解放军装备学院-小学优秀班主任事迹材料

surfaces,manyminutetree-likecarbonac eouspathsortracks
racksareoriented
randomly, butgenerallypropagatebetweentheelectrodes
under theinfl-
tuallyaseriesoftracksspanstheelectrodeg ap,andfailure
occursbyshortingoftheelectrodes.< br>5.3Theconditionsspecifiedhereinareintended,asino ther
trackingtestmethods,toproduceaconditioncon ducivetothe
formationofsurfacedischargesandposs iblesubsequenttrack-
nditionsarechosentoreprodu ciblyandconve-
nientlyaccelerateaprocess;forthi sreason,theyrarely
-
fore,whiletrackingtests servetodifferentiatematerialsunder
givenconditi ons,resultsoftrackingtestscannotbeusedto
infere itherdirectorcomparativeservicebehaviorofan
,tr ackingtestresultsprovideatool
forjudgingthesuit abilityofmaterialsforagivenapplication.
Thesuit abilitycanonlybeverifiedthroughtestingthedesign
inactualenduseorunderconditionswhichsimulateenduse as
closelyaspossible.
tus
6.1Thesimplified electricalcircuitryusedinthistestis
essaryinfor mationonthecleanli-
nessofapparatus,entialcompo nentsare
asfollows:
6.1.1VariablePowerSource ,consistingofatransformer
typesupply,suchasthec ombinationT1andT2inFig.1,with
avariableoutputof 0to1000V,60Hzcapableofmaintaining
acurrentof1A( 1kVA).
6.1.2Voltmeter(V1),capableofmeasuringthe varyinga-c
outputofthepowersource.A0to600-Vvolt meterwithan
accuracyofatleast62.5%offullscale.< br>6.1.3Ammeter(A1),witharangeof0to1Aa-candan
a ccuracyofatleast610%offullscale.
6.1.4CurrentLi mitingResistor(R1),continuouslyvari-
able,wirew ound,ratedatgreaterthan1A.
6.1.5ShortingSwitch( S1),single-polesingle-throwrated
at1000Vandgrea terthan1A.
N
OTE
1—
ispossibletocouple thevariableresistorwiththeautotransformerwhich
givesanautomaticsettingofthecurrentthroughoutthera ngeofthe
eneveritisnecessarytocheckthecalibrati onofthe
instrument,theshortingactioncanbeaccomp lishedbyajumperwire
uplingoftheautotransformerw iththe
variableresistorcanbeconsideredanotherop tion.
6.1.6Over-CurrentRelay(R0),whichhastobein sertedin
thecircuitshallnottripatcurrentsupto0. 1Aandthetripping
timeonshortcircuitshallbeatlea st0.5s(thecurrentshallbe
limitedonshortcircuitt o1Awithatoleranceof610%ata
powerfactorof0.9to1. 0).
N
OTE
2—SomeinstrumentshaveusedaHeine mannbreaker,whichis
probablythecloseststandardc ommercialbreakertothatdescribedinthe
eakerisHei nemannModelSeriesJA,
thetrippingactioncanbeacco mplishedwithelectroniccircuitry.
6.1.7TestingFi xture(J1),adjustableplatformwhichsup-
portsthes pecimenandelectrodesetup.
6.1.8PlatinumElectrod es,havingarectangularcrosssec-
tionmeasuring5by 2mm(0.2by0.08in.),extending20mm
(0.8in)minimumf romsuitablemountingshanks(Fig.2).The
endofeache lectrodeismachinedtoforma30°chisel-point
edge,h avingaradiusfrom0.05to0.10mm,extendingalong
the 5-mm(0.2-in)theradiusthat
generallyresultsfromp olishinga“Omm”radiuselectrode.
Sincethedirectio nofpolishmayinfluencetheresults,all
electrodessh ouldbepolishedinadirectionperpendicularto
thelo ngdimensionoftheelectrodeface.
6.1.9DroppingApp aratus,whichshoulddroptheelectro-
lyteprecisely asspecifiedshouldalsobeameansof
electricallystar tingandstoppingthedroppingoftheelectrolyte
aswe llasacountingdeviceformonitoringthenumberof
fice diameterofthedropmechanismisapproxi-
r,itmayben ecessarytoadjustthis
diametersomewhatsoastoobta intheproperdropsizein
accordancewith9.2.
ts< br>7.1ElectrolyteSolutionofAmmoniumChlorideinWater :
7.1.1Prepareasolutionofammoniumchlorideatanap -
proximateconcentrationof0.1%bydissolving1gofr eagent
erusedshall
haveavolumeresistivityofn olessthan0.5MVcmat23°C.
Allowthesolutiontostand overnightinacovered,butnot
sealed,container.
7.1.2Measuretheresistivityofthesolutionusingacond uc-
tivitycellandana-cbridge,ormeter,followingt hemanufac-
turer’esistivityis38565Vcmat236
1
⁄
2
°C,esistivity
isoutsidetheaboveli mits,adjusttheconcentrationuntilthese
mentisacc omplishedbyadding
waterorNH
4
Cl.
FIG. 1ElectricalCircuitComponents

