1. RS
Basics of Hydraulics
VOLUME CONTROLS
Volume or flow control valves used to regulate speed. It is possible to regulate the
flow by using variable displacement pump, but it is more practical to use fixed
displacement pump with flow regulating valve.
Flow control methods:
There are three methods of applying volume control valves to control the flow of the
actuator.
A. Meter in circuit:
In this flow control valve is placed between pump and actuator. It controls the
amount of fluid going into the actuator. The meter in method is highly accurate. It is
used in actuator where load continuously resist the movement of actuator.
B. Meter out circuit:
It is used where the load might tends to run away. The flow control is located where it
will restrict exhaust flow from the actuator.
C. Bleed off circuit:
The flow control is teed off the supply line from the pump and determines the
actuator speed by metering a portion of pump delivery to tank.
In double acting cylinder actuator it is necessity to put flow control valve on the load
bearing side to avoid the fall off of the load in uncontrolled way. If requirement of
load bearing is on both the sides, FCV to put on both the sides. The direction of the
check valve plays an important role in the defining the circuit.
Types of Flow control:
1. Pressure compensated
Load pressure remains relatively constant and feed rates not too critical.
A. The by pass type: It combines overload protection with pressure compensated
control of flow. In has normally closed hydrostat which opens to divert fluid, in
excess of the throttle setting, to the tank.
B. The restrictor type flow control: In this valve hydrostat is normally open and
tends to close off blocking all flow in excess of the throttle setting.
2. Non-Pressure compensated
In this change in the work load would affect the feed rate.
