Correct commissioning directly impacts cooling performance, service life and operational safety for reciprocating, single-unit two-stage, cascade and screw refrigeration compressor systems.
Before startup, inspect piping, welds and all sealing joints for leakage. Perform pressure holding test and vacuum dehydration to remove moisture and non-condensable gas inside the circuit.
For reciprocating refrigeration compressors including small, medium, large 4-cylinder and large 6-cylinder models, check crankcase oil level and confirm crankcase heater works normally.
Single-unit two-stage refrigeration compressor requires extra interstage pressure verification before commissioning. Improper interstage pressure will trigger excessive discharge temperature alarm.
Cascade refrigeration unit commissioning must test high-stage and low-stage circuits separately. Do not charge low-stage refrigerant before high-stage circuit runs stably.
Screw refrigeration compressor commissioning needs slide valve function test. Verify capacity adjustment can smoothly move from 10% to 100% rated capacity without abnormal noise.
Check oil quality and oil cleanliness for all compressor types. Oil contamination above NAS 8 grade for piston compressors or NAS 6 grade for screw refrigeration compressor is not allowed.
Verify sensor calibration: evaporation pressure, discharge pressure, oil pressure and temperature transmitters must be calibrated before first startup to avoid false protection shutdown.
Check safety relief valves and pressure switches. All safety components must have valid calibration certificates and correct set pressure values before commissioning.
Power supply inspection: confirm voltage fluctuation stays within allowable range, and check phase sequence to prevent reverse rotation damage to screw refrigeration compressor.
Start the compressor under no-load condition first. Monitor suction superheat, discharge temperature and oil pressure differential for the first 30 minutes of running.
For reciprocating refrigeration compressors, observe vibration amplitude. Abnormal vibration usually indicates foundation settlement, shaft misalignment or liquid return risk.
Single-unit two-stage refrigeration compressor needs continuous monitoring of interstage temperature during commissioning. Discharge temperature must not exceed 180℃.
When commissioning cascade refrigeration unit, strictly control the temperature difference of cascade heat exchanger between 5K and 8K to guarantee system COP.
Screw refrigeration compressor needs inspection of oil injection flow. Insufficient injected oil will lead to rotor overheating and sealing failure during operation.
Suction filter pressure drop should be logged during commissioning. High pressure drop indicates residual welding slag or debris left inside the pipeline.
Adjust expansion valve opening slowly to stabilize suction superheat. Different compressor types have different target superheat ranges for optimal operation.
Piston compressors target suction superheat of 6–10K; single-unit two-stage maintains 8–12K; screw refrigeration compressor can run safely at 5–8K superheat.
Test all protection functions: overload, high discharge pressure, low oil pressure, high bearing temperature and liquid return protection interlock.
Run continuous load test for 8 hours after commissioning. Record cooling capacity, power consumption and all operating parameters every 30 minutes.
After load test, shut down the unit and perform re-inspection of oil condition, bolt tightness and joint sealing to eliminate hidden risks.
For xiteliduo reciprocating compressor piston units, check valve plate temperature and sound during commissioning, abnormal ticking signals valve plate damage.
Commissioning acceptance documents shall include pressure test record, vacuum record, sensor calibration report, 8-hour load test log and safety valve certificate.
If liquid slugging occurs during commissioning, stop the compressor immediately. Do not restart until the root cause of liquid return is fully eliminated.
For explosion-proof customized compressors, check flameproof joint clearance and cable sealing to meet Ex d II BT4 requirements before commissioning.
System commissioning for cascade refrigeration unit takes the longest time, as two independent refrigerant circuits require separate testing and parameter tuning.
Improper commissioning can reduce compressor service life by 20~40%, especially for single-unit two-stage refrigeration compressor and cascade refrigeration unit.
After commissioning completion, hand over operation manual, maintenance schedule and spare parts list to the on-site operation and maintenance team.
Train operators to monitor key parameters in real time, and define emergency shutdown procedures for overpressure, over-temperature and low oil pressure faults.
The first oil change is recommended after 500 running hours for newly commissioned piston compressors, to remove metal particles generated during running-in period.
For screw refrigeration compressor, inspect oil filter and oil separator element after the 500-hour running-in period and replace if pressure drop exceeds the threshold.
FAQ
Q: What pre-start inspection is required for reciprocating refrigeration compressors?
A: Check crankcase oil level, crankcase heater, piping tightness, vacuum dehydration and sensor calibration before startup.
Q: What special commissioning check is needed for single-unit two-stage refrigeration compressor?
A: Verify interstage pressure and monitor interstage temperature to prevent excessive discharge temperature.
Q: What is the commissioning sequence for cascade refrigeration unit?
A: Test high-stage circuit first and make it stable, then commission low-stage circuit and adjust cascade heat exchanger temperature difference.
Q: What is the target suction superheat for screw refrigeration compressor?
A: Recommended suction superheat 5K to 8K due to oil injection cooling design.
Q: How long is the continuous load test required during commissioning?
A: 8 hours continuous load test, log operating parameters every 30 minutes.
Q: What to do if liquid slugging occurs during commissioning?
A: Shut down the compressor immediately, find and eliminate liquid return root cause before restarting.
Q: When should the first oil change be done for newly commissioned piston compressors?
A: After 500 running hours to remove metal particles produced during running-in.
