Why Refrigeration Compressor Oil Deteriorates & How To Add Oil

By Author: Jane Yu
Total Articles: 29
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1. Why Refrigeration Compressor Oil Deteriorates

The lubricating oil used in a refrigeration compressors can lubricate the friction surface, reduce the friction work, friction heat and avoid wear of the compressor motor. Besides, filling the sealing part with oil can ensure its performance and prevent the leakage of refrigerant.

Here are four reasons why the oil of refrigeration compressor deteriorate.

1.1 Polluted by Water

If there is water mixed with the compressor oil in the refrigeration system due to improper operation, it will reduce the viscosity and the lubricating performance of the oil.

1.2 High Temperature Oxidation

Compressor oil oxidizes at a high temperature. When the exhaust temperature of the compressor is high, the viscosity of the oil will decrease, affecting its lubrication performance, and the oil may be oxidized.

In particular in high temperature environment, the compressor oil with poor thermal stability will decompose free carbon around the exhaust valve, resulting in the valve to close loosely and reduce the gas transmission coefficient of the compressor.

1.3 ...
... Mixed with Impurities

The quality of the compressor oil is reduced by the casting of sand and metal debris. In addition, poor-quality sealing gasket and sealing rubber ring can also aggravate the aging of the oil.

1.4 Mixed Types of Compressor Oil

If you mix various types of compressor oil of different properties of antioxidant additives, it may produce chemical changes, form precipitates, seriously affect the lubrication performance of the compressor, and even destroy the formation of the oil film.

2. Discern Quality Oil from the Deteriorated

In theory, to identify whether the compressor oil deteriorates, you could have a laboratory test. In practice, you can also judge whether the refrigeration oil can be used continuously simply from the color and smell of the oil.

If the compressor oil has deteriorated, its color tends to be darker. Drop the oil on the white paper, if the central part of the oil drop is not black, it means that the compressor oil is still in good quality. If there is a black spot in the center of the oil drop, it means the compressor oil has deteriorated.

When there is water in the oil, the transparency of the oil will go down and it will be dark green. This identification method works well when much water and impurities are mixed into the compressor oil.

However, it is not necessary to assess the quality of oil very accurately. To consider the economical issue and ensure the good operation of the compressor, as long as the color of the oil is obviously darker, or the using period reaches the specified oil change time, you should change the compressor oil immediately.

3. How to Add Compressor Oil

When the compressor needs to be disassembled for repair or the quality of the compressor oil becomes poor and needs to be replaced, you can follow the steps below to do the work.

Turn the suction and discharge valve stems of the compressor to the top to isolate the compressor from the system. Due to the compressor failure or poor quality of refrigeration oil, the compressor can not operate normally, so the refrigerant in the crankcase can not be discharged into the high-pressure area.

Screw off the engine oil drain plug at the lower part of the crankcase to drain the compressor oil and refrigerant gas. If the crankcase is dirty, clean the compressor crankcase.

The compressor oil in the crankcase has been exhausted and the compressor can not start and suck in new compressor oil. It is necessary to connect an external vacuum pump to vacuum the crankcase, and then use the vacuum pressure to suck in compressor oil.

You should connect a fluorine filling pipe to one of the three valves including the by-pass hole of the suction valve, the oil three-way valve, or the special oil filling valve. The fluorine filling pipe is also connected to a maintenance meter valve that is connected to the vacuum pump through another fluorine filling pipe.

Open the repaired valve and start the vacuum pump for a few minutes. When it is a vacuum in the crankcase, you should close the repaired valve and remove the vacuum pump. After immersing the fluorine-filled pipe into the compressor oil, you should open the repaired valve, and the refrigerator oil is sucked into the crankcase.

When the oil reaches the maximum oil level, you should stop refueling. Connect the fluorine-filled pipe used for oil suction to the vacuum pump. After pumping the vacuum, you should close the repaired valve, and the vacuum pump stops.
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