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6.2 Calculation of the minimum safety distance
There must be a minimum safe distance between the photoelectric safety sensor
and the point of danger. This distance must be ensured so that the point of danger
cannot be accessed before the hazardous state of the machine has been stopped.
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Install the photoelectric safety sensor at a distance
that is greater than or equal to the minimum safety
distance (S) so that the hazardous area (A) can
only be accessed after complete standstill of the
hazardous machine motion.
According to the European Standard EN 999:2008 the
following formula is to be used to calculate the minimum
safety distance (S):
S = K (t1 + t2) + C
C = 8 (d - 14)
A = hazardous area
H = protected area height
S = minimum safety distance
C = additional distance
S
Minimum safety distance
mm
K
Speed of approach of the object towards the hazardous area
mm/s
t
1
Total response time of the protective equipment, from release to switching off s
t
2
Total response time of the machine, from the stop signal to switching off or to
passing into the state defined as safe
s
C
Additional distance
mm
d
Resolution (detection capacity)
mm
Non-compliance with the minimum safety distance may lead to restrictions
to or loss of the safety function.
