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GVS Reliability Products in conjunction with SDT Ultrasound Solutions is proud to present the below case study, Ultrasound Inspection On Rotating Assets, submitted by Mike Halls.
Mike is Technical Officer of Condition Monitoring at Rio Tinto’s Yarwun alumina refinery where he has held this position for over seven years. Mike has over 20 years working in the condition monitoring field, utilising popular technologies such as VA, Thermography and Oil Analysis. And now Ultrasound for the last 2 years!
Mike’s years of experience have given him a unique perspective on using ‘alternative’ condition monitoring tools such as the SDT 270 PRO, the world’s flagship ultrasound inspection device. With the SDT 270 delivering reliable, repeatable and calibrated ultrasound data and, with the power of signal analysis using SDT’s UAS software, Mike has been able to clearly demonstrate that ultrasound inspection should be the technology of choice for certain applications.
When using Ultrasound inspection technology in a harmonious relationship with other condition monitoring inspection devices, plant coverage increases, as does the overall reliability and availability of monitored assets. This then translates into greater production capacity and therefore overall profitability of an enterprise/company.
A portion of this case history was first published in The Industrial Eye: The official journal of the Australian Institute for Non-Destructive Testing – Condition Monitoring Issue – March/April 2017.
It has since been edited and rectified to give further information regarding the case.
Read on for Mike’s ultrasound inspection success story…
Case History: Mike Halls – Rio Tinto Yarwun – 16-10-2017
Bearing Life Extension using SDT 270 Contact Ultrasound measurement

Equipment Details
Equipment: P2620Vacuum Pump
Bearings: Tapered Roller Bearings
Pump Speed: 222 RPM
Motor: 630Kw – 6 Poles
Number of Vacuum Pumps on Site: 21
Costs associated with bearing failure
Overhaul cost due to a bearing failure: $120K
Total Replacement cost: $300K
Costs due to lost production or downtime: Currently there is some redundancy (as long as there are not too many other problems…). This may change in the near as further production demands are made on the plant.
History
Previous vacuum pump equipment failure modes and RCA’s have revealed that there has been an increase in bearing internal clearances & cage wear resulting in premature bearing failure. Due to the nature of these machines, vibration spectral analysis only revealed bearing defects in the later stages of the failure mode. Vibration analysis identified advanced propagation of fatigue due to surface cracks and spalling of the bearing raceway surfaces which were already resulting in unsatisfactory equipment performance.
Contributing factors to consider when using a vibration analysis approach are
a) a relatively low operating speed and
b) fluctuating ‘flow related’ vibration
Both of the above plant characteristics have the tendency to mask the early stage, low level amplitude bearing defect fault frequencies which, had they been detectable, would have indicated sub-surface bearing raceway defects and/or lubrication related anomalies. See the vibration analysis plots below as reference.
Vibration Analysis Plots
Below is the vibration Acceleration & PkVue spectral data taken the day after the acoustic vibration route was collected and, prior to any maintenance or lubricant/greasing intervention. Vibration analysis of the spectral plots indicates that the dominant frequencies relate to the vacuum pump pressure pulse fundamental & related harmonics. Neither of the plots indicates incipient bearing anomalies or lubrication related issues.


Challenge
With traditional condition monitoring technologies being limited in their capacity for detection of the early stages of the bearing failure modes, trending of the degradation process was not possible. Without being able to detect and trend the early stages of the failure modes, this left the plant exposed when needing to determine a projected planned maintenance window. So, once the later stage defects were finally identified, the asset was already at a critical crossroad in
a) needing immediate attention or
b) risk plant failure with consequent potential safety hazards or production loses.
Solution: Acoustic Vibration Monitoring Trial
Acoustic Vibration Monitoring or contact Ultrasound, are terms used when an Ultrasound inspection instrument (in this case the SDT 270 PRO), utilises a sensor to contact (touch) a surface to detect attenuated ultrasound signals. Using a sophisticated instrument such as the SDT 270 PRO, the ultrasound signals can then be acquired as either dynamic (for analysis and playback) or static measurements (for trending) and logged in SDT’s proprietary database, Ultra Analysis Suite (UAS).
Just over twelve months ago, an Acoustic Vibration Monitoring strategy was implemented on a trial basis to complement the vibration analysis program on the vacuum pump routes. This was done mainly to assist with lubrication related concerns and incipient bearing defects that vibration analysis was unable to confidently detect. After employing the ultrasound inspection strategy (with the 270), and the data analysed in UAS, a number of lubrication concerns with the vacuum pump bearings were rapidly identified. See figure 1 and 2 below.
Figure 1. Static trend

