What is a safety valve
The safety valve is a special valve which is normally closed under the action of external force. When the medium pressure in the equipment or pipeline increases more than the specified value, the medium pressure in the pipeline or equipment can be prevented from exceeding the specified value by discharging the medium to the system. Safety valve is an automatic valve, mainly used in boilers, pressure vessels and pipelines. The control pressure does not exceed the specified value, which plays an important role in protecting personal safety and equipment operation. The safety valve can only be used after pressure test.
Safety valves are classified according to the principle of action
1. Direct acting safety valve
The direct acting safety valve is opened under the direct action of the working medium, that is, the mechanical load imposed on the valve disc by the loading mechanism is overcome by the pressure of the working medium, so that the valve can be opened. The safety valve has the advantages of simple structure, quick action and good reliability. However, due to the structural loading, the load is limited and can not be used in high pressure and large caliber occasions.
2. Non direct acting safety valve
This kind of safety valve can be divided into pilot type safety valve and safety valve with power auxiliary device. Pilot type 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 valve are also used. Pilot type safety valve is suitable for high pressure, large caliber occasions. The main valve of pilot type safety valve can also be designed to rely on the working medium to seal, or it can exert much larger mechanical load on the disc than 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 kind of 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 more complex.