Safety Considerations; Operator Safety Switch - Siemens SIMATIC TI525 Hardware And Installation Manual

2.2

SAFETY CONSIDERATIONS

Pre-installation planning and site preparation must include consideration of
hazards to personnel during a system failure. The equipment connected to the
TI525/TI535 PLC should include interlocks and safety switches to prevent
operation during a system failure. Although the specific steps depend on the
application, the general precautions include the following:
D
Provide a means for disconnecting power—independent of the
PLC—from the output loads when a machine is not operating, or when
it is necessary for the operator to reach into the machine. Power must be
removed by a non-semiconductor switch or a physically-wired relay
contact, placed to interrupt power to the output. It is not sufficient to
rely solely on the PLC for this function. Figure 2-1 illustrates an

operator safety switch.

Output
Module
Output points from
the programmable controller
Hardware and Installation User Manual
Artisan Scientific - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisan-scientific.com Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
PRE-INSTALLATION
Relay contacts or limit switches
open when operator must
reach into machine.
Figure 2-1 Operator Safety Switch
2-4
User-supplied
critical loads
which could
cause injury
Loads which
could not
cause injury