Refrigerant Recovery System
Model 3600
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4.4. Liquid Push-Pull Recovery General Information
Attention:
Before attempting the following liquid push-pull recovery operations, please review this page.
It may not be possible to recover liquid refrigerant from some types of refrigeration equipment.
A scale or liquid sight glass can be used to determine when all the liquid is recovered. The unit will not pull
a vacuum using the push-pull liquid recovery operation. To finish the recovery operation, you must
proceed to vapor recovery operations.
Guidelines
If any of these conditions are present in the system being evacuated, liquid push-pull operations may not
be practical and vapor recovery operations should be performed.
•
The equipment contains less than 15 lbs. of refrigerant.
•
The equipment is a heat pump or other system with refrigerant flow that would prevent you from
isolating the liquid.
•
Equipment has an accumulator between the service ports used in the liquid recovery process.
•
Liquid refrigerant migration has occurred and the location of the liquid is unknown.
•
The refrigerant tubing design on the equipment does not allow for a solid column of liquid refrigerant
to be formed.
Direct Liquid Recovery Operations
All compressors are designed to compress gases. Normally compressors are not capable of pumping
non-compressible fluids such as liquid refrigerant, however, the 3600 has been designed with a special
head and valves that enable it to handle liquid directly. This feature makes the 3600 easier to use by
minimizing the need to monitor incoming refrigerant vapors and reduces compressor failures due to liquid
slugging.
It is important to remember that the 3600 is a compressor and not a liquid pump. When large amounts of
liquid are present, the liquid push-pull method of recovery should be used. Using the 3600 to pump large
amounts of liquid refrigerant over a long period of time will reduce the compressor life.
WARNING
: A “Knocking” sound coming from the compressor indicates too much liquid is entering the
compressor. The inlet ball valve must be regulated as shown in the shaded region until this
knocking sound stops, otherwise compressor damage could occur. Pumping liquid when the
compressor is knocking will damage the compressor and will reduce the compressor life.
This will void the compressor warranty.
A sudden slug of liquid into the compressor may cause a sudden spike in pressure and cause the high-
pressure safety shutoff switch to shut the compressor off. If this happens, you must clear the liquid from
the compressor before you can restart the compressor. To prevent this from happening, always open the
inlet valve slowly when starting a recovery job. Opening the inlet valve quickly could allow a slug of liquid
to enter the cylinder and cause the high-pressure switch to shut the system down.
