Maintenance method of ultra-low temperature chiller refrigeration system

Maintenance method of ultra-low temperature chiller refrigeration system

An ultra-low temperature chiller refers to a refrigeration unit whose chilled water temperature reaches below minus 35°C. The unit adopts two-stage compression refrigeration. The scroll compressor and piston compressor are combined to produce a freezing source of minus 35°C or even minus 60°C. To meet the requirements of the production process, to ensure the normal and smooth production.

　　 1. Leak detection of ultra-low temperature chiller system

　　 1. The refrigerant side of the unit has undergone strict leak detection procedures in the factory and during the commissioning process.

　　 2. After the unit is running, the high-pressure part should be checked with a leak detector to ensure the tightness of all connections.

　　 3. If there are any leaks, they should be dealt with immediately. Generally, the leaks can be eliminated by tightening the connection sockets or flange bolts, but there is also the possibility that the refrigerant must be recovered and then the leaks can be treated. Such as leakage at welded joints.

　　 2. System pressure leak detection

　　The standard pressure leak detection procedure of ultra-low temperature chiller is as follows:

　　 1. Fill a small amount of R-22 gas until the system pressure is 2PSIG.

　　 2. Fill nitrogen to the system to be 25~50PSIG. Ensure that the pressure reaches all parts of the system. You can open the oil filling valve slightly and check for refrigerant with a leak detector.

　　 3. Check every joint and weld, and strive to be careful and spend as much time as possible. The leak detection equipment used must be sensitive and reliable.

　　 4. Open the top bleed valve of the evaporator and condenser to confirm that no refrigerant is detected. If refrigerant is found, the end cover should be removed to eliminate internal leakage.

　　 5. Confirm that the system is completely sealed, and discharge the gas from the filling valve out of the system at an appropriate flow rate to play a certain purge function.

　　 3. Vacuum and drying of ultra-low temperature chiller system

　　 1. Connect the high-efficiency vacuum pump and mercury vacuum gauge in series to the charging valve of the system.

　　2. Open all the connecting valves, exhaust valves and valves of the vacuum gauge in the system. Confirm that all valves to atmosphere are closed.

　　 3. Start the vacuum pump and pump the vacuum of the system to 5mmHg.

　　4. If possible, 50oC hot water can be passed into the system to accelerate the evaporation of the system's internal liquid and increase the dryness.

　　 5. Close the shut-off valve and keep the mercury vacuum gauge.

　　 6. Keep the vacuum for 8 hours. If the vacuum rises to no more than 6.3mmHg, the vacuum test is considered qualified.

　　 7. If the vacuum rises above the standard, the leak detection must be repeated.