Hydraulic valves

Single overcenter valve for closed center VCCL

In stock

Single counterbalance valve semi-compensated for in-line installation

The counterbalance valves have the task of supporting a suspended load and of ensuring that its descent movement is fluid, without vibrations or sagging that are too sudden and therefore dangerous. Thanks to the BSPP threaded user ports, the VCCL series can be installed in-line inside the hydraulic circuit, taking into account the spaces available on the application.



The VCCL series valves are single counerbalance control valves; they are able to control the movement of the cylinder actuator in only one direction (usually the descent phase) while the opposite side is fed by the free flow. The single counterbalance valves represent the optimal solution for those applications in which it is necessary to guarantee the stability of an actuator in the working position and to manage the descent phase of a suspended load subject to gravitational force. In a hydraulic circuit these valves are installed so that the load control and support line is the cylinder return line, while in the delivery phase the supply is in free flow thanks to the presence of a check valve. Thanks to a reduction ratio between the load line and the hydraulic pilot line (pilot ratio), the pressure required to open the valve is lower than the setting pressure. Powering the line opposite to that of the load, also acted is the pilot line which manages the partial opening of the line of descent thus allowing to control the movement of the actuator and avoid the phenomenon of cavitation by counteracting the gravitational force that tends to accelerate the load descent. A calibrated hole on the pilot line also ensures that the valve is opened and closed gradually, avoiding load oscillations. The VCCL single counterbalance valve also has the function of protecting the structure connected to the actuator: the valve in fact acts as a pressure limiting device (or shockproof) and discharges the excess pressure upon the occurrence of sudden increases that are noted at too high a load or accidental impacts . For this to be possible, the return line on the main valve must be connected to tank. Any residual pressure on the VCCL return line has no influence on the valve setting value but increases the pilot pressure required to open it. The VCCL is in fact a semi-compensated counterbalance valve. For this reason, this type of valve can be installed downstream of main valves with closed center slides, with users closed in neutral position. To sustain the load, it is essential to guarantee high performance regarding hydraulic sealing. For this reason the internal components of the Oleoweb’s counterbalance valve are made of high-strength, hardened and grinded steel and during the production process accurate checks are carried out on the dimensions and geometric tolerances of the sealing parts, as well as on the seal itself when the valve is assembled. The VCCL counterbalance valves are parts in body valves: all the components are housed inside a hydraulic manifold. Thanks to this solution it is possible 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. The processing of the body on the six external faces guarantees to the overcenter valves Oleoweb 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 easy installation even of pipes with banjo bolts. Available in sizes from BSPP 1/4 "to BSPP 1/2", VCCL valves can work in systems with maximum pressures up to 350 bar (5075 PSI). Depending on the size chosen, it is recommended to use it for flow rates up to 60 lpm (15,9 gpm). For optimal operation it is advisable to calibrate the counterbalance valve at a value 30% higher than the maximum work load. Different setting ranges and different piloting ratios are available to better adapt to all types of applications.