condition monitoring of deep groove ball bearings · importance because of its advantages over...

CONDITION MONITORING OFDEEP GROOVE BALL BEARINGS

J. S. Tripathi1, J. F. Agrawal2,1Research Scholar Bapurao Deshmukh College

of Engg. & Technology, Sevagram, Wardha,(M.S.)2Shri Sai College of Engineering & Technology

Bhadrawati, Chandrapur (M.S.)

July 24, 2018

AbstractBall bearings are considered as most important mechan-

ical components or factor in kinematics rotating system. Ittransmits rotational motion between fixed and moving partsas well as it provides support to rotating shaft. In most ofthe cases inner ring is moveable and outer ring is fixed. Insome cases inner ring is fixed and outer ring is moveablethat is vice versa. Condition monitoring has been gainingimportance because of its advantages over traditional main-tenance methods. Even though it has been costly, it hasbeen capable especially in continuous processing plants orindustries, where down time costs are very high. In thispaper, an effort is made to monitor bearing faults. In con-dition monitoring, through vibration analysis, it has beenpossible to predict different types of defects having differ-ent characteristics and would reveal the details of defectsand inaccuracies so that it could be minimized, by doingpredictive maintenance which leads to increase the plant ef-ficiency. Condition monitoring through vibration analysisis non destructive technique (NDT), where for diagnosingthe fault there is no need of stop the machine.

Key Words:Ball bearings, rotational systems, nonlin-ear spring, dynamic behavior, vibration analysis, ConditionMonitoring, Maintenance.

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International Journal of Pure and Applied MathematicsVolume 120 No. 6 2018, 10173-10187ISSN: 1314-3395 (on-line version)url: http://www.acadpubl.eu/hub/Special Issue http://www.acadpubl.eu/hub/

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1 Introduction

Now a day with advanced manufacturing process though the geome-try of a ball bearing has been perfect, it will still produce vibrationson nanometer scale. Vibration is define as the response of a systemto an internal or external impulse causing it to oscillate or pulsate.It is common consideration that vibration causes failure in the ma-chines and structures, it does not. Instead, due to dynamic stressthe damage has been occurred which causes failure in the mate-rial, and the dynamic stresses have been induced by the vibrationproduced. In healthy bearing the vibrations are caused due to therotation of a finite number of loaded rolling element contacts be-tween the balls with the guiding rings. These contacts are elasticin nature, so the bearing stiffness explicitly dependent on time. Ingeneral, the bearing stiffness changes with respect to time a timevarying stiffness causes vibrations, even in the absence of externalloads. Since the stiffness can be regarded as a system parameter,the variable stiffness leads to a so called parametric excitation. Itis one of the major sources of vibration in ball bearings. Apartfrom this the savior vibrations occurred due to local or distributeddefects. Which can be prevented by condition monitoring or pre-dictive maintenance or condition based maintenance. The doctorcan diagnosis the diseases or health of human being by observingthe pulses of hand similarly engineer can diagnosis the defects orhealth of machine by observing the pulses or vibration signature andcarried out the productive maintenance with the help of FFT an-alyzer or IRD Mechanalyser. Vibration analysis has being appliedon operating machines to identify the health condition, to identifydefects and inaccuracies and to schedule an optimum maintenanceon individual machines. The basis of this study is the measurementand analysis of vibration characteristics at specified locations on amachine. In vibration analysis, it is possible to predict differentdefects produced by the vibrations of different characteristics andwould tell the details of defects and inaccuracies so that it could beminimized, which leads to increase the plant efficiency.StandardsISO 10816- VIBRATION STANDARDS Velocity measurements canbe categorized as follows:

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VIBRATION SEVERITY CHART AS PER ISO 10816 (Old IS2372). Abbreviations used are as follows. G-Good, S- Satisfactory,J S- Just Satisfactory, U S- Unsatisfactory

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Historical Review

In order to gain some perception on modern maintenance pro-grams, we will look at the history of maintenance practices a littlemore closely. The earliest type of maintenance was run to fail-ure (Break down) maintenance, where the machine was run untila fault caused it to fail in service. This is noticeably an expensiveapproach, with the major part of the cost being the unpredictabil-ity of the machine condition. It is surprising to learn how much ofpresent-day maintenance activity is of this type. Eventually, main-tenance people hit on the idea of periodic preventive maintenance,where machines are disassembled and overhauled on regular sched-ules. The theory is that if machines are overhauled before theirexpected service life is exceeded, they will not break down in ser-vice. Preventive maintenance has been around for a long time, butbecame much more well-known in the early 1980s, as we will see.In the last ten years, predictive maintenance has become popular,where the machine is repaired only when it is known to have afault. Smoothly running machines are not interfered with, on thetheory that you shouldn’t ”fix it if it isn’t broke”. It is conditionbased maintenance. The most recent innovation in maintenance iscalled pro-active, and it includes a technique called ”root cause fail-ure analysis”, in which the primary cause of the machine failure issought and corrected. The machinery health condition monitoringis being accepted as an effective method to assess the requirementsof maintenance and to increase the operating life of installed plantand machines. Many parameters can be monitored for an effec-tive health condition monitoring but the selection of a particularparameter depends on the type of machine and on economic con-siderations.

