Glossary · Guards and machine motion
Reach distance
In machine safety, the reach distance is the distance considered when determining whether a person can reach a hazard over, under, around or through a safeguard. It is based on body dimensions and is the input for choosing safe distances.
- Machine safety
- Human factors
In one sentence
Reach distance describes how far a person can reach over, under, around or through a safeguard; ISO 13857 turns body dimensions into design values.
Example
When designing a 1.4-meter fence around a conveyor transfer, the engineer checks in ISO 13857 how far behind the fence the transfer must be so that nobody can reach over it.
How it applies
- Machine safety: ISO 13857 covers reaching upward, reaching over protective structures, reaching around edges, reaching through openings and access with lower limbs. The tables combine hazard height, barrier height and horizontal distance.
- Human factors: Reach values assume people without aids. Where people may climb or use objects to extend their reach, the risk assessment must consider this separately.
- Design: Reach distance together with guard opening size decides whether a perimeter guard or mesh panel prevents access.
- Technical documentation: Record the ISO 13857 table and values used for each guard in the verification records, so that later layout changes can be rechecked.
Reach distance vs. safe distance
Reach distance describes the capability of the human body. Safe distance is the design value chosen so that this reach does not extend to the hazard.