What are the lessons of the D-I-P-F Curve and the Failure Patterns?

With the revision of Uptime? Elements Reliability Framework and Asset Management System one of the BIG changes was the addition of the D-I-P-F curve (Design-Installation-Potential Failure-Failure).

If you plan to attend IMC-2017 the 32nd International Maintenance Conference you will see Doug Plucknette, Author of RCM Blitz and Worldwide RCM Leader at Allied Reliability Group and myself deliver the opening keynote on this very topic.

Doug, who originally extended the P to F Curve concept in his Uptime Magazine article titled The Introduction of the I-P Interval started a long set of conversations from those who thought it was brilliant and those who thought it was not worthy of discussion. I happened to be in the first category and enthusiastically embraced the concepts it evoked.

For reference, the original P to F curve that was published in Nowlan and Heap's original report in 1978 is shown below

Point P (marked C in the drawing above) = Potential Failure: An identifiable physical condition that indicates functional failure is imminent.

Point F (marked D in the drawing above) = Functional Failure: The inability for an item (or the equipment containing it) to meet a specified performance standard.

P-F Interval: The time it takes for an item to functionally fail once a potential failure has been detected.

One of the most popular Google images for the P to F curve Power Point Presentations (shown below) is this one created by a talented Allied Reliability graphics team back in the early 2000's and often borrowed, seldom attributed (thank you Allied).

According to RCM Blitz Author Doug Plucknette states "As companies look to introduce On-Condition Maintenance (ACM/CbM/PdM/) tasks, they are almost always introduced to the P-F Curve, which helps to illustrate the benefits of detecting potential failures in the effort to improve reliability and reduce failure costs through planning and scheduling.

While the P-F Curve does an effective job at making this point, it only illustrates a portion of what an organization can do to achieve and sustain reliability."

While one could celebrate that this company successfully detected and responded to three potential failures over a short period of time and avoided the costly secondary damage associated with each failure, Doug states that he urges them to question why each failure occurred.

The most important things we need to understand about the P-F Curve and the Saw Tooth P-F Curve is this;

Detecting potential failure is simply not enough today to consider your PdM program a success. For each detected potential failure we must also determine the specific cause of failure. We need to know; What has caused this potential failure and most important, can this cause be eliminated?

While the Saw Tooth P-F Curve still effectively eliminates running costly rotating equipment to failure, it can lull maintenance managers into the illusion that Predictive Maintenance is all maintenance has to offer regarding these types of failures.

The idea is to move to the left of the P to F curve into the I-P precision domain with proper installation, commissioning, precision alignment and balancing, precision lubrication, proper torquing, defect elimination - in other words - do not permit the defect to enter into the system through your own poor practices so that you need to detect the potential failure with advanced vibration analysis later to prevent a functional failure!

The answer to where reliability is made is design. The answer to how much the cost of failure totals has more to do with when you decide to remove the failure mode!

That is a story for a different day!

What lessons do you take from the D-I-P-F Curve? Will you share them here for the benefit of all us to advance reliability and asset management?

Watch Doug and I deliver the IMC-2017 Keynote here

If you want clean copies of the D-I-P-F graphic click here