A pilot valve is a small valve that controls a limited-flow control feed to a separate piloted valve. A pilot valve is one part of a larger pilot‑operated valve assembly, typically controlling a high pressure or high flow feed. Pilot valves are useful because they allow a small and easily operated feed to control a much higher pressure or higher flow feed, which would otherwise require a much larger force to operate; indeed, this is even useful when a solenoid is used to operate the valve. Pilot valves are often used in critical applications (e.g., emergency and SIS controls) and are human-operated. They can be set up as a push-to-activate or dead man's switch.
See also Larner–Johnson valve Pilot-operated relief valve
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