A69Y main safety valve is suitable for use on power plant boilers with steam pressure P=10MPa and temperature t=540 ℃, to prevent the medium pressure of the boiler from exceeding the allowable value and ensure safe operation of the boiler. The main structural features of the A69Y main safety valve produced by Shanghai First Ring Road include: 1. The valve is a double exhaust system with flange connections at both ends. It is mainly composed of valve body, connecting pipe, buffer container, piston chamber, valve disc, valve stem and other parts. 2. When the medium pressure rises to the set pressure, the impulse safety valve opens, and the medium enters the piston chamber of the safety valve from the pulse tube, pushing the piston down and causing the valve to automatically open. When the impulse valve closes, the valve disc automatically closes again. 3. The sealing surface is welded with cobalt based hard alloy, and the valve disc is heat-treated to increase its hardness.