Tribology And Maintenance Of Machinery - A Review
Indian Journal of Production and Thermal Engineering (IJPTE)ISSN: 2582-8029(Online), Volume-1 Issue-2, June 2021Tribology and Maintenance of Machinery - AReviewChandan ChattorajAbstract: The present paper considers the tribologicalprinciples on the maintenance of machinery whose threeimportant areas are – Preventive, Condition Based and Proactive.Although breakdown is kept out of view, the morphology andanalysis of failure provide important inputs for maintenancestrategies. Condition based maintenance depends on three D’s –Detection, Diagnosis and Decision. In many machinery systems,the problem of predicting the remaining useful life – the Proactivepart of the program, and evaluating the cost benefits are ofenormous importance. Here the authors endeavor to highlighthow the tribologist can significantly improve the maintenancepractice.Keywords: Tribology, Preventive, Condition-based, Pro-activemaintenance.I. INTRODUCTION‘TRIBOLOGY’ a word of recent origin is a study of Friction,Lubrication and Wear. The British Lubrication EngineeringWorking Group (1966) put it as “the science and technologyof interactive surfaces in relative motion and the particlesrelated there to”. Whatever may be the genesis of the word,the question of friction, lubrication, and wear werereasonably understood by our fore fathers, even before thebeginning of the history.Friction is helpful in many types of machinery for theiroperation; it is astonishing to learn that about one third of theglobal energy production is wastefully drained out by frictionalone. Friction and wear are inseparably connectedphenomenon and considering the fact that world economyrests on energy efficiency, tribology has gained a position ofsupreme importance today.In this presentation the tribological aspects andmaintenance practice are co related to ensure that criticallyoperating machinery fulfils their intended function and tocontinue for pre-expected life time.Possibly no industrial unit can afford to throw away itsmachineries i.e. capital resources, unless they have beenutilized to their fullest extent of life with maximum reliabilityand performance. Hence the concept of Maintenance arises.Many people had defined the term maintenance in differentrespect. But the following flowchart (fig: 1.1) defines themaintenance in a generalized view:A. Maintenance practice – a reviewPrior to World war II, the maintenance of machine wasperformed on the break down principle. In this sort ofpractice the machines were the machines were continuouslykept in service until it could not continue its normal functionany further, which means “Don’t fix it, until it is broken”.During this concept the human senses like eyes, ears, smell,touch and even taste was considered during observationduring observation. But this would lead to disruption ofproduction plans as the type and the type of break down are ofrandom nature and may even cause loss of life. Meanwhilethe concept preventive maintenance was evolved duringwhich the equipment were regularly investigated on the dailyweekly, monthly or shutdown basis. During this, the faultyparts were get repaired/replaced, improving the life of theequipment.II. TRIBOLOGICAL PRINCIPLES APPLIED TOMAINTENANCE PRACTICE:Manuscript received on April 10, 2021.Revised Manuscript received on April 14, 2021.Manuscript published on June 10, 2021.* Correspondence AuthorChandan Chattoraj*, Professor, Mechanical Engineering Department,Dr. B. C. Roy Engineering College, Durgapur, West Bengal, India, PIN:713206. Email: chandan.chattoraj@bcrec.ac.in The Authors. Published by Lattice Science Publication (LSP). This is eval 2010.061221Journal Website: www.ijpte.latticescipub.com16Published By:Lattice Science Publication Copyright: All rights reserved.
