LING KIONG CHAI

FAULT

CLASSIFICATION IN ROLLING ^{EL. ENIE} T BEARING

USING VIBRATION MONITORING

LING KIONG CHAI

Ti 1071 1366 2001

FACULTY OF ENGINEERING Universiti Malaysia Sarawak

2001

Pusat Mddmat Maklumat AkademWiversiti Malaysia Sarawak

Kota Samarahan UMVERS1T1 MALAYSIA SARAWAK

BORANG PENYERAHAN TESIS

Judul: FAULT CLASSIFICATION IN ROLLING ELEMENT BEARING USING VIBRATION MONITORING

SESI PENGAJIAN: 199ä - 2001 Saya LING KIONG CHAI

mengaku membenarkan tesis ini disimpan di Pusat Khidmat Maklumat Akademik, Univusiti Malaysia Sarawak dengan syarat-syarat kegunaan sepati berikut:

1. Hakmilik kertas projek adalah di bawah nama penulis melainkan penulisan sebagni projek basama dan dibiayai oleh UNIMAS, hakmiliknya adalah kcpunyaan UNIMAS.

2. Naskhah salinan di dalam bcntuk kertas atau mikro hanya boleh dibuat dengan kebcnaran bertulis daripada penulis.

3. Pusat Khidmat Maklumat Akademik, UNIMAS dibenarkan mcmbuat salinan untuk pengajian mereka.

4. Katas projek hanya boleh diterbitkan dengan kebenaran paiulis. Bayaran royahi adalah mengikut kadar yang dipasetujui kelak.

5. * Saya manbaunkan/tid*ýcýemýCan Papustakaan manbuat salinan katas projek an sebagai bahan patukaran di antara instrtusi pengajian tmggi.

6. ** Sila tandakan ( J )

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SULIT (Mengandungi maldumat yang badarjah laeselamatffi atau kepeoutingan Malaysia sepati yang tpmaktub di dalam AKTA RAHSIA RASMI 1972).

TERHAD (Meagandungi makiumat TERHAD yang telah ditentuksn oleh aganisasi/

baden di mana peayelidikaa dijalankan).

TIDAK TERHAD

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Disahkan oleh

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ANGAN PENULIS) (TANDATANG PENYELIA)

Alamat tetap: No. 8F, Lorong Maludan Barat 2A, Jalan Salim, 96000, Sibu, Sarawak

Tarikh: 27 Mac 2001

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Approval Sheet

This project report attached here, entitled "FAULT CLASSIFICATION IN ROLLING ELEMENT BEARING USING VIBRATION MONITORING" prepared and submitted by Ling Kiong Chai as a partial fulfillment of the requirement for the degree of bachelor of Engineering with Honours (Mechanical Engineering and Manufacturing System) is hereby read and approved by:

Date: %ý fo3fz4)O(

(Dr. Ha How Ung) Project Supervisor Faculty of Engineering Universiti Malaysia Sarawak

FAULT CLASSIFICATION IN ROLLING ELEMENT BEARING

USING

VIBRATION MONITORING

P. KNIDMAT MAKLUMAT AKADEMIK UNNAS

0000095192

LING KIONG CHAI

Thesis Submitted to the Faculty of Engineering, Universiti Malaysia Sarawak

As a Partial Fulfillment of the Requirement for the Degree of Bachelor of Engineering with Honours (Mechanical Engineering and Manufacturing System)

2001

ACKNOWLEDGEMENT

Firstly, I would like to express deepest gratitude to my supervisor, Dr. Ha How Ung for volunteering his time, patience and outstanding guiding throughout the project until the aim of this thesis was successfully achieved.

Special thanks to Mr. Banff for his kindness in briefing me on the SENTINEL Type 7107 software and the 2526 Series BrOel & Kjaer Data collector. Not forgotten as well to say thank you to the Lab Technicians, Mr Masri and Mr Rhyier for their technical assistance in this project.

