How to safely operate the compressor in an ammonia refrigeration system

How to safely operate the compressor in an ammonia refrigeration system

Ammonia refrigeration compressor is a very important part of the refrigeration system, and it is also the main operation scope of the refrigeration workers. How to operate correctly is directly related to the safety index of the refrigeration system. The editor of okmarts.com shares with you an example of safe operating procedures for ammonia refrigeration compressors.

　　 Preparation work before turning on the ammonia refrigeration compressor:

　　 1. Check the records to understand the reason and time of the shutdown of the machine and the system. If it is an accident or parking after major repairs, it is necessary to know whether it has been delivered to use and whether the procedures are complete.

　　 2. Check whether the valves used in the system are in a state of waiting.

　　 1. The valves on the pipelines from the compressor to the oil separator, condenser, and high-pressure liquid storage tank are all opened.

　　2. The valves on the pipelines from the evaporator to the low-pressure liquid storage tank and the compressor are all opened.

　　3. Using a two-stage compressor, the steam inlet valve on the intercooler and the liquid inlet and outlet valves of the serpentine cooling coil are all opened.

　　4. The suction and exhaust valves of the machine are closed.

　　5. The pressure gauge control valve, safety valve control valve and indicator control valve on various equipment are all open. The oil drain valve of each device is closed.

　　 6. The regulating valve of the regulating station is closed.

　　 3. Inspection equipment

　　 1. The liquid level of the high-pressure liquid tank is the highest 80% and the lowest 30%.

　　2. Gravity liquid supply mode: the liquid level of the ammonia separator in the system shall not exceed 40%; the liquid supply mode of the ammonia pump: the liquid level of the low-pressure circulating liquid storage tank is maintained between 30% and 60%.

　　3. In the two-stage compression system, the liquid level of the intercooler is lower than the center line of the float valve, and the pressure of the intercooler does not exceed 0.49MPa.

　　 4. There are no obstacles around the ammonia pump to be used.

　　4. Turn on the circulating water pump to supply water to the condenser and the water jacket of the machine, and observe the water flow.

　　 5. Check the ammonia refrigeration compressor

　　 1. Make sure that the protective cover of the compressor is intact and that there are no obstacles in the compressor's operating part.

　　2. The crankcase pressure should be lower than 0.20MPa. When the pressure exceeds this pressure, the reason must be found out and the pressure should be reduced to the specified value.

　　3. The oil level of the crankcase single sight hole is not lower than 1/2 of the sight oil hole, and the oil level of the crankcase double sight hole is 1/3 of the upper sight hole.

　　4. When the machine refueling three-way valve is in the "running" or "working" position, turn the handle of the energy adjustment device to the zero position.

　　 5. Make sure that the pressure gauge valves of the machine are all open, and the pointers of the oil pressure, high and low pressure relay automatic protection device are on the set value.

　　 6. Check whether the water jacket water supply is unblocked.

　　 Six. Drive and stop under the command of the shift leader.

　　Ammonia refrigeration compressor start program

Start-up procedure of series single-stage compressor:

　　 1. Turn the handle of the oil filter to ensure the smooth flow of the oil filter. The coupling of the disc machine should be easy. If the disk does not move, find out the reason.

　　2. Open the exhaust valve of the machine.

　　3. Turn on the power and start the compressor.

　　 4. Slowly open the suction valve of the machine, and pay attention to the stable current of the ammeter. When opening the suction valve, if there is a liquid hammering sound, close the suction valve immediately, and then slowly open it again until there is no liquid hammering sound, open the suction valve completely. During the opening process, pay attention to changes in oil pressure at all times.

　　5. Adjust the oil pressure so that the oil pressure is 0.15～0.29MPa higher than the suction pressure.

　　6. ​​Watch the oil pressure gauge, and slowly move the handle of the unloading device step by step.

　　7. After the compressor is running normally, turn on the ammonia pump or the joint flow valve to supply liquid to the low-pressure system.

　　 8. Fill in relevant forms and driving records. Start-up procedure of series two-stage compressor:

　　 1. Turn the handle of the oil filter to ensure the smooth flow of the oil filter.

　　 2. Turn on the first and second exhaust valves of the machine, and move the first and second suction valves.

　　3. Turn on the power and start the compressor.

　　4. Adjust the oil pressure. The oil pressure should be 0.15～0.29MPa higher than the suction pressure.

　　 5. After the current and voltage are stable, add a set of loads (high-voltage loads). Slowly open the secondary suction valve of the compressor, and the current rises steadily at this time. If there is a liquid hammering sound, immediately close the suction valve, and then slowly open it again until there is no liquid hammering sound, fully open the suction valve.