Figure 2. Dynamic Signal

Listen to .WAV sound file at this Dropbox link.
Initial Results and Findings
The above Acoustic Vibration Analysis examples indicate a significant upward trend due to elevated ultrasound generated by the bearings. The ultrasound signal and trend indicate metal to metal contact that is identified by an outer race bearing defect. The causes for this are either inadequate lubrication or incipient bearing defect.
As already mentioned above, at these locations vibration analysis showed only high frequency data with a raised noise floor. This could be attributed to the product ‘flow’ and hence masked the true vibration signal. On the contrary (and unlike vibration), the Ultrasound signal is not affected by the ‘flow’ caused by the pump and hence did not mask/conceal the bearing condition data. Due to the clarity of this anomaly, we can call this a ‘text book case’ because in this example, increased readings in ultrasound data related directly to an inadequate bearing lubrication condition.
Due to the findings via the use of the SDT 270 Ultrasound inspection device, the recommended corrective action was; ‘grease the non-drive end bearing and re-evaluate the ultrasound values’.
Upon the recommendations being carried out in a timely manner, further readings were taken with results shown in Figure 3 and 4 below:
Figure 3. Static trend after recommended intervention

Figure 4. Dynamic signal after recommended intervention

Note: the vertical y axis between fig 2 and 4 is different by approx. a factor of 4
Listen to .WAV sound file at this Dropbox link.
Secondary Results and Findings
The data collected with the SDT 270 post lubrication intervention shown in figure 3 &4 showed drastically reduced static and dynamic ultrasound signals. Hence, the follow up survey indicated that the values had significantly decreased to within the acceptable ultrasound range. Further inspections were then planned to monitor the health of the asset. Through the unique attributes only available through ultrasound inspection with the SDT 270, the plant was protected.
Conclusion
Cost analysis:
Thanks to Ultrasound inspection and the access to complimentary software, a conservative estimate is that the company avoided a $120K+ cost to overhaul the pump due to a bearing failure. A catastrophic failure ($300K +) and potential compromise to personnel safety and plant production, would have seen the cost to the company far in excess of this $120K estimate.
Technology Analysis:
Ultrasound inspection has unique qualities which were instrumental in allowing condition monitoring to gain a true understanding of the health of the asset. For this application, other condition monitoring technologies were only useful once the asset was in the late stage of this particular failure mode exposing the company to high risks.
Furthermore, with the SDT 270’s ability to collect both dynamic and static data for trending and analysis, and the ability to record and analyse this data in the UAS software, the defect was easily identified and corrective actions taken.
Site Analysis and further actions:
Continued use of Ultrasound inspection technology to identify bearing condition will be employed so as to extend the reliability, availability and life expectancy of these important assets.
When using Ultrasound inspection technology in a harmonious relationship with other condition monitoring inspection devices, plant coverage increases as does the overall reliability and availability of monitored assets.
Thank you for reading.
I hope this study proved to be of use to you confirming best practice in technology integration results in determining a higher accuracy in detecting equipment failure modes.
For PDF download please view here Ultrasound-inspection-for-Rotating-assets-case-study-by-Mike-Halls-1.pdf

Guess what? Lube programs are ‘guess work’
Lubrication is the life blood of a healthy operating rotating machine. This fact was discovered thousands of years agoand employed by the ancient Egyptians in pursuit of greater reliability for their own rotating machinery. E.g. Animal fats applied to wheels of a horse drawn chariot reduced heat and wear on parts!