FIG.2Electr odes(Radius0.05to0.1mm)
7.1.3Calibratetheconduc tivitycellwith0.01Npotassium
chloridecalibratin gsolutionwhichisavailablefromthecell
manufactur er.
ecimens
8.1Typicaltestspecimenscanbe50-m m(2in.)or100-mm
(4in.)m
thicknessshallbe2.5m m(0.100in.).Atleastfivespecimens
ofeachsamplesha llbetested.
8.2Variationsinvaluescanresultfroma lackofuniformity
ofdispersionofthematerialthrou ghoutthemoldedspecimen
,caremustbetakento
pr eparespecimensthatareasuniformaspossible,bothwithi n
theparticularspecimenandfromonespecimentoanot her.
8.3ConditioningshouldbeinaccordancewithPro cedureA
ofPracticeD618.
8.4Specimensmustbecl eanofdust,dirt,oil,orother
dedsurfacemustbesmoo thand
scratch-free.
8.5Testthinmaterialsbyfir stclampingthemtogether
tightlytoformaspecimenha vingathicknessascloseas
possibletotherecommende dthickness.
ationandStandardization
9.1Parti allysupporttheelectrodesbyadjustablepivotarms
a ndrestonthetestspecimenasshowninFig.2,exertinga
forceof100g(3.5oz).
9.2Thedropheightfortheelec trolyteshouldnotbemore
than40mm(1.6in.)ding
deviceisdesignedtostoreanaqueoussolutionanddeliver
psizeis
tobe20+5−0mm
3
(0.0015in.
3
)andthedroprateistobe1
drop3065s.(Thedrops izecanbemeasuredbyusingasmall
calibratedgraduat etoaccumulateanumberofdropstoobtain
anaccurater eading.)
9.3Allowapproximately15dropsofelectrol ytetodrop
fromtheapparatusintoabeakerorothercon tainersoasto
removeanysolutionwithahighconcentr ationofammonium
chloride.
9.4Reformtheelectr odeswhentheedgesareroundedin
excessof0.1-mmdiam eterorwhenburrsorroughedgesare
observableat153m agnifieelectrodeswhen
sharpeningormachiningfails torestorethespecificdimen-
sionsoftheelectrodesa ndthequalityofthechiseledge.
9.5Reproducibility ofresultsisimprovedbycleaningthe
electrodesafte reverytwoorthreetests.
5
9.6Thepowersourceis settothedesiredvoltagewith
nothingbutairbetween theelectrodes(switchopen).The
shortingswitchisc losedandthecurrentlimitingresistor
adjustedtogi veareadingof1A.
ure
10.1Conductthetestinadra ft-free,cleanenvironmentata
temperatureof2065°C .
10.2Fillthedroppingassemblywithsolutionandset the
counterto0.
10.3Setthepowersourcetothede siredvoltageandadjust
inaccordancewith9.6.
1 0.4Placethetestspecimenonthesupportingplatformsothattheelectrodescanbeplacedonthespecimen.
10 .5PositiontheelectrodesasshowninFig.2sothatthe
chiseledgescontactthespecimenata60°anglebetween
electrodesandsothatthechiselfacesareparallelinthe vertical
planeandareseparatedby460.2mm(0.16in.) .
N
OTE
3—Itisrecommendedthatcontactofthe electrodeswiththe
specimenshallbesuchthatwhenal ightsourceissoplacedthatthelight
reachestheeyea longthesurfaceofthespecimen,nolightisvisible
ti svisibleduetothe
electrodeedgeshavingbecomeroun ded,theedgesmustbereground.
10.6Opentheshorting switchandbeginthesequenceof
dropswiththetimeint ervalbetweendropssetat3065s.
nditionisusu-
a llywelldefinedwithasuddensurgeoccurringinthecurrent
(fromessentially0toalmost1A)accompaniedbyacorr e-
spondingdropinvoltage.
10.8Atestmayberepe atedonagivenspecimenprovided
theelectrodegapisp ositionedaminimumof25mm(1.0in.)

