The advantage of a pilot-operated relief valve over a direct-acting relief valve is____________.

• A. Shorter pressure span
• B. Lower cost
• C. Less leakage
• D. Less parts

Answer: (A)

Pilot operation gives tighter pressure control by using a small pilot valve to regulate a larger main valve. The pilot senses the system pressure and controls when the main valve opens and closes, so the pressure at which relief starts and the pressure at which it reseats stay close to the set point even as flow changes. That keeps the pressure drop from climbing or fluctuating, effectively producing a shorter pressure span.

Direct-acting relief valves respond directly to inlet pressure with a spring, so their opening and reseating pressures can wander more with flow, leading to a larger span and less stable pressure regulation.