Disposal of a 750-lb R-11 Chiller
A hospital is decommissioning a 30-year-old R-11 centrifugal chiller with a nameplate charge of 750 lb. The chiller has been offline for three weeks, and the machine room is at 80°F. The system pressure is 8 psig. The facility plans to cut the chiller up for scrap metal, so the refrigerant must be removed. The technician has a low-pressure recovery machine, a recovery cylinder rated for R-11, and a vacuum pump. The chiller has a rupture disc set at 15 psig and a pressure relief valve. The technician must ensure the appliance is evacuated to the required level before the scrap yard will accept it. The hospital also wants to know what records to keep and whether the recovered R-11 can be resold. The technician is EPA Section 608 certified.
1. What evacuation level must be reached before disposal, and why is that level different from high-pressure appliances?
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Low-pressure appliances being disposed of must be evacuated to 25 mm Hg absolute, which is approximately 29.9 inches of mercury vacuum. This is much deeper than the evacuation levels for high-pressure appliances because low-pressure refrigerants such as R-11 have very low vapor pressure at ambient temperature. A deeper vacuum is needed to remove as much refrigerant as possible without venting. Safety precautions: do not exceed 15 psig during any pressurization, and ensure the chiller barrel is drained of water or isolated before pulling a deep vacuum, because water in the tubes can freeze and damage the heat exchanger.
2. Describe the recovery sequence. Should the technician recover liquid or vapor first, and what equipment is needed?
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Recover liquid refrigerant first, then vapor. Liquid recovery is much faster for low-pressure refrigerants and reduces the amount of vapor that must be pulled through the recovery machine. Use a recovery machine rated for low-pressure refrigerants and a recovery cylinder approved for R-11. Connect to the liquid port and use the machine’s liquid recovery capability, or use a liquid pump if available. Monitor the cylinder weight on a scale to avoid overfilling; never exceed 80% of the cylinder’s capacity by weight. After liquid recovery, switch to vapor recovery and pull the system down to 25 mm Hg absolute. Use a vacuum gauge calibrated for low absolute pressures.
3. What records must be kept for this disposal, and can the recovered R-11 be sold?
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The owner must keep records showing the date of recovery, the amount of R-11 recovered, the evacuation level achieved, the name of the certified technician, and the destination of the refrigerant (reclaimer or scrap yard). These records must be retained for 3 years. The recovered R-11 cannot be sold as-is. To be sold or used in another owner’s equipment, it must be reclaimed to ARI 700 purity standards by an EPA-certified reclaimer. If the hospital intends to reuse the R-11 in its own equipment, it may recycle the refrigerant on site, provided it is not contaminated and meets the applicable purity requirements.