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Address No.8 Building, Longxi Third Industrial Zone, Longcheng Street Office, Longgang District, Shenzhen
Maintenance and maintenance method of screw chiller
With the development of China's economy and the increase in production technology requirements, screw chiller has become an important aspect of the cooling demand of most enterprises. Therefore, screw chiller is more and more widely used in enterprises. However, the subsequent screw The maintenance and maintenance of the chiller has become an important aspect for owners of screw chiller companies.
(I) Preparations before the screw chiller starts:
The correct commissioning of the screw chiller is an important part to ensure the normal operation of the refrigeration unit, save energy consumption and long service life. For large and medium-sized refrigeration systems installed on-site, you should first be familiar with the layout of the entire system according to the design drawings before commissioning. And connection to understand the outline structure and component performance of each device, as well as electrical control systems and water supply systems. Users should carefully read the product operation manual provided by the factory before commissioning, and proceed step by step according to the operation requirements.
Preparation before commissioning
(1) Since the screw chiller is a medium-to-large refrigerator, it requires close cooperation in design, installation, and use during commissioning. In order to ensure that the commissioning work is carried out in an orderly manner, it is necessary to form a temporary commissioning team with personnel from relevant parties to comprehensively direct the commissioning work.
(2) The person in charge of commissioning should be fully familiar with the structure and performance of the screw-type chiller, be familiar with the safety technology of the screw-type chiller, clarify the method, steps and technical requirements of the adjustment method, and develop a detailed and specific commissioning plan. , The commissioning staff of each post clarified their own tasks and requirements.
(3) Check whether the installation of the screw chiller meets the technical requirements, whether the foundation of the screw chiller meets the requirements, and whether the size, specifications and materials of the connecting pipes meet the design requirements.
(4) The power supply system of the unit should be completely installed and debugged.
(5) Conduct water test separately for the cold water and cooling water systems, flush the dirt from the water system, and the pump should work normally, and the circulating water volume should meet the requirements of the working conditions.
(6) Clean up the environmental site for commissioning to be clean, bright and unobstructed.
(7) Prepare various general tools and special tools required for debugging.
(8) Prepare various measuring instruments, meters, such as pressure, temperature, flow, and time, required for commissioning.
(9) Prepare safety protection equipment necessary for commissioning.
2. Commissioning of screw chiller
(1) Charge of refrigerant. At present, refrigeration units are generally charged with refrigerant in accordance with regulations before leaving the factory. After installation on site, if no accidental damage is found in the visual inspection, the relevant valve can be directly started to debug. If it is found that the refrigerant has been leaked or insufficient, first find the leak point and eliminate the leakage phenomenon, and then add the refrigerant of the specified brand according to the product use statement, and pay attention to the refrigerant charge should meet the technical requirements.
(2) The screw chiller needs to be charged with refrigerant at the user's site. The refrigerant charge and refrigerant grade must be in accordance with regulations. Insufficient refrigerant charge will cause insufficient cooling capacity. Too much refrigerant charge will not only increase costs, but may also have an adverse impact on sports energy consumption.
(3) Before filling refrigerant, sufficient refrigerant should be prepared in advance. When filling, it can be filled directly from the special filling valve. Since the system is in a vacuum state, the pressure difference between the refrigerant and the system in the cylinder is large. When the valve is opened, the refrigerant quickly flows from the cylinder into the system. After the filling is completed, the liquid filling valve should be closed before removing the connection pipe.
(4) Commissioning of refrigeration system. After the refrigerant charging is completed, the load debugging can be performed. As the screw chiller has made great progress in terms of performance and electrical control in recent years, many screw chillers can perform simulated action detection on the main electronic control system before the official start-up, that is, the main unit of the unit is not powered on and the control system Power on, and then check the electrical control system of the unit through the internal settings of the unit to see if the components are operating normally. If there is any problem with the electronic control system, it can be resolved in time. Finally, power on the host computer for debugging. In the debugging process, pay special attention to the following points;
1) Check whether all the valves in the refrigeration system are in the normal open state, especially the exhaust shut-off valve. Do not close.
2) Open the cooling water valve of the condenser and the cold water valve of the evaporator. The flow of cold water and cooling water should meet the requirements of the manufacturer.
3) Observe whether the power supply voltage of the unit is normal before starting.
4) Start the unit according to the startup manual provided by the manufacturer.
5) After the unit is started, check whether the parameters of the unit are normal according to the startup manual provided by the manufacturer.
6) According to the screw-type cold water motorized data record table provided by the factory, various data of the screw-type chiller can be recorded, especially some main parameters should be recorded in detail.
7) During the operation of the screw chiller, attention should be paid to whether the compressor and the download mechanism work normally.
8) The safety protection devices installed in the refrigeration system, such as high and low pressure protection devices, cold water and cooling water cutoff flow switches, safety valves and other equipment, should be used properly. If damaged, they should be replaced in a timely manner.
9) If there is any abnormal condition of the screw chiller, it should be stopped immediately for inspection.
Before commissioning the refrigeration system, it is necessary to clean and dry the inside of the system. If the preliminary work is not carried out carefully, a lot of work will be added during commissioning, and it will bring many hidden dangers to the future operation of the refrigeration unit.
1) Whether the sound and vibration of the chilled water pump, cooling water pump and cooling tower fan are running, and whether the indicators such as the outlet pressure and water temperature of the water pump are within the normal operating parameters.
(2) Start-up operation of screw chiller
After the screw-type refrigeration compressor is tested and operated, and the problems found are dealt with, the normal operation procedure can be entered. Its operation method is:
(1) Confirm whether the state of the relevant valves in the unit meets the requirements for startup.
