Figure 10.9 shows a circuit in which speed control in a hydraulic circuit is accomplished using a pressure-compensated flow control valve.
The operation of the circuit is as follows:
• In the spring-centered position of the tandem four-way valve, the motor is hydraulically locked.
• When the four-way valve is actuated into the left envelope, the motor rotates in one direction. Its speed can be varied by adjusting the setting of the throttle of the flow control valve. The speed can be infinitely varied as the excess oil goes through the pressure relief valve.
• When the four-way valve is de-activated, the motor stops suddenly and gets locked.
• When the right envelope of the four-way valve is in operation, the motor rotates in the opposite direction. The pressure relief valve provides overload protection when the motor experiences an excessive torque load.