Trolley-Damaged R290 Display Cabinet in a Trading Aisle
A supermarket display cabinet uses 320 g of R290 (propane) in a sealed hermetic system. The cabinet stands in a busy aisle beside a checkout. The evaporator is at the rear and has been struck by a trolley; the suction line is kinked and there is oily residue at the joint. The cabinet still runs but will not hold temperature, and the store wants it repaired during trading hours. The technician has a brazing torch, dry nitrogen, a vacuum pump and recovery equipment on the van. The cabinet has no isolation valves, and the condenser is in the base. Store policy is to keep the aisle open. The refrigerant is not an HFC, and the technician says “R290 is natural, so venting is not an issue.”
1. What immediate safety and isolation actions would you take, and why is brazing in situ during trading unacceptable?
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R290 is a flammable A3 refrigerant, so the first priority is to control ignition sources and people. Do not braze, grind or use any hot work while the system contains charge. Clear the aisle, isolate the cabinet electrically, put up barriers and keep customers and staff away. Ventilate the area and use a calibrated flammable-gas detector before and during work. Recover the refrigerant into suitable recovery equipment; do not vent it into the store. Because there are no isolation valves, the whole charge must be removed before the damaged section is opened. Brazing in a trading aisle is unacceptable because residual propane can collect in the cabinet base and aisle, and a torch can ignite it. Even a small leak creates a local flammable atmosphere, and the public cannot be evacuated or controlled by the technician.
2. Outline the safe repair and recommissioning sequence, including pressure testing, evacuation and charging.
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After recovery, disconnect and move the cabinet to a ventilated workshop area or a controlled zone. Purge the damaged section with dry nitrogen, cut out the kinked suction line, and braze the replacement with nitrogen flowing through the pipe to prevent internal oxidation. Fit a new filter drier. Pressure-test with dry nitrogen at the manufacturer’s test pressure, never with refrigerant or oxygen, and check all joints with leak-detection fluid. Evacuate with a micron gauge to the manufacturer’s target, typically below 500 microns, and perform a standing vacuum test. Charge R290 by weight only, using a calibrated scale, to the nameplate 320 g; do not charge by pressure. Leak-test the cabinet in a ventilated area, run it to stable temperature, then refit it with the condenser airflow clear. Confirm no smell or detector reading before returning the aisle to service.
3. Why is venting R290 unacceptable, and what records or controls should accompany the job?
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“Natural” does not mean harmless. R290 is highly flammable, and venting 320 g into a store aisle can create a local concentration above the lower flammability limit, especially in a base or enclosed cabinet. Venting also wastes refrigerant and is contrary to good practice and waste controls. The job should be covered by a risk assessment and a hot-work permit, with gas detection, fire extinguisher, barriers and a competent person present. Record the recovery weight, the repair, the nitrogen test pressure and duration, the evacuation reading, the charge weight and the leak test result. Keep the R290 safety data sheet available and ensure staff know the emergency procedure. If the cabinet cannot be repaired safely in the controlled area, it should be isolated and removed from the sales floor.