheeventofanemergency;(c) ensurecompliance,sofarasisreasonablypracticable,withtheprovisionsofthe Regulationsinrespectofanyworkcarriedoutbyemployees,orotherpeople-in whichcasethemattersneedtobewithintheemployer’scontrol.
THE PRESSURE SYSTEM AND TRANSPORTABLE GAS CONTAINERS REGULATIONS 1989 23,24,25
21 TheseRegulationsimposerequirementsforpressuresystemscontainingagasorliquefiedgasatapressuregreaterthan0.5baraboveatmosphericpressure.Theyimposerequirementsondesigners,suppliersofpressuresystemsandonemployersofpeoplewhomodifyorrepairsuchsystems.TheintentionoftheRegulationsistopreventtheriskofseriousinjuryfromstoredenergyasaresultofthefailureofapressuresystemorpartofit.Ameasureofthestoredenergyisgivenbymultiplyingthesystempressure(bargauge)andvolume(litres).Apressuresystemis:
(a) asystemcomprisingoneormorepressurevesselsofrigidconstruction,any associatedpipeworkandprotectivedevices(systemswithastoredenergyof250 barlitreorlessareexemptfromsomerequirements,egthewrittenschemeof examination);(b) thepipeworkwithitsprotectivedevicestowhichatransportablegascontaineris,or isintendedtobe,connected;or(c) apipelineanditsprotectivedevices.
Thetransportablegascontainerisnotpartofthesystem.Employersmustensurethat:
(a) allplantandsystemsaredesigned,constructedandinstalledtopreventdanger;(b) systemsareproperlymaintained;
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(c) modificationsorrepairsdonotcausedanger;(d) thereisawrittenschemeforexamination54ofcertainpressurevessels,suchas chlorinevaporisers,fittingsandpipework,drawnupbyacompetentperson;(e) examinationsassetoutinthewrittenschemearecarriedoutbyacompetent person;and(f) recordsarekept.
Note:The transportable gas container (TGC) part of these Regulations was revoked in 1996 and incorporated into The Carriage of Dangerous Goods (Classification, Packaging and Labelling) and Use of Transportable Pressure Receptacles Regulations 1996. These PSTGC Regulations will be replaced in November 1999 by The Pressure Equipment Regulations and The Pressure Systems Safety Regulations.
THE PERSONAL PROTECTIVE EQUIPMENT AT WORK REGULATIONS 1992 63,64
22 TheseRegulationsimposehealthandsafetyrequirementswhenprovidingPPEandusingittoprotectpeopleintheworkplace.Employersmust:
(a) providesuitablePPEfreeofchargetoprotectemployeesagainstriskswhich havenotbeencontrolledbyothermeans;(b) takeallreasonablestepstoensureitisproperlyused;(c) beforeprovidingPPE,assessriskstohealthandsafetywhichhavenotbeen avoidedbyothermeansanddefinethecharacteristicsrequiredbyPPEtomakethe risksALARP;thenselectsuitablePPEbymatchingthosecharacteristicswiththose ofPPEavailable;(d) maintainthePPEprovidedincleanandefficientworkingorderandprovidesuitable storageforitwhennotinuse;and(e) giveinformation,instructionandtraining.
Employeesmust:
(a) usePPEprovided;and(b) reportanylossorobviousdefecttotheemployer.
THE REPORTING OF INJURIES, DISEASES AND DANGEROUS OCCURRENCES REGULATIONS (RIDDOR) 1995 91,92,93
23 Theseapplytoallemployersandself-employedpeopleandcovereveryoneatwork.Themainpointsarethatyoumust:
(a) notifyyourinspectorimmediately,normallybytelephone,ifanybodydies,receives amajorinjuryorisseriouslyaffectedby,forexample,anelectricshockorpoisoning;(b) notifyyourinspectorimmediatelyifthereisadangerousoccurrence,egafireor explosion,whichstopsworkformorethan24hours;(c) confirmtelephonenotificationsinwritingwithintendaysonF2508;(d) reportwithinsevendays(onformF2508)injurieswhichkeepanemployeeoffwork orunabletodotheirnormaljobformorethanthreedays;(e) reportcertaindiseasessufferedbyworkersonformF2508A;and(f) keepdetailsofreportedincidents.
ENFORCING THE LAW
24 HealthandsafetylawsrelatingtoyourfirmwillusuallybeenforcedbyahealthandsafetyinspectorfromHSE.Insomecases,egapublicswimmingpool,healthandsafetylawisenforcedbythelocalauthority.
25 Inspectorsmayvisitworkplaceswithoutnoticebutyouareentitledtoseetheiridentificationbeforetheycomein.Theymaywanttoinvestigateanaccidentorcomplaint,orinspectsafety,healthandwelfareatyourpremises.Theyhavetherighttotalkto
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employeesandsafetyrepresentatives,takephotographsandsamples,andevenincertaincasestoimpounddangerousequipment.Theyareentitledtoco-operationandanswerstoquestions.
26 Inspectorswillbeawareofthemainrisksinhandlingchlorineandwillgiveyouhelpandadviceonhowtocomplywiththelaw.Ifthereisaproblem,theymayissueaformalnoticerequiringimprovementsor,whereseriousdangerexists,onewhichprohibitstheuseofaprocessorequipment.Inspectorshavepowerstoprosecuteafirm(oranindividual)forbreakinghealthandsafetylaw.
