7
SAFETY DISTANCE CALCULATION
The light curtain / light grid must be installed at a distance that is greater than or equal to the
minimum safety distance
S
, so that a dangerous point can only be reached after all
hazardous machine movements have stopped (Figure 5).
According to EN 999, the minimum safety distance
S
must be calculated using the following
formula:
S = K (t
1
+ t
2
) + C
where:
S
minimum safety distance
mm
K
approach speed of object to the dangerous area
mm/sec
t
1
response time of the safety barrier in seconds
sec
t
2
machine response time, in seconds, meaning the time
required for the machine to interrupt the dangerous movement
following transmission of the stop signal
sec
C
additional distance
mm
The non-observance of the correct safety distance reduces or cancels the protective
action of the light curtain.
If the position of the light curtain / light grid does not prevent the operator from
having access to the dangerous area without being detected, additional mechanical
guards must be installed to complete the system.
“S”=Safety distance
Figure 5
HAZARDOUS
MACHINE
S
