The main valve comprises a valve body, the upper end of the valve body is connected with a valve
deck, a support is installed at the upper end of the valve
deck through a bolt
assembly, and the support is provided with a
valve opening and closing position and opening degree detection mechanism; a
valve seat is arranged on the valve body, a valve clack
assembly is arranged in a valve cavity located above the
valve seat, a valve clack connector is arranged at the upper end of the valve clack
assembly, a valve rod is connected into the valve clack connector, and the top end of the valve rod penetrates through a spring mechanism and extends out of the upper end of the valve
deck to reach the position of the support. Pressure tapping holes are respectively formed in the front and back of the valve body;
pilot control holes are formed in the front, back and side surfaces of the valve body; the main valve for the
pilot-operated
safety valve adopts a
pilot-operated medium self-driving structural form with a built-in
piston cylinder, and the
stress change of a
piston is formed under the condition that the pressure of an internal medium and the pressure of a pilot loop of an upper cavity of the
piston are changed, so that the opening and closing control of the main valve is realized. The whole main valve has the advantages of being reasonable in space
layout, compact in structure, high in reliability and high in anti-seismic performance.