While lubricants and machinery have evolved from animal fats and cart wheels, what has not changed in all the millennia since then is this: the lack of precise knowledge of quantity and frequency of lubricant application for greatest effectiveness.
Over time through trial and error, we can assume the lube techs and maintenance personnel of ancient Egypt determined the correct time to apply grease/lubricant.
‘That wheel shaft has not been greased for 2 weeks and we travelled through a sand storm yesterday. It’s time to get the animal fat out! But how much should I apply?’
Let’s face it, for a cart wheel, a ‘best guess’ lubrication strategy should probably work fine.
But today in the 21st century, with far more complex rotating machinery, maintenance and lubrication professionals across industry still face the same two critical questions:
‘How much lubricant and when?’
As civilizations have come and gone, greasing programs have still not evolved from the ‘best guess’ approach.
Did I Guess right?
As with our ancient Egyptian forebears, to answer the: ‘How much?’ and ‘When?’ questions, trial and error has led to the conclusions we have made about greasing. From trial and error (testing and research), mathematical formulae have been developed based on; bearing capacity, operational load, rotational speed and operating environment. However, experts agree that this formula is still only the ‘best guess’ regarding grease quantity and frequency of application.
And from this guess work, most industry lubrication programs are based on the calendar.
While calendar based lubrication programs assume that ‘someone’ ‘somewhere’ applied the mathematical formulae to determine the grease quantity and interval, what math can never account for is constant variations in:
- Load
- Speed
- Operating hours
- Temperature
- Environment (dust, water, sand etc…)
These variables are critical in the determination of both grease quantity and interval between interventions.
So, we can confidently state: Even the most well thought out lubrication programs running on a calendar basis are ‘best guess’ and not ‘best practice’.
Given that poor lubrication practice (especially over greasing and under greasing), has a significant negative effect on the life cycle of bearings, the question needs to be asked:
Are you happy to leave the healthy operation of your critical assets to guesswork?
Did you answer NO?
Good because now GVS Reliability Products and SDT Ultrasound Solutions can help.
‘Know’ when to grease, not ‘Guess’ when to grease.
Do you want to ‘know’ when to grease or when not to grease? Do you want to ‘know’ the impact lubricants are having on your precious assets? If yes, then you will need to lubricate with the assistance of Ultrasound technology.
The key to understanding how ultrasound assists with lubrication is this: Friction causes Ultrasound.
- Perfect Lubrication (‘sweet spot’) = Lowerfriction = Less Ultrasound = Happy bearing
- Imperfect Lubrication (under or over greased) = Higher Friction = Higher Ultrasound = Unhappy bearing… ☹
So, given the above information, the premise for the successful lubrication interventions should be this:
Lubricate bearings based on condition/evidence, not on the calendar.
With an SDT ultrasound assisted lubrication strategy, lubrication programs can evolve from ‘best guess’ to ‘best practice’.
With SDT hardware in the hands of a lubrication technician, a source of reliable information (knowledge) as to the friction condition of ANY bearing becomes available. With the knowledge an SDT instrument provides, calendar based programs evolve to become condition based programs.
With the help of Ultrasound, maintenance has the power to change lubrication culture from:
“Hey, it’s 3 months since the last lubrication intervention, therefore my best guess is, it must be time to put 20g of grease into the bearing.”
to
“Hey, it’s 3 months since the last lubrication intervention, therefore it must be time to use my SDT Ultrasound technology to help me determine how much grease to put in the bearing.”
‘I Guess all Ultrasound Lubrication instruments are created equal…?’
‘Best practice’ lubrication is only possible with high quality ultrasound inspection instrumentation.
SDT devices such as the LUBEChecker, LUBExpert or 270 provide dB µV data numerically on-screen. This data is reliable and calibrated based on a reference point (1µV = 0dB).
SDT instruments empower operators to confidently say, “when I attached the Ultrasound contact sensor, the screen read ‘X’dB. When I finished greasing the screen now reads ‘Y’dB.”
This is quantifiable data and can be included in reports as evidence given for reasonable action.
The point of the above is this:
- Numerical data is criticalwhen asking lubrication technicians to grease bearings using technology.
Without credible data, what exactly would we be asking the lubrication techs to do with technology? They can listen but how do they report? ‘Grease the bearing until it gets quieter’. This methodology doesn’t work as ‘louder’ or ‘quieter’ is qualitative and is completely open to interpretation. You might as well just go back to the original guess work!
Prove it
As already mentioned, with an SDT Ultrasound solution, current lubrication strategies can transform into ‘best practice’. By applying the use of the technology, an SDT customer claims the reduction of grease consumption by up to 95%! At the same time, by all measures at their disposal, reliability and plant availability is at an all-time high.
Evolve from ‘Guessing’ to KNOWING!
With the constant development of technology, the way industry lubricates bearings is evolving. Given that evolution simply means ‘change’, then it is time to change.
When it comes to lubrication practices we can now change from:
- guessing
to - knowing
We can change from:
- ‘apply 20grams because it’s Tuesday’,
to - ‘it’s Tuesday so I’ll check my Ultrasound data to see if I need to apply 20 grams’.
As with a whole bunch Isralites a few thousand years ago, its time to leave ancient Egyptian practices behind and evolve our practice to survive in a rapidly changing world.
Things evolve. Things change. We are no longer greasing Egyptian chariot wheels. Get on board or risk being the victim of natural selection as the rest of the world changes around you.
Best Practice.
Give your team confidence. Give them the opportunity to perform best practice maintenance. Give them a reliable Ultrasound instrument from SDT!
If you would like to learn more about the technology and real success stories, call GVS Reliability Products today.

