TYPES OF VALVES
Figure 29 Safety Valve
Pilot-Operated Relief Valves
Pilot-operated relief valves are designed to maintain pressure through the use of a small passage
to the top of a piston that is connected to the stem such that system pressure closes the main
relief valve. When the small pilot valve opens, pressure is relieved from the piston, and system
pressure under the disk opens the main relief valve. Such pilot valves are typically solenoid-
operated, with the energizing signal originating from pressure measuring systems.