The compressor is a complex machine running at high speed. It is a basic requirement to ensure that the crankshaft, bearing, connecting rod, piston and other moving parts of the compressor are fully lubricated to maintain the normal operation of the machine. For this reason, the compressor manufacturer requires to use the specified brand of lubricating oil and regularly check the oil level and color of lubricating oil. However, due to the negligence in the design, construction and maintenance of the refrigeration system, insufficient lubrication of moving parts caused by compressor oil shortage, oil coking and deterioration, liquid return dilution, refrigerant flushing, and the use of low-quality lubricating oil is common. Insufficient lubrication will cause wear or scratch on the bearing surface, and in serious cases, it will lead to axle seizure, piston seizure in the cylinder, as well as bending and fracture of the connecting rod.