ieeiatim swt displacement and vibration … shaft displacement and... · tando tnnda awal kerosakan...

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IEEIATIm S WT DISPLACEMENT AND VIBRATION MEASUREMENTS FOR THE EARLY FAULT DETECTION IN ROLLING ELEMENT BEARINGS LEO SING LIM A thesis submitted in fulfilment of the requirements for the degree of Master of Engineering Faculty of Engineering UNIVERSITI MALAYSIA SARAWAK 2004

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Page 1: IEEIATIm SWT DISPLACEMENT AND VIBRATION … shaft displacement and... · tando tnnda awal kerosakan galas bedah dibual pada bahagian larian kuar dm larian dalfim untuk 8;rwlas bebola

IEEIATIm S W T DISPLACEMENT AND VIBRATION MEASUREMENTS FOR THE EARLY FAULT DETECTION IN

ROLLING ELEMENT BEARINGS

LEO SING LIM

A thesis submitted in fulfilment of the requirements for the degree of

Master of Engineering

Faculty of Engineering UNIVERSITI MALAYSIA SARAWAK

2004

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'Phis thesis research project could not be completed without the assistance and support of

several indivitluals to whom the author wish to express his deepest ~adi*iudc. First of

all, the author wishes to take this opportrraity to sincerely thank his supervisor, Dr. IXa

Now lJng li~r his kind supervision, guidance and motivation given to see through Ihc

success of' this projc?cd.

Apart Gom t l~at : the author also wishes do thank all mecha~~ical lab assistants for

providing full assistance in ensuring the completion of his laboratory works. A sign of

gr;ztitudc is also Ibrjvarded to the Ministry of Science, Technology and the Environment

for their financial support awarded &rough the National Science Fellowship (NSF). Last

11uC not least, the author would also like to note the motivation and support given by his

fric?ads throughout this research project.

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Abstract

liloXl kmg eelerneat bearings are among the most counarxaon elements wsc?d in i,hc? operation of'

rolalirmg; anracklines. They are, however, one of the weak points inx these. machines whcrtr u

large nraa,jority trf problems associated are caused by bearings failures. As a result,

condition monituraing of the rc~Bling element bearings is important in ordor to kc?ep these

mai:bineries in their proper op~erating condition. Analysis and mainl,err;ance rd'any rolling

c:lc:nnc?rnl, bearings fail-r;rres are made wn~rch easier if any fault can be idex~tified during its

early stage. Thus, it is the aim of" this research to investigate thcr rt?llativc sk~afl,

disp1an:cmcnt and bearing housing vibratio,n nzeasuremcrats for t,hc? early ihtaX~, de~r?el,ion

in rolling a:lcment bearings. Experiments were ~:onductetl on a robor ki t that clobely

sim.rnla6es the actual behaviorxr of rotating machines. In ordc?r to sirnmlal,e the? early signs

of' fault, elcvelloping, a single localized fault was inrduced on thc? oul,cr racc? and tire iurnc:r

race 18br kjtu8il beam-ings and roller k~earings, as well as on a rolling c>Xemr?n.l of ;a roller

lacasing. Bra lhis rcsearclu, vibrations caused by the good and faulty bearing for both

r:ategorics o f kpearings were analysed, ExperimentaX data from the relative shaft

displaccmernt aneasnrerments due to dyrramic vibrations of the shaft were analyscd using

time waveforxn analysis to detect the suiitlen changes in amplitude as a fixncticm sf tinrt?.

Thc bt?aring ilbarusia~g vibration signals captured were analysed with c:nvelape analysis to

detccl Ibt: re~~c?Citive iia~pulse signals caused by the bearing fault in fsequcrrcy dornixin.

ITronn /,hc exlaerirnc?ntal results, it was found that both techniqlxc?~ car1 successfr.irlly

indicatr? the rollirrg elennent bearings condition and can also &)e used to iderrtify

partlc~~llar allnmagcd component of a bearing. The experimental results also showed that

both auonilorilrg teellniques conrlplinlerlt each other.

