These safety-check valves are used for those applications
where pressure drops (e.g. holding of a lifted load) must be avoided. Depending on the location in a hydraulic circuit these valves can have different functions. The model VSM-11 can be directly screwed into the oil port of a hydraulic cylinder and works at this location as a “hose break fuse“. The design of the VSM-21 is suitable for a combination with VHP directional valves.
At this location the VSM-21 ensures that the pressure is held precisely and that pressure drops caused by operating the directional valve are avoided.

Operation
After closing the relief valve (hand wheel) the cylinder can be advanced via the by-pass. In direction to the cylinder the valves always have free flow. The built-in check valve ensures that a pressurized cylinder (e.g. a lifted load) is held precisely in stop position.
A smooth lowering speed can be adjusted by opening the throttle valve (hand wheel) in order to relieve the pressure. A safety pressure valve protects the cylinder from being overloaded by external loading.

       
These valves are used to shut-off hydraulic lines especially in multiple cylinder systems. The needle valve VHM-1 also allows you to throttle an oil flow especially within lifting applications.