GVS Reliability Products was privileged and excited to exhibit and co-sponsor IMVAC, the all new conference for Vibration Analysts & Condition Monitoring Professionals.
The event ran at the Gold Coast from September 5th through 7th. IMVAC (International Machine Vibration Analysis Conference) was designed specifically for vibration and condition monitoring professionals. This is a perfect fit for GVS as we strive to inform and arm the reliability professionals with asset health inspection hardware in our corner of the globe. From the amazing IRIS M, Motion Amplification technology, the ground breaking LUBExpert and our industrial vibration sensor range from Hansford Sensors, GVS added great value to the IMVAC community.
GVS supported the hosting of workshops, learning sessions and case studies to the latest technologies featured in the expo. IMVAC provided practical learning in the important aspects of industrial vibration analysis and the complementary condition monitoring technologies (Thermography, Wear Particle, Oil Analysis, Motor Testing, Ultrasound, Lubrication, Shaft Alignment and Field Testing).
IMVAC helped attendees form new relationships with fellow reliability improvement practitioners, and provided actionable new skills and knowledge that can be taken back to the plant to help attendees deliver even greater value.
One final word, our principal supplier Ultrasound hardware of SDT engaged the esteemed Tom Murphy to join the team at IMVAC to present and discuss the advantages of a sophisticated Ut inspection device and program. From all reports, Toms presentations were a success and many took take the time to talk to Tom while attending the event.
Top Reasons to Attend IMVAC
- Focused Event
IMVAC is dedicated to Vibration Analysis, Maintenance and Reliability, and Condition Monitoring Technologies - Variety of Content
Each IMVAC event has 3 keynote presentations and over 50+ top-rated educational presentations from leading industry experts - Expand Your Network
Network with other learning professionals from leading companies around the world including Shell, Dupont, GE, Siemens, Bridgestone, Weyerhaeuser, GM, Johnson Controls, and MillerCoors - Learn from Your Peers
Improve diagnostic knowledge and skills while building relationships with peers who face the same challenges - New Technology
IMVAC has an Exhibit Hall featuring more than 30 exhibitors providing the latest products and solutions - Add to Your Library
The IMVAC Bookstore gives convenient access to the latest Condition Monitoring books (featured at IMVAC Australia and IMVAC USA)
GVS were indeed excited to be involved in the 1st IMVAC conference to be held in Australia.
We are looking forward to an exciting IMVAC 2018!