The Oleoweb valves of the VBZL series are single overcenter valves. The action of sustaining and controlling the movement of the load therefore takes place in one direction only. They are fixed setting valves and do not require the use of further setting times; they therefore represent an ideal solution for optimizing the times and costs of the plant and eliminating the risk of any tampering with the setting. The controlled line must be connected to the return of the cylinder on the load side. In the delivery direction a check valve supplies the actuator in free flow. Powering the opposite side, it acts on the piloting line that manages the gradual opening of the valve, allowing control of the load’s movement. 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. The counterbalance valves can work as an anti-shock valve protecting the mechanical structure from damage caused by pressure peaks. For this to be possible, the return line on the distributor must be connected to the drain. The VBZL is a non-compensated counterbalance valve: any residual pressure on the return line is added to the spring setting and counteract the valve opening. For this reason this type of valve is better suited to be installed downstream of distributors with open center spool, with users connected to discharge in neutral position. Oleoweb pays particular attention to the realization and verification of all the components that realize the hydraulic seal of the valve in order to guarantee the best performance for this fundamental feature of the counterbalance valves. All valves are also tested once assembled. The VBZL counterbalance valves are parts in body valves: all the components are housed inside a hydraulic manifold. This solution allows to manage high flow rates while keeping down the overall dimensions. The body and external components are made of zinc plated steel for better corrosion resistance. Zinc-nickel treatment is available on request for applications in particularly corrosive environments. The machining of the body on the six faces guarantees an optimal execution of the surface treatment to the advantage of its effectiveness. Valve bodies made of steel guarantee working pressures up to 350 bar (5075 PSI) and ensure high wear resistance. VBZL valves are available in sizes from BSPP 1/4 "to BSPP 1/2" for recommended operating flows up to 60 lpm (15,9 gpm).