Mounting
Leuze electronic GmbH + Co. KG
MLC 530 SPG
57
7.1.3
Calculation of safety distance S for parallel approach to the protective field
Calculation of safety distance S for danger zone guarding
S
[mm]
=
Safety distance
K
[mm/s]
=
Approach speed for danger zone guarding with approach direction parallel to the protective field
(resolution up to 90 mm): 1600 mm/s
T
[s]
=
Total time of the delay, sum from (t
a
+ t
i
+ t
m
)
t
a
[s]
=
Response time of the protective device
t
i
[s]
=
Response time of the safety relay
t
m
[s]
=
Stopping time of the machine
C
[mm]
=
Additional distance for danger zone guarding with approach reaction H = height of the protec-
tive field, H
min
= minimum installation height permitted, but no smaller than 0, d = resolution of
the protective device C = 1200 mm - 0.4 × H; H
min
= 15 × (d - 50)
Calculation example
The danger zone in front of a machine with a stopping time of 140 ms is to be safeguarded as close to the
floor height as possible using a horizontal safety light curtain as a replacement for a PS mat. Installation
height H
min
can be = 0 - additional distance C to the safety distance is then 1200 mm. The shortest possible
safety sensor is to be used; the first value to be selected is to be 1350 mm.
The receiver with 40 mm of resolution and 1350 mm protective field height has a response time of 13 ms,
an additional relay interface a response time of 10 ms.
Ä
Calculate safety distance S
RO
using the formula acc. to ISO 13855.
K
[mm/s]
=
1600
T
[s]
=
(0.140 + 0.013 + 0.010)
C
[mm]
=
1200
S
[mm]
=
1600 mm/s × 0.163 s + 1200 mm
S
[mm]
=
1461
The safety distance of 1350 mm is not sufficient; 1460 mm are necessary.
This is why the calculation is repeated with a protective field height of 1500 mm. The response time is now
14 ms.
Ä
Re-calculate safety distance S
RO
using the formula acc. to ISO 13855.
K
[mm/s]
=
1600
T
[s]
=
(0.140 + 0.014 + 0.010)
C
[mm]
=
1200
S
[mm]
=
1600 mm/s × 0.164 s + 1200 mm
S
[mm]
=
1463
A suitable safety sensor has been found; its protective field height is 1500 mm.
The following changes should now be taken into account in this example of the application conditions:
Small parts are occasionally thrown out of the machine; these can fall through the protective field. This
should not trigger the safety function. In addition, the installation height is increased to 300 mm.