For my parents, warmest appreciation for your love and unwavering support of me throughout my life. For my brothers and sisters, thank you for constant support and encouragement. Special dedicates to my beloved, Cheng See Chiew for her warmest and greatest spiritual support and putting up with my constant harassment.

Lastly, the author wishes that this thesis would contribute towards the expansion and development of all sciences, engineering and technological field both in theoretical and practical.

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ABSTRACT

This thesis entitled, "Fault classification in rolling element bearing using vibration monitoring" mainly focused on the vibration characteristic of different faults introduced intentionally on the rolling element bearings. The rolling element bearing used for this thesis experiment is called "Deep Groove Ball Bearing".

The machine monitoring software and program tool used in this project is called SENTINEL Machine monitoring Software (Type 7107 - Version 4.0) and Brüel &

Kjaer 2526 Series Data Collector System. The vibration monitoring diagnostic technique utilized in this project is called Selective Envelope Detection (SED) will be discussed in this thesis.

Overall in this paper introduction will be presented, followed by literature review, methodology, result, discussion and conclusion. Finally the key source papers are referenced, for those who wish to dig deeper on their own.

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ABSTRAK

Thesis ini yang bery'udul, " Klasifikasi kecacatan pada elemen bebola berputar melalui permonitoran vibrasi" terutamanya difokuskan pada ciri-ciri vibrasi bagi pelbagai kecacatan yang sengaja diperkenalkan di atas elemen bebola berputar. Elemen bebola yang digunakan dalam eksperimen ini dipangil " Deep Groove Ball Bearing".

Permonitoran perisian dan alat program yang digunakan pada thesis ini ialah SENTINEL Machine monitoring Software (Type 7107 - Version 4.0) dan Brüel &

Kjaer 2526 Series Data Collector System. Teknik untuk diagnos permonitoran vibrasi dalam projek ini ialah Selective Envelope Detection (SED) dan akan dibincangkan.

Keseluruhan kertas kerja ini merangkumi pengenalan, kajian ilmiah, langkah-langkah eksperimen, keputusan, perbincangan dan kesimpulan. Akhir sekali, rujukan-rujuakn juga dicatatkan agar membantu sesiapa yang berminat ingin mengkaji lebih lanjut.

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CONTENTS

LETTER OF APPROVAL SHEET OF APPROVAL PROJECT TITLE

ACKNOWLEDGEMENT ABSTRACT

ABSTRAK CONTENTS

LIST OF TABLES LIST OF FIGURES

LIST OF ABBREVIATIONS

CHAPTER 1 INTRODUCTION

1.1 BEARINGS INTRODUCTION 1.2 ROLLING ELEMENT BEARINGS

1.2.1 DESIGN COMPONENTS OF BALL BEARING

1.2.2 BEARING LOADS

1.2.3 BEARING ASSEMBLY AND INSTALLATION

1.3 ROLLING ELEMENT BEARING FAULTS

PAGE

i

11

III

iv viii ix X1

1 1

3 5

7 8

IV

1.3.1 INTRODUCE FAULTS TO BEARING 1.4 FAULT AND CONDITION ANALYSIS

1.4.1 VIBRATION MONITORING TECHNIQUE

1.4.2 ENVELOPE ANALYSIS

1.4.3 VIBRATION ANALYSIS TOOL 1.5 AIM & OBJECTIVE

CHAPTER 2 LITERATURE REVIEW

2.1 BRIEFHISTORY OF VIBRATION ANALYSIS TECHNIQUE

2.2 ROLLING ELEMENT BEARING VIBRATION SOURCE

N

2.3 BEARING FREQUENCY ANALYSIS 2.3.1 BASIC GEOMETRICAL

RELATIONSHIPS

2.3.2 FUNDAMENTAL TRAIN FREQUENCY 2.3.3 INNER RACE DEFECT FREQUENCY 2.3.4 OUTER ARCE DEFECT FREQUENCY 2.3.5 BALL DEFECT FREQUENCY

