The operating principle and types of safety valve
operating principle
Safety valve is a safety device to prevent bursting that caused by pressure equipment and container or easy to cause pressure rise or the container internal pressure exceeds the limits. Safety valve is a safety device that is widely used in pressure vessel, boiler, pressure piping and other pressure systems, to ensure the safe operation of pressure systems. When the container pressure exceeds the design requirements, the safety valve automatically opens, the escaping gas reduces internal over pressure, to prevent the container or pipeline damage. And when the internal pressure reduces to normal operating pressure, the container automatically shuts down to avoid over-pressure exhaust all the gas, lead to waste and production suspension. It is mainly composed by the seat, disc (valve core) and the loading mechanism. Some seats are as a whole with body, some, some are assemblied with body together, and connected with the device. The disc is often associated with stem, it is closely linked on the seat. The upper is a loaded mechanism, the size of the load can be adjusted. When the pressure of internal device is within a certain work pressure scope, the pressure of internal medium acting on the disc is less than the force of the loading body added on the valve, the two differential forms the sealing force between the disc and seat, makes the disc pressing the seat tightly, equipment media can not be discharged. When the pressure of internal device exceeds the work pressure and get to the opening pressure, the pressure of internal medium acting on the disc is larger than the force of the loading body added on the valve, thus disc leave the seat, the safety valve opens, the internal medium are exhausted through the seat, if the discharge is large than equipment safety discharge, the internal pressure is gradually declining, and can drop back to normal working pressure after a short time of exhausting, at this point, the pressure of internal medium acting on the disc is less than the force of the loading body added on the valve, disc presses the seat tightly again, and stop exhausting medium, equipment continues to run with maintaining normal working pressure. Therefore, the safety valve is through growth and decline of upper disc medium force and loading force, self-closed or opened in order to achieve the purpose of preventing device overpressure.
types
At present mass-produced safety valves are spring type and lever type. There are also impulse-type safety valve, pilot-type safety valve, safety switching valve, safety decompression valve, static weight safety valve, etc. Spring-type safety valve relies mainly on the work of the spring force, spring-type safety valve is also have closed and not closed, generally flammable, explosive or toxic media should use enclosed, steam or inert gas, etc., may choose not closed type, and it also has wrench or not have, the main function of wrench is to examine disc flexibility, and sometimes can also be used manually emergency pressure relief. Lever-type safety valve mainly relies on the force of lever heavy hammer to work, but because of lever-type safety valve is often bulky and limit the scope of choice. When the temperature is higher, should be chosen the safety valve with a radiator. The main parameter is displacement, which is determined by the diameter of the seat and disc opening height, from the opening height difference, it can be devided into low lift type and fall lift type. The low lift means the disc open height is 1 / 40 ~ l/20 of the seat throat diameter, fall lift type means the disc open height is 1 / 4 of the seat throat diameter
