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(one) Â Â Â Â Â Â Â Preparation before screw chiller start-up
The correct commissioning of the screw chiller is an important part of ensuring the normal operation of the refrigeration unit, saving energy and prolonging the service life. For on-site installation of large and medium-sized refrigeration systems, the requirements should be familiar with the layout and connection of the entire system, the outline structure and component performance of each equipment, as well as the electronic control system and water supply system. To this end, engineers such as refrigeration and hydropower should participate in the commissioning. Users should carefully read the product operation instructions provided by the factory before commissioning, and proceed step by step according to the operation requirements. The operator must undergo special training from the factory to obtain the operation certificate of the unit before the operation can be carried out, so as to avoid fatal damage to the unit caused by wrong operation.
1 . Preparation before commissioning
(1 ) Since the screw type chiller is a medium and large chiller, it needs to be closely coordinated 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 for the relevant personnel to form a temporary commissioning team to fully conduct the commissioning work.
(2 ) The personnel responsible for commissioning should be fully familiar with the structure and performance of the screw chiller, familiar with the safety technology of the chiller, clarify the method, steps and technical requirements to be debugged, formulate detailed and detailed commissioning plans, and make each post The commissioning staff clarifies 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 pipeline meet the design requirements.
(4 ) The power supply system of the unit should be fully installed and commissioned.
(5 ) Pass the water test on the cold water and cooling water system separately, flush the dirt of the waterway system, the water pump should work normally, and the circulating water quantity meets the requirements of working conditions.
(6 ) Clean and debug the environmental site to achieve clean, bright and smooth.
(7 ) Prepare the various common tools and special tools required for debugging.
(8 ) Prepare various measuring instruments and meters for pressure, temperature, flow, quality, time, etc. required for commissioning.
(9 ) Prepare the safety protection equipment necessary for commissioning operation.
2 . Screw chiller commissioning
(1 ) Â Â Â Â Â Â Â Â Â Â Charge of the refrigerant. At present, the refrigeration unit is generally filled with refrigerant before leaving the factory. After the installation on site, if no accidental damage is found in the visual inspection, the relevant valve can be opened directly (you should read the manufacturer's instruction manual first, in transit, on the unit). The valve is normally in the off state) for commissioning. If the refrigerant has been leaked or insufficient, first find the leak point and eliminate the leak, then add the required grade of refrigerant according to the product instruction manual. Note that the refrigerant charge should meet the technical requirements.
(2 ) Â Â Â Â Â Â Â Â Â Â Some screw chillers need to be filled with refrigerant at the user's site. The refrigerant charge and refrigerant grade must be in accordance with regulations. The refrigerant charge is insufficient. Will result in insufficient cooling. Excessive refrigerant charge will not only increase the cost, but also adversely affect the operating energy consumption.
(3 ) Â Â Â Â Â Â Â Â Â Â Adequate refrigerant should be prepared before charging the refrigerant. When filling, it can be directly charged 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 air in the connecting pipe should be blown out with the refrigerant first, so that the air does not enter the unit and affect the performance of the unit), the refrigerant is quickly replaced by the cylinder. In the flow system, after filling, the liquid filling valve should be closed first, and then the connecting pipe should be removed.
(4 ) Â Â Â Â Â Â Â Â Â Â Refrigeration system commissioning. After the refrigerant is charged (if the refrigerant needs to be charged), the load can be debugged. In recent years, screw chillers have made great progress in performance and electrical control. Many screw chillers can perform analog operation check on the main electronic control system before the official start-up, that is, the main unit of the unit is not energized, and the control system Power on, and then through the internal settings of the unit, the unit's electronic control system is tested, and the components are running normally. If there is any problem with the electronic control system, it can be resolved in time. After the zui, connect to the host power supply for debugging. During the debugging process, special attention should be paid to the following points:
1 ) Check that the valves in the refrigeration system are in the normal open state, especially the exhaust shut-off valve, and 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 factory.
3 ) Before starting, pay attention to observe whether the power supply voltage of the unit is normal.
4 ) Start the unit according to the start-up manual provided by the factory.
