10. Functions of Different Hydraulic Valve

Directional Control Valve:
Directional valve controls the direction of oil flow and stops/allows oil flow. The directional control valve for balers has four ports (A, B, P & T). Port A and B connects to the cylinder, port P connects in oil-in pipe and port T connects with the oil tank.

As shown in above drawing, P connects with B and T connects with A, the cylinder moves to the right. When P connects with A, T connects with B, the cylinder will move to the left.
Hydraulic directional valve has two series: manual directional valves and electromagnetic directional valves.

The manual type is using handle to control the movement of the platen. This is a simple structure and has low fault rate.
The electromagnetic directional valve is using buttons to control the platen movement, which is easy to operate but with more complicated electric circuit.

Overflow Valve
Overflow valve controls the system pressure. When the pressure is too high, the valve will automatically discharge some oil and lower the pressure, ensuring the safety of the whole system.

Check Valve
Check valve allows oil flow in one direction only and prevents the refluence of oil to the pump.

Manual Control Directional Valve	Electromagnetic Control Directional Valve
Overflow valve	Check valve