What is Common Cause Failure?
Common cause failure is a single cause that makes redundant channels fail together, such as a shared impulse line, wrong calibration or environment.
Common Cause Failure Explained
Redundancy only helps if channels fail independently. Shared tapping points, the same calibration error or one power supply can defeat it.
The beta factor model assumes a fraction β of failures are common cause; typical values are a few percent to 10 % depending on separation and diversity.
Common Cause Failure Formula
| β | common cause factor |
| λDU | dangerous undetected rate of one channel |
Calculators for Common Cause Failure
Frequently Asked Questions
What is Common Cause Failure?
Common cause failure is a single cause that makes redundant channels fail together, such as a shared impulse line, wrong calibration or environment.
How do I reduce common cause?
Separate tapping points, diverse technology, staggered testing and separate power and routing.
Does diversity eliminate CCF?
It reduces it but shared environment and procedures still matter.
Learn more on the blog
What is SIL (safety integrity level)
A practical guide on instrumentationblog.in with more detail on common cause failure and how it is applied on real plants.
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