Hydraulic valves

Single counterbalance valve in-line for open center VBLP

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Overcenter valve simple effect not compensated in-line installation


With the Oleoweb VBLP 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 threaded ports, the VBLP overcenter valves are designed to be installed in-line within the hydraulic system in compliance with the spaces available on the machine.

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The Oleoweb overcenter valves of the VBLP series are single counterbalance valves, thus controlling the movement of the cylinder in only one direction (usually the lowering phase) while the opposite side of the actuator is fed by the free flow. These valves, also known as overcenter valves, are suitable for applications with suspended loads and subject to gravitational force which require stability in the working position and control the descent movement. In the hydraulic circuit the installation of these valves requires that the line to be controlled is connected to the return of the cylinder. In the delivery phase, a check valve allows the supply of the same line in free flow. 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. By powering the line on the opposite side, the pilot line acts to manage the partial opening of the descent line and to control the movement of the actuator by counteracting the gravitational force and avoiding the cavitation phenomenon. A hole calibrated on the pilot line also ensures that the valve is opened and closed proportionately, avoiding load oscillations. The VBLP single counterbalance valve can also works as anti-shock valve to protect the structure connected to the actuator when pressure peaks occur due to too high a load or accidental impacts. For this to be possible, the return line on the distributor must be connected to the drain. The VBLP is a non-compensated counterbalance valve: any residual pressures on the return line counteract the opening of the valve by raising the setting and pilot pressure necessary to open it. This type of valve is then better suited to be installed downstream of distributors with open center spool, with users connected to discharge in neutral position. For load support, sealing is a key feature for counterbalance valves. For this reason, the internal components of the Oleoweb VBLP counterbalance valves are made of high-strength, hardened and grinde steel and during the production process the dimensions and geometric tolerances of the sealing parts are accurately checked, as well as the seal itself when the valve is mounted. The VBLP counterbalance valves are parts in body valves: all the components are housed inside a hydraulic manifold. This solution allows you to manage high flow rates while keeping down the overall dimensions. For effective protection against corrosive agents, the body and external components of Oleoweb VBLP valves are made of high-strength steel and subjected to zinc-plating treatment. The valve body is machined on the six faces for an optimal execution of the surface treatment. On request, zinc-nickel treatment is available for applications exposed to particularly corrosive environments (eg marine applications). The steel body allows to work with pressures up to 350 bar (5075 PSI), also guaranteeing a high resistance to wear to the benefit of reliability and durability of the valve. VBLP valves are available in sizes from BSPP 3/8 "to BSPP 1/2" and their use is recommended in systems with flow rates up to 60 lpm (15,9 gpm). Different setting ranges and pilot ratios are available to better adapt to all types of applications. For optimal operation it is advisable to calibrate the counterbalance valve at a value 30% higher than the maximum work load. Valve setting is sealable by a plastic sealing cap.

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