3S9: (90 min.) Case Study: Vibration in the real world – examples from the field

John van Bynen , Director, Commotion Systems Pty Ltd


Big call! Yankee Dryer bearing
Vibration analysis is not always clear cut. False positives and negatives can happen. If you are in-house you might get away with quite a few of these, but as a contractor clients might not be so forgiving – particularly on large, expensive machines with enormous down time / cost implications. A Yankee Dryer bearing is one of these. When this fault was first detected, careful discussion was held with site to ensure they were not too alarmed, but concerned enough to put an engineering team together to plan the replacement. The spare bearings were checked by the manufacturer, how do you suspend a 40-ton monster? Organising the bearing replacement team and other matters. This luckily also allows time for further monitoring which revealed further bearing deterioration, as initially expected. How can you be certain? How do you judge severity? How can you be confident the bearing will last? Although bearing faults can be obvious, the management of replacement is often of paramount importance. This presentation will shine a light on how this was successfully done.

Things are not always as they seem. The mysterious bearing fault
An incumbent service provider had ordered a bearing replacement. Unfortunately, no damage was found and the frequencies of concern remained in the new bearing. A team of analysts looked deeper. Lots of theories, no conclusive answers. Commotion was contacted to investigate. Initial thoughts…What could it be if so many analysts have not worked it out? Never shy away from a challenge. There is always something to learn.
Looking at the site vibration database, clues were already emerging. What could it be? After collecting data, the origin of the fault was clear. This part of the presentation will teach us never to focus on one item too quickly and also a very interesting example of how bearing fault frequencies can be different to the expected.

Once in a lifetime. Yankee bearing
You can work an entire career and hope to have seen most of the faults we have all earned about during training courses. And then this one comes along. Initially, the investigation was not quite on the right track, due to a long history of having a different problem with this press roll. It quickly exceeded normal routine survey measurements and became an example of how the synchronous averaging technique helps isolate the symptoms successfully. Although at the time of writing, the after-repair measurements could not yet be taken, it is hoped that these will be available at the IMVAC conference. This presentation will teach us not to “jump the gun” and take things a step at a time, increasing the complexity of measurements and use of specialised equipment accordingly.

Fault frequencies for 80,000 bearings. How do we get our head around these?
Whilst employed at SKF in the mid 2000’s managing the Victorian team of vibration analysts, John learned about how ISO bearing designations are determined. Adding to this the knowledge of bearing fault frequencies gained over many years, he perceived a very simple relationship between the dimension series chart and all the bearing fault frequencies that vibration analysts deal with almost daily. An understanding of this helps to develop a sixth sense of bearing fault frequencies which when adopted, will certainly help you in identifying fault frequencies – even when no bearing details are available for the machine you may be assessing. It does rely on you thinking in orders though! May the arguments begin!


John has over 25 years’ experience in vibration consulting and specialises in accurate diagnoses of variable speed, complex and critical machines as well as “walk in the park” fixed speed plant. Much of his experience is in the pulp and paper industry, where there are always plenty of challenges.
Having worked for prominent companies in the vibration industry John established his own consultancy in 2008. The aim was to bring back care and attention to the work, which is so often lacking as larger condition monitoring service providers tend to focus on profit.
All too often, the fruits of our vibration condition monitoring efforts are discarded and along with them the evidence of correct diagnosis and justification for the condition monitoring service. The components and damage found usually speak for themselves. They offer a unique opportunity to instill confidence in the accuracy of the analyst and provide insight into the possible causes. We will look at several examples that use actual vibration data leading to correction and findings afterwards, as well as a unique concept for understanding bearing fault frequencies. There are several valuable lessons to be learnt.