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Proper commissioning of screw chillers is an important step in ensuring the proper operation of cooling systems, saving energy consumption, and extending their service life. For large and medium-sized refrigeration systems installed on-site, before commissioning, it is necessary first to familiarize oneself with the layout and connections of the entire system as specified in the design drawings, to understand the physical structure of each device and the performance of its components, as well as the electrical control system and water supply system. Before debugging, users should carefully read the product operation manual provided by the manufacturer and proceed step by step in accordance with the operating instructions. I. Commissioning of screw-type chiller units: Turn on the valves of the refrigeration system to start the commissioning process. If it is found that the refrigerant has been completely depleted or is insufficient, the leak location must first be identified and the leak fixed. Afterwards, add refrigerant of the specified grade in accordance with the instructions provided in the product manual; note that the amount of refrigerant filled must meet the technical requirements. After the refrigerant charging is completed, load testing can be carried out. Many screw-type chillers allow for simulated testing of their main electrical control systems before they are put into operation. In this process, the main unit of the chiller is not powered, while the control system is powered on; then, through settings within the chiller, the electrical control system is tested to determine whether all components are functioning properly. If any problems arise with the electronic control system, they can be resolved promptly. Finally, connect the power to the host computer to proceed with debugging. During the debugging process, special attention should be paid to the following points: 1) Check whether all valves in the refrigeration system are in their normal open position, especially the exhaust stop valve, which must not be closed. 2) Open the cooling water valve of the condenser and the cold water valve of the evaporator; the flow rates of cold water and cooling water should meet the requirements specified by the manufacturer. 3) Before starting, it is necessary to check 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 all its parameters are normal according to the startup manual provided by the manufacturer. Record all the data related to screw-type chiller units, making sure to note down some of the key parameters in particular. 5) During the operation of the screw chiller, it is necessary to check whether the upper and lower moving 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, flow switches for cold water and cooling water supply interruption, safety valves, etc., should be used properly; any damaged devices must be replaced promptly. 7) If any abnormality occurs in the screw-type chiller, it should be stopped immediately for inspection. Before commissioning the refrigeration system, it is essential to ensure that the interior of the system is clean and dry. If the preliminary work is not carried out carefully, it will increase the workload during commissioning and pose many potential problems for the subsequent operation of the refrigeration system. II. Startup procedures for screw-type chiller units 1) Verify that the status of all relevant valves in the unit meets the requirements for startup. Supply power to the aircraft’s electrical control unit and turn on the power switch to illuminate the power control indicator light. 2) Start the cooling water pump, cooling tower fan, and chilled water pump; the operation indicator lights for all three should be visible. Check whether the lubricating oil temperature has reached 30 ℃. If the temperature is below 30 °C, the electric heater should be turned on to provide heat; at the same time, the oil pump can be started to ensure a uniform increase in the temperature of the lubricating oil. 3) Turn off the power to the compressor and activate the control switch. If the cooling water temperature is low, the fan of the cooling tower can be turned off temporarily. 4) The sound and vibration levels of the chilled water pumps, cooling water pumps, and cooling tower fans during operation; whether various parameters such as the outlet pressure of the pumps and water temperature are within the normal operating range. 5) Is the oil temperature of the lubricating oil below 60 °C, and is the oil level normal? 6) Is the suction pressure within the specified range when the compressor is operating at full load? Is the exhaust pressure of the compressor within the specified range, and is the exhaust temperature below 100 ℃? 7) During the operation of the compressor in a screw-type chiller, is the motor’s operating current within the specified range? If the current is too high, it should be adjusted to operate under reduced load to prevent the motor from burning out due to excessive operating current. 8) Are the sound and vibration levels of the compressor normal during operation? Among the items mentioned above, if any abnormality is detected, the machine should be stopped immediately; after identifying the cause and fixing the fault, the unit can be restarted. Under no circumstances should a screw chiller be operated with problems, to avoid serious accidents. III. Maintenance of screw water-cooled chillers 1) Screw compressors The screw compressor is a very critical component in the chiller unit; the quality of this compressor directly affects the stability of the unit. If the compressor fails. Due to the high precision requirements for the installation of screw compressors, it is generally necessary to have the manufacturer carry out the repairs. 2) Cleaning of the condenser and evaporator: In water-cooled condensers, since the cooling water operates in an open circulation system, tap water is typically used and circulated through a cooling tower. When the levels of calcium and magnesium salts in water are high, they tend to decompose and deposit on the cooling water pipes, forming scale that hinders heat transfer. Excessive scaling also reduces the flow cross-section of the cooling water, decreases the water volume, and raises 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 within them. There are generally two methods for cleaning the water pipes in a condenser: using a specialized cleaning brush to clean the pipes. Use a specialized cleaning agent for cyclic flushing, or dilute it in cooling water; wait for 24 hours before changing the solution until it is thoroughly cleaned. 3) Replace the lubricating oil: After long-term use, the quality of the lubricating oil deteriorates, with an increase in impurities and moisture within it; therefore, it is necessary to regularly monitor and check the quality of the oil. Once a problem is detected, it should be replaced promptly, and the grade of the lubricating oil used for replacement must comply with the technical specifications. 4) Replacement of the dry filter: The dry filter is an important component that ensures proper circulation of the refrigerant. Since water and refrigerant are immiscible, the presence of water in the system will **affect the operating efficiency of the unit; therefore, it is very important to keep the system dry. The filter elements inside the dryer-filter must be replaced regularly. 5) Calibration of safety valves: The condenser and evaporator in screw-type chillers are both considered pressure vessels. According to regulations, safety valves must be installed at the high-pressure end of the unit, that is, on the condenser itself. In case the unit operates under abnormal conditions, these safety valves can automatically release pressure, thereby preventing potential harm to people caused by high pressures. Therefore, the regular calibration of the safety valve is extremely important for the safety of the entire unit. Both the condenser and the evaporator in a screw-type chiller are considered pressure vessels. According to regulations, a safety valve must be installed on the high-pressure side of the unit, that is, on the condenser itself. In the event that the unit operates under abnormal conditions, the safety valve can automatically release pressure, thereby preventing potential harm to people caused by high pressures. Therefore, the regular calibration of the safety valve is extremely important for the safety of the entire unit. 6) Refrigerant charging: Unless there are other special reasons, normal units do not experience significant leaks. If a certain amount of refrigerant leaks due to improper use or after maintenance, it is necessary to add more refrigerant.