play a security role in the system. When the system pressure exceeds the predetermined value, safety valves could open automatically and discharge the gas into the atmosphere so that the pressure will not exceed the allowable value, avoiding the accidents. Therefore, safety valves are also known as safety relief valves.
1. The parameters of safety valves
Gas safety valves can be divided into two categories: spring type and the lever type. Besides, safety valves also have other types: impulse safety valve, pilot operated safety valve, switch safety valve, relief safety valve and so on. Mainly working on the force of spring, spring loaded safety valves also have two categories: closed type and open type. Generally, flammable, explosive or toxic media should choose closed type while steam and inert gas are more suitable for open type. A spring-loaded safety valve can also be classified by the wrench. The key role of a wrench is to check the flexibility, and sometimes it can also be used to relief pressure manually. Lever-type safety valves mainly work on the force of the hammer, but their selection range is often limited because of the huge volume.
The main parameters of the gas safety valves
are displacement, which determine the caliber of the seat and the opening height. Because of the different height, gas safety valves can be divided into full open type and small open type. For small open gas safety valves, the opening height is 1/40～l/20 to the throat diameter of the seat, while for the full open type, the opening height is 1/4 to the seat throat diameter.
2. Selection of gas safety valves
The nominal pressure of a safety valve is determined by the operation pressure, as well as the temperature range. But for the rated pressure range of the spring or lever, it is determined by the rated pressure value of a gas safety valve. And for the valve material and structure type are all decided by the media, and then you can calculate the valve throat diameter according to its discharge.