Maintenance Guidelines - Siemens SIMATIC S7 Functional Safety Manual

Fail-Safe CPU and signal module (SM) installation

4.4 Maintenance guidelines

4.4 Maintenance guidelines
Each S7-1200 module and CPU is a factory-assembled unit that contains no user
replaceable components or repairable components, except for removeable terminal blocks
and memory cards. Maintenance of an S7-1200 system consists of the following:
● Observation and response to diagnostic reports from the S7-1200
● Replacement of modules with identified failures
● Replacement of modules at 20 years of operating life
● Inspection and monitoring of the installation environment to ensure continued adherence
to all specified operating conditions, to include the following:
– S7-1200 and field wiring electrically and mechanically secure
– Ventilation continued as designed for installation
– Continued protection from moisture, dust, and conductive contamination
– Voltage of connected circuits in proper range
– Operating temperature of equipment in proper range
The fail-safe signal modules (SMs) monitor the 24 VDC power supplied at L+/M and
passivate the module on voltage out-of-range.
The fail-safe SMs monitor internal temperature and passivate the SM on temperature out-of-
range.
You must assess your installation safety and determine if you require additional voltage and
temperature monitoring.
Note
Associated equipment including sensors, actuators, circuit breakers, and surge protectors
are subject to wear and typically require periodic inspections or proof tests according to
manufacturer's instructions or standards to maintain a consistent level of safety integrity.
User cleaning or decontamination of an S7-1200: Use vacuum or a dry cloth applied to the
outside of the assembly only. High pressure forced air can damage components or carry
entrained contaminants. Liquid cleaners of any kind can deposit conductive contamination
onto the circuit boards.
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S7-1200 Functional Safety Manual
Manual, 02/2015, A5E03470344-AA