fault diagnostics - report-2

Fault Diagnostics

Report on Fault Diagnostics in Machine Tools using Vibration

With Practical Case Studies

Name Seat #

Mohamed Emad Abdullah 106

Mohamed Emad Mohamed 107

Mohamed Fouad Saber 108

Mohamed Magdy Ahmed 109

Mohamed Mohsen El-Sayed 110

Mohmed Mohamed Elsyaed 111

Mohmamed Mahmoud El-Sayed 112

Mohamed Mahmoud Mohamed 113

Mohamed Mostafa Ahmed 114

Mohamed Mostafa Abd El-Razaq 116

Presented By

Alexandria University

Faculty of Engineering

Production Engineering Department

Third Year

PE363- Theory & Design of M/C Tools -1

Part I – Theory of Vibrations

Fault Diagnostics Page 1

Table of Contents Table of Figures ............................................................................................................................................. 1

Introduction .................................................................................................................................................. 2

Maintenance Engineering ............................................................................................................................. 2

Preventive Maintenance ........................................................................................................................... 2

Predictive Maintenance ............................................................................................................................ 2

Unscheduled Maintenance ....................................................................................................................... 2

Why Make Condition Monitoring ................................................................................................................. 3

Fault Diagnostics ........................................................................................................................................... 3

Using Spectrum in Fault Diagnostics ............................................................................................................. 5

Equipment’s & Instrumentations used in Fault Diagnostics ......................................................................... 6

Measuring instrumentations .................................................................................................................... 6

Vibration Meter PCE-VD 3 ..................................................................................................................... 6

Vibration Meter PCE-S 41: ........................................................................................................................ 7

Vibration Meter PCE-VMS 504 .................................................................................................................. 8

Fluke 810 Vibration Tester .................................................................................................................... 9

Faults ........................................................................................................................................................... 10

Gear wear fault ....................................................................................................................................... 10

Other Faults ............................................................................................................................................ 11

References .................................................................................................................................................. 11

Table of Figures Figure 1- Condition Monitring....................................................................................................................... 3

Figure 2 - What to Measure for a fault ......................................................................................................... 4

Figure 3 Source of Vibration ......................................................................................................................... 4

Figure 4 - Spectrum of a Machine ................................................................................................................. 5

Figure 5 - Measurement References............................................................................................................. 5

Figure 6 - Trending in Vibration Signals ........................................................................................................ 6

Figure 7 - Vibration Meter ............................................................................................................................ 6

Figure 8 - Vibration Meter 2 ......................................................................................................................... 7

Figure 9 - Vibration Meter 3 ......................................................................................................................... 8

Figure 10 - Fluke 810 ..................................................................................................................................... 9

Figure 11 - Wear in Gears ........................................................................................................................... 10


Introduction Machine fault problems are broad sources of high maintenance cost and unwanted downtime across

the industries.

The prime objective of maintenance department is to keep machinery and plant equipment’s in good

operating condition that prevents failure and production loss.

Vibration signature analysis techniques for machine fault identification are the most popular among

other techniques.

Vibration monitoring is based on the principle that all the system produces vibration.

When a machine is operating properly, the vibration is small and constant, however, when faults

develop and some of the dynamic process in the machine changes, there will be changes in vibration

spectrum observed.

After the review of previous published work, it is concluded that gear fault, bearing fault, and coupling

fault are studied for research purpose to fault signature analysis.

Maintenance Engineering There are many types of maintenance Engineering discipline but we will only care about the most 3

discipline that is relative in terms of Vibration usage in faults detection

Preventive Maintenance Preventive maintenance (PM) consists of scheduled inspection and upkeep that is specifically intended

to prevent faults from occurring during subsequent operation. Inept PM, however, can also cause

problems.

Predictive Maintenance Predictive maintenance is a preventive type of maintenance program that anticipates failures that can

be corrected before total failure. Predictive maintenance can also determine that a failure is about to

occur.

