This paper introduces the faults and treatment methods encountered during the commissioning and commissioning of the screw refrigeration unit used by a mining bureau in Hebei.

2 unit composition

The unit consists of a 1215L GS D2 and two 16L GS D2 screw compressors, a cooling water system, a chilled water system and a supply system.

3 commissioning preparation

3.1 pressure test leak detection

Pressurize the refrigeration system with 1 MPa of dry compressed air for 24 h. To facilitate leak detection, add an appropriate amount of R22 to the compressed air, and then use an electronic halogen meter to detect each joint.

3.2 Determination of compressor steering

Point start is used to judge the steering; when the compressor is turned to the opposite direction, the two-phase line in the power phase line can be changed to meet the requirements.

3.3 plus refrigeration oil

First evacuate the system to a certain degree of vacuum, then put the pipe drawn from the system oil path into the oil in the tank, open the valve on the pipe, so that the frozen oil is sucked into the system.

3.4 Vacuuming

There are two ways to evacuate, one is to use the compressor of the refrigeration unit itself; the other is to use vacuum pump to complete. During the installation, a vacuum pump was used to evacuate and the interface was placed above the condenser.

L GS 2 screw chiller 3.5 plus liquid

When the vacuum reaches - 0101 MPa, close the filling valve before the vacuum suction valve and the condenser after the expansion valve, and then connect the system repair valve and the refrigerant cylinder with a pressure hose to open the refrigerant bottle valve. Run the air in the hose, tighten the connection between the hose and the filling valve, invert the refrigerant bottle, and use the vacuum to add the refrigerant to the system.

When the system refrigerant pressure and the pressure in the bottle are balanced, the refrigeration unit can be started. Gradually close the condenser outlet valve, close the repair valve, pump the refrigerant in the evaporator into the condenser, form a certain degree of vacuum, slowly increase the opening of the repair valve, slowly add liquid, with the increase of the amount of refrigerant The energy regulating valve should be adjusted to meet the compressor output power requirements required by the system.

Among the three units of the system, two large units each add 130kg, and one small unit adds 60kg.

4 debugging

4.1 Commissioning requirements

The commissioning of the chiller is to adjust the operating parameters of the plant to the required range, so that the screw chiller can meet the design requirements and operate safely and economically.

During the commissioning process, the main parameters evaporating pressure, evaporating temperature, condensing pressure, condensing temperature, compressor suction and exhaust temperature, and refrigerant temperature before the expansion valve are required to be adjusted within a reasonable range.

4.2 Debugging steps

4.2.1 Starting the cooling water system

1 Turn off the water pump outlet valve and turn on the motor; 2 When the motor is running normally, open the outlet valve; 3 Start the cooling fan for the cooling tower.

4.2.2 Starting the refrigerant water system

1 Open the refrigerant water inlet and outlet valve on the unit evaporator; 2 Close the pump outlet valve and start the motor; 3 When the motor is running normally, open the outlet valve.

4.2.3 Starting the compressor

1 start the oil pump; 2 start the compressor, measure the suction temperature of the compressor 15 °C, exhaust temperature 45 °C; 3 adjust the energy regulating valve, so that the compressor suction pressure is 015MPa, the exhaust pressure is 115MPa; 4 adjust the oil pump outlet Pressure, oil pump outlet pressure and compressor gas outlet pressure difference between 0115 ~ 013MPa; 5 adjustment expansion valve, evaporation temperature 5 °C, evaporation pressure 015MPa (gauge pressure); evaporator water temperature reaches 7 °C; condensation temperature 38 °C, refrigerant condensing pressure 115MPa (gauge pressure); 6 open the room fan coil fan, adjust the wind speed, measure the outlet temperature.

5 common troubleshooting during debugging

5.1 Pump surge and solution

The cooling water and the refrigerant water system have a large vibration sound during the work due to the uncleaning, and cause strong vibration of the pipeline. Open the vent valve in the cooling water and refrigerant water system and drain the air from the system.

5.2 System shaft seal leakage and treatment measures

Since the unit has put the lubricating oil into the compressor before installation, it is impossible to blow the unit. During the operation, the impurities in the system (mainly the sand after casting cannot be removed) make the shaft The seal was quickly worn and leaked during operation.

When processing, the refrigerant is first collected into the condenser; then the compressor is turned on to clean, the dirty refrigerant oil is discharged from the liquid storage tank, the oil filter is cleaned, and the mechanical seal is repaired.

5.3 Automatic protection component malfunction and solution 5.3.1 Oil pressure difference protector

The compressor must work with a stable oil pressure to ensure normal operation. At the beginning of the compressor, due to the fluctuation of the exhaust pressure, the difference between the oil pump outlet pressure and the compressor discharge pressure is difficult to maintain between 0115 and 013 MPa, causing the oil pressure difference protector to operate, forcing the compressor to stop, and it is difficult to complete the driving.

During processing, adjust the delay time of the time relay on the oil pressure difference protector to ensure that the compressor discharge pressure can work normally for a short period of time.

5.3.2 Expansion valve

Due to the presence of dirt in the refrigeration system, the suspended particles block the expansion valve passage during operation, resulting in greatly reduced system cooling capacity.

When disposing, remove the expansion valve, clean the valve core with gasoline and dry it, reassemble it after assembly, and replace the silica gel and copper mesh in the dry filter.

5.4 Fan Coil and Repair

During the commissioning process, the fan coil has an abnormal sound. After inspection, it was found that the unreasonable suspension in the transportation process and the suspension point in the installation were the main reasons for the deformation of the fan coil bellows.

After repairing the deformed bellows and changing the suspension point, the abnormal noise of the fan coil is eliminated.

6 conclusion

The L GS D2 screw chiller is a large refrigeration system. In the debugging process, the author gained some understanding: 1 system blowing is the basis for the smooth commissioning of the refrigeration unit.

2 In the operating state of the compressor, it is feasible to fill the refrigerant; at the same time, attention should be paid to the adjustment of the energy regulating valve to match the power consumption of the compressor.

3 The surge of the pump is generally the presence of air in the refrigerant water system or the cooling water system, and the venting of the pump can eliminate the surge of the pump.

4 Appropriate adjustment of the time relay can ensure the normal operation of the refrigeration system.

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