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Refrigeration system blowdown

  • 2020-11-12

The cold storage refrigeration system should be a clean, dry and tight closed circulation system. What if there are mechanical impurities or other contaminants in the system?


Here are the impacts on the device:

1. Accelerate the wear of the friction surface, and if it is serious, it may cause the cylinder to damage the machine;

2. Affecting the sealing performance of the valve seat of the suction and exhaust valve, so that the exhaust pressure of the compressor is lowered and the suction pressure is increased;

3, may cause some of the narrower pipe fittings such as thermal expansion valves, capillaries and strainers, etc., affecting the normal flow of refrigerant, and thus affect the refrigeration capacity of the refrigerator. Therefore, mechanical impurities or other contaminants are not allowed in the system, and the system must be cleaned after installation.


The mechanical impurities and other contaminants in the refrigeration system are derived from iron filings, welding slag, scale, sand, rust and other impurities caused by equipment and piping during manufacturing, construction, installation and maintenance.


For small refrigeration systems, the basic method of cleaning up is to first disconnect the compressor from the other parts of the refrigeration system, then depressurize the high pressure nitrogen through the pressure reducing valve to 0.5 ~ 0.6MP and then connect to the condenser inlet for purging . Under the action of air pressure, the nitrogen gas is swept through the entire refrigeration system except the compressor in the direction of the original refrigerant circulation. The length of the purge time should be determined on a case-by-case basis.

For larger systems, in order to reduce gas flow resistance and gas flow, the cleaning operation can be carried out in stages. The sewage outlet should be set at the lowest point of each cleaning section, and the sewage discharge can be repeated several times until the gas discharged from the sewage outlet is blown on the white paper or the white cloth without obvious stain, the system can be considered to have been blown clean. If a solenoid valve is installed in the system, try to open the solenoid valve when blowing. If the compressed air of the compressor itself is used for blowing, the exhaust temperature of the compressor should not exceed 130 °C. Otherwise, the blowdown must be intermittent. Before the blown, the trichloroethylene solution may be added to the relevant parts to dissolve and discharge the oil, and then the oil is dissolved before being blown.

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