Every cylinder repressurises at once, and any that lost their position while the machine was down travel to wherever the valve spool leaves them - at full speed, because the speed controls are downstream of the fill. Guards, tooling and anything left in the machine during maintenance are in the path. Gradual build-up gives the control system time to establish a known state before full force is available.

At a set fraction of supply pressure, typically around half, either fixed by the design or adjustable on the unit. Below it the fill passes through the restrictor; above it the main element opens. Setting the threshold too high leaves the machine crawling on restart; too low and the soft-start window closes before slow-moving actuators have settled.

It removes the stored pneumatic energy, which is one hazard among several. Suspended loads still fall when the air that held them is released, springs still act, and electrical and hydraulic energy are untouched. Exhausting is a step in an energy isolation procedure, not the whole of it, and vertical axes usually need a separate means of holding them.

That the internal construction and the fault behaviour have been assessed against ISO 13849-1, generally through redundant elements that monitor each other so a single failure is detected rather than hidden. It is a property of the valve within a defined circuit; wiring a rated valve into an unrated circuit does not carry the rating across.

The volume to be dumped and the time allowed to dump it. The valve's own flow rating is only half the answer - a restricted silencer or a long exhaust line will set the actual time instead. Where a stopping time has been assessed, the exhaust route has to be measured as installed rather than taken from the valve's data sheet.

A lockout valve is a manual device operated by a person and padlocked in the exhausted position for maintenance. A soft-start and dump valve is operated by the control system, cycles routinely and is not a lockout point. Machines normally carry both, and substituting one for the other removes either the manual isolation or the automatic response.

It is often required for commissioning and for recovering a machine that has stalled part way through a cycle, and units are supplied with a non-detenting override for that reason. A detenting override left engaged defeats the dump function, so the choice between the two types is a safety decision rather than a convenience one.