Fault Tree Analysis (FTA) provides a means to logically and graphically display the paths to failure for a system or component. One way to manage a complex system is to start with a reliability block diagram (RBD). Then create a fault tree for each block in the RBD.
Whether a single block or a top level fault for a system the basic process to create a fault tree follows a basic pattern.
1. Define the system. This includes the scope of the analysis including defining what is considered a failure. This becomes important when a system may have an element fail or a single function fails and the remainder of the system still operates.
2. Define top-level faults. Whether for a system or single block define the starting point for the analysis by detailing the failure of interest for the analysis.
3. Identify causes for top-level fault. What events could cause the top level fault to occur? Use the logic gate symbols to organize which causes can cause the failure alone (or), or require multiple events to occur before the failure occurs (and).
4. Identify next level of events. Each event leading to the top level failure may also have precipitating events.
5. Identify root causes. For each event above continue to identify precipitating events or causes to identify the root or basic cause of the sequence of events leading to failure.
6. Add probabilities to events. When possible add the actual or relative probability of occurrence of each event.
7. Analysis the fault tree. Look for the most likely events that lead to failure, for single events the initiate multiple paths to failure, or patterns related to stresses, use, or operating conditions. Identify means to resolve or mitigate paths to failure.
8. Document the FTA. Beyond the fault tree, graphics include salient notes from the discussion and action items.
FTA is a convent means to logically think through the many ways a failure may occur. It provides insights that may lead to product improvements or process controls.
Related:
Benefits of Fault Tree Analysis (article)
Intro to Fault Tree Analysis (article)
Fault Tolerance Basics (article)
Hi Fred. Thank you for the informative step-by-step revelations process of FTA. I am novice to this. I have seen FTA’s, which have the “OR”s & “AND”s. It would be great if you have an example of a complete FTA.
Hi Mulyadi, I’ll look into developing a couple full examples. In the meantime there are a few that are available online. This slideset from NASA, http://www.hq.nasa.gov/office/codeq/risk/docs/ftacourse.pdf, has a couple pretty good examples.
Cheers,
Fred
Are there any companies using Artificial Analysis t to perform Fault Tree Analyses?
Hi David, if you mean artificial intelligence, I’m not sure. If it’s artificial analysis I’ve no idea what that means other than the way my roommate did homework in college, at times. cheers, Fred
Hi, can FTA be used to find the values of reliability indices for reliability analysis?
Hi Gaki,
Technically yes it can, yet there are better tools to estimate reliability for an item or function. The FTA starts with a top unwanted outcome (like system failure or power supply failure) then lays out the various paths of events that may lead to the unwanted top event. Then working out the probability of each element in all the paths one can sort out the probability of the top event.
I tend to use a reliability block diagram to organize the reliability information and conduct calculations – at least for me it’s easier.
cheers,
Fred
helo sir how i can make the fault tree analysis diagram of event management system
Hi – not familiar with an event management system, yet the typical use of an FTA is to start with the top unwanted outcome – and work through the process to identify elements that could lead to the unwanted outcome.
cheers,
Fred
sir any help please
well, for the event management system, what would be an unwanted outcome, a failure of the system? That then would be the top block, then follow the remaining steps outlined in the article.