Tools
Safety distance calculator
Estimate how far a light curtain or other protective device must be from the hazard, from the machine's stopping time and the device's detection capability.
Calculator
Light curtain safety distance
Enter the measured total stopping time and the detection capability of the device. The result updates as you type.
For orientation only. The final safety distance must be determined by a qualified person using the current standards, a measured stopping time and the device manufacturer's data.
Minimum safety distance
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How it works
The formulas behind the calculator
ISO 13855
The minimum distance is S = (K × T) + C. T is the total stopping time of the system: device response, control system and machine. K is the approach speed: 2,000 mm/s, or 1,600 mm/s when the result exceeds 500 mm (with a minimum of 500 mm in that case). For devices with a detection capability d up to 40 mm, C = 8 × (d − 14); for 40 to 70 mm, the formula becomes S = 1,600 × T + 850.
ANSI B11.19
The U.S. method uses Ds = K × (Ts + Tc + Tr + Tbm) + Dpf with a hand speed constant K of 63 in/s (1,600 mm/s), the same constant OSHA uses for presses in 29 CFR 1910.217. Dpf, the depth penetration factor, depends on the device's object sensitivity and is given in its manual.
Fixed guards are different
Fences and other fixed barriers do not depend on stopping time. Their height, distance and openings come from ISO 13857; see our safety fence machine guarding guide.
FAQ
Frequently asked questions
What is total stopping time?
The time from the moment the device detects a person until the hazardous motion has stopped: device response time, control system response and the machine's own stopping time. Measure it on the machine; do not take it from a brochure.
Why does ISO 13855 use two approach speeds?
2,000 mm/s represents hand speed close to the device. For larger distances, where the whole body approaches, 1,600 mm/s is used, with a minimum distance of 500 mm.
Is the result valid for fences?
No. The calculator is for protective devices such as light curtains. Fixed guards use the reach-over and reach-through tables in ISO 13857.
Need the full layout checked?
Our engineers check fence heights, openings and device distances for every layout.