Safety Light Curtain Separation distance

At Right Angles to Approach

Interactive Tool acc. to ISO 13855:2024

S = v∙T + c + Z

Calculating required minimum distance behind a vertical light curtain.
T ms
d mm
Approach speed v x m/s
Intrusion distance c x mm
Supplemental distance Z mm
Separation distance S x mm
Parameters explained

Above graphic shows general concept only. Separation distance shown is hard to implement: Finger protection (d = ∅14 mm), very fast reaction time, and almost instantaneous stopping are all required. Larger distances impede ergonomy. Contact Engineering Consultant Wolfgang Grassberger for expert help on these topics:

  • Estimating overall system response time
  • Heigth of upper edge (reaching over)
  • Height of lower edge (crawling under)
  • Stepping through
  • Required Performance Level PLr
  • Proving PL in SISTEMA
  • Requirements for muting acc. DIN EN IEC 61496-1
  • Light curtains with starting function acc. DIN EN ISO 12100
  • Validation acc. EN ISO 13849-1
  • Regular Testing

Relevant Parameters

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System response time T
Timespan from actuation of a safeguard until dangerous movement has stopped completely. Overall System Response Time in ISO 13855.
Detection Capability d
Smallest item that actuates safeguard. Sensor Detection Capability in ISO 13855.
Approach Speed v
Speed taken into account when reaching through a safeguard. Approach Speed K in ISO 13855.
Intrusion Distance c
Distance up to which a safeguard is not yet activated by reaching through. Called reaching distance in ISO 13855.
Supplemental Distance Z
Allowance for various measurement errors, lack of ground clearance or decreasing braking torque. To be determined by manufacturer of protective device or by system integrator.
Height h
Height of hazard above floor level. Height a of Hazard Zone in ISO 13855.
Height H
Height of upper edge of a safeguard above floor level, to prevent reaching over.
Separation distance S
Distance between a safeguard and the hazard. Required to stop machine movement in time before hazard can be reached.

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