Tuesday, 6 November 2012


Ah! Failed equipment! Why? Wear! Wear & tear! We have all heard that frequent enough. When I first started my career as an engineer, I accepted that as a form of failure mode so to speak. Things wear, components wear after use, and it is acceptable. Am I right?

No! Wear is NOT a failure mechanism. It is far from being a failure mechanism. A failure mechanism can be dealt with through some form of maintenance (not replacement). It is an overly vague term to be used as a failure mechanism. It is exactly like seeing a failure notification in CMMS that says equipment is f*cked! It does not add any value at all. As a maintenance personnel, you cannot tell anything out of that notification. As a reliability analyst, there is no useful data for you to analyse.

I came across a failure mechanism list developed by a consultant for their clients. In there, was Wear. Caused pointed towards cavitation, rubbing, fretting, abrasion and erosion. Lets dwell deeper on what is wrong about that.

Cavitation itself is a failure mechanism, and it is caused by insufficient head pressure. A pump specification will give you head required to prevent cavitation becoming an issue up to its useful life probably around the 15-20 years mark depending on manufacturer. To design cavitation out totally, make sure there's a good 30-50% more head that it needs be on top of the recommended head on specification sheet. Rubbing and fretting are again failure mechanism, they are likely caused by improper design or installation. Abrasion and erosion are again failure mechanism that are likely caused by improper material use or highly abrasive material handling. The failure mechanisms all have individual cause and different way to manage. Is it clearer now that wear is not suitable to be used as a failure mechanism? It is incapable of pin pointing a method to "fix" wear.

Wear is a consequence of a failure mechanism due to a cause. Wear by itself is not a failure mode. It can be use as a simplified technical term for the business minded management team to understand, but it should never exist in the technical team itself. If you are a manager to a technical team, use your words concisely as a technical person. It drives the maintenance culture which affects the reliability bottom line. Excellent maintenance culture is 50% of a high reliability plant, and a reliable plant, is a safe plant.

Till then, stay reliable, stay safe.

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