　　 6. When slowly opening the secondary suction valve, observe the pressure change of the intercooler at any time. When the pressure is less than 0.39MPa, slowly open the first stage suction valve of the compressor (the suction pressure is not higher than 0.04MPa). Observe the operation of various instruments at any time. If there is a knocking sound from the compressor, you should quickly close the suction valve and continue to open it after the sound is eliminated until it is fully opened. Observe the oil pressure gauge, slowly shift the handle of the unloading device step by step until the compressor runs at full load.

　　7. After the machine runs normally, turn on the ammonia pump or a joint flow valve to supply liquid to the low-pressure system.

　　 8. Fill in the relevant record form and driving record.

　　Adjustment and operation during compressor operation:

　　 The sign of normal operation of the machine:

　　1. The sound of the machine running: When the compressor is running, there should be no abnormal sound in the cylinder, crankcase and safety cover. Only the suction and exhaust valves make clear up and down sounds.

　　2. The current of the machine running: When the compressor is running, the pointer of the machine's ammeter is in a stable state when the suction and discharge pressures do not change, and there should be no large swings.

　　3. The oil pressure during the operation of the machine: keep stable between the specified values, and keep the oil level of the crankcase within the required range without foaming.

4. The temperature of the machine during operation: the temperature of each part should be kept within the specified value; the highest oil temperature should not exceed 70℃, and the lowest should not be lower than 5℃; the compressor body should not have local abnormal temperature rise, and the bearing temperature should not exceed High; the temperature of the sealer should not exceed 70°C.

　　 5. The temperature difference between the cooling water inlet and outlet of the machine is 3～5℃.

　　 6. The normal oil dripping rate of the machine sealer is 1 to 2 drops/min.

　　7. The operation of the machine is coordinated with the work of the entire system. That is, the suction temperature of the machine is 5-15°C higher than the evaporation temperature, and the exhaust temperature of the machine does not exceed 150°C. The exhaust pressure of the machine should not exceed 1.47MPa, and the suction and exhaust pressure ratio of the machine should not exceed 8.

　　Adjustment operation while compressor is running:

　　 1. When the temperature difference between the compressor inlet and outlet water temperature is greater than the machine's specified cooling water inlet and outlet temperature difference, the cooling water volume should be increased slowly (it is strictly forbidden to suddenly increase the cooling water volume to prevent accidents).

　　2. When the compressor oil level is too low and the machine needs to be refueled, the personnel in the equipment room should be notified to turn on the refueling pump, and then turn the compressor's refueling three-way valve to the "refueling" position. If the crankcase pressure is high, the suction valve can be appropriately closed to reduce the pressure of the crankcase, and then the suction valve can be opened after the refueling is complete. After the refueling work is completed, notify the equipment room to stop the refueling pump, and at the same time turn the refueling three-way valve to the "working" or "running" position, and close the refueling valve.

　　3. When the compressor suction pressure is too low or too high, the cause must be found in time, measures should be taken, adjustments should be made, and the machine should be stopped if necessary.

　　4. When the exhaust temperature of the two-stage compressor is too high, judge whether the intercooler supply is insufficient, if so, the intercooler should be supplied with liquid in time.

　　5. If the machine still cannot operate normally by adjusting the operating state of the machine, stop immediately and find out the reason.

　　 The normal shutdown operation of a single-stage compressor:

　　 1. Reduce the number of working cylinders of the compressor to "0" position by gear, and close the suction valve.

　　2. Cut off the power supply and close the exhaust valve of the compressor while the compressor stops running.

　　 3. After parking for 5-10 minutes, close the water jacket water supply valve.

　　4. Fill out the relevant forms and make a record of parking.

　　 The normal shutdown operation of the two-stage compressor:

　　 1. Reduce the number of working cylinders of the low pressure cylinder step by step, close the first-stage suction valve, and close the second-stage suction valve when the intermediate pressure drops to 0.20MPa.

　　2, cut off the power, and close the first and second vent valves at the same time.

