Interpretation and Use of Flashpoint Information Cs24

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Health and Safety

Executive

The interpretation and use of

flashpoint informationGuidanceNoteCS24

This is a free-to-download, web-friendly version of CS24

(First edition, published 1999). This version has been adapted for online use

from HSE’s current printed version.

You can buy the document at www.hsebooks.co.uk and most goodbookshops.

ISBN 978 0 7176 2418 8

Price £5.00

This guidance provides information on the problems associated with

the determination of flashpoint during the classification of substances.

It discusses the principles and pitfalls in the test methods used in the

classification.

The guidance is aimed at those directly responsible for the classification of

the flammability hazard, ie manufacturers and suppliers. It can also help theend-user of a substance to interpret the flammability information given by the

safety data sheet and the label on the packaging.

HSE Books


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© Crown copyright 1999

Firstpublished1999

ISBN9780717624188

Allrightsreserved.Nopartofthispublicationmaybereproduced,storedin

aretrievalsystem,ortransmittedinanyformorbyanymeans(electronic,

mechanical,photocopying,recordingorotherwise)withoutthepriorwritten

permissionofthecopyrightowner.

Applicationsforreproductionshouldbemadeinwritingto:

TheOfficeofPublicSectorInformation,InformationPolicyTeam,

Kew,Richmond,SurreyTW94DUore-mail:[email protected]

ThisguidanceisissuedbytheHealthandSafetyExecutive.Followingtheguidance

isnotcompulsoryandyouarefreetotakeotheraction.Butifyoudofollowtheguidanceyouwillnormallybedoingenoughtocomplywiththelaw.Healthand

safetyinspectorsseektosecurecompliancewiththelawandmayrefertothis

guidanceasillustratinggoodpractice.

Health and Safety

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ContentsIntroduction 4

Classificationofhazards 4

Flammabilityprinciples 5

Incidentsresultingfrominadequateflammabilitydata 8

Flashpointmeasurement 10

Theinterpretationofflashpoint 16

Importantpointstobearinmind 17

References 18

Furtherinformation 19

Health and Safety

Executive


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Health and Safety

Executive

Introduction1 Thisguidanceprovidesinformationontheproblemsassociatedwiththe

determinationofflashpointduringtheclassificationofsubstances.Itdiscussesthe

principlesandthepitfallspresentinthetestmethodsusedintheclassification.

2 Theimportantpointstobearinmind,whetheryouareauserorasupplierofa

substance,aresummarisedattheendoftheguidance.

3 Theguidancerecommendsaprocedureforcorrectlyclassifyingasubstance

inrelationtoitsflammability.Itisimportantthattheclassificationofthehazardis

correct,otherwisethelabel,safetydatasheetandpossiblythepackagingmay

beincorrectlyassigned.Thiscanhavepotentiallyseriousconsequencesfora

subsequentuserofthesubstance.RelativelylittleguidanceisgivenintheUN

Manual of tests and criteria.1

4 Theguidanceisaimedatthosedirectlyresponsiblefortheclassificationof

flammabilityhazard,iemanufacturersandsuppliers.Itcanalsohelptheend-userof

asubstancetointerprettheflammabilityinformationgivenbythesafetydatasheet

andthelabelonthepackaging.

5 Examplesofincidentscausedasaresultofincorrectflammabilityclassification

aregivenlaterintheguidancenote.

Classification of hazards6 Theclassificationofchemicalshelpstoidentifythehazards(ordangers)ofa

chemicalsubstanceorpreparation.Therearemanypiecesofhealthandsafety

legislationwhichrequiresuchclassification.Theseinclude:

(a) theChemicals(HazardInformationandPackagingforSupply)Regulations19942

(CHIP)ifyousupplydangerouschemicals;

(b) theCarriageofDangerousGoods(Classification,PackagingandLabelling)and

UseofTransportablePressureReceptaclesRegulations19963ifyoutransport

dangeroussubstances;

(c) theNotificationofNewSubstancesRegulations19934beforeyouplacenew

substancesonthemarket.Newsubstancesarethosewhicharenotlistedon

theEuropeanInventoryofExistingCommercialChemicalSubstances(EINECS).

7 Otherregulationsalsorelyuponthecorrectclassificationofsubstancesand

preparations,forexampletheHighlyFlammableLiquidsandLiquefiedPetroleum

GasesRegulations19725andtheControlofMajorAccidentHazardsRegulations

1999.6

8 Inmanycases,thereareguideswhichdetailthemethodsforclassifying

substancesorpreparations,forexamplethe Approved requirements and test

methods for the classification and packaging of dangerous goods for carriage7

andthe Approved guide to the classification and labelling of substances and

preparations dangerous for supply.8Thetestmethodscontainedinthese

documentsaretakenfromeithertheUnitedNations Recommendations on the

transport of dangerous goods: Manual of tests and criteria Secondrevisededition(UNPublicationST/SG/AC.10/11/Rev2,1995) 1orAnnexVoftheDangerous

SubstancesDirective(67/548/EEC) 9whichhasbeendirectlyadoptedinthe

UKasanApprovedCodeofPractice.



Health and Safety

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Flammability principles9 Firstly,itisimportanttounderstandthebasicprinciplesrelatingtoflammability.

