USCG Exam PracticeRefrigeration principles and systems
A marine refrigeration system is opened for repair and then reassembled. Before recharging with refrigerant, the system is evacuated to a deep vacuum. What is the PRIMARY technical reason for this procedure?
- A. To verify that the compressor discharge valves are seating properly under vacuum conditions
- ✓ To boil off all moisture, preventing it from freezing at the metering orifice and forming acids and sludge with the oil and refrigerantCorrect
- C. To purge non-condensable air that collected in the condenser during the repair
- D. To confirm there are no leaks in the system before introducing the refrigerant charge
Why B is correct
NAVEDTRA 14075 §6-6 states that a system opened for repair is evacuated to a deep vacuum to boil off all moisture before recharging, because moisture freezes at the metering orifice and reacts with oil and refrigerant to form acids and sludge. While leak checking under vacuum is a common practice, the source text identifies moisture removal as the reason for evacuation.
Cited:NAVEDTRA 14075 §6-6