Tribology and Maintenance of Machinery - A ReviewBut this concept was further modified as it was not taken careof abnormality and sudden change of the equipmentparameters. This background developed a new concept inmaintenance practice well known as condition-basedmaintenance in which abnormality of machineries andchange-in equipment parameters were taken care of inaddition to preventive maintenance. Some industry hadadopted the new concept in demand, proactive i.e. root causeanalysis for predicting the remaining future life of anyequipment.All these concepts may be used by any industry alltogether or individual one. This is totally depending upon thewhole spectrum of the industry i.e. the type of businessinvolved, the type of machinery deployed and the workforceavailability – skill level and turnover of staff. Thesignificance of adopting these approaches is to find an answerfor the question of “fail to fulfill its function”, and what maycause that “loss of life”?III. FAILURE ANALYSIS:The term ‘Failure’ is widely used to indicate the loss ofability to perform specified function. To identify and isolatethe causes of failure an analysis is often carried out in threefunctional areas – design, production and end-useenvironment. The failure pattern, frequently described as thelife cycle from cradle to grave, commences with a highincidence of infant mortality exhibiting high failure raterelated to tribological components such as wear debrisproduction rate, intensity of noise, etc. This is followed by aconstant or slowly increasing failure rate and finally by awear out zone, where component replacement becomesessential.B. Tribology - its principle:Friction, Wear between mating surfaces, and Lubrication–these are three major areas of tribology. As the technology isdeveloped the modern machines are designed for “providingmore power”, in a small size. As a result, very small areaavailable in the contact of mating surfaces to transmit therequisite increase in load at high speeds. At higher speeds theinstability and the temperature rise are the main two threatsfor the continued smooth operation. Due to limitation forimproving the properties of the material (mating surfaces andlubricant), friction and consequent wear will increase, with acorresponding rise in temperature and removal of surfacematerial leading to either seizure or instability due tounacceptable wear. To overcome this drawback thelubrication theory was developed.In the later 70’s when there was a relative increase inthe cost of energy arising from the energy crisis the clearindication was to conserve energy and raw materials byimproved design applying tribological principle. But thattime very few industries were realized/aware the necessitiesor possibilities for improvement in their practices byapplying tribological principle. Even they are not sure todecide which machinery health monitoring techniques werebest suited for their purpose. Now industries have realized thesafety as the highest priority, therefore more concentrationhad been given to the maintenance practice.C. Tribology and Maintenance:Now-a-days the concept -“Prevention is Better than Cure”is applied along with the outcomes of tribological research,for manufacturing components with improved design. Withthis application a marked change in the performance ofmachinery is observed. Throughout the major areas ofmaintenance activity, tribological principles (table:01)applied are – Preventive, Condition based and Proactive.Retrieval 2010.061221Journal Website: www.ijpte.latticescipub.comTo determine the most probable causes of failure thefollowing steps may be followed:a) Thorough inspection of the machinery and failedparts.b) Study carefully the changes in mechanical andchemical properties of the failed parts in thelaboratory.c) Collect the relevant data from eyewitness andcompare it with the data related to operatingcondition.d) Study all the parameters inthe design space.17Published By:Lattice Science Publication Copyright: All rights reserved.
Indian Journal of Production and Thermal Engineering (IJPTE)ISSN: 2582-8029(Online), Volume-1 Issue-2, June 2021 e)Reliability function R (t) exp [- [( ) x (t′ ) dt′] exp[-(t/ ) Identify the most probable causes and compare it withthe pre-designed parameter envelope.f) If it violates, create a new set of parameters for thedesign space, otherwise store information for futurereference. Probability density function f(t) -[dR(t)/dt] ( ) x(t ) x exp[-(t/ ) Mean Time To failure (MTTF) t f(t)dt ( ) 0 [MTTF t f(t)dt [ ( ) x (t ) x exp{-(t/ ) t dt00Let y (t/ ) then dy ( ) x (t ) dt, MTTF t e-ydy, since t y1/ we have0 MTTF y1/ e-ydy ( ) {since (x) yx-1e-ydy } ]0For example, a compressor experiences the followingfailure rate function:ln(FR) -0.1.ln(t) C , -------------(i) C, ---------------------------------------------(ii) ln(t) C, ---------------------(iii) F t1 t2 ( ) t1 t2 886.23 hrst1 t2 can be calculated from log-log plotequation (i), (ii) and (iii) can be simplified by imposing thegiven conditions.ln(FR) - 0.1ln(t) 1.39 --------------------(ia) 0-----------------------(iia) ln(t) - 13.12 ---------------------(iiia)The mathematical relation between the failure rate and time isgiven by,FR ( ) x (t ) for 0, 0, t 0where is a shape parameter, in the burn-in region inthe useful life 2 andin the wear-out zone is a scale parameter tat influences both the meanand the spread, or dispersion of thedistribution.However, taking natural logarithm on both sides yields,ln(FR) ( )ln(t) ( ) [ln( ) 2ln( )]ln(FR) ( )ln(t) C -------------------------(i)where C is a failure parameter which is a function of and in the burn-in region in the useful life 2 andin the wear-out zone Retrieval 2010.061221Journal Website: www.ijpte.latticescipub.com18Published By:Lattice Science Publication Copyright: All rights reserved.
