In a pilot-operated check valve, what component provides the pilot actuation to move the valve element?

• A. Spool
• B. Adjustable knob
• C. Solenoid
• D. Piston

Answer: (D)

The pilot actuation in a pilot-operated check valve is provided by a piston. When pilot pressure is applied to the small pilot chamber, the force on the piston moves, lifting the main valve element off its seat and permitting flow in the forward direction. Once the pilot pressure drops, a spring or load returns the valve to the closed position. Spools are used in other valve types, an adjustable knob only changes preload or cracking pressure, and while a solenoid can generate a pilot signal in some electro-hydraulic setups, the direct actuation of the valve element in this context is achieved by the piston converting the pilot pressure into linear motion.