1- The directional valve
The directional valves can direct oil to receivers (cylinders, motors ...).
There are 2 types of directional valves:
- A poppet valve: They have the distinction of being waterproof. On the other hand, their number of positions remain limited.
- With spools: They can be 3/2 - 4/3 - 6/3 ... On the other hand they are not waterproof.
The directional valve pilot can be:
- Electric.
- Hydraulic.
- Pneumatic.
- Manual (pedal, lever, cable ...)
Pilots can be:
- All or nothing (on- off)
- Or proportional.
The 4/3 type directional valve (4 ports and 3 positions) can be:
- Closed center.
- Open center from P to T (called tandem center).
- Open center (called center in H).
2- Directional valve 4/3 closed center: at rest