on Systems Thinking

I recently received an interesting LI inquiry that I felt others could learn from the answers that I was able to get. This is not my expertise so I sought out answers from some colleagues who were more familiar with fasteners.

Here is the original inquiry (translated from Portuguese so I hope Google Translator did a good job):

“I would like to know if you can help me clarify my doubts about:

1. The purpose of conducting a study of the coefficients of friction in screws, threads and nuts?
2. Is there an accurate standard for such testing?
3. What methods can be perfected in projects that target this type of trial and application?
4. Can surface treatments influence changes in results?
5. Who is responsible for such testing (the manufacturers and suppliers of raw materials, the assembler and/or its various final assembly applications)?

Lets start with a fresher on general Component Fatigue.

• Fatigue occurs when a material is subjected to repeated loading and unloading.
• When the loads are above a certain threshold, microscopic cracks will begin to form at a material’s surface.
• Cracks always begin in high stressed areas of a material.
• Eventually a crack will reach a critical size, and the structure will suddenly fracture.

Let’s start off with some honesty…the term ‘RCA’ (Root Cause Analysis) is quite vague, misleading and easily misinterpreted by those who are not immersed in its use. It is a useless and counter-productive term because there is no universally accepted, standard definition. Therefore, any process/tool someone is using to solve a problem is likely to be labelled as ‘RCA’. It could be troubleshooting, brainstorming and/or some other more structured problem solving approaches such as 5-Whys, fishbone diagrams, causal factor trees and/or logic trees. 

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Author’s Note: I want to reiterate that this Series about reading the basic fracture surfaces, is for novices who often come into contact with such failed components. This Series is about the basics (101), and is intended to give readers an appreciation for the value of such ‘broken’ parts to an effective investigation/RCA. While this information will be rudimentary to seasoned materials engineers/investigators, I know they will all appreciate heightening awareness to the need to retain such failed parts for formal analysis, versus throwing them away and just replacing the part. Throwing away failed parts is a recipe for a repeat failure. When one does not understand why the part failed in the first place, they can’t prevent it from failing again.

In this article we will focus on how to actually incorporate the evidence (failed parts) from a failure, into a disciplined Root Cause Analysis (RCA) process.

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To those following this Series, I will apologize for the front-end redundancy. I am doing so for those that are NOT following the Series and will read these articles independent of each other. If you are following the series (Thank You!) and proceed past the front-end stuff and to the shaft pics below:-)

Abstract. In our last series highlighting the 4 primary Failure Modes (FM) of component failures (erosion, corrosion, fatigue and overload), we discussed how to read fractured surfaces. In this follow up series, we will take a look at tips on how to collect, preserve and examine such failed components.

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I recently attended a conference where I listened to a presentation on Human Performance Improvement (HPI) by Dr. Todd Conklin and other speakers advocating Dr. Conklin’s ‘Learning Team’ approach. This was the first time I had heard Root Cause Analysis (RCA) referred to as ‘old school’ and obsolete. This got me to thinking, given I have been in the RCA business for decades, is what I do for a living…obsolete?

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In our last series highlighting the 4 primary Failure Modes (FM) of component failures (erosion, corrosion, fatigue and overload), we discussed how to read fractured surfaces. In this follow up series, we will take a look at tips on how to collect, preserve and examine such failed components.

[Read more…]

Author’s Note: I want to reiterate that this Series about reading the basic fracture surfaces, is for novices who often first come into contact with such failed components. This Series is about the basics (101), and is intended to give readers an appreciation for the value of such ‘broken’ parts to an effective investigation/RCA. While this information will be rudimentary to seasoned materials engineers, I know they will all appreciate heightening awareness to the need to retain such failed parts for analysis, versus throwing them away and just replacing the part. Throwing away failed parts is a recipe for a repeat failure, when one does not understand why the part failed in the first place.

[Read more…]

Author’s Note: I want to reiterate that this Series about reading the basic fracture surfaces, is for novices who often come into contact with such failed components. This Series is about the basics (101), and is intended to give readers an appreciation for the value of such ‘broken’ parts to an effective investigation/RCA. While this information will be rudimentary to seasoned materials engineers, I know they will all appreciate heightening awareness to the need to retain such failed parts for analysis, versus throwing them away and just replacing the part. Throwing away failed parts is a recipe for a repeat failure, when one does not understand why the part failed in the first place.

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This article is directed at those ‘first responders’ who arrive immediately at the failure scene. These are the people who have to ensure the area is safe, preserve the scene for investigators and contribute to a plan to expedite a quick, safe return to production norms.

Many do not understand how valuable failed parts are to the metallurgical/forensic investigators. Broken parts are to metallurgists’, like the murder weapon is to a forensic crime investigator.

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Can you identify and name this fracture pattern?

How can you tell it is that fracture pattern?

Where are the origin(s) of the failure on the fractured surface?

How can you tell where the origin(s) are?

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RCA Self-Assessment Tool. (linked version no longer available) The purpose of this tool is to allow individuals or groups to anonymously self-assess their current RCA system. How they wish to use the results is completely up to them!

All results are private and not retained anywhere. Therefore, if you wanted to keep your results, you would have to print them out and scan them back into your work station (or your past results are gone).

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This failure occurred on a turbine driven boiler feedwater pump (TDBFP) at a fossil fuel power plant. The pump in question is an outboard boiler feed pump. Plant is operating normally when unexpectedly pump shuts down and causes a forced outage.

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This is a failed shaft that came out of a pump in a paper mill. The pump was only in service for about a month before it failed unexpectedly.

From the top view above, identify the type of failure pattern that you see from the fractured surface(s). If you need more info to make your assessment, just ask.

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Where does ‘failure’ come from? Why do some things not go as we planned? When bad things happen, at that time, it can be chaotic and appear very complex. Often, in hindsight (when the urgency has faded), we find that good people made bad decisions at that time. Most of the time such failures were not complicated and we find that most likely, anyone else put in the same position, would have made the same decision. So why do things not always go as planned?

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