When to use Fuzzy Fault Tree Analysis

When to use Fuzzy Fault Tree Analysis

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In the interest of Root Cause Analysis, sometimes is it feels like there can never be enough to tools. It’s also easy to develop some favorites out of that toolbox. Even with those tools we prefer, there are limitations. Lean tools have logical teammates and partners that complement them and improve results. In this article, we’ll take a deeper look at the Fuzzy Fault Tree Analysis (FFTA) tool, when to use it, and which other tools complement it. Keep an eye out for how you could apply it in your own organization.

What is Fault Tree Analysis (FTA)?

Fault Tree Analysis is a root cause analysis (RCA) method that uses Boolean logic to analyze the potential of factors in a system to cause the “top event,” or error. The idea is to first decide which factors, such as parts and people, could produce an error. These form the backbone of the analysis. Then, the logic comes in. “And,” “or,” and other logic symbols are used to create scenarios where factors are evaluated based on their ability to cause an error on their own or with another factor. The end result of the analysis is a table that shows where the most critical factors and combination of factors are so that the risk of errors caused by them can be reduced.

What makes Fault Tree Analysis “fuzzy?”

In Fuzzy Fault Tree Analysis the uncertainty of some factors, tolerance for linguistic differences, and human failures are taken into account to allow for the calculation of the system reliability and determination of the systems failure logic. This is a key difference between FFTA and FTA, which is less capable of including such factors in the analysis.

Why would someone use Fuzzy Fault Tree Analysis?

The value in the FFTA’s inclusion in less black and white aspects is in its ability to take more of the system into account. Rather than limiting us to the factors that can be easily quantified and evaluated for key probability calculations, the FFTA allows us to subjectively explain and evaluate factors that don’t fit the conventional description. This results in a higher level of precision in the end result and a better understanding of the system reliability.

Examples of when to use Fuzzy Fault Tree Analysis

The FFTA is especially valuable in systems and situations that have more of those less objective, more subjective factors. It is also preferred when the potential costs of failure are extremely high, such as in healthcare and mining. Here are some examples to consider.

  • Selecting an Enterprise Resource Planning (ERP) solution provider:

    Due to the complexity of choosing and implementing a new ERP, the FFTA is a great match. An ERP has to work for the whole organization. That means, it needs to be able to accommodate every function, regardless of how objective or subjective it is. It also requires a multifaceted implementation process that can take months to complete. Any point in this project could be a deal-breaker and the consequences of choosing the wrong ERP are enormous in terms of time and money both at implementation and down the road. Using FFTA up front can improve the likelihood of choosing the best ERP and implementing appropriately in the organization.

  • Improving healthcare systems:

    There are plenty of metrics and data in a healthcare system, but some of the most important parts are all up to the performance of individual doctors, nurses, specialists, cleaning staff, and many more. Rather than trying to squeeze all of those factors into neat boxes and excluding the aspects that don’t quite fit into a conventional FTA, the FFTA leaves room for all of it.

  • Evaluating frequent occurrence of rare, high impact events:

    When something that shouldn’t happen very often, like an explosion in a foundry, starts happening a lot, the level of uncertainty goes up dramatically. Add to that the high cost of when it does happen and it’s even easier to understand why the conventional FTA may not be the best course of action. The FFTA takes more factors into account and can explain what’s causing the unusual occurrences.

Logical Lean tool partners for FFTA

5 Whys: It’s the all too familiar game of “why.” Start with the problem and ask why it happened, then why that why happened, etc. until you have the root cause. This pairs well with the FFTA, because it provides a structure to the process of evaluating the factors and how they impact the system.

Failure Mode and Effects Analysis (FMEA): Next time, add FFTA to your FMEA. They share the focus on failure and complement each other because FFTA gives a way to quantify those subjective factors that may be contributing to the failure. Through the FFTA process, more detail will add context to the FMEA.

Which other tools do you use with Fuzzy Fault Tree Analysis? Do you have a past project you think could have been more effective by utilizing FFTA? If this is a new topic in your organization, share it with colleagues and brainstorm times when it would be particularly helpful. If it’s not new, ask around and learn about the best practices that already exist or develop new ones to improve future outcomes.

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