CBM Conference by Mobius Institute - Bearings in 25 Animations or Less

hello and welcome to this presentation called bearings in 25 animations or less we'll be talking about rolling element bearings and fluid film bearings my name is Jason Tranter the founder and CEO of Mobius Institute okay so let's first talk about detecting rolling element bearing faults fortunately rolling element bearings give us a lot of warning of problems that they are experiencing there's a lot of different ways we can cause the bearings to fail there are a lot of different signs they can give us that there is a problem it just depends whether it's EDM like current flowing through the bearing or there's a crack or there's a lubrication problem or there's a spool or one of a number of different types of faults that can develop but the fact is that as the balls roll along or as the rollers roll through the bearing we first detect high frequency vibration and we can see both from the tone waveform derived from that high frequency vibration or from a spectrum - right from the high frequency vibration we can get a very early warning as the false gets worse we can see changes in acceleration spectra and time waveforms and then velocity spectra and time waveforms so we get a lot of warning and we can see how that fault develops so let's just have a look at the patterns themselves so what this little simulator is showing us is that as the balls roll along so there's our balls going along let's just assume for a moment that we have a fault right here on the bearing on the outer race so basically any time that that crack or spool or whatever it is when that is between the rolling elements there is no unique vibration in fact if the bearing was in perfect condition and the rollers were just rolling along we don't expect to detect any unique vibration based on the bearings themselves we'll get the One X vibration that's just the normal running speed vibration which is the big sine wave if we can see but no other types of vibration should be seen from the bearing but if we have a fault for example on the outer race then every time one of these rolling elements strikes that point there we get a little spike of vibration now even though in my simulator there I show that spike you know fairly large on the time wave form in reality in the very earliest stages of damage to the bearing we can't see that on the time way from it's just too small it's very low amplitude but fortunately it actually also generates very high frequency vibration as well imagine is kind of like ringing a dinner bell does bringing a tuning fork or something we've got a periodic ping ping hopefully when you heard my voices when the rolling element was striking the red ball red red mark there but it's kind of like ringing the tuning fork so we can pick that up as a periodic source of vibration we can detect that with certain techniques I'll just explain a bit more in a moment but anyway that's a periodic vibration now if the fault was instead on the inner race as it was in the animation just a moment ago as that damaged area rolls along with the shaft we get a penguin and strikes that bearing ping when it strikes that bearing and so on and therefore now what we are seeing is more frequent pings of vibration effect if we go back to this animation you can see it there that white wave you see rushing out is the ping that I'm talking about it's a stress wave which ripples out or also called a shock pulse that ripples out and we want to detect that but as the fault develops we will also detect it as normal periodic vibration in a spectrum or a time may form so that's one of a sort of fault and then we can see if it was on the rolling element itself then potentially two times per revolution of the rolling element the damage area will impact the inner race and add a race impact the inner race then add a race and we will see that in the time wave form as well now if it's a ball and it's rolling along it may be that it doesn't impact the Raceway every time or you know twice for revolution if it's a rolling element a roller and then it's more likely that we'll see that vibration but the key is that as the fault develops it starts up being very small and the vibration grows and grows and grows and if we use special techniques that isolate just the impacts themselves it's called enveloping or demodulation and then there's techniques like peak View and shock pulse and so on that specifically are designed to to detect this type of fault condition it they specifically look for the high frequency vibration they isolate that with silt ISM so and they use rectification and all these sorts of things we don't really need to talk about right now the point is they work and if we get a fault on the outer race of the bearing which is more common then as each rolling element hits it we get a certain ping of vibration and we can detect that in the high frequencies if on the other hand is on the inner race then we see something interesting happening here we get the periodic ping but you notice that it the vibration level rises and falls rises and falls and that is a periodic increase and decrease in the amplitude of that vibration that's because when the fault on the inner race is rolling over the top of the bearing assume the machines mounted horizontally there is less force in their impact as compared to when it's down below now that's all a lot of details the beauty of it is that if we see a pattern like that in our time waveform or if we see a spectrum with sidebands I'll show you some in just a moment then we can tell okay the salts on the inner race if on the other hand it's on the rolling element itself then we get a much lower rise and full of vibration let's just do that for a moment here we we see it a rise and fall in vibration it's just that it's a lower frequency of modulation anyway I've got some slides on them in just a second so the beauty of it is I can detect it at different stages one of the things now this this little simulates a little bit complicated but the thing is that as the fault develops we see fall condition develop by monitoring the very high frequencies and as