Relief Valve

Traditionally, relief valve is a safety valve in which the degree of opening is proportional to pressure. It is used on liquid service only.


Operation Principle of Relief Valve

Operation Principle of Relief Valve

The function of a relief valve is to set the maximum pressure in a hydraulic system. Although there are many designs and varieties, they can all be denoted by the general symbol (a) in Figure 2. It is a normally closed valve which partially opens permitting flow to the tank port when the pressure at the inlet port overcomes the spring force. Symbol (a) does however more accurately represent a direct acting valve. If there is no arrow through the spring the valve is pre-set, i.e. non-adjustable. A two-stage relief valve may be shown as Figure 2(b) as this more closely illustrates its operation which will be described later.