ISO 13855 safety distance calculator
Legacy arithmetic with stated limits. Check the reach-through part of S = K × T + C for perpendicular upper-limb approach to a vertical safety light curtain, with detection capability at most 40 mm. Worked examples, a printable record and a commissioning checklist support the calculation; they do not establish an approved installation.
Calculator
Perpendicular approach to a vertical light curtain only; not a whole-body or horizontal-field calculator.
For finger protection, d=14 mm is common.
Optional margin for repeatability, mounting tolerances, etc.
Measured with a stop-time meter (include worst-case).
From datasheet; add cable/IO latency if specified.
K=2000 mm/s; T=0.2300 s (200+20+10+0 ms); C=0 mm at d=14 mm; minimum=100 mm; extra=0 mm. Rounded upward to whole millimetres. Geometry and 2024 additions are not included.
Formula & constants (ISO 13855)
| Term | Meaning | Typical value / rule |
|---|---|---|
| S | Legacy reach-through subtotal; not final installation distance | S = K × T + C |
| K | Approach speed | Start at 2000 mm/s; 1600 mm/s is conditional on the initial reach-through result exceeding 500 mm. |
| T | Total response time | T = (Tstop + TESPE + Tlogic + Tother) / 1000 s |
| C | Additional distance | For this legacy case with d ≤ 40 mm: C = max(0, 8 × (d − 14)) mm. This is not a universal light curtain rule. Add Cextra if needed. |
| Floor | Minimum distance | The supported calculation enforces 100 mm; conditional 1600 mm/s recalculation enforces 500 mm. A higher policy floor cannot replace omitted geometry. |
Worked examples
Example A — Finger-resolution arithmetic (not a press-brake approval)
K=2000 mm/s, d=14 mm ⇒ C=0; Tstop=180 ms, TESPE=18 ms, Tlogic=10 ms. No extra margin.
T = (180+18+10)/1000 = 0.208 s
S = 2000 × 0.208 + 0 = 416 mm → apply floor ≥100 mm ⇒ 416 mmExample B — Hand-resolution arithmetic (illustrative conveyor inputs)
K=2000 mm/s, d=30 mm ⇒ C=8×(30−14)=128 mm; Tstop=220 ms, TESPE=20 ms, Tlogic=10 ms, margin 20 mm.
T = (220+20+10)/1000 = 0.250 s
Base: S = 2000 × 0.250 + 128 = 628 mm
Add margin 20 mm ⇒ 648 mmExample C — Conditional recalculation (not whole-body protection)
For a legacy vertical reach-through example with d=40 mm and T=0.300 s, the initial 2000 mm/s result is 808 mm. A conditional 1600 mm/s recalculation gives 688 mm, above its 500 mm minimum. This is not a whole-body robot-cell design.
T = 0.300 s; d = 40 mm; C = 208 mm
Initial S = 2000 × 0.300 + 208 = 808 mm > 500 mm
Conditional: max(500, 1600 × 0.300 + 208) = 688 mm
Reach-through subtotal only; geometry remains to be assessedPrintable record (copy to CSV)
Machine/Line,Device,Location,Approach(K mm/s),Resolution d (mm),Tstop (ms),TESPE (ms),Tlogic (ms),Tother (ms),Cextra (mm),S (mm),Date,By,Notes
,,,,,,,,,,,,,
Commissioning & periodic verification
- Stop-time measured with a calibrated meter; worst-case recorded.
- Document effective detection capability, protective height and every access path. Select the required device integrity from the risk assessment and applicable machine standard, not from this arithmetic.
- Validate restart prevention and reset visibility for the application; resetting must not itself initiate hazardous motion. Assess access and undetected presence behind the field.
- Verify output-device diagnostics and feedback where required by the safety architecture. Do not assume every relay provides EDM or manual-reset functions.
- Mounting tolerances reviewed; added margin (Cextra) justified.
- Signage, cleaning plan, and inspection intervals defined.
FAQ
What does C = 8×(d−14) represent?
It is the legacy reach-through addition for perpendicular approach to a vertical light curtain with detection capability at most 40 mm. Use max(0, 8×(d−14)). It does not account for reaching over, under or around the field, and a zero value at d≤14 mm does not eliminate those checks.
Should I always enforce a minimum S?
For this supported legacy case, the base minimum is 100 mm, not an optional policy. A permitted recalculation at 1600 mm/s uses a 500 mm minimum. The tool cannot select a final installation distance because other access paths and current-edition requirements remain outside its scope.
How do I obtain Tstop?
Use verified worst-case stopping performance for the actual machine and operating conditions. Include sensor, logic and other delays once, plus applicable tolerances. If a measurement already includes a delay, do not count it again; if it omits a delay, add it.
Why 2000 mm/s vs 1600 mm/s?
This tool starts the legacy vertical upper-limb calculation at 2000 mm/s. Only if that reach-through result exceeds 500 mm can its 1600 mm/s recalculation be selected, with a 500 mm minimum. That option does not turn the calculator into a whole-body, horizontal-field or robot separation-distance tool.
What if my ESPE datasheet includes cable delay?
Document what the stated response time includes. Add cable, input/output or network delays only when not already included in the quoted total. Use the actual configuration and worst-case response, not a typical value.
Do I always need an extra margin?
Determine required uncertainty and application allowances from the applicable standard, measurements and safety manual. The extra field only adds a documented allowance; an arbitrary margin cannot replace omitted geometry, moving-hazard effects or a full ISO 13855:2024 assessment.
Sources and limits
The ISO 13855:2024 scope covers positioning and dimensioning beyond this tool. OMRON's published safety-distance guidance documents the legacy vertical calculation and its 100/500 mm conditions. Pilz explains the 2024 additions. These references do not certify a DAIDISIKE model or replace the complete standard and machine-specific validation.
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Foshan DAIDISIKE Optoelectronics Technology Co., Ltd. (2025). ISO 13855 Safety Distance Calculator. Retrieved from https://www.fsddsk.com/iso-13855-safety-distance-calculatorContent updated: