Expanding the P-F Curve

Maintenance has always seemed simple to be a simple process to me, understand what you want your system to do, determine the ways it can fail, and develop a series of tasks to mitigate the effects of each failure.

Develop a plan and do it. Some like to believe it's common sense and others, well they have a difficult time getting their arms around the concept of a sound maintenance strategy.

Several years ago I was instructing the principals of the Potential Failure Curve to a new class of RCM Blitz Facilitators and in this class I had one of those students that every teacher loves. The student who will not stop asking questions until he is 100% sure he understands the material. In this particular session we were discussing the importance of sticking to the determined interval of each on-condition maintenance task and to illustrate this point I used an entire 8 foot wide white board and drew a 6 foot long straight line that then dropped into a P-F curve. As with any P-F curve I labeled the y-axis resistance to failure, and the x-axis as time. Along the x-axis I put one year for every six inches with point P being at 12 years. To make sure my student with all the questions understood the point I was about to make I asked him, if this were the P-F curve for the bearing on the centrifugal pump in our example, how often would you perform vibration analysis?

He answered correctly stating "Every month"!

Being the RCM instructor/facilitator that I am, I then asked why?

"Because we don't know when point P will occur, it could happen at any time along that long line you just drew".

Correct again! Now a more important question, could we ever expect to see such a long time line between installation and potential failure, if so how do we accomplish that?

Answer: "Yes but only if you first understand your failure modes and use the tools necessary to eliminate them"!

The above discussion resulted in what I refer to today as the complete P-F curve that includes the I-P interval and the importance of Reliability Tools and Precision maintenance. If you are interested in increasing the interval between installation and failures contact Allied Reliability and sign up for RCM Blitz training.

The Complete P-F curve will be presented at IMC2008 complete with a case study.