Installation, Maintenance and Debugging of Screw Chiller

Correct debugging of screw chiller is an important link to ensure the normal operation of refrigeration device, save energy consumption and prolong service life. For large and medium-sized refrigeration systems installed on site, before debugging, you should first be familiar with the layout and connection of the whole system according to the requirements of design drawings, and understand the external structure and component performance of each equipment, as well as the electric control system and water supply system. Before debugging, users should carefully read the product operation instructions provided by the manufacturer and proceed step by step according to the operation requirements.

1.Screw Chiller Debugging

Turn on the valve of the refrigeration system and start it for debugging. If it is found that the refrigerant has leaked completely or is insufficient, first find out the leakage point and eliminate the leakage phenomenon, and then add the specified brand of refrigerant according to the requirements of the product instruction manual, and pay attention to that the refrigerant filling amount should meet the technical requirements.

After the refrigerant filling is completed, the load can be debugged. Many screw chillers can simulate the main electric control system before starting, that is, the main engine of the unit is not powered on, and the control system is powered on, and then the electric control system of the unit is tested through the internal settings of the unit to see if the components are running normally. If there is any problem with the electronic control system, it can be solved in time. Finally, turn on the host power supply for debugging.

During debugging, special attention should be paid to the following points:

1) Check whether all valves in the refrigeration system are in a normal open state, especially the exhaust stop valve, and do not close it.

2) Open the cooling water valve of the condenser and the cooling water valve of the evaporator, and the flow of cold water and cooling water shall meet the requirements put forward by the manufacturer.

4) When the unit is started, check whether the parameters of the unit are normal according to the startup manual provided by the manufacturer. Record the data of screw chiller, especially some main parameters.

5) During the operation of the screw chiller, pay attention to whether the loading and unloading mechanism of the compressor works normally.

6) The safety protection devices installed in the refrigeration system should be used correctly, such as high and low pressure protection devices, cold water and cooling water cut-off flow switches, safety valves and other equipment, and they should be replaced in time if damaged.

7) If there is any abnormality in the screw chiller, it shall be stopped immediately for inspection.

Before debugging the refrigeration system, it is necessary to clean and dry the interior of the system. If the preliminary work is not carried out seriously, it will increase a lot of workload during debugging, and it will bring many hidden dangers to the future operation of the refrigeration device.

2. The screw chiller startup operation

1) Confirm whether the state of each relevant valve in the unit meets the startup requirements. Supply power to the electrical control device of the unit, and turn on the power switch to make the power control indicator light on.

2) Start the cooling water pump, cooling tower fan and chilled water pump, and you should be able to see the operation indicators of the three. Check whether the oil temperature of lubricating oil reaches 30℃. If it is less than 30℃, the electric heater should be turned on for heating, and the oil pump can be started at the same time to make the circulating temperature of lubricating oil rise evenly.

3) Turn off the compressor power supply and start the control switch. If the cooling water temperature is low, the fan of the cooling tower can be temporarily turned off.

4) Whether the noise and vibration of the chilled water pump, cooling water pump and cooling tower fan during operation, the outlet pressure of the water pump, water temperature and other indicators are within the normal working parameters.

5) Whether the oil temperature of lubricating oil is below 60℃ and the oil level is normal.

6) Whether the suction pressure value is within the range when the compressor is running at full load. Whether the exhaust pressure of the compressor is within the range and whether the exhaust temperature is below 100℃.

7) Whether the running current of the motor is within the specified range during the operation of the screw chiller compressor. If the current is too large, it should be adjusted to run at reduced load to prevent the motor from burning due to too large current.

8) Whether the sound and vibration of the compressor are normal during operation. In the above-mentioned items, if any abnormal situation is found, stop the machine immediately, find out the reason and troubleshoot before restarting the unit. Never let the screw chiller run with problems, so as not to cause major accidents.

3. Screw water cooling unit maintenance

1) Screw compressor Screw compressor is a key component of the unit, and the quality of the compressor is directly related to the stability of the unit. If the compressor breaks down. Because of the high installation accuracy of screw compressor, it is generally necessary to ask the factory to carry out maintenance.

2) Cleaning of condenser and evaporator Because the cooling water of water-cooled condenser is an open circulation loop, the tap water generally used is recycled through the cooling tower. When the content of calcium salt and magnesium salt in water is large, it is easy to decompose and deposit on the cooling water pipe to form scale, which affects heat transfer. Excessive scaling will also reduce the circulation cross section of cooling water, reduce the water volume and increase the condensation pressure. Therefore, when the quality of the cooling water used is poor, the cooling water pipe should be cleaned at least once a year to remove the scale and other dirt in the pipe.

There are usually two methods for cleaning condenser water pipes:

•Use a special cleaning brush to clean the pipe.

•Use a special cleaning agent to rinse circularly, or fill it in cooling water, and then change the solution after 24 hours until it is cleaned.

3) Replace the lubricating oil After long-term use of the unit, the oil quality of lubricating oil becomes worse, and impurities and moisture in the oil increase, so it is necessary to observe and check the oil quality regularly. Once the problem is found, it should be replaced in time, and the brand of the replaced lubricating oil must conform to the technical data.

4) Dry filter replacement Drying filter is an important component to ensure the normal circulation of refrigerant. Because water and refrigerant are immiscible with each other, if the system contains water, it will greatly affect the operating efficiency of the unit, so it is very important to keep the system dry, and the filter element inside the drying filter must be replaced regularly.

5) Calibration of safety valve The condenser and evaporator on the screw chiller are both pressure vessels. According to the regulations, a safety valve should be installed on the high-pressure end of the unit, that is, the condenser body. Once the unit is in an abnormal working environment, the safety valve can automatically release the pressure to prevent high pressure from causing harm to the human body. Therefore, the regular calibration of safety valves is very important for the safety of the whole unit. The condenser and evaporator on the screw chiller are both pressure vessels. According to the regulations, a safety valve should be installed on the high-pressure end of the unit, that is, the condenser body. Once the unit is in an abnormal working environment, the safety valve can automatically release the pressure to prevent high pressure from causing harm to the human body. Therefore, the regular calibration of safety valves is very important for the safety of the whole unit.

6) Charging of refrigerant If there are no other special reasons, the general unit will not produce a lot of leakage. If a certain amount of refrigerant leaks due to improper use or after maintenance, it is necessary to add refrigerant again.