Case Study: Root Cause on Seal Failure in Refinery

I have heard one manager in a plant that has stipulated a maximum of two hours for an Root Cause Analysis to be conducted in his organisation. Another expects at least “brainstormed” solutions before the conclusion of day one – within 6 or 7 hours.  It is not uncommon for a draft report to be required within 48 hours of the RCA. The following three tips may assist to meet tight deadlines and when time expectations are short. One advantage of the Apollo RCA process is that it is a fast process but the “driver” has to be on the ball to achieve the desired outcomes – effective solutions.

I was recently engaged by a client to conduct failure analysis on a large (and expensive) hydraulic cylinder off an excavator. This hydraulic cylinder had been changed-out due to leaking rod seals after achieving only half of its expected service life. Inspection revealed that apart from the rod seals, which had failed as a result of the 'diesel effect', the other parts of the hydraulic cylinder were in serviceable condition.

Fatigue is a failure mode that every manufacturing plant will experience at some point and can become chronic if not solved. While understanding fatigue has advanced since its inception in the early 1800s, there are still some misunderstandings in manufacturing in solving these failures. A characteristic of fatigue failures is stress, which is typically below the yield strength of the material. This is what makes fatigue a silent killer.

Root Cause Analysis has the potential of CHANGING people, IF the leader of the investigation knows of this potential. Far from “just another problem-solving exercise,”the root cause analysis should SLOW PEOPLE DOWN to the extent that they can see the truth of the incident under inquiry, WHATEVER THE TRUTH MIGHT BE. This paper focuses on two parts of our human nature which are large obstacles to root cause discovery, i.e., our unwillingness to slow down, and our unwillingness to let go of certain basic assumptions about life. Warning: This paper is designed to challenge the way you think about Root Cause Analysis.

As a teacher and a practitioner of root cause analysis, I see not only the physical motions of going through such an effort, but also the psychology behind what makes or breaks it. When you consider the effort that goes into determining root causes and developing recommendations, why should it be such a hard sell to get something done?

When a bearing in a critical piece of equipment fails prematurely, a maintenance specialist knows the failure usually indicates there is more here than meets the eye. What the untutored eye sees is a failed bearing and little more. However, a premature bearing failure is symptomatic of other problems that, if left untreated, will cause the same kind of failure to occur again.

To understand why a part or equipment failed, how it failed must be first diagnosed. Different failure modes such as fatigue, brittle, and corrosion all have very different causes and very different solutions. If an investigation were to guess at the failure mode and guess wrongly, the planned remediation may not address the true cause of failure and additional failures may occur. This article considers three failed chain links and demonstrates the importance of identifying how something failed.