5 ) After the unit is started, check whether the parameters of the unit are normal according to the start-up manual provided by the factory.
6 ) According to the screw chiller operating data record table provided by the factory, the data of the screw chiller can be recorded. 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 downloading mechanisms of the compressor are working properly.
8 ) The safety protection devices installed in the refrigeration system, such as high and low pressure protection devices, cold water and cooling water water flow switch, safety valve, etc., should be used correctly. If there is damage, it should be replaced in time.
9 ) If the screw chiller has abnormal conditions, it should be stopped immediately for inspection.
Before the refrigeration system is commissioned, be sure to clean and dry the air conditioning system. If the preliminary work is not carried out seriously, it will increase the workload during the commissioning period, and it will bring many hidden dangers to the future operation of the refrigeration unit.
(2) Start-up operation of screw chiller
After the screw-type refrigeration compressor has undergone trial operation and processed the discovered problems, it can enter the normal operation procedure. Its method of operation is:
( 1 ) Confirm that the state of each relevant valve in the unit meets the requirements for power-on.
(2 ) Supply power to the unit's electrical control unit, and turn on the power switch to make the power control indicator light.
(3 ) Start the cooling water pump, cooling tower fan and refrigerant pump, and you should be able to see that the running indicators of the three 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, and the oil pump can be started to raise the lubricating oil circulation temperature evenly.
(5 ) After the oil pump is started, put the energy adjustment control valve in the deloading position and make sure the spool is in the zero position.
(6 ) Adjust the oil pressure regulating valve. The oil pressure is made 0.5 to O.6 MPa .
(7 ) Close the compressor power supply, start the control switch, open the compressor suction valve, and start the compressor after the delay. After the compressor is running, adjust the lubricating oil pressure to make it higher than the exhaust pressure 0.15 ~ 0.3 MPa . ( 8 ) Close the solenoid valve control circuit in the liquid supply line and start the solenoid valve. The liquid refrigerant is supplied to the evaporator, the energy regulating device is placed at the loading position, and the load is increased step by step over time. At the same time, observe the suction pressure, and adjust the expansion valve to stabilize the suction pressure at 0.36 ~ O.56MPa .
( 9 ) After the compressor is running, when the temperature of the lubricating oil reaches 45 °C , the power of the electric heater is turned off, and the inlet and outlet valves of the cooling water of the oil cooler are turned on, so that the oil temperature is controlled at 40 during the operation of the compressor. ~ 55 °C .
(10 ) If the cooling water temperature is low, the fan of the cooling tower can be temporarily turned off.
(11 ) Open the injection valve for 1 / 2 to 1 turn, and at the same time, the suction valve of the suction and the unit should be in the fully open position.
(12 ) Adjust the energy adjustment device to 100 % position while adjusting the expansion valve to maintain the suction superheat above 6 °C .
(13 ) Inspection of the start-up operation of the screw chiller. After the unit is started and put into operation, attention should be paid to the following to ensure the safe operation of the unit.
1 ) The sound and vibration of the refrigerant pump, cooling water pump and cooling tower fan during operation, whether the pump outlet pressure, water temperature and other indicators are within the normal working parameters.
2 ) Is the oil temperature of the lubricating oil below 60 °C , and whether the oil pressure is higher than the exhaust pressure by 0.15 ~ O.3MPa , and the oil level is normal.
3 ) When the compressor is at full load, the suction pressure value is in the range of 0.36 to 0.56 MPa .
4 ) Is the discharge pressure of the compressor below 1.55 MPa and whether the exhaust temperature is below 100 °C .
5 ) During the operation of the screw chiller compressor, the running current of the motor is within the specified range. If the current is too large, it should be adjusted to the load shedding operation to prevent the motor from being burnt due to excessive operating current.
6 ) Whether the sound and vibration of the compressor are normal.
If any abnormality is found in the above items, it should be stopped immediately. After identifying the cause and troubleshooting, restart the unit. Do not let the screw chiller run with problems to avoid major accidents.
