Safety valve is a safety valve, its opening and closing parts of external force in a normally closed state, when the device or medium pressure inside the pipe increases, exceeds the set value automatically open, to prevent the medium pressure piping or equipment exceeds the specified value discharge to the system through the medium. Safety valves are automatic valves, mainly used for boilers, pressure vessels and piping, control pressure does not exceed the specified value, the protection plays an important role in personal safety and equipment operation.