the fault continues it gets you know as a fault gets worse and worse the frequencies generated become lower and lower so in the very early stages we're seeing very high frequency vibration so the envelope being techniques and the peak views and shock pulses and so on detect that but notice in the normal spectrum we're really not seeing anything really not seeing very much at all but as the fault develops if you continue to monitor it you might notice that you'll see some of this higher frequency vibration get into the lower frequencies and in fact if you use enveloping techniques that filter both at the higher frequencies and at the lower frequencies you'll notice that the higher frequencies will be sort of increasing amplitude first and then the lower frequencies but then as we go further the acceleration which is more sensitive to higher frequencies will will begin to change and we can see it in the time waveform and spectrum and we go further and our traditional peaks in the spectrum that I'll just explain a little bit more about in just a moment will start to develop as well so the beauty of all of this is that it enables us to get an estimate or an assessment or no approximation of how long the bearing has to live if we're just at acting these very very high frequencies we said great we can start thinking about the bearing we may need to order and you know we can we can look forward to down time that we have where we could replace that bearing but we don't need to do it now but when this fault gets quite bad there's a lot more noise and there's no high frequencies and in fact it starts to look like looseness now you know you have to act quickly so bottom line is that these enveloping and peak view and shock pulse and these sorts of methods all give us a nice early warning but notice the earliest warning we can get is actually when we detect the root causes of failure it's really important to understand the root causes like poor lubrication contamination of the lubricant excess load from unbalanced misalignment resonance and so on and poor installation practices the bearing being damaged when it's installed cocked on the shaft and so on but this will give a serious warning using acceleration and either looking at the spectrum or particularly the waveform we'll get a warning of the salt either later if we're not using this technique or as a fault gets worse and then we can look in velocity and last at all we can look at the overall level so the typical sort of RMS reading which is one number okay so that gives us an idea now I mentioned some of this already but just to say that first there is a fault on the outer race we will see a frequency that we call the ball pass at erase frequency its vpso and we'll see a certain type of pattern we expect when the inner race is tuned in that there will be vibration there will be harmonics so we expect to see a peak at that frequency and twice that frequency three times and four times this is whether we're looking at a classical sort of velocity spectrum or an acceleration spectrum or a spectrum of the enveloped signal itself bit peak view shock pulse or whatever it's only a question of exactly what sort of shape it takes and whether we expect to see one X and other kinds of Peaks there as well but the point is we will see this beacon will see harmonics it's non synchronous which means that the this frequency is not an exact multiple of the running speed of the machine so it might be 3.09 times or six point seven times or whatever it will be a non integer number there will be harmonics so there's multiples and under normal circumstances we don't expect to see side bands okay if it's on the inner race then we again expect to see harmonics we again expect it to be non synchronous but now we will see sidebands so now we've got these one x side bands on either side so there will be little Peaks on either side separated by the running speed of the machine now the Caged frequency is two and sometimes called the fundamental train frequencies the frenzy related to just the turning of the of the cage within the bearing if you see a peak at that frequency which is normally just less than half the running speed you need to take urgent action but the other reason for saying it is that if we see damage on the rolling elements themselves then again we see harmonics again they're non synchronous it's a different frequency to be PSO and be psi but now the sidebands are of the fundamental train frequency or that cage frequency okay so moving right along now we'll just have a quick chat about the fluid film bearing vibration analysis obviously fluid film bearings are also critical like rolling element bearings we need the rolling element bearings to keep on turning and providing providing great reliability same with fluid film bearings however a lot of our really critical machines like the steam and gas turbines and you know major pumps and major compressors and so on typically use these fluid film bearings so it becomes even more important that we monitor them correctly so few things we can't use the same techniques that we've just used for rolling them bearings for two reasons number one we can't rely on using accelerometers on those sorts of bearings the thing is that the as um you'll see an animation in just a minute the right now so inside the journal bearing so here's the bearing and there's the journal or it's a fluid film bearing because there's a film of fluid the oil that separates the journal let's just call it the shaft and the bearing so it's like what I'm trying to show in this animations it's as if it's riding on this wave of oil I'm exaggerating the motion as I do in all the animations but it's writing on this film now it means that this vibration is being cushioned and therefore if we have an ax seller ominous sitting up on the bearing housing somewhere we would be expecting this vibration this motion to be sort of transmitted through up to where the sensor is located and this this film of fluid is little wave under there really dead and that vibration we may not see very much at all so we can't rely on that technique and the other thing is too is we're