The trend in today’s mobile hydraulic system design is to use electrohydraulic proportional valves to transmit only enough engine power to drive the specific loads for a job. Because it is not practical to control valves sized for flow rates of 50 l/min (13 gpm) or more directly by proportional solenoids, pilot stages come into play. The pilot stage taps into a machine’s main hydraulic system for pressurized fluid to provide the force needed to control position of spools in large valves...
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