Service manual

24
Service Information
Always wearprotectiveclothingwhenthereis
ariskofexposuretoliquidHFC-134a.Where
splashingispossible,always weareyeprotection
andafaceshield.
Combustibility of HFC-134a
HFC-134aisnonammableatambient
temperaturesandatmosphericpressure.However,
testshaveshownHFC-134atobecombustible
atpressuresaslowas5.5psig(139.3kPa
absolute)at177°C(350°F)whenmixedwithair
atconcentrationsgenerallygreaterthan60%
volumeair.Atlowertemperatures,higherpressures
arerequiredforcombustibility.(HCFC-22isalso
combustibleatpressuresaboveatmosphericinthe
presenceofhighairconcentrations).Testresults
andcalculationshaveshown:
•  Atambienttemperature,allconcentrations
ofHFC-134ainairarenonammableat
pressuresbelow15psig(205kPaabsolute).
•  CombustiblemixturesofairandHFC-
134awillnotformwhenliquidHFC-134a
ispumpedintoclosedvesselifinitial
airpressureinvesselislimitedtoone
atmosphereabsoluteandnalpressureis
limitedto300psig(2,170kPaabsolute).
Ifinitialairpressureisgreaterthanone
atmosphere,combustiblemixturesmayform
astankislled.
Basedonaboveinformation,thefollowing
operatingpracticesarerecommended:
Leak Testing
•  EquipmentshouldNEVER beleaktested
withapressurizedmixtureofHFC-134aand
air.HFC-134amaybesafelypressuredwith
drynitrogen.
Bulk Delivery and Storage
•  Tanksshouldnormallybeevacuatedatstart
oflling,andshouldneverbelledwhile
underpositiveairpressure.
•  Tankpressureshouldneverbeallowedto
exceed300psig(2,170kPa)whenllingwith
HFC-134a.Reliefdevicesoneithertanks
orHFC-134asupplysystemusuallyprevent
this.
•  Tankpressuresshouldbemonitored
routinely.
•  Airlinesshouldneverbeconnectedto
storagetanks.
Filling and Charging Operations
•  Beforeevacuatingcylindersorrefrigeration
equipment,anyremainingrefrigerantshould
beremovedbyrecoverysystem.
•  Vacuumpumpdischargelinesshouldbefree
ofrestrictionsthatcouldincreasedischarge
pressuresabove15psig(205kPa)andresult
informationofcombustiblemixtures.
•  Cylindersorrefrigerationequipmentshould
normallybeevacuatedatstartoflling,and
shouldneverbelledwhileunderpositiveair
pressure.
•  Finalpressuresshouldnotexceed300psig
(2,170kPa).
•  Filledcylindersshouldperiodicallybe
analyzedforair(nonabsorbablegasorNAG).
Refrigerant Recovery Systems
Efcientrecoveryofrefrigerantfromequipment
orcontainersrequiresevacuationattheendof
therecoverycycle.Suctionlinestoarecovery
compressorshouldbeperiodicallycheckedfor
leakstopreventcompressingairintotherecovery
cylinderduringevacuation.Inaddition,therecovery
cylinderpressureshouldbemonitored,and
evacuationstoppedintheeventofarapidpressure
riseindicatingthepresenceofnoncondensable
air.Therecoverycylindercontentsshouldthen
beanalyzedforNAG,andtherecoverysystem
leakcheckedifairispresent.DONOTcontinueto
evacuatearefrigerationsystemthathasamajor
leak.
Thermal Decomposition
HFC-134avaporswilldecomposewhenexposed
tohightemperaturesfromamesorelectric
resistanceheaters.Decompositionmayproduce
toxicandirritatingcompounds,suchashydrogen
uoride.Thepungentodorsreleasedwillirritate
thenoseandthroatandgenerallyforcepeople
toevacuatethearea.Therefore,itisimportantto
preventdecompositionbyavoidingexposureto
hightemperatures.