Safety Integrated - Industry - Siemens

Ex. No.
1
Emergency Stop with Acknowledgement in Category 4
acc. to EN 954-1
Automation Function
Description of the functionality
If persons (e.g. in manufacturing engineering) work in the vicinity
of machines, they have to be adequately protected by
technical devices. Emergency stop is an additional safety
measure in order to protect people and plants from hazards.
Emergency stop must have priority over all other functionalities.
Devices, functional aspects and basic design principles of the
emergency stop push button are laid down in EN 418, and additionally,
EN 60204-1 : 1997 must be observed.
In this example, an actuated emergency stop push button disables
an output of a failsafe digital output module at which
e.g. a hazardous machine is operated. All other outputs of this
output module remain in their current status. Prior to a renewed
machine start the emergency stop push button must
be reset manually. This requires an acknowledgement signal.
The flowchart below illustrates the relation.
Y
Start
"Machine" STOP
Emergency
stop pressed?
N
Acknowledgement
Y
Emergency
stop pressed?
N
START?
Y
Emergency
stop pressed?
N
"Machine" ON
Emergency
stop pressed?
N
170 Functional Example No. AS-FE-I-001-V10-EN
Y
N
Y
N
Y
G_FB_XX_076
Note
In this example, the hazardous machine is simulated by
an indicator light. When using other actuators than this
indicator light, safe switching-off function of the loads
including signal feedback is to be supplemented.
For calculating the max. reaction time of your F-system please
use the Excel file (Cotia table), which is available for S7 Distributed
Safety V 5.3. This file is available on the internet:
http://support.automation.siemens.com/WW/view/en/
19138505.
Prefabricated blocks and network templates from the Distributed
Safety library were used to implement the emergency
stop functionality. Alternatively, you can also access the respective
block from the Distributed Safety library (from Distributed
Safety V5.3) for the realization.
Advantages/customer benefits
■ Wiring reduced to a minimum due to use of failsafe S7-CPU
and distributed I/O. The more safety functions are implemented,
the more useful this advantage is.
■ Only one S7-CPU is required, since within the CPU failsafe
and standard program parts run on a coexistent basis.
■ Programming the failsafe program with STEP 7 engineering
tools.
■ Editor user interface within the failsafe program is used as
familiar from STEP 7.