Which element in a pilot-operated relief valve is primarily responsible for setting the threshold pressure via a spring?

• A. Poppet
• B. Orifice
• C. Spring
• D. Spool

Answer: (C)

In a pilot-operated relief valve, the moment relief starts is determined by the spring in the pilot valve. That small spring holds the pilot closed until system pressure reaches its setting. Once the system pressure overcomes that spring force, the pilot opens and hydraulic pressure acts on the main valve, pushing its poppet open against the main spring and allowing relief flow. So the pilot spring sets the threshold where relief begins. The main spring mainly influences how far the main valve opens and the flow once relief is happening, not the initial threshold. The other parts—poppet, orifice, and spool—are essential for sealing and directing flow, but they don’t set the starting pressure themselves.