not usually looking for impacts and for seeing impacts in something pretty serious is going on but we are interested in the health of the bearing itself you know if there were rubs or something like that going on well we're interested in that but we are also interested or particularly interested in the stability of this system so you know the idea is the shops turning around it's sitting nicely on this film of oil it's supposed to be in a certain location within the bearing for example shaft turning in this direction it's supposed to be just off-center to the right and sort of sitting in this area be hard to see from that animation because I've exaggerated the motion so much but that's what it does when it's stable it can become unstable and that can damage the bearing or damage the machine and they are conditions called oil world and oil whip so we want to monitor the vibration and the position of the shaft within the bearing to detect whether this is a problem now or could become a problem we are also interested in other conditions of the machine like unbalanced misalignment preload and other conditions so that you know we we are looking for the vibration it tells us about the health of the machine as a whole but also of of the bearings now we are also interested in let's just call the dynamics of the row to the rotor dynamics as you with a lot of these sorts of machines the machine might operate above the critical speed of the rotor that is that as a machines running up to speed the shaft will be into Flex kind of like a guitar string you know strums back and forward it's it's resonating the shaft itself is resonating and the machine operates higher than that speed so as it runs up we are very interested in in how its operating as it goes through that speed anyway so back to this animation there's a few things I'm trying to show here number one yep there's our a little wave of oil that the journal is riding on but in order to measure this vibration we use these two proximity probes this probe can measure that stands between the tip of the probe and this surface now again this is all exaggerated the clearances are much greater than the motions much greater than in real life but basically it can measure the distance and this one can measure the difference so it's kind of like triangulation if we can you know this distance in this distance that I can tell from moment to moment or the system can tell exactly how it's moving so in this case I'm showing a little orbit here I'll explain that in just a moment but it is moving in this in this circular actually elliptical motion and these two probes can tell us that because they're constantly measuring how that distance is changing it's kind of like triangulation in essence it's telling us how the center of the shaft is moving now at the same time we need timing information for the sake of the orbit and for phase and that's what this probe the key phasor that's what it's doing it's seeing the keyway as it rotates around and they're not all in the same plane so let's have a look at that okay now it's rotating in the opposite direction so for the confusion but in any case so now you can see that this probe is MA is mounted actually in a different location to these probes so here typically mounted near the bearing they are watching how the shaft is is moving so we've got an idea of what's happening in the bearing and we'll have these probes X or Y and X probes on each bearing and then we might have just one key phasor looking at this now in reality there might be multiple TVs approach for redundancy and some of that so that's another story okay so even though this motion is greatly exaggerated but as the machines vibrating with if there's any amount of unbalance anything then the shaft moves you know moves that circular motion it's just exaggerated in this case well those two probes let us measure how the shaft is moving and we can plot that on a graph in that cell orbit plot what this animation is showing is that potentially I could measure at other locations and I can see how the shaft itself is moving whether it's moving in this in this circular motion here where the center of the shaft is moving more than the ends now in reality I'm only going to have probes at the bearings some it may be difficult to tell exactly what it's doing but in any case just for artistic license this is how the shaft may be rotating as it goes through its first critical and we'd like to have an idea of what motion exists and that brings us to the orbit plot so here is the shaft measure I'm looking along it actually and what I'm going to do is just slow down the motion a little bit and turn on the procs probes and the key phasor so the probe could be mounted in this classical X&Y location or they may be you know located here it could be different configurations and and here we have the key phasor and again it could be mounted just about anywhere you need to know where the probes are mounted though of course but basically as the shaft turns the key phasor sees the key way or maybe a key in actual fact the two probes monitor the the gap which again is very exaggerated but we end up with two sine waves from each one from each probe and we can plot them against each other so X versus Y gives us this orbit and we might find that for example there's more motion in the x-axis and there's it wouldn't be exact sort of phase relationship as in wouldn't be exactly 90 degrees phase and we might see a bit of an elliptical motion as more movement let's say horizontally versus vertically bit of a phase relationship there and we might see elliptical motion this so much more we could tell you about these all the plots and exactly how they work with just trying to keep this webinar sure to give you a taste of all of this and hopefully tell you something that you weren't clear about before okay so what we've learned so far is how the shaft moves as it rotates and it's moving in this elliptical motion as we just saw and that is what the center of the shaft is doing that's the way to think about it what's what's the shaft doing so here it is now we've got it rotating counterclockwise and if you