Glossary · Guards and machine motion
Guard opening
In machine safety, a guard opening is an opening in a guard whose size and distance from the hazard must prevent access. The permissible size depends on which body part could pass through it and how far the hazard lies behind it.
- Machine safety
- Risk assessment
In one sentence
A guard opening is safe only if its size and its distance from the hazard together keep fingers, hands and arms out of reach; ISO 13857 gives the values.
Example
A mesh guard around a packaging-line gearbox uses square openings small enough that a fingertip passing through cannot reach the rotating shaft behind it.
How it applies
- Machine safety: Openings are needed for ventilation, visibility or material feed. ISO 13857 relates opening shape (slot, square, round) and size to the minimum distance from the hazard, so that fingers, hands or arms cannot reach it. See safe distance and reach distance.
- Design: Feed openings for material often exceed the tabulated sizes. Then additional measures such as tunnels, self-adjusting guards or protective devices are needed.
- Evidence: Record measured opening sizes and distances in the verification report. Later changes, such as a larger infeed or a mesh swap, need a new check.
- Technical documentation: Tell users not to enlarge openings or remove panels to improve access, and name the correct replacement parts.