I have for many years worked with condition monitoring companies that do vibration analysis on machinery. Indeed the same is true of thermography and acoustic ultrasound monitoring too. Many of these organisations back up the service with independent lab analysis to cover all the bases for customers machinery.
If you were to ask any expert in the field which technology is best, a vibration analyst will tell you vibration, thermographers will say that thermography is best and acoustic engineers will say ultrasound. If you ask me, I would say they are all wrong as oil analysis is the best obviously. That is said with tongue in cheek obviously. Oil analysis is a good all rounder but it is not the holy grail to all fault detection and localisation in every scenario. So often a combination of technologies is the best approach, but it does raise the very valid question in which technology suits your needs to monitor machinery health.
Hence I will try to answer this question for the reader. Let me start off by saying I am an oil person I know something a bit about my subject area. However my knowledge of other condition monitoring technologies is nowhere near my oil analysis knowledge, so if you want to learn how to read a vibration analysis result there are many better trainers in this area than me. However what I can help with is where each works best and how they work in combination.
Which detects earlier?
This is usually fairly simple, in that even ordinary oil analysis in repeated studies detects bearing failures 10 to 15 times earlier than typical vibration, thermography or ultrasound monitoring. Why? Well changes in wear metals occur far earlier than physical changes in vibration for instance and oil analysis is also good at detecting causes such as dirt and water before they show as wear. However some situations such as a sudden gear tooth fracture from shock loading, the sudden nature of the failure shows very little in the oil sample as wear material. Whereas in something like a vibration analysis this would be very easy to spot.
Which identifies the wearing component best?
In terms of engines oil analysis is pretty much the only tool to use and no other tools are used commonly, as oil analysis can identify the different wearing engine components from the different wear metals. In hydraulics about 80% of all faults are contamination related, so again identifying the contaminant is more relevant than localising what it has worn. However in a greased bearing or gear system everything tends to be iron so although wear detection is earlier, identification of a specific component that is wearing (if not contamination related) may be more difficult. Hence why I often recommend following up other condition monitoring techniques. E.g. on a greased bearing once we find a fault to use vibration monitoring to localise the fault for instance or in systems overheating identify a localised hotspot with thermography. Equally in transformer analysis I suggest using acoustic monitoring to help localise electrical faults found with dissolved gas analysis of oils.
So what you will find is there is some synergy between different techniques and that is why a lot of these field based technologies supplement their services with an independent analysis like ours. We even allow them to badge the service with their logo to aid in bringing the package under one package to their customers.
Which is best?
So let’s discuss what are the strengths and weakness of each technology.
1. Vibration Analysis
What It Excels At:
Vibration analysis is superb at identifying imbalances, misalignments, and other mechanical issues in rotating machinery. By measuring the frequency and intensity of vibrations, specialists can detect anomalies that precede many types of mechanical failures.
Limitations:
However, vibration analysis can be less effective on non-rotating equipment such as engines or where the vibration signals are dampened or masked by other components.
2. Acoustic Analysis
What It Excels At:
Acoustic analysis involves the detection of ultrasonic frequencies that are typically beyond human hearing. This method is highly effective at locating leaks in pressure and vacuum systems, detecting electrical discharges, and even identifying poor lubrication states in bearings.
Limitations:
Its limitations include difficulty in noisy environments where background noise can interfere with the detection of relevant signals. Additionally, acoustic analysis provides little information about the condition of internal machine components beyond bearings and leaks.
3. Thermography
What It Excels At:
Thermography uses infrared cameras to detect heat patterns and anomalies in equipment. This technique excels at identifying overheating components, electrical faults like loose connections or overloaded circuits, and blockages in fluid systems.
Limitations:
Thermography can be less effective in environments with fluctuating ambient temperatures or where heat emissions are shielded by casings or other components. It also does not provide information on internal mechanical conditions unless they manifest as heat.
4. Oil Analysis
What It Excels At:
Oil analysis is crucial for assessing the internal condition of all lubricated systems, but is not possible on non fluid or grease lubricated systems. It can detect contaminants, wear particles, and chemical properties of the oil that indicate wear, contamination, or degradation of the oil itself.
Limitations:
The main limitation of oil analysis is that it is an indirect method; it can suggest that a problem exists but often cannot locate which component is failing for non engines. This often doesn’t matter if it’s a contamination related issue as removing the contaminant often resolves the wear cause. Additionally, it requires periodic sampling and laboratory analysis, which is not a real-time result, but as stated earlier can still detect faults earlier 10 to 15 times more than the other technologies.
Combining Techniques for Optimal Results
Where Combinations Work Best:
The combination of these techniques often provides a more holistic approach to machine health. For instance:
- Vibration and Oil Analysis: This combination is excellent for rotating machinery, where vibration analysis can detect mechanical anomalies and oil analysis can confirm internal wear or lubrication issues.
- Oil dissolved gas analysis, Thermography and Acoustic Analysis: Useful in electrical systems, where thermography detects hot spots due to electrical faults and acoustic analysis can pinpoint discharges or arcing.
Conclusion
Each monitoring technique has its specific application scope and combining them often leads to the most accurate diagnostics. By understanding the capabilities and limitations of each method, maintenance teams can tailor their monitoring strategies to the specific needs of their machinery and operational demands.
Are you keen to explore how these techniques can be integrated into your maintenance strategies? Click the ‘Contact Us’ button to find out more and discuss your specific needs with our experts.
Equally if you are a professional performing on site condition monitoring and would like to support your service with the very best industry leading oil analysis, then get in touch.