2 Literature Review

The Condition Monitoring for Inner Raceway Fault of InductionMotor Ball Bearings have discussed by [1]. A test setup has beendeveloped with a fault on inner raceway of the ball bearing. Thevibration signal is analyzed with assuming contact angle equal tozero degrees and motor operating without a load. A logarithmic

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plot of the vibration spectrum with healthy bearing and damagedbearing condition were compared. They concluded that the spectralanalysis shows the characteristic vibration frequencies. Monitoringof these frequencies fault on a bearing of the induction motor canbe detected. the vibration analysis of a ball bearing have presentedby [2]. They have done experimental analysis and stimulation of4 different bearings which are healthy bearings, Inner Race fault,Outer Race faults and bearings with cage defect. Their study tellsus that the data collection shows that FFT of intrinsic mode func-tions in Hilbert-Huang transform is a useful tool in finding out allpossible root causes and predict root causes based on the system-atic study. Also bearing failure is the High Severity Field Concerncausing failure of the whole machine affects the production rateas well as the Safety of the operator. The data was analyzed byusing FFT analyzer. Input signals of FFT were given to MATLABand simulate the data, and concluded that Amplitude at BPFO ishigher than BPFI and BSF and Amplitude at BPFI is less thanBPFO and BSF. Fault Detection in Bearing Using Envelope Anal-ysis has been presented by [3]. A variety of artificially fault inducedin ball-bearing type SKF 6002-2Z was used. The type of fault in-cluded a defective outer-race, a defective inner race, and a defectiveball. Although motor was set to rotate at 25 Hz, the actual rotatingspeed of faulty bearing monitored by the tachometer was found tobe 2.05Hz. They discussed a method for fault detection of a ballbearing was based on a newly developed technique for obtaining thesignal with the piezoelectric element. The work was also done withan accelerometer. The original vibration signal from piezoelectricelement was obtained and characteristic frequency of different faultwas found out by formulas. By correlating the fault frequency withthe characteristic frequency they were able to find fault in bearing.Vibration analysis of deep groove ball bearing with outer race de-fect using ABAQUS has been discussed by [4]. Their main focuswas about the effect of outer race defect of deep groove ball bear-ings for (SKF 6004) through experimental and numerical methods.Three-dimensional finite element model of the housing and outerrace is simulated using ABAQUS/CAE. An angular position of thelocal defect on the outer race changes from 0 to 315 with angularintervals 45 was investigated through the dynamic finite elementmodel. Experimental results were obtained using bearing test rig

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to validate the simulated results. They modified the design of thefinite element model and concluded that:• The defects located at the radial load distribution area have moreeffect than the defects located at the unloaded area.• According to the RMS parameter for all time responses, the in-crease in the ratio between the time domain parameters of the de-fected and healthy bearings is due to the increase of the clearancevalue.Condition Monitoring of Ball Bearing Using Vibration Analysis andFeature Extraction have presented by author [5]. The vibrationanalysis of ball bearing was carried out at no load, 1kg, 2kg, and4kg at 1475 rpm. Based on the experiment carried out on vibra-tion monitoring of bearings, it was concluded that FFT spectrumindicates the location of the fault. Additionally, they also men-tioned RMS, Skewness, Variance, Mean, standard deviation, fewof the statistical parameters were evaluated for above conditions ofbearing. From the plots of extracted features against Load, it wasclear that these features have potential to identify the defects inthe bearing as the plots of healthy bearing and defective bearingare not overlapped. The numerical bearing model to investigate thevibrations of the ball bearing during run-up has been developed byauthor [6]. The numerical bearing model was developed with theassumptions that the inner race has only 2 DOF and that the outerrace is deformable in the radial direction, and is modelled with finiteelements. They have considered centrifugal load effect and the ra-dial clearance effect. The contact force for the balls is described bya nonlinear Hertzian contact deformation. They have consideredouter race, inner race and ball defects into account. They usedthe continuous wavelet transform (CWT) and envelope analysis toidentify simulated bearing faults. The continuous wavelet trans-form (CWT) found better for vibration analysis of a bearing withball fault. Fault diagnosis of a rotor-bearing system using responsesurface method has been discussed by author [6]. They have con-sidered the distributed defects such as internal radial clearance andsurface waviness of the bearing components. They have studied ballwaviness, inner race waviness, and outer race waviness individuallyand also taken readings of combined waviness. They investigate anaccurate performance prediction, which is essential to the design ofthe high performance rotor-bearing system. They used mathemat-