Flammabilityisthetermusedtodescribetheabilityofasubstancetoburnor

combustwithaflame.Combustionisusuallyarapidchemicalprocess,described

asanoxidationreactionbetweenafuelandanoxidantwhichisaccompaniedby

theevolutionoflightandheat.Forcombustiontotakeplace,bothfueland

oxidantneedtobepresentwithanignitionsourceofsufficientenergytoinitiatethe

reaction.Thewell-known‘firetriangle’providesausefulmeansofillustratingthis

requirement,ieallthreecomponentsmustbepresentforcombustiontooccur.

Removinganyoneofthesecomponentsresultsinano-firecondition.

10 Commonexamplesofthethreecomponentsofthefiretrianglearewood,air

andamatch(asinadomesticfire),andpetrol,airandaspark(asinacarengine).

Althoughintheseexamplesthefuelelementiseitherasolidorliquid,the

combustionreactionbetweenthefuelandtheoxidant,withafewexceptions,takesplaceinthevapourphase.Sotostartthereaction,ieforignitiontooccur,enough

energymustbesuppliedbothtovaporisethefuelandtoinitiatethereaction.For

burningtocontinue,thecombustionreactionmustproducesufficientheatto

propagatethereactionand,inthecaseofsolidorliquidfuels,tomaintainthe

vaporisationprocess.

11 Theamountofheatproduceddependsonthenatureofboththefuelandthe

oxidant,andalsoontherespectiveconcentrationsintheburningmixture.The

mixtureoffuelvapourandoxidantiscalledaflammableatmosphereandmaybe

definedasonethroughwhichaflamewillbepropagated,awayfromtheinfluence

oftheignitionsource.

12 Theoxidantisoftentheoxygenpresentinair.Howeverotheroxidantscan

constitutetheoxidantelementofthefiretriangle,andsoallowthecombustion

reactiontooccur.Theseincludethegaseschlorineandnitrousoxide,andeven

solidssuchasammoniumnitrate.

13 Inunconfinedsituations,combustionofaflammablemixturegenerallyresults

inafire.Underconfinedconditions,theheatfromthecombustionreactionand

alsotheproductionofgaseousreactionproductscancausesignificantincreases

inpressure.Thiscanoccurinamatterofmillisecondsandleadultimatelyto

anexplosion.Theseverityoftheexplosionisinfluencedbyanumberoffactors

includingtheinitialpressure,themixturecomposition,thedegreeofconfinement,

andthedegreeofcongestion.

14 Theflammabilityofasubstanceisthereforecharacterisedby:

(a)theconditionsunderwhichthesubstancecanbeignitedandthoseunder

whichitcontinuestoburn-knownrespectivelyastheflashpointandfirepoint;

(b)theconcentrationrangeoverwhichthevapour/oxidantmixtureisflammable,

ietheupperandlowerflammabilitylimits.Theselimitsvarydependingonthe

oxidant,andpressure;and

(c) theminimumoxygenconcentrationrequiredforthecombustionreaction.

Flammability limits

15 Ithasbeenfoundexperimentallythatmixturesofflammablegasesandvapours

inairareonlyignitableoverarestrictedrangeofconcentrations,thelimitsofwhich

aretermedthelowerandupperflammabilitylimits(orlowerandupperexplosive

limits).Theselimitsarenormallyquotedintermsofthevolumepercentageof



Health and Safety

Executive

flammablevapourinair,forexamplethelowerandupperflammabilitylimitsof

tolueneareapproximately1.3%and7%respectively.Iftheconcentrationof

toluenevapourinairislessthanabout1.3%thencombustionwillnotoccur;the

mixtureofflammablevapourinairissaidtobe too leantoburn.Conversely,ifthe

concentrationoftoluenevapourinairisgreaterthanabout7%thencombustion

againwillnotoccur;themixtureissaidtobe too richtoburn.

16 Theselimitshavenotbeensatisfactorilyexplainedtheoretically,andtheir

measurementhasbeenfoundtobeveryapparatusdependent.Awiderangeof

factorsinfluencethelimitsofflammabilityorexplosibility,forexample:

(a) actualtestconditions(notablythevesseldimensions,energyoftheignition

sourceandthedirectionofflamepropagation);

(b) temperatureandpressure;and

(c) oxidantconcentration.

Inaddition,differentcriteriamaybeusedtodeterminewhetherornotignitionhasoccurred.Forexample,aGerman(BAM)testusesapressureriseratherthanthe

flamedisengagingfromtheignitionsourceasthecriterionforignition.This

generallyresultsinawiderflammablerangethanothermethods.

17 Flammabilitylimitsarenotveryconvenientworkingtoolsasitisdifficultto

interpretvolumeconcentrationsinair.Itisoftenmorehelpfultoknowthe

conditionsunderwhichflammablemixturesofvapoursandgasesinairwillbe

formed,andtheparametermostusedinthiscontextisflashpoint.

Flashpoint

18 Theflashpointofaliquidisanimportantandpracticalflammabilitycharacteristic,

andisoneofthemainpropertiesusedtodeterminefireandexplosionhazard.

Theflashpointisdefinedas: the lowest temperature, corrected to a pressure of

101.325 kPa, at which a liquid evolves vapours, under the conditions defined in the

test method, in such an amount that a flammable vapour/air mixture is produced in

the test vessel.Youshouldnotethatattheflashpoint,continuouscombustiondoes

notoccur;thistakesplaceatahighertemperaturecommonlyreferredtoasthe

fire point .

