Definition:
Beta Factor (β) is the method for quantifying the contribution of Common Cause Failures (CCF) in redundant systems. It is the mathematical representation of CCF. It is the fraction of all failures that are CCF related. Therefore, 1-β represents the independent failures.
This term is part of PFDavg calculations in all its various forms. Note that failure rate values include both common cause and independent.
Key Points:
- Common cause failures occur when multiple components fail simultaneously due to a shared cause.
- Beta factor represents the ratio of total failures attributable to common cause.
Example:
If two redundant pressure sensors fail together due to a power supply fault, this is treated as a common cause failure.
See Also: common cause failure, beta factor in depth article
Cited Source:
- IEC 61508-6:2010, Annex D.