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ical formulation the contacts between the rolling elements and theraces are considered as nonlinear springs, whose stiffnesses are ob-tained by using Hertzian elastic contact deformation theory. Fromthe obtained responses following conclusions are drawn:• Nonlinear dynamic responses are found to be associated with largeinternal radial clearance and distributed defects.• It is shown that the system exhibit dynamic behaviors that areextremely sensitive to small variations of the system parameters,such as internal radial clearance and ball waviness.• The system shows periodic nature when ball waviness is at itsmaximum level.

3 Roller Bearing

The bearing is a mechanical component permitting rotation of onepart relative to another by reducing friction. It has three mainfunctions:• -Forces transmission• -Rotation with minimum friction• -The position of a shaft with respect to the housingThus, if we describe a ball, we find rolling elements, separated atequidistance by a cage, an inner ring and an outer ring providedwith raceways (Figure 1). The ball bearing may replace the slidingfriction by rolling one. However, various body contacting (innerraceway and balls or outer raceways and ball) showing differencesspeed in their contact areas that will generate local slipping. In-deed, the friction generated by the fastest surface will tend to pullthe slow surface.

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Bearings are an essential component in almost all machinery. Theirmain functions are to provide location and support for the movingparts while ensuring the minimum of friction under all conditions ofload and speed. The main component of ball bearing is as shown inFig.1 Outer Ring: The outer ring is situated on the housing of themachine and is stationary. It is the connection between inner pe-ripheral and the outer peripheral. Cage: This component keeps theballs separated and equally spaced and acts support to the balls.Inner Ring: The Inner Ring is the smaller of the two bearing rings.The inner ring has a groove on its outer diameter to form a pathwayfor the balls. The surface of outside diameter path is finished to ex-tremely tight tolerances and is honed to a very smooth. The innerring is mounted on the shaft and it is the rotating element. Ball:Balls of a bearing are the rolling elements that separate the innerring and outer ring and permit the bearing to rotate with minimalfriction. The radius of the ball is made slightly smaller than thegrooved ball track on the inner and outer rings. This makes theballs to contact the rings at a single point.

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To ensure a long life, the roll bearings are lubricated with greaseor oil. According to their operating conditions (load, speed etc.),different regimes of lubrication can be occurs:- A system of elasto-hydrodynamic lubrication (EHL).

3.1 The E.H.L Contacts in Bearing

A ball bearing can force the position of shaft relative to system. Therolling elements transmit the forces applied by the shaft to the innerrace and then to the outer ring which is fixed to the housing. Theymake easy also the rotation of shaft relative to housing (Figure 2).Geometry of rolling elements and raceways (inner and outer ring)differs depending on the loading conditions (axial and / or radialdirection moments) and speed. Angular contacts ball bearings aredesigned to collect radial and axial loads simultaneously (Figure3). They can operate at very high speed, moderate and low speed.Due to the own weight of the shaft and the unbalance effects theaxial component of the thrust and the radial component generatedis engagement in the case of the use of a speed reducer.

4 Methodology

On individual machines critical measurement locations have beenidentified and important vibration characteristics have been mea-sured at different locations in horizontal (H), vertical (V) and axial(A) directions. There has many inaccuracies or distributed defects

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in a machine such as geometrical imperfection, unbalance of ro-tating machines, misalignment, intrusion of foreign particles, bear-ing problems, mechanical friction, waviness, excitation, resonancesinto machine structure, etc., which can produce vibration into thesystem. Many machines may have one or more problems simulta-neously and thereby make the analysis a complex one. Based onthe initial measurements, the machines health condition may beclassified. Machines indicating unsatisfactory behavior should beattended to improve the health condition. Once the base line dataor alarm value has been established, regular vibration studies atspecified intervals of time can help in monitoring the deterioration.

5 Experiential Setup

The vibration signal was collected by IRD Mechanalyser and ana-lyzed in software. The accelerometer probe has been mounted onbearing housing with the help of a magnet, and the measurementsare taken in Horizontal, Vertical and Axial directions. The mea-surements have been taken in the Drive End (DE) side and NonDrive End (NDE) side in running condition of 250 RPM.

