Do you know the two methods of evacuating the refrigeration system?

Do you know the two methods of evacuating the refrigeration system? Vacuuming is an indispensable important process before charging refrigerant in the production or maintenance of refrigeration equipment. The process of removing the non-condensable gas and moisture in the system pipeline by connecting the vacuum pump to the refrigeration system pipeline (generally, the high and low pressure sides are simultaneously connected) Function 1. Remove the non-condensable gas in the system: the presence of non-condensable gas will increase the system's condensing pressure and the temperature of the exhaust gas, which will affect the cooling effect; it may also cause the carbonization of the lubricating oil at high temperature, endangering the compressor's normal Run, or even burn out the compressor motor. 2. Remove moisture from the system: Moisture is the biggest killer in the refrigeration system (specifically the Freon system in the vapor compression refrigeration cycle); first, the action of lubricating oil and moisture will generate acids, which will corrode the system and cause "copper" The phenomenon of "plating" damages the compressor; at the same time, moisture can cause ice in the expansion valve or the capillary, and "ice blockage" occurs. The vacuuming operation of the refrigeration system should be carried out after the system is cleaned, drained and tested for pressure and leaks. Vacuuming can not only further check the air tightness of the system, but also exclude the air, moisture and other non-condensable gases in the system, so as to prepare the system for refrigerant charging. Vacuuming should be done with a vacuum pump. For small refrigeration systems that use medium and small open-type and semi-hermetic compressors, the vacuum of the system itself can also be used for pumping without the vacuum pump. The product manual provided by the equipment manufacturer prohibits the use of this machine for pumping Except. 1. Operation method of vacuuming with vacuum pump 1) Close the valves (such as filling valve, air vent valve, etc.) that the system communicates with the outside world, and open all the connected valves in 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 for pumping, the air in the system is difficult to exhaust, in order to achieve a certain degree of vacuum, the pumping should be carried out in fractions, with an interval of about l0min, to balance the pressure in the system. The residual pressure of the vacuum of the ammonia system should be less than 7.997kPa (60mmHg); the residual pressure of the Freon system should be less than 1.333kPa (10mmHg). 4) After the vacuum reaches the standard, first close the bypass hole, then stop the vacuum pump, and remove the exhaust pipe, screw on the exhaust valve bypass hole screw plug 5) After vacuuming, it should be maintained for 24h, and the pressure increase in the system does not exceed 666.61Pa (5mmHg) is qualified. If the pressure rises faster, the cause should be identified and eliminated in a timely manner. Second, the operation method of 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 in the system that are open to the atmosphere (such as the filling valve and the air release valve), 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 discharged, otherwise the moisture in the system will not be easily evaporated due to the low temperature of the cooling water, and it is difficult to be exhausted. 4) Force the contact between the oil pressure controller and the low-pressure controller to be normally open, start the compressor, and slowly open the suction valve after the oil pressure is normal, and place the energy adjustment device in the smallest gear. Due to the small diameter of the evacuation valve of the refrigeration compressor, the suction valve cannot be opened very large at the beginning, nor can the energy adjustment device be placed in high gear. As the pressure in the system decreases, the suction valve can be opened gradually and Gradually load, increase inspiratory volume. During the pumping process, the oil pressure of the refrigeration compressor must not be less than 50kPa. 5) The intermittent evacuation method should be used for vacuuming. When the compressor is continuously pumped until no sound of airflow is heard, the exhaust pipe is immersed in the oil cup of the refrigerator, and the bubbling situation of the pipe mouth is observed. If no bubbles emerge within 5 minutes, it can be considered that the gas in the system has been basically exhausted. If bubbles come out of the exhaust pipe for a long time, it means that the compressor itself or the system has a leak, 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 bubbles in the oil container, and it also indicates that there is a problem in the system; if the compressor leaks, the bubbles will continue to be generated, which is often caused by the shaft seal not tightly closed. If the bubble is larger at the beginning and then gradually becomes smaller, the interval between the bubbles will become longer and longer, which means that the shaft seal has never closed to gradually close. If it is found that the end of the pipe (in the case of not deep insertion) appears to be repeatedly sucked in and out of the refrigerating machine oil, the phenomenon can not be seen when the pipe end is inserted deep into the oil. This situation is generally caused by the valve disc being not tightly closed. As a result, there will be some improvement after heavy use. After evacuating the vacuum, the drain hole should be closed first, and then stopped to prevent the backflow of air due to the non-adherence of the valve pieces after shutdown. 3. Attentions 1) When the vacuum is pumped to 8.659kPa, the oil pressure of the compressor is already very low and the pumping can no longer be continued. 2) In the process of using its own compressor for vacuuming, if the compressor itself has a lubricating oil pump, the working conditions of the lubricating oil pump will deteriorate with the increase of the vacuum in the system, causing damage to the moving parts of the machine, so when the oil When the pressure (finger pressure difference) is less than 26.7kPa, stop immediately. 3) After the evacuation is completed, the compressor should be disassembled and washed, and replaced with new lubricant.

Recent related posts

Customers frequently viewed

Submitted Successfully
Submission Failed