2.4 COMMON CONDITION MONITORING TECHNIQUES

9 10

11 11 13 14

16

17 18

19 21 21 22 23

24

2.4.1 OVERALL READINGS 24

2.4.2 CREST FACTOR 2.4.3 KURTOSIS

2.4.4 SHOCK PULSE METHOD (SPM) 2.4.5 PECTRUM ANALYSIS

2.4.6 ENVELOPE ANALYSIS 2.4.7 CEPSTRUM ANALYSIS

CHAPTER 3 METHODOLOGY

3.1 METHODOLOGY PREVIEW 3.2 CONDITION MONITORING TOOL

3.2.1 TEST RIG

3.2.2 VIBRATION MONITORING SOFTWARE

3.2.3 DATA COLLECTOR SYSTEM 3.3 EXPERIMENTAL APPARATUS SETUP

3.3.1 BEARING ASSEMBLY 3.3.2 TEST RIG OPERATION 3.3.3 SETTING UP A NEW PLANT

STRUCTURE

3.3.4 ENVELOPE SPECTRUM MEASUREMENT SETUP

3.3.5 DOWNLOADING ROUTES TO THE DATA COLLECTOR

3.3.6 TAKING MEASUREMENT 3.3.7 UNLOADING ROUTES

25 27 27 29 30 35

36 36 37

38 39 42 43 44

45

46

48 49 50

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CHAPTER 4 RESULTS

4.1 EXPERIMENTAL TEST BEARINGS RESULT 4.2 SPECIFICATION OF TEST BEARINGS

4.3 THEORETICAL CALCULATION 4.4 ANALYSIS

CHAPTER 5 DISCUSSION

5.1 BEARING DIAGNOSTICS AND FAILURE RECOGNITION

5.2 FACTORS AFFECTING EXPERIMENTAL RESULTS

CHAPTER 6 CONCLUSION

6.1 CONCLUSION

CHAPTER 7 RECOMMENDATION

7.1 RECOMMENDATION FOR FURTHER WORK

BIBLIOGRAPHY

52 60 60 62

67

72

74

75

76

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LIST OF TABLES

Table Page

Table 1.1 Rolling Element Bearings Defect Frequencies 8

Table 1.2 Frequencies Range of Acceleration, Velocity and

Displacement 11

Table 2.1 The main frequencies of defective bearings' vibration modulation

Table 4.1 Specification of Test Bearings

Table 4.2 Analysis Comparison between Theoretical and Experimental Results

34

60

64

viii

LIST OF FIGURES

Figure

Figure 1.1 Basic Types of Rolling Element Bearings Figure 1.2 Deep Groove Ball Bearing Components Figure 1.3 Radial Play

Figure 1.4 Axial Play and Contact Angle Figure 2.1 Rolling Element Bearing Parameters

Figure 2.2 Trend Analysis of Overall Vibration Signal Figure 2.3 Spiky Nature of Time Series

Figure 2.4 Shock Pulse Method Process

Figure 2.5 Reference Spectrum and Alarm Level Figure 2.6 Envelope Analysis Process

Figure 2.7 Cepstrum Harmonic Series Signature Figure 3.1 The Components of Test Rig Construction

Figure 3.2 Physical View of Brüel & Kjaer 2526 Series Data Collector

Figure 3.3 Envelope Spectrum Measurement Setup Dialogue Figure 3.4 An Equipment Experimental Setup

Figure 4.1 Envelope Spectrum of A Good Rolling Element Bearing

Figure 4.2 Envelope Spectrum of A Rolling Element Bearing With A Worn Outer Race

Page

2 4 5 6 20 25 26 28 30 32 35 38

41 47 51

53

54

ix

Figure 4.3 Envelope Spectrum of A Rolling Element Bearing With A Spall Outer Race

Figure4.4 Envelope Spectrum of A Rolling Element Bearing With A Worn Inner Race

Figure 4.5 Envelope Spectrum of A Rolling Element Bearing With A Spall Inner Race

