A screw refrigeration unit before the start of the preparatory work
Refrigeration unit of the correct commissioning of the refrigeration unit is to ensure the normal operation of refrigeration installations to save energy and extend 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, understanding of the shape and structure of each device and component performance, as well as the electronic control system and water supply system. 1, the commissioning of the preparation
1) check whether the installation of the unit meets the technical requirements, whether the unit's foundation meets the requirements, connecting pipeline size, specification, material is in line with the design requirements. 2) Check whether the power supply system of the unit is normal.
3) The cold water and cooling water system only water test, flush the water system of dirt, the pump should work normally, the amount of circulating water in line with the requirements of the working conditions.
4) check whether the pressure gauge, thermometer, sensor on the pipeline is normal, 5) check whether the water pressure in the pipeline is normal, 6) ready to run the necessary safety protection equipment. 2, unit commissioning
1) check the refrigeration system in the various valves are in a normal open state, especially the exhaust valve, do not close.
2) Open the condenser cooling water valve and evaporator cold water valve, cold water and cooling water flow should be in line with the factory requirements.
3) 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 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 unit operation data record sheet provided by the factory, record the data of the unit, especially some major parameters must be recorded clearly.
7) During the operation of the unit, attention should be paid to the compressor on the download mechanism is working properly. (8) should be correctly used in the refrigeration system installed in the safety protection devices, such as high and low pressure protection device, cold water and cooling water cut-off flow switch, safety valve and other equipment, if damaged should be replaced in a timely manner. (9) The unit should be shut down immediately for inspection if any abnormality occurs.
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.
Two, screw refrigeration unit start-up operation
Screw refrigeration compressor after test run operation, and the discovery of the interproblems 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 valve is in line with the requirements of the boot.
(2) to the unit electrical control device power supply, 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 ℃, you should open the electric heater for heating, and at the same time, you can start the oil pump, so that the lubricating oil circulation temperature rises evenly.
(5) After the oil pump start operation, the energy regulation control valve 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 compressor start operation, after the compressor operation for lubricant pressure adjustment, so that it is higher than the exhaust pressure of 0.15 ~ 0.3 MPa.
(8) Closing the solenoid valve control circuit in the liquid supply pipeline, start the solenoid valve. Supply liquid refrigerant to the evaporator, place the energy regulator in the loading position, and over time, step by step loading. 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, disconnect the power supply of the electric heater when the lubricating oil temperature reaches 45 ℃, and at the same time open the inlet and outlet valves of the cooling water of the oil cooler, so that during the compressor operation, the oil temperature is controlled within the range of 40 to 55 ℃.
(10) If the cooling water temperature is low, you can temporarily turn off the cooling tower fan.
(11) Open the injection valve to 1 / 2 ~ 1 turn, at the same time should make the suction continent and the unit's liquid discharge valve in the full open position. (12) Adjust the energy regulator to the 100% position, and at the same time adjust the expansion valve to keep the suction superheat above 6 ℃.
(13) unit 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.
(14) chilled water pumps, cooling water pumps, cooling tower fan running sound, vibration, pump outlet pressure, water temperature and other indicators are within normal operating parameters.
(15) lubricant oil temperature is below 60 ℃, oil pressure is higher than the exhaust pressure 0.15 ~ O.3MPa, oil level is normal.
(16) When the compressor is running at full load, whether the suction pressure is within 0.36～0.56MPa.
(17) whether the compressor exhaust pressure is below 1.55MPa, exhaust temperature is below 100 ℃. (18) During compressor operation, whether the motor running current is within the specified 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. (19) compressor running sound, vibration is normal.
If any of the above items are found to be abnormal, the unit should be shut down immediately to find out the cause, remove the fault, and then restart the unit. Do not let the unit run with the problem, so as not to cause major accidents. Third, the screw refrigeration compressor shutdown operation
Screw refrigeration compressor shutdown is divided into normal shutdown, emergency shutdown, automatic shutdown and long-term shutdown and other shutdown.
1. Normal shutdown operation
(l) will be manually unloading the control device is placed in the position of load shedding.
(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 stop of the unit
Screw refrigeration compressor in the normal course of operation, such as the occurrence of abnormalities; in order to protect the safety of the unit, it should be implemented emergency stop. The method of operation is: (1) stop the compressor operation. (2) close the compressor suction valve.
(3) Close the solenoid valve on the unit's liquid supply pipe and the condenser's liquid discharge valve. (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 of the 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, after eliminating the fault, the unit can be restarted according to the normal starting 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 protection device will play a role in automatically stopping the compressor work, this phenomenon is called 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 methods 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 shut down due to low suction pressure.
(2) Remove the water from the oil cooler, condenser, and evaporator after stopping operation, and drain the residual water to prevent freezing of its internal heat transfer tubes in winter.
(3) Close the relevant valves in the unit and check for leakage.
(4) every week should start the lubricating oil pump running 10 ~ 20min, in order to make 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 reboot difficulties.
Four, 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 consumption. 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 to help find hidden trouble, take early measures to prevent the emergence of the release of the 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 due to the open loop, generally used by the tap water through the cooling tower cycle
use. 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) using a specialized cleaning agent cycle flushing, or filling in the cooling water, to be 24h and then replace the solution until clean. 3, the replacement of lubricating oil
The unit in long-term use, the lubricant oil quality deterioration, the oil inside the impurities and moisture increase, so we must regularly observe and check the oil quality. Once found that the problem 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, the calibration of the safety valve
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 to prevent high-pressure may be harmful to the human body. Therefore, the 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, the general unit will not produce a lot of leakage. If due to improper use or after maintenance, a certain amount of refrigerant leakage. It is necessary to re-charge the refrigerant. Charge refrigerant must pay attention to the unit using refrigerant grade. V. Operation management and shutdown precautions 1 . Screw chiller operation management precautions
(1) the normal start, stop, must be strictly in 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 the operation of the water flow switch is strictly prohibited short, so as to avoid freezing water pipes.
(5) the machine room should be specialized staff responsible for, strictly prohibit idle personnel into the machine room, operation of 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 The 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, should be cold water, cooling water system inside all the water discharge to prevent rust and corrosion. The water chamber end cover 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.