Definition
A functional failure is the state in which an asset no longer performs a function to the standard required: a pump can no longer deliver the required flow, a sensor no longer reports within tolerance. It is defined against a specific performance standard and is the broader state that a failure mode describes the specific manner of.
Key facts
- Defined against a specific performance standard for one function: an asset can meet some functions while functionally failing another.
- The broader state (function not met), of which a failure mode is the specific, observable way it occurred.
- Central to RCM analysis: RCM starts by defining each function and its performance standard before identifying possible functional failures.
- Can be total (complete loss) or partial (reduced performance still below the required standard).
What does Functional failure reveal about failures?
A functional failure means an asset has stopped performing a defined function to its required standard (whether that standard is a flow rate, an accuracy tolerance, a structural capacity, or a safety response time) and applies specifically to that function, not necessarily the entire asset.
How do teams use Functional failure in failure analysis?
Functional failure is the broader condition: the function is no longer met. Failure mode is the specific, observable way that condition manifests: a pump's functional failure to deliver required flow could occur through the failure mode of impeller wear, a blocked line, or a seized bearing, each a different specific manner of the same broader functional failure.
FAQ
Frequently asked questions
When does an asset no longer meet its required function?
A functional failure occurs when an asset stops performing a specific function to its required performance standard, regardless of the particular manner (the failure mode) in which that happened.
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