imagine a great big shaft with a crosshair in the middle that's what the orbits showing us how is the center of the shaft moving so what is that orbit telling us let's sort of zoom out a little bit there's our shaft the center of the shaft is is moving in that elliptical motion so that's great so that tells us that what it does not tell us is we're inside the bearing it's doing that so there's our bearing and right now I've got that more or less sitting in right in the center of the bearing it's moving in that elliptical motion now just so happens that if I knew that was actually happening I might be a little concerned because it shouldn't be there it should be down in this quadrant here for a shaft rotating in a counterclockwise motion like that the bearing has a certain amount of clearance you know the bearing the shaft contour the journal can't move outside that bearing and we represent that available clearance by this circle here and what we're building up here is a is a plot that gives you an indication of where the center of the shaft is located within the bear and this plot is called a center line plot so it's like the center of the bearing where is it within the bearing so if we click one more time you can imagine that you know it was our motion just before but it should be the center of the sharp should be rotating around a point in this quadrant not in this quadrant I'm certainly not up here now if you if you look closely as I attempt to drag the center outside of the yellow circle it won't go because it's bumping up against the edge of the bearing and as I move it around now that's that's the available clearance within the bearing the bearing could be more elliptical in shape there's different sorts of bearings we might have but to keep it simple you know there it is and you know when it's when it's rotating and moving in this of an orbital motion like that or elliptical motion there we are very interested in whether it's doing it here or over here or up there that tells us something about the stability the shape of the orbit tells us about the fall condition if it's highly elliptical it might mean that there's some preload if it's very round and quite large there might be some unbalance and there's lots of other fault conditions that we can detect by the shape of the orbit and the position of that or but if you like within the bearing tells us about the stability of the bearing look there's so much more we can learn about all of this we can look at the response of the machine we can look at a full spectrum we can look at the response we can see what happens as it runs through the critical speed this so much more we can learn but the orbit tells us an awful lot and from the X&Y waveform we can build a spectrum we can build the magnitude and phase we can build something called the full spectrum there's a lot we can do to tell us all about the machine now just want to tell you about a couple of things coming up we have category for vibration courses that really dive very deeply into all the topics we would just talking about that's the journal bearings rudder dynamics all that plots and all of that that is discussed in great detail in the category for course and we have one coming up in Dubai as you can see with these dates special course for what I like to call the superheroes of vibration the people that really get into the turbo machinery and rotor dynamics but also modal analysis learning about isolation mass stiffness damping you know it's like a very advanced cat3 if you like so all the things we learn and get through more advanced and rotor dynamics as well but what I also want to tell you about the conferences we have coming up we have a conference in Dubai coming up not-too-distant future one after that in Europe Australia and the United States these conferences are there to support you as a vibration analyst yes the training courses are great and yes there are free videos a lot from us but these conferences are a chance to meet other people just like you to talk to them about what they've learned from vibration analysis how they solve problems and so on but also to listen to presentations case studies great new technologies that are coming out there's social events is great exhibition and so on so we need your support because we're putting on these conferences to support you and at the conference in Dubai well actually before I say that we are offering a 10% discount to anyone watching this webinar all you got to do is register with the code in vac international machinery vibration analysis conference impact you do that 10% discount and if there's a few of you at your site that are involved with vibration analysis well if you registered two people a third person can come for free so it was about two a is that I will be delivering a few presentations there but also to half-day workshops one talking much more about how you detect rolling in the bearing faults lots lots of examples and all of that but also talking about how you prevent the faults in the first place what are all the causes of the salts and and therefore how do you prevent them and then in the second half day workshop going to much more detail about well the proximity probes the key phase of the orbit plots the center line plots the bode plots full spectrum and so on and if you were thinking about going to category 4 that would be a good workshop to to attend and maybe you can see how you feel about the topic afterwards and whether you're ready for a category 4 so I really hope you enjoyed this presentation I hope you learn something from it but I also hope to see you at the next impact conference

Channel: Mobius Institute

Views: 39,174

Rating: 4.9561405 out of 5

Keywords: vibration analysis, Condition Monitoring, Reliability, Reliability Centered Maintenance, RCM, CBM, Certification, Root cause failure analysis, Lubrication, Alignment, Vibration Analysis, Predictive Maintenance, condition based maintenance, IMVAC, fault detection, rolling contact, bearing, fluid film, CBM Connect, Mobius Institute, CBM Conference, The CBM Conference

Id: 67Et4vbKhOM

Length: 29min 58sec (1798 seconds)

Published: Mon Feb 06 2017