Unscheduled Maintenance Unscheduled or nonscheduled maintenance must be done immediately when an emergency affects the

productivity of the plant. This is maintenance to “fix what is broken” or provide a work-around so that

the operation that was started can be finished


Why Make Condition Monitoring Condition Monitoring is one of the Predictive Maintenance techniques in fault detection of machine

elements

Figure 1- Condition Monitring

Fault Diagnostics The main advantage of making vibration measurements on rotating machinery is the possibility to detect faults, before they make the machine break down, and thereby reduce economic losses, such as damaged equipment and production loss.

To this the constant percentage band width spectrum has shown to be the most efficient.

When a fault is detected, vibration analysis can be used to diagnose the fault.

Making diagnosis using vibration analysis requires skill and experience.

Additional measurements of FFT spectra and phase measurements is often required. In the following some simple rules for the most common machine faults are drawn up giving the fault type and a characteristic vibration measurement.

The spectrums in the examples are all made as drawings, in order to emphasize the typical feature of each fault.


There are mainly 5 techniques in measuring and detecting faults in any machinery systems which are the

following:

But from where is the vibration is coming from in the first place the answer of this question will help us to know more about the usage of vibration in fault diagnostics

So the next question that should appear after knowing sources of vibration is how can we allocate the fault of machine element in a machine that have many elements to operate

And that by using Spectrum graph created by transducer signals that have been filtered and processed

By vibration analyzer and finally transformed from time wave form spectrum using FFT

Figure 3 Source of Vibration

Figure 2 - What to Measure for a fault


Using Spectrum in Fault Diagnostics Mainly there is two techniques are used for evaluating vibrations of machine elements in the spectrum

First : Making Reference for each measuring point and compare the results using ISO 10816 for non-

rotating parts and ISO 10817 for rotating shafts.

Figure 5 - Measurement References

Figure 4 - Spectrum of a Machine


Second Technique is Trending which we compare the results of single or Multi-Elements vibration

spectrum to specific dates assign by the predicative maintenance protocol of the organization or the

machine supplier.

Equipment’s & Instrumentations used in Fault Diagnostics

Measuring instrumentations

Vibration Meter PCE-VD 3

Figure 7 - Vibration Meter

Usage :

it can be used for many different applications like, for instance, shipment control. Furthermore the

PCE-VD 3 vibration meter can be used for sports, medicine or for recording of movements 0f 1 to 3

axes.

Figure 6 - Trending in Vibration Signals


Features :

Measurement Range ±18 g

Accuracy ± 0.5 g

Resolution 0.00625 g

Frequency Range 0 ... 60 Hz

Dimensions 95 x 28 x 21 mm

Power Supply Interchangeable 3.6 V

lithium battery

How it measures :

Acceleration force is measured along the X, Y and Z axes. Since the PCE-VD 3 vibration meter is in

motion while it is recording data, alterations are recorded for the three axes. The PCE-VD 3 vibration

meter can be placed anywhere due to its robust and magnetic bracket

The internal sensor of the PCE-VD 3 vibration meter has a measurement range of ±18g per axis. The

PCE-VD 3 vibration meter can be easily programmed through a software. All data can be sent to a PC

or portable computer via the USB port easily and quickly.

Vibration Meter PCE-S 41:

Figure 8 - Vibration Meter 2

Usage :

This Vibration Meter can be used for detecting noise in machine components, such as gears, valves,

vents and pumps This makes the Accelerometer a useful tool in inspecting noise and vibration, giving

the maintenance team the chance to locate the source of a problem before it becomes too costly.


Features :

Frequency range 100 Hz to 10 kHz

Power 9V battery

Volume Adjustable

Dimensions 206 x 50 x 32mm

Sensors (attachable) 1 x 290mm ; 1 x 70mm (long)

Sensor composition Steel

Weight 240g, with battery

How it measures :

The enclosure of the accelerometer is made of ABS plastic which is comfortable to hold and operate.

The device uses a piezoelectric transducer which can detect very low resonant noises. The earpiece is

equipped with an adjustable headset that has a 2m cable.

