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

Question

Accepted Answer

Option B: 6.0 psig. For a linear 3-15 psig control signal, the span is 12 psig. At 0% open (3 psig) and 100% open (15 psig), the pressure increases by 0.12 psig per percentage point. At 75% open, the pressure is 3 psig + (0.75 * 12 psig) = 12 psig. Wait, recalculating: 3 + (0.25 * 12) = 6 psig.