1、 Working principle
The working principle of a pressure reducing valve is mainly achieved by adjusting the opening of the valve and utilizing the pressure loss generated by the fluid passing through the throttle to achieve the pressure reducing function. It generally includes an adjustable valve core structure. When fluid flows in from the inlet, passes through the throttling area between the valve core and the valve seat, the pressure decreases, and then flows out from the outlet. Under normal circumstances, the inlet pressure acts on one side of the valve core, and the outlet pressure acts on the other side of the valve core through the control channel. The pressure difference between the two is balanced with the spring force, thereby determining the position of the valve core and the opening of the valve.
1) Spring type pressure reducing valve
Valve core position:
When the inlet is blocked, no fluid enters the pressure reducing valve, and the valve core will be in a closed state under the action of spring force. Because there is no import pressure to counteract the spring force, the spring will push the valve core towards the valve seat, causing the valve to close tightly. For example, in a simple water spring pressure reducing valve, after the inlet pressure disappears, the spring will cause the valve core to tightly adhere to the valve seat, preventing any reverse flow or accidental opening.
Due to the lack of new fluid replenishment, the pressure on the outlet side will gradually decrease with the use or leakage of downstream equipment. If the downstream is a closed system and there is no leakage, the outlet pressure will remain basically unchanged, but once there is any trace leakage or usage, the pressure will decrease until it reaches equilibrium with the external environmental pressure or the system is completely depressurized.
3. The difference between constant pressure reducing valve and proportional pressure reducing valve
Fixed pressure reducing valve:
Whether it is a spring-loaded constant pressure reducing valve or a pilot operated constant pressure reducing valve, the main state when the inlet is blocked is that the valve core is closed and the outlet pressure drops. The purpose of a constant pressure reducing valve is to lower the inlet pressure to a fixed output value. When there is no pressure input from the inlet, it cannot achieve the pressure reducing function and only remains closed to prevent backflow and other situations.
Proportional pressure reducing valve:
The output pressure and inlet pressure of the proportional pressure reducing valve are adjusted according to a certain proportional relationship. When the inlet is blocked, like a constant pressure reducing valve, the valve core closes and the output pressure decreases with downstream conditions. However, its internal structure may be slightly more complex due to the design characteristics of proportional adjustment, and the adjustment process may be slightly more complicated when the inlet pressure is restored, requiring the re establishment of control parameters such as valve core position corresponding to proportional relationships.