In the illustrated pneumatically-operated diaphragm-actuated control valve, what statement is true concerning the opening and closing forces acting upon the control diaphragm? GS-0051

Correct Answer: Option C — The spring force acting on the control diaphragm is a valve opening force, and the pilot pressure acting on the top of the control diaphragm is a valve closing force.

In this direct-acting, air-to-close configuration, the spring provides the force to hold the valve open. The pilot air pressure is applied to the top of the diaphragm, creating a downward force that opposes the spring, thereby acting as the closing force for the valve assembly.