Liquid level gauge glasses (except bull's eye) are generally equipped with which type of valve?

• A. Check valves only
• B. Automatic shut-off valves only
• C. Pressure relief valves only
• D. Isolation valves only

Answer: (B)

Protecting a liquid level sight glass from accidental refrigerant release is the idea here. Liquid level gauge glasses are potential points of leakage if the glass breaks or loosens, so they’re paired with an automatic shut-off valve that closes the line automatically if the sight glass is damaged or removed. This stops refrigerant from spurting out and makes maintenance safer, since you can replace or service the glass without venting the system. The other valve types don’t provide this automatic protection: check valves prevent backflow, pressure relief valves vent only under overpressure, and isolation valves require manual operation and don’t automatically isolate the line when the glass is compromised.