Industrial systems very seldom fail only due to one obvious problem. There are a number of reasons a production line could stop, such as electrical failure, part failure, control failure, or a combination of many smaller problems. That’s where fault tree analysis is useful, before these connections lead to downtime. It provides engineers with a systematic approach to identify combinations of failures which can cause an undesirable event to happen and to work backwards from it. This can be a proactive way for industries to identify vulnerabilities, enhance equipment reliability and make well-informed maintenance decisions before equipment failure occurs.
So what is Fault Tree Analysis?
Fault Tree Analysis is a systematic (top-down) approach to the study of how various failures could contribute to one undesirable event. The analysis starts with a “top event” that has already occurred, e.g., equipment shut down, loss of production, fire, loss of power.
Engineers then reverse engineer – decomposing the event into possible contributing causes. The logical relationships (AND, OR gates) indicate whether the top event occurs when one or more failures occur.
This results in a “road map” of the visual field linking seemingly small faults together to form a major industrial issue.
How to do this, and why it is needed is another story?
One failed component does not have to instantly bring a facility to a halt. But, if it fails along with another weak point, the results can be far more severe.
Consider an important production machine that suddenly shuts down. The first thought that comes to mind is probably motor failure. Further investigation may have shown that the motor had been overheating due to poor cooling, and that the monitoring sensor had also failed to give an early warning.
One of the main advantages of fault tree analysis is that it has a wider perspective. It takes investigation beyond the symptom and looks at the sequence of events that led to the symptom.
Identifying weak links prior to failure
To ensure industrial reliability, vulnerabilities need to be identified when systems are operating. A fault tree can be used by engineers to analyze:
- Critical equipment and components
- Electric and control system failures are among the causes.
- Safety system vulnerabilities
- Human or manual errors
- Maintenance-related failures
- Common-cause failures
- Combinations of independent faults
Knowing that these are weak points, then organizations can prioritize what needs to be done to rectify the failures rather than fix all of them with the same urgency.
Analysis to Prevent Action
The true power of Fault Tree Analysis is in the use that is made of the diagram. The results can help determine the schedule for preventive maintenance, equipment upgrades, redundancy planning, inspection schedules, and safety enhancements.
If an analysis indicates that while one backup component fails, an entire safety function is rendered useless, then the component is not considered to be a backup. If one backup component failure will make an entire safety function inoperable, then it is not a backup component. The discovery of this can lead engineers to question the reliability of the component, add extra redundancy or change the inspection schedule.
Failure analysis is a useful and practical technique for preventing failure rather than merely reporting what has already occurred.
Supporting Smarter Maintenance Decisions
Maintenance strategies for each component will not be the same. Some failures will have little impact, others can stop production or pose significant safety hazard.
Fault tree analysis can identify the routes by which critical failures occur and guide the maintenance and engineering team to target resources where they can have the biggest impact. It can also be used in conjunction with other reliability methods, providing a more comprehensive picture of equipment performance.
Conclusion
Industrial reliability is not a mere matter of getting the machines repaired as fast as possible after breakdowns. It’s the concept of finding out what fails, and decreasing the chance for it to fail in the first place. A major drawback of this is the logical approach that is possible when applying Fault Tree Analysis, which can be used to trace back major problems to their contributing causes and reveal weak links that may go unrecognized. If used properly, it can lead to a change in industry culture from reactive troubleshooting to proactive reliability, safer operations, and reduced unexpected downtime.
Also Read: A Safer Facility Starts With Questions: What Does Your Electrical Risk Assessment Ask?