Requirements For Sensors And Actuators For Fail-Safe Modules - Siemens SIMATIC ET 200SP System Manual

Wiring
5.2 Additional rules and regulations for the operation of the ET 200SP with fail-safe modules
Power supply requirements for compliance with NAMUR recommendations
Note
To ensure adherence to the NAMUR recommendation NE 21, IEC 61131-2 and EN 298,
only use power packs/power supply units (230 V AC → 24 V DC) with a mains buffering time
of at least 20 ms. The latest up-to-date information on PS components is available on the
Internet (https://mall.industry.siemens.com).
These requirements, of course, also apply to power packs/power supply units not
constructed using ET 200SP / S7-300-/400-/1500 technology.
5.2.2

Requirements for sensors and actuators for fail-safe modules

General requirements for sensors and actuators
Note the following important warning regarding safety-related use of sensors and actuators:
Note that instrumentation with sensors and actuators bears a considerable safety
responsibility. Also bear in mind that sensors and actuators generally do not have proof-test
intervals of 20 years as defined in IEC 61508:2010 without considerable loss of safety.
The probability of hazardous faults and the rate of hazardous faults of safety functions must
comply with an SIL-defined high limit. A listing of values achieved by F-modules in the
technical specifications of the F-modules is available under "Fail-safe performance
characteristics".
To achieve the required safety class, suitably qualified sensors and actuators are
necessary.
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WARNING
Distributed I/O system
System Manual, 12/2015, A5E03576849-AF