Question 261General Subjects - Assistant Engineer70% to pass
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
AI Explanation
The correct answer is B) The valve will lose control of the fuel oil temperature with the result that the fuel temperature will fluctuate with changes in fuel demand.
Explanation:
If the stem packing is over-tightened, the stem will be unable to move vertically in either direction. This means the valve will not be able to respond to changes in the fuel oil temperature and modulate the steam flow accordingly. As a result, the valve will lose control of the fuel oil temperature, causing it to fluctuate with changes in fuel demand, rather than maintaining a stable temperature.
The other options are incorrect because: A) the valve would not fail in the fully closed position, C) the valve would not fail in the fully open position, and D) it is possible to predict the valve's response to over-tightened packing, as explained above.
Related Questions
#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 #260 Referring to the illustrated pneumatically operated diaphragm actuated control valve, what statement is true? 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 #264 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