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.
Before using the push-pull recovery method, make sure the system does not have a heat pump or a reversing valve, will allow a solid column of liquid to form, or does not have an accumulator. If any of these components exist within the system, the push-pull method can't be used. You will need to use a liquid or vapor recovery method.
Liquid recovery. With the advent of oil-less compressors and constant pressure regulator valves, liquid recovery has become the preferred method of recovery and recommended by most recovery equipment manufacturers. Liquid recovery is performed the same way as standard vapor recovery. The only difference is that you will connect to the high side of the system. Recovering liquid is ideal for recovering large amounts of refrigerant like refrigerant transfer, or if the system you are servicing will allow you to recover liquid.
After completing the transfer of liquid refrigerant between a recovery unit and a refrigeration system, avoid trapping liquid refrigerant between the service valves.
Vapor recovery: During vapor recovery, an additional hose must be attached between the storage tank and the recovery unit. Vapor is drawn from the refrigeration unit into the recovery system. It passes through the compressor to the condenser, where cooling occurs. Once cooled to a sufficient temperature, the gas turns to liquid and proceeds into the storage tank. Refrigerant recovery systems operate on a temperature pressure relationship. A lower temperature facilitates a lower pressure, allowing for fast, efficient operation.
Vapor recovery is approximately 75 to 80% of the recovery process, so it's important to use a recovery machine with a high vapor recovery rate.
Recovering Refrigerant
Before using a recovery unit you should always: check the positions of the service valve, evacuate and recover any remaining refrigerant from the unit's receiver, and evacuate an empty recovery cylinder prior to transferring refrigerant to the cylinder.
Many technicians prefer to have a digital refrigerant scale for keeping track of the refrigerant. This is recommended, for your own service records, and it will help in the event of an EPA audit request.
Recovering large amounts of liquid refrigerant can sometimes involve large amounts of oil if the system lacks an adequate oil separator. If this recovered refrigerant isn't going to be liquid-charged back into the same system, you might want to separate the refrigerant from the oil to measure the oil. That way, you'll know how much oil to charge back into the system.
When working on a system that has parallel compressors, you must remember to isolate a parallel compressor system in order to recover refrigerant. Failure to do so will cause an open equalization connection that will prevent refrigerant recovery.
Liquid can often become trapped in the refrigeration system. A good indicator of trapped liquid in a system is frost or condensation forming on the components where the liquid is trapped. If you are unable to locate the trapped liquid, but you know it's there because the recovery job is taking "forever,"then turn on the system compressor (if it's operable) for a few seconds. This will get the refrigerant moving to another part of the system and in the process pick up enough heat to boil off.
Another trick is to cool the tank, if it's partially filled, prior to or during recovery. This operation will lower the pressure in the storage tank, and therefore speed up recovery. There must be a minimum of 5 lbs. of liquid refrigerant in the tank you wish to chill. There's no magic here; you're simply using your recovery machine to make a refrigerator, where the tank is the evaporator. Five to 10 minutes of chilling produces some very dramatic tank cooling, depending on conditions. The greater the quantity of refrigerant in the tank, the longer the process will take.
Finishing the Job
After the refrigerant has been removed, and before the system is ready to receive the new refrigerant, use a vacuum pump to remove moisture and air from the system. Systems today are built tighter, so accurate charges become critical. This means these systems have a greater sensitivity to moisture and other contaminants, making thorough evacuation very important.
Most systems are not "recovery-friendly." Many lack access ports at their lowest points. Significant time can be saved, especially on maintenance contracts, by simply installing access ports at all of the lowest points in the system, where liquid is likely to accumulate. Since most systems lack such ports, you need to be prepared to boil off the trapped liquid with a heat gun.
If you're using your recovery equipment to recover multiple refrigerants, remember to purge the recovery equipment. Most new equipment includes automatic purge features, which clear out the machine, and prepare the equipment for the next job.
Safety First
Safety is always a concern when recovering refrigerant. Always wear safety glasses and gloves to keep debris from getting into your eyes and to prevent frostbite on your hands. Understand the system you're working on, and adequately prepare by using the right tools for the job, and the recovery process will go much faster and more trouble-free than you think.
| For Mechanical Contractors: Refrigerant Reclamation Q&A Why use a refrigerant reclamation company? Why not just What does the reclamation procedure consist of? The refrigerant is distilled, filtered, dried, and finally tested to verify that it meets ARI standards. Once it's confirmed that it meets or exceeds ARI standards, it's packaged, or stored for packaging at a later date. It sounds simple, however, it's difficult to process 10,000 to 30,000 lbs. everyday, to handle 10 different refrigerant types simultaneously, to pass ARI standards every time, and to properly account for it to the customer and the EPA. How do the contractor and refrigerant reclaimer work together? Established reclaimers provide specialized services the mechanical contractor can't, or doesn't want to provide. Established reclaimers normally have an inventory of empty Department of Transportation (DOT) cylinders available for the mechanical contractor to use, or they can send their own technicians out to physically recover the used refrigerant as a subcontractor. If the used refrigerant isn't going to be returned to the existing system, the reclaimer will normally purchase the used gas, at a negotiated price. If the recovered gas is going to be returned to the same system, a few of the larger reclaimers can process the used refrigerants on-site to remove contaminants and greatly improve the performance of the system. What does the reclaimer do with the used refrigerant? After the refrigerant is weighed, processed, and tested to verify that it meets or exceeds ARI standards, it's packaged into new cylinders or drums for resale. How does one find a reclaimer? Visit www.epa.gov and search for refrigerant reclaimers. However, some refrigerant reclaimers have been around for many years and have learned how to do it right, and some have not. Some are well funded, and others are barely scraping by. The best advice is to ask around. Most of the larger reclaimers in the U.S., such as CFC Refimax, Smyrna, GA use some type of proprietary equipment. There are systems that only reclaim higher pressure refrigerants, and systems that deal with low pressure gases. More advanced systems, which are able to process both high and low pressure refrigerants, have been built in the last few years. Many reclamation companies can recover the refrigerant and reclaim the product. This enables the mechanical contractor to partner with the reclamation company along with their proprietary equipment, which allows the mechanical to utililize his technicians for mechanical repairs. There are a few reclamation companies whose equipment enables them to reclaim the refrigerant as well as recover it at the jobsite. This procedure is important if a system has contamination and needs flushing, or the refrigerant needs to be reclaimed and reintroduced into the system in a short period of time. What questions should I ask a reclaimer? Sidebar authors: Ken Beringer is senior vice president, refrigerants, CFC Refimax, Smyrna, GA. Doug Romine is senior vice president, business development with Airgas, Inc. Airgas, an industrial gas company, purchased CFC Refimax as of January. 1. |
Tim Wagaman is product manager for air conditioning tools and equipment for SPX Service Solutions, Owatonna, MN, which encompasses Promax, Robinair and Tif.