Figure 4.6 Envelope Spectrum of A Rolling Element Bearing With A Cage Defect

Figure 4.7 Envelope Spectrum of A Rolling Element Bearing With Balls Spall

55

56

57

58

59

mm --- Milimeter

MB --- Mega Byte

n --- Number of Rolling Elements

N --- Shaft Speed

Nb --- Numbers of rolling elements

rd --- Third

RAM --- Random Access Memory RMS --- Root mean square

RPM --- Revolution Per Minute

SAE --- Society of Automobile Engineers SED --- Selective Envelope Detection SPM --- Shock Pulse Method

2x --- 2 times

2X --- 2 multiply rotating frequency

* --- Multiply

X11

CHAPTER 1

INTRODUCTION

1.1 BEARINGS INTRODUCTION

Bearing is frequently used for support and reduction of friction. Generally there are two basic types of bearing which are plain bearing and rolling element bearing. Plain bearings are based on sliding motion between a stationary and a moving member. Rolling element bearings have either balls or rollers that accommodate motion between the stationary and moving parts. Rolling element bearings are frequently called "Anti-friction" bearings although the frictional torque of a full fluid-film plain bearing can be as low as that of a rolling element bearing. However, starting friction in a plain bearing is usually higher than that of a rolling element bearing.

1.2 ROLLING ELEMENT BEARINGS

Rolling element bearings have spread throughout industry as the most widely used element for transmitting force between rotating machine components. All rolling bearing manufacturers make bearings to standardized tolerances set forth by the Anti Friction Bearing Manufacturers Association (AFBMA) and the International Standards Organization (ISO). Rolling element bearings generally consist of two rings known as the

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inner race and outer race with a set of rolling elements running in their tracks. Normally the outer race is located in the bearing housing and the inner race on the shaft. The rolling elements take the form of balls or various types of rollers. Rollers can be cylindrical, spherical or tapered. Figure 1.1 illustrates the basic types of rolling element bearings.

Radial Cylindrical

Spherical

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Figure 1.1 Basic Types of Rolling Element Bearings

Due to the rolling element bearing consists of various types of design, which depend on their effective load carrying function, so this is beyond the scope of the author to test each and every one of the bearings faults. In order to achieve the aim and objective of this

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project, the author had selected the most widely used rolling element bearing called

"Deep Groove Ball Bearing". This bearing is also known as "Single-Row Radial Bearing" due to its design characteristic, mainly to carrying radial load that support loads perpendicular to their axis of rotation. However, its also can accommodate some axial load that support loads parallel to their axis of rotation and accept slightly angular misalignment.

1.2.1 DESIGN COMPONENTS OF BALL BEARING

Deep Groove Ball bearings are, perhaps, the most familiar type of rolling element bearing. The rolling elements are usually enclosed between rings called "races". The diameter of the outer ring is bigger than the inner ring. Typically, the outer race is stationary and the inner race is affixed to a rotating shaft. The balls are held in position by a retainer or cage. The assembly of the components for the deep groove ball bearing is shown in Figure 1.2.

The inner and outer rings are normally made of SAE 52100 steel, hardened to Rockwell

`C' value of 60 to 67. The rolling element raceways are accurately ground in the rings to a very fine finish that is 16 micro inch or less. The balls are made of the same material and ground to a true sphere, and polished to a fine finish. This material has ability carry a wide range of loading and able to carry high unit stresses at the contact surfaces. Besides its hardness and good load-carrying capacity properties, it also has excellent stability,

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wear resistance, fatigue resistance and corrosion resistance properties. [Eugene A. A

&Theodore B 111, 1987].

Figure 1.2 Deep groove ball bearing components

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1.2.2 BEARING LOADS

The rolling element bearing load can be divided into two main groups, which are radial and axial load. Bearings are normally assembled with a slight amount of looseness between balls and raceways. This looseness, referred to as Radial Play, which is the maximum distance that one bearing ring can be displaced with respect to the other in a direction perpendicular to the bearing axis as shown in Figurel. 3.

