self-acting valve

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1. Working principle of the self-acting pressure control valve (post-valve pressure control): The pressure P1 of the working medium before the valve is reduced through throttling by the valve core and seat, resulting in the post-valve pressure P2. P2 is delivered through control lines to the lower diaphragm chamber of the actuator, acting on the top plate; the force generated thereby balances the reaction force of the spring, which in turn determines the relative position of the valve core and the valve seat and controls the pressure behind the valve. As the pressure behind the valve, P2, increases, the force exerted by P2 on the top plate also increases. At this point, 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 and the reaction force of the spring reach equilibrium. 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. Similarly, when the pressure P2 behind the valve decreases, the direction of action is opposite to that described above; this is the working principle of a self-acting (pressure behind the valve) pressure control valve. 2. Working principle of the self-acting pressure control valve (pressure control before the valve): The pressure P1 of the working medium before the valve is reduced through throttling by the valve core and seat, resulting in the pressure P2 after the valve. At the same time, P1 is delivered through control lines to the upper diaphragm chamber of the actuator, acting on the top plate; the force generated thereby balances the reaction force of the spring, which in turn determines the relative position of the valve spool and the valve seat, thus controlling the pressure before the valve. As the pressure behind the valve, P1, increases, the force exerted by P1 on the top plate also increases. At this point, the force exerted by the top plate is greater than the reaction force of the spring, causing the valve core to move away from 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 increases, the flow resistance decreases, thereby reducing P1 to the set value. Similarly, when the pressure behind the valve P1 decreases, the direction of action is opposite to that described above; this is the working principle of a self-acting (pressure ahead of the valve) pressure control valve.