At present, there are a large number of production safety valve spring and leveraged two broad categories. There are also impulse-type safety valve, pilot-type safety valve, safety valve switching, security, decompression valve, safety valve, such as static weight. Mainly depend on spring-loaded safety valve spring and the work force, and spring-loaded safety valve in the closed and non-closed general flammable, explosive or toxic media should be chosen behind closed doors, steam or inert gas can be chosen, such as closed type, in the spring-loaded safety valve with wrench in there and without wrench. The role of wrench valve is mainly to check the degree of flexibility, in some cases can be used as a manual for emergency relief, and in Figure 3. Lever-type safety valve lever to rely mainly on the weight of the work force, but the lever-type safety valve size often limit the choice of scope. Selection of a higher temperature when the safety valve with radiator.
     The main parameter is the safety valve displacement, the displacement determined by the caliber of the valve seat and valve opening height, height from the different open and divided into Enlight and two full-Kai style. Enlight-type refers to the open valve seat height of throat diameter of 1 / 40 ~ l/20. Kai-type refers to the entire valve seat height of the open throat diameter of 1 / 4.