Siemens SINAMICS S120 System Manual page 44

Configuration
3.3 Configuring the hydraulics
Principle of operation
For the HLA module, the STO safety function corresponds to shutting off a safety-relevant
shutoff valve.
The figure below shows the interconnection of a shutoff valve (based on the example of one
axis) and the most important elements for its operation and testing:
Figure 3-5
The shutoff valve controls the infeed to the hydraulic circuit. The shutoff valve is controlled
via an F-DO of the HLA module, which in turn is monitored by the safety functions.
The F-DO has the following properties:
● The F-DO is designed to be P/P switching
● The F-DO+ is an FET, the F-DO- is a semiconductor switch with an additional short-
circuit protection function
● The voltages behind the two switches can be read in by the software (digital) and
evaluated for the purposes of diagnosing the shut-off path (diagnostics signals Diag DO+
and Diag DO-).
Every time STO is selected/deselected, the F-DO undergoes a dynamization process (check
of Diag DO+ and Diag DO- when switching F-DO+ and F-DO-).
44
Interconnection of the shutoff valve
System Manual, 04/2015, 6SL3097-4BA00-0BP1
Hydraulic Drive