 So, far we have discussed about machinery condition mounting in the sense signal processing and then how through vibration mounting we are able to find out faults in mechanical systems. Now, we will begin the module 4 of this course wherein we will be discussing the other techniques of machinery condition monitoring that is normally the wear debris analysis as it is known as and then we have the other condition mounting techniques like the motor current signature analysis and how non-destructive test NDT techniques like you know ultrasonics, radiography, acoustic emission are also thermography are also used to find out faults in machines. Usually you know about 70 percent of the cases are in in condition monitoring are through vibration analysis and inversely throughout surveys in the industry it has been found that usually the other 20 percent actually belongs to this category which we will be discussing in today's lecture on contaminant analysis and then the subsequent lecture on oil analysis. How basically we analyze the oil the lubricating oil and the debris which are deposited in them by examining them we can find out whether the machine is deteriorating fast or slow and so on. So, I will be discussing on contaminant analysis as you know the tribology is a study of friction lubrication and wear in a mechanism or machines for example, when we have two machine members interacting with each other there is a normal force on to them and this surfaces may not be smooth as I showed you in the case of the bearings they may have a surface roughness and usually to and once these two components rub against each other because the application of load we actually put a layer of lubricant. So, the purpose of this lubricant is to reduce the friction I have to reduce friction because reduction of friction between two meeting machine members means that the forces of the power consumed to move them will reduce because of the friction friction can be reduced by closing this asperities in these surfaces by having this lubricants here. But in the process what happens these particles here also wear out because of loading because of abrasion so on and these particles wear particles get deposited they get deposited in the lubricating oil. So, two very important things happen because of this process in any machine. So, this happens in any or every machine meeting members example gears meeting shaft and bearing could be bush could be journal could be anti friction. So, when two materials meet against each other they rub against each other there will be lot of heat generation and because one may be softer than the other. So, it is going to wear out like when you have an eraser rubbing on a piece of writing you know you those rubber flakes peel off the eraser. So, what happens is two important things happen number one because of such an process the wear particles or which we call them as the contaminants get deposited in the oil. So, the concentration of the wear particles the nature of the wear particles the rate at which they have been deposited in the oil gives us some clue as to what is wrong with the parent material from which they have worn out because of may be excessive load because of less lubrication because of temperature effects. So, these are factors which are responsible for the wearing out of these particles from the meeting members. Now, understanding where these wear particles came up came up from we can know whether the parent material was may be poorly designed was of a softer material was did not have proper heat treatment was not lubricated was subjected to higher temperature. So, these are the scenarios which we need to investigate and then also knowing from the chemical composition of the wear particles if it has say for example, if it has come out of a general bearing if you see lot of zinc or tin or lead we know this bearing is wearing out faster than it supposed to be. So, this gives us indication as to how why and how or how quickly the machine is deteriorating. Then the next of course, happens is once this wear particles get deposited in the oil will undergo a change in its physical and chemical properties because the virgin oil you know by mean virgin oil I mean the oil which was you know new and which has not been used in machine. It has certain physical properties like its density like viscosity like its oxidation number etcetera. So, once these contaminants get deposited in the oil it will its properties are going to change its properties are this properties are going to change this properties change. So, if somebody monitors this properties we will know that something has gone wrong with the machine it is very similar. So, this contaminant analysis which you are going to discuss in today's lecture and in the oil analysis in the subsequent lecture basically they are like pathological tests which we do when we go to the doctor like we do an urine analysis or in the blood sample analysis. Similarly, for the machines we also need to look into this wear particles and oil analysis. Now, throughout the world worldwide I should tell that again 70 percent of CBM condition based maintenance is done through vibration monitoring and these are from statistical information which is available in the literature. And 20 percent is what is known as the wear and debris analysis which is essentially nothing but the contaminant analysis and oil analysis. And the remaining 10 percent is other techniques and that makes it 100 percent. So, in this other techniques I have what is known as the motor current signature analysis then we have what is known as the thermography then we have the ultrasonics some of them are the and non-destructive test techniques like X-ray or radiography acoustic emission then we have dye penetrant test then we have boroscopy etcetera these are the non-destructive NDT. So, this form about 10 percent of the CBM throughout the world recently what has happened this motor current signature analysis has become leading technique in finding out CBM and we in IIT Kallapur have done some of the pioneering research in motor current signature analysis to basically find out faults in mechanical systems using the current drawn by the electrical motor which is driving either the gearbox or the mechanical driven unit. And details