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Gallxs ~ l e r r ~ ~ n hergulca~g nzeyr~~pakan ko/?xporzeiz yare,: palir~g biasa d t g ~ ~ n a k a n d i dalam

o~~erus t sese8jua;de mesial putasan. la merupahan sakah satu tstik Kelenzahan bargt mesin

t~rsehul herana kebanycrkan masalah yang fimbul cxdalah dtsehakihan oleh kegagalcar~

galas. OJeh sebab ttu, penguwasan Keodaaan terhadap galas eleme1-s bergulirtg adrwbaJ~

pentia~~; unlulz mernastikan mesin-mesin _ ~ a n g d1,gunahan senliasa herada dalam

izocadaatn yan,g ma~muashan. An akisis dan pen,yelenggaraan sebaralxg masa lah kega4;alaxz.

galas plemen be)-guling mer~jads lebih mudah sehtraxzyca kemswkan awal pada galas

daj~ab drkesan dan dikerealpasti. "FuJ7uan penyekidikan ini iaCah vhc.nyiasa$ tehnih

pc2r1,gukuran anjakwre relati[ awci dan juga tehr~jlk per~gukuran getarale perumwh galos

uaatuk mpngesan sebarang herosakan awai pada galas ekemen berga~lir~g. Jthspertrnen-

eks~)er~,men telajz dQalankan deaagare menggunahan sebuah rotcsr kit yang b~rupaya

aas,en,stmulr~si periiaku s e b ~ n a r sebwaiz mesin berputar. Sa tu hesosakari yar~g meaj.3rerui1ai

tando tnnda awal kerosakan galas bedah dibual pada bahagian larian kuar d m larian

dalfim untuk 8;rwlas bebola dare pengguling, Selain iku, satu kerosakan .jugs dib~sat pada

elemen ped~ggull~zg unduk galas pengguling. ISalam peqyelidikan mi, gelaran yang

dihastlhmn taleh Jzedua-dua .Jen&s galas dalam kemdaar~ baik d a n rosak telah drsanalists,

Data yartAr dipprolehi dnrtpada pengukuran ar~jakan relullif aei yang berdasarkcrn

gelaran d i n a m ~ k pcada aei te2ah dianaltsis dengan mereggunakan analisis bent~lk

g~lomhang maser untuh mengewun sehamng perubahan amplitud seeara meaadadak

ine2au~aj.n. tnasa. Ss.yarat getaran yang dipprolehi dar~pada perurnail galas teSah dislnaltscs

d ( ~ n g a i ~ m~r-~ggunakan anakisis sampul untuh mengesan seharang ssyarat dedc~r~~yut

b~ru lang yang dihasilkan oEeh kerosahan pada gaka.3 di dala~re domazn fiekuensc.

Dartl~aida ke~~uttxscuuz eks~>esimen, dtdapatr bahawcr kedua-dun tekntfi tersebut bt~rupayar,

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rnengesan Zderosakan pada galas elemen berguling dan juga berjaya mengenalpasti

kornponen galas ,yang telah mengalami kerosakan. Selain itu, kedua-dun teknik

pengawasa rnenunjukkan keputusan eksperimen yang sepadan di antara satu sama

lain.

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TABLE OF CONTENTS

Acknowledgc?ment

Abstract

Abstsak

Table of Contents

List, of Figures

List of 'Tables

TEIt 1: INTRODUCTION

I. 1 Background

6.2 (bb%jeetives of the Research

1.3 Thesis Organization

TER 2: LITEEtATURE REVIEW

2.1 Maintenance Methods

2.2 Types of Bearings

2.2.1 Fluid film bearings

2.2.2 Rolling element bearings

2.3 Types of' Faults in Rolling Element Bearings and Their Causes

2.4 Rolling Element Bearings Frequencies

2.5 Techniques of Fault Detection in Rolling Element Bearings

PAGE

ii

iii

iv

vi

X

xiii

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2,6 Vibration Analysis in Rolling Element It3earixags

