Requirements Of Sensors And Actuators For Fail-Safe Modules - Siemens SIMATIC S7-1500 System Manual

Wiring
5.2 Additional rules and regulations for operation of the S7-1500/ET 200MP with fail-safe modules
Power supply requirements in case of voltage interruptions
Not e
Always use power packs or power supply units (24 VDC) with a mains buffering time of at
least 20 ms to ensure adherence to IEC 61131-2.
Also take into consideration the respective requirements of your product standards regarding
mains buffering time.
Information on the power supply components is available on the Internet
(https://mall.industry.siemens.com).
5.2.2

Requirements of sensors and actuators for fail-safe modules

General requirements for s ensors 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 s afety
res ponsibility. Also bear in mind that sensors and actuators generally do not have a service
life 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 respective safety class, suitably qualified sensors and actuators are
necessary.
Additional sensor requirements
General rule: A single-channel sensor is sufficient to achieve SIL3/Cat.3/PLd. However, to
achieve SIL3/Cat.3/PLd with a single-channel sensor, the sensor itself must be
SIL3/Cat.3/PLd-capable; otherwise, the sensor must be connected via two channels to
achieve this safety level.
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Automation system
System Manual, 09/2016, A5E03461182-AD