Recovery Cylinder Overfill and an Unknown Refrigerant
You are recovering R-448A from a medium-temperature supermarket rack that holds a 180 lb charge. The recovery cylinder on your scale is stamped TW 27.4 lb and WC 47.6 lb; the scale currently reads 74.0 lb at 68°F. The rack has been pumped down, and the recovery machine is connected to the low side. A second recovery cylinder sits nearby with about 12 lb of unknown refrigerant left from a previous job; its label is faded and the valve shows no refrigerant identification. Your supervisor wants the job finished before the store opens and suggests topping off the first cylinder because "the scale can be checked later." The mechanical room is warm, and the cylinder has been sitting in direct sunlight. You have a refrigerant identifier, a recovery machine, and a spare labeled cylinder.
1. Determine whether the first recovery cylinder is within the 80% fill limit, and state the immediate actions you would take.
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Use the stamped water capacity, not the nominal cylinder size. The 80% limit is 0.80 × 47.6 lb = 38.1 lb of water-equivalent. R-448A liquid density is roughly 1.05 to 1.1 times that of water at ambient temperature, so the maximum net refrigerant charge is about 40 to 42 lb. Allowed gross weight is therefore about 27.4 + 40 to 42 = 67.4 to 69.4 lb. The scale reads 74.0 lb, which means the net refrigerant is about 46.6 lb and the cylinder is overfilled by roughly 5 to 7 lb. Stop recovery immediately. Do not vent refrigerant and do not "top off" the cylinder. Move it out of direct sunlight, secure it upright, and transfer the excess into an evacuated, labeled recovery cylinder using the recovery machine while weighing continuously. Record the final gross weight and refrigerant type. The 80% limit exists because liquid expansion with rising temperature can hydraulically fill the cylinder and rupture it.
2. What should you do with the unknown 12 lb cylinder, and why is mixing refrigerants unacceptable?
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Treat the unknown cylinder as a separate waste stream. First use a refrigerant identifier and compare the result with the cylinder label and job records. If the refrigerant cannot be positively identified, label the cylinder "UNKNOWN REFRIGERANT - DO NOT USE," recover it into its own dedicated recovery cylinder, and send it to a reclaimer or permitted destruction facility. Never combine it with the R-448A from the rack. Mixing changes the composition and pressure-temperature relationship, may make the lubricant incompatible, and can create a blend that no reclaimer can restore to specification. A mixed cylinder may also have a higher-than-expected pressure at ambient temperature. Venting is prohibited, and using an unidentified refrigerant in equipment can damage the system and create a safety hazard. Accurate labeling and separate recovery are the controls that keep the refrigerant stream reclaimable.
3. List the safety controls and documentation you would use for the rest of this recovery job.
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Use a calibrated scale for every cylinder and record the TW, WC, refrigerant, and gross weight before and after. Keep cylinders upright, secured, and out of direct sun; use caps on unused valves. Wear gloves and eye protection, and avoid breathing refrigerant vapor in the mechanical room. Confirm the recovery machine and hoses are rated for the refrigerant and that the cylinder is not overfilled at any point. Use a refrigerant identifier before transferring any unknown gas. Document the rack charge removed, the cylinder weights, the unknown-cylinder serial number, and the destination of each cylinder. If a cylinder is overfilled, the corrective action and final weight should also be recorded. Keep ignition sources out of the area and follow local refrigerant management rules. The point is traceability: every pound must have a known refrigerant type and a known container.