Closed Center Valve
A closed center valve closes all ports in neutral, preventing pump flow from returning to tank. It is used with a variable displacement pump; when no work is being done the pump destrokes and only maintains standby pressure. This is the standard architecture of excavators and large mobile cranes.
There is a communication path between the valve and the pump: line pressure or the load sensing signal goes to the pump regulator. With the lever in neutral, demand is zero, the pump pulls its angle to zero and only makes up for leakage. When the lever is moved, demand appears and the pump produces the required flow rate.
- Benefit: there is almost no heat generation at idle and operating at high pressure is efficient.
- Simultaneous motion: in load sensing types, when two motions are performed together their speeds affect each other little.
- Cost: a more expensive pump, tighter filtration, and more complex troubleshooting.
On a closed center machine the first lever movement directly means a flow demand; response starts more sharply than with open center. In electronic lever control this sharpness can be softened with ramp time. The Soft and Dynamic modes of the HCT402 exist precisely to leave this choice to the operator.
Where this term is used: How Are Manual Hydraulic Levers Controlled Remotely? A Comparison of 6 Methods