2.6, I 1Tistor.y of I";luXt detection usirrg vibration analysis

2.6.2 Vabration measureulend syste~ras

2.6.3 Gauschs of vibrations

2.6.4 '1"ypes of vibration transducers and rneasurcments

2-6.5 Vittration sigrral srnaly sis

2.6.6 NJethods of vibration rnasalitoring

2.7 Surmmary

C:EiAll)llII:TC 3; METEXLODOLCIGY EWERIMENrTAL SETUP

3-1 Yrttisiudracliorl

;%.2 IPro~ac3rtics of the Test Bearinlgs

3.3 XJe\rellopment or tkac Components

1 Shaft

3.3.2 XSearing housing

3.4 Fe:xpc*rixncntal Setup for Relative Sl.raR 1)isplacement Measurement

3.4.31 'Yest rig setup

3,4 -2 AI3RE@ for WindowsTM soRware

3.4.3 208-1) Data Acquisition Interhce ZJnlt

3.5 Rxperirnental Setup for Bearing I-lousing Vibration Mcasurernent

3.5.1 Test rig setup

3.5.2 SENrI"INEBl'rM Machine M[~nitoa.ing Software

35.3 Ilatts Collector System - 2526 Series

t3.6i 8 urn rntrry

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GXI'EA1I'?'EI4: 4: EXPERLMEINFfi RESUIJTS OF ELEIAKFIW SWFT

BIXSPPAC:EMERT1' MEASUREMENT

4. I Inlr'odraclion

4.2 OX.?jieetivcs o f the Hxperiments

4.3 F:xporixnoniaX Results and 13isctassions

4 -3.1 Non-tledbctivc loezrnngs

4.3.2 '6"learings vvitln a single outer race fault

4.3.3 Bearings with a single ixnner race fault

4 . 4 Xloller beizring witla. ;I single rolling elernenl f'tmult

4.4 Xrrn~nrrary

CIIAly'rElt 6: EXPERIMENTILL RESUI,TS OF IEEARXNG HCIIJSlN6:

VII3MrIQ)N MEASUREMENT

5.1 Inlroduction

5.2 Ohjcetives of lJrc Experiments

5.3 Bil:xpi?rimenl,al Results and IJiscussions

5.3.1 Non -defc?etivc bearings

5,3.2 Bearixags with a singlc outer. race fatalt

5.3.3 Vjearings with a single inner race fault

5.3.4 Roller bearing with a single rollirlg clement fault

5.4 8ummiary

5.5 Corrc?lal,lrsn Belwii?en Relative ShaR Displacemexll and nearing XSousi ng

Vibration Measureanents

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CHAPTER 6: SUMMARY AND CONCLUSIONS

REFERENCES

APPENDIX

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Ctandition monitoring maintenance

Rolling e1e:ment bearings terminoloa

C utimay view of a single row deelo-g~roove ball bearings

B:uCaway view 01 a double row deep-6;rsoowc? ball ilearing

Cutaway view of an angular contact ball bearing

Clataway view of a cylindrical roller bearing

Cutziway view of a sphert~c;ll roller bearing

(~~;n.tziway view of a tapered roller bearixrg

Iluhiway view o f a needle roller bearing

Cutr"~w;~y view of a thrust, ball bearing

Schematic ciiapam of the rolling clilcmermt bearing gecsmctrg

Important stages in vibration measanrements

Test bearings

Schcrmatic diugrun~ of the sha-li,

Sc:hematic diapana of the bearing housing

"I"cst rig sc?tup for relative shaft displacemerjt measurcunenl

Bevelled faces on the bearing and probe blocks

Schematic diagram of the proximity l)robc?s mounted on prok~o

marount, (a) viewed from the drive anti Cb3 viewed from the left sidc.

Tmt rig setup for bearing housing vibration measurement

The structure of tho Plant Wirrdow and Route Wirrdow

PAGE

5

9

I I

11

12

1 :-b

13

14

15

15

18

25

35

13 8

t38

40

4 2

43

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LIST OF TABLES

TABLE

3.1

3.2

3.3

3.4

Ball and roller bearings dimensions

Calculated bearing frequencies for shaft rotational speed at

2000 rpm

Approximate ratio of bearing frequencies to shaft speed frequency

RK 4 Rotor Kit specifications

PAGE

36

36

37

4 1

... X l l l

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vibratiiora cI.al-nracter(isties of rolling element bearings is imp~ortant for eff~?c:tivc: ;~rr;alysis

(YBl"araciora & (Ihornelhury, 1997). Vibration signals resrmlting from the rolling clcnneat

bearilr~gs Fault present a rich contenhof pllysical information, which can lead to tho clear

itlentificatiorr abor~lt the nature of'thc fault with axa appropriate analysis.

