Root Cause Analysis Without Verification is Conventional Wisdom

Root cause analyses are done every day all over the world. Organizations do root cause analysis because it is good business. From an explosion in an auto parts plant to the wrong prescription being given to a patient. Events such as these can have dramatic monetary, physical and psychological effects on an organization. To solve problems down to the true roots will reduce or eliminate the cause from ever happening again.

In many cases we interview the witnesses, collect some data, and get all of our experts together in a room to brainstorm the possibilities of how the incident could have occurred. When all the participants have come to a consensus on the most likely causes they begin to collaborate solutions that will eliminate the causes. With the solutions complete a plan to implement is developed, presented to the appropriate parties, and a paper is written to document the analysis. This technique of solving problems is usually ineffective in getting to the true root causes. In many cases you can get to the physical roots of a problem, this is usually the component that was broken. When you stop at the component failure you have completed a failure analysis not a root cause analysis.

I was recently talking with a client about root cause analysis. He was telling me that some of the problems they were encountering had clear solutions based on the data collected. He offered an example on a roller in the facility that had a hydraulic arm break. The reason for the failure was derived from interviews collected in the field. The hydraulic arm failed because the pillow block bearing bolts broke the bearing housing. Because of the production requirements the housing was welded in the field to maintain rate. Several weeks later the hydraulic arm on the opposite end failed. The determination was that it failed because the weld job left the hydraulic arm misaligned causing the opposite arm to operate in a bind. I thought that this was an interesting summation of the problem. I asked if they had looked into all the possibilities and the reply was that the evidence was so clear cut that there was no need to do a complete root cause analysis. I never heard him question why did the bearing-housing break in the first place? The analysis was based completely around the apparent causes. The solution will probably take care of the problem for a while but unless the true roots are discovered it will show up again.

There are ways that you can avoid a repeat of the same failure mechanism on the same piece of equipment. In the reliability world it’s called verification of the hypothesis. The PROACT® method of root cause analysis forces the user to look at all the possibilities as well as finding ways to verify each hypothesis using available technologies such as vibration analysis, metallurgical review, observation, eddy current testing, etc. There are enough technologies available that most hypotheses can be verified easily.

I have found that for material failures such as bearings, belts, fasteners, plastic conveyer parts, shafts, couplings, and many other components that the best and fastest approach to verification is to know how to read fractured surfaces. This skill can be acquired through trained professionals who teach fractology or you can hire these people to evaluate your failed parts. Knowing how to do this can reduce the time to do the root cause analysis because it leads you to understanding the physics behind the failure. Once the physics is clear the rest falls into place.