Analysis of the Mechanism of Oil Lack in Compressor

Analysis of the Mechanism of Oil Lack in Compressor

During the operation of the system, the lubricating oil is discharged from the compressor along with the refrigerant, and returns to the compressor after circulation, so lubricating oil will flow in and out wherever there is refrigerant.

There is an essential difference between the performance of refrigerant and lubricant. In the system cycle, refrigerant has two phases, namely liquid refrigerant and vapor refrigerant, while lubricant is basically liquid. When the refrigerant changes from liquid to gas, the lubricant will precipitate from the refrigerant. Under the influence of various factors, it is likely to be stored in a certain part or a certain structural point, resulting in the lubricant being unable to flow back to the compressor smoothly, causing the scroll compressor to lack oil. If the lack of oil is not resolved for a long time, it will lead to insufficient lubrication of the moving parts in the compressor.

Ensure oil return-installation

When the compressor discharges the refrigerant, it also discharges a small amount of refrigeration oil. Even if the oil intake rate is only 0.5%, if the oil cannot be circulated back to the compressor through the system, under ARI conditions, if the circulation volume is about 330kg\/h, the oil in the compressor can be pumped out in 50 minutes, and the compressor will burn out in about 25 hours.

Therefore, in order to ensure that there is no lack of oil in the operation of the compressor, we should start from the following two aspects:

1. Ensure that the refrigerant oil discharged from the compressor returns to the compressor;

2. Reduce the oil supply rate of the compressor.

First, ensure that the refrigerant oil discharged from the compressor returns to the compressor.

1. The flow rate of the refrigerant in the suction pipe (about 6m\/s) should ensure that the oil returns to the compressor, but the maximum flow rate should be less than 15m\/s to reduce pressure drop and flow noise. The horizontal pipe should also have a downward slope along the refrigerant flow direction, about 0.8cm\/m

2. Prevent refrigeration oil from being retained in the evaporator.

3. Ensure that the oil return hole of the gas-liquid separator is appropriate. If it is too large, it will cause wet compression. If it is too small, it will cause insufficient oil return and oil stagnation in the gas-liquid separator.

4. There should be no part of the system where oil is retained.

5. In the case of long pipelines and large drop, ensure that there is enough refrigeration oil in the compressor. Usually, a compressor with an oil level mirror is used to confirm that frequent startup of the compressor is not conducive to oil return.