Hydraulic valves

Single counterbalance valve for open center VBZL

In stock

Overcenter valve simple effect not compensated for in-line installation with fixed setting

With the Oleoweb VBZL counterbalance valves it is possible to support a suspended load and control its movement by eliminating vibrations or too fast and dangerous lowering. Equipped with a valve body with BSPP-GAS threaded ports, the VBZL overcenter valves are designed to be installed in-line within the hydraulic system in compliance with the spaces available on the machine. The fixed setting prevents unwanted tamperings of the setting value.



The single overcenter valves of the VBZL series are designed to ensure the stability in the working position of a hydraulic actuator with suspended load, and to control its movement in only one direction (usually the descent phase), leaving the opposite side powered by free flow; thanks to the BSPP-GAS threaded ports, it can be installed in-line into the hydraulic system. By feeding the line opposite the load, the pilot line manages the partial opening of the descent channel allowing control of the actuator movement and avoiding the phenomenon of cavitation thanks to the action of contrasting the gravitational force. A calibrated hole dampens the pilot signal so that the valve opens and closes proportionally, avoiding load oscillations. The VBZL single overcenter valve also works as an antishock valve in the presence of pressure peaks caused by impacts or excessive loads. For this to be possible, the return line on the distributor must be connected to the drain. The VBZL is a not-compensated valve: any residual pressures on the return line counteract the opening of the valve and rises its setting and piloting values. The use of this type of valve is therefore recommended in systems with DCV with an open center spool. The hydraulic leakproof is a fundamental feature for the overcenter valves. To ensure the best performance, Oleoweb manufactures the internal components of its valves in high-strength steel, hardened and grinded, and, during the production process, carefully checks the dimensions and geometric tolerances of the sealing elements, as well as the seal itself on the assembled valve. VBZL are parts-in-body valves: all components are housed inside a hydraulic manifold, a solution that allows to manage high flow rates while limiting overall dimensions. The manifold is made of steel for operating pressures up to 350 bar (5075 PSI) and high wear resistance; it is protected from corrosion by Zinc plating treatment and it is machined on the six faces for a more effective execution of the surface treatment. For applications exposed to particularly aggressive corrosive agents (e.g. marine applications) Zinc-Nickel treatment is available on request. VBZL valves are available in size BSPP 1/4" to BSPP 1/2” for recommended working flow rates up to 60 lpm (15,9 gpm). Different calibration fields and pilot ratios. For optimal operation, it is recommended to set the overcenter valves to a value 30% higher than the maximum working load.