19 Obviouslyflashpointislinkedtotheflammabilityorexplosibilitylimitsand

thereforethefactorsmentionedearlierwillhaveanaffectonitsvalue.Inaddition,

otherrelevantparametersare:

(a)testequipmentdesign;

(b) sizeofsample;

(c) ignitionsourceanddistancefromtheliquidsurface;

(d) ambientpressure;

(e) viscosityofthematerial;and

(f) operatorinterpretation(forsomematerialsitcanbedifficulttodeterminewhen

apropagatingflameoccurs).

20 Thehazardbeingdeterminedistheabilityofasubstanceorpreparationto

evolveaflammablevapour/airmixturewheretheintroductionorpresenceofan

ignitionsourcewouldcauseaflash.Themethodofidentifyingthishazardisto

performaflashpointtestusingoneoftheapprovedmethods.

21 Followingtheinitialignition,combustionmaybesustained.Acombustibilitytest,

usinganapprovedmethod,canconfirmwhetherthecombustionissustained.This

testmustbecarriedoutifthedeterminedflashpointlieswithincertaincritical

ranges.



Health and Safety

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22 Therecanbeproblemsindeterminingtheflashpointofmulticomponentblends

andmixtures(egminorproportionsofanorganicflammablesolventpresentina

mixture),emulsions,somehalogenatedsolvents,viscousliquidsandproductsthat

formaskin.

23 Theflashpointcanberegardedasalowertemperaturelimitofflammability.

Thiscanthenhelptoobtainthetemperaturerangeoverwhichaclosedvesselcan

containaflammableatmosphereinthepresenceofexcessliquid.

24 Ifaliquidisbelowitsflashpointtemperature,aflammableatmospherewill

notbeformed.However,ifthereisafine-dropletmistoraerosolofaflammable

substance,thismayproduceaflammableatmosphere.Fine-dropletmistsor

aerosolsareknowntobeflammableattemperaturesatleast100°Cbelowthe

flashpoint.Suchmistsmayformduetomechanicalmeansorduringcooling.

Similarly,foamsmaybeflammablebelowtheflashpointtemperature.

25 Factorsaffectingtheflashpointincludeatmosphericpressureandthecompositionoftheliquid.Astheatmosphericpressuredecreases,theflashpointdecreasesand

viceversa.Thiscanbeillustratedbyconsideringtheflashpointoftolueneas

measuredintheUKatsealevelandatDenverinthemountainsofColorado.

UK Atmosphericpressure Flashpoint

(sealevel) 101.3kPa 4.5°C

Denver Atmosphericpressure Flashpoint

(1685metres) 83.3kPa 1.0°C

26 Flashpointmeasurementscanbecorrectedforatmosphericpressurebyusing

thefollowingempiricalequation:

∆FPt =0.25(101.3-P )

where ∆FPt isthedifferenceinflashpointbetweenthatmeasuredatapressureP

(inkPa)andthatatapressureof101.3kPa.

27 Flashpointvaluesquotedintheliterature,ingeneral,areforpuresubstances.

Thepresenceofcontaminantscanhaveasignificanteffectontheflashpoint,

particularlyifthecontaminantisrelativelymorevolatile.Forexample,pureethylene

glycolhasaflashpointof111°C.However,theflashpointisreducedto29°Cwhen

acetaldehydeatalevelofonly2%ispresent.

28 Addingwatertoasolventcanraisetheflashpoint,providedthesolventismisciblewithwater.Ifsufficientwaterisadded,theaqueousliquorcanberendered

non-flammable.ThisisillustratedinTable1.

Table 1Variationofflashpointwithpercentageethanolinwater

% ethanol in water Flashpoint (°C)

100

90

75

50

25

105

13.0

14.5

20.5

23.5

31.5

47.561.5

Forsolventswhichareimmiscibleinwater,theflashpointwillbelargelyunaffected

bytheadditionofwater.

!



Health and Safety

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Incidents resulting from

inadequate flammability data29 Thesefourincidentshighlightthewidediscrepanciesthatmayresultinthe

measurementofflashpoint,dependingonthemethodchosen.Inparticular,there

arethesubstancesthatareviscous,andthemixturesthatcontainonlyarelatively

minorcomponentofavolatile,flammablesolvent.Boththeserequirecarewhen

choosingthemostappropriatetestapparatusandmethod.Inthesecircumstances,

themeasuredflashpointscanvarysubstantiallywiththetestmethod.Threeofthe

incidentsalsodemonstratetheseriousconsequencesthatcanarisewhenincorrect

flashpointtestdataisprovided,andwhentoomuchrelianceisplacedonthat

informationwithoutfurtherconsideringthecompositionoftheproducts.

Incident 1

Ahalf-full205-litremetaldrumcontainedaproprietarypre-polymerblendused

inthemanufactureoffoams.Itwasopenedandstirredwithaflatdiscstirrer

attachedtoastandardelectricdrill.Duringthisprocess,flammablevapours

releasedfromtheblendbuiltupinthedrumandwereignitedbyasparkfromthe

stirrermotor.Theresultingfireballeruptedfromthedrum,engulfingtheheadand

shouldersofanemployee.

Thepre-polymerformulationconsistedofaviscousmixtureofpolymers,

surfactants,catalystsandapentaneblowingagent.Thereplacementofnon-

flammableCFC-typeblowingagentsbyflammablealternativesisbecomingincreasinglywidespread,primarilybecauseoftherestrictionsimposedby

environmentallegislation.