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Appendix 4 Useful contacts and standardsCHLORINE PRODUCERS AND SUPPLIERS
Hays Process ChemicalsSandbach,CheshireCW113PZ
Imperial Chemical Industries plc, Chlor ChemicalsPOBox13,TheHeath,Runcorn,CheshireWA74QF
Rhodia LtdStaveley,ChesterfieldS432PB
The Associated Octel Co LtdPOBox17,EllesmerePort,Wirral,CheshireL654HF
BOC Ltd Special Gases24DeerParkRoad,LondonSW193UF(Note:BOCsuppliesonlycylinders.)
Air Products (GB) LtdSpecialityGasesDepartment,WestonRoad,CreweCW11DF(Note:AirProductssuppliesonlydrumsandcylinders.)
OTHER USEFUL CONTACTS
Chemical Industries Association(CIA)KingsBuildings,SmithSquare,LondonSW1P3JJTel:01718343399
TheCIArunsachlorinecommitteedealingwithtechnicalandliaisonissues.
Water Services Association of England and Wales1QueenAnne’sGate,LondonSW1H9BTTel:01719574567;Fax:01719574666
HSE
YoucanfinddetailsofyourlocalHSEofficeinyourlocaltelephonedirectoryorthecurrenteditionofHSE35The Health and Safety Executive: Working with employers,availablefromHSEBooks.
YoucanfinddetailsofHSEBooksandHSE’senquiryserviceontheinsidebackcoverofthisbooklet.
Chlorine InstituteInc.2001LStreet,NW,WashingtonDC20036USA
Euro ChlorAvenueEVanNieuwenhuyse4,Box2,B-1160Brussels,BelgiumTel:+3226767211;Fax:+3226767241
EuroChlorpublishesawiderangeofrelevantreports.22Thenewseries(AP)ofpamphletsonlearning from accidentsisessentialreading(egseereference82).
UK suppliers of Euro Chlor approved globe valves
Descote Ltd19SandyLane,WestonPoint,Runcorn,CheshireWA74EXTel:01928565666;Fax:01928565646
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Shaw, Son & Greenhalgh Ltd AlbertStreet,Lockwood,HuddersfieldHD13QGTel:01484532425;Fax:01484512426
British Standards Institute
BSISalesandCustomerServices,389ChiswickHighRoad,LondonW44ALTel:01819967000;Fax:01819967001
BritishStandardsareavailablefromtheaboveaddress.
Standards relevant to chlorine
Specification for pipe threads for tubes and fittings where pressure-tight joints are made on the threads (metric dimensions)BS21:1985
Specification for liquid chlorineBS3947:1976(1997)
Specification for filling ratios and developed pressures for liquefiable and permanent gasesBS5355:1976
Specification for unfired fusion welded pressure vesselsBS5500:1997
Specification for flat products made of steels for pressure purposesBSEN10028:Parts1,2,3:1993and4:1995
Specification for tolerances on dimensions, shape and mass for hot rolled steel plates 3 mm thick or aboveBSEN10029:1991
Circular flanges for pipes, valves and fittings. Part 3: Section 3.1 Specification for steel flanges. Part 3 Section 3.3 Specification for copper alloy and composite flangesBS1560:Part3:1989
Specification for bolting for flanges and pressure containing purposesBS4882:1990
Specification for compressed asbestos fibre jointingBS1832:1991(1997)
Specification for bursting discs and bursting disc devicesBS2915:1990
Transportable gas containers. Part 1 Specification for seamless steel gas containers above 0.5 litre water capacityBS5045:Part11982;Part 2 Specification for steel containers of 0.5 L up to 450 L water capacity with welded seamsBS5045:Part21989
Specification for filling ratios and developed pressures for liquefiable and permanent gasesBS5355:1976
Safety signs and colours. Part 1 Specification for colour and designBS5378:Part11980(1995);Part 3 Specification for additional signs to those given in BS 5378: Part 1BS5378:Part31982(1995)
Polytetrafluoroethylene (PFTE) materials and products. Specification for fabricated unfilled polytetrafluoroethylene productsBS6564:Part21991(1996)
Specification for identification of pipelines and servicesBS1710:1984(1991)
Schedule of paint colours for building purposesBS4800:1989(1994)
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Guide to implementing an effective respiratory protective device programme BS4275:1997
Specification for respiratory protective devices: self-contained open-circuit compressed air breathing apparatusBSEN137:1993
Respiratory protective devices: compressed airline breathing apparatus for use with a full face mask, half mask, or mouthpiece assembly. Requirements, testing, markingBSEN139:1995
Steels for pressure purposes. Part 3 Specification for corrosion and heat-resisting steels: plates, sheet and stripBS1501:Part31990
Specification for steels for fired and unfired pressure vessels: sections and bars BS1502:1982(1990)
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Appendix 5 Outside installations and inside installations1 Bulkchlorineinstallationsshouldpreferablybelocatedintheopenair.Sometimesitmaybeappropriatetolocatetheinstallationinabuilding.
2 Thebuildingmayenclosetheentireinstallationorpartofit,egthemanlids,valves,associatedpipework,gaugesandotherequipment,leavingthetankitselfoutside.
3 Theadvantages,disadvantagesandconsequentrequirementsforoutsideorinsideinstallationsarelistedinparagraphs4-8.
OUTSIDE INSTALLATIONS
4 Theadvantagesofoutsideinstallationsarethat:
(a) leakagesarenotconfined,sothesourceofleakageismoresafelyaccessiblefrom upwind;(b) itiseasiertoidentifythepointofleakageandtakeimmediatelocalcorrectiveaction;(c) accessforinstallationandformajormaintenanceissimpler;and(d) buildingcostsarelower.
