8
SAFETY DISTANCE AND POSITIONING
SAFETY DISTANCE AND POSITIONING
The photocell must be installed at a distance greater than or equal to the minimum safety
distance, S, so that no hazardous point can be reached until the hazardous action of the
machine has stopped (fig. 2).
Figure
Figure 2
2
With reference to the proposed European standard prEN999, the minimum safety distance,
S, must be calculated through the following formula:
S = K(tb + tu + t1 ) + C
where:
SS
is the minimum safety distance expressed in mm.
K
K
is the speed of approach of the body to the hazardous zone in mm/sec.
tb+ tu
tb+ tu
is the total reaction time of the sensor plus the control unit (
≤
31ms).
t1
t1
is the reaction time of the machine in seconds, i.e., the time it takes for the machine to
stop the hazardous action from the time the control unit transmits the stop signal through
the opening of its output circuit.
C
C
is an additional distance in mm