Thesafetydatasheetforthepre-polymerblendstatedthattheflashpointwas

38°C;thetestmethodusedwasnotquoted.Italsostatedthatthematerialdid

notsupportcombustion.

Theresultsofindependentflashpointtestscarriedoutwithdifferenttest

apparatusgavethefollowingresults:

Test method Flashpoint (°C)

ISO2719:1988 27.4ISO3679:1983 17.0

ISO1523:1983 <10.0

Thematerialprovednottosupportcombustionwhentestedinaccordancewith

Schedule2oftheHighlyFlammableLiquidsandLiquefiedPetroleumGases

Regulations1972.

Thisillustratesthewidespreadofflashpointtemperaturesforagivensample.In

termsofCHIP,twoofthetestswouldresultinthematerialbeingclassifiedas

highlyflammable;whiletheothertestprocedurewouldresultinitbeingclassified

asnon-hazardousintermsofflammability.Theresultsofthecombustibilitytest

canexemptmaterialfrombeingclassifiedas‘flammable’,iftheflashpointisbetween21°Cand55°C.



Health and Safety

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Incident 2

Acompanymanufacturespolyurethaneprecursorstovariousspecifications.

Duetoreformulationwithaflammableblowingagent,thecompanyundertook

aflashpointdeterminationaspartoftheclassificationexercise.Thecompany

normallyusedtestISO3679butbecausethedataforacompetitor’ssamplehad

beentakenfromatestusingISO1523,theydecidedtosubjectallthesamples

tobothtests.Allsamplesweretakenfromalarge-scaleevaluationandwere

replicated.Allreplicatesgavegoodagreementbythesametestmethod,andthe

testswerecarriedoutonthesameday.Theresultswereasfollows:

Sample Flashpoint (°C)

ISO3679 ISO1523

A 27 3

B 15 1.5

C 7.5 -8.5

BothISO3679andISO1523aretestmethodscontainedinAnnexVofthe

DangerousSubstancesDirectiveasequilibriummethodssuitablefordetermining

theflashpointofviscousliquids.

Incident 3

Amanwaskilledwhenastoragetankexplodedduringweldingworknearby.The

tankcontainedawasteproductfromanothercompanywhichthiscompanythen

treatedtoproduceagriculturalchemicals.Thewasteproductwasessentiallyan

aqueousmixtureofaceticandphosphoricacids.Howeveritwastheproductofasolventextractionprocesswithtoluene.Althoughessentiallyaqueoustherewere

smallamountsoftoluenepresentinthemixturewhichallowedflammablevapours

tobuildupintheheadspaceofthetank.Theparentcompanyhadquoteda

flashpointonthesafetydatasheetas91°C.Furthertestsoftheflashpointwere

undertakenduringtheinvestigation.Theresultswereasfollows:

Test method Flashpoint (°C)

ISO3679 55-65

ISO1523 28-33

Incident 4

Anexplosionoccurredinaheatedproductstoragetankcontainingrecycled

motoroil,seriouslyinjuringanemployee.Testsduringtheinvestigationshowed

thatwastemotoroilnormallycontainsapproximately0.5%w/wofpetrol.This

resultsinasignificantloweringofthemeasuredflashpoint.Acomparison

betweentheflashpointsofoilcontaminatedwithpetrolmeasuredbyequilibrium

andrapidequilibriummethodsisshownhere:

Nominal petrol addition Flashpoint (°C)

to unused oil (%w/w) ISO 3679 ISO 1523

0 >>110 >>110 0.5 92 68

1.0 65.5 49

1.5 47.5 32



Health and Safety

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Flashpoint measurement30 Flashpointscanbemeasuredintwomodes,equilibriumornon-equilibrium,and

inessentiallytwotypesofapparatus,closedcupandopencupapparatus.The

mostextensivelyusedapparatusare:theAbelclosedcup;thePensky-Martens

closedcup;theTagopenandclosedcups;theSetaflashapparatus;andthe

Clevelandopencup.

31 Closedcupmeasurementscanbeequilibriumornon-equilibriummethods,

whereastheopencupmeasurementsarenon-equilibriummethods.

32 Closedcupflashpointsarenormallyseveraldegreeslowerthanthosedetermined

byopencupmethods,thedifferencebeingmoremarkedwhenaclosedcup

equilibriumprocedureisused.Thisisbecausetheyaredeterminedonasaturated

vapour/airmixture,whereasintheopencuptest,thevapourhasfreeaccesstothe

air.Consequently,withtheopencuptest,thevapourisslightlylessconcentratedatagiventemperatureduetovapourlossestothesurroundingatmosphere.

33 Theclosedcupflashpointtestroughlyapproximatestoasituationwherethe

topclosureofadrumcontainingaliquidsubstanceisopened,andalightisused

toseeifthedrumisfullorempty.Whenthelightisofatypethatcanignitethe

vapoursinthedrum,anexplosionislikelyifthetemperatureisatorslightlyabove

theclosedcupflashpointoftheliquidsubstance.

34 Likewise,theopencupflashpointconditioniscomparedtothepotentialignition

ofvapoursaboveapoolofspiltliquidsubstanceonthefloorintheabsenceof

draughts.Table2showsthecomparativeflashpointsmeasuredinopenandclosed

cupapparatusforpureliquids.