(3) The normal operation of the screw chiller compressor
The signs of normal operation of a screw refrigeration compressor are:
(1 ) The compressor discharge pressure is 1.8 to 1.47 MPa (gauge pressure);
(2 ) The compressor discharge temperature is 45 ~ 90 °C , and the Zui height must not exceed 1.05 °C ;
(3 ) The oil temperature of the compressor is about 40 to 55 °C ;
(4 ) The oil pressure of the compressor is 0.2 to 0.3 MPa (gauge pressure) ;
(5 ) The sound should be uniform and stable during the operation of the compressor, and there is no abnormal sound;
(6 ) The condensing temperature of the unit should be 3 ~ 5 °C higher than the temperature of the cooling water ; the cold pole and temperature should be controlled at about 40 °C , and the inlet temperature of the condenser should be below 32 °C ;
(7 ) The evaporating temperature of the unit should be lower than the outlet water temperature of the refrigerant water by 3 to 4 °C , and the outlet water temperature of the refrigerant water is generally about 5 to 7 °C .
(4) Shutdown operation of screw refrigeration compressor
The shutdown of screw refrigeration compressors is divided into normal shutdown, emergency shutdown, automatic shutdown and long-term shutdown.
1. Normal shutdown operation method
(l ) Place the manual unloading control unit in the load shedding position.
(2 ) Close the solenoid valve and the outlet valve on the liquid supply line between the condenser and the hair dryer.
(3 ) Stop the compressor operation and close its suction valve.
(4 ) After the energy load shedding to zero, stop the oil pump work.
(5 ) Place the energy adjustment device in the " stop " position.
(6 ) Close the cooling water inlet valve of the oil cooler.
(7 ) Stop the operation of the cooling water pump and the cooling tower fan.
(8 ) Stop the operation of the refrigerant pump.
(9 ) Turn off the main power supply.
2. Emergency shutdown of the unit
In the normal operation of the screw refrigeration compressor, such as the abnormal phenomenon of the regulation; to protect the safety of the unit, emergency shutdown should be implemented. Its method of operation is:
(1 ) Stop the compressor operation.
(2 ) Close the suction valve of the compressor.
(3 ) Close the solenoid valve on the unit supply pipe and the outlet valve of the condenser.
(4 ) Stop the oil pump work.
(5 ) Close the cooling water inlet valve of the oil cooler.
(6 ) Stop the refrigerant pump, cooling water pump and cooling tower fan.
(7 ) Cut off the main power supply.
The shutdown method when the unit has a power failure or water stop during operation may refer to the relevant contents in the emergency shutdown of the centrifugal compressor.
After the emergency shutdown of the unit, the cause of the failure should be ascertained in time. After the fault 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 play a role and automatically stop the compressor operation. This phenomenon is called automatic shutdown of the unit. When the unit is automatically shut down, the corresponding fault indicator on the electrical control board of the unit will illuminate to indicate the location of the fault. When such a situation occurs, after the host is shut down, other parts of the shutdown operation can be handled according to the emergency shutdown method. After the shutdown operation is completed, the unit should be inspected. After the fault is removed, the unit can be restarted according to the normal startup procedure.
4. Long-term shutdown of the unit
Since the screw-type refrigeration compressor used for the central air-conditioning cold source is seasonally operated, the downtime of the unit is long. In order to ensure the safety of the unit, during the seasonal shutdown, the following operations can be performed.
(l ) When the unit is in normal operation, close the unit's outlet valve to make the unit perform load shedding operation, and pump all the refrigerant in the unit to the condenser. In order to stop the unit from being stopped due to too low suction pressure, the setting of the low pressure pressure relay can be adjusted to 0.15 MPa . When the suction pressure drops to about 0.15 MPa , the compressor stops, and when the compressor is stopped, the low pressure value can be adjusted back.
(2 ) Remove the water from the oil cooler, condenser, and evaporator after the operation is stopped, and drain the remaining water to prevent the internal heat transfer tubes from freezing in winter.
(3 ) Close the relevant valve in the unit and check for leaks.
(4 ) The lubricating oil pump should be started for 10 to 20 minutes every week , so that the lubricating oil can be evenly distributed to all working faces in the compressor for a long time, preventing the unit from being oil-deficient due to long-term shutdown, resulting in restarting. Difficulties.
