pilotoperated

Pilot-operated (sometimes written as pilotoperated) describes devices whose main actuation is controlled by a small pilot signal derived from another part of the system. In valves, a pilot-operated valve uses a pilot valve and a pressure-sensing line to apply pressure to the main element, such as a spool or poppet, allowing a small, controllable signal to control a larger flow. The main valve is typically spring-loaded to close; when the pilot line pressure increases beyond a set threshold, it opens the main valve and fluid passes through. This arrangement enables high flow capacities to be controlled by small control signals, with improved stability and tighter control than direct-acting valves.

Common types include pilot-operated relief valves, which limit system pressure by venting excess fluid once the pilot pressure reaches the setpoint; pilot-operated check valves, which permit flow in one direction but require a pilot signal to allow reverse flow; and pilot-operated safety valves, used on boilers and pressure vessels to relieve pressure when the pilot valve opens.

Advantages of pilot-operated devices include higher capacity for a given control signal, better pressure regulation, and reduced sensitivity to changes in back pressure in the main line. They offer flexible control and rapid, stable responses. Disadvantages include greater complexity, more components that can fail, reliance on a clean and reliable pilot signal, and higher cost and maintenance requirements compared with direct-acting devices.

Applications span hydraulic systems, boiler and pressure vessel protection, fluid power circuits, and various process-control applications where precise, high-capacity actuation is required.