Pilz PSEN op4B-S-3-080 - Manual (Page 15)

Operating Manual PSEN op4B Series
11
2.2.1 Minimum safety distance
The safety distance of the safety light curtain should be such that the
operator cannot reach the danger zone until the movement of the
hazardous machine part has come to a standstill (see Fig. 5).
According to the standards EN 999, 775 and 294, this distance
depends on four factors:
1 Reaction time of the safety light curtain (time it takes for the signal
at the OSSD output to switch from High to Low once the beams
have effectively been interrupted).
2 Machine's overrun time (time it takes for the machine to come to a
standstill once the reaction time of the safety light curtain has
elapsed).
3 Resolution of the safety light curtain.
4 Approach speed of the object requiring detection.
Fig. 5
The formula for calculating the safety distance is as follows:
S = K (t
1
+ t
2
) + C
where:
S = Minimum safety distance in mm between the protected field and
the danger zone
K = The speed at which the object requiring detection (body or parts
of the body) approaches the danger zone, in mm/s
t
1
= Reaction time of the safety light curtain in seconds (Ch. 10
“Technical details”).
t
2
= Machine’s overrun time in seconds
d = Resolution of the safety light curtain.
C = 850 mm for a safety light curtain with a resolution > 40mm