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| Inside This Issue |
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May 2009 |
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| The Importance of Qualitative Static dBµV Testing (SDT) in Acoustic Lubrication | ||||
Allan Rienstra, Editor |
Friction between a bearing's rolling elements and races produce
ultrasonic sound which has an amplitude level directly proportional to
the friction. This relationship is the fundamental principle for
acoustic lubrication. As the lubricant film becomes less effective at
separating the metallic surfaces friction increases in concert with the
measurable ultrasonic amplitude. Restoring the lubrication film will
decrease the friction and consequently the amplitude.
Lube technicians use ultrasonic detectors equipped with special contact probes to evaluate qualitatively and quantitatively the state of lubrication in rolling element bearings. Qualitative evaluation depends on the ears of the inspector to judge what is heard through the headphones of the ultrasound detector. Using his own criteria, experience, and best judgment the lube tech listens to the ultrasonic signal of the bearing and decides if it requires greasing, and if so, how much grease to add. While there is an art to this method, there may not be very much science. The reality is that all bearings produce some level of ultrasound and in certain situations it is hard to evaluate if the sound is normal or abnormal, simply based on what was heard. Furthermore it is impossible to baseline, compare, or consult because it is absolutely possible for two people to hear the same signal in completely different ways. There are acoustic devices available on the market that are based solely on qualitative interpretation. Greasing decisions should not be based on hearing alone, but rather on a combination of qualitative and quantitative data. Quantitative evaluation is the science that makes ultrasound effective for acoustic lubrication. By the very definition of the word, "quantitative" suggests some level of measurement, benchmarking, and trending will help decide conclusively the lubrication needs of the bearing. Quantitative can refer to static measurements where digital decibel metering is used for trending. Or it can go a step further and refer to Ultranalysis™, the science of analysing dynamic ultrasonic signals in the time and spectrum domains. Static dBµV measurements are the standard best practice for lube techs and Dynamic Ultranalysis is the advanced best practice. Where static measurements are well established and understood dynamic measurement methods are in their infancy and a lot of the rules are still being written. But that is a discussion for a future newsletter. For now lets focus on static digital dBµV testing (SDT). With SDT methods lube techs can:
Take advantage of both Qualitative & Quantitative techniques: SDT170S+ Lube Tech Kit |
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| Ultrasound Tip - Pointers for Lube Techs | ||||
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Condition based lubrication
programs rely on ultrasound data collection to alarm when re-greasing is
required. Lube techs grease bearings with an ultrasonic grease gun
interface to ensure the right amount of grease is added. Some confusion
about how much grease is enough still remains a question mark. Our
advice on the subject >> click here
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| Analysing a Dynamic Signal During Lubrication | ||||
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Using static decibel metering to determine lubrication
intervals on motor bearings depends on an accurate ultrasound meter. It
also presumes that the lube tech understands what the measurements and
results mean.
This waveform is a signal captured on the inboard bearing of a pump/motor at Canadian Light Source in Saskatchewan, Canada during program implementation training. Listening to the bearing as the grease reduces friction is impressive. But what did we really hear? |
 Before the bearing was greased it read 43dBµV. After greasing the signal dropped to 13dBµV, a drop of 30dB. That is equivalent to a factor of 31.6. The lube tech is satisfied to know that the friction levels are 31.6 times lower thanks to his swift strokes with the grease gun. |
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| Upcoming Training Events - New Sessions Just Added!! | ||||
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Level 1
and Level 2 Airborne Ultrasound Certification is coming to a city near
you. We've added several new dates and locations so if you haven't
checked our training calendar lately, check it out by
clicking on this link.
We've certified over 300 inspectors worldwide this year and several thousand over the pas three. To have a long lasting effective ultrasound program you need at least one certified ultrasound inspector. No Budget to travel? No Problem! We can bring our training to you. Click here to request more information about our training programs, both public and onsite |
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| Here More Ultrasound in Latin America - www.ultrasonido.ca | ||||
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It is with great excitement and pleasure that I announce the
launch of www.ultrasonido.ca our
full Spanish Language website designed to service are important and
growing customer base in Latin America. For our Spanish speaking friends who enjoy The Ultrawave Technology Report, and would like to read Spanish updates as well, I invite you to click on the link below and Subscribe to "Reporte Técnico SDT" Reporte Técnico SDT is a frequently published newsletter under the direction of our Latín American Sales Manager, Gustavo Velásquez We hope you will enjoy both of our corporate newsletters. |
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| We take your privacy seriously | ||||
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The Ultrawave Technology Report is published regularly by SDT North America and is intended to provide information to anyone with an interest in this technology about current and future events. If you have questions about this email or the format in which it's received please contact Allan Rienstra. If you do not wish to receive these updates you can request removal from the list at anytime by sending an email to allan@sdtnorthamerica.com.
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