Thermal Protective Performance (TPP) | Globe Turnout Gear

Thus, the NFPA minimum requirement of a TPP rating of 35 equates to 17 ½ seconds until second-degree burns occur in a flashover situation. A pie chart breaking ... FindaDistributorHome / ThermalProtectivePerformance(TPP)ThermalProtectivePerformance(TPP)Inthe1986revisionofNFPA1971,ProtectiveClothingforStructuralFireFighting,anewtestmethodformeasuringthermalprotectionwasintroducedandaminimumthermalprotectiveperformance(TPP)ratingwasestablished.Thissophisticatedtestmethodreplacedtherequirementforaminimumcompositethickness,anditspurposeistomeasuretherateatwhichconvectiveandradiantheatpenetratethroughthecompositesystem–outershell,thermalliner,andmoisturebarrier–tocausesecond-degreeburnstothehumanskin.TheTestThisillustrationisofastandardTPPtester.Thethreelayersthatmakeuptheturnoutensembleareplacedincompositeformbeneaththesensor,whichrecordsskintemperature.Theselayersareplacedontothemachineinthesameorderinwhichtheyarefoundintheprotectivesystem,withthethermallayernexttothesensor,themoisturebarrierinthemiddle,andtheoutershellnexttotheenergysource.Themovableshutterenablesthetechniciantocontrolthetimeandtheamountofexposure,duringwhichgasburnersprovideactualflame.Atthesametime,theheatedtubesprovideradiantheatandaflashoversituationcanbesimulated.Thepointatwhichheattransferthroughallthreelayersisenoughtocauseasecond-degreeburnisdeterminedgraphically,byusingarecorderchartofthesensorreadings.Duringtesting,therecordingcontinuouslytracestheaveragetemperatureriseonpaper,whichisdepictedasacurvedlinerepresentinghigherandhighertemperaturesasmoreheatpenetratesthroughthesamplematerialstothesensor.Asthetestisbeingrun,thetracingiscomparedwithasecondcurve,calledtheStoll'scurve,whichshowstheblisterpointofhumanskinasafunctionofheatandtime.ThepointofintersectionbetweenthesetwocurvesistheactualTPPrating.Forthepurposeofmeasuringactualtimetoburn,theTPPratingisdividedinhalftodeterminethenumberofsecondsuntilhumantissuereachesthesecond-degreeburnpoint.Thus,theNFPAminimumrequirementofaTPPratingof35equatesto17½secondsuntilsecond-degreeburnsoccurinaflashoversituation.TPPRatingsandComponentMaterialsItisimportanttorememberthattheTPPratingisdependentuponthecomponentmaterialsspecifiedandisnotanindependentfunction.Toillustratethispoint,imaginethatfabricsareactuallynumbersandthatyouorderanoutershellwitharatingof5,athermallinervaluedat3,andamoisturebarrierratedat2–andspecifythatthecombinationmusttotal12.Bytotalingthenumbers(i.e.,materials)youordered,wecanonlycomeupwitha10,nota12,regardlessofhowhardwetry!Toreachthe12,itwouldbenecessarytomakeachangetothematerialsspecified.VariationinTPPMeasurementsSincematerialsarenotnumbers,therewillalwaysbesomevariationinthemeasurements.Forexample,inanytextileindustrytherearetolerancesfortheweightsoffabrics;specifictotheNFPA1971standard,thereisnoweightrequirementforanyofthethreelayers.Instead,thestandardsetsminimumperformancerequirements,andaslongastheindividuallayersmeetalloftheperformancerequisites,weightisnotaconsideration.Wedowanttopointout,however,thatbecausematerialweightsdovary,itispossibleforthesamecombinationtoyielddifferentTPPratingsfromtesttotest.Forexample,ifthe7.5oz.PBI®shellfabricisrunningslightlyhigher(say7.8)andthe7.2oz.ARALITE®andthe4.0oz.GORE®RT7100arealsoontheheavierside(say7.4and4.3respectively),thenyourtotalTPPtestratingwillbehigheronthatparticularcompositetest.Forthisreason,wecautionourcustomerstotakealloftheNFPArequirementsintoconsiderationwhenmakingchoices,andtonothoneinonthisonevalue.Ingeneral,weactuallyprefertoprovidearange;however,thestandardonlydictatesaminimumratingof35andsothethird-partytestresultisreportedasanaverage,yieldingonlyonenumber.SincemanymanufacturershavetheirownTPPtestapparatus,andsincethesamecombinationscanyielddifferentresults,weencouragedepartmentstorequestthatanyvaluesprovidedcomefromspecificULcertificationresults.LearnmoreaboutVariabilityinTPPandTHLResultsTheTrade-offBetweenTPPandTHLApopularmisconceptionisthatif35isgood,aratingof40,50,oreven60mustbebetter.Itisimportanttoremember,however,thattheonlywaytoincreaseyourTPPratingistoaddmoreinsulation,usuallybyspecifyingheaviermaterialcomponents.Generallyspeaking,addedinsulationwillmeanincreasedweightofthetotalsystem,resultingingreaterheatstressforthefirefighterandlowertotalheatlossofthecomposite.Thequestionyoumustaskyourselfiswhethertheaddedsecondsofprotectionintheeventofaflashoverenvironmentisreallyagoodtrade-offagainsttoday'slighterweightsystemsandhigherTHLvalues.Itisalsoimportanttonotethatbyselectingthethreelayerstobeusedinyoursystem,youhaveautomaticallyspecifiedtheTPPrating,sinceitisafunctionofthematerialschosenandisnotaproductofgarmentdesignorconstruction.LearnmoreaboutTPPvsTHLTurnoutProtectionExampleGarmentdesignandfeaturesdominatethethermalandheatstressperformanceoftheclothingsystem.Morethan50%ofatypicalturnoutisreinforcedbyadditionalfabrics,trim,labels,oroverlap.BaseComposite:TPP=50.KEVLAR®/NOMEX®OuterShellPTFE/E-89®MoistureBarrieraramidbattThermalLiner.FindaDistributorFindADistributorAccessMSA'snetworkofGlobedistributors.StayInformedStayInformedSignuptogetthelatestindustryresources,productinformation,monthlynewsletter,andrelatedtopics.SignUpFOLLOWUS: