USCG Exam PracticeRefrigeration cycle and components
An engineer opens a refrigeration system for repair and, before recharging, evacuates it to a deep vacuum. What is the PRIMARY reason for this procedure?
- A. To verify the integrity of the compressor discharge valves before restarting
- ✓ To remove moisture that would otherwise freeze at the metering orifice and react with oil and refrigerant to form acids and sludgeCorrect
- C. To purge non-condensable air that has accumulated in the receiver
- D. To reduce the refrigerant charge required to bring the system to operating pressure
Why B is correct
Evacuating the system to a deep vacuum boils off residual moisture. Moisture in a refrigeration system freezes at the metering orifice, blocking refrigerant flow, and reacts with the oil and refrigerant to form acids and sludge that damage the system. While purging non-condensables is also a maintenance task, it is not the primary purpose of deep evacuation before recharging after a repair.
Cited:NAVEDTRA 14075 §6-6