Safety Integrated - Industry - Siemens

Safety Door without Guard Locking in Category 4
acc. to EN 954-1
Automation Function
Description of the functionality
In general, two types of safety doors can be used. In case of
the type with guard locking, the door is held in a position
switch during the potential hazard. In case of hazardous machine
motions with short braking times, position switches
without tumbler are often used. The example introduced
here shows how the requirements of Safety Category 4 can be
met with the latter variant according to EN 954 : 1996.
Actuator
Position switch
Protective Door opened Protective door closed
The requirements of Safety Category 4 are met due to use of
2 SIGUARD position switches (or a magnetic switch) with separate
actuators (redundancy for mechanical parts). The position
switch is installed form fit at the closing edge on the fixed
part, the actuator is installed at the moving door.
The position switch features positive-opening contacts which
are directly connected to the failsafe digital input module of
the ET 200S I/O system. The commands acquired that way are
evaluated in the safety program of the S7-CPU. The safety program
of the S7-CPU ensures that:
■ prior to each start, acknowledgement is necessary if the
application has been stopped by opening the safety door
■ if only one position switch indicates an open safety door, it
must be completely opened prior to a restart (open/close
safety door, acknowledge, start)
■ the application can only be started if the safety door is
closed
■ the application stops if the safety door is opened during
operation or as soon as a contact of the position switch
responds
In this example, the hazardous machine is simulated by an indicator
light which is connected to a failsafe digital output
module of the ET 200S I/O system. In this document, the designation
"machine" refers to this indicator light.
G_FB_XX_106
Warning!
When using different actuators, the feedback circuits
have to be integrated and evaluated by the user. You
find more information about the readback signals in
the Safety Functional Example no. AS-FE-I-007-V10-
EN.
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
The diagram below illustrates the conditions for a start or a
stop of the "machine".
G_FB_XX_107
Start
Button for
"Machine" STOP
pressed?
N
Actuator
in each position
switch?
Y
Button for
acknowledgement
pressed?
Y
Button for
"Machine" START
pressed?
Y
"Machine" ON
Y
N
N
N
Door open
"Machine" ON?
Functional Example No. AS-FE-I-004-V10-EN 207
Y
N
"Machine" OFF
Ex. No.
4