Mounting
Leuze electronic
MLC 520 EX
20
6.1.2 Calculation of safety distance S
RT
or S
RO
if protective fields act orthogonally to the approach direction
With vertical protective fields, EN ISO 13855 differentiates between
• S
RT
: safety distance concerning access through the protective field
• S
RO
: safety distance concerning access over the protective field
The two values are distinguished by the way additional distance C is determined:
• C
RT
: from a calculation formula or as a constant, see chapter 6.1.1 "Calculation of safety distance S"
• C
RO
: from a table (see table 6.1)
The larger of the two values S
RT
and S
RO
is to be used.
Calculation of safety distance S
RT
acc. to EN ISO 13855 when access occurs through the protective field:
Calculation of safety distance S
RT
for point of operation guarding
S
RT
[mm]
= Safety distance
K
[mm/s]
= Approach speed for point of operation guarding with approach reaction and normal ap
-
proach direction to the protective field (resolution 14 to 40 mm): 2000 mm/s or
1600 mm/s, when S
RT
> 500 mm
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
RT
[mm]
= Additional distance for point of operation guarding with approach reaction with resolu
-
tions of 14 to 40 mm, d = resolution of protective device C
RT
= 8
(d - 14) mm
Calculation example
The feeding-in area in a press with a stopping time (including press Safety PLC) of 190 ms is to be safe
-
guarded with a safety light curtain with 20 mm of resolution and 1200 mm of protective field height. The
safety light curtain has a response time of 22 ms.
Calculate safety distance S
RT
using the formula acc. to EN ISO 13855.
K
[mm/s]
= 2000
T
[s]
= (0.022 + 0.190)
C
RT
[mm]
= 8
(20 - 14)
S
RT
[mm]
= 2000 mm/s
0.212 s + 48 mm
S
RT
[mm]
= 472
S
RT
is smaller than 500 mm; this is why the calculation may not be repeated with 1600 mm/s.
Calculation of safety distance S
RT
for access guarding
S
RT
[mm]
= Safety distance
K
[mm/s]
= Approach speed for access guarding with approach direction orthogonal to the protec
-
tive field: 2000 mm/s or 1600 mm/s, if S
RT
> 500 mm
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
RT
[mm]
= Additional distance for access guarding with approach reaction with resolutions of
14 to 40 mm, d = resolution of protective device C
RT
= 8
(d - 14) mm. Additional dis
-
Implement the stepping behind protection required here, e.g., through the use of an additional or
cascaded safety sensor for area protection.
S
RT
K T C
RT
+
=
S
RT
K T C
RT
+
=
S
RT
K T C
RT
+
=