about this research can be found in my website and in fact in the subsequent classes we will be referring you to some of the experiments on literature which we have published in these areas. So, what today as I was telling you we will focus more in this contaminant analysis in this class. So, with this kind of an preview let us see what is this contaminant analysis we are going to talk about. So, as you will see here the contaminants or the wear debris have certain characteristics one is the quantity of course, if the quantity is high in a given composition usually they are measured in parts per million say this wear debris are measured in PPM parts per million. And if you will know if you go back to the familiar bathtub curve what is going to happen is you have the infant mortality zone and then the uniform failure rate and then towards this end you have this wear out zone. And what happens suddenly at a given time if you see that the wear debris parts have increased or increasing with time you know that the defect severity has increased. So, in the laboratory where you do the contaminant analysis by the way this contaminant analysis etcetera cannot be done in situ that means next to the machine like when you have vibration monitoring you just put a vibration transducer next to the machine and record the signal and do an analysis and tell the where the fault is in contaminant analysis or in oil analysis you cannot do that all is you have to collect the oil like we collect on blood or a urine sample and send it to a pathological lab similarly in this machines also you have to collect the oil in which the contaminants are there give the entire sample to a lab where in they will be doing the contaminant analysis they are in where they will check the severity by calculating the quantity of the particles present for example, in every month you see the PPM of may be zinc in a machine component. So, in the first month end of the first month, second month, third month, fourth month, fifth month after every month you will be collecting the oil sample and giving it to a lab and suddenly it began with you know this is about you know two parts from three parts again two parts this could happen because of measurement error once it is three then again it is coming down, but you know four five and constantly five and then you see suddenly and you see towards the end this is when you need to be get alarmed because of high levels of zinc well, but then you may be wondering who decides who decides what is an alarm level well, this depends on many things this depends on the machine of course this depends on the operating parameters like speed, load, temperature machine could be a gear box, blower etcetera. So, for these there are standards, there are standards or industries have made their own standards based on their experience they say you know if I get more than 15 PPM of zinc I should be alarmed that the machine has undergone a severe failure. So, this severity is actually the severity level of the alarm level is actually decided by the user himself or herself. Now, what happens the next point is size of the particle you know we are getting size of the particles you know this where debris are they come in many forms you know one could be laminar strips, one could be irregular shaped particle, one could be spears, some could be curled strips because this actually leads to the morphology of the where are particles, but the rate is very important because what will happen we have some having may be 5 micron size suddenly if the surface has worn out so much that I am getting large boulders large spears. Good example of this is you know you have a fresh road nicely metal road and then initially you know you have lot of loose asphalt and with time you will see suddenly you will get big chunks big spears big rocks loose asphalt small rocks then you have big rocks then you will have you know boulders coming out. If you do not treat this road asphaltic road no treatment is done with time because of weathering conditions you will initially have loose asphalt coming out then the gravels and the rocks then the big rocks followed by boulders. Similarly, so the same thing happens in machines as well you will have you know small strips coming out small spears coming out if it goes untreated you will have you know big components coming out big spears coming out and so on. So, the size will decide on the rate of severity of this where depth is ok. So, with time you will see that the particle size may be it was 5 microns to begin with and then it became 20 or 10 microns and so on. Next is the morphology the mode is whether it the shape is laminar like strips whether it is curled whether it is pure whether it is irregular you must have noticed this while you do machine in the laboratory in the workshop when you use a lathe machine to machine surfaces. The chip morphology tells us regarding the type of machining I am sure all of you must have seen while you while you machine from mild steel specimen you will get curl chips ok when you have cast iron you will get broken steel pieces. There is no continuous strip here, but here you will get broken steel. So, this tells us about the operation of course you know here we are making it happen, but in machines because of wear and tear we will get this particles coming out. So, some particles could be like a sphere some particles could be like a strip some particles could be like a sphere some particles could be curled curved some particles may be having lot of holes on them and so on. So, depending on the morphology of this way or not particles you know of course you know we cannot see them in our naked eyes. So, we need to use optical microscope to begin with and then we have to magnify them to see them. And then the most important part is the composition of the wear debris particles the composition of the wear debris particles will tell us what is the parent material in terms of the composition whether it is in a lot of iron lot of zinc lot of chromium lot of sulphur lot of silicon ok. We know for example a good example is silicon ok the sand grains or the dirt actually have silicon silica. Suddenly in the contaminants I find lot of silicon or sand grain coming up I will know that means lot of foreign dirt has gone into