In the illustrated self-contained, internal-pilot, piston-operated steam pressure- reducing valve, what statement is true concerning the opening and closing forces acting upon the control diaphragm? GS-0044

Correct Answer: Option A — The spring (F) force acting on the control diaphragm is a pilot valve opening force, and the downstream pressure (J) acting on the control diaphragm is a pilot valve closing force.

The spring (F) provides a constant downward force, acting to open the pilot valve. Conversely, the downstream pressure (J) is applied to the underside of the diaphragm, creating an upward force that opposes the spring, effectively acting as a closing force to maintain the set pressure equilibrium.