Siemens SINUMERIK 840D sl Function Manual page 83

A forced checking procedure must be used, e.g. for components that are required to stop a
process (e.g. contactors and power semiconductors) - the so-called switch-off signal path and
for the shutdown condition. Generally, it is not possible to test a shutdown condition, e.g.
violation of a limit value criterion, using other methods such as e.g. crosswise data comparison,
when the machine is in an acceptable (good) condition. This also applies to errors along the
entire switch-off signal path including associated hardware and software and circuit-breakers.
By integrating a test stop every eight hours with a comparison and expected status, faults can
also be detected when the machine is in an acceptable (good) condition...."
Comment: Acceptable (good) condition means that there are no machine faults that are
apparent to the operator
Comment: For Safety Integrated, a forced checking procedure interval of one year is
permissible
Forced checking procedure with Safety Integrated
The forced checking procedure is used to detect faults/errors in the software and hardware of
the two monitoring channels. In order to do this, the safety-related parts in both channels must
be processed at least once during a defined period in all safety-related branches. Any faults/
errors in the monitoring channel would cause deviations and will be detected by the cross-wise
data comparison.
For Safety Integrated, the forced checking procedure interval is max. 1 year. This involves
components from the SINUMERIK 840D sl / SINAMICS S120 system. Possible requirements
relating to shorter forced checking procedure intervals of safety-related components (e.g.
PROFIsafe I/O modules, sensors such as e.g. Emergency Stop buttons, actuators such as
e.g. brakes, etc.) are not influenced.
The forced checking procedure must be initiated by the user or integrated in the process as
an automatic procedure, e.g.:
● When the axes are stationary after the system has been powered-up
● When the protective door is opened
● In defined cycles (e.g. every 8 hours. The maximum permissible is once per year)
● In the automatic mode, dependent on the time and event
The forced checking procedure also includes testing the safety-related sensors and actuators
at the safety-related inputs/outputs. In this case, the entire circuit including the Safe
Safety Integrated
Function Manual, 12/2017, 6FC5397-4BP40-6BA1
Basics regarding the safety functions integrated in the system/drive
6.3 Forced checking procedure
83