The counterbalance valve is used for load holding and prevents the load running away uncontrolled. The valve automatically throttles the outgoing flow using a pilot signal from the input flow leg to the ram or motor. The valve symbol is very similar to the Relief valve with a normally closed function and a check valve looped around the main valve.
To open the valve it will need a pilot pressure and for very large loads this should be as small as possible where lighter loads should be higher. The valve will be made with a designed pilot ratio, this is ratio of the pilot pressure against the induced load pressure to open the valve and can be typically 3:1 to 10:1
To establish the way to set up the Counterbalance valve you must know the Pilot Ratio. Pilot Pressure= Valve Setting Pressure – Pressure induced by load divided by the Pressure Ratio + the ratio of piston area divided by the annular ram . A hydraulic motor would be 1.
If we are using a hydraulic motor on a winch it will be important to ensure that there is enough pressure to release the brake. This might require a low Pressure Ratio to achieve enough pressure to release the brake.
If you do not set these valves up correctly the system can become unstable, the ram or motor may not move and in the case of winches the brake might not release.
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Very best wishes
Bob
