February 2018 The barrier cable gland: moldable sealant ......The barrier cable gland: moldable...

February2018

Thebarriercablegland:moldablesealant(two-componentfiller)vsauto-formingsealant(two-componentresin)

1. Preface:theselectionofthecableglandIntheplantconcept ithasalwaysbeenofprimary importancethephysicalseparationbetweensafeareaandclassifiedarea.Thisconceptwasapplied in theelectricenergy transportsystemsbymeansofcablesburiedinsandbedandthenderivedtotheuser(anelectricmotororajunctionboxoranenduser)withtheuseofaconduittubesuitableforthe insertionofelectricalcables(Freez-Moon)freefrominternalridgesand terminatedon theenduser throughaphysical separationmadewithexplosion-proof sealingdevice(forexampleasealingfitting).With the advent of the IEC/EN 61241-0 and IEC/EN 60079-0 standards, as well as the IEC/EN 60079-1standard,changedtheconceptofcableentryinelectricalandelectronicequipmentsuitableforareaswithdangerofexplosion,allowingtohavethecableentrywithappropriatesealingcablegland.Lately,theIEC60079-14:2013-1/EN60079-14:2014-03standards,whichdescribesthedesign,selectionandinstallationofelectricalsystemsinexplosiveatmospheres,introduced,intheparagraph10.6.2,theselectioncriterionofcableglandstobeusedforcableentry intoelectricalandelectronicequipmentsuitablefor installationinsuchatmospheres.Thismeansthatsubstantialchangeshaveoccurredovertime.Theeffectofregulatoryunification,bothinEuropeandinternationally,changedtheconceptsofclassificationfroma"Rigid"system,asystemthatprovideduniquedimensionalparameters,toa"Calculation"systemaccordingtothetypeofgas,theconcentration,theaerationcapacityoftheclassifiedareaandotherprocessparametersthathavebecomeaprerogativeoftheprocessengineer.Foragreaterclarityandtogiveaprecisedescriptionofthisconceptualvariation, inthegraphsbelowweshowthedifferencesbetween thepreviousversionof thestandard IEC60079-14:2007-12/EN60079-14:2008-10 and the version currently in force of the IEC 60079-14:2013-11/EN 60079-14:2014-03, fullyreportingwhatisdescribedinthesestandards.Inthepreviousversion,intheparagraph10.4.2,itisdescribedasfollows:Note:theversionsofthementionedstandardswithinthisdescriptionmustobviouslybethosealignedwiththedateofissueoftheserules."10.4.2Selectionofcableglands"Thecableentrysystemshallcomplywithoneofthefollowing:a) cable glands in compliance with IEC 60079-1 standard and certified as part of the equipment when

testedwithasampleoftheparticulartypeofcable;

b) whenacable,incompliancewith9.3.1(a)(from9.3.1a)"withasheathinthermoplastic,thermosetting

orelastomericmaterial.Theymustbecircular,compact,havetheextrudedinsulationandanyfillermustbenon-hygroscopic")issubstantiallycompact,aflameproofcablegland,incompliancewithIEC60079-1,maybeusedifitincorporatesasealingringanditisselectedinaccordancewithFigure2.Thecompliancewiththefig.2isnotrequiredifthecableglandcomplieswiththe60079-1standardandifasampleofthespecificcablehasbeensubjectedtorepeatedignitiontestsoftheflammablegasinsideofajunctionboxandnoignitionoccursoutsidethebox.

c) mineral-insulated cable withmetal-sheathed cable with or without plastic outer with an appropriate

flameproofcableglandcomplyingwithIEC60079-1;d)flameproofsealingdevice(forexampleasealingchamber)specifiedintheequipmentdocumentationor

complyingwith IEC60079-1 standardandusinga cablegland suitable for the cableused. The sealingdevice shall incorporate compound or other appropriate seals which permit the sealing aroundindividualcores.Thesealingdeviceshallbeplacedatthepointofentryofcablesintotheequipment;

e)flameproofcablegland,specifiedintheequipmentdocumentationorcomplyingwithIEC60079-1,filled

with compound seals or elastomeric seals that seal around the individual cores or other equivalentsealingarrangements.

Figure2

a) internalsourcesof ignitionincludesparksorequivalenttemperaturesoccurringinnormaloperationwhichcancauseignition.Anenclosurecontainingterminalsonlyoranindirectentryenclosure(see10.4.1ofIEC60079-14)isnotconsideredaninternalsourceofignition.

b) Theterm“volume”isdefinedinIEC60079-1standard.