positionoft henewtestmustbecleanandunsplashedbya
priortest.
10.9Obtainonereadingoneachoffivespecimensofa
thisprocessin
accordancewith10.8,atdifferentvo ltagelevelssuchthatat
leasttwolevelsproducefail uresinlessthan50dropsandtwo
levelsgreaterthan50 drops.
No.P13CrystalBayCleaningCrocusCloth,avai lablefrom3MCo.,hasbeen
foundsatisfactoryforthis method.
5

10.10Testvoltagesshouldbeli mitedto600Vorless.
Testingathighervoltageswillg enerateelectricdischarges
abovethesurfaceofthes pecimen,whichwillproduceerro-
neousresults.
10.11Whentestingatvoltagesinthelowestrange(below150V)theremaynotbesufficientenergytovaporizecom-
pletelytheelectrolytesolutionthathasbeenplaced between
,iffloodingoccurs,thetestshouldbe
dis continued.
ation
11.1Plotthenumberofdropsofe lectrolyteatbreakdown
urvenotethevoltagewhichco rre-
thecomparativetrackindex(CTI)
(seeFig.3 ).

12.1Reportthecomparativetrackingindexfor eachmate-
rialtested,andincludethefollowing:
12.1.1Descriptionofthematerialtested,
12.1.2Re sistivityoftheelectrolyte,
12.1.3Testtemperatur e,
12.1.4Testvoltageandnumberofdropsofelectroly teto
failure,foreachtest,
12.1.5TheCTIvaluei nvoltsderivedinaccordancewith
11.1,and
12.1. 6Visualobservationsofspecimenbehavior,suchas
me ltingoftheplastic,flameignition(ifitoccurs),andthet ype
oferosionthathasoccurredonthesurfaceofthete stspecimen
betweentheelectrodes.
ionandBias< br>13.1Whilesomevarianceinbreakdowndatacanbeex-
FIG.3TypicalTrackingVoltageCurve
pectedwiththi stestmethod,particularlyasthetestvoltage
approa chesanasymptoticvalue,CTIvaluesderivedtherefrom
generallyshowaninterlaboratoryrangeof625V,intrala bo-
rvariationsinCTI
approaching650Vormorear elikelytoresultifmeticulous
attentiontotheproce dureisnotemployed.
13.2Astatementaboutbiascanno tbemadeforthistest
methodbecauseastandardrefere ncematerialofknown
trackingindexisnotcurrentlya vailable.
ds
14.1CTI;comparativetrackinginde x;tracking;contamina-
tion;trackingresistanceANNEX
(MandatoryInformation)
INESSOFAPPARA TUS
A1.1Cleanlinessoftheapparatusisessentialtoo btaining
pliesespeciallytothehypodermic
need le,theelectrodes,andthecontaminantliquiddeliverysystemcomponents.
done
bysquirtingreagentg radeacetonefromalaboratorywash
bottleontotheele ctrodetipsandallowingtheexcessacetone
heelectro deswiththe
acetone-filledtissuetoremoveresiduest hatmightbepresent
etheelectrodescarefullyto
onalacetone
leaning,theelectrodes
maystillsh owadarkdiscolorationbutitisnotnecessaryto
heele ctrodeswithdistilled
waterandwipedry.
A1.1.2 Itisimportanttocleantheneedleafteranytestin
whi chthetrackingphenomenoncreatesalargeflameorsoot
heneedleafteranytestin
whichthedropsofcontamina ntliquidwetthesideofthe
tissuesoakedwithacetone ,scrubtheneedle,
especiallyaroundthetip,toremov eanyresiduefromthe
heneedlebysquirtingwithdisti lledwater.
everaldropsofcontaminantliquidthroug h
psshouldfallstraightoffthetipwithout
ropsw ettheside,
continuetorepeatthecleaningstepsabov euntilthewettingof
thesideisnotevident.
A1.1 .3Cleanthecontaminantliquiddeliverysystemperi-
odicallybyflpparatushas
notbeenusedwithinanhour, severaldropsshouldbeflushed
throughthesystemprio rtostartingatest.

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Thisstandardissubjecttorevisionatanytimeby theresponsibletechnicalcommitteeandmustbereviewede veryfiveyearsand
ifnotrevised,mmentsareinvitedei therforrevisionofthisstandardorforadditionalstanda rds
mmentswillreceivecarefulconsiderationatamee tingoftheresponsible
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viewsknowntotheASTMCommitteeonStandards, 100BarrHarborDrive,WestConshohocken,PA19428.