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Fault prediction


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Hello everyone,


I didn't do much research on the topic, but i guess in many industrial facilities where any fault may lead to dramatic consequences, engineers just use a fault detection unit to prevent any hazardous incident. But I've been wondering if there has been some works on fault prediction, like a technique able to foresee the incident given the actual state of the facility's equipment and the constraints they undergo. This would be very important for the safety of the equipment and the staff.


What are your view points on the subject ?


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Industrial safety standards use all sorts of techniques, such as:

  • Hazard analysis and risk assessment (H&R / HARA)
  • Failure mode and effects analysis (FMEA)
  • Fault tree analysis (FTA)
  • Dependent failure analysis (DFA)
  • Design review by failure modes (DRBFM)
Edited by Strange
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Maybe the original query wasn't about statistical prediction, but about monitoring the health of an equipment to detect wear.


In this case: yes, it's done - where possible. Ball and roller bearings are observed by measuring their vibrations. The remaining thickness of corroded steel vessels is observed by various means. Cracks in vessels can be detected acoustically.


There are many means - too many for one person to have them ready in his head. Each means is very specialized. Some means work on the operating unit, others (aircraft engines, nuclear power plants...) need to stop the equipment and even deassemble it. Some industries (nuclear, chemical, airlines...) do it always, some (sea transport...) do it sometimes, some don't because an accident is cheaper there or because detection is impossible.




But if the original post meant: "predict the reliability of a machine" - then no, sorry, this doesn't work.


Beacuse failure results from poor design rather than from constraints, and no method on Earth leads to good engineering. This results from good engineers, good prototyping and testing, but most definitely not from quality practices.


Even on strained parts where methods have been developed, no good reliability prediction exists. There are attempts for bearings, but for instance SKF just plainly writes "our experience tells that a bearing's lifetime is unlimited if used properly". The Hdbk-217 tries to predict electronic components' reliability but everyone who has made reliability experiments laughs at it. Woehler's curves try to predict fatigue failure due to alternate stress, but even the measurements on shafts are not repeatable. Possibly the least bad case is alloy creep at heat.


And then you have software, for which the only valid prediction is that it will indeed fail, and you'd better have none.

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