Inthecurrentversion,inparagraph10.6.2,itisdescribedasfollows:Note:theversionsofthementionedstandards,withinthisdescription,mustobviouslybethosealignedwiththedateofissueoftheserules."10.6.2Selectionofcableglands"Thecableentrysystemshallcomplywithoneofthefollowing:a) Sealedcableglandsprovidedwithaspecialcompound(barriercableglands)accordingto IEC60079-1

andcertifiedsuchequipment;b) Cablesandcableglandsthatmeetallofthefollowing:

- CableglandsaccordingtoIEC60079-1andcertifiedasequipment- CablesusedaccordingtothespecificationsofArticle9.3.2a)ofIEC60079-14(Note1)- Thelengthofthecableisatleastequalto3m(Note2)

c) indirectentriesthroughtheuseofacombinationofan‘Exd’explosion-proofjunctionboxprovidedwithsealingbushinganda‘Exe’junctionbox

d) mineral insulated cables and metal sheath, with or without plastic coating, fitted with appropriate

flameproofcableglandcomplianttoEN60079-1e) explosion-proof equipment specified in the documentation or according to IEC 60079-1. The sealing

devicemustincorporateacompoundorothersuitablesealingmeans,aroundtheindividualcoresofthecable,whichdonotallowthepassageofanything.Thesealmustbeinstalledatthepointofcableentryintotheequipment.

Note1 The minimum cable length is specified to limit the potential hazard due to flame transmission

throughthecable(seealsoAnnexEofthesamestandard)Note2 If thecableglandandthecables inusearecertifiedasapartof theequipment (enclosures), the

complianceto10.6.2paragraphisnotnecessary.

Note1 With a sheath in thermoplasticmaterial, thermosetting or elastomeric. Theymust be circularandcompact.Anypaddingorsheathingmustbeextruded.Anyfillersmustbenon-hygroscopic.

Note2 The minimum cable length is defined in order to limit the potential danger due to thetransmissionof flame through thecable. For the testproceduresof restrictedbreathingcable(AppendixE,extractedfromEN60079-14),youhavetouseapieceofcablewithalengthof0.5mtobetested,once installed inasealedjunctionboxof5 liters (±0.2 liters), inconditionsofconstant temperature. The cable is considered acceptable if the interval of time required tobring down to 0.15 kPa (15 mm of water column) an internal overpressure of 0.3 kPa (30millimetresofwatercolumn)isequaltoorgreater5s.

Itisthereforeevidentthat,followingtheentryintoforceofthenewversionoftheIEC60079-14standard,thescenariohaschangedandtheuseofbarrier-typecableglandsresultsofprimaryimportance.2. Themethodsofsealingofthebarrier-typecableglandsWhat kind of sealant should be used to achieve a perfect flameproof protection on barrier-type cableglands?Therearetwodifferentmethodstobeusedfortherealizationofthe"Barrier".One,whichusesasasealantthesemi-solidtypewithtwocomponents,theotherthatusesaresin,alsotwo-component,butintheliquidstate.Thefirstsystemusesthesemi-solidsealantandmustbeperformedthefollowingoperations:

- mixingthetwosemi-solidcomponents,thuscausingachemicalreactionofunification- insertingaminimumpartofthiscompoundinsidethecablecoresand,subsequently,coveringallthe

surroundingparts- insertingthewholeintothehousingprovidedinthecablegland.

Thisoperation,afterhardening,doesnotallowacompletefilling(presenceofairpockets).Moreover,duringthepolymerizationphaseofthecompound,thecablesmustnotbetouchedatall,toavoidtheformationofairintersticesbetweenthecablesheathandthecompound.Thesecondsystemusesthebi-componentresinandmustbeperformedthefollowingoperations:

- preparing the"cablehead", inserting thespecialpre-drilledcap for theeffectivediameterofeachindividualcore

- fillingwiththebi-componentresinpreparedpreviouslyorfromthesinglepackagesuppliedwiththebarriercablegland.Thisoperationmustbecarriedoutdirectlyinsidethehousingdesignedforthisfunction.

This second system, being the resin of the liquid type, guarantees a perfect penetration between theindividual cores and outside them, guaranteeing in fact a correct finishing in full compliance with thereferencestandard.CortemGroup,alwaysattentivetoplantrequirements,afteracarefulanalysisoninstallationproblems,hasfavouredthesecondsystemthatallowsthe installer tocarryoutacorrectsystemand,at thesametime,verifythatitcorrespondstotheinstallationinstructionsgivenalongwiththecableglands.Weconcludebyrecallingthatallactivitiesaimedatsizingandselectionaretheprerogativeofthedesignerwhomust always refer to the specific mandatory regulations and that he is entirely responsible for theanalyses,calculationsandtheconsequentexecutiveproject,certifyingthecompliancewiththeregulations.