Reasons for Compressor Oil Deterioration and Oil - adding Operations

Regarding the identification of the quality of refrigeration oil, the methods are as follows:
To identify whether the refrigeration oil has deteriorated, it should be identified through testing. In practical operations, it can also be simply determined from the color and smell of the oil whether the refrigeration oil can continue to be used.
When the refrigeration oil deteriorates, its color often darkens. Drop the oil on white paper. If there is no black in the central part of the oil drop, it indicates that the refrigeration oil has not deteriorated; if there is a black spot in the center of the oil drop, it means the refrigeration oil has started to deteriorate. When there is water in the oil, the transparency of the oil decreases, showing a dark green color. When there is more water and impurities mixed in the refrigeration oil, this identification experience is very effective. However, it is not necessary to precisely identify the quality of the oil. Considering operational economy, as long as the color of the oil significantly darkens or the compressor reaches the specified oil - change time, the oil - change operation should be carried out immediately.

If the compressor needs to be disassembled for repair or the quality of the refrigeration oil deteriorates and needs to be replaced, the operation steps for oil drainage and oil addition are as follows:
Turn the suction and discharge valve stems of the compressor to the top - closed position to isolate the compressor from the system. Since the compressor has a fault or the refrigeration oil is of poor quality and the compressor can no longer operate normally, the refrigerant in the crankcase cannot be discharged into the high - pressure area by the compressor.
Unscrew the oil drain plug at the bottom of the crankcase. What is discharged first is the refrigeration oil and refrigerant gas. If the inside of the crankcase is too dirty, the crankcase of the compressor can be cleaned.

Since the refrigeration oil in the crankcase has been completely drained and starting the compressor is not allowed, the compressor cannot be used to suck in new refrigeration oil. It is necessary to connect an external vacuum pump to evacuate the crankcase, and then use the vacuum pressure in the crankcase to suck in the refrigeration oil.
Connect a refrigerant - charging tube to any one of the three valves: the by - pass hole of the suction valve, the by - pass hole of the oil three - way valve, or the special oil - charging valve. The refrigerant - charging tube is connected to a service gauge valve, and the service gauge valve is connected to a vacuum pump through another refrigerant - charging tube.
Open the service valve and start the vacuum pump for a few minutes. When a vacuum is present in the crankcase, close the service gauge valve and remove the vacuum pump. Immerse the refrigerant - charging tube in the refrigeration oil, open the service gauge valve, and the refrigeration oil will be sucked into the crankcase.

Stop adding oil when the oil level reaches the oil level line. Connect the refrigerant - charging tube used for oil suction to the vacuum pump again, evacuate, then close the service valve and stop the vacuum pump.