Hitachi Primairy Series - Page 9

8 Repairing intrinsically safe components
• Donotapplyanypermanentinductiveorcapacitiveloadstothecircuitwithoutensuringthatthiswillnotexceedthe
permissible voltage and current for the equipment in use.
• Intrinsicallysafecomponentsaretheonlytypesthatcanbeworkedonwhileliveinthepresenceofaammable
atmosphere. The test device shall be at the correct rating.
• Replacecomponentsonlywithpartsspeciedbythemanufacturer.
• Otherpartsmayresultintheignitionofrefrigerantintheatmospherefromaleak.
9 Cabling
• Checkthatcablingwillnotbesubjecttowear,corrosion,excessivepressure,vibration,sharpedgesoranyotheradverse
environmental effects.
• Thecheckshallalsotakeintoaccounttheeffectsofagingorcontinualvibrationfromsourcessuchascompressorsor
fans.
10 Detection of ammable refrigerants
• Undernocircumstancesshallpotentialsourcesofignitionbeusedinthesearchingforordetectionofrefrigerantleaks.
• Ahalidetorch(oranyotherdetectorusinganakedame)shallnotbeused.
11 Leak detection methods
Thefollowingleakdetectionmethodsaredeemedacceptableforsystemscontainingammablerefrigerants:
• Electronicleakdetectorsshallbeusedtodetectammablerefrigerants,butthesensitivitymaynotbeadequate,ormay
needre-calibration.(Detectionequipmentshallbecalibratedinarefrigerant-freearea.)
• Ensure that the detector is not a potential source of ignition and is suitable for the refrigerant used.
• LeakdetectionequipmentshallbesetatapercentageoftheLFLoftherefrigerantandshallbecalibratedtothe
refrigerantemployedandtheappropriatepercentageofgas(25%maximum)isconrmed.
• Leakdetectionuidsaresuitableforusewithmostrefrigerantsbuttheuseofdetergentscontainingchlorineshallbe
avoidedasthechlorinemayreactwiththerefrigerantandcorrodethecopperpipe-work.
• Ifaleakissuspected,allnakedamesshallberemoved/extinguished.
• Ifaleakageofrefrigerantisfoundwhichrequiresbrazingisfound,alloftherefrigerantshallberecoveredfromthe
system,orisolated(bymeansofshutoffvalves)inapartofthesystemremotefromtheleak.
• Oxygenfreenitrogen(OFN)shallthenbepurgedthroughthesystembothbeforeandduringthebrazingprocess.
12 Removal and evacuation
• Whenbreakingintotherefrigerantcircuittomakerepairs–orforanyotherpurpose–conventionalproceduresshallbe
used.
• However,itisimportantthatbestpracticeisfollowedsinceammabilityisaconsideration.
• The following procedure shall be adhered to:
- Remove refrigerant;
- Purge the circuit with inert gas;
- Evacuate;
- Purge again with inert gas;
- Open the circuit by cutting or brazing.
• The refrigerant charge shall be recovered into the correct recovery cylinders.
• Thesystemshallbe“ushedout”withOFNtorendertheunitsafe.
• This process may need to be repeated several times.
• Compressedairoroxygenshallnotbeusedforthistask.
• FlushingshallbeachievedbybreakingthevacuuminthesystemwithOFNandcontinuingtolluntiltheworking
pressureisachieved,thenventingtoatmosphere,andnallypullingdowntoavacuum.
• Thisprocessshallberepeateduntilnorefrigerantiswithinthesystem.WhenthenalOFNchargeisused,thesystem
shallbeventeddowntoatmosphericpressuretoenableworktotakeplace.
• Thisoperationisabsolutelyvitalifbrazingoperationsonthepipe-workaretotakeplace.
• Ensure that the outlet for the vacuum pump is not close to any ignition sources and there is ventilation available.
SAFETY PRECAUTIONS
HO2019292HA
5
EN