Table 1. Equipment Specification and machine drawing

Vibration measurement of Healthy bearing

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Table 2. Vibration Measurements DATE:- 19.01.2018

The Roll NDE bearing is exhibiting normal vibration trend withmaximum overall amplitudes of 0.5 mm/sec RMS Velocity, but theroll DE bearing is exhibiting very high vibration measurements of1.3mm/sec RMS velocity. As per the ISO standards, the obtainedmeasurements are high and when spectrum analysis is performedit is found that there are Harmonics of ”Inner race bearing defect”frequencies with side bands of the roll rotational frequency. Thevibration signals corresponding to the defective bearing with thedefect on the bearing are shown in Fig.2.

Analysis:The peak at 4.16Hz is the shaft rotating frequency, also called asthe fundamental frequency. The peak at 8.32 is 2*fundamental fre-quency harmonic and similarly, 12.48 is 3X harmonic,16.64 is 4Xharmonic,20.80 is 5X harmonic and 24.96 is the 6X of the funda-mental frequency. Due to the presence of fundamental frequency

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harmonics along with side bands, it indicates ”Inner Race Defect”.From the spectrum analysis, it is conformed to be inner race defect.

6 Results and Discussion

It is clear from the spectrum analysis that it possess inner racedefect, as bearing housing was opened and observed, there is aninner ring crack as shown in (Fig.3).

Figure 3. Inner Ring Defect

After successful detection of the defect, the bearing is replaced andfurther monitored. After Replacement (Table 3) contains the vi-bration measurements and (Fig.4) is the spectrum of the replacedbearing.After Correction:

Table 3. Fig.

Figure 3. Inner Ring Defect

The Roll NDE DE bearings are exhibiting normal vibration trendwith maximum overall amplitudes of 0.3mm/sec 0.5mm/sec RMSVelocity respectively.

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Table 3. Fig.

Figure 4. Spectrum of New Bearing and Defective Bearing

7 Conclusion

This research work presents a method for detection of ball bear-ing fault on the inner ring of a bearing by vibration analysis. Anexperimental study has been conducted in running condition withfaulty bearings, measuring vibrations. The spectral analysis showsthe characteristic vibration frequencies of inner race defect of abearing. Spectral and vibration comparison of the bearing is madebefore and after replacement.

References

[1] Ravindra A. Tarle, Nilesh K. Kharate, Shyam P. Mogal, Vibra-tion Analysis of Ball Bearing, International Journal of Scienceand Research (IJSR)

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[2] Amit Shrivastava and Dr.Sulochana Wadhwani, ConditionMonitoring for Inner Raceway Fault of Induction Motor BallBearings, International Journal of Electrical Engineering. ISSN0974-2158 Volume 5, Number 3 (2012), pp. 239-244

[3] Dr.AsheshTiwari and Ravi Jatola, Fault Detection in Bear-ing Using Envelope Analysis, INDIAN JOURNAL OF RE-SEARCH, Volume: 3 Issue: 5 June 2013

[4] A Nabhan, M Nouby, AM Sami and MO Mousa, Vibrationanalysis of deep groove ball bearing with outer race defectusing ABAQUS, Journal of Low-Frequency Noise, Vibration,and Active Control 2016, Vol. 35(4) 312325

[5] S. V. Shelke , A. G. Thakur, Y. S. Pathare, Condition Mon-itoring of Ball Bearing Using Vibration Analysis and FeatureExtraction, International Research Journal of Engineering andTechnology (IRJET) , Volume: 03 Issue: 02 — Feb-2016

[6] M. Tadina and M. Boltezar Improved model of a ball bearingfor the simulation of vibration signals due to faults during run-up. Journal of Sound and Vibration (2011), Volume: 300, Issue17, Pages 4287-4301

[7] Md. Abdul Saleem, G. Diwakar, Dr. M.R.S. Satyanarayana,Detection of Unbalance in Rotating Machines Using Shaft De-flection Measurement during Its Operation,IOSR Journal ofMechanical and Civil Engineering (IOSR-JMCE) ISSN: 2278-1684 Volume 3, Issue 3 (Sep-Oct. 2012), PP 08-20

[8] H. Saruhan, S. Sardemir, A. iek, and . Uygur, Vibration Anal-ysis of Rolling Element Bearings Defects, Journal of AppliedResearch and Technology,Vol. 12, June 2013

[9] Pratesh Jayaswal, A.K.Wadhwani, and K.B.Mulchandani, Ma-chine Fault Signature Analysis, Hindawi Publishing Corpora-tion International Journal of Rotating Machinery, 2008, ArticleID 583982.

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condition monitoring of deep groove ball bearings · importance because of its advantages over...

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