Table 2Comparisonofflashpointsmeasuredinopenandclosedcupapparatus

Material Flashpoint (oC)

Closed cup Open cup

Aceticacid

Acetone

n-butanol

Methanol

Toluene

40

-17

29

10

4

43

-9

44

16

7

35 Theabilityofaliquidtoproduceaflammablevapour/airmixturewithinpreciselydefinedconditions,whichwillcauseaflashatacertaintemperature,isanintrinsic

propertyoftheliquid.Theflashpointtestmethodswhichidentifythispropertydo

notmeasureflashpointsundersuchpreciselydefinedcondition.Theyhavediffering

constantsineachtestmethodwhicheffectivelyreflectdifferingconditionsofuse.

36 Flashpointmeasurementisanempiricalapproach,andthereforeitisimportant

whenquotingflashpointstodefinethemeasurementtechnique.Becauseitisan

empiricalmeasurement,youcannotcomparevaluesofflashpointobtainedfrom

differentmethods.Howevergoodagreementshouldexistifcomparingequilibrium

methodstogether,ornon-equilibriummethodstogether,particularlywithpure

(singlecomponent)liquids.

37 Themajordifferencebetweenequilibriumandnon-equilibriummethodsisnot

merelythattheapparatusforequilibriummethodshasacoveroverthesample

vessel,socontainingthevapoursproduced.Itisalsothedifferentwayinwhichthe

temperatureoftheliquidisattained.



Health and Safety

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38 Essentiallyinnon-equilibriummethods,thetemperatureisincreasedslowlyover

agivenrangewiththesourceofignitionbeingpresentedtothevapouratintervals

untiltheflashisobserved.Inequilibriummethods,thetemperatureissteppedtoa

givenvalueorincreasedataveryslowrate,andthevesselallowedtoequilibrate

forafixedperiodoftimebeforethesourceofignitionisintroduced.

39 Thetestisthereforeat‘equilibrium’becausethistimeintervalallowsthe

temperatureofthevapourtobethesameasthatoftheliquid,soachievingan

almoststeadystate.Inactualfact,trueequilibriumisnotachievedbecauseinall

acceptedtestmethods,thelidofthevesselisnotheated.Consequentlythereisa

temperaturegradientinthevapourspaceoftheapparatus.Sincethemeasurement

offlashpointisempirical,thiseffectmatterslittleinpracticeandthematerialis

deemedtobeatequilibrium.

40 Howeverintestapparatuswhichoperateswithalargecupandafluidwhich

containsonlyasmallproportionofalowflashpointmaterialthentheequilibrium

effect,coupledtotherateofreleaseofthevolatilecomponents,maybeappreciable.

What do the Regulations require?

41 Asdiscussedearlier,theRegulationsstatethatsubstancesandpreparations

shouldbeclassifiedsoastodeterminetheirhazard.Theapplicabletestmethods

forthemeasurementofflashpointarestatedintherelevantguides,andinthe

approvedcodesfortransportandsupply(seeparagraph8).

42 Theprincipleforalltheflashpointtestmethodsis,(normally)aftersuitably

coolingorwarmingthetestmaterialtoafewdegreesbelowthetesttemperature,

toplacetheliquidinatestvessel.Thesubstanceisthenheatedtothetesttemperatureaccordingtotheproceduredescribedintheindividualtestmethod

containedinthevariousstandards.Ignitiontrialsarethencarriedoutinorderto

ascertainwhetherornotthesampleflashesatthetesttemperature.

43 ThemethodsquotedintheRegulationsrecognisethetwomodesoftest,and

stateapplicabletestmethodsforeachmode.Thesetestmethodsareasfollows:

Equilibrium test methods

ISO1516:1981 Paints,varnishes,petroleumandrelatedproducts-

flash/noflashtestclosedcupequilibriummethod

ISO3680:1983 Paints,varnishes,petroleumandrelatedproducts- flash/noflashtestrapidequilibriummethod


determinationofflashpoint-closedcupequilibrium

method


determinationofflashpoint-rapidequilibriummethod

Non-equilibrium test methods

44 Manyofthestandardslistedherehaveequivalentnationalstandardswhich

obviouslycanbeusedinsteadofthosequoted:

BS2000:Part170 FlashpointbytheAbelapparatus(non-statutorymethod)

EN57 Determinationofflashpoint-Abel-Penskyclosedtester



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ASTMD56 Tagapparatus

ISO2719:1988 Determinationofflashpoint-Pensky-Martensclosedcup

method

45 Onlycertaintestmethodsareapplicablefordeterminingtheflashpointof

viscousfluids.TheseareISO3679,ISO3680,andISO1523.

46 Thevariouspiecesoflegislationhavedifferentclassificationcategoriesand

differenttransitiontemperatures,andthesearediscussedinthefollowingparagraphs.

Classification of flammability for supply

47 UndertheCHIPregulations,2substancesareessentiallyclassifiedfor

flammabilityintothreecategoriesofdangeraccordingtotheirflashpoints:

(a) extremelyflammable- thoseliquidswithaflashpointlowerthan0°C

andaboilingpoint(orinitialboilingpoint)lower thanorequalto35°C;

(b) highlyflammable - l iquidswhichhaveaflashpointbelow21°Cbut

arenotextremelyflammable;

(c) flammable - liquidswhichhaveaflashpointequaltoorgreater

than21°Candlessthanorequalto55°Cand

whichsupportcombustionwhentestedinthe

prescribedmanner(giveninSchedule2ofthe

HighlyFlammableLiquidsandLiquefied

FlammableGasesRegulations19725)at55°C.