my machine ok. So, these are little size if I know the parent composition of the material and I know that in my wear particles a certain elements composition is increasing I know in a given machine from where this particle has come out and which component in this machine is deteriorating that knowledge will be known to me. So, this wear mechanisms are many ok. For example, when the particles are meeting one may adhere to another because of temperature because of load and then because of rubbing they may try to bring out pull out surface of this material there could be lot of abrasion because one is hard other is soft they could be using as an abrasive ok. And this abrasive happens in normal machines not that this is bad this happens only thing is that whether the rate at which they are happening is more whether I could do something to arrest them. For example, if you think of a journal bearing if you are abrasion is so because usually the bearing journal bearing the inner liners are much softer than the shaft material. So, when in process of abrasion the soft being a hard surface is going to wear out the inner bearing surface. Now, imagine if this inner bearing surface is wearing out faster the bearing clearance is going to increase. Now, this clearance increases you know the Z n by P that is going to change and then the from the summer field equation you will see that the load carrying capacity of the bearing is going to reduce. So, some machines are designed of course, you know one machine one component will be hard another will not be hard, but that does not mean that abrasion wear will not take place in normal times abrasion wear will take place only thing is that we should be worried that the rate of abrasion is not excessive. So, that it creates a condition wherein my blaring clearance has increased and this bearing is not able to sustain the load which is given to it and of course, in other delamination occurs and fatigue because of the load reversal or the load cycles fatigue kind of wears happen and another important thing is corrosion or oxidized knockers because of an environment this corrosive things can happen and electrical attack happens particularly when there is a electrical loop or the ground voltage going through a machine and because of this lubricating oil you know this electrical attack actually happens particularly think of the case of an electrical motor and there is a rotor this here is a rotor of course, there is a stator I am not drawing this stator here what happens because of this there is always a small amount of voltage loop which is going on. Now, at this interface there is a lubricant either if it is a journal bearing or a ball bearing there is a thin layer of lubricant between the inner races outer races etcetera and this actually is actually a dielectric. So, when I am bringing in a voltage across a capacitor and there is a dielectric this dielectric breaks this voltage is going to get pass through. So, this intermittent passing of this EMF will create a spark because there is a potential. So, this sparking comes with high energy of heat momentarily heat. So, this is going to produce lot of pitting on the surface pitting on the bearing surface I will show you in the next class some pictures of what happens when this bearings pit. So, lot of pitting marks will come on the walls of the inner race or the outer race because of an electrical discharge going through the circuit. The usual way to avoid it is you know have a good grounding if you ground it this does not happen I will show you some. So, but then this are responsible for the initiation of the pitting and if this goes once the surface has got pitted because of load and temperature they are weakened and then with time there this small pitting will be bringing will become large scowling will occur and then lot of large chunks of the material are going to get eroded. So, surface are going to get worn out again. So, one has to be very careful when designing electrical motors or particularly when we have high voltage electricals in your machinery is wherein there are parts in which there are lubricant and then when there is a disconnect. We may not get in voltage as you measure, but when they are going at high speed because of this EMF if the grounding is not proper we will get this parts and this parts are responsible for actually like an erosion or like an EDM like an electrical discharge is occurring. In fact, people use this high voltage parts in electrical discharge machining to machine surfaces, but here the same EDMs may be harmful to our machines. But this wear modes you know when we have an initial in the infant mortality zone of the bath structure we have the usually running in wear modes because of the maybe it was not properly aligned maybe the surfaces were having lot of bad surface finish to agree lot of the machined surfaces were not clean and these debris were there which is then followed by your steady wear and then we have the wear out towards the fag end of the life of the machine. We will have a severe wear out followed by pitting and then if pitting goes unnoticed we will have large materials coming out which is known as scuffing. Now usually this wear particle types you know are drawn few of them like the laminar ones or the irregular shape or the curl shape. The typical size of this wear particles you know could be cutting could be spherical if it is rubbing it is usually less than 15 micron. By the size I mean if you see under the microscope one of the dimensions this happens to be 15 micron this has to be only seen through microscopy microscopes. But normally usually we use an optical microscope of about 1000 magnification. So, with that we can see sizes of about no maximum about 5 micron. But and usually this wear particles are of bigger sizes and then you will see sliding is usually 20 to 50 microns laminar fracture is big severe sliding is big 50 micron etcetera you can see it in an optical microscope even 200 or 500 zoom magnification. But the wear debris particles to understand the chemical composition we require the wear particles will be of the order of less than 2 microns and this is not possible by optical microscopes this has to be seen through an SCN scanning electron microscope. So, obviously as you as I