Novel hydraulically relieved electromechanical direct actuation system for large scale switching valves
Keywords:Electromechanical actuation system, Large sized valves, Valve actuation system, Pilot operation, Flow controlled system
Extensive actuation forces and strokes are required for the actuation of large sized valves normally implemented in high power hydraulic systems. A hydraulic piloted operation is, as for now, the most suitable solution and the state of the art. However, recent research has shown that the application of new electromechanical valve actuation systems is possible in various cases. In this contribution a novel electromechanical valve actuation system for large sized 4/3-way directional control valves in a displacement controlled system is presented. The new actuation system is characterized by a hydraulic relief of the centering springs. Therefore, the springs are only active in safety-critical conditions, as in a power outage. Since the actuator is not working against the spring force during every displacement, the necessary actuation force is reduced drastically, so that common electromechanical actuators can be used. In case of a power outage, the spring relief is deactivated causing the stored energy to center the spool in neutral position. The performance of the novel actuation system is examined based on measurements, which are conducted on a manufactured demonstrator for valves of nominal size 25 with a flow rate of up to 600 l/min.