Refrigerant Recovery

Refrigerant recovery equipment has evolved from heavy, slow, complex pieces of equipment, to equipment that is light, fast, and user-friendly.

Today, most equipment uses oil-less compressors rather than the hermetic compressors of the past. Oil-less compressor technology offers many advantages: better recovery rates, direct liquid recovery, elimination of oil maintenance, and the capability to handle multiple refrigerants.

Refrigerant recovery can take place at any one of three stages during the lifecycle of refrigeration equipment:

• during servicing, when a partial or complete refrigerant charge is removed from the system
• when the system is converted to run with a new refrigerant
• before disposing of the equipment.

Of the three stages, conversion is rare in a system's lifetime, mainly because the system can still be run even after a refrigerant becomes obsolete due to regulation. The large refrigerant charges and the premium demanded for some refrigerant have been positive incentives for recovery.

Understand the System
Whether you're working on a supermarket application with multiple compressors connected in parallel, or a restaurant walk-in freezer, the more you know about the system beforehand, the better prepared you'll be for the job.

Before getting started, first identify the refrigerant type and quantity in the system you're servicing. When recovering refrigerant from a system that has a burned-out compressor, you'll need to use extra filtration prior to recover,y to deal with any potential contamination in the oil.

If you know the gas in the system is relatively clean or new, you should use a new tank. This will make it easy if you plan to put the refrigerant back into the same system. It is recommended you own at least one tank for each refrigerant type you service, plus extra tanks for burnouts and other unknowns.

Knowing the quantity of refrigerant is important for planning storage requirements, as well as planning for the actual recovery. A substantial amount of vapor can remain in the system after all the liquid is removed. For instance, an average 350 ton R-11 chiller at 0 psig still contains 100 lbs. of vapor after all the liquid has been removed. In cases like this one, a heater on the recovery vessel side will help to evacuate the vapor faster than if you didn't have a heater.

Hoses & Valves
Hoses and Schraeder valves have a large impact on recovery speed. Generally, the larger the hose, the less friction on the flow of refrigerant, and the quicker the recovery time. Many contractors and technicians are now using 3/8-in. lines for the input to the recovery machine, even if those lines originate out of 1/4-in. fittings.

Use the shortest hose possible. The longer the suction hose and the smaller in diameter it is, the higher the pressure drop in the system, and the longer it will take to recover refrigerants.

Remove Schraeder valves from the connection prior to a recovery. Most wholesalers sell a tool for removing these cores, while keeping the connections sealed. Be sure to remove the Schraeder valves and core depressors before every recovery job.

One last hose consideration is the little rubber grommet at the end of the hose that makes a seal with the flare fitting. Over time, these seals wear and become deformed. There are times when these seals are so worn and deformed that when the hose is connected to the flare fitting, the grommet virtually seals off the connection. This situation never gets noticed during charging, because the pressure opens the grommet, but during recovery (or with suction) the deformed grommet severely restricts the flow of refrigerant. Make the recovery machine's job easier by using larger hoses with no restrictions, and you will be rewarded with a quick recovery job.

Keep the Dirt Out
During the recovery process, your recovery machine can be exposed to debris that can cause damage internally — brazing spatter, copper/ brass slithers and acid contamination that may be in the system. Therefore, always use an inline filter at the inlet port. All manufacturers recommend using a new filter on every recovery job.

If you follow this simple practice, and use the appropriate filter on every job, your refrigerant recovery machine should give you many years of trouble-free performance.

Recovery Methods Described
The key to a quick recovery procedure is to get the liquid out first, and then get the remaining vapor out. There are three different ways to remove refrigerant from the system: push-pull recovery, liquid recovery, and vapor recovery, which is the most common.

Push-pull Recovery. Push-pull is a method of removing bulk liquid from a system by using the pressure differential created by the recovery machine. Push-pull is commonly used on systems with a receiver tank, those with greater than 20 lbs. of refrigerant, or when transferring from one tank to another. Push-pull will generally not work on smaller systems, as there is no bulk liquid reservoir from which to create a siphon.