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Know more about vacuum pump of compression molding machine

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1. Tips to assembly the vacuun pump.

(1) Close the valves that the system communicates with the outside world (such as filling valves, vent valves, etc.), and open all the communicating valves inside the system.

(2) Unscrew the screw plug of the bypass hole of the exhaust valve, open the bypass hole, and connect the vacuum pump.

(3) Start the vacuum pump to pump air. It is difficult to exhaust the air in the system. In order to achieve a certain degree of vacuum, vacuum pumping must be performed several times with an interval of about 10 minutes to equalize the pressure in the system. The residual pressure of the ammonia system should be less than 7.9 kPa (60 mmHg); the residual pressure of the Freon system should be less than 1.3 kPa (10 mmHg).

(4) After the vacuum reaches the standard, close the bypass channel first, then stop the vacuum pump, remove the suction pipe, and screw on the bypass hole plug of the exhaust valve.

(5) It should be kept for 24 hours after vacuuming, and the pressure in the system should not exceed 670 Pa (5 mmHg) as qualified. If the pressure rises quickly, the cause should be identified and eliminated in time.

2. Operation method and steps for vacuuming with its own compressor

(1) Close the suction valve and exhaust valve, unscrew the screw plug of the bypass hole of the exhaust valve, install the exhaust pipe, and open the bypass hole to discharge air.

(2) Close the valves that open to atmosphere in the system (such as filling valve, vent valve, etc.), and open all other valves in the system.

(3) If the condenser of the system is a water-cooled condenser, the cooling water in the condenser should be drained. Otherwise, the water in the system will not be easy to evaporate and be exhausted due to the low cooling water temperature.

(4) Forcibly connect the contacts of the oil pressure controller and the low pressure controller, start the compressor, slowly open the suction valve after the oil pressure is normal, and place the energy regulating device in the first gear. Due to the small diameter of the discharge valve of the refrigeration compressor, the suction valve cannot be opened very large at the beginning, and the energy regulating device cannot be placed in a high gear. As the pressure in the system decreases, the large suction valve can be gradually opened and loaded gradually to increase the suction volume. During the pumping process, the oil pressure of the refrigeration compressor shall not be lower than 50 kPa.

(5) Intermittent evacuation should be used for vacuuming. When the compressor continues to pump air until no airflow sound is heard, immerse the exhaust pipe in the refrigerator oil cup and observe the bubbling at the nozzle. If no bubbles emerge within 5 minutes, it can be considered that the gas in the system has been basically exhausted. If there are bubbles coming out of the exhaust pipe port for a long time, it means that the compressor itself or the system is leaking, which should be checked and eliminated. When checking, first close the suction valve of the compressor to check whether the compressor itself leaks. If the compressor does not leak, there will be no air bubbles in the oil container, which also means that there is a fault in the system; if the compressor leaks, air bubbles will continue to be generated, which is often caused by a leaky shaft seal. If the bubbles are large at the beginning and then gradually become smaller, the time interval between the appearance of the bubbles will become longer and longer, which means that the shaft seal has never been tightly sealed to gradually sealed. If you find that the pipe end (when the insertion surface is not deep) has the phenomenon of repeatedly sucking in and out of the refrigerating machine oil, you will not see this phenomenon when the pipe end is inserted deep into the oil. It is generally caused by the valve disc not being tight. It will get better after heavy use.