48 Thetransitiontemperaturesbetweenthevariouscategoriesofdangerare

thereforecritical,andtherearespecificmethodsformeasuringtheflashpoint.When

aflashpointisdeterminedbyanon-equilibriummethodandthevalueisfoundto

be0±2°C,21±2°Cor55±2°C,theflashpointshouldbeconfirmedbyusingan

equilibriummethod.

49 Inpractice,foraliquidwhichpossessesaflashpoint,thelimitingcriteriafor

classificationasextremelyflammablewillnormallybedeterminedbytheboiling

pointcriterion.Sotherelationshipbetweenflashpointandboilingpointissuchthat:

foraliquidwithaflashpointandwithaboilingpoint(orinitialboilingpoint)below

35°C,itsflashpointwillbelowerthan0°C.

Classification of flammability for transport 50 UndertheCarriageofDangerousGoods(Classification,Packagingand

Labelling)andUseofTransportablePressureReceptaclesRegulations1996, 3

liquidsareessentiallyconsideredasflammableif:

theflashpointis61°Corlessand,whentheirflashpointisabove35°C,

theysupportcombustionwhentestedintheprescribedmannerat60.5°C

or75°C.

TheprescribedmannerisgiveninAppendixBofthe Approved requirements

and test methods for the classification and packaging of dangerous goods for

carriage.7Asubstancewithaflashpointabove61°C,butactuallytransportedata

temperatureatoraboveitsflashpoint,isalsoconsideredaflammableliquid.

51 Thethresholdsforthecategoriesofflammabilityhazardare:



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I (highhazard) - those liquidswithaboiling point (orinitial boiling

point)lowerthanorequalto35°Canda

flashpointnotexceeding61°C;

II (mediumhazard) - thoseliquidswithaboilingpoint(or initialboiling

point)above35°Candaflashpointof23°Cor

lessunlesstheymeetthecriteriaofIII(c)below;

and

III (lowhazard) - (a) thoseliquidswithaninitialboilingpoint

above35°Candaflashpointof23°Cor

abovebutnotexceeding61°C;or

(b) liquidswithaninitialboilingpointabove

35°Candaflashpointabove61°C

carriedorofferedforcarriageata

temperatureabovetheirflashpoint;or

(c) viscousliquidswithaflashpointof23°C

orbelowunlessexcludedbecausethey

meetcertainsolventseparation,

compositionandviscosityrequirements

specifiedintheregulations.

52 Asinthecaseofsupply,thetransitiontemperaturesbetweenthevarious

categoriesofdangerarecritical,andatthesetemperaturestherearespecific

methodsforthemeasurementofflashpoint.Whenaflashpointisdeterminedby

anon-equilibriummethodandthevalueisfoundtobe23±2°Cor61±2°C,or

thesubstanceisviscous,theflashpointshouldbeconfirmedbytheuseofanequilibriummethod.

Classification of flammability in the Highly Flammable Liquids and

Liquefied Petroleum Gases Regulations 1972 5

53 TheHighlyFlammableLiquidsandLiquefiedPetroleumGasesRegulations

1972,5asamendedbyCHIP, 2definehighlyflammableliquidsasanyliquid,liquid

solution,emulsionorsuspension:

(a) withaflashpointlessthan32°Cmeasuredbyanyoneoftheapproved

methodsspecifiedinPartIIIofSchedule1totheCHIPRegulations;2and

(b) whichwhentestedinthemannerspecifiedinSchedule2totheHighly

FlammableLiquidsandLiquefiedPetroleumGasesRegulations19725

(ieat50°C)supportscombustion.

Ammonia,liquefiedflammablegasandliquefiedpetroleumgasareexcludedfrom

thisdefinition.

54 Aswithsupplyandtransport,anequilibriummethodisrequiredonlyifthe

flashpointisdeterminedbyanon-equilibriummethodandlieswithin2°Cofthe

criticaltemperature,iewithintherange30-34°C.

How do the equilibrium methods differ?

ISO 1523

55 Thistestmethodisusedtodeterminetheactualtemperatureoftheliquidwhen

ignitionofthevapoursfirstoccurs,iebydefinitiontheflashpointofamaterial.The

standardcanbeappliedtoassessingtheflashpointofapaint,varnish,paintbinder,



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solvent,petroleumorarelatedproduct.Itissuitableforviscousliquidsbutthere

arenolimitssetfortheviscosityquotedinthestandard.Themethodissuitablefor

testingoverthetemperaturerange5to110°C.Anyofthefollowingtestapparatus

canbeused:

(a) Abel;

(b) Abel-Pensky;

(c) Pensky-Martens;

(d) Tag.

56 Alltheaboveapparatusaresimilarinthatthevolumeofthecupisrelatively

large(approximately50cm 3)andfittedwithaclose-fittinglid.Thetestportionis

heatedintheclosedcupbyimmersioninasuitablebath.Thetemperatureofthe

bathisslowlyraisedatsucharatethatthedifferenceintemperaturebetween

theliquidinthebathandthetestportioninthecupneverexceeds2°C.This

heatingprocedureensuresthatthetemperatureofthetestportiondoesnotrise

morequicklythanabout0.5°Cin1.5minutes.Duringtheheatingupperiod,ignitiontrialsarecarriedoutatintervalsofnotlessthan1.5minutes.Thelowest

temperatureatwhichaflashoccursisrecorded.Thetestisrepeatedusingafresh

testportion.Theflashpointsarecorrectedtostandardatmosphericpressure.

