6
SICK WSU 26/2 – WEU 26/2
8 008 692/9-12-99 Technical Description · WSU/WEU 26-2 © SICK AG · Safety Systems · Germany · All rights reserved
5 Mechanical Arrangement and Mounting
5 Mechanical Arrangement
Fig. 4: Safety distance to light beam
Table 1
shows which C value must
be used for which application.
Number of beams
0
1
0
2
0
3
Height of beam(s)
750
400
0
300
above floor (mm)
900
0
700
1100
C
1200
850
0
850
Table 1: Height of beams above floor
pr EN 999
Safety of machinery
Approach speed of body parts
for arrangement of protective
systems
The WSU/WEU must be attached such that, if the light beam is
broken during hazardous movement of the machinery, the point-
of-operation can only be reached when the power-driven
machinery is no longer in a hazardous state.
For this purpose, a safety distance must be maintained between the
light beam and the nearest boundary of the point-of-operation.
This safety distance is determined according to pr EN 999.
People within the hazardous area but outside the light beam are
not detected. It must, however, be ensured that any hazardous
state can only be initiated when there is no one in the hazardous
area.
Use and mounting of the protective systems is subject to the rele-
vant official rules and regulations. These provisions differ depending
on the area of application.
5.1 Safety distance
The WSU/WEU must be attached
such that, if the light beam is
broken during hazardous
movement of the machinery, the
point-of-operation can only be
reached when this hazardous
movement has ceased. For this
purpose, a safety distance S must
be maintained between the nearest
boundary of the point-of-operation
and the light beam (
Fig. 4
). The
safety distance depends on the
machine stopping time and on the
approach speed of the personnel.
The machine stopping time must be
determined by repeating
measurements under practical
conditions. 1.6 m/s is the
recommended approach speed.
The safety distance is calculated as
follows:
S = v (t
1
+ t
2
) + C
S
Safety distance (mm)
v
Approach speed
1.6 m/s
t
1
Machine stopping time (ms)
t
2
Response time of WEU (22 ms)
C
Dependent on number of beams
(1, 2, or 3), see Table 1
Mechanical
safeguarding
Point-of-operation
S
Entry/exit
guarding
with
WSU/WEU Direction
of entry
into
hazardous
area