Proportional Control Valves
Proportionally control the flow into the A or B lines depending on the angle of a hand leaver or value of electrical control signal.
Also available as proportional relief and reducing valves.
Proportional valves require a significant pressure drop across the valve to accurately control the flow, say 30 bar.
Require good fluid cleanliness
Require suitable electrical control cards
Manual or electrical operation.
Spool center leakages vary depending on free flow path or pressure venting.
Pilot or direct operated valves. Low flows generally direct acting, large flows piloted.
Valve response times may vary.
Control pressure drop across valve to give repeatable flow accuracy independent of system.