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6.1.2
Calculation of safety distance S
With vertical protective fields, EN ISO 13855 differentiates between
• S
: safety distance concerning access through the protective field
RT
• S
: safety distance concerning access over the protective field
RO
The two values are distinguished by the way additional distance C is determined:
• C
: from a calculation formula or as a constant, see chapter 6.1.1 "Calculation of safety distance S"
RT
• C
: from a table (see table 6.1)
RO
The larger of the two values S
Calculation of safety distance S
Calculation of safety distance S
S
RT
=
S
RT
K
T
t
a
t
i
t
m
C
RT
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
S
RT
=
K
T
C
RT
S
RT
S
RT
S
is smaller than 500 mm; this is why the calculation may not be repeated with 1600 mm/s.
RT
Implement the stepping behind protection required here, e.g., through the use of an additional or
cascaded safety sensor for area protection.
Calculation of safety distance S
S
RT
=
S
RT
K
T
t
a
t
i
t
m
C
RT
Leuze electronic
or S
RT
RO
and S
RT
RO
acc. to EN ISO 13855 when access occurs through the protective field:
RT
for point of operation guarding
RT
K T
C
+
RT
[mm]
= Safety distance
[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
[s]
= Total time of the delay, sum from (t
[s]
= Response time of the protective device
[s]
= Response time of the safety relay
[s]
= Stopping time of the machine
[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
using the formula acc. to EN ISO 13855.
RT
K T
C
+
RT
[mm/s]
= 2000
[s]
= (0.022 + 0.190)
[mm]
= 8 (20 - 14)
[mm]
= 2000 mm/s 0.212 s + 48 mm
[mm]
= 472
for access guarding
RT
K T
C
+
RT
[mm]
= Safety distance
[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
[s]
= Total time of the delay, sum from (t
[s]
= Response time of the protective device
[s]
= Response time of the safety relay
[s]
= Stopping time of the machine
[mm]
= Additional distance for access guarding with approach reaction with resolutions of
14 to 40 mm, d = resolution of protective device C
if protective fields act orthogonally to the approach direction
is to be used.
> 500 mm
RT
+ t
+ t
a
i
RT
+ t
+ t
a
i
MLC 520 EX
)
m
= 8 (d - 14) mm
RT
> 500 mm
)
m
= 8 (d - 14) mm. Additional dis-
RT
Mounting
20
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