- designed to reduce internal system pressure (in ref. and A.C.systems)
-used to remove moisture and other contaminants
-only use vacuum pump when system is at 0 gauge pressure
-pump is rated in CFM ( sucking power)
-blank off pressure ( lowest pressure that pump can attain)
Vacuum Pump Staging
Single
-Generally two stage Vacuum pressure is deeper (20 microns)
Double ( two stage)
- first stage pump must achieve rated CFM level
- second stage creates deeper vacuum
Gas Ballast
• open either before or immediately after starting vacuum pump
• close gas ballot after vacuum pump pulls to appox. 100o microns
• gas ballast helps to prolong oil life by reducing efficiency of second stage of vacuum pump
• seal is provided by the oil
• oil is hyrdroscopic ( likes water)
Storage
• change oil when vacuum Pump is not sucking any more on the micron gauge, first check gauge for leaks
Vacuum Pump Contaminants
• moisture
• refrigerant
• air
• metal filings
• corrosion
• acid
• sludge
Water (moisture)
• invisible (vapour)
• visable (droplets)
• when Vacuum oil and moisture mix water forms acids and oil and water forms sludging fine globules
• Water + ref. = corrosion from acid (sludge)
• moisture + heat = acid
• moisture + heat + ref. = more acid
-for each 18 degrees rise in temp above 68 F, acid formation doubles Corrosion: attaches to metallic surfaces and leaves a solid detachable product
-Sludge exists as slimy liquids, fine powders, and granular or sticky solids (sludge will corrode whatever it clings to)
Vacuum Pump Applications
Newly installed systems
• moisture
• metal filings
• manufacturing
• blazing residue (solids)
• gaseous contaminants
• carbon or gaseous contaminants from chemical reactions during brazing process
Ref. failed systems
• acids which formed from burn out
• burn out particulate
• moisture
Non ref. failed systems
• moisture
• minimal contamination as the ref. in the system was in reasonably good condition
Pump Maintenance
• follow instructions
• keep outside clean
• always ensure inlets are capped
• change oil after each use
• power flush pump on a regular basis
• use quality oil
• check motor coupler
• before each use:
• visually inspect for external damage
• ensure ISO valve is in proper starting position
• check length and size of extension cord
• open gas ballast valve
• in cold weather move pump to warm ambient before using outside or cold area
Thermister Vacuum Gauge
• micron gauge- found on some manifold gauge sets however not very accurate
• to test system you must hook up and apply vacuum for 15 min. at 500 microns
• meter must be vertical in relation to gas flow
• if metering devise gets oil droplets in it; it may contaminate the system ( use contact cleaner)
29.92 inch Hg Vac. = 0 microns boiling point of water will be 80 F
29.90 = 500 microns -10 F
28.92 = 25401.07 microns
1” Hg Vac. = 25401.07 microns
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