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The working principle and selection of pressure relief valve

RKSfluid 2022-04-21 16:45:52

The working principle of pressure reducing valve can be simply understood as inlet pressure + outlet pressure = spring force, by controlling the opening of the valve to control the outlet pressure, the smaller the opening, the smaller the liquid through the closure of the liquid resistance, the smaller the pressure loss, the greater the outlet pressure, on the contrary, the smaller the outlet pressure.

Suppose that the force acting on the diaphragm is F

The outlet pressure acting on the diaphragm of the pressure reducing valve is F1 and the inlet pressure is P1. The acting area of the diaphragm is S1, F1=P1×S1

The inlet pressure acting on the valve core is F2 and the outlet pressure is P2. The acting area of the valve core is S2 F2=P2×S2

When equilibrium is reached, F=F1+F2=P1×S1+P2×S2

When the inlet pressure fluctuates, assuming that the inlet pressure becomes P2+△P and other conditions remain unchanged, then the spring force F < F1+F2, the pressure under the diaphragm pushes the diaphragm upward, the spring is compressed, F becomes larger, at the same time, the closure opening becomes smaller, the liquid resistance becomes greater, the outlet pressure becomes smaller, F2 becomes smaller, until the new equilibrium is reached.

When none of the pressure reducing valve export water or downstream of the pressure reducing valve is closed, outlet pressure continues to increase, F2 continued, under the pressure of diaphragm drive diaphragm continuously upgrade movement until the pressure reducing valve closed, the pressure reducing valve outlet pressure is greater than the set value, but because of inertia effect, upward movement of the diaphragm will not stop immediately, will continue to move up a little, the equivalent of the exit valve cavity, larger volume, the internal liquid pressure drop, until just equals the export of pressure reducing valve set pressure value