The wet stroke of compressor, also known as return gas with liquid, is caused by liquid refrigerant entering the cylinder, which belongs to operation accident. The causes are as follows:

1. There is too much refrigerant in the system when the throttle valve is opened.

2. The refrigerant level in the system is too high.

3. After the system defrosts, the return valve is opened too quickly, so that the steam containing a lot of moisture enters the cylinder.

4. Compressor suction valve opened too fast.

5. The throttle valve for discharging air is opened too much.

The wet stroke of the compressor is shown as follows: the compressor pipe or the crankcase frosted, and the lubricating oil in the crankcase is frothy. Because the liquid is impossible for the compressor, when the piston goes up, due to the small area of the exhaust channel, the liquid can not be discharged from the exhaust channel in time, so that the pressure in the cylinder increases, and the safety cover is jacked up; it is usually called "knocking cylinder". If adjustment and maintenance are not carried out in time, the valve plate will be broken, and in serious cases, the cooling water pipe in the crankcase will be frozen and cracked, and the compressor will be scrapped due to lubrication failure.