The piston type electro-hydraulic valve consists of a two usually open solenoid valve, a two usually closed solenoid valve, 2 3/8 "ball valve (needle valve) combination, usually open solenoid valve is installed in the upstream pipeline of the control loop, normally closed solenoid valve is installed in the downstream pipeline of the control loop.

Piston type electro-hydraulic valve in the process of pipeline transmission medium, when the need to open the valve, the valve open signal issued by the computer, normally open solenoid valve power (closed), and normally closed solenoid valve power (open). At this time, from the upstream to the main valve diaphragm chamber channel is cut off, the main valve diaphragm chamber to the downstream channel is conduction. At this time, the pressure of the lower part of the diaphragm is higher than the upper pressure, the medium of the chamber on the main valve diaphragm is discharged to the downstream pipeline through the normally closed solenoid valve channel, and the main valve is opened.

When the valve needs to be closed, the valve is closed by the computer signal, normally open solenoid valve is disconnected (open), and normally closed solenoid valve is disconnected (closed). At this time, the passage from upstream to the chamber on the main valve diaphragm is conducted, and the passage from the chamber on the main valve diaphragm to the downstream is cut off. The high pressure medium upstream enters the chamber on the diaphragm of the main valve through the normally open solenoid valve. At this time, the diaphragm, the lower pressure is equal, under the action of the spring force to close the main valve.

Piston type electro-hydraulic valve in the main valve opening and closing process, normally open solenoid valve power (closed), normally closed solenoid valve power (closed). At this time, the upper and downstream channels are in the cut-off state, the medium pressure is truncated in the main valve diaphragm chamber, so that the winner valve due to hydraulic pressure is locked in a fixed open position, so as to maintain the main valve outlet to send a constant flow. When the upstream flow rate changes, the computer sends a signal to the corresponding solenoid valve according to the feedback signal of the flow meter, and the flow rate can be automatically adjusted to the preset value again.

Piston type electro-hydraulic valve is equipped with two small ball valve (needle valve) in the control loop as the main valve response valve, installed in the upstream control loop in one to close the regulator, installed in the downstream control loop in one to open the regulator. According to the viscosity of the medium and the actual pipeline pressure used, respectively adjust the opening of two small ball valves (needle valves) can fine tune the opening and closing of the main valve; Small ball valves (needle valves) should not be closed more than 4/5 of full scale.



Piston type electro-hydraulic valve in the control loop is also equipped with a small ball valve as a manual control valve, when the power off or solenoid valve can not work, manual operation of the valve can make the main valve open or close; It can also detect whether the spool diaphragm is damaged.