The Hydrostat Valve Is Not Able To Maintain Consistent Cylinder Flow With Varying Pressures

By Robert Sheaf, CFPAI/AJPP, CFPE, CFPS, CFPECS, CFPMT, CFPMIP, CFPMMH, CFPMIH, CFPMM, CFC Industrial Training

A new hydraulic employee designed a circuit using a proportional valve to control the speed of a cylinder. It was specifically constructed so the flow would be consistent regardless of the forces the cylinder was exposed to. Proportional valves are directional in nature, featuring built-in flow control. These valves need a hydrostat to make them pressure-compensated, offering constant flow regardless of the actuators’ pressure demands.

The new hire’s circuit design is shown. With a hydrostat installed under the proportional valve controls, the pressure drops across the valve spool and does not control the PSI the cylinder requires. However, the new team member’s system is installed to reduce the pressure available at the cylinder with no pressure compensation.

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