Figure 1.3 Radial Play

Axial Play, or End Play of a bearing is equal to the total axial displacement of the inner ring with respect to the outer ring, in a direction parallel to the bearing axis, under the effect of a small measuring force. Contact Angle is the angle between a plane

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perpendicular to the bearing axis and the ball to race contact line. The higher the axial play the higher the contact angle and therefore the greater the thrust capacity under axial loads. Figure 1.4 shown the deep groove ball bearing axial play and contact angle.

In applications where axial stiffness is required, bearings should be preloaded to remove radial play. Preload is the condition where internal clearance between elements and both racers become smaller or insufficient. It is normal to preload bearing pairs by pushing the inner races together or by pushing the outer races apart. This results in a contact angle orientation giving maximum stiffness. As axial force or preload is applied, the contact angle increases.

Figure 1.4 Axial Play and Contact Angle

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1.2.3 BEARING ASSEMBLY AND INSTALLATION

Improper assembly or installation of the rolling element bearings can cause machinery faults problems before running under operation. In order for a ball or roller bearing to perform satisfactorily, the fit between the inner ring and the shaft, the fit between the outer ring and the housing must be suitable for a specific application. For example, too loose a fit could result in a corroded or scored bearing bore and shaft, while too tight a fit could result in unnecessarily large mounting and dismounting forces and too great a reduction in internal bearing clearance.

The selection of fit is dependent on the character of the load, the bearing dimensions, the bearing operating temperature, the heat expansion of the shaft and other parts, the design and the required running accuracy. The material and housing wall thickness influence the choice of tolerances for bearing housings. Also, consideration must be given to the fact that the shaft deforms differently when it is solid than when it is hollow.

To facilitate bearing assembly, most bearings are fitted loosely to either the shaft or housing depending on the part that rotates. The part that rotates must have a press fit in order to eliminate wear from differential rolling or "creep. ' Creep occurs when the loose- fitted ring is rotating with respect to the load direction.

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1.3 ROLLING ELEMENT BEARING FAULTS

Rolling element bearings are used in almost every kind of machines and devices with rotating parts. During operation, bearings are subjected to various forms of damages. The forms of faults would occurs either in the elements or both racers could cause the rolling element bearings to fail.

As mentioned earlier anti-friction bearings are constructed using several distinct parts which are the inner race, outer race, cages or retainers, and the balls or rollers. Faults in any of the bearing components will generate specific frequencies dependent upon the bearing geometry and rotating speed. These four distinct parts assist us in detecting bearing defects. [Ron Barron, 19961. The following are the expected bearing defect characteristic frequencies for the respective type of bearing faults as shown in Table 1.1.

BPFO

- Ball Pass Frequency, Outer Race n N d .

( 1 _ cosa 260 D BPFI - Ball Pass Frequency, Inner Race n N d

260 1 + cos a D

BSF - Ball Spin Frequency D N d 2

1_ cost a 2d 60 D

FTF - Fundamental Train Frequency 1 N 1 _ d 2 60 cosa

D

Table 1.1 Rolling Element Bearings Defect Frequencies [Ron Barron, 1996]

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Where:

N = Shaft Speed RPM (or speed range if applicable) n = Number of Rolling Elements

d =Rolling Element Diameter

D = Bearing Pitch Diameter (roller center to roller center) a = Contact Angle

In actual condition bearing elements rotate with combination of sliding and rolling action.

For the above-expected bearing defect characteristic frequency assumption had been made such that rolling element does not slide but only roll over the raceway surface. By calculating the discrete frequencies associated with these four components, we can identify which bearing component is defective. Most of the above bearing problems have characteristics that are readily discernible from the fundamental running speed of the shaft (1xRPM). Typical defects detected in a vibration signature and by analyzing the signature, it is possible to determine whether bearing failure has occurred or not. [Ron Barron, 1996]

1.3.1 INTRODUCING FAULTS TO BEARING

In order to investigate the different vibration characteristic of any faults in rolling element bearing, only one type of fault such as for example spall either on element, outer race or inner race, was introduced to the bearing at any one time. Extra care and attention was taken while introducing any faults on the elements or the both racers in order not to

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