Question 264General Subjects - Assistant Engineer

The correct answer is 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. This is correct because in a pneumatically operated, diaphragm actuated control valve, the spring force acts to open the valve, while the pilot pressure acting on the top of the control diaphragm applies a closing force. The spring provides the opening force, while the pilot pressure above the diaphragm pushes the diaphragm down, closing the valve. The other options are incorrect because they do not accurately describe the forces acting on the control diaphragm in this type of valve. For example, option A incorrectly states that the pilot pressure acts on the bottom of the diaphragm, and option B incorrectly reverses the roles of the spring and pilot pressure.