Tribology and Maintenance of Machinery - A Reviewprobability of failure before the next major overhaul. Mostcritical repairs get the highest priority during minor overhauland less critical repair is deferred to the major overhaul,reducing the overall down time.IV. WEAR DEBRIS ANALYSIS:Wear debris analysis was first developed in U.K by means ofMagnetic Debris Plug (MDP) in the lubricating systems. Butthe most significant development was the ferrographytechnique. By this technique the morphological characteristicof the debris is identified and compared with the standardobservation charts. Debris analysis gives the idea of type ofwear that is occurred, by the worn surface and the size of thewear particle. It also ensures about the mode of wear (i.e. dueto rubbing, cutting, severe sliding or any other mechanicaloperations) from the size and surface of the debris.For establishing a definite relationship between differentwear condition and their associated wear debris generally aprogrammed base database is developed. Regarding thisprocedure a large number of tests are performed on the samemachine under different operating condition on theprobability basis, and a comprehensive wear particle database was acquired. A monitoring technique of debris analysisis shown in figure 06.A. Preventive maintenance:It can be termed as planned maintenance of the equipmentconducted periodically to locate faulty condition and takepreventive actions to avoid or minimize chances of delay,thereby, this method ensures long and safe working of theequipment without any mishap. As the preventivemaintenance is based on overhauling time, previouslyexperienced and expected life of wearing components, theaction may often be taken before it is really necessary andreliability of the equipment is ignored. This technique doesnot guard against unexpected deterioration between overhaul,as there is no monitoring system is provided. Hence thedevelopment of different concept in maintenance systemarises.B. Condition Based Maintenance:In condition-based maintenance the monitoring systemplays the most important role in detecting the condition ofmachine. Condition monitoring will provide the regular datafor assessing the machine condition as well as to aware whenprecautions will have to be taken. The merits ofcondition-based maintenance are:i) Increasing reliability by reducing the probability ofsudden/unexpected failureii) Increasing the time interval between consecutiveoverhaulsiii) Reducing un-necessary replacement of machine partsV. CONCLUSION:The most commonly used monitoring system (table:03)related to tribology is:The effective maintenance of machinery lies primarily inapproximately communicating knowledge of its tribologicalbehavior and the practical consequences in relation to failureanalysis. Implementation of three D’s – Detection, Diagnosisand Decision in the field of maintenance of machinery mayhopefully ensure safe, reliable and efficient operations andhelp any industry to achieve profitable value return amongstcompetitive.Finally,1. Application of tribological principles onmaintenance of machinery help to predict theremaining useful life of the failing machinery.C. Proactive Maintenance:It is a combination of condition-based maintenance and thedata available from the previous failure. The raw data werecollected from monitoring system and compiling with theprevious failure data, prediction of the remaining life of amachine can be made. This is generally done on the basis ofRetrieval 2010.061221Journal Website: www.ijpte.latticescipub.com19Published By:Lattice Science Publication Copyright: All rights reserved.
Indian Journal of Production and Thermal Engineering (IJPTE)ISSN: 2582-8029(Online), Volume-1 Issue-2, June 20212.3.By balancing preventive, condition-based andpro-active maintenance practices availability ofmachinery can be improved.Total expenditure can be minimized by reducing thespare part stock.ACKNOWLEDGEMENTThe authors are highly indebted to the authority, Dr.B. C. Roy Engineering College, Durgapur for kind help andsupport. The authors express sincere thanks to theMechanical Engineering Department for their help andsupport.REFERENCERoyalance B J, ‘Machine failure and its avoidance – what istribology’s contribution to effective maintenance?’, Proc. Instn Mech.Engrs Vol. 217 Part J: J. Engineering Tribology.2. Bachschmid N., Pennacchi P. and Vania A., ‘Identification ofMultiple Faults in Rotor Systems’,Journal of Sound and Vibration,Vol.254, No.2(2002), pp327-366.3. Platz R. and Markert R., ‘Faults Models for Online Identification ofMalfunctions I Rotor Systems’, Proc. Of Surveillance 4-Acousticaland Vibratory Surveillance Methods and Diagnostic Techniques,Compiegne, France,(2001), nance’,1991(Butter-worth-Heinemann,Oxford)5. Hunter R.C., ‘Engine failure prediction technique’, Aircraft Engng,19756. Seiffert W.W. & Westcott V.A., ‘A Method for te study of Wearparticles in lubricating oil’, Wear, 1972, 21, pp27-42.7. Williams J.A., “Engg. Tribology”, Oxford University Press, NY,19948. Andras Z Szery to ,“Fluid Film Lubrication, Theory and Design”,Univ Press, 1998.9. Majumdar B.C., “ Introduction to Tribology of Bearings”, 1ed,1986,a.h.wheeler, India.10. Reshetov D.N., “Machine Design”, MIR PUBLISHER, MOSCOW.1.AUTHORS PROFILEDr.Chandan Chattoraj, is Professor ofMechanical Engineering Department, Dr. B. C.Roy Engineering College, Durgapur. Hecompleted his B.E. and M.Tech from NITDurgapur. He was awarded with University GoldMedal. He also received his Ph.D from NITD. Heauthored many research papers in International & National Journals.He authored a book - Theory and Applications of Robotics. Hismajor research interests are Dynamics of Machines, Rotordynamics,Robotics.Retrieval 2010.061221Journal Website: www.ijpte.latticescipub.com20Published By:Lattice Science Publication Copyright: All rights reserved.
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