What is the normal differential pressure?

• A. 8.33 PSI
• B. 8.00 PSI
• C. 9.00 PSI
• D. 7.50 PSI

Answer: (A)

Differential pressure is the difference between the pressure upstream and downstream of a component, and the normal differential pressure is the design point at which the system should operate under normal, unobstructed conditions. This value serves as a baseline: if the measured differential pressure rises, it usually means increasing resistance (like fouling or a narrowing passage); if it falls, there may be a leak, bypass, or too-open a valve.

Here, about 8.33 psi is the standard operating differential for this setup, which is why it’s chosen as the normal value. It corresponds to roughly 57 kPa—a moderate pressure drop typical for many small to medium-scale systems aiming for balanced flow and efficiency. The other figures are close in magnitude but do not align with the design-point standard used for this situation.