Post on 03-Mar-2015
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.
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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.
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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
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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
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-: 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.
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-: 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.
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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):
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(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:-
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Types of Bearings:-
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(Fig. - C)1.4 Damages and Damage Types:-
Normal WearOverlay Fatigue
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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
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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
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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
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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
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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.
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(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?
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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:-
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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:-
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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:-
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(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:-
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(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.
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For Sound and Vibration Test Flow chart is as follow:
(A) RPM 1
Motor On – Mic 1 on and Record Noise – Test Vibration
Motor On – Mic 2 on and Record Noise – Test Vibration
Motor On – Mic 3 on and Record Noise – Test Vibration
(B) RPM 2
Motor On – Mic 1 on and Record Noise – Test Vibration
Motor On – Mic 2 on and Record Noise – Test Vibration
Motor On – Mic 3 on and Record Noise – Test Vibration
(C) RPM 3
Motor On – Mic 1 on and Record Noise – Test Vibration
Motor On – Mic 2 on and Record Noise – Test Vibration
Motor On – Mic 3 on and Record Noise – Test Vibration
4.5 Interface:-
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(Fig. J)
(Fig. K)
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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
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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.
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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.
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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.
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-: 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/
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