A refrigerant gas recovery machine will extract a greater quantity of refrigerant than any other employed method, so its use is recommended.
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How a refrigerant gas recovery unit works
Refrigerant gas recovery is the preliminary stage required to repair or commission air conditioning equipment. This involves transferring the gas to a recovery cylinder from the refrigeration system. If the refrigerant gas is not contaminated, it can be recharged into the refrigerant system after the repair of the air-conditioning system has been completed. If it is contaminated, it must be recycled before being reintroduced into the system.
Several refrigerant gas recovery systems are available:
Recovery of the refrigerant in liquid phase.
Recovery of the refrigerant in gas phase.
Liquid and vapour recovery without separation of the oil from the refrigerant gas. The oil ends up in the recovery cylinder as it leaves the system.
Liquid and vapour recovery, isolating the oil from the refrigerant gas.
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These systems have their advantages and disadvantages:
The first method, liquid refrigerant, is quick to perform, however, vapour remains in the system.
The second method, vapour refrigeration, although a slower process, no refrigerant is left in the system.
Recovery by isolating the oil is not always better than recovery that does not separate the oil. Some recuperators require a vacuum process before use, especially when a refrigerant change is to be made.
Steps to recover refrigerant gas
It is important to note:
The refrigerant should be poured into the recovery tank using the method recommended by the refrigerant manufacturer.
Do not overfill the cylinder.
Do not mix refrigerant gases of different strength.
Do not put refrigerant gas of one type in a cylinder labelled with another type of gas.
Use properly cleaned cylinders, free of contamination.
Check the cylinder beforehand.
Check that the cylinder has separate valves for gas and liquid, and has a pressure relief system.
Liquid phase recovery
Recovery is carried out by decanting, separation or push/pull techniques, with consequent oil transport.
The push/pull method (suction/feedback) is performed by using the vapour from the cylinder to push the liquid refrigerant gas out of the system.
The “pull” consists of sucking the liquid refrigerant out of the equipment through the recovery tank when the recovery unit reduces the pressure in the cylinder.
The “push” consists of pushing the vapour sucked out of the recovery tank by the recovery unit into the vapour zone of the equipment.
As soon as most of the refrigerant has been charged into the recovery tank, the recovery unit will start cycling, managed by the low suction pressure switch, moving the rest of the refrigerant gas in vapour state. The process will end when the recovery tank stops.
Gas phase recovery
The gas is sucked in by the recovery unit and when condensed is transferred to the recovery tank.
Liquid and vapour phase recovery
When the amount of gas to be recovered is considerable, the push/pull method should be used because it is three times more efficient than the direct method. In addition, long hoses increase the recovery time.
Recovery takes place in the vapour zone of the recovery tank, thus minimising the risk of liquid in the lines. This ensures a cleaner process. When the tubes are removed, it is possible that some coolant may leak out.
The use of a filter drier is recommended in the above processes as it serves as protection for the recovery tank, especially in cases where the system has a burnt compressor.
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