Troubleshooting of Cold Storage Compressor Liquid Strike Failure | Solution for Liquid Return Protection and Gas Liquid Separators Configuration
Liquid impact is the most destructive fault of piston compressors. When liquid refrigerant enters the cylinder for compression, the instantaneous impact can cause valve plate breakage, piston pin deformation, and in severe cases, directly crack the cylinder body.
The rapid recovery of load, excessive opening of expansion valve, and the return of liquid after defrosting are the three major causes of liquid hammer, accounting for 82% of the total liquid hammer failures in cold storage compressors. These three causes should be avoided in advance during the debugging stage.
The Xitelidou semi closed piston unit is equipped with a gas-liquid separator on quick freezing and two-stage cryogenic models. The volume of the gas separator cylinder is selected based on 12 times the suction capacity of the compressor to intercept liquid refrigerant.
After the low-temperature cold storage is shut down, the refrigerant inside the coil migrates, and it is easy for the liquid to return when it is restarted. Install a crankcase heater to preheat the oil temperature to above 30 ℃ and reduce the amount of refrigerant oil migration.
The low suction pressure of the compressor is accompanied by signs of liquid return, and the frost on the outer wall of the return pipe extends to the compressor housing. If the frost on the housing exceeds 1/2, it indicates that the risk of liquid return is already at a high level.
The temperature difference between day and night in cold storage in tropical regions is large. After shutdown, the pressure on the condensing side drops, and the liquid refrigerant flows back to the evaporator. Small units can be equipped with solenoid valves to cut off the liquid supply pipeline during shutdown.
Many cold storage debugging personnel pursue fast heating, opening the expansion valve to the maximum at once, quickly cooling down in a short period of time, but continuously returning liquid, shortening the valve disc life to one-third of the original.
The frozen tunnels and freeze-drying units exported from foreign trade have insufficient overseas maintenance resources, and buyers are generally willing to additionally select two sets of protective accessories, gas-liquid separators and crankcase heating.
The anti liquid impact ability of screw refrigeration compressors is better than that of piston models, but if a large amount of liquid is continuously sucked in, it will still wash away the oil film on the rotor surface, causing the rotor wear clearance to increase.
The refrigeration maintenance company is repairing the liquid hammer unit, and cannot only replace damaged valve plates. The oil circuit must be cleaned synchronously. The liquid refrigerant dilutes the refrigeration oil, and residual oil will cause subsequent bearing wear.
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FAQ
What are the main damages caused by liquid impact on piston compressors? Easy to shatter valve plates, damage piston components, and even cause cylinder cracking.
2. Reference standards for volume selection of gas-liquid separators? Select the cylinder volume based on approximately 12 times the suction capacity of the compressor.
What is the function of the crankcase heater? Preheat the engine oil to reduce refrigerant dissolution and migration, which can cause liquid return during startup.
4. Where does the frosting on the shell belong to high-risk liquid return? If more than half of the shell is frosted, there is a high risk of liquid return.
What problems will arise if the expansion valve is opened too much? Rapid liquid return significantly shortens the lifespan of the valve disc.
6. Is the screw machine not afraid of liquid impact? Stronger impact resistance, but a large amount of backflow will still wear down the rotor.
7. Is it enough to only replace the valve plate for liquid hammer maintenance? Not enough, it is necessary to clean the oil circuit and remove the diluted refrigerant oil.
