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Application 13849-1 Step 5: Defining Common Cause Failures
Common Cause Failures CCF
No.
Measure against CCF
Points S
1
Separation/ Segregation
Physical separation between signal paths:
15
separation in wiring/piping, sufficient clearances and creepage distances on printed-circuit boards.
2
Diversity
Different technologies/design or physical principles are used,
20
for example:
first channel programmable electronic and second channel hardwired, kind of initiation,
pressure and temperature, Measuring of distance and pressure,
digital and analogue. Components of different manufacturers.
3
Design/application/experience
3.1 Protection against over-voltage, over-pressure, over-current, etc.
15
3.2 Components used are well-tried and attention has been paid
5
to the ambient conditions
4
Assessment/analysis
Are the results of a failure mode and effect analysis taken into account
5
to avoid common-cause failuresin design.
5
Competence/training
Have designers/maintainers been trained to understand the causes and consequences
5
of common-cause failures?
6
Environmental
6.1 Electromagnetic Compatibility (EMC)
25
Has the system been checked for electromagnetic immunity,
e.g. as specified inrelevant standards against CCF?
6.2 Other influences
10
Have the requirements for immunity to all relevant environmental influences such as,
temperature, shock, vibration, humidity
(e.g. as specified in relevant standards) been considered?
Total
[max. possible 100]
Measures to avoid CCF
Total points S
Requirements reached
65% or better
Process failed; select additional measures
less than 65%
Which common cause failures
can arise? The measures against
these failures should be
recorded in a grid.
For each of the listed measures,
either all the points are assigned
or none. If a measure is only
partially fulfilled, the number of
points is zero.