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Failure

The loss of function, value or utility of an asset under stated conditions. The loss may vary by degree:


Classification
There are numerous methods for classifying failure. Listed below are some examples

Webster’s dictionary defines failure as “a state of inability to perform a normal function”. Nolan and Heap defined Failure as “an unsatisfactory condition”.

  • A.  Failure Modes (water, fatigue, wear and tear, etc)
  • B.  Failure Detection
  • B.  Failure Effects (eg., outage)
  • C.  Failure Grades (eg., partial, systemic, etc)
  • D.  Failure Criticality (eg., catastrophic, negligible, etc)
  • E.  Failure paths (eg., P-F interval)
  • F.  Failure Analysis (eg., FMEA, FMECA, degradation curves, survivor curves


B.  Failure Detection
  • Ferrography
  • Thermography
  • Ultrasound
  • Vibration Analysis
  • Wear Debris Analysis


E.  Failure Paths
Listed below are some of the key concepts associated with the paths of failure of an asset:


D.  Failure Criticality
Listed below are some of the key concepts associated with the criticality of failure:

C.  Grades of Failure
Listed below are some concepts associated with different degrees and manifestations of failure.

Partial failure is reflected in 


Failure Analysis
A study by
Nolan and Heap identified six failure patterns as follows:
A study at Iowa University identified survivor curves with classes of 31 Iowa Curves, as follows:

Modeling and Predicting Failure and the Failure Process

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Fig. Samples of the result of deferred maintenance resulting from a variety of different forms of failure.


The risk spectrum extending along the P-F interval to illustrate the varying strategies in the Pre-P and Pre-F periods. For example, a shift from Time-Based Maintenance (TbM) to Condition-Based Maintenance (CbM)
Fig. The risk spectrum extending along the P-F interval.


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Fig. Excessive vegetation growth on roof is an example of extrinsic failure resulting from deferred maintenance and lack of care by the owner..

See also:


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