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Working principle of pressure regulating valve in front of (behind) self operated valve

Source: Manufacturer of electric control valve Release time: June 15, 2020 11:57

Self operated regulating valve is divided into three series: self operated pressure regulating valve, differential pressure regulating valve and flow regulating valve. The self operated pressure regulating valve can be divided into two types according to the position of the pressure taking point: before and after the valve. When the pressure measuring point is in front of the valve, it is used to regulate the constant pressure in front of the valve; when the pressure measuring point is behind the valve, it is used to control the pressure behind the valve. When the pressure in front of and behind the valve is introduced to both sides of the air chamber of the actuator at the same time, the pressure difference at both ends of the valve can be adjusted to be constant, or the pressure difference between the two ends of the orifice plate on the pipeline can be introduced to both sides of the air chamber of the membrane actuator to form a self operated flow regulating valve, or the flow can be regulated by the self operated differential pressure regulating valve after the flow is detected by other methods.
 
Pressure control principle behind valve:
The pre valve pressure P1 of the working medium changes to the post valve pressure P2 after throttling the valve core and valve seat. After the relative pressure of the valve core and the bottom of the valve seat is controlled by the pressure of the upper and lower valve seat, which determines the position of the control valve. When the pressure P2 behind the valve increases, the force of P2 acting on the top plate also increases. At this time, the force of the top plate is greater than the reaction force of the spring, making the valve core close to the position of the valve seat until the force of the top plate is balanced with the reaction force of the spring. At this time, the flow area between the valve core and the valve seat decreases, and the flow resistance increases, so that P2 is reduced to the set value. Similarly, when the pressure P2 behind the valve decreases, the action direction is opposite to the above, which is the working principle of the self operated (after valve) pressure regulating valve. This kind of valve should be installed horizontally in the pipeline.
Front pressure control principle:
At the same time, P1 is input to the upper membrane chamber of the actuator through the control pipeline, and acts on the top plate. The force generated is balanced, which determines the relative position of the valve core and valve seat, and controls the front force of the valve. When the pressure P1 behind the valve increases, the force of P1 acting on the top plate also increases. At this time, the force of the top plate is greater than the reaction force of the spring, which makes the valve core move away from the position. Until the force of the top plate is balanced with the reaction force of the spring. At this time, the flow area between the valve core and the valve seat increases, and the flow resistance decreases, so that P1 is reduced to the set value. Similarly, when the pressure P1 behind the valve decreases, the action direction is opposite to the above, which is the working principle of the self operated (front) pressure regulating valve.