　　 3. After parking for 5-10 minutes, close the water jacket water supply valve.

　　4. If it is stopped for a long time, the ammonia in the intercooler must be drained.

　　 5. Fill out the relevant forms and make a record of parking.

　　 If the entire system stops working, the main liquid supply valve and system liquid supply valve on the regulating station must be closed before stopping the compressor, and the operation of the ammonia pump must be stopped (the liquid supply to the low-pressure circulation barrel must be stopped before the pump is stopped). After the compressor stopped running for 10 minutes, stop the water pump. When parking or stopping the pump in winter, the remaining water in the equipment such as the machine water jacket and the pipeline must be drained to prevent the equipment from freezing and cracking.

　　 Ammonia refrigeration compressor special operation operation:

　　The adjustment of the wet stroke of the compressor

　　 1. If the following conditions are found during compressor operation, the operator must take immediate measures.

　　(1) The suction temperature of the machine drops rapidly.

　　(2) The exhaust temperature of the machine drops rapidly.

　　 (3) The machine's running sound is heavy or there is a knocking sound.

　　(4) The suction port of the machine is frosted quickly. When it is severe, the cylinder wall is frosted. When it is severe, the crankcase and exhaust pipe appear frost.

　　2. Treatment of wet stroke of single-stage compressor.

　　 (1) If a wet stroke occurs during compressor operation, the machine suction valve should be closed immediately (close the suction valve in severe cases), and the liquid supply valve should be closed at the same time.

　　(2) Unload immediately, leaving only a set of cylinders to work, and use the heat generated during the operation of the machine to melt the frost on the cylinder wall.

　　(3) When the exhaust temperature rises to 70～80℃, slowly open the suction valve. If the exhaust temperature drops, close the suction valve again and repeat the above process (items 1 and 2). 　　 (4) When the suction and exhaust temperature gradually tends to normal, increase the number of working cylinders and open the suction valve to restore normal operation of the machine.

　　(5) During the adjustment process, always pay attention to the changes in the oil pressure of the machine, and do not cause the machine to run without oil pressure.

　　 (6) When the wet stroke is severe, the machine must be stopped, but the machine cooling water must not be turned off to prevent the machine cooling system from being frozen and cracked, and increase the water jacket water supply.

　　3. Treatment of wet stroke of two-stage compressor

　　The wet stroke of the low-pressure stage is treated in the same way as the wet stroke of the single-stage compressor.

　　 The high-pressure wet stroke is mostly caused by the excessively high level of the intercooler, please operate according to the following procedure:

　　(1) Close the liquid supply valve of the intercooler.

　　(2) Close the low-pressure stage suction valve.

　　(3) Unload all the low-pressure working cylinders, leaving only the high-pressure cylinder to work, and close the high-pressure suction valve at the same time.

　　(4) When the liquid level of the intercooler drops to normal, restore the machine to normal operation.

　　(5) During the adjustment process, always pay attention to the changes in the oil pressure of the machine, and do not cause the machine to run without oil pressure.

　　 (6) During the wet stroke or after the wet stroke is severely stopped, the water jacket water supply should be increased.

　　Ammonia refrigeration compressor reverse pumping operation rules:

　　 1. Close the suction valve and exhaust valve of the machine.

　　 2. Open the anti-suction steam valve and the exhaust steam valve.

　　 3. Open the machine exhaust valve.

　　4. Turn on the power, start the machine, slowly open the machine's suction valve, and perform reverse pumping.

　　 5. After the reverse pumping work is completed, close the machine suction valve. Cut off the power and close the exhaust valve of the machine at the same time.

　　 6. Close the anti-suction steam valve and exhaust steam valve.

　　7. Turn on the suction valve and exhaust valve of the machine to restore the normal state of the system.

　　 Abnormal shutdown of ammonia refrigeration compressor:

　　 1. Sudden power failure can be operated as normal stop. After finding out the cause of the power failure, turn on the machine after handling.

　　2. Equipment general failure shutdown: carefully observe and analyze, determine the location and nature of the failure, and stop according to the normal shutdown procedure. After the overhaul is completed, turn on the machine again.

　　3, equipment shutdown due to serious failure: when equipment and pipelines have serious ammonia leakage (especially high and medium pressure systems);

　　 The machine makes an abnormal sound, and it is too late to determine the faulty part. In order to prevent the spread of the accident, it is necessary to immediately cut off the power supply and shut down, close all valves, and organize personnel for emergency repairs. After the overhaul is completed, fill in the relevant form, make a record, and then turn on the machine.