crankshaft seal is bathed in lubricating oil at a pressure
equal to the suction pressure of the refrigerant. The first
indication of crankshaft seal failure is excessive oil
leaking at the shaft.
When the seal must be replaced or when it shows
signs of abnormal wear or damage to the running
surfaces, a definite reason can be found for the abnormal
conditions. Make an inspection to locate and correct the
trouble, or the failure will recur.
Seal failure is very often caused by faulty
lubrication, usually because of the condition of the
crankcase oil. A dirty or broken oil seal is generally
caused by one or both of the following conditions:
- Dirt or foreign material is in the system or system
piping. Dirt frequently enters the system at the time of
installation. After a period of operation, foreign material
will accumulate in the compressor crankcase, tending to
concentrate in the oil chamber surrounding the shaft
seal. When the oil contains grit, it is only a matter of time
until the highly finished running faces become
damaged, causing failure of the shaft seal.
- Moisture is frequently the cause of an acid
condition of the lubricating oil. Oil in this condition will
not provide satisfactory lubrication and will cause
failure of the compressor parts. Use a refrigerant
dehydrator when the compressor is put into operation if
you suspect that moisture may be a problem. Anytime
foreign material is found in the lubricating oil,
thoroughly clean the entire system (piping, valves, and
REMOVING A SHAFT SEAL.If a shaft seal
must be removed, proceed as follows:
If the seal is broken to the extent that it permits
excessive oil leakage, do NOT attempt to pump the
refrigerant out of the compressor. If you do, air
containing moisture will be drawn into the system
through the damaged seal. Moisture entering the
refrigerant system may cause expansion valves to
freeze. This can cause acid formation and other
problems. If oil is leaking excessively, close the
compressor suction and discharge valves and relieve the
pressure to the atmosphere by loosening a connection
on the compressor discharge gauge line.
Next, drain the oil from the compressor crankcase.
Since the oil contains refrigerant, it will foam while
being drained. Leave the oil drain valve or plug open
while you are working on the seal. This ensures that
refrigerant escaping from the oil remaining in the
crankcase will not build up pressure and blow out the
seal while it is being removed.
Remove the compressor flywheel (or coupling) and
carefully remove the shaft seal assembly. If the
assembly cannot be readily removed, build up a slight
pressure in the compressor crankcase. To do this,
slightly open the compressor suction valve. Take the
necessary precautions to support the seal and to prevent
it from being blown from the compressor and damaged.
INSTALLING A SHAFT SEAL.Clean and
replace the entire seal assembly according to the
Wipe the shaft clean with a linen or silk cloth; do
not use a dirty or lint-bearing cloth. Be careful not to
touch the bearing surfaces with your hands as you
unwrap the seal. Rinse the seal in an approved solvent
and allow it to air-dry. (Do NOT wipe the seal dry!) Dip
the seal in clean refrigerant oil. Follow the instructions
found in the manufacturers technical manual to insert
the assembly. Bolt the seal cover in place and tighten the
bolts evenly. Replace the flywheel and belts or coupling
and check and correct the motor and compressor shaft
alignment. To test the unit for leaks, open the suction
and discharge valves and use a halide leak detector.
Evacuating the Compressor
Whenever repairs to a compressor allow any
appreciable amount of air to enter the unit, the
compressor should be evacuated after assembly is
completed and before it is ready for operation The
proper procedure is as follows:
1. Disconnect a connection in the compressor
discharge gauge line between the discharge line stop
valve and the compressor.
2. Start the compressor and let it run until the
greatest possible vacuum is obtained.
3. Stop the compressor and immediately open the
suction stop valve slightly. This will blow refrigerant
through the compressor valves and purge the air above
the discharge valves through the open gauge line.
4. Close the discharge gauge line and open the
discharge line stop valve.
5. Remove all oil from the exterior of the
6. Test the compressor joints for leakage using the
halide leak detector.