Pagina 383 - GC_Sensor_Vision_Safety_Measurement-ENA4

A light grid with 2, 3, 4 separate beams is often used to detect the intrusion of the human body or parts
in a specific area; the number of beams and the distance between them depends on the risk estimation
made and by specific machine applications. Risks such as slipping under the lower beam, passing
over the higher beam, passing through two beams have to be considered.
The following table provides the heights from the ground or from reference plane for different beams.
In case of use of a single beam, in an industrial environment, a height of 750 mm is considered
appropriate, with the device positioned at a machine distance, where
S = (1600 mm/sec x T) + 1200 mm.
Parallel approach to the detection area
S = (K x T) + C
where K = 1600 mm/sec, C = (1200 mm - 0,4 H), not less than 850 mm
Hmax = 1000 mm, Hmin = 15 (d - 50 mm), where d = resolution of the safety light curtain
Angled approach respect to the detection area
For foreseeable approach angles bigger than 30°, follow the normal approach procedure, while for
angles inferior to 30° follow the parallel approach procedure.
Note: The reference Standard is the EN 999 / ISO 13855 ‘Safety of machinery - the positioning
of protective equipment in respect of approach speeds of parts of the human body’. The given
information is indicative and synthetic; it is compulsory to refer to the complete EN 999 / ISO 13855
standard for a correct safety distance calculation.
Number of beams Heights of single beams from the plane (mm)
4 300, 600, 900, 1200
3 300, 700, 1100
2 400, 900