The elasticity of the spring determines the safety of the safety valve

spring type safety valves rely on the elastic pressure of the spring to lock the valve's valve or plunger and other seals. Once the pressure in the pressure vessel is abnormal, the high pressure will defeat the spring pressure of the safety valve, so the locking device is pushed open, causing A pressure relief channel is provided to release the high pressure. According to the different opening height of the valve disc, it is divided into two types: full lift type and micro lift type. The full-lift type has a large discharge capacity and good resilience, and is suitable for liquid and gas media, while the micro-lift type is only suitable for liquid media.

Based on the analysis of the opening characteristics of the spring type safety valve, it can be concluded that under the effect of the external force FW, during the entire process of a safety valve from closing to opening, and then from opening to closing, the external force FW Change the rules, when the additional force gradually increases from zero, and the sum of the internal pressure PL×S is exactly the wave spring preload force, the valve opens slightly, increasing the medium effect area S, so that the internal pressure used to overcome the spring preload force The effective force increases sharply, and as a result, the external force is instantly reduced. Thus the first characteristic peak A appears. When the external force gradually decreases and reaches the closing point, because the medium effect area suddenly decreases, in order to maintain the balanced relationship of the force, at this time, the external force will rise instantaneously, which is the second characteristic peak point B. The above two characteristic peak points A and B are the technical basis for detecting the opening pressure and return pressure of the safety valve under online conditions.

Safety valves can be divided into two types according to their structure: pendulum type, lever type, spring type and pilot type (pulse type); according to the structure of the valve body, they can be divided into two types: closed type and non-closed type. A closed safety valve means that the discharged medium does not leak out and is discharged along the outlet to a designated location. It is generally used in toxic and corrosive media. Regarding safety valves for air and steam, non-closed safety valves are often used. Regarding the selection of safety valve products, it should be confirmed based on the actual sealing pressure. Regarding Tension Spring safety valves, there are springs with several working pressure levels within a nominal pressure (PN) range. In addition to indicating the type, name, medium and temperature of the safety valve when ordering, the valve body sealing pressure should also be indicated. , otherwise it is supplied according to the maximum sealing pressure.