57
2540772-01-11/21 (translation of the original operating instructions)
Operating Instructions Bus Module
MBM-EC-..-MLI-… (EtherCAT)
EN
14.1. Calculation example for determining the risk time for safe functions
Important!
Only modules and submodules that contain a safety function flow into the calculation of the risk time.
Safe modules and submodules are apparent because they transmit safe bits (FSoE bits) via the bus
module to the control system.
Modules with safety functions are, for example:
Ì
Interlocking and locking modules MGB2-I…/MGB2-L…
Ì
Submodules MSM with emergency stop, safe enabling switch, safe selector switch, enabling
switch, etc.
The following formula applies to the calculation of the risk time for your system:
T
Risk
= T
P
+ n x t
L
T
Risk
= Total risk time for a safety function
T
P
= Processing time for safety function (general figure 250 ms)
t
L
= Latency time for a safe module/submodule (general figure 26 ms)
n = Number of the safe modules/submodules installed in the system
The following example shows a system with three locking modules. In two of the locking modules there is one submodule
with a safety function installed. There is therefore a total of 5 safe modules/submodules.
System layout
Item
Module/submodule
Safety
function?
Processing
time T
P
Latency time t
L
2
3
4
5
6
7
ML2C
ML1C
1
1
Bus module MBM
-
250 ms
-
2
Locking module MGB2-L
yes
-
26 ms
3
Locking module MGB2-L
yes
-
26 ms
4
Submodule MSM with emergency stop safety function
yes
-
26 ms
5
Interlocking module MGB2-I
yes
-
26 ms
6
Submodule MSM
no
-
-
7
Submodule MSM with emergency stop safety function
yes
-
26 ms
These data yield the following calculation:
T
Risk
= 250 ms + 5 x 26 ms = 380 ms
The risk time for any safe function in the system is 380 ms.
