ISO 13857 safety distances for machine guarding
What is ISO 13857?
For machine guarding projects, ISO 13857 is commonly used to assess how a person could reach a hazard:
• Over the top of a perimeter guard;
• Through mesh, slots or other openings;
• Under a guard panel;
• Around the side or end of a guard;
• Through conveyor, product-transfer or service openings; and
• Into a crushing, shearing, drawing-in or entanglement zone.
The standard is especially relevant when selecting guard height, mesh aperture, floor clearance and the distance between the guard and hazardous movement. It does not provide a single universally safe fence height or mesh size. Those dimensions must be assessed against the specific hazard location, opening geometry and possible reach direction.
ISO 13857 does not operate in isolation. Machinery risk assessment and risk reduction are generally addressed through ISO 12100. Guard design and construction are addressed by ISO 14120, while interlocking devices and measures to reduce foreseeable defeat are covered by ISO 14119. Where the position of a protective device depends on approach speed and machine stopping time, ISO 13855 may also be relevant.
Identify the hazardous zone
Assess possible reach paths
Select guard dimensions
Verify the installed layout
How is ISO 13857 used in machine guarding design?
The standard is then used to assess whether the physical layout prevents a person reaching the hazard.
A person could reach over the guard
Guard height, hazard height and the horizontal distance between the guard and hazard must be considered together. A taller guard may reduce reach-over access, but only where the arrangement prevents a person from leaning or reaching into the hazard zone.
A person could reach through mesh or an opening
Mesh aperture and setback distance must be assessed together. A larger opening can allow a finger, hand or arm to extend further through the guard, requiring the hazard to be positioned further away.
A person could reach beneath a guard
Floor clearance must be controlled where lower-limb or upper-limb access beneath the guard could expose a person to the hazard. Uneven floors, ramps, pits and raised machine bases can affect the actual clearance.
A person could reach around a guard edge
Guard ends, wall interfaces, columns, service penetrations and conveyor transfer points require the same attention as the main fence line. A compliant panel arrangement can be undermined by an uncontrolled side gap.
The hazard is inside a large automated cell
Perimeter guarding should be positioned to prevent reach-through and reach-over access while maintaining sufficient separation from hazardous robot movement, conveyors, palletisers, tooling and other equipment in accordance with the risk assessment and applicable machinery or robot safety standards.
Access is required through a gate or door
Safety distance alone may not be sufficient. Where opening a movable guard provides access to hazardous movement, interlocking, guard locking, restart prevention and safety-control performance may need to be considered.
The process requires material transfer openings
Pallet, product or conveyor openings should be designed so that materials can pass through without allowing people to access the hazardous area. Tunnel guards, fixed side protection, interlocked gates or protective devices may be required depending on the application.
Designing machine guarding around ISO 13857
Guard height and hazard position
Mesh aperture and setback distance
Floor clearance and uneven surfaces
Conveyor and product openings
Gates and controlled entry
Existing machinery and retrofit projects
Common ISO 13857 Machine Guarding Mistakes
Common safety-distance issues include:
- Selecting mesh based on appearance rather than aperture and hazard setback;
- Positioning a guard too close to a robot, conveyor, rotating component or pinch point;
- Assuming a standard fence height is appropriate for every machine;
- Leaving large gaps beneath panels because of uneven floors or poor installation;
- Ignoring reach-around access at guard ends, columns and wall interfaces;
- Allowing uncontrolled access through conveyor or material-transfer openings;
- Installing a gate without considering interlocking or restart prevention;
- Changing a guard layout on site without reassessing the safety distance; and
- Treating the physical guard separately from the machine’s controls and operating procedures.
A modular fencing system can provide a practical guarding structure, but conformity with applicable safeguarding requirements depends on the completed layout, openings, access arrangements and machine interface.
Frequently Asked Questions About ISO 13857 (FAQ)
ISO 13857 is an international machinery safety standard that provides safety-distance values intended to prevent hazardous areas being reached by upper and lower limbs.
Yes. ISO 13857 is commonly used when assessing mesh apertures and other guard openings. The opening size and distance from the opening to the hazard must be considered together.
No. There is no single guard height suitable for every application. The required height depends on the location and height of the hazard, the guard position and the potential for a person to reach over the top.
The required distance depends on the type and size of the opening, the direction of possible reach and the location of the hazard. ISO 13857 provides safety-distance values that should be applied to the specific arrangement.
Yes. A guard positioned too close to hazardous movement may allow a person to reach through, over, under or around it. The guard-to-hazard distance must be assessed with the aperture size and other access routes in mind.
Yes. Floor clearance and other lower openings should be assessed where a person may be able to reach a hazardous area with their feet, legs, hands or arms.
ISO 13857 addresses reach-prevention distances. Interlocking devices associated with movable guards are more specifically addressed in ISO 14119. The complete safeguarding arrangement may also require safety-related control-system design.
ISO 13857 provides safety-distance values intended to prevent people reaching hazardous zones. ISO 14120 covers the general design and construction requirements for fixed and movable guards.
Not by itself. ISO 13857 is primarily concerned with reach prevention. Where the position of a protective device depends on approach speed and machine stopping time, ISO 13855 and relevant safety-control requirements may also apply. ISO 13857 does not itself calculate machine stopping distance.
Yes. ISO 13857 is commonly used when assessing retrofit guards around existing machinery. The upgrade should also consider the overall machine risk assessment, actual site dimensions, access requirements, stopping performance and applicable local legal requirements.
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