(2) Supply power to the unit's electrical control device, and turn on the power switch to make the power control indicator light.
(3) Start the cooling water pump, cooling tower fan and chilled water pump, and you should be able to see that the three operation indicators are on.
(4) Check if the lubricating oil temperature reaches 30 ° C. If it is less than 30 ° C, the electric heater should be turned on for heating. At the same time, the oil pump can be started to increase the circulation temperature of the lubricant evenly.
(5) Close the compressor power and start the control switch.
(6) If the cooling water temperature is low, the fan of the cooling tower can be temporarily turned off.
(7) Inspection of screw-type chiller during startup. After the unit is started and put into operation, it is necessary to pay attention to the inspection of the following to ensure the safe operation of the unit.
1) Whether the oil temperature of the lubricating oil is below 60 ° C and whether the oil level is normal.
2) When the compressor is running at full load, is the suction pressure value in the range of 0.36 --- 0.56MPA?
3) Whether the discharge pressure of the compressor is 1.55MPA and the discharge temperature is below 100 ° C.
4) 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 load reduction operation to prevent the motor from being burned due to the excessive running current.
5) Whether the sound and vibration of the compressor is normal.
If any abnormal situation is found in the above items, the machine should be shut down immediately, the cause should be identified, the fault should be eliminated, and then the unit should be restarted. Never run the screw chiller with problems to avoid major accidents.
(Three) stop operation of screw refrigeration compressor
The shutdown of screw refrigeration compressors can be divided into shutdown modes such as normal shutdown, emergency shutdown, automatic shutdown and long-term shutdown.
Operation method for normal shutdown
(1) Press the stop key to stop the compressor.
(2) Stop the operation of the cooling water pump cooling fan.
(3) Stop the operation of the chilled water pump.
(4) Turn off the main power.
Emergency shutdown of the unit
During the normal operation of the screw refrigeration compressor, if abnormal phenomena are found; in order to protect the safety of the unit, an emergency shutdown should be implemented. Its operation method is:
(1) Press the emergency stop switch to stop the compressor.
(2) Stop the chilled water pump, cooling water pump and cooling tower fan.
(3) Cut off the main power.
After the unit is shut down urgently, the cause of the failure should be identified in time. After the failure is eliminated, the unit can be restarted according to the normal starting method.
3. Automatic shutdown of the unit
During the operation of the screw refrigeration compressor, if the pressure and temperature of the unit exceed the specified range, the protection device in the unit control system will function and automatically stop the compressor. This phenomenon is called the automatic shutdown of the unit. When the unit stops automatically, the corresponding fault indicator on the unit's electrical control board will light to indicate the location of the fault. When this happens, after the main machine is stopped, other parts of the shutdown operation can be handled as emergency shutdown methods. After the shutdown operation is completed, the unit should be checked, and the fault can be restarted according to the normal startup procedure.
4. Long-term shutdown of the unit
As the screw-type refrigeration compressor used for the central air-conditioning cold source runs seasonally, the downtime of the unit is longer. In order to ensure the safety of the unit, when the machine is shut down during the season, the shutdown operation can be performed according to the method below.
(1) When the unit is operating normally, turn off the power of the unit.
(2) Remove the water from the condenser and evaporator after stopping operation, and drain the remaining water to prevent the internal heat transfer tube from freezing in winter.
(3) Close the relevant valves in the unit and check for leaks.
(Four) maintenance of screw chiller
The main content of screw chiller maintenance includes daily maintenance and regular maintenance. Regular maintenance can ensure the long-term normal operation of the unit, prolong the service life of the unit, and save cooling energy consumption. For screw-type chiller units, there should be operating records to record the unit's operating conditions, and maintenance maintenance files should be established. Complete technical information is helpful to find hidden troubles and take early measures to prevent them from appearing.
Screw compressor is a very critical component in the unit. The quality of the compressor is directly related to the stability of the unit. If the compressor fails, the installation accuracy of the screw compressor is high. Generally, it is necessary to ask the factory for repair.
2. Cleaning of condenser and evaporator
Since the cooling water of the water-cooled condenser is an open circulation circuit, the tap water generally used is circulated and used by the cooling tower. When the content of calcium and magnesium salts 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 can also reduce the cross-section of cooling water, reduce the amount of water, and increase the condensation pressure. Therefore, when the water shield using cooling water is poor, clean the cooling water pipe at least once a year to remove scale and other dirt in the pipe. There are two ways to clean the condenser water pipes:
(1) Use a special cleaning brush to clean the tube.
(2) Use a special cleaning agent to cycle the rinsing, or fill it with cooling water, and then change the solution after 24H until it is washed.
3. Change the lubricant
After the unit is used for a long time, the oil quality of the lubricating oil becomes worse, and the impurities and moisture inside 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. The oil grade to be replaced must conform to the technical data.
4.Drying filter replacement
Dry filter is an important part to ensure the normal circulation of refrigerant. Because water and refrigerant are incompatible with each other, if the system contains moisture, it will greatly affect the operating efficiency of the unit. Therefore, it is very important to keep the system dry. 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 regulations, a safety valve must be installed on the high-pressure side of the unit, that is, the condenser body. Once the unit is in an abnormal working environment, the safety valve can automatically vent Pressure to prevent possible damage to the human body caused by high pressure. Therefore, the regular verification of the safety valve is very important for the safety of the entire unit.
6. Refrigerant charging
If there is no other special reason, the general unit will not produce a large amount of leakage. If a certain amount of refrigerant leaks due to improper use or after maintenance, the refrigerant needs to be refilled. When filling refrigerant, pay attention to the brand of refrigerant used by the unit.