Mounting
Leuze electronic GmbH + Co. KG
MLC 530 SPG
53
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 protective field:
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 access guarding with approach reaction with resolutions of 14 to 40 mm,
d = resolution of protective device C
RT
= 8 × (d - 14) mm. Additional distance for access guard-
ing for resolutions > 40 mm: C
RT
= 850 mm (standard value for arm length)
Calculation example
Access to a robot with a stopping time of 250 ms is to be safeguarded with a safety light curtain with 90 mm
of resolution and 1500 mm of protective field height whose response time is 6 ms. The safety light curtain
directly switches the contactors whose response time is contained in the 250 ms. An additional interface
therefore does not have to be taken into consideration.
Ä
Calculate safety distance S
RT
using the formula acc. to ISO 13855.
K
[mm/s]
=
1600
T
[s]
=
(0.006 + 0.250)
C
RT
[mm]
=
850
S
RT
[mm]
=
1600 mm/s × 0.256 s + 850 mm
S
RT
[mm]
=
1260
This safety distance is not available in the application. This is why a new calculation is done with a safety
light curtain with 40 mm of resolution (response time = 14 ms):
Ä
Re-calculate safety distance S
RT
using the formula acc. to ISO 13855.
K
[mm/s]
=
1600
T
[s]
=
(0.014 + 0.250)
C
RT
[mm]
=
8 ×~ (40 - 14)
S
RT
[mm]
=
1600 mm/s × 0.264 s + 208 mm
S
RT
[mm]
=
631
The safety light curtain with a 40 mm resolution is thus suitable for this application.
NOTICE
For the calculation with K = 2000 mm/s, safety distance S
RT
equals 736 mm. The adoption of ap-
proach speed K = 1600 mm/s is therefore permitted.
