Introduction and Explanation of Self-acting Pressure Control Valves

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　　A self-acting pressure control valve operates on the principle of equilibrium between control oil and a spring; its operating state is directly influenced by the control pressure, and it changes accordingly. Understanding the structure of the pressure valve helps in grasping its operating characteristics under different working conditions. It maintains a constant pressure difference between the inlet and outlet of the throttle valve when the load pressure changes. In this way, once the throttle orifice area is set, regardless of how the load pressure changes, the speed control valve can maintain a constant flow rate through it, thereby keeping the movement speed of the actuator stable. 　　An actuator product that achieves automatic regulation by utilizing the energy of the medium being regulated itself is of a right-angle rotary structure; it consists of a V-shaped valve body, a pneumatic actuating mechanism, a positioner, and other accessories. It features an inherent flow characteristic that is approximately proportional to pressure, adopts a dual-bearing design, has low starting torque, and exhibits good sensitivity, response speed, and shear capacity. It can operate in areas without electricity or gas, while also saving energy; the pressure setting can be adjusted at will during operation. It features a quick-opening flow characteristic, offering rapid response and excellent sealing performance; as a result, it is widely used in various industrial devices across sectors such as petroleum, chemicals, power generation, metallurgy, food processing, light textiles, machinery manufacturing, and residential buildings for the automatic control of pressure reduction, pressure stabilization (for regulation after the valve), or pressure relief and maintenance. When equipped with a condenser, it can be used at temperatures up to ≤350°C. 　　This valve is connected via control lines to the lower diaphragm chamber of the actuator, where it exerts force on the top plate; this force balances the reaction force of the spring, thereby determining the relative position of the valve core and the valve seat and controlling the pressure behind the valve. When the pressure behind the self-acting pressure control valve increases, the force acting on the top plate also increases. The force exerted by the top plate is greater than the reaction force of the spring, causing the valve core to move toward the valve seat until the force from the top plate balances the reaction force of the spring. At this point, the flow area between the valve core and the valve seat decreases, the flow resistance increases, thereby reducing P2 to the set value.