Mounting
Leuze electronic GmbH + Co. KG
ELC 100
16
5.1.2
Calculation of safety distance if protective fields act orthogonally to the approach direction
With vertical protective fields, ISO/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 5.1.1 "Calculation of safety distance S")
• C
RO
: from the following table "Reaching over the vertical protective field of electro-sensitive protective
equipment (excerpt from ISO/EN ISO 13855)"
The larger of the two values S
RT
and S
RO
is to be used.
Calculation of safety distance S
RT
acc. to ISO/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 approach di-
rection 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 resolutions 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 17 mm of resolution and 1200 mm of protective field height. The
safety light curtain has a response time of 17 ms.
Ä
Calculate safety distance S
RT
using the formula acc. to ISO/EN ISO 13855.
K
[mm/s]
=
2000
T
[s]
=
(0.017 + 0.190)
C
RT
[mm]
=
8 × (17 - 14)
S
RT
[mm]
=
2000 mm/s × 0.207 s + 24 mm
S
RT
[mm]
=
438
S
RT
is smaller than 500 mm; this is why the calculation may
not
be repeated with 1600 mm/s.
NOTICE
Implement the stepping behind protection required here, e.g. through the use of an additional
safety sensor.
