Referring to the illustrated huddling-chamber safety valve, what statement is true concerning the adjustment of the popping pressure? (SG-0018)

Correct Answer: Option C — Popping pressure is adjusted by rotating the compression screw after first loosening the compression screw locking nut (C).

Popping pressure is determined by the spring force acting on the valve disc. Rotating the compression screw adjusts the spring tension; tightening it increases the popping pressure, while loosening it decreases it. The locking nut (C) must be released first to allow for this adjustment and then secured.