Leuze electronic MLC 520 - Calculation of safety distance SRT for access guarding

Mounting
Leuze electronic MLC 520 21
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 EN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 EN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.