Question 264General Subjects - Assistant Engineer70% to pass
In the illustrated pneumatically operated, diaphragm actuated control valve, what statement is true concerning the opening and closing forces acting upon the control diaphragm? Illustration GS-0051
AI Explanation
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.
Related Questions
#262 Suppose the pilot controller for the illustrated pneumatically operated diaphragm actuated control valve is supplied with 20 psig control air and is designed to operate the valve with a pilot pressure ranging from 3 to 15 psig. What would be the indication of a properly adjusted spring #263 Assuming that the flow is from left to right on the illustrated pneumatically operated diaphragm actuated control valve, what statement is true? Illustration GS-0051 #265 Referring to the illustrated pneumatically operated diaphragm actuated control valve, what statement is true? Illustration GS-0051 #266 Suppose the illustrated pneumatically operated diaphragm actuated control valve is used to control the fuel oil outlet temperature of a steam-heated heavy fuel oil heater by controlling the steam flow. What would be the result if there was a complete loss of pilot air being delivered to the valve actuator? Illustration GS-0051 #267 Suppose the pilot pressure is from 3 to 15 psig for the illustrated pneumatically operated, diaphragm actuated control valve. Assuming the control valve is trimmed for a linear response and the travel position indicator is calibrated in percentage, what would be the approximate pilot pressure if the position indicator showed the valve to be 75% open? Illustration GS-0051