5 Thedisadvantagesofoutsideinstallationsarethat:
(a) leakagesmaybedetectedatanearlystageonlyfromdownwindpositions;(b) smallleakages,particularlythosearisingfromcorrosion,candevelopunnoticed;(c) maintenanceandrepairworkmayhavetobecarriedoutinadverseweather conditions;(d) thereisnocontainmenttoreducetherateofreleasetotheatmosphere;(e) surfacecorrosionismorelikely;anyleakmayrapidlyescalate;and(f) thereislesssecurity.
6 Itfollowsthatoutdoorinstallationsrequire:
(a) strictvigilanceandprotectionagainstcorrosion;(b) protectionagainstpossiblemechanicaldamageandunauthorisedaccess;(c) anappropriateemergencysystem,possiblyincludingproceduresfortheuseof waterspraysforgasclouds(seealsomaintextparagraphs247-263);(d) weatherprotectionformaintenanceincriticalareas;thiscouldbeeitherapermanent canopyortemporarysheeting;and(e) continuousstaffingonthesiteifachlorinereleasecouldpresentserious consequencesonoroffsite.
INSIDE INSTALLATIONS
7 Theadvantagesofinsideinstallationsarethat:
(a) valvesandotherequipmentareprotectedfromrainandsnow,andprovided thebuildingiskeptdry,therewillbelessriskofcorrosion;(b) backgroundheatingispossible,tohelpprovidedrysurroundingsand increasedchlorinevapourpressureforprocesseswhereinertgas/airpadding isnotacceptable;(c) controlledventilationispossible,limitingtheexternaleffectsiftheleakis fairlysmall;
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(d) thereisgreaterlikelihoodofamonitoringdevicedetectingaleak;thisisa particularadvantageonanunattendedplant;and(e) theinstallationisprotectedfromaccidentalmechanicaldamage,explosionorfirein adjacentplantorinterferencebyunauthorisedpersons.
8 Thedisadvantagesofinsideinstallationsarethat:
(a) followingamediumormajorleak,emergencyaccessmayhavetobemadetoa closedroomwithahighchlorineconcentration;(b) thepointofleakagemaybedifficulttoidentify,owingtolackofdispersion,andmist formation;(c) ifthebuildingisheated,therewillbegreatergroundevaporationandflashfroma liquidleak;and(d) accessformaintenanceislikelytobemoredifficult.
9 Itfollowsthatindoorinstallationsrequire:
(a) adequateforcedventilationsystems,includingstart-upfromoperatingpoints outsideaswellasinsidethebuilding;and(b) carefulconsiderationofplantlayoutandprovisionofadequateescaperoutesand escaperespiratoryequipment.
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Appendix 6 Procedures for discharging road tankers of chlorineNote: This typical procedure assumes that the storage tanks and associated items of equipment have a safe working pressure of at least 12 bar gauge. If this is not the case, then steps will need to be taken (eg adjust the air system pressure, and relief valve settings) to ensure that the safe working limits for the storage vessels and delivery system are not exceeded. It is important that more detailed and site-specific procedures are developed and agreed by the customer, haulier and chlorine supplier.
Action by Action needed
Joint 1Theproceduresneedtobedesignedtominimisepotentialleaksbyensuringthatallnewlymadejointsaretestedbygaspressurewith,atmost,onlyasmallamountofliquid.Duringthesetestoperationsagasmaskmustbeworn.Similarly,asuitablegasmask(seeparagraphs235-246)mustbewornduringthedisconnectingoperationwhenthereisapossibilityoftheescapeofasmallquantityofresidualvapour.Duringtherestoftheoperationsitshouldbekeptreadilyavailable.
Customer 2 Willoperateallvalvesonthebulkstorageinstallation,includingthe fillingpipe.
Driver 3 Onarrivalattheworks,willweighoffonthesiteweighbridgeand proceedtothedischargeberth.
Driver 4 Willpositionthetankeratthedischargeberthandemploythe drive-awayprotection.Avarietyoftechniquesmaybeused,eg interlockstothetankerbrakes,wheelchocks,andtheremovalofthe vehicleignitionkeytoacontrolledlocation.Theseareinaddition (seeparagraph7below)toanydrive-awayprotectionbarriersandany interlockstoshutdownthedischargeshouldmovementofthevehicle orshouldchlorinebedetected(seemaintext,paragraphs39-41).
Driver 5 Presentsthedeliverynotestoaresponsibleofficial.
Insigningthesenotesthecustomeracceptstheresponsibilitythat thereissufficientspaceavailableinthestoragetanktoreceivethe fullloadfromtheroadtankandthattheinstallationisfitandreadyfor thedischargetoproceed.
Driver 6 Willtelltheplant operatortheweightofchlorineinthetankerso thattheoperatorcandeterminewherethefinalreadingwillbeonthe weighingmachinedialorloadcellindicator.
Customer 7 Willensurethatanywarningnoticesaredisplayedandbarriers areerected,andwilloperateanysafetyinterlocksassociatedwith theroadvehicleberth.
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Customer 8 Wheretherearetwoormoretanksthe customerwilldetermine whichtankistoreceiveandcheckthatthestoragetankcannotbe overfilled.Thepressureonthetankbeforestartingthedischarge shouldnotnormallybegreaterthan5.9bargaugebutinveryhot weatheritmaybehigher.
Customer 9 Thecustomerwillensurebeforedischargethattheventvalve onthestocktankfillingpipeisclosed.Whenfitted,thebarrier mechanicalinterlockkeyisusedtoactivatethecontrolpanel sequenceforthedischargingoperationandreleasetheoff-loading arm.
