testing of bearings

TESTING OF BEARING ON SOUND AND VIBRATION QUALITY.

Seminar Report on...

Testing Of Bearings on Sound and Vibration Quality.

A Report By: HIREN R PATEL.

M.G.I.T.E.R. NAVSARI


Guidance By:

CONTENTS

CHAPTER NO. PAGE NO.Chapter 1: Introduction.

1.1: What is Bearing?

1.2: Importance.

1.3: Types.

1.4: Damages and Damage types.

1.5: Factors affecting bearing life.

Chapter 2: History.

2.1: Historical methods of testing.

2.2: Need of innovation.

Chapter 3: Why sound and vibration?

Chapter 4: Method introduction.

4.1: Importance of method.

4.2: Component introduction.

4.3: Mechanical set up.

4.4: Working cycle.

4.5: Interface.

4.5.1: I/O card specifications.

4.5.2: P.C. compatibility.

4.5.3: Front end selection.

4.5.4: Back end selection.

Chapter 5: Future scope.

Chapter 6: Obstacles.



Chapter 7: References.

Record of Tables:-

Sr No

Content Page Number

1TABLE OF INDEX.

-

2 TYPES OF BEARINGS. 8

3 TYPES OF DAMAGES AND REASONS. 10

4 COMPONENT LIST 18

5 CARD DETAILS 24



List of Drawing:-

Fig.No.

Content Page Number

(Fig.–A) BEARING ELEMENT DETAILS 7

(Fig.–B) BEARING SYSTEM 7

(Fig.– C) TYPES OF BEARINGS. 9

(Fig.– D) TYPES OF DAMAGES 10

(Fig.– E) HISTORICAL METHOD 15

(Fig. - F) MECHANICAL SETUP WITH MIC 19

(Fig.– G) TEST RIG (3D VIEW) 20

(Fig.- H) TEST RIG (FRONT VIEW) 21

(Fig.- I) WORKING CYCLE PRESENTATION 22

(Fig.– J) SOUND TEST SETUP 23

(Fig.– K) VIBRATION TEST SETUP 23

(Fig.– L) EXPLODED VIEW OF FRONT END 27



-: ABSTRACT:-

Bearings are valuable.... until they go bad, and then they are worthless.

But the definition of Bad Condition of Bearing is not standardized yet. To quickly

discover what bearings may be salvaged, we offers positive testing machine.

Because “A Bearing Saved is a Bearing Earned”. We tried to compare the

bearings on ideal and defective condition on Sound and Vibration factor. For

Sound we used microphone and for Vibrations we implemented piezoelectric

sensor. Instead of manually comparing we further given the data to computer for

automatic test of bearing. By this we reduced manual errors. By this we can

predict life very near to actual.



-: CHAPTER 1:-

INTRODUCTION

In many industries, ever-increasing demand for high power and high speed

with uninterrupted and reliable operation, accurate prediction and control of the

dynamic behavior (unbalance response, critical speeds and instability) is

increasingly important. The most crucial part of such large turbo machinery is the

machine elements that allow relative motion between the rotating and the

stationary machine elements i.e. “Bearings”.

Bearings are used in variety of devices, including rotating machinery in

the manufacturing industry. Bearing failures account for a large percentage of

breakdowns in such machines and can lead to costly downtime. Bearing failure is

probabilistic in nature. Because of this, maintenance programs based on set

schedules or past performance are not completely effective in preventing failures

during operation. Techniques in condition monitoring have been investigated for

decades with the aim of determining the actual status of the bearings and

replacing them based on that information. We just tried another method for

prediction of bearing condition.

Quality is the term which decides the company image and that depends on

factors such as Machine Downtime, Good Quality Product and many more. As

consideration of competition each and every industry is trying for a good

AUTOMIZATION.



1.1 What Is Bearing?

Bearing is a machine part or device which is mostly used when there is a

fixture or machine needs rigid support or when there are two revolving or rotating

surfaces are there and they are in contact with each other. Bearing helps both the

surface to lower the friction and run system smoothly.

General Bearing System (Roller Bearing):

(Fig. - A)

General Bearing System (Ball Bearing):



(Fig. – B)1.2 Importance:-

Today there are 90% Elements which are using bearings. So it will be a

funny work to list out the applications and justify the importance of bearings.

