Concerning pressure-relief valves, what statement is true?

Correct Answer: Option A — No stop isolation valve may be installed between the relief valve and its source of pressure, and no stop isolation valve may be installed in the relief valve discharge piping.

Per 46 CFR Subchapter F, safety and relief valves must be installed without any intervening stop valves between the pressure source and the relief valve, or in the discharge piping. This ensures that the system is never isolated from its overpressure protection, preventing catastrophic failure during an emergency.