1% Objli?cdivc?s of the Research

'I'tris r.esenre1.s. invc~lves tho investigatiox~ of techniques rrsed fior early tloteetion trf arxy

iroaring hjllts. L3all arnd roller bearings were wsc:d in the analysis of' transducer response?

l o ;a singlo loealiza2d fault on the outer race, inner race and a roljing olcmr?rat,

irespcc:tiva?lly. 'Il%erefore, the main objedives of the? currenl researellr incl ude:

1. "'0 iravcstigale tkre fc?asibility of using relative shaR displacs:meurl, for tbc?

(lctection of" rolling element bearing faults. Displacements or dyrntzrrlie

vnbrations of the shaft are measure directly by using proximiCy probes,

mountc?d elosc to the bearing llnder test.

2. 1'0 investigate the application of bearing housing vibration measnrc?m(?nL

xnet!aod for "LC detec1,ion of ball and roller bearings faarlt. A casing-mtrunli,cd

trarrstlueer is mounted on Cop sf the bearirrg ht~uxsi~rg to pick up casing

vibratiitrrx siigrlals caused by good and hulty bearings.

3, "Yo ovaluato the effectiveness of relative shaft displacelmcnt and be~nring;

krcsusing vibration measurements techniques fbr the deteetatrn and

idcntmficaation trf any rolling elemelrat bearings faull arnd its severi-V,y.

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1-3 Thesis Organization

Tllis thc:sis is organized into six related ch;zpders. Below is the description for ezzeh of tho

ch;iptr?r from chaptc?rs 2 Ca 6.

Chapter 2 irlcludes the literature review about conventiorlal antl rrroderr~

maintenance methods, types of b c a ~ n g s and its properties, as well as teclzniques -ibr

rolling element hearings fault detection. In addition, vibration analysis teehniquci is also

discussed in depth.

C:lsapter 3 covers the methodology and experimental setup in this research

project. IXcre, a rJescription or the experimental approaches for both rela-iivc shaft

dispiaeemon2, ;md bearing housing vibration measurements techniques will be made,

I3oacriplion for the hardware and software used arc also includt:d.

Chapter 4 lbcuses on the experiments conducted to investigate the reladive shaft

displaccncnt measurement tecl-znique. Resides, analysis of the results ant1 discussions

arc matlo fur each of Ihc? experiment.

CllapGer 5 presents the results obtaincd from the experiments conducted under

hearing housing vibration measurement technique. The results are analysed antl

discussions ihr each ofthe experiment are included.

Final conclusions of this research are present in the last chapter, In additior~,

suggcst,ior.rs for future research arc also offered.

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LJl"l'E1WFmE REVIEW

2.1 Mainterranccl? Mothods

'T'raditiornal machinery maintenance prae4,ice in industry can broadly bn cadeg;orihsc?d ixn

two mrelkaods; they are, run to fail~rre and preventive maintena~rce (lF$riic?l & l(j;jor, 1989).

l n r-t~nm to Fdi I txrc ~.an;iia ten;mce prac tised, machir~ery would not be mrrirntained until i4,

broke down. This is the simplest approach to maintmamce and the systc?m rcsyrrirtrd .120

ilmpXomcnt could be extremely simple, Run to fadure can also X>e eonsida?reri as tho

dohull main tcrxanee action, since the possibility of an urxexpeeted failure will always

c?xis.l,. qM"Fnt? tlrawloacks of this approach depencll on the consequencr? of fzilurc? and

urtc?xpc>ctod failaures are disruptive B,o existing ae1,ivities. This practiet? may halt

~~rorJrrctinn ant3 result in the loss of h ~mdreds or tho-rrsarrds of dolars. On the othcr tlimnd,

pre?verak,ivc? rwnaixrtenanet? is an organizr:d activity designed to lnrevcnt tho sutddc?xl hilrrre

of oqr r ipurnea.111 components anaor syslern, where id requires the scheduled inspection

and/or raplacement of parts a t pre-determinc?d intervals. This maintenance helps to

prol,ecI, assc!ts alrrd proloxrg the usehl lift? of producticln equipment. The dif'fieul ty wit11

this ancftXrrori lies in the fad that ofien the components in grrod working condit,ic~n arc?

rc>lrlae(:d, wl~iWt3 ira many occasions damage is done during the process of rebuilding.