Vibration Meter PCE-VMS 504

Usage :

wireless vibration monitor with external vibration sensors/ to measure acceleration, speed, offset and

temperature

Features :

Communication type wireless

Frequency band

GHz 2.4

Dimensions 250 x 210 x 100 mm

Weight 2400 g

Frequency range 5 Hz ... 10 kHz

Figure 9 - Vibration Meter 3


how it measures :

The wireless vibration monitor PCE-VMS 504 detects vibration within an acceleration range of up to 30

g and a frequency range between 5 and 10 KHz. The wireless vibration monitor therefore features

external vibration sensors, which measures vibrations at machines to transfer those wireless to a

receiving unit. Those sensors can be easily attached to a machine due to its magnetic base. There they

can not only measure vibrations at machines and transfer those to a computer but also recognize

temperatures between -20 and +120 °C.

Fluke 810 Vibration Tester

Features and benefits

On-board identification and location of the most common mechanical faults (bearings,

misalignment, unbalance, looseness) focus maintenance efforts on root cause, reducing

unplanned downtime

Repair recommendations advise technicians on corrective action

On-board context sensitive help provides real-time tips and guidance to new users

2 GB expandable on-board memory provides enough space for your machinery’s data

Self-test function ensures optimal performance and more time on the job

Tri-axial accelerometer reduces measurement time by 2/3 over single axis

accelerometers

Viewer PC Software expands data storage and tracking capacity

Use the Fluke 810 Vibration Tester to:

Troubleshoot problem equipment and understand the root cause of failure

Survey equipment before and after planned maintenance and confirm the repair

Commission new equipment and ensure proper installation

Provide quantifiable proof of equipment condition and drive investment in repair or

replacement

Manufacturer

Fluke – USA

Figure 10 - Fluke 810


Faults Now we will try to give some practical examples on some of the most common faults in machine tools

and the way of detecting them also we will try to discuss some of the causes , treatment and prevention

techniques for some of the faults

Gear wear fault

Fault Name Fault Type Causes Place Diagnosis Treatment Prevention

Tooth wear Gear Fault 1-Lack of lubrication 2-Over loading 3-Poor gear meshing 4-using different meshing gear materials

Any gear meshing in any machine.

It could be recognized through vibration spectrum analysis. It will be appear as a gradually growing frequency with growing amplitude with lower side bands approximately as shown in figure

After wear in gear there is no solution except changing it.

1-Monitor the condition of the gear mesh by schedule. 2-assureance of good lubrication and suitable working conditions.

Figure 11 - Wear in Gears


Other Faults

Fault Name Causes location Diagnosis Treatment Prevention

Unbalanced

The centrifugal force that arise from: In design (some parts may be not perfectly symmetrical) Technological (non-homogenous material) manufacturing (everything is produced in some tolerances, rotating parts exhibit run out) In mounting (namely with mounted rotors)

In a rotor when the mass center axis is different to its running center axis. At 1- Pump, 2- Fans, 3- Propellers

and 4- Turbo

machinery

From vibration spectrum analysis: Appear in high vibration amplitude in radial directions at the rotational component (1X).

Adding mass Removing mass Shifting mass

Either the entire rotor is balanced or its individual parts before the final assembly and then a final balance is carried out.

Misalignment Changes in clearances result in worse machine performance. thermal growth uneven applied loads inappropriate foundations

At rotating systems: A machine set rotors one to each other. At Gears, Shafts, etc.

Also from vibration spectrum analysis: Angular Misalignment: characterized by large axial vibration, which is out-of-phase

by a designer, Enough combine elements for adjusting the position of the rotor axis towards the axis of the housing to the construction and Suitable choice of rotor couplings, including measures to establish their parts one to each other.

References Machine Condition Monitoring by Dr Mohd Salman Leo - Institute of Noise & Vibration

University Technology Malaysia

Machine Fault Signature Analysis by Pratesh Jayaswal - International Journal of Rotating

Machinery Volume 2008 (2008), Article ID 583982

Maintenance Engineering Handbook Six Edition by Lindlet R.Hiffins Puplished by McGraw-Hill

Instrumentations Manufactures Websites

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