BBH SMX Series - Consideration of Systematic Failures

Installation manual
HB-37420-810-01-25F-EN SMX100 Installation manual.docx Page 244 of 260
Version: 25F
12.3.4.3 Consideration of systematic failures
Within the hardware specification one must also consider systematic failures.
Examples for measures against systematic failures:
Power drop during operation. If this causes a danger, a power drop must be considered
a operating status. The SRP/CD must be able to cope with this condition, so that a safe state
is maintained.
Measures against systematic failures acc. to appendix G DIN EN ISO 13849-9
Source BGIA Report 2/2008
Fault exclusions:
If fault exclusions are made for certain devices or system components, these must be
individually nominated and specified.
Fault exclusions may be e.g. mech. shaft breakage, sticking of switching contacts, short-
circuits in cables and lines, etc.
The permissibility of fault exclusions must be justified, e.g. by referencing to permissible fault
exclusions acc. to applicable standards, e.g. EN ISO 13849-1)
If these fault exclusions require special measures, these must be mentioned.
Examples for fault exclusions and associated measures:
Positive connection for mechanical shaft connections
Dimensioning based on sufficient theoretical bases in case of breakage of components in the
safety chain.
Positively guided connection with forced separation in case of sticking of switching contacts.
Protected routing within switchgear in case of short-circuit in cables and lines.
Causes of systematic
failures
Before commissioning, e.g.:
- Manufacturing faults
- Fault in development (incorrect
selection, incorrect
dimensioning, faulty software)
- Fault in integration (incorrect
selection, faulty wiring)
after commissioning, e.g.:
- Power failure/fluctuations
- environmental influences
- Wear, overloading
- Faulty maintenance
Measures for the avoidance of failures
Black-Box test
Automatic testing
Redundant hardware/hardware diversity
Desmodromic operation mode
Contacts with positive guidance/ with forced
opening
Directed failures
Over-dimensioning
Draft for the control of environment related influences
Draft for the control of voltage related influences
Principle of power supply shut-down
additionally:
"Secure" data communication processes (bus systems)
Monitoring of program run (in case of software)
Correct selection, arrangement, assembly, installation
Correct dimensioning and design of shape
Appropriate materials and suitable manufacture
Function test
Project management, documentation
Component in accordance with standard with defined types of failure
Resistance against determined environmental conditions
Component with compatible operating characteristics
INTEGRATION:
additionally:
Measures for the control of failures