1.3Types of Bearings:-



Types of Bearings:-



(Fig. - C)1.4 Damages and Damage Types:-

Normal WearOverlay Fatigue



ScoringCorrosion

Dirt Embedment Cap Shift

Distorted Crankcase

Oil Starvation

Accelerated Wear

Hot Short

Dirt on Bearing Back

Wiped

Fretting Fatigue

(Fig. - D)

1.5 Factors Affecting Bearing Life:-Bearings in industrial applications continue to fail because of inadequate

lubrication caused by lubricant loss, contamination, decomposition and break-down. Lip

seals invariably wear out well before the bearing fails, and sealed bearings inherently

foreshorten the life of a bearing to the service life of the contained grease (usually only

about 3,000 to 5,000 hours for most industrial services).Maintenance professionals may


http://engineparts.com/Motorhead/techstuff/bearingfailures.htm


find the following suggestions on how to forestall motor hearing failure obvious, but

some new techniques and technologies are available.

1) Lubricate Bearing at Correct Intervals:-

Despite years of warnings from bearing manufacturers, over lubrication

continues to plague many motor bearings. Too much grease can cause overheating

of the bearings. The lubrication instructions supplied by the motor manufacturer

will specify the quantity and frequency of lubrication. Generally, two-pole motors

should be greased twice a year, four-pole and slower motors only once a year.

2) Use the Best Available Grease:-

The most commonly used bearing grease is polypro-based, low-cost, low-

performance, highly compatible lubricant. However, it does not handle water

well, a serious drawback for many industrial applications. It reacts readily with

water and loses its ability to lubricate bearings. Industrial motor bearings should

be lubricated with synthetic-based aluminum complex grease. High-quality grease

pays for its additional cost in reduced motor downtime and repair costs.

3) Keep out Moisture:-

Unless the motor is being hosed down or it operates in a humid

environment, shielded motor bearings may not become seriously contaminated

with moisture while the motor is running. However, when the rotor is shut down,

moisture and condensation can collect on the surface of the bearing components.

Eventually, this water breaks through the oil and grease barrier, contacts the metal

parts of the bearing, and produces tiny particles of iron oxide. These rust particles

make an excellent grinding compound when mixed with the grease. Resulting in

premature failure of the bearing because of surface degradation. Preventing water

contamination is a major challenge to bearing housing design. Close shaft-to-end

bell clearances cannot stop the movement of humid air. Contact seals will quit

contacting, resulting in large gaps that allow movement of air and water vapor



across the bearing. Vapor-blocking bearing isolators, such as the one illustrated,

are among the more successful devices presently available to prevent water vapor

from entering a stationary bearing. When the motor shaft is rotating, the isolator

opens, eliminating the possibility of friction and wear. However, when the shaft is

stationary, the isolator closes, preventing movement of air or water across its face.

With no wear from rotating friction, the seal may last indefinitely, and surely as

long as the fatigue-failure life of the bearing.

5) Keep out Dirt:-

Lip seals, contact seals, and frequent grease replacement help minimize

the amount of dirt and other air-borne abrasives that can contaminate bearing

lubricant. These solutions, however, have some drawbacks. Lip seals have a short

service life, and frequent grease displacement is expensive and messy. One

successful approach to keeping air-borne dirt and liquids out of an operating

bearing is to install a labyrinth-type non-contact seal over the bearing housing.

These bearing isolators, readily available from suppliers, combine a tortuous

labyrinth path with impingement and centrifugal forces to trap and remove air-

borne dirt and liquid; virtually no contamination can reach the bearing. Because

the bearing isolator is a non-contact device, it will generally be the longest-lasting

component of the motor. Although not intended as such, a bearing isolator could

serve as an emergency sleeve bearing if the primary bearing fails, possibly

preventing damage to the motor’s stator and rotor. In emergency situations, the

bearing isolator can allow continued operation for a short time and still prevent

the need to rewind the motor when the bearing is replaced. Bearing isolators

constructed of bronze or other non-sparking materials also can prevent hazardous

sparks that could otherwise occur when the bearing’s rolling elements fail.

5) Other Suggestions:-

Improved bearing protection and lubrication will reduce downtime and the

maintenance costs of electric motors, but other important motor design features

contribute to long service life, including over-sized high quality bearings, high-tech



winding insulation, superior fan design, high-performance paint (such as epoxy) and a

strong, rigid cast iron frame. These features, usually standard or readily available, are

found in most industrial-grade severe-duty electric motors. High-performance bearing

protection systems. However, are not universally accepted as essential for long motor

life. Specifying permanent bearing protection for new motors, or retrofitting isolators

onto existing equipment, usually requires initiative on the part of the user’s maintenance

or engineering staff. Permanent, absolute bearing protection has a greater effect on motor

life than any other decisions made in specifying, equipping, and caring for electric

motors. Keeping bearings lubricated with the right amount of clean, uncontaminated,

high-quality lubricant allows bearings in most industrial motors to outlast all other motor

components.

