With the development of our country’s economy and the improvement of production process requirements, screw chillers have become an important aspect of the production cooling needs of most enterprises. Therefore, screw chillers are used more and more widely in enterprises. However, the screw chillers that follow The care and maintenance of screw chillers has also become an important aspect for business owners who own screw chillers.

With the development of our country’s economy and the improvement of production process requirements, screw chillers have become an important aspect of the production cooling needs of most enterprises. Therefore, screw chillers are used more and more widely in enterprises. However, the screw chillers that follow The care and maintenance of screw chillers has also become an important aspect for business owners who own screw chillers.

（一）Preparations before starting the screw chiller:

The correct debugging of the screw chiller is an important link to ensure the normal operation of the refrigeration device, save energy consumption, and extend the service life. For large and medium-sized refrigeration systems installed on site, before debugging, you should first follow the design drawing requirements, familiarize yourself with the layout and connections of the entire system, understand the appearance structure and component performance of each equipment, as well as the electrical control system and water supply system, etc. Users should carefully read the product operating instructions provided by the manufacturer before debugging, and proceed step by step according to the operating requirements.

1 . Preparation before debugging

(1) Since the screw chiller is a medium-to-large refrigeration machine, close cooperation in design, installation, and use is required during debugging. In order to ensure that the debugging work proceeds in an orderly manner, it is necessary for relevant personnel to form a temporary commissioning team to fully direct the debugging work.

(2) The person responsible for debugging should be fully familiar with the structure and performance of the screw chiller, familiar with the safety technology of the refrigeration machine, clarify the debugging methods, steps and technical requirements that should be met, formulate a detailed and specific debugging plan, and make each position The debugging personnel clearly understand their 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, specification, and material of the connecting pipes meet the design requirements.

(4) The power supply system of the unit should be fully installed and debugged.

(5) Carry out a water flow test on the cold water and cooling water systems separately, flush the dirt in the water system, the water pump should work normally, and the circulating water volume should meet the requirements of the working conditions.

(6) Clean up the debugging environment to make it clean, bright and smooth.

(7) Prepare various general tools and special tools required for debugging.

(8) Prepare various pressure, temperature, flow, quality, time and other measuring instruments and instruments required for debugging.

(9)Prepare necessary safety protection equipment during debugging and operation.

2 . Commissioning of screw chiller

(1) Refrigerant charging. At present, refrigeration units are generally filled with refrigerant according to regulations before leaving the factory. After on-site installation, if no accidental damage is found during the visual inspection, the relevant valves can be opened directly (the manufacturer’s instruction manual should be read first, and during transportation, the unit must be The valve is generally in a closed state) startup and commissioning. If it is found that the refrigerant has leaked out or is insufficient, you should first find the leakage point and eliminate the leakage, and then add the specified brand of refrigerant according to the product instruction manual. Note that the refrigerant charge should meet the technical requirements.

(2) Some screw chillers need to be filled with refrigerant at the user’s site. The refrigerant filling amount and refrigerant grade must be in accordance with regulations. The refrigerant charge is insufficient. Will lead to insufficient cooling capacity. Excessive refrigerant charging will not only increase costs, but may also have adverse effects on operating energy consumption.

(3) Sufficient refrigerant should be prepared before charging refrigerant. 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 in the cylinder and the system is large. When the valve is opened (refrigerant should be used to blow out the air in the connecting pipe first to avoid air entering the unit and affecting the performance of the unit), the refrigerant quickly flows out of the cylinder. After filling the liquid into the system, the liquid filling valve should be closed first, and then the connecting pipe should be removed.

(4) Refrigeration system debugging. After refrigerant charging is completed (if refrigerant charging is required), load debugging can be performed. Since screw chillers have made great progress in performance and electrical control in recent years, many screw chillers can perform simulated action checks on the main electronic control systems before they are officially started. That is, the main unit of the unit is not powered on, and the control system Turn on the power, and then check the unit’s electronic control system 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 solved in time. Finally, turn on the host power and perform 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 a normal open state, especially the exhaust stop valve. Do not close it.

2) Open the cooling water valve of the condenser and the cold water valve of the evaporator. The flow rate of cold water and cooling water should meet the requirements of the manufacturer.

3) Start-up operation of screw chiller3) Before starting, you should pay attention to observe whether the power supply voltage of the unit is normal.

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) Various data of the screw chiller can be recorded according to the screw chiller operating data record sheet provided by the manufacturer. In particular, some main parameters must be recorded clearly.

7) During the operation of the screw chiller, attention should be paid to whether the upper and lower mechanisms of the compressor are working properly.

8) 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. If damaged, they should be replaced in time.

9) If any abnormality occurs in the screw chiller, it should be shut down immediately for inspection.

Before debugging the refrigeration system, the inside of the system must be cleaned and dried. If the preliminary work is not carried out carefully, a lot of workload will be increased during the commissioning period, and it will bring many hidden dangers to the future operation of the refrigeration device.

(二) Start-up operation of screw chiller

After the screw refrigeration compressor has undergone trial operation and the discovered problems have been dealt with, it can enter the normal operation procedure. How it works is:

(1) Confirm whether the status of the relevant valves in the unit meets the startup requirements.

(2) Supply power to the electrical control device of the unit and turn on the power switch to make the power control indicator light on.

