Rupture Disc Release on an R-123 Chiller
A 400-ton R-123 low-pressure chiller (400 lb charge) has a rupture disc that burst, releasing refrigerant into the machine room. The room's refrigerant monitor alarms at 50 ppm. The technician arrives 30 minutes after the release. The chiller is now at 0 psig, and the rupture disc is open to the atmosphere. The machine room is below grade with limited ventilation. The owner wants to replace the rupture disc, recharge the chiller, and restart it the same day. The technician has a low-pressure recovery machine and a replacement rupture disc rated at 15 psig. The facility has no backup chiller, and the outside temperature is 95°F. The technician must decide whether it is safe to enter, what steps to take before repair, and what regulatory requirements apply.
1. What immediate safety actions should the technician take before entering the machine room?
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The technician should not enter the machine room without proper precautions. R-123 is heavier than air and can accumulate in a below-grade space, displacing oxygen. The technician should ventilate the room with portable fans or the installed ventilation system, check oxygen concentration with a calibrated meter, and use a self-contained breathing apparatus if the concentration is high or unknown. All ignition sources should be eliminated because R-123 can decompose into toxic products such as phosgene if exposed to flame or high heat. The area should be evacuated and the owner notified. Entry should proceed only after the atmosphere is verified safe.
2. What must be done before replacing the rupture disc and recharging?
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The technician must recover any remaining refrigerant from the chiller to 25 mm Hg absolute before opening the system for repair. Because the rupture disc is open to the atmosphere, the system is already at 0 psig, but any liquid refrigerant remaining in the chiller must still be recovered; it must not be drained or vented. After recovery, replace the rupture disc with the correct 15 psig rated device. Leak test the system with dry nitrogen at a pressure not exceeding 15 psig, then evacuate to 25 mm Hg absolute. Ensure the chiller barrel water is drained or isolated to prevent freezing during evacuation. Charge with R-123 and verify the repair before restart.
3. What regulatory and recordkeeping requirements apply to this release?
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Under Section 608, the technician must not knowingly vent refrigerant. The release was caused by a rupture disc failure, but the technician must still recover all remaining refrigerant and document the event. The owner should record the date, the amount of R-123 lost, the repair performed, and the amount recharged. These records must be kept for 3 years. The technician should also check whether the release triggers any local, state, or federal reporting requirements; if the amount released exceeds an applicable reportable quantity, the owner must notify the appropriate authorities. The replacement rupture disc must be the correct rating for the chiller, and the pressure relief valve should be inspected.