Fiessler ULVT - Horizontal Protection for Hazardous Areas

4.2.2 Horizontal protection of hazardous areas by light grids (EN 999 / ISO 13855)
4 Installation - Safe distance
Calculation examples for the safe distance
with horizontal protection of hazardous
areas using ULVT light barrier:
Example:
ULVT1200/156 light barrier
Response time t1 of light barrier: 18 ms
Run-on time t2 of machine: 50 ms
H = 200 mm
The safe distance is:
S = (1600 mm / s x (0.050 s + 0.018)) +
(1200 mm - 0.4 x 200 mm)
S = 1229 mm
With the ULVT 1200/156, the protective
field depth is 1200 mm.
A distance a between the last beam of the
protective field and the front edge of the
hazardous area must then be 29mm +
7,5mm = 38,5mm
(the last beam must be added).
Formula for calculating the safe
distance with horizontal protection of
hazardous areas using a light curtain:
Here:
K = 1600 mm/s
C = 1200mm-0.4H, but smaller than 850
mm, whereby H is the height in mm
of the protective field above the
reference level, e.g. floor.
T = t1 + t2 (refer also to page 14)
t1 = response time of the barrier
t2 = Overrun period of the machine
With a height H of the protective field
above the floor of > 300 mm, a risk of
crawling under exists. This must be
considered in risk assessment.
The following condition thus applies for H
≥ 300 mm:
1200 - 0.4 x H > 850 mm
The distance a of the end of the
protective field (last beam to front
edge of hazardous area) must be
no more than:
example:
Height 200 mm
a
max
= 200 / 15 + 40 mm
a
max
= 53 mm
S = (1600 mm / s x T) + (1200 mm - 0,4 H)
a = H / 15 + 40 mm
S = Safe distance
Start of protective field (first beam) to
front edge of hazardous area
H
Front edge of hazardous area
H = Height of protective field to reference level
S = (K x T) + C
a = Distance from last beam of protective
field to front edge of hazardous area
S
a
fig 15/1 Horizontal protection
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