Functional Failure

Last updated: August 4, 2014

What Does Functional Failure Mean?

Functional failure is the inability of a system to meet a specified performance standard.

A complete loss of function is clearly functional failure. However, a functional failure also includes the inability to function at the level of performance that has been specified as satisfactory. Functional failure can lead to corrosion and catastrophic damage to the system.


Corrosionpedia Explains Functional Failure

In order to define functional failure for any component or system, a clear understanding of its functions is required. It is extremely important to determine all the functions that are significant in a given operational context, since it is only in these terms that its functional failure can be defined.

Basic functional failure types include:

  • Crisis:
    • Deviation is sudden and severe
    • Usually demands immediate attention

  • Chronic:
    • Deviation is not severe
    • Deviation is often viewed as a normal part of operations
    • Occurs routinely
    • Often sneaks under the radar

Functional failure can originate from:

  • Design errors
  • Manufacturing errors
  • Installation & commissioning errors
  • Operating & maintenance errors

Hidden failures are functional failures that share two very important characteristics. Firstly, they can’t be seen by the operators during normal operation of the system. Secondly, they are usually in items that protect people from severe injury or death, or protect equipment from severe damage. The combination of those two characteristics means that there must be some sort of hidden failure-finding task in place as part of any maintenance strategy. It is important to remember that the longer the hidden loss of function is present, the higher the risk of catastrophic consequences.


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