Q.1.What are the different centre positions of the DC valve?
Following are the different types of centers in a direction control valve.
1) Float centre : Float centre type valves have their Pump port blocked in neutral position. Such type of valves need pressure compensated valves.
b) Open center: The open center valve provides the same benefits as the float spool, but can be used with fixed displacement pumps. The pump flow is naturally unloaded to tank, and the spool also provides a drainage flow path for any accessory valves attached to the A and B work ports.
c) Tandem Centre: The tandem center valve is also used for fixed flow systems where fluid is unloaded to tank in neutral and work port flow is blocked. This spool is common on gear pump systems operating cylinders with no work-holding requirement.