Hydraulic Control Valves
Hydraulic control valves open and closes at controlled, adjustable speeds to provide for smooth operation and reduce pressure surges associated with conventional check valves.
When the upstream (inlet) pressure is greater than the downstream (outlet) pressure, the hydraulic control valve moves to the open position at a controlled speed by exhausting control water from above the diaphragm to the downstream side through an adjustable needle valve. When the upstream pressure becomes less than the downstream pressure, the hydraulic control valve closes to prevent reverse flow at a controlled speed by introducing control water above the diaphragm from the downstream side through a second needle valve.
Hydraulic Flow Control Valves
As the flow rates tend to vary because of changing line pressures or downstream demand, the differential pressure across the orifice plate also tends to vary. When this occurs, the pilot valve repositions to compensate, and changes the throttled position of the main valve piston to control and maintain the desired flow rate. This is a main characteristic of hydraulic flow control valves.
Hydraulic control valves as used in industrial applications are built in several pressure ranges. The majority of present applications are in the range of 0 to 1500 lb per sq in., but the trend is toward higher pressures. Various types of valves are used in hydraulic systems to control or regulate the flow medium.
Basically valves are expected to control:
Hydraulic Control Valve: Automatic Control Valves