Safety Distance Calculator

Per ISO 13855:2019, the minimum safe distance (S) for a light curtain is calculated as: S = K × T + C, where K is the approach speed (typically 1.6 m/s for walking, up to 2.0 m/s for running), T is the total stopping time (machine stopping time + light curtain response time + any control system delays), and C is additional distance (e.g., 850 mm for reach-through, or user-defined clearance). Our Safety Distance Calculator implements this precisely, applying the safety factor (≥1.0) and configurable C values. Note: K may be reduced to 1.0 m/s if access is restricted or floor conditions limit speed — always validate via risk assessment per ISO 12100.

The safety factor in our calculator multiplies the dynamic component (K × T) — not the entire S value — to account for uncertainties in timing measurements, component aging, or environmental variability. Increasing it from 1.4 to 1.6 directly scales the motion-based portion of the distance, reflecting stricter conservatism aligned with ISO 13855 Annex B guidance on reliability validation. This is distinct from SIL or PL requirements; it’s a design margin applied *before* verification testing. Always document your chosen factor and justify it in your safety file (per ISO 13849-1), especially if deviating from default values used in type-C standards.

Yes — 1.6 m/s remains appropriate for normal walking under typical industrial conditions, including steel-toed boots on concrete, per ISO 13855 Table B.1. This value assumes unrestricted movement and flat, dry surfaces. However, if floor contamination (oil, water), slope (>5°), or mobility aids are present, consider reducing K to 1.2–1.4 m/s and re-evaluate via task-based risk assessment (ISO 12100). Do *not* default to 2.0 m/s unless sprinting is foreseeable — that requires physical barriers, procedural controls, and documented justification. Always verify approach speed empirically using high-speed video or motion capture during hazard analysis.

Use *measured worst-case electro-mechanical stopping time*, verified under load and at maximum operating speed (per ISO 13855 §6.2.2 and ISO 13849-1 Annex J). PLC scan time alone is insufficient — it ignores valve lag, brake engagement delay, and mechanical inertia. Conduct Type-2 or Type-3 stop-time tests per EN/IEC 62061 or ISO 13849-1, logging data across ≥10 cycles. Input the 95th percentile value (or max observed) into the calculator. If only nominal specs exist, apply a ≥20% uncertainty margin before entry. Never rely solely on manufacturer datasheets without field validation — real-world degradation affects timing significantly.

No — this calculator computes *minimum horizontal separation distance* only, per ISO 13855’s primary guarding configuration. Vertical mounting, resolution (e.g., 14 mm vs. 30 mm beam spacing), and detection capability affect *height placement* and *hazard coverage*, but not the S-distance formula itself. For vertical applications, you must separately verify that the light curtain’s optical resolution and height meet ISO 13857 requirements for zone restriction (e.g., 300 mm max gap below lowest beam). Resolution impacts finger/hand intrusion detection — refer to IEC 61496-1/-2 for performance level validation, which influences required PL/PLe but not S.

Yes — the 'additional clearance' input corresponds directly to the C-value in ISO 13855:2019, Table B.1. It accounts for body part penetration (e.g., 850 mm for full-body reach, 200 mm for hand-only access) and compensates for measurement uncertainty or misalignment. Our default 0.5 m aligns with common hand-access scenarios (C = 500 mm), but must be adjusted case-by-case: e.g., use C = 0 mm only for non-penetrating presence sensing (like curtain edges aligned flush with hazard boundary), and C = 850 mm for unrestrained torso access. Always cross-check against Figures B.1–B.4 in ISO 13855 and validate via physical mock-up.

Recalculate *whenever any input parameter changes*: machine retrofit (e.g., faster actuator), firmware update affecting response time, change in operator procedure (e.g., introducing jogging mode), or relocation of the safeguard. Per ISO 13849-1 §5.2.3, validation must occur after *any modification impacting performance*. Annual verification is insufficient — instead, tie recalculations to change control logs. Also revalidate after major maintenance (e.g., brake replacement) or if field measurements show >10% deviation from original T-values. Document all inputs, assumptions, and test evidence in your safety file for audit readiness (EN 1037 compliance).