ISO 3679

57 Theapparatusspecifiedinthisstandardallowsdeterminationoftheflashpoint

byamorerapidmethodandwithasmallertestportion(approximately2cm 3)than

themethodinISO1523.Thestandardcanbeappliedtoassessingtheflashpoint

ofapaint,varnish,paintbinder,solvent,petroleumorarelatedproduct.Itis

suitableforviscousliquidsbuttherearenolimitssetfortheviscosityquotedinthe

standard.Themethodissuitableforusewhentheflashpointisbelow110°C.

58 Theapparatusisheatedtoatemperature3°Cbelowtheexpectedflashpoint.

Thetestportionisthenaddedtotheapparatus,andallowedtoequilibratefor

60secondsbeforecarryingoutanignitiontrial.Ifnoflashisobserved,thetestis

repeatedattemperaturesin5°Chigherintervalswithfreshtestportions,untila

flashisobserved.Ifaflashisobservedattheinitialtesttemperature,thetestis

repeatedattemperaturesin5°Clowerintervalswithfreshtestportions,untilno

flashisobserved.Havingestablishedaflashbetweenthetwotemperatures5°C

apart,thetestisrepeatedagainwithfreshtestportionsat1°Cintervalsabove

thelowerofthetwotemperaturesuntilaflashisobserved.Theflashpointsare

correctedtostandardatmosphericpressure.

ISO 3680

59 ThisstandardusestheapparatususedinISO3679andisapplicableforthe

sametypesofmaterialsandoverthesametemperaturerange.Thedifference

isthatitdoesnotdeterminetheactualflashpointofaliquid,butdetermines

whethertheliquidflashesataspecifictemperature.Itisaso-called‘flash-no

flash’method.Itcanbeusedthereforetodeterminethebehaviourofaliquidata

selectedequilibriumtemperature,asrequiredundertheregulationsrelatingtothe

storage,transportorsupplyofflammableproducts.

60 Theliquidisheatedtothespecifictemperature,andallowedtoequilibrateforat

least60secondsbeforetheignitiontrialiscarriedout.

ISO 1516

61 Thisisthe‘flash-noflash’testequivalenttoISO1523.Thedifferenceisthat

theliquidisallowedtoequilibrateatthespecifictesttemperaturefor10minutes



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beforetheignitiontrial.Alsoifnoflashoccurs,thetestsampleismaintainedatthis

temperatureforafurther10minutesandtheignitiontrialrepeated.



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The interpretation of flashpoint62 Experiencehasshownthatevenforpuresinglecomponentmaterials,there

arediscrepanciesbetweenthevarioustypesofequipment.Table3illustratesthe

averagecomparativerangeforarangeofdifferenttestapparatus.Asurveyofa

numberofcomparisonprogrammesshowsthattheAbelclosedcupdesignoften

givesthelowestresults.

Table 3Comparisonofflashpointtemperaturerangesbetweendifferenttestapparatus

Test apparatus Open/closed Average comparative range

Abel Closed -

Setaash Closed about0-6.9oChigher

Tag Closed about0.5-5oChigher

Pensky-Martens Closed about1.7oClowerto6oChigher

Abel-Pensky Closed about0.2oClowerto1.4oChigher

Luchaire-Finances Semi-open about5.1-15.6oChigher

Tag Open about6.4-16.1oChigher

Cleveland Open about11.7-26.1oChigher

63 Thevariationswillbemoremarkedwhenproceduralchangesareintroduced

(ieequilibrium,rapidequilibriumandnon-equilibrium).Ingeneralthevalueofthe

determinedflashpointincreasesintheorder:

equilibrium<rapidequilibrium<non-equilibrium

64 Equilibriumflashpointprocedurestendtobetimeconsuming,anditisoften

moreexpedientandconvenienttouseasmall-volumetestapparatuswiththe

associatedrapidequilibriumtestprocedure.Formanymaterials,andcertainlyfor

purecompounds,thisisperfectlyadequate.However,astheincidentsdescribed

inthisguidancenoteshow,forcertainmixturesanequilibriumprocedureisa

bettermeansofassessingtheflammabilityhazard.Thisisparticularlysoforthose

mixturescontainingrelativelylowlevelsoflowflashpointmaterials,whichmaybe

leftforrelativelylongperiodsinaclosedsystem.



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Important points to bear in mind Theguidancehasillustratedthedifficultiesthatcanarisewiththemeasurement

andinterpretationofflashpoint.Thefollowingchecklistsummarisestheimportant

pointstakenfromtheguidance.Theseneedtobeunderstoodinorderto

correctlyapplyflashpointinformation.

If you are a user of the substance

1 Remember,flashpoint isanempirical measurement ofasubstance.

2 Theflashpointtemperaturegivesanindicationoftheflammabilityhazard,

butdoesnotpredictthelevelofsafetyunderspecificcircumstancesofuse.

Makesureyoureadthesafetydatasheetforadditionalinformation.

3 Flashpointvaluesarevariable,dependenton:

(a) modeoftest,ieequilibrium,rapidequilibriumornon-equilibrium;

(b) apparatustypeandcondition;

(c) operatorinterpretation;

(d) samplingprocedure,particularlyformixtures,halogenatedsolventsand

emulsions;

(e) sampleconditioning,iehowthesamplehasbeenhandledandstored

beforethetest;

(f) ambientpressure.

