Hydraulic valves

Single overcenter valve for open center VBCL

In stock

Single counterbalance valve not compensated for in-line installation


The counterbalance valves have the task of supporting a suspended load and controlling its downward movement, eliminating vibrations or too fast, and therefore dangerous, lowerings. The VBCL series is designed to be installed in-line within the hydraulic system in compliance with the spaces available on the machine.

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The counterbalance valves VBCL series are single control valves. They control the movement of the cylinder in one direction only (usually the descending phase), while the opposite side of the actuator is free flow supplied. The single overcenter valves are suitable for applications where it is necessary to guarantee stability in the working position and to control the descent phase of a suspended load subject to gravitational force. Inside the hydraulic circuit these valves are usually installed on the return line of the cylinder, while in the delivery phase a by-pass valve allows the supply with free flow. Thanks to a reduction ratio between the load line and the hydraulic driving line (pilot ratio), the pressure required to open the valve is lower than its pressure setting. When the line without load is supplied with oil, the pilot line is also fed and manages a partial opening of the descent line allowing to control the movement of the actuator against the gravitational force avoiding the phenomenon called cavitation. A calibrated orifice on the pilot line also ensures a progressive opening and closing of the valve, avoiding load fluctuations. The single counterbalance valve VBCL also works as a relief valve to protect the structure connected to the actuator: in the event of pressure increase caused by excessive loads or accidental impacts, the valve opens once reached the setting value and unload the exceeding pressure. For this to be possible, the return line on the distributor must be connected to tank. The VBCL is a not compensated valve: any residual pressure on the return line counteract the valve opening, causing an increasing of the pressure setting and of the pilot pressure required to open it. For this reason, this type of valve is better suited to be installed downstream of main valves with open center spools, with users connected to tank in a neutral position. For the sustenance of the load, the seal is a fundamental characteristic for this type of valves. Therefore internal components of Oleoweb’s counrebalance valves are made with high resistence steel, hardened and grinded; also their dimensions and geometric tolerances of the sealing elements are carefully checked during the production process, as well as the sealing of the assembled valve itself. VBCL overcenter valves are parts-in body valves: all components are housed inside an hydraulic manifold. This solution allows to manage high flow rates containing the overall dimensions. The body and the external components are made of high-strength steel and are protected against corrosion by galvanizing. Oleoweb also machines the valve body on the six external faces to guarantee an optimal execution of the surface treatment to the advantage of its effectiveness. For applications exposed to particularly aggressive corrosive agents (eg marine applications) the zinc-nickel treatment is available on request. The steel body also ensures high wear resistance to the benefit of valve reliability and durability. Its shape allows a easy installation with banjo bolts. VBCL valves are available with sizes from BSPP 1/4 " to BSPP 3/4”. Maximum pressure is up to 350 bar (5075 PSI) and it is recommended a maximum flow rates, according with the choosen size, up to 120 lpm (31,7 gpm). For optimal operation, it is recommended to set the overcenter valve at a value of 30% higher than the maximum working load. Several setting ranges and pilot ratios are available to better adapt the valve to all types of applications. With a plastic cap it is also possible to seal the calibration protecting it from possible tampering.

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