Tag Archive Classification of Safety Valves by Principle of Action

According to the principle of action, it can be divided into direct-acting safety valve and non-direct-acting safety valve.
1. Direct acting safety valve
Direct acting relief valve is opened under the direct action of working medium, that is, relies on the action of working medium pressure to overcome the mechanical load imposed on the valve disc by the loading mechanism, so that the valve opens. The safety valve has the advantages of simple structure, quick action and good reliability. However, due to the structural loading, its load size is limited, and can not be used in high-pressure, large-caliber occasions.
2. Non-direct acting safety valve
This kind of safety valve can be divided into pilot safety valve and power assistant safety valve.
Pilot safety valve is driven or controlled by the medium discharged from the pilot valve. The pilot valve itself is a direct acting safety valve, sometimes other forms of valves are also used. Pilot safety valve is suitable for high pressure and large caliber occasions. The main valve of pilot relief valve can also be designed to be sealed by working medium, or it can impose a much larger mechanical load on the disc than the direct acting relief valve, so it has good sealing performance. At the same time, its movements are seldom affected by back pressure. The disadvantage of this kind of safety valve is that its reliability is related to the main valve and the guide valve. Its action is not as fast and reliable as that of the direct acting safety valve, and its structure is more complex.
The safety valve with power assistant device is forced to open under normal opening pressure by means of a power assistant device. This safety valve is suitable for situations where the opening pressure is very close to the working pressure, or where the safety valve needs to be opened regularly for inspection or blowing out the sticky and frozen medium. At the same time, it also provides a means to force the opening of safety valve in emergency.