Driver 10Establishthevehiclemovementdetectioninterlockandactivate interlockstothechlorinedetectionsystembeforeoperatingvalves onthetankerandinstallation.Wearingagasmask,removebothcaps fromtheroadtankvalvesandthecustomer’sfillingarmsandtestfor leaks.UsingnewPTFE,aramidfibreorothersuitablematerialforjoint rings(preferablynotCAF,seeparagraph56),connectbothairsupply andliquiddischargearmstotheappropriatevalvesonthetanker.
Joint 11Wearingagasmask,applypressuretothedischargeconnection, preferablybybrieflyopeningthevalvetothestocktank.Analternative butlessdesirablemethodistoopenthetankerdischargevalve momentarily.Thedriver(wearingagasmask)teststhejointsonthe dischargepipeusingammoniawater.Ifsatisfactory,thedrivercan removehisgasmaskandthenrequesttheplantoperatortoopenthe valveonthestockfillinglineafterthedroparm.Theliquidvalveonthe tankercanbeslowly openedtofillthedeliveryline:thepressure observedwillbethepressureontheroadtanker.Alternatively,and onlywhenthedriverissatisfiedwiththeintegrityoftheconnections, theinstrumentairconnectionsaremadewhichwillallowthe dischargevalvestobeoperated.Thismayalsoactivateabrake interlockwhichisintegralwiththecustomer’sshutdownsystem.
Joint 12Starttheaircompressorandwhenthelinepressureis8.3 bargaugeopenittotheroadtanker.Whentheroadtankerpressure (asindicatedonthefillingpipetothestocktank)is1.7bargauge abovethatofthestocktankrequesttheplant operatortoopenthe valvetotheappropriatestocktankandcommencedischargeofthe roadtanker.
Joint 13Observethedischargeoftheroadtankerisproceeding satisfactorilybyreferencetotheweighingmachinedialorloadcell indicator.
Joint 14Observethestocktankpressureasthedischargeisproceeding. Shouldthisrisesto6.2bargaugethedriverrequeststhecustomerto crackopentheventvalveonthetanktoreducethepressure.
Joint 15Indicationthattheroadtankerhasbeencompletelydischargedis:
(a) fluctuationofpressuregaugeontheliquidchlorinedeliveryline; (b)equalisationoftankerandlinepressurereadings.Joint 16Theplantoperatorclosesthestoragetankinletvalveandthe paddingairsupplyvalve.Ventexcesspressurefromthetankerviathe ventvalvetothescrubber.Thedriverthenclosesthepaddingairinlet tothetankerandtheliquidchlorineoutletfromthetanker,and
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disconnectstheoperatingairleadstothemsothetankervalves cannotbereopened.Theconnectingpipeforpaddingaircan nowbeventedanddisconnectedandthetankerpaddingair connectioncapped.Theoperatorcracksopentheventvalveonthe liquidchlorinedeliverylinetothestocktankfillingpipe.Whenthe pressuregaugeontheliquidchlorinedeliverylineshowszero(and anyhoarfrostontheventvalvehasbeguntodisappear)the operatorclosesthevalveonthechlorinedeliverylineatthetanker dischargepoint.Closethedeliverylineventvalve.
Customer 17 Crackopentheventvalveonthestocktankforaboutoneminute inordertocheckthatthelevelofliquidchlorineinthetankisbelow thebottomoftheventdippipe(nofrostingshouldappear).This operationalsoventsnon-condensablegases.Checkthatthepressure inthetankisreasonableforthetemperatureofthechlorine.The storageisnowisolatedfromthedischargelinetothescrubberand thedeliverylineispurgedbypressurisinganddepressurising(open ventvalveandcloseitwhenpressuregaugeshowszero)withdryair foraminimumoffivecycles.Theoperatorcannowshutdowntheair compressorifitisnotneededforotheroperations.
Driver 18Wearingagasmask,disconnecttheliquiddischargepipefromthe tanker,replacethesealingplugtopreventtheentryofmoistair,and swivelbacktothestaging.Telltheplant operatorthattheventcanbe closed.Theshortconnectingpipesfromtheliquidandairvalvescan bedisconnected,bothvalvescappedandthetankerdomesecurely fastened.TheRPEcannowberemoved.
Customer 19 Under no circumstances allow any section of the pipeline to be left unvented with liquid chlorine trapped between closed valves.
Driver 20Beforeleavingthestorageplantaskthedesignatedresponsible persontosigntheadvicenoteandconsignmentnoteafterthewords ‘alloperationsconnectedwiththedischargeoftheroadtankhave beencompletedsatisfactorily’.Handonecopytotheresponsible person.Onleavingtheworksweighagainonthesiteweighbridge.
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Appendix 7 Types of vaporiserChlorinevaporisersmaybedividedintofourbasictypes:
(a) Verticaltubebundle.(b) Coiledtubeimmersedinaheatingbath.(c) Concentrictube.(d) Kettle-typeevaporator.
VERTICAL TUBE BUNDLE (TYPE 1)
1c Hotwaterbath
1b Steambayonet
1a Shellandtube
Advantagesofthistypeofsystemare:
(a) smalloverallsizeforrelativelylargeheattransfersurfaces;(b) easymaintenance;and(c) forthemodeofoperationinwhichthechlorineisintubes,theliquidchlorineis automaticallydisplacedbyover-pressurewhenthevapoursupplytotheconsuming plantisshutoff.
Disadvantagesofthistypeofsystemare:
(a) forthemodeofoperationinwhichthechlorineisinthetubes,thereisariskof instabilityathighthroughputowingtovariationofliquidlevelsandapossibilityof corrosionintheregionoftheliquidsurface;and(b) forthemodeofoperationinwhichthechlorineisintheshell,itisdifficulttodryout theshell.