(5) Maintenance of screw chillers
The main contents of screw chiller maintenance, including daily maintenance and regular maintenance. Regular maintenance and repair can ensure the long-term normal operation of the unit, prolong the service life of the unit, and also save energy consumption. For screw-type chillers, there should be a record of operations, record the operation of the unit, and establish a maintenance technical file. Complete technical information can help identify potential hazards and take early action to prevent obstacles.
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 the screw compressor, it is generally necessary to ask the factory for maintenance.
2 . Condenser and evaporator cleaning
The cooling water of the water-cooled condenser is an open circuit, and the tap water generally used is recycled through the cooling tower. When the content of calcium salt and magnesium salt in the water is large, it is easily decomposed and deposited on the cooling water pipe to form scale, which affects heat transfer. Excessive fouling also reduces the flow cross section of the cooling water, reduces the amount of water, and increases the condensing pressure. Therefore, when the water quality of the cooling water used is poor, the cooling water pipe is cleaned at least once a year to remove scale and other dirt in the pipe. There are usually two ways to clean the condenser water pipes:
(1 ) Use a special pig to clean the pipe.
(2 ) Rinse with a special cleaning agent, or fill in the cooling water, wait for 24h and then replace the solution until it is washed.
3 . Replacement of lubricant
After long-term use, the oil quality of the lubricating oil will deteriorate, and the impurities and moisture inside the oil will increase. Therefore, it is necessary to observe and inspect the oil quality regularly. Once the problem is found, it should be replaced in time. The replacement lubricant grade must comply with the technical data. 4 . Dry filter replacement
The drying filter is an important part to ensure the normal circulation of the refrigerant. Since 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 internal drying of the system. The filter element inside the drying filter must be replaced regularly.
5 . Safety valve check
The condenser and evaporator on the screw chiller belong to the pressure vessel. According to the regulations, the 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 be automatically vented. Pressure to prevent high pressure damage to the human body. Therefore, the regular calibration of the safety valve is very important for the safety of the entire unit.
6. Filling of refrigerant:
If there are no other special reasons, the general unit will not generate a lot of leaks. If a certain amount of refrigerant leaks due to improper use or after repair. It is necessary to re-add the refrigerant. To charge the refrigerant, you must pay attention to the grade of the refrigerant used by the unit.
(6) Operation management and shutdown notices
1. Screw chiller operation management precautions
(1 ) The normal opening and closing of the unit must be carried out in strict accordance with the steps of the operating instructions provided by the manufacturer.
(2 ) During the operation of the unit, the parameters should be recorded in a timely and correct manner.
(3 ) If there is an alarm stop during the operation of the unit, the relevant personnel should be notified in time to check the unit. It can also be directly with the factory.
(4 ) It is strictly forbidden to short the water flow switch during the operation of the unit to avoid freezing the water pipe.
(5 ) The computer room should be staffed by a special staff member. It is strictly forbidden for people to enter the machine room and operate the unit.
(6 ) The equipment room should be equipped with corresponding safety protection equipment and maintenance inspection tools, such as pressure gauges, thermometers, etc., and the tools should be stored in a fixed position.
2 . Screw type chiller shutdown notice
(1 ) The unit should be disconnected from the main power switch after shutdown.
(2 ) If the unit is in a long-term shutdown state, all the water inside the cold water and cooling water system should be drained to prevent rust. The water chamber end cover should be sealed.
(3 ) When the unit is in a long-term shutdown, it should be repaired and maintained.
(4 ) During the shutdown period, the unit should be completely covered to prevent dust accumulation.
(5 ) During the shutdown period, personnel unrelated to the crew must not touch the machine.
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Screw chiller maintenance and maintenance method
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With the development of China's economy and the improvement of production process requirements, screw chillers have become an important aspect of the cooling demand of most enterprises. Therefore, screw chillers are used in enterprises more and more widely, but the screw that comes with them The maintenance and maintenance of chillers has also become an important aspect of the owners of screw chillers. Some maintenance and maintenance methods for screw chillers are briefly introduced: