The self-operated pressure regulating valve is a hydraulic condition balancing valve with automatic constant pressure difference. It is used in water systems such as heating and central air conditioning to support the independent adjustment and elimination of pipe network pressure by each user terminal device of the controlled system. According to the position of the pressure point, self-operated pressure regulating valves can be divided into two categories: before the valve and after the valve. The pre-valve pressure regulating valve is used to regulate the pressure in front of the valve to be constant, while the post-valve pressure regulating valve is used to regulate the pressure behind the valve to be constant.

Post-valve pressure control is the working principle of the self-operated pressure regulating valve. The pressure in front of the valve P1 of the working medium becomes the pressure behind the valve P2 after being throttled by the valve core and valve seat. P2 is input into the lower diaphragm chamber of the actuator through the control pipeline and acts on the top plate. The generated force is balanced with the reaction force of the spring, which determines the relative position of the valve core and valve seat, and controls the pressure behind the valve. When the pressure P2 behind the valve increases, the force P2 acts on the top plate also increases. At this time, the action force of the top plate is greater than the reaction force of the spring, causing the valve core to close toward the valve seat until the action 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 becomes larger, thereby reducing P2 to the set value. In the same way, when the pressure P2 behind the valve decreases, the direction of action is opposite to the above.

Self-operated pressure regulating valves should generally be installed horizontally in pipelines. When it is necessary to change the set value of the pressure P2 behind the valve, the adjusting nut can be adjusted.