USCG Exam PracticeRefrigeration principles and systems
When a refrigeration system is opened for repair and then reassembled, what procedure must be performed before recharging, and why?
- A. Purge the system with nitrogen to remove refrigerant vapor, preventing flammability hazard
- ✓ Evacuate the system to a deep vacuum to boil off all moisture before rechargingCorrect
- C. Charge the system with a small amount of refrigerant to pressurize and leak-test, then vent to atmosphere
- D. Flush the system with fresh water to remove contaminants, then drain before recharging
Why B is correct
NAVEDTRA 14075 §6-6 states that a system opened for repair is evacuated (pumped down 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. Venting refrigerant to atmosphere is prohibited by regulation.
Cited:NAVEDTRA 14075 §6-6