4 Forpuresinglecomponent,non-viscousliquids,thedeterminedflashpoint

shouldbecomparablebetweenalltheapprovedequilibriummethods.

If you are carrying out a flammability classification of a substance

5 Whengivingtheflashpointofasubstance,alwaysquotethetestmethod

used.

6 Formulticomponentmixtures,particularlythosecontainingaminor

proportionofavolatilelow-flashpointsolvent,choosethemostappropriate

methodafterconsiderationoftheapplicablestandards.Do not justuseany

ofthetestapparatusthatyoumayhavereadilyavailabletoyou.Theincidents

describedinthisdocumentsuggestthatforthistypeofsubstanceorpreparation,

trueequilibriumtestmethodsusingapparatusthatcontainsarelativelylarge

volumeofliquidareappropriate,ieISO1523andISO1516.

7 Rememberthereisadutyunderthevariousregulationstoclassifyand

labelyourproductscorrectly.Ifaflashpointtestisgivingnon-reproducibleresults,

oriftwotestmethodsgiveconflictingresults,thenyourdutyistoresolvethese

uncertaintiessatisfactorily-nottoclassifyandlabelmaterialsonthebasisof

unsatisfactoryresults.

8 Iftherearesituationswheretheriskduringuseisgreaterthanthatsuggested

bytheclassificationorlabelling,thisinformationshouldbepresentinthesafety

datasheet.Forexample,therecouldbeasubstancewithaflashpointofbetween

21°Cand55°C,andthesubstanceisshownnottosupportcombustion,and

soitisnotclassifiedas‘flammable’underCHIP.2

Howevertheremaybeanincreasedriskofproducingaflammableatmospherebyvapourenrichmentor

accumulation.Thesafetydatasheetcouldwarnusersofthisdanger.Theuse

ofriskphraseR18onthesupplylabelandinthesafetydatasheetisapplicable.

Alternativelyyoucouldprovideinformationonanyflammablecomponents.



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References1 Recommendations on the transport of dangerous goods: manual of tests and

criteriaSecondrevisededition(ST/SG/AC.10/11/Rev.2)UnitedNations1995

ISBN9211390494

2 Chemicals (Hazard Information and Packaging for Supply) Regulations 1994

SI1994/3247HMSO1994ISBN0110438779asamendedbythe Chemicals

(Hazard Information and Packaging for Supply) (Amendment) Regulations 1996

SI1996/1092HMSO1996ISBN0110545702,theChemicals (Hazard Information

and Packaging for Supply) (Amendment) Regulations 1997 SI1997/1460Stationery

Office1997ISBN011063750X,the Chemicals (Hazard Information and

Packaging for Supply) (Amendment) Regulations 1998SI1998/3106Stationery

Office1998ISBN0110799313,andthe Chemicals (Hazard Information and

Packaging for Supply) (Amendment) Regulations 1999SI1999/197Stationery

Office1999ISBN0110804104

3 Carriage of Dangerous Goods (Classification, Packaging and Labelling) and

Use of Transportable Pressure Receptacles Regulations 1996SI1996/2092HMSO

1996ISBN011062923X

4 Notification of New Substances Regulations 1993SI1993/3050HMSO1993

ISBN011034278X

5 The Highly Flammable Liquids and Liquefied Petroleum Gases Regulations

1972SI1972/917HMSO1972ISBN0110209176

6 The Control of Major Accident Hazards Regulations 1999(duetocomeintoforceApril1999)

7 Approved requirements and test methods for the classification and packaging

of dangerous goods for carriage. Carriage of Dangerous Goods (Classification,

Packaging and Labelling) and Use of Transportable Receptacles Regulations 1996.

Approved requirementsL88HSEBooks1996ISBN071761221X

8 Approved guide to the classification and labelling of substances and

preparations dangerous for supply. CHIP97 L100HSEBooks1997

ISBN0717613666

9 Annex V of the Dangerous Substances Directive(67/548/EEC)whichhasbeen

directlyadoptedintheUKasanApprovedCodeofPractice.

Whileeveryefforthasbeenmadetoensuretheaccuracyofthereferenceslistedin

thispublication,theirfutureavailabilitycannotbeguaranteed.


http://slidepdf.com/reader/full/interpretation-and-use-of-flashpoint-information-cs24 19/19

Further informationForinformationabouthealthandsafetyringHSE’sInfolineTel:08453450055

Fax:08454089566Textphone:08454089577e-mail:[email protected]

writetoHSEInformationServices,CaerphillyBusinessPark,CaerphillyCF833GG.

HSEpricedandfreepublicationscanbeviewedonlineororderedfrom

www.hse.gov.ukorcontactHSEBooks,POBox1999,Sudbury,Suffolk

CO102WATel:01787881165Fax:01787313995.HSEpricedpublications

arealsoavailablefrombookshops.

TheStationeryOfficepublicationsareavailablefromTheStationeryOffice,

POBox29,NorwichNR31GNTel:08706005522Fax:08706005533

e-mail:[email protected]:www.tso.co.uk(Theyarealso

availablefrombookshops.)StatutoryInstrumentscanbeviewedfreeofcharge

atwww.opsi.gov.uk.

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Documents

Interpretation and Use of Flashpoint Information Cs24