What Is The Difference Between Direct Acting And Indirect Acting Safety Valves
Mar 29, 2022
1. Direct acting safety valve
The direct acting safety valve is opened under the direct action of the working medium, that is, it overcomes the mechanical load imposed by the loading mechanism on the valve disc by relying on the pressure of the working medium to open the valve. The safety valve has the advantages of simple structure, rapid action and good reliability. However, due to structural loading, its load is limited and can not be used in high-pressure and large-diameter occasions.
2. Non direct acting safety valve
This kind of safety valve can be divided into pilot safety valve and safety valve with power auxiliary device.
The pilot operated safety valve is driven or controlled by the medium discharged from the pilot valve. The pilot valve itself is a direct acting safety valve, and sometimes other forms of valves are used. Pilot operated safety valve is suitable for high pressure and large diameter occasions. The main valve of the pilot safety valve can also be designed to rely on the working medium to seal, or the mechanical load on the valve disc is much greater than that of the direct acting safety valve, so it has good sealing performance. At the same time, its movement is rarely affected by back pressure. The disadvantage of this safety valve is that its reliability is related to the main valve and pilot valve. Its action is not as fast and reliable as the direct acting safety valve, and its structure is complex.
The safety valve with power auxiliary device is to force the safety valve to open under the condition of lower than the normal opening pressure with the help of a power auxiliary device. This kind of safety valve is suitable for occasions where the opening pressure is very close to the working pressure, or occasions where the safety valve needs to be opened regularly for inspection or to blow away adhesive and frozen media. At the same time, it also provides a means to forcibly open the safety valve in an emergency.
