Direct-acting pressure reducing valve and pilot-operated pressure reducing valve

Direct acting pressure reducing valve
The direct-acting Wuhan pressure reducing valve is shown as a structural diagram of a direct-acting pressure reducing valve with a relief valve (referred to as an overflow pressure reducing valve).
The compressed air with a pressure of P1 is throttled by the left end input through the valve port 10, and the pressure is reduced to the P2 output. The size of P2 can be adjusted by the pressure regulating springs 2, 3. Rotating the knob 1 clockwise, compressing the springs 2, 3 and the diaphragm 5 causes the spool 8 to move downward, increasing the opening of the valve port 10 to increase P2. If knob 1 is turned counterclockwise, the opening of valve port 10 is reduced and P2 is decreased.
If P1 rises instantaneously, P2 will rise accordingly, causing the pressure in the diaphragm chamber 6 to rise, and the thrust generated on the diaphragm 5 will increase accordingly. This thrust destroys the balance of the original force, and the diaphragm 5 is upward. Moving, a small portion of the airflow is discharged through the overflow hole 12 and the exhaust hole 11. At the same time as the diaphragm moves up, due to the action of the return spring 9, the valve core 8 is also moved upward, and the small intake valve port 10 is closed, and the throttle action is increased, so that the output pressure is lowered until a new balance is reached, and the output pressure is basically Go back to the original value. If the input pressure drops instantaneously, the output pressure also drops, the diaphragm 5 moves down, the spool 8 moves down, the intake valve port 10 opens, and the throttling action decreases, so that the output pressure also returns to the original value. Turn knob 1 counterclockwise. The adjustment springs 2, 3 are relaxed, the force of the gas acting on the diaphragm 5 is greater than the force of the pressure regulating spring, the diaphragm is curved upward, and the intake valve port 10 is closed by the action of the return spring. After rotating the knob 1, the top end of the intake valve core 8 and the overflow valve seat 4 will be disengaged, and the compressed air in the diaphragm air chamber 6 will be discharged through the overflow hole 12 and the exhaust hole 11, so that the valve is in an output-free state. .
In short, the relief pressure reducing valve is decompressed by the throttling action of the air inlet, balanced by the balance of the force on the diaphragm and the overflow of the overflow hole; adjusting the spring can change the output pressure within a certain range. . In order to prevent the above-mentioned overflow type pressure reducing valve from polluting a small amount of gas to the surrounding environment, a pressure reducing valve (ie, a common pressure reducing valve) without an overflow valve may be used.

Pilot operated pressure reducing valve
Internal pilot type Wuhan pressure reducing valve: When the output pressure of the pressure reducing valve is high or the diameter is large, the pressure is directly adjusted by the pressure regulating spring, the spring stiffness is inevitably too large, and the output pressure fluctuates greatly when the flow rate changes. The structural size will also increase. In order to overcome these disadvantages, a pilot operated pressure reducing valve can be employed. The working principle of the pilot type pressure reducing valve is basically the same as that of the direct acting type. The pressure regulating gas used in the pilot type pressure reducing valve is supplied by a small direct acting pressure reducing valve. If the small direct acting pressure reducing valve is installed inside the valve body, it is called the internal pilot type pressure reducing valve; if the small direct acting pressure reducing valve is installed outside the main valve body, it is called the external pilot type pressure reducing valve. . Compared with the direct-acting pressure reducing valve, the nozzle baffle enlargement portion composed of the nozzle 4, the baffle 3, the fixed orifice 9 and the air chamber B is added. When the distance between the nozzle and the baffle changes slightly, the pressure in the B chamber changes significantly, causing a large displacement of the diaphragm 10 to control the up and down movement of the spool 6 to advance The valve port 8 is opened or closed to increase the sensitivity to the spool control, that is, the voltage regulation accuracy is improved.
There is also a small direct-acting Wuhan pressure reducing valve outside the main valve body to control the main valve. This type of valve is suitable for applications with a diameter of 20mm or more, a long distance (within 30m), a high point, a dangerous place, and difficulty in voltage regulation.