-: CHAPTER 2:-

HISTORYYou may want to look at bearing failures as a means of justification. Can

you identify key machines that will shut down production in the event of failure? It

doesn’t have to be a million dollar machine. An 85 Rs. bearing can stop a

production line as quickly as an 85,000 Rs. bearing. However you choose to



validate your intentions to the next level, be sure to make a solid business case and

have everyone onside.

As it is said “A BEARING SAVED IS BEARING EARNED” man tried

a lot of times to predict the life or failure state of bearing.

2.1 Historical Methods of Testing:-

The Reference Bearing (Bearing recommended to be acceptable or of

known life value) is to be hanged vertically, using an elastic rubber

band, to the rigid support

An Instrumented impact hammer is to be used to strike the outer race of

the bearing with four (4) repeated light impacts in an any chosen

direction at any chosen point. The value of the impact signal is to be

taken from the hammer to channel (1) of (at least) Two channel

Vibration Analyzer.

The response signal of the bearing to each hammer blow is taken

through the accelerometer attached (by bees wax) to a point on the

bearing at opposite side of the outer race (opposite to striking point).

This accelerometer is connected to channel (2) of the Vibration

Analyzer.

After averaging of the results of the 4 strikes, the analyzer will show the

Transfer Function of the bearing. This Transfer Function will contain

the Modal parameters for the first mode of vibration that will be

extracted by (BAT) software.

Steps 1-4 above are to be repeated for all bearings to be tested.

BAT software will make the necessary calculations and will produce a

report containing the modal parameters of all tested bearings together

with their expected lives relative to the Reference Bearing.



(Fig. E)

2.2Need of Innovation:- Historically the theoretical estimation of bearing characteristic has

always been a source of error in prediction of the dynamic behavior of bearing system.

Obtaining reliable estimates of the bearing operating conditions (such as static load,

temperature, lubricant etc.) in actual test condition is difficult and leads to inaccuracies.

Consequently, physically meaningful and accurate parameter identification is required in

actual test conditions to reduce the discrepancy between the measurements and

predictions.

-: CHAPTER 3:-

Why Sound and Vibration?



Up to now I think you might have understand, what is bearing, how it

works, how it is essential and so on.

The cause for failure of any machine gives first blame or first doubt on the

bearings. So ultimately the bearings are main factor which serves the quality. The

cause for bearing failure or near to failure can be described on various criteria

such as

Temperature Rise

Sound Rise

Vibration Rise

And Many More...

Any bearing near to failure may be from any reason gives different sound

than the ideal one which ultimately can capture the intention of human. Whenever

there is presence of sound vibrations ultimately take place or vice versa. You can

call it as Resonance of Bearing.

Sound and vibrations are the major and important factors in bearing and

they can be monitored very easily.

We are not checking them with standards but using the comparative theory

on dB calculation.

-: CHAPTER 4:-

Method Introduction:-



Considering the quality, human errors must be eliminated or

implementation of automatic process must be there. We tried the same by doing

atomization in testing process of bearing.

In this method the sound is recorded by microphone and vibrations by

piezoelectric sensor and this data is fed to computer through ADD ON card. And

at computer end or at inspection end there will be comparison and justification of

condition of bearing. Also this test bench can be used in QC of Bearing.

4.1 Importance of Method:-Inspection of mechanical equipment with sound and vibration testing has

many advantages. It provides early warning of bearing failure, lack of or over

lubrication and can be used for slow and high speed lubrication.

Basic inspection methods are extremely simple and require very little

training. In addition it works extremely well with vibration technology. In fact

two technologies complement each other and enhance any PDM (Predictive

Maintained) program.

Mechanical movements produce a wide range of sound. Microphone

(Sensors) detects suitable changes in sound quality.

Sound Observation.8 dB Pre Failure / Low Lubrication.12 db beginning of a Failure mode.16 dB Advanced Failure Condition.30-35 dB Catastrophic Failure.

Note: This Observation is made by NASA for A particular Roller Bearing.These values are not applicable for each type of bearings.

4.2 Component Introduction:-



Sr. No.

