Directional Valve Symbols

The valve shown is a 4 way two position valve. The '4 way' means it has 4 pipe connections, generally Pressure, Return, Port A and Port B. The 'two position' means that it has two switched positions i.e. it can sit in the A or B position.

Next we have a 2 position 2way valve.

Finally we show 3 way two position valve.

The valves shown above are all drawn with the de-activated position e.g. pushed over by the spring not the solenoid.

Learn more about directional valves

Here we have a 4 way 3 position valve shown in the centre position. This means it has four pipe connections to the valves but 3 different switched positions possible.

Note how this valve now has two springs instead of one. With no signal to the valve it will sit in its central position blocking flow to all ports.

When the electrical solenoids are operated the spool position moves to either the right or left hand position.

The second symbol shows a 2 position detented valve. This valve has no springs but instead the spool is held in position by a mechanical detent when electrical power is removed.

Finally the third symbols shows another 4 way 3 position valve but with a different centre position layout. In this valve the A and B lines are connected to tank instead of blocked, as shown above.

Hydraulic valves can be activated by in many different ways. The symbols here show an electrical solenoid, spring, electrical with hydraulic pilot, hand emergency, proportional solenoid, manual lever and foot operation.

Note how the hydraulic pilot is shown as a solid triangle although if this was a pneumatic pilot it would be shown as solid triangle.

This symbol shows a complete pilot operated directional valve. This would probably be a large, high flow, hydraulically operated bottom valve with a smaller electrically operated pilot valve.

The solenoids show the hydraulic pilot as well as an external pilot pressure supply X and external pilot pressure drain Y.

The symbol also shows and open centre P to T spool.

The proportional valve symbol includes several key differences from the ON/OFF type directional valve. Firstly the outside of the spool section contains lines either side. The solenoids also have arrows running through them to show they operate gradually rather than just on and off.

The square box with the triangle inside represents internal electronics although this will not be present on all proportional valves.

Learn more about proportional valves