"'he idoal miaintenance st rate^ is that machines are c~nlg stoppc?d if3lheir

coxnd ition dernands it. Therelbre, condition monitoring as illustraterl in ;tiqigura 2. I , has

since spread rapidly thrclu& most industries cmployjng rot,atirrg machinery. Contiitio~x

rnonid,orinl~ ranc?ans keeping careful watch of' machinery and to detect the onst?C o f claangcs

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in operating conditions that carr signal a breakdom. Upon dcteef,non of" such conditions,

ttle rnairatcaaancc? pmfessional can take appropriate actions to address the problcnn and

evela determine a Lime framc? within which maintenance must be carried out f,tr avoid awry

disruption to production. In this kind of maintenarrce stratt:gy, cornponexai,~ arc only

replaced when they are as close to the end of their uselirl life as possible (Rtrsaler, 1998).

Ii~?ec?rttBy, new tc:chncllo~"y in electronics axld computer Lechnolo~y enables nlaintenanco

professionals to gather and process extensive amalumts of data, and f,o xnclrc? accurately

dr:t~:n nine macbirao condition. Rarkov and A~ovtsev (1995) rncntioned {,hat, tht? ncw

gc~~eratir~ra of condition monitoring system can reliably detect not, only Lha, if,otcm.rliailly

ilangcroers faults a t Ihc initial stage of thcir developmenl,, but also identify tho cxdct type

(sf ' fa11 P 1 unad its severity.

E'igrare 2-1: (Zonditlon monitoring maintenance (Brcel& Kjaer, 1989)

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In fact, condition monitoring can provide several advantages over other

maintenance strategies (Barron, 1996). These advantages are:

Improved availability of equipment

Improvement in equipment availability can occur for several reasons. Firstly,

condition monitoring can reduce the amount of planned maintenance, since

maintenance is done only when needed. Secondly, if the total number of

unscheduled failures is reduced, there will be a corresponding reduction in

the overall time that a machine is unavailable while defects are being

repaired. Finally, condition monitoring can reduce the possibility of secondary

damage by predicting the onset of the failure, which mean that the average

repair time of an unexpected failure should also be less.

Reduced breakdown costs

As condition monitoring has the ability to predict many in-service failures,

this in turn can reduce the numbers of spares kept in stock because spares

need only be purchased when it is required. In addition, by reducing the

number of breakdowns, the staffing levels needed to cope with unexpected

breakdowns may also be lower.

Improved reliability and safety

Reliability can be improved by reducing the number of faults introduced

during scheduled maintenance. This improvement is based on the premise

that a significant number of faults develop during the early stages of a

component's life and mistakes that can lead to failures may be initiated

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during any rework. By using the predictive nature of condition monitoring, it

is possible to remove or to replace a piece of equipment before serious

consequence arises.

Generally, large majorities of problems in rotating machines are caused by faulty

bearings (Neale, 1995). It is very important for the maintenance professional to

understand the bearing characteristics before any corrective actions can be taken.

Ilence, the following section discusses the types of bearings and its characteristics.

2.2 Types of Bearings

The basic purpose of a bearing is to provide a near frictionless environment to support

and guide a rotating shaft. In principle, bearings can fit into two main categories:

namely, fluid film bearings and rolling element bearings (Rothbard, 1996).

2.2.1 Fluid film hearings

Thcse bearings are the most widely used plain bearing. They rely on lubricant viscosity

to separate the bearing surfaces. The rotating shaft drags the lubricant around fbrrning

a supporting wedge and that is why these bearings usually need a lubrication system.

'J'hc continuous lubrication acts to cool the bearing, which allow fluid film bearings to

support high shaft speeds and heavy loads. Fluid film bearings are used in some

applications, such as in small electric motors, steam turbines for electric power

generation, automobile and aircraft piston engines. By properly designed and lubricated,

these bearings are very reliable and offer lives measured in decades for some

applications.

