According to the safety valve or relief valve structure and loading structure, safety valve or relief valve includes lever safety valve or relief valve, spring safety valve or relief valve and pulse safety valve or relief valve.
1. lever safety valve or relief valve
Lever safety valve or relief valveuses counter weight and lever to balance the acting force on the disc. According to the lever principle, it is possible to adopt smaller counter weight to bring one bigger acting force through the leverage. And through moving the counter weight position or changing the counter weight to adjust the safety valve or relief valvedischarge pressure.
Lever safety valve or relief valveis with simple structure, easy adjusting and more accurate. The loading added on the lever does not increase too much because of the disc lift, so lever safety valve or relief valveis applicable widely to working conditions with high temperature, especially the boiler and pressure vessel with higher temperature. But the structure of lever safety valve or relief valveis heavy; the loading mechanism of lever safety valve or relief valveis easy to vibrate; lever safety valve or relief valvenormally leaks because of vibration; the re-seating pressure of lever safety valve or relief valveis lighter, so the lever safety valve or relief valveis not easy to close or keep tight.
2. Spring low lift safety valve or relief valve
Spring low lift safety valve or relief valveuses the force of compression spring to balance the acting force on the disc. The compression of spiral coil spring can be adjusted by turning the adjusting nut on top of it; it is possible to adjust the discharge pressure set pressure safety valve or relief valveaccording to this structure. The structure of spring low lift safety valve or relief valveis compact and lightweight; the sensitivity of spring low lift safety valve or relief valveis high; the mounting of spring low lift safety valve or relief valveis not limited to working place; and even the sensitivity of spring low lift safety valve or relief valveto vibration is small. So, spring low lift safety valve or relief valvecan be applicable to movable pressure vessel. The drawback of spring low lift safety valve or relief valveis that the added loading changes along with the dis c opening. With the disc lifting, the spring compression will increase, and the acting force on the disc will increase then, which is unfavorable to quick discharge of spring low lift safety valve or relief valve. On the other hand, the spring force will become smaller under the influence of high temperature for long time. So when the spring low lift safety valve or relief valveis applied to higher temperature pressure vessel, it normally should be considered of the spring heat insulation and heat dissipation, and as result that the structure of the spring low lift safety valve or relief valvebecomes complex.
3. Pulse safety valve or relief valve
Pulse safety valve or relief valveis made up of main valve and pilot valve. Pulse safety valve or relief valveworks through the action of pilot valve brings the main valve to act. The structure of pulse safety valve or relief valveis complex. Pulse safety valve or relief valveis normally applied to boiler and pressure vessel whose safety discharge is big.
Among these three types of safety valve or relief valve, the spring safety valve or relief valveis using the most widely.