The system vacuum requirement of small refrigeration and air conditioning devices is relatively high, and the absolute pressure of residual air in the system is required to be below 133Pa. The methods of vacuum extraction include: low-pressure side vacuum extraction, secondary vacuum extraction, duplex air exhaust method and high-low pressure double-side vacuum extraction, etc.
1. Low-pressure overhaul vacuum
1. Low-pressure side vacuum evacuation is to use vacuum pump to evacuate the process tube on compressor or the process tube set on the return air pipe.
2. This method is simple to operate, has few welding points, and the possibility of leakage is relatively small. The disadvantage is that the air on the high-pressure side of the system needs to be extracted through the capillary . Due to the large resistance of the capillary, when the absolute pressure of the air in the low-pressure side reaches below 133Pa, the absolute pressure of the residual air on the high-pressure side is still high. Therefore, the vacuuming time is required to be longer.
Secondary vacuum
Low-pressure vacuum
It is difficult to make the refrigeration system meet the requirements of vacuum degree. Therefore, the system can be evacuated to a certain vacuum degree, stop the vacuum pump, and then refrigerant is charged to the system and the internal pressure of the system will be raised to the same as atmospheric pressure. At this time, turn on the compressor and run for a few minutes, so that the residual air in the system will be mixed with the working fluid, stop the compressor, and turn on the vacuum pump for a second vacuum. Although it is still difficult to meet the vacuum requirement on the high-pressure side, compared with the vacuum evacuation on the low-pressure side, the system is left with a mixed gas of refrigerant and air, reducing the amount of air remaining in the system.
3. Complex air exhaust method
1. The purpose of vacuuming is mainly to reduce the air and water vapor content in the system. If there is no vacuum pump, the duplex air exhaust method can be used, that is, the system is filled with people and discharged refrigerant multiple times. Each time the refrigerant is charged, the gauge pressure reaches 0.2MPa, stop charging and wait for 5 minutes, and then discharge the refrigerant until the gauge pressure is zero, and repeat it several times. The disadvantage of this method is that it consumes a lot of refrigerant and pollutes the environment. When installing
2 and split air conditioner , when the indoor unit and outdoor unit are connected to with pipes, the indoor unit and the connecting pipe should be exhausted. First, tighten the connectors at both ends of the liquid supply pipe (slim tube) and the return pipe (coarse tube), then loosen the nuts of the cutoff inflatable port on the return pipe, open the shutdown valve on the liquid supply pipe, and the refrigerant flows into the pipeline from the condenser , and connect the indoor unit to the connecting pipe.
3. Air is discharged through the inflation port on the return air pipe shut-off valve.
4. Vacuum vacuum on both sides of high and low pressure
1. Vacuum vacuum on both sides of high and low pressure is to use a vacuum pump to evacuate the vacuum on both sides of the system at the same time.
2. Use a vacuum pump to evacuate the process tube of drying filter and the process tube of the compressor at the same time.
3. Use pressure-resistant hose to connect the process tube of the drying filter and the process tube of the compressor to the duplex repair valve, and connect the common joint of the duplex repair valve to the vacuum pump through the pressure-resistant hose.
4. When vacuuming, just open the two valves on the left and right of the duplex repair valve and turn on the vacuum pump to vacuum the system. The advantage of this method is that the vacuuming speed is fast, and both high and low pressure sides can meet the vacuum requirements, but it is only suitable for systems with process tubes on both the high and low pressure sides.
Shanshang Refrigeration Equipment specializes in the production of cooler , condenser, refrigeration unit, bucket pump unit, screw parallel unit, evaporation and refrigeration. The products are widely used in various industries such as food processing, refrigeration, medical care, chemical industry, cold chain logistics and other industries. We are committed to providing customers with efficient, safe and reliable products, and to formulate complete and flexible solutions and services.