Common Commissioning & Commissioning Checkpoints for Industrial Refrigeration Compressor Systems
Correct commissioning directly impacts cooling performance, service life and operational safety for reciprocating, single-unit two-stage, cascade and screw refrigeration compressor systems. Before startup, inspect piping, welds and all sealing joints for leakage. Perform pressure holding test and vacuum dehydration to remove moisture and non-condensable gas inside the circuit. For reciprocating refrigeration compressors including small, medium, large 4-cylinder and large 6-cylinder models, check crankcase oil level and confirm crankcase heater works normally. Single-unit two-stage refrigeration compressor requires extra interstage pressure verification before commissioning. Improper interstage pressure will trigger excessive discharge temperature alarm. Cascade refrigeration unit commissioning must test high-stage and low-stage circuits separately. Do not charge low-stage refrigerant before high-stage circuit runs stably. Screw refrigeration compressor commissioning needs slide valve function test. Verify capacity adjustment can smoothly move from 10% to 100% rated capacity without abnormal noise. Check oil quality and oil cleanliness for all compressor types. Oil contamination above NAS 8 grade for piston compressors or NAS 6 grade for screw refrigeration compressor is not allowed. Verify sensor calibration: evaporation pressure, discharge pressure, oil pressure and temperature transmitters must be calibrated before first startup to avoid false protection shutdown. Check safety relief valves and pressure switches. All safety components must have valid calibration certificates and correct set pressure values before commissioning. Power supply inspection: confirm voltage fluctuation stays within allowable range, and check phase sequence to prevent reverse rotation damage to screw refrigeration compressor. Start the compressor under no-load condition first. Monitor suction superheat, discharge temperature and oil pressure differential for the first 30 minutes of running. For reciprocating refrigeration compressors, observe vibration amplitude. Abnormal vibration usually indicates foundation settlement, shaft misalignment or liquid return risk. Single-unit two-stage refrigeration compressor needs continuous monitoring of interstage temperature during commissioning. Discharge temperature must not exceed 180℃. When commissioning cascade refrigeration unit, strictly control the temperature difference of cascade heat exchanger between 5K and 8K to guarantee system COP. Screw refrigeration compressor needs inspection of oil injection flow. Insufficient injected oil will lead to rotor overheating and sealing failure during operation. Suction filter pressure drop should be logged during commissioning. High pressure drop indicates residual welding slag or debris left inside the pipeline. Adjust expansion valve opening slowly to stabilize suction superheat. Different compressor types have different target superheat ranges for optimal operation. Piston compressors target suction superheat of 6–10K; single-unit two-stage maintains 8–12K; screw refrigeration compressor can run safely at 5–8K superheat. Test all protection functions: overload, high discharge pressure, low oil pressure, high bearing temperature and liquid return protection interlock. Run continuous load test for 8 hours after commissioning. Record cooling capacity, power consumption and all operating parameters every 30 minutes. After load test, shut down the unit and perform re-inspection of oil condition, bolt tightness and joint sealing to eliminate hidden risks. For xiteliduo reciprocating compressor piston units, check valve plate temperature and sound during commissioning, abnormal ticking signals valve plate damage. Commissioning acceptance documents shall include pressure test record, vacuum record, sensor calibration report, 8-hour load test log and safety valve certificate. If liquid slugging occurs during commissioning, stop the compressor immediately. Do not restart until the root cause of liquid return is fully eliminated. For explosion-proof customized compressors, check flameproof joint clearance and cable sealing to meet Ex d II BT4 requirements before commissioning. System commissioning for cascade refrigeration unit takes the longest time, as two independent refrigerant circuits require separate testing and parameter tuning. Improper commissioning can reduce compressor service life by 20~40%, especially for single-unit two-stage refrigeration compressor and cascade refrigeration unit. After commissioning completion, hand over operation manual, maintenance schedule and spare parts list to the on-site operation and maintenance team. Train operators to monitor key parameters in real time, and define emergency shutdown procedures for overpressure, over-temperature and low oil pressure faults. The first oil change is recommended after 500 running hours for newly commissioned piston compressors, to remove metal particles generated during running-in period. For screw refrigeration compressor, inspect oil filter and oil separator element after the 500-hour running-in period and replace if pressure drop exceeds the threshold.
FAQ Q: What pre-start inspection is required for reciprocating refrigeration compressors? A: Check crankcase oil level, crankcase heater, piping tightness, vacuum dehydration and sensor calibration before startup. Q: What special commissioning check is needed for single-unit two-stage refrigeration compressor? A: Verify interstage pressure and monitor interstage temperature to prevent excessive discharge temperature. Q: What is the commissioning sequence for cascade refrigeration unit? A: Test high-stage circuit first and make it stable, then commission low-stage circuit and adjust cascade heat exchanger temperature difference. Q: What is the target suction superheat for screw refrigeration compressor? A: Recommended suction superheat 5K to 8K due to oil injection cooling design. Q: How long is the continuous load test required during commissioning? A: 8 hours continuous load test, log operating parameters every 30 minutes. Q: What to do if liquid slugging occurs during commissioning? A: Shut down the compressor immediately, find and eliminate liquid return root cause before restarting. Q: When should the first oil change be done for newly commissioned piston compressors? A: After 500 running hours to remove metal particles produced during running-in.