Part Purpose Description

1 Motor Drive For Shaft Refer Manual

2 Shaft Mounting For Bearing -

3 Microphone 1/2/3 Sound Input Carbon Type

4 Sensor Vibration Input PZ Type

5 Analog Mux Reduction Of Circuitry. Analog Type

6 Zero Span Span Setting 0-5 V Std.

7 ADC A-D Converter 8Bit SADAC

8 ADD - On Hardware Interface DHI0C51Ref Manual

9 Computer Output /Inspection

which has ISA slot

4.3 Mechanical Setup:-



(Fig. F)

Bearing failures are the number one cause of motor failures (as reported

by EPRI and substantiated by numerous industry studies). The bearing diagnostic

test stand will provide a facility for developing and validating bearing diagnostic

algorithms and for performing bearing life tests that are essential for accurate

bearing lifetime predictions. The test stand will have all the necessary

instrumentation for monitoring all electrical and mechanical variables. Facilities

for extended life-cycle testing and for sensor testing are being incorporated into

the design of this stand.

4.4 Working Cycle:-



(Fig. I)

The above layout gives the brief flow of the working cycle. The total cycle

is controlled by the user end computer. Only the mounting and dismounting of

bearing has to be done manually.

First for the ideal condition of bearing sounds and vibration are tested and

recorded in database. Methods of mounting and dismounting are also mentioned

at there. Then actual working cycle starts for comparative test.



For Sound and Vibration Test Flow chart is as follow:

(A) RPM 1

Motor On – Mic 1 on and Record Noise – Test Vibration



(B) RPM 2




(C) RPM 3




4.5 Interface:-


(Fig. J)

(Fig. K)


It is the word which is used for connection is to be done between computer

and any type of external machine which can cot be directly connected. Although

there are lot of mediators for this interfacing.

4.5.1: I/O Card Specifications

1 Product ID - DHIOC51

2 Name – Digital Input / Output Card for computer

3 Type – Add-On type

4 Mounting – ISA Slot (Main Board)

5 Channels – 24 Channel Input / Output

6 Signal type – Digital (0 – 5 Volts)

7 Logic Level – TTL compatible (0.7 to 4.3)

8 Ports – 3x8 Bit Bi-directional with output latch

9 Max input frequency – 3.12 MHz

10 Source Current – 10 mA max.

11 Sink Current – 13 mA max.

12 Address – Jumper Selected

13 Environment – 16Bit / 32Bit Compatibility

14 Driver – Required only for Visual Basic applications



4.5.2: PC Compatibility

This Add-On direct compatible for 16Bit environment like DOS as well as

the 32 Bit environment like Windows 9x, ME, XP, NT platform and supports all

programming languages Like QBASIC, C, ANSI C, C++, FORTRON, Visual C+

+, Visual BASIC, JAVA.

Out of these programming languages the Visual BASIC Requires the

driver program for accessing the Add-On Because Visual BASIC doesn’t supports

to direct access for Hardware. To overcome this problem one DLL file and one

Visual BASIC module is provided. For further details please Read the Visual

BASIC interfacing test programs and tips in Section 5.4 of manual.

Also driver program provides the friendly sharing of the Add-On hardware

by multiple application programs means multiple programs can use the same Add-On at

the same time without any resource confliction. The user can use maximum eight Add-

On cards of the same type in one computer simultaneously with eight different addresses.



4.5.3:Front End Selection:-

As we seen the compatibility of the card in above topic. It can be used

with QBASIC, C, C++, FORTRON, Visual C++, Visual BASIC, and so on. So it now

becomes important to select the front end. The front end is technical word used in

software manipulation and the user end that means through which user gives commands

or reacts is called as Front End.

Why VB is selected is described in the Followed Table?

Test QB C C++ Fortran VC++

VB6.0

Availability G VG VG G G G

Speed Ok G G O G G

Coding B V V Vast Vast Easy

Environment O O O B G G

GUI B O O B G G

Future Scope B O O B G G

Simplicity In Using

B O O B O G

Cost L L L L H M

Overall Rating B B B B A+ A+

Note: 1) These observations are made by survey of some interface experts. We Just Selected a System

which has an average point and can be easy to handle for any one.



4.5.3:Exploded View of FRONT END:

(Fig. L)

4.5.4: Back End Selection:-It is again dependent on person to person and application to

application. We selected MS-Access.

Because

Good storage capacity.

Easy database creation.

Easy to handle.

Easy available.



-: CHAPTER 5:-

FUTURE SCOPE

On line testing.

Self diagnostic based smart system.

Life cycle calculations.

Determination of causes of failure.

Spectrum analysis.

DSP analysis.

Quality testing of bearings.

-: CHAPTER 6:-

OBSTACLES

Atmospheric condition.

Ambient temperature.

Mounting and dismounting.

-: CHAPTER 7:-

-: REFERENCES:-

www.nesbearings.com/


testing of bearings

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