Hey everyone! If you’ve ever worked with FMEAs, you know they’re great for mapping out potential failures, but they don’t always tell the full story. That’s where Fault Tree Analysis (FTA) comes in—it helps fill in the gaps by modeling system logic and dependencies. We recently hosted a webinar diving into this exact topic, and I’ll be posting a link to the recording so you can check it out for yourself!
Why Combine FMEA with Fault Trees?
FMEAs help you catalog failures, but they assume a pretty straightforward cause-and-effect relationship. Real-world systems are more complicated than that. Fault trees let you introduce logic gates (AND, OR, voting gates) to capture how failures interact, making your reliability analysis much more accurate.
We recently held a webinar on the topic of using FMEA's and Fault Trees together, in the webinar, we walked through a practical example using an airbag system. We showed how you can start with an FMEA, build a failure net, and then transform it into a fault tree for deeper insights.
The Process: From FMEA to Fault Tree
- Start with the FMEA:
- Identify failure modes, causes, and effects in a structured tool like e1ns.
- Build a failure net to visualize how failures are connected.
- Move to the Fault Tree:
- Use Data Link Manager to transfer the failure net into FaultTree+.
- Convert those cause-and-effect relationships into fault tree logic.
- Refining the Model:
- Add logic to reflect real-world system behaviors, like redundancies.
- Assign failure rates from industry sources (MIL-217, SN29500, etc.).
- Use minimal cut set analysis to find the weakest points in your system.
- Run the Analysis & Make Improvements:
- Check how often system failures are likely to happen.
- Compare results against industry safety targets (ASIL, SIL, etc.).
- Implement design changes (like redundant sensors) to improve reliability.
Key Takeaways from the Webinar
- FMEAs Are a Starting Point: They help catalog potential failures but don’t handle system logic.
- Fault Trees Fill in the Gaps: They let you model dependencies and quantify failure probabilities.
- Data Integration is a Game-Changer: The Data Link Manager makes it easy to bridge FMEA and FTA.
- Redundancy Matters: The airbag example showed how adding a 2-out-of-3 sensor voting gate drastically improved system reliability.
Final Thoughts
At the end of the day, combining FMEA with Fault Tree Analysis gives you a much clearer picture of system reliability. With tools like e1ns and FaultTree+, you can make smarter design choices and build more robust systems.
And if you have any questions or want a demo of our tools, just reach out. Let’s keep the conversation going!
Author:
Jeremy Hynek, PeakAvenue