Maintenance Phoenix

Abnormalities vs Failures

Posted by Mike Gehloff on Mar 11, 2014 2:17:37 PM
Mike Gehloff

What better way to waste an afternoon than to debate which came first the chicken or the egg? reliability failures vs abnormalities

One thing that can not be debated however is the fact that abnormalities come before failures.
This is a fact.

What we notice:
We are conditioned early on to react to failures; the loss of function, why did the lights go out?, why did my car stop working?, but the abnormalities that lead to these failures often fly below our radar.   This ability to change our thinking or our refine our attention to look for abnormalities is a first critical step in transforming from a reactive to proactive organization.   Reactive organizations attribute their performance to bad luck, proactive organizations make their own luck.

Definitions: Abnormality and Failure:
So what is the difference between an abnormality and a failure?  First of all, I prefer to use the phrase “functional failure” rather than simply “failure.”  I have to really concentrate and force myself to use these words, but it has an important effect on my thinking and the thinking of those around me.  To me, Failure seems to be an arbitrary word open to interpretation.
Loss of function or functional failure on the other hand is quite clear, I can no longer do what I desire to do.

  • If the light bulb goes out, then I can no longer read my book – loss of function.
  • If the impeller wears on my pump and can no longer produce my product in the required quantity – loss of function.
  • If my tire goes flat and I can no longer drive my car at full speed – loss of function.

In each case if we start with that condition that we desire, the loss of this ability or function becomes quite clear.

Abnormalities, on the other hand, are the clues that our assets provide to us that something is wrong and that we are on that pathway to loosing our desired function.

  • A baby crying. The baby is indicating that something is wrong, but there is no obvious problem.

As caretakers of our assets (our babies) it is our job to do something about it; proactively, before the functional failure occurs.

Functional Failures, Abnormalities and the P-F Curve Explained:
This pathway to functional failure, and the abnormalities that mark this path is best described by the P-F curve shown here.

The definition and meaning behind the P-F Curve is quite simple and powerful at the same time.  Let’s review the P-F CurveP-F Curve in detail:

  • The vertical axis represents our equipment condition while the horizontal axis represents time.
    • The higher the equipment condition the better.
  • The first point on the graph (upper left hand corner) is labeled “the point where the failure starts to occur.”  Lets consider this point P.

Example: Imagine that we forget to lubricate the bearings on an electric motor.  Eventually all of the grease will evaporate out, leaving metal to metal contact.   This is point P in this example.

The equipment (asset) starts to degrade, losing its condition slowly at first, but then increasing in speed as time continues on.   As this process continues, the equipment provides us with clues that inform us of what is happening – at first very subtle clues, but increasing in magnitude (and our urgency I hope) as the process continue.  These clues are the abnormalities we speak of.
If we do not act proactively to the abnormalities, we will reach the point labeled “equipment fails here.”  This is point F or the point of Functional Failure.
Because we have failed to react proactively to the abnormalities, we will now have to react to the functional failure – the choice has been made for us!

Action Taken for Abnormalities:
What should we do with abnormalities?  We must report them in an official way as soon as we see them.  When I say reporting in an official way, I mean something like putting a work request into our CMMS system, or using an abnormality tag that is part of our Operator Care process.

Note: Tugs on the shirtsleeve, emails, phone calls, sticky notes; none of these count.   This collection of official notifications represent what we know to be our backlog, and a full and rich backlog is critical to our proactive approach to maintenance.

I talk to many people who tell me, I only want people to report the “important or critical problems.”
Guess what, today's unimportant problem will quickly become tomorrow’s important one, the P-F curve illustrates this perfectly.  Better to have a solid reporting system, a simple method to prioritize work so we are attacking the most important abnormalities first, as well as a robust and visual means to communicate our progress to everyone who participates in the process (managers, and technicians, operations and maintenance).

If we do not report abnormalities early, or strive to report only those ambiguous “really important ones” we are selling ourselves short. When we fail to report abnormalities early, we loose the ability to address them early.

The Takeaway:
The most important thing to remember is this:  All abnormalities eventually become functional failures.   It is our choice to address the on our terms (proactively) or when the equipment demands it (reactively).

Tags: P-F Curve, Asset Failure, asset reliability, asset management, Asset Reliability, Evaluate PM, maintenance best practices, PF Curve, Reliability Based Maintenance

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