The Classification of Hydraulic Pressure Relief Valve
There are many kinds of sanitary pressure relief valves, but they can be divided into two general categories: direct-action type and indirect-action type. Direct-action type uses the energy of the medium itself to control the required pressure. Indirect-action type uses external power, such as air pressure, hydraulic pressure or electric power to control the required pressure. Compare these two types, and it’s easy to conclude that the former has a relatively simple structure while the latter has higher precision.
According to the structure of pressure relief valve, they can be divided into:
Piston-type pressure relief valve: It uses the piston to balance pressure and drive the movement of valve flap.
Membrane-type pressure relief valve: It uses membrane as sensing element to drive the movement of valve flap.
Air bag-type pressure relief valve: It uses the pressure produced by medium entering the air-bag to balance pressure.
The above classification method is based on the structure of the valve. According to the types of valve seat, they can be divided into single-seat valve and double-seat valve. On the one hand, double-seat valve can make the force on upper and lower seats mostly balanced and offset, reducing the resultant effected on the valve stem. On the other hand, a larger channel area can be achieved, and the overall size of the valve can be reduced. However, the valve seat technology of pressure relief valve is not good, and machining and grinding of it is difficult. Assembly size chain should be well controlled in order to ensure assembly accuracy, making the valve normal and stable when working.