(3) Start the cooling water pump, cooling tower fan and chilled water pump, and you should see the operation indicators of the three on.

(4) Check whether the lubricating oil temperature reaches 30 ℃. If the temperature is less than 30°C, the electric heater should be turned on for heating, and the oil pump can be started to increase the lubricating oil circulation temperature evenly.

(5) Turn off the compressor power and start the control switch.

(6) If the cooling water temperature is low, the cooling tower fan can be temporarily turned off.

(7) Inspection during startup of the screw chiller. After the unit is started and put into operation, attention should be paid to checking the following contents to ensure the safe operation of the unit.

1) Check the sound and vibration of the chilled water pump, cooling water pump, and cooling tower fan during operation, and whether the outlet pressure, water temperature and other indicators of the water pump are within the normal operating parameters.

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

3) When the compressor is running at full load, whether the suction pressure value is within the range of 0.36~0.56MPa.

4) Whether the exhaust pressure of the compressor is 1.55MPa and the exhaust temperature is below 100 ℃.

5) During the operation of the screw chiller compressor, whether the operating current of the motor is within the specified range. If the current is too large, it should be adjusted to load reduction operation to prevent the motor from burning due to excessive operating current.

6) Whether the sound and vibration of the compressor are normal during operation.

Among the above items, if any abnormality is found, the unit should be shut down immediately, the cause should be identified, and the fault should be eliminated before restarting the unit. Never allow the screw chiller to operate with problems to avoid causing major accidents.

(三) Shutdown operation of screw refrigeration compressor

1. Operation method of normal shutdown

(1) Press the stop button to stop the compressor.

(2) Stop the cooling water pump and cooling tower fan.

(3) Stop the operation of the chilled water pump.

(4) Turn off the main power supply.

2. Emergency shutdown of the unit
During the normal operation of the screw refrigeration compressor, if there is any abnormality, in order to protect the safety of the unit, an emergency shutdown should be implemented. How it works 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 supply.

After the unit is shut down in an emergency, the cause of the fault should be identified in time. After the fault is eliminated, the unit can be restarted according to the normal startup method.

3. Automatic shutdown of the unit

During the operation of the screw refrigeration compressor, if the pressure and temperature values of the unit exceed the specified range, the protection device in the unit control system will take effect and automatically stop the compressor. This phenomenon is called the automatic shutdown of the unit. When the unit automatically shuts down, the corresponding fault indicator light on the electrical control board of the unit will light up to indicate the location of the fault. When this happens, after the main machine is shut down, the shutdown operations of other parts can be handled according to the emergency shutdown method. After completing the shutdown operation, the unit should be inspected and the unit can be restarted according to the normal startup procedure after the fault is eliminated.

4. Long-term shutdown of the unit

Since the screw refrigeration compressor used as the cold source of central air conditioning operates seasonally, the unit has a long downtime. In order to ensure the safety of the unit, when shutting down during the season, the following methods can be used to shut down the unit.

(1) When the unit is running normally, turn off the power of the unit.

(2) Remove the water from the condenser and evaporator after stopping operation, and drain away the remaining water to prevent the internal heat transfer tubes from freezing in winter.

(3)Close the relevant valves in the unit and check if there is any leakage.

(四) Maintenance of screw chiller

The main contents of screw chiller maintenance include daily maintenance and regular inspection. Regular inspection and maintenance can ensure the long-term normal operation of the unit, extend the service life of the unit, and also save refrigeration energy consumption. For screw chillers, there should be operation records to record the operation of the unit, and maintenance technical files should be established. Complete technical information will help you discover hidden faults and take early measures to prevent obstacles from occurring.

1 . Screw compressors

The 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. Due to the high installation accuracy requirements of screw compressors, it is generally necessary to ask the manufacturer for maintenance.

2 . Cleaning of condenser and evaporator

Since the cooling water of the water-cooled condenser is an open circulation loop, the generally used tap water is recycled through the cooling tower. When the calcium salt and magnesium salt content in the water is large, it is easy to decompose and deposit on the cooling water pipes to form scale, which affects heat transfer. Excessive scaling will also reduce the circulation cross-section of the 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 pipes should be cleaned at least once a year to remove scale and other dirt in the pipes. There are usually two methods for cleaning condenser water pipes:

(1) Use a special cleaning brush to clean the pipe.

(2)Use a special cleaning agent to circulate and rinse, or fill it in cooling water, and then replace the solution after 24 hours until it is clean.

3. Change lubricating oil

After the unit has been used for a long time, the quality of the lubricating oil will deteriorate, and the impurities and moisture inside the oil will increase. Therefore, the oil quality must be regularly observed and checked. Once a problem is discovered, it should be replaced in time. The grade of lubricant replaced must comply with the technical data.

4. Filter dryer replacement

The dry filter is an important component to ensure the normal circulation of refrigerant. Since water and refrigerant are immiscible with each other, 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 inside of the system dry. The filter element inside the dry 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 end of the unit, that is, the condenser body. Once the unit is in an abnormal working environment, the safety valve can automatically discharge. pressure to prevent possible damage to the human body caused by high pressure. Therefore, regular calibration of the safety valve is very important for the safety of the entire unit.

6. Refrigerant charging

If there are no other special reasons, 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. It is necessary to refill the refrigerant. When charging refrigerant, you must pay attention to the brand of refrigerant used by the unit.