CCH · Engineering Tool

Safety Distance Calculator — ISO 13855:2024

Calculate a preliminary separation distance for a vertically installed safety light curtain with an orthogonal approach, using the current ISO 13855:2024 calculation structure.

ISO 13855:2024 Vertical Light Curtain Orthogonal Approach dₑ ≤ 55 mm
Calculator Scope Know What This Tool Calculates

This calculator is intended for preliminary evaluation of a static, orthogonal approach toward a vertically installed safety light curtain with an effective detection capability of 55 mm or less.

Reaching over, reaching under, effective detection capability, overall system response time and application-dependent supplemental distances must all be evaluated for the actual machine installation.

ISO 13855:2024 Structure
S = (K × T) + DDS + Z
K · Approach Speed 2,000 mm/s initially; 1,600 mm/s may apply when the calculated separation distance exceeds 500 mm.
T · Overall Response Time Safety device + safety control + machine stopping time + applicable tolerance factor.
DDS · Reaching Distance Maximum applicable allowance for reaching over, through or under the protective device.
Z · Supplemental Distance Application-dependent allowance for factors such as uncertainty or changes in stopping performance.
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Safety Distance Inputs

01 Effective Detection Capability
Use effective detection capability, not simply beam spacing.
Do not use the nominal ENT14 / ENT25 / ENT45 resolution automatically when blanking changes the effective detection capability. Determine the effective value for the configured safeguarding function and enter it as a custom dₑ value.
Automatically Calculated DDT reaching-through allowance: —
02 Overall System Response Time T
Use the actual selected ENT model response time.
Include relay/controller response where applicable.
Use validated measured or calculated stopping data.
Account for the applicable response-time tolerance.
03 Reaching Over / Under
Determine from the actual protection-field and hazard geometry using the current standard.
Enter 0 only when reaching under is prevented by the safeguarding design.
04 Supplemental Distance Z
Z can address application-specific factors such as uncertainty, measurement effects or changes in stopping performance. Do not assume Z = 0 without evaluation.
Why the 2024 Calculator Is Different

More Than Resolution and Stop Time

Reaching Through Effective detection capability is used to determine the reaching-through allowance.
Reaching Over / Under Protective-field geometry can create a larger reaching allowance than resolution alone.
Overall Response Time Sensor, safety-related control, machine stopping performance and applicable response-time tolerance must be considered.
Supplemental Distance Z Application-dependent uncertainty and stopping-performance factors can require additional distance.
Engineering-use disclaimer

This calculator provides a preliminary engineering value and does not reproduce the full requirements, tables or application rules of ISO 13855:2024. Users must consult the current standard and the applicable safety-device documentation when designing, validating or modifying a machine safeguarding system. Dynamic applications, parallel approaches, whole-body access, detection capabilities above 55 mm and other configurations require additional evaluation.

Need help with an ENT safety light curtain application? Send the machine layout, protection height, stopping data and mounting arrangement to CCH Engineering for preliminary product selection.
Contact Engineering →