Screw chiller maintenance and maintenance methods
With the development of China's economy and the requirements of the production process to improve, screw chiller has become an important aspect of the majority of enterprises in the production of cooling needs, so the screw chiller is used in the enterprise is more and more extensive, however, the screw chiller has become an important aspect of the business owners who have screw chiller, now briefly introduce the screw chiller. Consequently, the screw chiller maintenance and maintenance has also become an important aspect of the screw chiller owners, now briefly introduces some of the screw chiller maintenance and maintenance methods:
(a) Screw chiller start-up preparations Screw chiller correct commissioning is to ensure that the refrigeration unit to operate normally, saving energy, extending the service life of an important link. For field installation of large and medium-sized refrigeration system, before commissioning should first be required by the design drawings, familiar with the entire system layout and connection, to understand the shape and structure of each device and component performance, as well as the electronic control system and water supply system. For this reason, the commissioning should be refrigeration and water and electricity engineers to participate. Users in the commissioning should carefully read the product operating instructions provided by the factory, according to the operating requirements step by step. Operators must undergo specialized training by the factory and obtain the operating certificate of the unit before going on duty, so as not to bring fatal damage to the unit by wrong operation. 1 ． Preparation before commissioning
(1) Because the screw chiller belongs to the medium and large-scale refrigeration machine, so in the commissioning of the need for design, installation, use and other aspects of close cooperation. In order to ensure that the commissioning work in an orderly manner, it is necessary to form a temporary commissioning team from the relevant parties, the overall command of the commissioning work.
(2) The person in charge of commissioning should be fully familiar with the structure and performance of the screw chiller, familiar with the refrigeration machine safety technology, a clear method of commissioning, steps and technical requirements should be achieved, to develop a detailed and specific debugging plan, and make the positions of the commissioning staff clear their tasks and requirements.
(3) Check whether the installation of screw-type chiller meets the technical requirements, whether the foundation of the screw-type 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 pass the commissioning.
(5) Separate chilled water and cooling water system for the water test, flushing the water circuit system of dirt, the pump should work properly, the amount of circulating water in line with the requirements of the working conditions.
(6) clean up the environmental site of the commissioning, to achieve clean, bright, unobstructed. (7) ready to debug the various general tools and special tools required.
(8) ready to debug a variety of pressure, temperature, flow, quality, time and other measuring instruments, meters. ( 9) ready to debug the operation of the necessary safety protection equipment. 2 The Screw chiller debugging
(1) refrigerant charge. At present, the refrigeration unit in the factory are generally in accordance with the provisions of the refrigerant charge, site installation, appearance check if no accidental damage was found, you can directly open the valve (should read the factory's instruction manual, in transit, the unit on the valve is generally in a closed state) start debugging. If you find that the refrigerant has been leaked or insufficient, you should first find out the leakage point and exclude the leakage phenomenon, and then according to the requirements of the product instruction manual, add the specified grade of refrigerant. Note that the refrigerant charge should meet the technical requirements. (2) Some screw-type chiller needs to be charged at the user site refrigerant, refrigerant charge and refrigerant grade must be in accordance with the provisions. Insufficient refrigerant charge. Will lead to insufficient cold. Refrigerant charge is too much, not only will increase the cost, but also on the operation of the energy consumption may have a negative impact.
(3) before charging refrigerant, should have enough refrigerant in advance. Charging, can be charged directly from the special charging valve. As the system is in vacuum, the refrigerant in the cylinder and the system pressure difference is large, when the valve is opened (the refrigerant should be used first to blow out the air in the connecting tube, so as not to air into the unit, affecting the performance of the unit), the refrigerant flows rapidly from the cylinder to the system, after charging, the liquid charging valve should be closed, and then remove the connecting tube.
(4) Refrigeration system commissioning. After the end of the refrigerant charging (such as the need to charge refrigerant), you can carry out load debugging. As in recent years, screw-type chiller in terms of performance and electrical control have made great progress, many screw-type chiller in the official start-up before the main electrical control system can do simulation action check side, that is, the unit host is not energized, the control system is energized, and then through the unit's internal settings, the unit's electronic control system to detect whether the components are operating normally. If there is any problem with the electronic control system, it can be solved in time. Finally, the host is powered on again for debugging. In the commissioning process, special attention should be paid to the following points:
1) Check whether the valves in the refrigeration system are in a 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, and the flow rate of cold water and cooling water should meet the requirements put forward by the factory. 3）Before starting, observe whether the supply voltage of the unit is normal or not. 4) Start the unit according to the start-up manual provided by the factory.
