StaticElectricityAshamelesslystolenintroductionAlbertNessSeptember15,2008SensoryEffectsSlide2StaticElectricity-DavidWechslerOctober,2002VisualEffectsSlide3StaticElectricity-DavidWechslerOctober,2002WorkplaceEffects?Slide4StaticElectricity-DavidWechslerOctober,2002StaticElectricity•3Steps1.Generation2.Accumulation3.Discharge•Control&Mitigation1)Whenevertwomaterialsareplacedincontact,anexchangeofchargeoccursbetweenthem.2)Unlessthematerialsareconductiveandelectricallybondedtogether,whenthesurfacesareseparatedeachacquiresanequalandoppositenetcharge.Thenetchargesdrainawaytogroundataratethatdependsontheconductivityofthematerials.3)Electricchargesmaybuilduponungroundedconductivematerials(suchasmetals)non-conductivematerials(mostplastics)untilTheelectricalbreakdownfieldofthesurroundings(usuallyair)isexceededandanelectrostaticdischarge(suchasaspark)occurs.Thestaticdischargemaybeofsufficientenergytoignitevaporsordust,dependingontheMinimumIgnitionEnergy(MIE)oftheignitablemixture.AGeneralStaticCondition-Slide6StaticElectricity-DavidWechslerOctober,2002Generation-StreamingCurrentSplashCharge+++++++---------------------++++++++++++DumpingPowderContactandFrictionalChargingInductionAccumulationofChargeChargeout+++Chargein+++ChargeOut(groundedvessels)•Conductiveliquid–Nearlyinstantaneous•Non-conductiveliquid-eventuallydissipatesingroundedvessels.5min1minRelaxationTime30min10,000gal5–10,000gal<5,000galExtrakicker-Examplesofsomenonconductiveliquidsthatwillaccumulatechargeandareflammable:gasolinepropanetoluenebutadienebenzenemineralspiritsstyrenemonomerSlide15StaticElectricity-DavidWechslerOctober,2002AccumulationofChargeonEquipment•Chargeonfluidplacesoppositechargeonequipment.•Conductiveequipment(metal),ifgrounded,safelybringschargetoground.•Chargeonnon-conductive(ornon-grounded)equipmentwilllingeronequipment.++++•Accumulatedchargesremaininnonconductiveandinnon-groundedvessels.ConductiveSectionsinnon-conductiveLineDischargeEffectOfFuelConcentrationOnIgnitionEnergyENERGYFORIGNITIONM.I.EL.F.L.U.F.LFLAMMABLERANGEM.I.E-MinimumIgnitionEnergyL.F.L.-LowerFlammableLimitU.F.L.-UpperFlammableLimitFlammableLimits-Lower(LFL)andUpper(UFL)FlammableLimitsSlide20StaticElectricity-DavidWechslerOctober,2002ApproximateValuesOfM.I.E.InAir*1.Gases:0.1MillijouleHydrogen=0.02mJ2.Liquids1.0MillijoulePentane=0.54mJStyrene=0.30mJ3:Dusts10MillijouleOrMore*Oxygen-EnrichedFuelsHaveMuchLowerM.I.E.’sMinimumIgnitionEnergySlide21StaticElectricity-DavidWechslerOctober,2002SparkSparkDischargeStaticElectricityControl•Groundallisolatedconductors•Reduceflowvelocity•Installdippipes•Movefiltersfurtherupstream•Eliminatetopelectrodes•Antistaticadditives,materials•IncreaseHumidity•IonizetheairGrounding&Bonding•Grounding.Theprocessofbondingoneormoreconductiveobjectstotheground,sothatallobjectsareatzero(0)electricalpotential;alsoreferredtoas“earthing.”•Bonding.Theprocessofconnectingtwoormoreconductiveobjectstogetherbymeansofaconductorsothattheyareatthesameelectricalpotential,butnotnecessarilyatthesamepotentialastheearth.ExampleBondingGroundingSlide28StaticElectricity-DavidWechslerOctober,2002Exampleofatankcardip-pipeliquidtransfersystemSafeChargeDischargefromBags+++-------ConductiveBagConductiveGlovesConductiveShoesConductiveFloor•Reducechargevelocity•Groundallisolatedconductors•Movefilterfurtherupstream•I...
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