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According to Jc?ffrey (19911, fluid IXlm bearings may bc: classified by t1-1: 1 1 rl,ii:rle c,r:I

function; they are, journal bearings and thrust hearings. Journal bearing is

1,i:aring in whicls two surface moves relative to each other without the benefil, :t.i Irr I I I I ~ ;

elt?rnent. Thus, there is sliding contact. For the case of a bearirlg on the rotalr'i irra; i J 7 , I " I , ,

the portion of lhc rotating shale ad the bearing is called the journal and tho (,?I,- 0 i i s s 1 1 - i y

part that support the load is the bearing. A journal bearing in its simplest

jrxsl a bushing or a reamed bole in a machine for supporting a rotating s

bearing extends compIetciy around the shaR, it is called as a full journa : I : .x~J~~ I ;

Whereas it is called a partial journal-beanjng if the angle of wrap is less than ""C'iiTcm 'll'~~ 1:'

partial journal bearing may be used when the load always acts in one dir

sirrrplest form of thrust bcaring consists of two opposed washers with some

srxppiying lubricant to the interhcc. Thrust bearings accc~mmotlate the axin

of a rottzting shaft. They arc? usually used in coqjunction with journal bear-inylc* t~ c r r l r,

Iubricated by grease, which leaks from the ends of the journal housings.

2 - 2 2 Rolling element bearings

I'reviomsly, the fluid film bearings were the prevalent style used in rnosi, r n I,.] i,11 I

rnaelrinery. Ilovvever, as metallurgy and machining techniques progressed tJI.1,

elernent hearings giiiaed greater usage. Rolling elcrnent bearings are, at pr, ? : ? r r ~ , , II,I I

most widely used of ail bearing types and first choice for gc?neral applic;itisil,r~ [ i i t i i , ' , ,

1999). 'The advantages of rolling e1eunen"iearings are its ability do support b:ri,h .* , I I ;~II

and axial loads in the same bearing? low starling friction and operating frii,, i y i r , : A ~ ~ * l l

Lower sensitivity Lo Iilibricatlon comp~lred to iluid f"rm bc?arings, Figure 2.2 ilins l1t.i ~,r,rk i, i i ,

common terminology used in descr-ibing rolling element hearings (Av,n ll~-n,? (L

13aurrreister, 1987).

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* Cages

I:ugc?s also called as separator or retainer. The purposes of' cages arc usetl to

spact? the rolling elenrrcnl,~ from each other. Cages arc? i'nrnishcd in a wide

variety of' materials and construction, such as pressed-stet71 cages, riwetcd or

cli arcllcd. lilearings without cages are referred as firll-complexnenl.

Rollirag elemenlt bearir~gs fall into two main clasuifications, Lhc?*y arc? ball bcarirags

arrd r o i l ~ r . boarings, E3all bearings are classified according to the ring eonligur;btioxls,

such ;IS ~.Bc:(?p groovt?, angular contact, and thrust typos. Rollcrr k~cizrings on GExo other. BlaraaX

are a:fassifietl ;recording to the shape of the rollers, such as cylirrdsieal, nocdlc, taper and

sphcli-ict~l (Moil, 1999). Some of the nnore common rolling c?lement Inr;:arings lor kxjth ball

anrt.4 rollor hcuriings are ilustrtited below and their ch;lracteristit:s an: desc~ibed briefly.

Single row deep-poove ball bearings

Thr?st? bei~ri~ags, as showlm in Figure 2.3, are probably tho no st widely used. A

d ~ p groove? is formeti on each inner and outer rings of a dc?ep grcrtrvo X~all

bearing. These bearings can handle both radial and thrust loads and it

rssualily hunt$ in applications, where the load is relatively small. l a a ball

bt?aring, thr? load is t,ransmit,te?d fionrr the outer race l o the ball and from the

lraaXl 10 the inner race. Since the ball is a sphere, i t only coa4,aets the inner aratl

OU~,E:B" race at a very small point, which helps il spin very smoothly. Eut il also

metnras that there is not very much contact area holding that load, 60 if the

bearlaig is overloadecl the balls can dcfomm or squish, ruining the bc?aring.

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Figure 2.3: G~~taway view af a single row deep-groove? ball ba:;arings (The 'l'orrington (2ornpany)

* Dou'k~Ic? raw deep-poove ball bearings

rls shown in Figure 2.4, double raw deep-groove hall bea-srillgs provide lbr

heavy radial and light thrust loads without increasing tl-~c? oertc?r diameter of'

i,hc ksearin~gs. Adding a seeoxld row of balls increases the radial load carrying

capacity eorrlpared with the single row design becausc more balls siaare tint?

load. '6he greater width of double TOW beaxbing often aalversely affects tho

misaligrl mcnt capability.

Fig~rre 2.4: Cutaway view of a double row deep-gn~ovc Gall bearing (ETctovc?r-NSK Bearing Company)