Siemens S7-300 Installation Manual page 215

6SOLWWLQJ WKH JURXS LQWR VDIHW\UHOHYDQW DUHDV DQG DUHDV ZKLFK DUH QRW VDIHW\
UHOHYDQW
Most plants contain equipment performing safety-relevant operations (e.g.
EMERGENCY-OFF switch, protective gates, two-hand controls). To avoid the need
to examine the entire controller from the aspect of safety, WKH FRQWUROOHU LV XVXDOO\
GLYLGHG LQWR DQ DUHD WKDW LV VDIHW\UHOHYDQW DQG DQ DUHD WKDW LV QRW VDIHW\
UHOHYDQW In the non-safety-related area, no special demands are placed on the
safety of the control equipment because any failure in the electronics will have no
effect on the safety of the installation. In the safety-relevant area, however, it is
only allowed to operate controllers or circuits compliant with corresponding
regulations.
The following divisions are common in practical situations:
• For control equipment with few safety-related functions (e.g. machine controls)
The conventional PLC is responsible for machine control, whereas safety-
related functions are implemented with a fail-safe mini PLC (e.g. S5-95F).
• For controllers with balanced areas (e.g. chemical installations, cable cars)
The non-secure area is implemented with a conventional PLC, while the secure
area requires a tested, fail-safe controller (S7-300F, S7-400F, S7-400FH, S5-
115F or several S5-95Fs).
The entire installation is implemented with a fail-safe control system.
• For control equipment with mainly safety-relevant functions (e.g. burner control
systems)
The entire control system is implemented with fail-safe technology.
,PSRUWDQW ,QIRUPDWLRQ
The instructions in the operating manual MUST be followed, even if the electronic
control equipment has been configured for maximum design safety - e.g. with a
multi-channel structure. Incorrect handling can render measures intended to
prevent dangerous faults ineffective, or generate additional sources of danger.
S7-300 Automation System, Hardware and Installation: CPU 312IFM - 318-2 DP
A5E00203919-01
$SSHQGL[
12-29