COILED TUBE IMMERSED IN A HEATING BATH (TYPE 2)
2 Coilinbath
Steam
Condensate
Liquid chlorine
Chlorine gas Liquid chlorine
Electric heater
Water bath
Chlorine gas
Liquid chlorine
Chlorine gasCoil
Steam
Hot water bath
Hot water outlet
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Advantagesofthistypeofvaporiserare:
(a) itissimpletomaintainandoperate;(b) thelongcoilgenerallyensuresadequatesuperheating;(c) therearenoproblemswithdifferentialthermalexpansion;(d) plugflowoperationavoidsconcentrationofhighboilingimpurities;(e) dryingoutofequipmentbeforeuseisrelativelyeasy;and(f) liquidchlorineisautomaticallydisplacedwhenthevapoursupplytotheconsuming plantisshutoff.
Disadvantagesofthistypeofvaporiserare:
(a) lowthroughput;(b) externalcorrosionofthetubecaneasilyoccur,especiallyneartheliquid surface;(c) irregularinternalerosionofthecoilmayoccur;and(d) internalinspectionandcleaningofthecoilisdifficult.
CONCENTRIC TUBE UNITS (TYPE 3)
3 Concentrictubeunit
Advantagesofthistypeofsystemare:
(a) simpleconstructionwithminimumweldingrequirements;(b) easymaintenanceandoperation;(c) easyprovisionofadequatecorrosionallowance;(d) automaticdisplacementofliquidchlorinewhenthevapoursupplytotheconsuming plantisshutoff;and(e) plug-flowoperationaboveacertainminimumflowavoidsconcentrationofhigh boilingimpurities.
Disadvantagesofthistypeofsystemare:
(a) potentialinstabilityofoperationathighandlowthroughput;(b) limitationofunitcapacityowingtorelativelysmallheattransfersurfacearea;and(c) greaterdifficultyinobtainingadequatesuperheatingofthechlorine.
Liquid chlorine
Chlorine gas
Condensate
Steam
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KETTLE-TYPE EVAPORATOR (TYPE 4)
4 Kettle-typeevaporator
Advantagesofthistypeofsystemare:
(a) itcanbedesignedforlargethroughput;(b) allowanceforthermalexpansioncaneasilybemade;and(c) operationisstable,providedthateitherthelevelofchlorineinthekettleorthe pressureofchlorinefedtothevaporiser,iscontrolled.
Disadvantagesofthistypeofsystemare:
(a) sincethevesselcontainsarelativelylargeamountofliquidchlorine,leakageor excesspressureinthevesselposeagreaterpotentialhazard;(b) areliefsystemwithalargecapacityisrequired,unlessthevaporiserisdesignedfor highpressure;(c) operationcanresultinconcentrationofnitrogentrichloride;thepurgingprocess requiredtoreducethishazardmaybedifficulttocarryoutonconsumerpremises;(d) dryingoftheequipmentonthechlorinesideisdifficult;and(e) dismantlingofthetubesisdifficultandrequiresalargespace.
Liquid chlorine Chlorine gas
Liquid CI
Heating medium in
Heating medium out
Heating Coil
Control to inlet
Levelmeasuringdevice
2
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Health and Safety Executive
Appendix 8 Emergency plans(Note:A fuller discussion of emergency plans appears in HSE’s HSG2569 and references 17, 70 and 71. Additional guidance will be issued to support the COMAH Regulations.)
1 Theworksshouldhaveanon-siteemergencyplanfordealingwithamajorchlorinerelease.Theplanshouldincludeinstructionsfortheemergencyteamandfornon-essentialpersonnel,andforliaisonwiththeemergencyservices.Theemergencyplanshouldbebasedonparagraphs247-263.Yourplanwilldependontheresultsofyourriskassessmentandtheneedtocomplywithhealthandsafetylegislation,egsection3oftheHSWAct.2Thefollowingparagraphscontainsomeelementsofaplan.
2 Theplanmayincludedetailedinstructionsfor:
(a) raisingthealarm;(b) investigatingandassessingthesourceandextentofthechlorinerelease;(c) alertingallpersonnelon-siteorinneighbouringpremisesandtheemergency services;settingupemergencycontrolcentres,assessmentbykeypersonnelofthe incidentandconsequentemergencymeasuresonandoff-site;(d) methodsforcontrollingthechlorinerelease;(e) searchsystemsforcasualties,andaccountingforpersonnelon-site;(f) methodsforassessingthedirectionalspreadandconcentrationofthegascloud;(g) criteriafordeterminingwhethertoevacuatenon-essentialpersonnelortoadvise themtostayinsidebuildingswithdoors,windowsandventilationshut;(h) methodsforassessingwhethercorrespondingactionsareadvisableforpeople off-siteand,inparticular,liaisonwiththemanageratanyadjacentunderground workingswherechlorinecouldentertheventilationsystem;advicetoemergency servicesonthedirection,spreadandconcentrationofthegascloud;and(i) firstaidtoon-sitecasualties,andarrangementsforevacuationwhereadvisableand practicable;advicetoambulanceserviceonroutestouse.
3 Sinceeachinstallationwillhaveitsownspecialfeatures,adetailedplanrelatingtotheparticularplantwillberequired.Localmanagementshouldberesponsibleforpreparationoftheplanwhichshouldbedevelopedinco-operationwiththelocalauthority,thepolice,fire,hospitalandambulanceservices,andthechlorinesupplier.SpecificdutiesarelaidonsomeofthesepeoplebytheControlofIndustrialMajorAccidentHazardsRegulations1984.ThesewillbesupersededbytherequirementsoftheCOMAHRegulationsin1999.
