Question 260General Subjects - Assistant Engineer70% to pass
Referring to the illustrated pneumatically operated diaphragm actuated control valve, what statement is true? Illustration GS-0051
AI Explanation
The correct answer is D. The control valve has two discs which are both downward seating.
The reason this is correct is that in a pneumatically operated diaphragm actuated control valve, the valve discs are designed to be downward seating. This configuration allows the valve to fail in the closed position when the pneumatic supply is lost, which is a common safety feature for this type of valve. The two discs ensure a tight seal when the valve is closed.
The other options are incorrect because a single disc valve would not provide the redundancy and fail-safe behavior required for this type of critical control valve. Additionally, upward seating valves are less common in this application and would not provide the desired fail-closed functionality.
Related Questions
#258 Which of the following listed valves would require "blow down" to insure proper operation and prevent damage due to repeated and rapid opening and closing? #259 In the illustrated huddling-chamber safety valve, what statement is true concerning the opening and closing forces acting upon the disc? Illustration SG-0018 #261 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 the stem packing was over-tightened and the stem was unable to vertically move in either direction? Illustration GS-0051 #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