was telling you no in situ analysis is possible in case of this wear particles. So, what we do basically there is a technique now if you look at this contaminant analysis depending on the size of the particles we can have different modes of investigation. If the particle size is less than 2 microns I will use what is known as spectroscopy if it is between you know 5 to 30 micron I can use what is known as the wear debris analysis and if it is greater than 30 micron I can use what is known as the particle count. And usually there is a method known as ferrogram or ferrography wherein we have iron wear particles. So, actually all these contaminants are actually deposited in oil basically the lubricating oil which is there between the two mating members actually uses we use that in oil to understand this contaminants. This oil can be taken dried in a piece of on the floor put on a place of paper and then with an magnetic field or a gravity field it can be laid in such a way that the heavier particles are going to get deposited in the bottom and the top particles on the top. So, you will see a ferrogram like this on a surface like this this could be large particles and then toward the end it will be small particle this is a ferrogram and ferrogram you can measure you can see it in a microscope and see the nature of the nature and size and also then try to understand how severe your wearing mechanism is. So, if you look at the characteristics of wear particles in a ferrogram usually normal rubbing wear means you know which occurs are like flat plates plate plates like less than 15 micron. If the wear becomes severe and sliding will have flat elongated particles greater than 20 microns with striations there will be lot of striated marks cutting wear long curl strips of metal which you must have seen in your workshop gear wear flat striated particles bearing wear laminar plate plates spears small particles less than 5 microns black oxides indicates insufficient lubrication red oxides indicates water contamination corrosive wear becomes because of heavy concentration of fine particles aluminium wear white metal particle when there is dust or dirt foreign particle or material not characteristic of machine or oil. So, what happens these are the particles which we see from an macroscopic level under an optical microscope and just only looking at the size and the shape we can we can have some clue as to what kind of wear took place what kind of contamination took place is it water contamination is it contamination with dirt or sand in your machine this can be done. But this analysis never tells us about the chemical composition of this wear particles whether it is made out of iron whether how much of parts of copper is there how much parts of zinc is there for that we have to do what is known as spectroscopy. Before I go into spectroscopy I will tell you some of the wear debris analysis methods and basically wear debris are done for particles which are above 5 microns and beyond. So, I could seat under an optical method I can have a light beam pass through an oil which has this wear particles and because of the density of the air particles increasing this light is going to get reflected and this can be detected by a photo detector. So, the intensity of the light reflected back gives me a clue as to how much percentage of that opaque surface of wear particles are there in that oil. So, in a given milliliter of oil I can have an estimate as to how many parts per million of solid substances are there filter blockage I can have a pore or a mesh size and then like a normal sieve I can say you know 5 microns state back and I can this is the parts per million of 5 microns and if I increase the sieve size may be you know 10 microns 20 microns and so on I can do wear particles can also be measured through radioactivity through thin film sensors like magnetic attraction is by ferrography or the gravimetric which I just described the last slide. But to know the chemical composition of the wear particles we have to do what is known as the spectroscopic techniques for debris analysis this debris and mind you they have to be sizes less than about 2 microns which are not possible to see obviously on naked eye even with high power magnification may be 100000 X magnification you may at most see about 5 microns. But beyond that we have to use what is known as this fine particles we have to use we need not count the number of parts per million, but rather find out the chemical content of these particles and that is done through all these techniques and these are all specialized equipment like the atomic absorption spectrophotometer known as AAS, atomic emission spectrophotometer AES, XRF, inductive coupled plasma ICP, DCP, EDX etcetera. These are very very sophisticated equipment each of these equipment could be costing anywhere from 50 lakhs to 2 crores each of these equipment. So, obviously when I have a plant with the gear box worth only 50000 rupees or a 1 lakh rupees it will be not economical for me to have in my plant all these machines. In fact, none of the engineering industries have these where they do regular plant operations, but to analyze or to know the condition of this machine this oil which have been collected from their gear boxes or you know pumps etcetera has to be collected and sent to a centralized laboratory. Where in this laboratory people can do analysis using this sophisticated equipment and I will just tell you briefly about one of them the atomic absorption spectrophotometer. What happens is you know this 2 micron samples which are there, they are heated to such a high surface that we have plasma coming out of it. Then you know E is equal to H nu from the flanks law of radiation and this energy which is emitted is at the wavelength or is at the frequency of the radiations of the chemical elements present in this in this where particles for example, suppose it has iron, suppose it has zinc, copper etcetera. So, the radiation of these elements of this atoms electrons in an iron if it goes to an excited state it goes at a particular frequency same is true for zinc and same is true for copper radiation at its characteristic frequency. So, all I have to do is at that characteristic frequency I have to measure the intensity of the radiation