Screw compressor
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I would like to ask: Why is it necessary to evacuate air from a screw refrigeration compressor when it is first started up or after maintenance? What is the purpose of evacuating air? !
Screw compressors shouldn’t have this issue; screw compressors in replacement systems come equipped with separate nitrogen filling tubes. I think it’s done before starting up the machine to test its sealing performance
1. Sealing performance of the test system 2. Ensuring sufficient purity of ammonia after filling it
I really haven’t thought about this issue properly
I think it’s mainly to prevent air from entering the compressor cylinder, as the oxygen in the air can oxidize the walls of the compressor cylinder.
Vacuuming is done to ensure the purity of the medium added, which is better for the efficient operation of the compressor as well as for the precision of the mixing between that medium and the compressor oil!
To remove the non-condensable gases from the system, as refrigerants can be compressed and condensed, whereas air cannot be condensed by refrigeration compressors; moreover, its oxygen content poses a significant explosion risk. We evacuate the system to remove oxygen from it; a concentration of less than 0.3% is considered acceptable. After that, N2 is introduced to displace the remaining gases, with the concentration of non-condensable gases having to be less than 2%
1. Check the system’s airtightness to prevent refrigerant leakage； 2. Remove non-condensable air and moisture from the system. Ensure the effective condensation of the condenser and prevent ice blockage in the system at low temperatures
It is necessary to remove the air and moisture that remain in the equipment after maintenance and opening. If ammonia is used, the presence of air increases the condensation pressure and reduces the cooling efficiency; moreover, the moisture in the air corrodes steel when it comes into contact with ammonia； Using fluorine – the presence of air increases the condensation pressure, reducing cooling efficiency; moreover, moisture in the air can easily cause ice blockages