What is Fault Tree Analysis?

Fault tree analysis (FTA) is a tool that allows for visual and mathematical representation of the system to determine the possibility that it is experiencing system or machine failure. This is a top-down process that reverse-engineers possible failures via the root-cause analysis process. Below are some examples of fault tree analysis.

Fault Tree Analysis tool is a way to answer the question, “How likely are you that this machine will cease functioning?”

FTA illustrates how failures travel through a system. This generates a graphic model showing how component failures can cause system-wide failures. Reliability engineers use these models to design systems with the correct redundancies and prevent component breakdowns from causing system-wide failures. It can also create fault-tolerant systems.

FTA is simple, even though it sounds complex.

FTA models can be modeled with analytical graphs that look similar to trees. These are called fault trees. The fault tree diagram will help you to see how one or several failures can lead to catastrophic failure. This will help you choose the most effective preventive and corrective actions in the future.

Different types of analysis for fault trees

The Standard Fault Tree Analysis may not be the best option. FTA can be extended for specific industries or use cases. These extensions can visualize features that are not easily expressed by standard fault trees. These are just a few:

  • Dynamic FTA Dynamic Fail Trees: Dynamic fault tree (DFT) that extend fault trees, model complex system behavior and interact with them.
  • Repairable FTA-Repairable Fault Trees Enhance the FTA model to allow for complex, dependent repairs to system parts.
  • Extended: Considers multi-state components and random probabilities.
  • Fuzzy: This complicated mathematical concept is called fuzzy set theory. It takes into consideration unreliable variables that are difficult to predict (like wind or weather).
  • State-event FTA: The SETF can be used to analyze dynamic behavior that fault trees cannot model.

FTAs fall generally under one of two categories: qualitative, or quantitative.

Qualitative analysis should be done at all times. Quantitative analysis is only possible when you have a clear idea of the probability of certain events. Let’s take a closer look at each.

Qualitative FTA

Qualitative fault tree analyses is used to analyze fault tree structure and identify system vulnerabilities. There are many methods to conduct qualitative fault tree analyses.

  • Minimal cut (MCS), helps identify system vulnerabilities. Unreliable systems are those with a small number of components or elements that have high failure probabilities. These elements can be identified in MCS’s fault tree. Redundancies or reducing failure probability can increase reliability.
  • You can use the Minimal Path Sets (MPS), to assess the system’s strength. This method identifies the minimum number required to maintain the system’s functionality. Once you have identified the components, you can reduce their failure rate. This increases the reliability of your system.
  • Common causes error (CCF). Determine if multiple elements could cause failures. CCF is used to identify critical components. These components must be regularly inspected by your team and replaced if needed. Limble is a computer-aided maintenance planning system (CMMS) that can schedule and plan maintenance for these crucial components.

Quantitative FTA

For calculating the likelihood of failure, the quantitative FTA method is useful. This will help you understand your risk better and prioritize it.

Quantitative FTA can produce important or stochastic measures.

  • Stochastic measures can be used to predict the possibility of the system’s failure.
  • Importance Measures show the importance of a cut set or path to reliability.

Once you know the probabilities of your basic events, you can use the gates to calculate the probabilities of your intermediate events. OR gates and AND gates represent the most common gates. Here’s an example.

Why is Fault Tree Analysis worth it?

FTA can be complicated and requires a lot of math. It’s worth learning it and putting it to use in your business. It:

  • Assists in the analysis, understanding and improvement of your systems
  • Let’s take each one of these faults and address them in a systematic way.
  • A review of multiple systems and how they relate to each other
  • It is important that you focus on the root cause, not the solution.
  • Prioritize repairs based on failure rates and issues that could lead to catastrophic failures
  • This tool allows you to plan and design maintenance based on the probability of failure for each system.
  • Takes human error into account

FTA offers all of these benefits, so it is a good idea to include FTA in your analysis toolbox. FTA allows you to see the future and predict it.