5) When 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 factory-provided screw-type chiller unit operation data record sheet, the screw-type chiller unit's various data records, especially some of the main parameters must be recorded clearly.
7) In the process of screw-type chiller operation, should pay attention to the compressor on the download mechanism is working properly.
8) should be the correct use of refrigeration systems installed in the safety protection devices, such as high and low pressure protection devices, cold water and cooling water disconnect flow switch, safety valves and other equipment, if any damage should be replaced in a timely manner.
9) Screw chiller should be stopped immediately for inspection if there is any abnormality. Before the commissioning of the refrigeration system, be sure to do a good job of cleaning and drying the inside of the air conditioning system. If the preliminary work is not carried out carefully, during the commissioning will increase the workload, and will bring many hidden dangers to the future operation of the refrigeration unit. (B) screw chiller start-up operation
Screw refrigeration compressor after trial operation, and the discovery of the problem to deal with, you can enter the normal operation of the operating procedures. The operation method is:
(1) confirm that the unit in the state of the relevant valves in line with the boot requirements.
(2) supply power to the unit electrical control device, and open the power switch, so that the power control indicator light. (3) Start the cooling water pump, cooling tower fan and refrigerant water pump, you should be able to see the three running indicator light on.
(4) Detect whether the lubricant oil temperature reaches 30 ℃. If less than 30 ℃, it should open the electric heater for heating, at the same time, you can start the oil pump, so that the lubricating oil circulating temperature rises evenly.
( 5 ) After the oil pump starts running, the energy regulating control valve is in the load shedding position, and make sure the slide valve is in zero position. ( 6 ) adjust the oil pressure control valve. Make the oil pressure to 0.5 ~ O.6MPa.
(7) close the compressor power supply, start the control switch, open the compressor suction valve, after a delay, the compressor starts running, after the compressor is running to adjust the lubricating oil pressure, so that it is higher than the exhaust pressure of 0.15 ~ 0.3 MPa. (8) close the solenoid valve in the liquid supply pipeline control circuit, start the solenoid valve. Supply liquid refrigerant to the evaporator, put the energy regulating device in the loading position, and increase the load step by step over time. At the same time to observe the suction pressure, by adjusting the expansion valve, so that the suction pressure stabilized at 0.36 ~ O.56MPa .
(9) after the compressor is running, when the lubricating oil temperature reaches 45 ℃ disconnect the power supply of the electric heater, and at the same time open the inlet and outlet valves of the cooling water of the oil cooler, so that the compressor is running, the oil temperature is controlled within the range of 40 ~ 55 ℃. ( 10 ) If the cooling water temperature is low, you can temporarily turn off the cooling tower fan.
(11) will open the injection valve 1 / 2 ~ 1 turn, at the same time should make the suction chauffeur and the unit's outlet valve in the fully open position.
(12) Adjust the energy regulator to the 100% position, and adjust the expansion valve to keep the suction superheat above 6 ℃.
( 13) Screw chiller startup operation check. After the unit is started and put into operation, attention should be paid to the following contents of the inspection to ensure the safe operation of the unit.
1) refrigerant water pump, cooling water pump, cooling tower fan running sound, vibration, pump outlet pressure, water temperature and other indicators are within normal operating parameters.
2) whether the oil temperature of the lubricant is below 60 ℃, whether the oil pressure is higher than the exhaust pressure 0.15 ~ O.3MPa, whether the oil level is normal. 3）When the compressor is running at full load, whether the suction pressure is within the range of 0.36～0.56MPa. (4) Whether the compressor exhaust pressure is below 1.55MPa, exhaust temperature is below 100 ℃.
5) screw chiller compressor operation, the motor running current is within the prescribed range. If the current is too large, it should be adjusted to run at reduced load to prevent the motor from burning due to excessive running current. (6) compressor running sound, vibration is normal.
