Glossary · Guards and machine motion
Movable guard
In machine safety, a movable guard is a guard that can be opened without tools and is therefore normally linked to the machine control system, typically through an interlocking device.
- Machine safety
- Human factors
In one sentence
A movable guard opens without tools for frequent access; because anyone can open it, it is normally interlocked so opening it stops the hazard.
Example
A sliding door on a packaging machine lets operators clear jams several times per shift; an interlock switch stops the machine whenever the door is opened.
How it applies
- Machine safety: Movable guards are chosen where access is needed often, for setting, loading or jam clearance. They are usually hinged or sliding and should stay attached to the machine when open.
- Functional safety: Because a movable guard opens without tools, the protection comes from the interlock, not from the guard alone. Its design follows ISO 14119 and the required Performance Level or SIL.
- Human factors: If the interlock makes normal work slow, people will defeat it. Consider the task frequency and provide safe operating modes for tasks that need access with the machine running. See tamper resistance.
- Technical documentation: Describe which hazards stop when the guard opens, which remain (for example run-down or stored energy) and how often the interlock must be tested.
Movable guard vs. fixed guard
A fixed guard needs a tool to remove and suits rare access. A movable guard suits frequent access but needs an interlock.