How does the electro-hydraulic directional valve work?

The electro-hydraulic directional valve is composed of a two normally open solenoid valve, a two normally closed solenoid valve, and two 3/8 "ball valves (needle valves). The normally open solenoid valve is installed on the upstream pipeline of the controlled circuit, and the normally closed solenoid valve is installed on the downstream pipeline of the controlled circuit.

In the process of transporting medium through pipelines, when a valve needs to be opened, the computer sends a valve opening signal, and the normally open solenoid valve is energized (closed), while the normally closed solenoid valve is energized (opened). At this point, the channel from the upstream to the chamber on the main valve diaphragm is cut off, and the channel from the chamber on the main valve diaphragm to the downstream is opened. At this point, the pressure at the lower part of the diaphragm is higher than the pressure at the upper part. The medium in 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 computer sends a valve closing signal, and the normally open solenoid valve is disconnected (opened), while the normally closed solenoid valve is disconnected (closed). At this point, the channel from upstream to the chamber on the main valve diaphragm is opened, and the channel from the chamber on the main valve diaphragm to downstream is closed. The high-pressure medium upstream enters the chamber on the main valve diaphragm through a normally open solenoid valve. At this point, the upper and lower pressures of the diaphragm are equal, causing the main valve to close under the action of spring force.

During the opening and closing process of the main valve, the normally open solenoid valve is energized (closed) and the normally closed solenoid valve is de-energized (closed). At this point, both the upstream and downstream channels are in a cut-off state, and the medium pressure is trapped in the upper chamber of the main valve diaphragm, causing the main valve to be locked in a fixed open position due to hydraulic pressure difference, thereby maintaining a constant flow rate from the main valve outlet. When the upstream flow changes, the computer sends a signal to the corresponding solenoid valve based on the feedback signal of the flow meter, which can automatically adjust to the pre-set flow value again.