The correct commissioning of screw chillers is an important step in ensuring the normal operation of refrigeration systems, saving energy consumption, and extending their service life. For large and medium-sized refrigeration systems installed on site, before debugging, it is necessary to first familiarize oneself with the layout and connections of the entire system according to the design drawings, understand the external structure and component performance of each equipment, as well as the electrical control system and water supply system. Users should carefully read the product operation manual provided by the manufacturer before debugging, and gradually follow the operation requirements.
1, Debugging of screw chiller unit
Open the valve of the refrigeration system and start debugging. If it is found that the refrigerant has already leaked or is insufficient, the leakage point should be identified and the leakage phenomenon should be eliminated first. Then, according to the requirements of the product manual, add the specified grade of refrigerant, and pay attention to the refrigerant filling amount that meets the technical requirements.
After refrigerant charging is completed, load adjustment can be carried out. Many screw chillers can perform simulated action checks on the main electrical control system before formal start-up, that is, when the main unit is not powered on, the control system is powered on, and then the electrical control system of the unit is checked through internal settings to ensure that the components are running normally. If there are any problems with the electronic control system, they can be resolved in a timely manner. Finally, power on the host and perform debugging.
During the debugging process, special attention should be paid to the following points:
1) Check if all valves in the refrigeration system are in the normal open state, especially the exhaust shut-off valve, and do not close it.
2) Open the cooling water valve of the condenser and the cold water valve of the evaporator, and ensure that the flow rates of cold water and cooling water meet the requirements set by the manufacturer.
3) Before starting, pay attention to observing whether the power supply voltage of the unit is normal. Start the unit according to the startup manual provided by the manufacturer.
4) After the unit is started, check whether the various parameters of the unit are normal according to the start-up manual provided by the factory. Record the various data of the screw chiller unit, especially the main parameters, which must be clearly recorded.
5) During the operation of screw chillers, attention should be paid to whether the up and down mechanisms of the compressor are working properly.
6) The safety protection devices installed in the refrigeration system, such as high and low pressure protection devices, cold water and cooling water cut-off flow switches, safety valves, etc., should be used correctly. If damaged, they should be replaced in a timely manner.
7) If there is any abnormal situation with the screw type chiller, it should be stopped immediately for inspection.
Before debugging the refrigeration system, it is essential 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 the debugging period and bring many hidden dangers to the future operation of the refrigeration unit.
2, Startup operation of screw chiller unit
1) Confirm whether the status of all relevant valves in the unit meets the startup requirements. Supply power to the electrical control device of the unit and turn on the power switch to turn on the power control indicator light.
2) When starting the cooling water pump, cooling tower fan, and chilled water pump, the operation indicator lights of all three should be visible. Check if the lubricating oil temperature has reached 30 ℃. If the temperature is below 30 ℃, the electric heater should be turned on for heating, and the oil pump can be started to evenly increase the circulating temperature of the lubricating oil.
3) Close the power supply of the compressor 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 sound and vibration of the chilled water pump, cooling water pump, and cooling tower fan during operation, as well as the outlet pressure and water temperature of the water pump, are within the normal operating parameter range.
5) Is the oil temperature of the lubricating oil below 60 ℃ and is the oil level normal.
6) Is the suction pressure value within the range when the compressor is operating at full load. Is the exhaust pressure of the compressor within the range and is the exhaust temperature below 100 ℃.
7) Is the operating current of the motor within the specified range during the operation of the screw chiller compressor. If the current is too high, it should be adjusted to reduce load operation to prevent the motor from burning out due to excessive operating current.
8) Whether the sound and vibration of the compressor during operation are normal. If any abnormal situation is found in the above items, the machine should be stopped immediately, the cause should be identified, the fault should be eliminated, and then the unit should be restarted. Never operate the screw chiller with problems to avoid causing major accidents.
3, Maintenance of screw water-cooled unit
1) Screw compressor
Screw compressor is a crucial component in the unit, and the quality of the compressor directly affects the stability of the unit. If the compressor malfunctions. Due to the high installation accuracy requirements of screw compressors, it is generally necessary to hire the manufacturer for maintenance.
2) Cleaning of condenser and evaporator
The cooling water of a water-cooled condenser is usually circulated through a cooling tower using tap water due to its open loop design. When the content of calcium and magnesium salts in water is high, they are easily decomposed and deposited on the cooling water pipes, forming scale and affecting heat transfer. Excessive scaling can also reduce the flow cross-section of cooling water, decrease the amount of water, and increase the condensation pressure. Therefore, when the quality of the cooling water used is poor, the cooling water pipes should be cleaned at least once a year to remove scale and other contaminants from the pipes.
There are usually two methods for cleaning the condenser water pipes:
Use specialized cleaning brushes to clean the pipes.
Use specialized cleaning agents to cycle and rinse, or fill with cooling water, and wait for 24 hours before changing the solution until it is thoroughly cleaned.
3) Replace lubricating oil
After long-term use, the lubricating oil quality of the unit deteriorates, and impurities and moisture inside the oil increase, so it is necessary to regularly observe and check the oil quality. Once a problem is discovered, it should be replaced in a timely manner, and the lubricating oil brand replaced must comply with the technical specifications.
4) Dry filter replacement
The dry filter is an important component to ensure the normal circulation of refrigerant. Due to the immiscibility of water and refrigerant, if there is moisture in the system, it will greatly affect the operating efficiency of the unit. Therefore, it is very important to keep the internal system dry, and the filter element inside the drying filter must be replaced regularly.
5) Verification of safety valve
The condenser and evaporator on the screw type chiller unit are both pressure vessels. According to 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 pressure to prevent high pressure from causing harm to the human body. So regular calibration of safety valves is very important for the safety of the entire unit.
The condenser and evaporator on the screw type chiller unit are both pressure vessels. According to 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 pressure to prevent high pressure from causing harm to the human body. So regular calibration of safety valves is very important for the safety of the entire unit.
6) Charging of refrigerant
Unless there are other special reasons, the unit generally does not produce a large amount of leakage. If a certain amount of refrigerant leaks due to improper use or after maintenance, it is necessary to add refrigerant again.