EMERGENCY CONTROL CENTRES
4 Basicrequirementsforasatisfactorysystemtodealwithanemergencyresultingfromaseriousescapeofchlorineareoutlinedasfollows:
(a) twocontrolcentresshouldbeprovidedsothat,intheeventofagasescape, operationscanbecontrolledfromthecentrewhichisleastaffectedunderprevailing atmosphericconditions;(b) eachcentreshouldbeprovidedwithaseparateexternaltelephoneline,aswellas withconnectionstothefactory’sexternalandinternaltelephonesystem;(c) adequateemergencyequipment(self-containedbreathingapparatus,suppliesof suitablefoamasagreedwiththeemergencyservices,protectiveclothing,etc) shouldbeavailable(seesectiononemergencyequipment);(d) emergencyfirst-aidfacilities,includingequipmentforadministeringoxygen,needto beprovided;(e) alarge-scalemap(1:25000or1:10000)ofthesurroundingareashouldbeavailable tohelpdeterminewhichpartsofthefactoryandthelocalneighbourhoodarelikely tobeaffected;
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Health and Safety Executive
(f) winddirectionindicatorshavetobevisiblefrom,orindicatedin,eachcontrolcentre; and(g) equipmentandinformationareneededtoassessthelikelyextentofthegascloud forvarioussizesofreleaseandvariousweatherconditions.
5 Theemergencyplanshouldspecifyinadvancetheindividualsanddeputiesresponsiblefortheactionnecessarytodealwiththeemergency.
SITE EMERGENCY TEAM
6 Thereshouldbeatrainedemergencyteamwiththefollowingkeypersonnel:
(a) Site incident controller-theseniorpersonon-siteresponsibleforthedirection ofon-siteoperations;
(b) Site main controller-normallytheworksmanagerordeputywithoverall responsibilityfortheoperationoftheemergencyplan,maintainingclose liaisonwiththepoliceandfireservices,andforadvisingthemontherisk; and
(c) Other key personnel -including:
(i) theteamresponsibleforthecontrolofthechlorinerelease; (ii) theteamresponsibleforthesearchforcasualties,forfirstaidandforthecontrol ofevacuation.
7 Thepolicewillberesponsiblefordealingwithmembersofthepublicwhomightbeaffectedbythechlorineescape;theywillneedtobeadvisedofthesizeandexpecteddurationofthereleasetogetherwiththeareaswhichcouldbeaffected,toallowthepoliceandthesitemaincontrollertoagreewhetherthepublicshouldremainindoorsorbeevacuated.
EMERGENCY ASSEMBLY AREAS
8 Emergencyassemblyareasshouldbedesignatedforuseinachlorineemergencybypersonnelnotinvolvedintheemergencyteam.Theassemblyareasallowforcountingofpersonnelandforcontrolledevacuationiftheneedshouldarise.Preferably,theassemblyareashouldbeattheperipheryoftheworkssitewithgoodexitforevacuation.Abuildingwithupperstoreysatalocationupwindofthechlorinereleasemayoffersufficientprotectionwhilethereleaseisbroughtundercontrol.Evacuationofpersonneltotheassemblyareasshouldbedirectedbyaseniormemberoftheemergencyteamwhowilltakewinddirectionintoaccount.Therewillbeoccasionswhenevacuatingoff-siteisnotthebestaction,forexample,whenthereleaseissuddenandoflimitedduration.
CASUALTIES
9 First-aidtreatmentforcasualtiesisdiscussedinAppendix1.
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References1 Safe handling of chlorine from drums and cylindersHSG40HSEBooks1999 ISBN0717616460
2 Health and Safety at Work etc Act 1974
3 List of current health and safety legislation1996HSEBooks1997 ISBN0717613119
4 The Notification of Installations Handling Hazardous Substances Regulations 1982SI1982/1357HMSO
5 The Control of Industrial Major Accident Hazards Regulations 1984 SI1984/1902HMSO
6 Council Directive 96/82/EC Control of major-accident hazards involving dangerous substancesOfficialJoftheECNoL10/40CECJanuary1997
7 The Planning (Hazardous Substances) Regulations 1992SI1992/0656HMSO
8 Risk criteria for land-use planning in the vicinity of major industrial hazards HSEBooks1989ISBN0118854917
9 Environmental Protection (Prescribed Processes and Substances) Regulations 1991SI1991/0472HMSO
10 EnvironmentalProtectionAct1990
11 AlkaliandWorksRegulationAct1906
12 Health and Safety (Emissions into the Atmosphere) Regulations 1983 SI1983/0943HMSO
13 The Carriage of Dangerous Goods (Classification, Packaging and Labelling) and Use of Transportable Pressure Receptacles Regulations 1996 SI1996/2092HMSO
14 The Carriage of Dangerous Goods by Road Regulations 1996 SI1996/2095HMSO
15 Are you involved in the carriage of dangerous goods by road or rail?INDG234 HSEfreeleaflet1996
16 Successful health and safety managementHSG65HSEBooks1997 ISBN0717612767
17 Formula for health and safety: guidance for small to medium-sized firms in the chemical manufacturing industryHSG166HSEBooks1996 ISBN0717609960
18 The Management of Health and Safety at Work Regulations1992 SI1992/2051HMSO
19 Management of health and safety at work. Approved Code of Practice. Management of Health and Safety at Work Regulations 1992L21HSE Books1992ISBN0717604128
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Health and Safety Executive
20 The Control of Substances Hazardous to Health Regulations 1994 SI1994/3246HMSO
21The Fire Precautions (Workplace) Regulations 1997SI1997/1840TSO
22 Publications: Literature and technical documentationEuroChlor1997*
23 The Pressure Systems and Transportable Gas Containers Regulations 1989 SI1989/2169HMSO
24 Safety of pressure systems. Pressure systems and Transportable Gas Containers Regulations 1989. Approved code of practice COP37HSEBooks 1990ISBN011885514X
25 A guide to the Pressure Systems and Transportable Gas Containers Regulations 1989HSR30HSEBooks1990ISBN0717604896
26 The Carriage of Dangerous Goods by road (Driver Training) Regulations 1996 SI1996/2094HMSO
27 The Carriage of Dangerous Goods by Rail Regulations 1996 SI1996/2089HMSO
28 Specification for pipe threads for tubes and fittings where pressure-tight joints are made on the threads (metric dimensions)BS21:1985
