Hydraulic valves

Single counterbalance valve for open center with bolt VBCB

In stock

Overcenter valve simple effect not compensated with banjo bolt

Thanks to the VBCB counterbalance valves it is possible to manage suspended loads and control their movement by eliminating vibrations or sudden and dangerous lowerings. The banjo bolt on the body valve simplifies the installation and makes the action of the valve more effective.



The single VBCB series overcenter valves are specifically designed for applications where it is necessary to guarantee the stability in the working position of a hydraulic cylinder with suspended load and to control its movement in only one direction (usually the descent phase), leaving the opposite side of the actuator powered by free flow. Thanks to the valve body predisposed for the installation of a banjo bolt on the load side, the VBCB counterbalance valves can be installed directly on the cylinder, simplifying the circuit to the advantage of assembly times, and optimizing performance thanks to containment of the hysteresis phenomenon. The banjo bolt must be connected to the load line on the cylinder return. Along the same line, the oil flow in the opposite direction is free thanks to a by-pass valve. Powering the line opposite to the load, the pilot line is fed as well, with the task of managing the partial opening of the descent line allowing the control of the movement of the actuator and avoiding the phenomenon of cavitation thanks to the action of contrasting the gravitational force. A reduction ratio between the load line and the hydraulic pilot line (pilot ratio) allows the valve to be opened at a lower pressure than the setting one. The pilot signal is damped by a calibrated hole so that the opening and closing of the valve take place proportionally avoiding load oscillations. The VBCB single counterbalance valve also functions as a pressure relief valve: in the event of a sudden and excessive increase in pressure due to, for example, an excessive load or an impact, the valve protects the hydraulic system itself and the mechanical structure, discharging the exceeding pressure. For this to be possible, the return line on the distributor must be connected to the drain. The VBCB is a non-compensated counterbalance valve: any residual pressure on the return line counteracts the opening of the valve by raising the pressure and piloting value necessary to open it. For this reason, it is recommended to use this type of valve better in systems where main valve has open center spool, with users connected to tank in neutral position. The hydraulic seal of the overcenter valves is a fundamental characteristic for sustaining the load. In order to guarantee the best performance on this fundamental aspect, Oleoweb manufactures the internal components of the counterbalance valve in high-strength steel, hardened and grinded, and during the production process the dimensions and geometric tolerances of the sealing parts are accurately verified, as well as the seal itself when the valve is assembled. The VBCBs are parts-in-body counterbalance valves: all components are housed inside a hydraulic manifold. This solution allows to manage high flow rates while keeping down the overall dimensions. The Oleoweb counterbalance valves have steel body as standard in order to reach operating pressures up to 350 bar (5075 PSI) and guarantee a high resistance to wear with benefit of reliability and valve life. Body and external components are protected from corrosion by zinc-plating treatment. The valve body is machined on the six faces for an optimal and more efficient execution of the surface treatment. For applications exposed to particularly aggressive corrosive agents (eg marine applications) the zinc-nickel treatment is available on request. VBCB valves are available in size BSPP 3/8 "for recommended working flows up to 40 lpm (10,6 gpm). Several setting ranges and different piloti ratios are available to better adapt to all types of applications. By applying a plastic cap to the adjustment screw it is also possible to seal the setting, protecting it from tampering. For optimal operation it is recommended to set the counterbalance valves at a value 30% higher than the maximum work load.