Hydraulic valves

Double counterbalance valve in-line for closed center VBCC

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Double counterbalance valve in-line for closed center


Through the counterbalance valves it is possible to support suspended loads and control their movement during the descent, eliminating vibrations or sagging too quickly and which could generate dangerous situations. The VBCC series is equipped with BSPP threaded ports, thanks to which it can be installed in line inside the hydraulic circuit and positioned according to the spaces available on the machine.

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VBCC counterbalance valves are devices that have the task of controlling the descent or movement of an actuator. They are double-acting valves, thus blocking the actuator – e.g. double-acting cylinder or reversible hydraulic motor - and controlling their movement in both directions. The double counterbalance valves are therefore suitable for applications with suspended loads and subject to gravitational force or bidirectional loads. Within the hydraulic circuit these valves are installed so that the lines with controlled opening are connected to the actuator returns. Two check valves allow free flow supply during the delivery phase. Thanks to a reduction ratio between the load line and the hydraulic pilot line (pilot ratio), the pressure required to open the valves is lower than the setting pressure. Powering the line opposite to load, the pilot line is also fed for managing the partial opening of the descent line, allowing to control the movement of the actuator thanks to the action of contrast to the gravitational force and avoiding cavitation. A further function of the VBCC double counterbalance valve is to protect the system from pressure peaks or damage caused by accidental impacts of the mechanical structure. This is because the valve works as a pressure relief or antishock, when the return line of the distributor is connected to the drain. The VBCC is a semi-compensated counterbalance valve: any residual pressure on the lines between the distributor and the valve have no influence on the setting value of the valve itself but increase the pilot pressure necessary to open it. Thanks to this solution, the VBCC counterbalance valves can be installed in systems where the distributor has spool with closed center in neutral position. For an effective support of the load, the correct seal is a fundamental characteristic for this type of valve. For this reason, the internal components of the Oleoweb overcenter valve are made of high-strength steel, they are hardened and grinded and the production process requires that dimensions and geometric tolerances of the contact parts are accurately checked, as well as the seal itself when the valve is mounted. The VBCC counterbalance valves are parts-in-body type: all the components are housed inside a manifold. This solution allows to manage high flow rates keeping down the overall dimensions. The body and external components are made in steel and zinc plated to be protect against corrosion. Oleoweb machine furthermore the body valve on the six external faces, which ensures an optimal execution of the surface treatment to the benefit of its effectiveness. For applications subject to particularly aggressive corrosive agents (eg marine applications) the zinc-nickel treatment is available upon request. The use of steel as a standard material for the bodies of counterbalance valves guarantees a high resistance to wear to the benefit of reliability and durability of the valve. Its shape is also designed to allow easy installation with banjo bolts. VBCC valves are available in sizes from BSPP 1/4 "to BSPP 1/2" for maximum recommended working flows up to 60 lpm (15,9 gpm). The maximum working pressure is 350 bar (5075 PSI). To obtain optimal operation, it is advisable to calibrate the overcenter valve at a value 30% higher than the maximum working load. Various setting ranges and different piloting ratios are available to better adapt to all types of applications.

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