29 GEST75/45FlexibleMonelhosesforthetransferofgaseousorliquidchlorine 5thEdMay1996EuroChlor*
30 GEST75/43Flexiblesteelcoilsforthetransferofgaseousorliquidchlorine 7thEdMay1996EuroChlor.
31 GEST75/44Articulatedarmsforthetransferofgaseousorliquidchlorine 9thEdMay1996EuroChlor*
32 Process pipingB31.3AmericanSocietyofMechanicalEngineers1996
33 Chemical plant and petroleum refinery pipingSupplementtoB31.3American SocietyofMechanicalEngineers1995
34 Specification for bolting for flanges and pressure containing purposes BS4882:1990
35 Circular flanges for pipes, valves and fittings.Part3Steel,castironand copperalloyflangesBS1560:Part3Sections1-3:1989
36Pipe flanges and flanged fittingsB16-5NPS1-2throughNPS24American SocietyofMechanicalEngineers1988
37 Specification for compressed asbestos fibre jointingBS1832:1991(1997)
38 Polytetrafluoroethylene (PFTE) materials and products Part 2 Specification for fabricated unfilled polytetrafluoroethylene productsBS6564:Part2 1991(1996)
39 The Dangerous Substances (Notification and Marking of Sites) Regulations 1990SI1990/0304HMSO
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Health and Safety Executive
40 Notification and marking of sites. The Dangerous Substances (Notification and Marking of Sites) Regulations 1990. Guidance on RegulationsHSR29 HSEBooks1990ISBN0118854356
41 Safety signs and colours. Part 1 Specification for colour and designBS5378: Part1:1980/(1995);Part 3. Specification for additional signs to those given in BS 5378 Part 1BS5378:Part31982(1995)
42 Specification for identification of pipelines and servicesBS1710:1984(1991)
43 Schedule of paint colours for building purposesBS4800:1989(1994)
44 The Health and Safety (Safety Signs and Signals) Regulations 1996 SI1996/0341HMSO
45 Safety signs and signals. The Health and Safety (Safety Signs and Signals) Regulations 1996. Guidance on RegulationsL64HSEBooks1997 ISBN0717608700
46 HSCOilIndustryAdvisoryCommitteeThe safe isolation of plant and equipmentHSEBooks1997ISBN0717608719
47 Specification for filling ratios and developed pressures for liquefiable and permanent gasesBS5355:1976
48 Specification for unfired fusion welded pressure vesselsBS5500:1997
49 Specification for bursting discs and bursting disc devicesBS2915:1990
50 KletzTA Hazop and Hazan: Identifying and assessing process industry hazards3rdedIChemE1992ISBN0852952856
51 GEST76/55Maximumlevelsofnitrogentrichlorideinliquidchlorine1990 EuroChlor*
52 SafehandlingofchlorinecontainingnitrogentrichlorideChlorineInstitute Pamphlet152**
53 Introducing competent persons. Pressure Systems and Transportable Gas Containers Regulations1989INDS29HSEfreeleaflet1990
54 Written schemes of examination. Pressure Systems and Transportable Gas Containers Regulations 1989INDG178HSEfreeleaflet1994
55 Provision and Use of Work Equipment Regulations 1992SI1992/2932HMSO
56 Work equipment. Provision and Use of Work Equipment Regulations 1992 Guidance on RegulationsL22HSEBooks1992ISBN0717604144
57 The Manual Handling Operations Regulations1992SI1992/2793HMSO
58 Manual handling. Manual Handling Operations Regulations 1992. Guidance on RegulationsL23HSEBooks1992ISBN071760411X
59 The Confined Spaces Regulations 1997SI1997/1713TSO
60 Safe work in confined spaces. Confined Spaces Regulations 1997. Approved Code of Practice and Guidance L101HSEBooks1997ISBN0717614050
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Health and Safety Executive
61 Safety in pressure testingGS4(rev)HSEBooks1992ISBN0717608115
62 Permit-to-work systemsINDG98(rev3)HSEfreeleaflet1998
63 The Personal Protective Equipment at Work Regulations 1992 SI1992/2966HMSO
64 Personal protective equipment at work: Personal Protective Equipment at Work Regulations 1992. Guidance on regulationsL25HSEBooks1992 ISBN0717604152
65 GEST92/171Personalprotectiveequipmentforusewithchlorine1995 EuroChlor*
66 The selection, use and maintenance of respiratory protective equipment: A practical guideHSG531998HSEBooksISBN0717615375
67 Guide to implementing an effective respiratory protective device programme BS4275:1997
68 Prepared for emergencyINDG246HSEfreeleaflet1997
69 Control of Industrial Major Hazards Regulations 1984 (CIMAH): Further guidance on emergency plansHSG251985HSEBooksISBN0118838318
70 RobinsonBWandUKChlorineProducersGeneral guidance on emergency planning within the CIMAH Regulations for chlorine installations1986†
71 Inter-company collaboration for chlorine emergenciesCIA1992 ISBN0900623†
72 Specification for respiratory protective devices: self-contained open-circuit compressed air breathing apparatusBSEN137:1993
