Question 267General Subjects - Assistant Engineer
70% to passSuppose 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
A4.5 psig
B6.0 psig
C7.5 psig
D9.0 psig
AI Explanation
The correct answer is B) 6.0 psig. For a pneumatically operated, diaphragm actuated control valve with a linear response, the pilot pressure is directly proportional to the valve position. Since the position indicator is calibrated in percentage, and it shows the valve to be 75% open, the corresponding pilot pressure would be 75% of the full pressure range, which is 3 to 15 psig. Calculating 75% of the pressure range (15 - 3 = 12 psig) gives a pilot pressure of 6.0 psig. The other options are incorrect because they do not represent the proportional relationship between the valve position and the pilot pressure for a linear response control valve.
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