All of the above, if you find that there is an abnormal situation, you should immediately stop, find out the reasons, troubleshooting, and then restart the unit. Do not let the screw chiller run with the problem, so as not to cause major accidents. (C) screw chiller compressor signs of normal operation Screw refrigeration compressor signs of normal operation:
(1) compressor discharge pressure of 1.8 ~ 1.47MPa (gauge pressure);
(2) compressor discharge temperature of 45 ~ 90 ℃, the maximum shall not exceed 1.05 ℃; (3) the compressor oil temperature of 40 ~ 55 ℃ or so;
(4) compressor oil pressure of 0.2 ~ 0.3MPa (gauge pressure);
(5) compressor sound during operation should be uniform, smooth, no abnormal sound;
(6) the unit's condensing temperature should be higher than the temperature of the cooling water 3 ~ 5 ℃; the cold pole, the temperature should generally be controlled at 40 ℃ or so, the condenser feed temperature should be 32 ℃ the following; (7) the unit's evaporating temperature should be higher than the temperature of the refrigerant water;
(7) the unit's evaporating temperature should be higher than the temperature of the refrigerant water. (7) The evaporation temperature of the unit should be lower than the temperature of the refrigerant water outlet 3 to 4 ℃, the temperature of the refrigerant water outlet is generally about 5 to 7 ℃.
(D) screw refrigeration compressor shutdown
Screw refrigeration compressor shutdown is divided into normal shutdown, emergency shutdown, automatic shutdown and long-term shutdown and other shutdown methods. 1. Normal shutdown operation
(l) the manual unloading control device in the load reduction position.
(2) Close the solenoid valve and liquid outlet valve on the liquid supply line between the condenser and the Yanfan. (3) Stop the compressor operation and close its suction valve at the same time. (4) Stop the oil pump operation after the energy load reduction to zero. (5) Place the energy regulator in the "stop" position. (6) Close the cooling water inlet valve of the oil cooler. (7) Stop the cooling water pump and cooling tower fan. (8) Stop the operation of refrigerant water pump. (9) Turn off the main power supply. 2. Emergency unit shutdown
Screw refrigeration compressor in the normal course of operation, such as the development of abnormalities; in order to protect the safety of the unit, it should be implemented emergency shutdown. The operation method is: ( 1 ) stop the compressor operation.
( 2) close the compressor suction valve.
( 3) Close the solenoid valve on the liquid supply pipe of the unit and the liquid discharge valve of the condenser. ( 4 ) Stop the oil pump.
( 5 ) Close the cooling water inlet valve of the oil cooler.
(6) Stop refrigerant water pump, cooling water pump and cooling tower fan. (7) Cut off the main power supply.
The unit in the operation process of power failure, water failure and other faults in the shutdown method can refer to the centrifugal compressor emergency shutdown in the relevant content of the treatment.
After the emergency shutdown of the unit, the cause of the failure should be identified in a timely manner, and after removing the fault, the unit can be restarted in accordance with the normal start-up method.
3. Automatic unit shutdown
Screw refrigeration compressor in operation, if the unit pressure, temperature value exceeds the prescribed range, the unit control system in the protective device will play a role in automatically stopping the compressor, this phenomenon is known as the unit's automatic shutdown. Unit automatic shutdown, the unit's electrical control board on the corresponding fault indicator will light up to indicate the occurrence of fault parts. When such a situation occurs, after the host shutdown, other parts of the shutdown operation can be handled in accordance with the emergency shutdown method. After the completion of the shutdown operation, the unit should be checked, to be eliminated after the fault can be restarted according to the normal startup procedures. 4. Long-term shutdown of the unit
Screw refrigeration compressor for central air-conditioning cold source is seasonal operation, so the unit's downtime is longer. In order to ensure the safety of the unit, in the seasonal shutdown, the following method of shutdown operation can be carried out.
(l) During normal operation of the unit, close the outlet valve of the unit to enable the unit to perform load-shedding operation and pump all the refrigerant in the unit to the condenser. In order that the unit will not be shut down due to low suction pressure, the setting value of the low pressure relay can be adjusted to 0.15MPa . When the suction pressure drops to about 0.15MPa, the compressor stops, and when the compressor stops, the low pressure value can be adjusted back again. ( 2) will stop running after the oil cooler, condenser, evaporator in the water unloading, and put clean residual water, in order to prevent the winter freeze its internal heat transfer tube.