73 Respiratory protective devices. Compressed airline breathing apparatus for use with a full face mask, half mask or mouthpiece assembly. Requirements, testing, markingBSEN139:1995
74 Occupational exposure limitsEH40/98HSEBooks(updatedannually) ISBN0717614743
75 WHOInternationalProgrammeonChemicalSafetyEnvironmental Health Criteria 21 Chlorine and hydrogen chlorideWorldHealthOrganisation, Geneva,1982
76 Summary criteria for occupational exposure limitsEH64HSEBooks(updated annually)ISBN0717615766
77 LewisRJSax’s dangerous properties of industrial materials(9thed)Van NostrandRheinhold1996ISBN0442020252
78 TurnerRMandFairhurstSToxicology of substances in relation to major hazards: ChlorineHSEBooks1990ISBN011885528X
79 GEST89/145Guidelinesformedicalmanagementofchlorineexposure (3rded)1995EuroChlor*
80 Specification for liquid chlorineBS3947:1976(1997)
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81 GEST79/82Choiceofmaterialsofconstructionforuseincontactwith chlorine(7thed)EuroChlor1995*
82 GEST/AP1Learningfromaccidents1996.EuroChlor*
83 The setting of safety standards: A report by the interdepartmental group and external advisors 1996HMTreasury††
84 Price listHSEBooks(publishedannually)
85 A guide to risk assessment requirements: Common provisions in health and safety lawINDG218HSEfreeleaflet1996
86 Health and Safety Law. What you should know(poster)HSEBooks IBSN0717613801
87 The Health and Safety (Consultation with Employees) Regulations 1996 SI1996/1513TSO
88 A guide to the Control of Industrial Major Accident Hazards Regulations 1984 HSR21(rev)HSEBooks1990ISBN0118855794
89The Lifting Plant and Equipment (Records of Test and Examination etc) Regulations 1992SI1992/0195HMSO
90 A guide to the Lifting Plant and Equipment (Records of Test and Examination etc) Regulations 1992L20HSEBooks1992ISBN0717604888
91 The Reporting of Injuries,Diseases and Dangerous Occurrences Regulations 1995SI1995/3163HMSO
92 A guide to the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 1995L73HSEBooks1996ISBN0717610128
93 Everyone’s guide to RIDDORHSE31HSEfreeleaflet1996
Thefutureavailabilityandaccuracyofthereferenceslistedinthispublicationcannotbeguaranteed.CurrentRegulations,guidanceandACOPs,andcurrentHSEpublicationsarelistedinthelatestversionofreferences3and84respectively.
* AvailablefromEuroChlor,seeaddressinAppendix4.** AvailablefromCIA,seeaddressinAppendix4.† AvailablefromCIAorchlorineproducers,seeaddressesinAppendix4.†† AvailablefromThePublicEnquiryUnit,HMTreasury,ParliamentStreet, LondonSW1P3AGTel:01712704558
FordetailsonhowtoobtainHSEpricedandfreepublications,seeinsidebackcover.
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List of acronyms and abbreviationsACOP ApprovedCodeofPracticeALARP AsLowAsReasonablyPracticableANSI AmericanNationalStandardsInstituteAPF AssignedProtectionFactorASME AmericanSocietyofMechanicalEngineeringBA BreathingApparatusBS BritishStandardCABA CompressedAirlineBreathingApparatusCAF CompressedAsbestosFibreCEC CommissionoftheEuropeanCommunitiesCIA ChemicalIndustriesAssociationCIMAH ControlofIndustrialMajorAccidentHazards(Regulations)COMAH ControlofMajorAccidentHazards(Regulations)COSHH ControlofSubstancesHazardoustoHealth(Regulations)DTL DangerousToxicLoadEA EnvironmentAgencyEEC EuropeanEconomicCommunityEU EuropeanUnionHAZOP HazardandOperabilityHMSO HerMajesty’sStationeryOfficeHSA HazardousSubstancesAuthorityHSE HealthandSafetyExecutiveHSR HealthandSafetyRegulations(Booklet)HSW HealthandSafetyatWorkISO InternationalStandardsOrganisationLOLER LiftingOperationsandLiftingEquipmentRegulationsLPA LocalPlanningAuthorityMHO ManualHandlingOperations(Regulations)MHSW ManagementofHealthandSafetyatWork(Regulations)NIHHS NotificationofInstallationsHandlingHazardousSubstances (Regulations)OEL OccupationalExposureLimitOES OccupationalExposureStandardOJ OfficialJournal(oftheEuropeanCommunities)PPE PersonalProtectiveEquipmentppm Partspermillion(byvolume)PSTGC PressureSystemsandTransportableGasContainers(Regulations)PTFE PolytetrafluoroethylenePUWER ProvisionandUseofWorkEquipmentRegulationsRIDDOR ReportingofInjuries,DiseasesandDangerousOccurrence (Regulations)RPE RespiratoryProtectiveEquipmentSCBA SelfContainedBreathingApparatusSEPA ScottishEnvironmentalProtectionAgencySI StatutoryInstrumentSOED ScottishOffice,EnvironmentDepartmentSTEL Short-TermExposureLimitTGC TransportableGasContainerTSO TheStationeryOfficeUK UnitedKingdomUPVC UnplasticisedPolyvinylChlorideWSE WrittenSchemeofExaminatio
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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