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- Explain, with the aid of a sketch, the procedure for vapour re-charging of a refrigeration plant.(10)
Procedure for Vapour Re-Charging of a Refrigeration Plant
- Preparation and Safety Checks
- Identify the correct refrigerant type and ensure sufficient quantity is available.
- Confirm that all charging equipment (hoses, manifold gauge set, charging cylinder, and connections) are clean, leak-free, and serviceable.
- Ensure good ventilation and that PPE (gloves, goggles) is worn to prevent refrigerant burns.
- Leak Testing
- Before charging, carry out a leak test (using dry nitrogen/soap solution or electronic detector).
- Any leaks must be repaired and the system evacuated before proceeding.
- Evacuation of System
- Connect a vacuum pump to the charging line via the manifold.
- Evacuate the system to remove air and moisture (typically to about 500 microns/–0.9 bar gauge).
- Isolate and check the vacuum holds to confirm system tightness.
- Connection of Charging Cylinder
- Attach the refrigerant cylinder to the centre (charging) port of the manifold gauge set.
- Purge the charging line by briefly opening the cylinder valve to expel air from the hose.
- Charging in Vapour Form
- Place the refrigerant cylinder upright (so only vapour, not liquid, enters the system).
- Open the low-pressure side of the manifold slowly, allowing vapour refrigerant to be drawn into the system by compressor suction.
- Do not charge through the high-pressure side, as this risks liquid slugging and compressor damage.
- Monitoring During Charging
- Start the compressor and observe suction/discharge pressures.
- Watch the liquid line sight glass for bubbles; continue charging until it runs clear.
- Monitor temperatures and superheat/subcooling to ensure correct operating conditions.
- Completion
- When the correct charge level is reached, close the cylinder and manifold valves.
- Disconnect charging equipment carefully and fit protective caps to service valves.
- Record the type and amount of refrigerant added in the maintenance log (for statutory compliance under MARPOL/FGas regulations).