and that is what is done through an atomic either absorption or emission spectrum. So, basically I have a sample which is heated and then radiations will be there, I will have another source wherein I will be giving the from a concentration from a known concentration. I know some x p p m, I know the amount of light intensity. So, I will see the unknown light intensity which I will measure which has been radiated out to this element and then from by inertial method find out what is the p p m. So, I have to know for the particular element I am trying to identify I will I need to know its electromagnetic radiation frequency. So, there are all standards which are used standard light sources are used used to identify the chemical elements. So, typically the elements in the spectroscopic spectrometric analysis where elements these are easily iron chromium aluminum copper layer these are the where elements which happens and sometimes we give certain additive elements and then these are usually the contaminants silicon, sodium, boron and vanadium. And one of course we need to know in the engineering applications of machines what are the typical where elements and from aluminum to silicon and what is the probable origin. So, for example, if I see lot of aluminum I know these are the possible sources where in aluminum is there. Suppose I see chromium these are the possible sources could be the exhaust valves etcetera or shafts and when I say silicon I know it is ingested dirt, sand, sometimes gasket, silents, oil, antiform, antifreeze additives. So, these will be known to us from the original designer. So, to know the material of the element and then look out for these. Sometimes in many machines which are just available to us its material composition is not known to us sometimes it is a difficult thing, but with experience if you will see that you know usually a particular component is coming out we can do diagnostic measures to find out where what is the source of this material. So, this is only possible by spectroscopic spectrometric analysis wherein we have copper is usually coming out of bearings, lead is also coming out of bearings and everything of course, in the industry is made out of iron and silver particularly in respite embossions, antifrictions, silver, solder etcetera. So, this gives us a clue as to what is the possible source of the element detected by spectrometric analysis and usually this is the composition of the components which are there in the machinery. One is iron, chromium, nitrogen, molybdenum, manganese, lead, copper, zinc usually in bearing cages it is which has high copper and zinc as you can see. If you have rolling element bearings it is high iron, gears very much iron, shafts iron, gear box casings. Sometimes you will see this manganese etcetera and this kind of metallurgy is only available by doing an spectroscopy of a sample. So, you give me a piece of iron it is not 100 percent iron. So, it will may be an iron coming out of a gears may be only there is chromium, there is nitrogen, there is nitrogen, high nitrogen because of the case carburizing with or nitriding. Now, the gear surfaces are hard because of the initial high levels of nitrogen are there. So, suddenly in your contaminants if you see high level of nitrogen you will know well my gear is varying out faster than it should be. If I see high amounts of may be zinc I will can know it is high amount this bearings which are varying out faster. So, this kind of clues give us an indication as to where from this materials have come out of. So, to summarize in this class on contaminant analysis you have seen what are the different types of contaminants available. Contaminants can be distinguished in terms of their size something less than two microns we cannot see them through a very high power magnetic sorry magnification of 1000 x we have to do spectral analysis. This spectrometric analysis is done through atomic absorption spectrophotometer or emission spectrometer emission spectrophotometer X RF ICP etcetera wherein we need we get to know the chemical constituent of that O naught particles as to how much percent of the iron is there copper is there zinc is there lead is there nitrogen is there and all we have to do is regularly in a frequent interval we have to see the chemical composition of the where particles. I am not asking you to rub off or scrape off a material from a nice machine, but what is already deposited in the oil which is there as a lubricant. So, then from this contaminants we can try to get as to clue what is the parents source and why this is varying. Next comes the size the bigger sizes about you know 5 microns or greater we can then look into the through microscope we can see the size shapes whether they are laminar whether they are spherical whether they are curved whether they have striation marks whether they have irregular in shape cut shape. So, this gives us an indication as to with the where mode whether it is addition abrasion whether it is corrosion whether it is because of an electrical interference etcetera. So, these gives us to an understanding of the where modes and next comes the sizes are large and then they are ferritic we can develop ferrography and then do ferrograms, but if they are sizes more than may be 30, 40 or 50 microns we can just use an optical source and just do a particle count as to in a given liquid what is the parts per million of the where particles nothing to do about the content of the composition of the where particles, but whether is it 50 p p m in a given ml of the liquid is that concentration of where particles increasing with time if it is increasing we need to get alarm. So, this is how the contaminant analysis helps us in identifying the severity of defects or the where mechanism and machine and of course, the other sister measurement technique of this is the oil analysis which I will discuss in the next class. Then examples of contamination just as a closer we will have the mining usually if you go to a mining it is the stone dust ore or water process plant is it will process material dust water lot of water comes in this mining process plant and querying component manufacture ceramic will have lot of clays and chemicals. So, this also gives us to clue as to what happens. Thank you.