A lock valve holds a cylinder exactly where you left it. When the control valve centres, the lock closes and the load cannot drift, creep or settle — not through the spool, not through anything. When the operator calls for movement, pilot pressure from the opposite line opens it again.

This is what a spool with a "closed centre" cannot do on its own. Every directional valve leaks a little across the spool; on a loaded cylinder that leak is a slow, unstoppable drift.

Single or double?

A single lock valve holds one direction — use it where the load only ever acts one way, such as a lift cylinder that cannot be pushed back down. A double lock valve holds both directions and is the right choice for anything that can be loaded either way: outriggers, stabilisers, tilt and steering cylinders.

Aluminium or steel?

Aluminium is lighter and cheaper and does the job in most mobile applications. Steel handles higher pressure cycling and exposure, and is the safer choice on anything safety-critical or anything that will get knocked about.

Also available: VBD38SPA, a 3/8" steel double lock valve in poppet style, and VBD38SFA-M18X1.5 with an M18×1.5 male port. Ask if you need either.

Manufactured by CBF Hydraulic, Montecchio Maggiore, Italy.