( 3) Close the relevant valves in the unit and check for leakage.
( 4) every week should start the lubricating oil pump running 10 ~ 20min, so that the lubricating oil can be long-term uniform distribution to the compressor within the various working surfaces, to prevent the unit due to long-term shutdown caused by the lack of oil on the surface of the parts, resulting in re-opening difficulties. (E) screw chiller maintenance
Screw chiller maintenance of the main content, including routine maintenance and regular maintenance. Regular maintenance can ensure long-term normal operation of the unit to extend the service life of the unit, but also to save refrigeration energy. For screw-type chiller units, there should be operation records to record the operation of the unit, and it is necessary to establish maintenance technical files. Complete technical information helps to find hidden faults and take early measures to prevent the emergence of the release barrier. 1. Screw compressor
Screw compressor is a very critical component of the unit, the compressor is directly related to the stability of the unit. If the compressor failure. Because the screw compressor installation precision requirements are high, generally need to ask the factory to repair. 2. Condenser and evaporator cleaning
Water-cooled condenser cooling water because of the open loop, generally used tap water through the cooling tower cycle. When the calcium and magnesium salt content in the water is large, it is very easy to decomposition and deposition in the cooling water pipe and the formation of scale, affecting heat transfer. Scale is too thick will also make the cooling water flow cross-section narrowing, water reduction, condensing pressure rise. Therefore, when the use of cooling water quality is poor, the cooling water pipe at least once a year to clean, remove the scale and other dirt in the pipe. There are usually two ways to clean condenser water tubes:
(1) Use a specialized pipe-cleaning gun to clean the tubes. (2) Use a specialized cleaning agent cycle flushing, or filling in the cooling water, to be 24h and then replace the solution until clean. 3． Replacement of lubricating oil
After long-term use of the unit, the oil quality of the lubricating oil deteriorates, and the impurities and moisture inside the oil increase. Once the problem is found should be replaced in a timely manner, the replacement of the lubricant grade must comply with the technical information. 4． Filter drier replacement
Filter drier is to ensure that the refrigerant for normal circulation of important parts. As water and refrigerant are immiscible, if the system contains water, will greatly affect the operating efficiency of the unit, so it is very important to keep the system dry, filter drier inside the filter element must be replaced regularly. 5 ． Safety valve calibration
Screw chiller on the condenser and evaporator are pressure vessels, according to the provisions of the high-pressure end of the unit that is, the condenser body on the installation of the safety valve, once the unit is in a non-normal working environment, the safety valve can automatically relieve the pressure in order to prevent
High-pressure may be caused by the human body injury. Therefore, regular calibration of the safety valve is very important for the safety of the whole unit. 6 . Refrigerant charging:
If there is no other special reason, generally the unit will not produce a lot of leakage. If a certain amount of refrigerant leakage occurs due to improper use or after maintenance. It is necessary to re-charge the refrigerant. Charge refrigerant must pay attention to the unit using refrigerant grade.
(F) operation management and shutdown considerations
1 . Screw chiller unit operation management precautions
(1) The normal start and stop of the unit must be operated in strict accordance with the steps of the operating instructions provided by the factory. (2) During the operation of the unit, the recording of parameters should be done timely and correctly.
(3) If there is an alarm shutdown during the operation of the unit, the relevant personnel should be notified in time to check the unit. You can also contact the factory directly.
(4) unit in operation is strictly prohibited to short the water flow switch, so as not to freeze the water pipe.
(5) The machine room should be specialized staff in charge, it is strictly prohibited for idle personnel to enter the machine room and operate the unit.
(6) The machine room should be equipped with appropriate safety equipment and maintenance and testing tools, such as pressure gauges, thermometers, etc., tools should be stored in a fixed location.
2. Screw chiller shutdown precautions (1) The unit should cut off the main power switch after shutdown.
(2) If the unit is in a long-term shutdown state during the unit should be cold water, cooling water system inside all the water discharge to prevent rust and corrosion. The water chamber end cap should be sealed.
(3) The unit should be properly maintained during long-term shutdown. (4) During downtime, the unit should be fully covered to prevent accumulation of dust. (5) During the shutdown period, personnel not related to the unit should not touch the machine