Hydraulic Actuator with Counterbalance Valve

Open Model

The model demonstrates extension, retraction, and holding of a hydraulic actuator with a counterbalance valve. An open-center 4-way directional valve controls a double-acting actuator, and a constant flow rate source equipped with a pressure relief valve serves as the power unit. The actuator is subject to an external force that tries to extend the actuator. The counterbalance valve modulates the return flow into port L, preventing the loss of control of the actuator in extending, as well as holding the piston in place at the neutral position of the valve. Port A of the actuator connects to port P of the counterbalance valve, making it impossible for the cylinder to move until the pressure at port A builds up to a certain level.

To keep the position of the actuator at the neutral position of the 4-way valve, the counterbalance valve has the set pressure differential of $2 \times 1000 N / 0.002 m^2 = 1 MPa$ , where 2 is the safety factor, $1000 N$ is the load, $0.002 m^2$ is the piston area in chamber B of the cylinder. The actuator begins to extend when the pilot pressure increases so that $p_{load}+p_{pilot}R_{pilot}-p_{back}R_{back}>0$ , where $p_{load}$ is the load pressure, $p_{pilot}$ and $R_{pilot}$ are the pilot pressure and pilot ratio, and $p_{back}$ and $R_{back}$ are the back pressure and back pressure ratio, respectively.