Safety Of Electronic Control Equipment - Siemens Simatic S7-300 CPU 31xC Series Installation And Operating Instructions Manual

Appendix
A.4 Safety of electronic control equipment
A.4

Safety of electronic control equipment

Introduction
The notes below apply regardless of the type or manufacturer of the electronic control.
Reliability
Maximum reliability of SIMATIC devices and components is achieved by implementing
extensive and cost-effective measures during development and manufacture:
This includes the following:
• Use of high-quality components;
• Worst-case design of all circuits;
• Systematic and computer-aided testing of all components;
• Burn-in of all large-scale integrated circuits (e.g. processors, memory, etc.);
• Measures preventing static charge when handling MOS ICs;
• Visual checks at different stages of manufacture;
• Continuous heat-run test at elevated ambient temperature over a period of several days;
• Careful computer-controlled final testing;
• Statistical evaluation of all returned systems and components to enable the immediate
• Monitoring of major control components, using on-line tests (cyclic interrupt for the CPU,
These measures are referred to as basic measures.
Risks
In all cases where the occurrence of failures can result in material damage or injury to
persons, special measures must be taken to enhance the safety of the installation – and
therefore also of the situation. System-specific and special regulations exist for such
applications. They must be observed on installing the control system (e.g. VDE 0116 for
burner control systems).
For electronic control equipment with a safety function, the measures that have to be taken
to prevent or rectify faults are based on the risks involved in the installation. As of a certain
degree of hazard the basic measures mentioned above are no longer sufficient. Additional
measures must be implemented and approved for the controller.
Important information
The instructions in the operating manual must be followed exactly. Incorrect handling can
render measures intended to prevent dangerous faults ineffective, or generate additional
sources of danger.
A-30
initiation of suitable corrective measures;
etc.).
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05