MAGNETIC FLUX LEAKAGE SYSTEM FOR WIRE ROPE INSPECTION

USING BLUETOOTH COMMUNICATION

MUHAMMAD MAHFUZ BIN SALEHHON

UNIVERSITI TEKNOLOGI MALAYSIA

MAGNETIC FLUX LEAKAGE SYSTEM FOR WIRE ROPE INSPECTION

USING BLUETOOTH COMMUNICATION

MUHAMMAD MAHFUZ BIN SALEHHON

A thesis submitted in fulfillment of the

requirements of the award of the degree of

Master of Science (Physics)

Faculty of Science

Universiti Teknologi Malaysia

NOVEMBER 2014

iii

ACKNOWLEDGEMENTS

First of all, I want to pay my heartiest gratitude to Almighty Allah for

granting us the strength, hardiness and guidance throughout out my study. Indeed, it

was through His Consent and Blessing that I have managed to complete this

research. Foremost, I would like to express my sincere gratitude to my advisor

Associate Professor Md. Supar bin Rohani for his continuous support of my study

through motivation, teaching, comment, criticism and providing me with an excellent

atmosphere for doing research.

Special appreciation and thanks goes to lecturers who were willing to help in

completion this research. Thanks for their brilliant comments and suggestions. I also

would like to take this opportunity to express the deepest appreciation to my

supportive friends who was always making my life happier. Many thanks also to

workshop and laboratory technician for their helping hands.

Last but not least, my heartiest thank you to my parents and beloved family

for their moral and financial support. Their sincere and kind help has really enhanced

my spirit, determination and enthusiasm to go on with this assignment until the end. I

am truly and will always be indebted and grateful to them. Words cannot express

how grateful I am to be part of this family, their prayer for me was what sustained

me thus far.

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ABSTRACT

A wireless data communication Magnetic Flux Leakage (MFL) system for

steel wire rope cable inspection has been designed and constructed to facilitate the

remote data transferring. The system incorporates permanent magnets and Hall

Effect sensor arrays, with its signal processing circuit and data acquisition system.

Strong permanent magnetic discs of about 1T are used to magnetize the cable. Hall

Effect sensors are arranged in parallel to detect the leakage flux from different

angles. The system is battery operated, which is three units of AA batteries function

as a power source. Another three units of AA batteries can also be fitted in as the

backup power supply. The wireless data communication system has been constructed

using Bluetooth module. The signals are digitized using an Emant380 Bluetooth data

acquisition module consist of six channels of differential multiplexed analog-to-

digital converter, and the data can be stored in computer or Smartphone’s memory.

Python programming language is used to collect and interpret the data in a graphical

form. This system use Tkinter graphical user interface toolkit for the computer while

HTML is a platform for full screen user interface display on Smartphone. The screen

displays the location and the flaws signal. System was tested and evaluated on

various simulated wire rope defects of different depth and width, ranging from 2 mm

to 6 mm depth and 1 mm width and also 2 mm to 6 mm width and 2 mm to 3 mm

depth. This system has a relatively high sensitivity for the detection of magnetic flux

leakage through defects with a depth of 2 mm and 1 mm wide.

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ABSTRAK

Sistem pemeriksaan kebocoran fluks magnet (MFL) komunikasi data tanpa

wayar untuk pemeriksaan kabel dawai keluli telah direka dan dibina untuk

membolehkan pemindahan data jarak jauh. Sistem ini menggabungkan magnet kekal

dan susunan penderia Kesan Hall, lengkap dengan litar pemprosesan isyarat dan

sistem pemerolehan data. Cakera magnet kekal dengan kekuatan 1T digunakan untuk

memagnetkan kabel. Penderia Kesan Hall disusun secara selari untuk mengesan

kebocoran fluks dari sudut yang berbeza. Sistem ini beroperasi menggunakan tiga

unit bateri AA berfungsi sebagai pembekal kuasa. Tiga unit bateri AA yang lain

boleh juga digunakan sebagai bekalan kuasa sokongan. Sistem komunikasi data

tanpa wayar telah dibina menggunakan modul Bluetooth. Isyarat didigitkan

menggunakan modul pemerolehan data Emant380 Bluetooth enam saluran

multipleks berbeza penukar analog-ke-digital, dan data disimpan di dalam memori

komputer atau telefon pintar. Bahasa pengaturcaraan Python digunakan untuk

mengumpul dan mentafsir data dalam bentuk grafik. Sistem ini menggunakan

perkakasan antara-muka pengguna grafik Tkinter bagi komputer manakala HTML

sebagai antara-muka pengguna pada platfom paparan skrin penuh telefon pintar.

Skrin memaparkan lokasi dan isyarat kecacatan. Sistem telah diuji dan dinilai pada

berbagai simulasi kecacatan kabel dengan kedalaman dan lebar pembeza masing-

masing pada julat kedalaman 2 mm hingga 6 mm dan 1 mm lebar serta pada julat 2

mm hingga 6 mm lebar dan kedalaman 2 mm hingga 3 mm. Sistem ini mempunyai

kepekaan yang tinggi bagi pengesanan kebocoran fluks magnet melalui kecacatan

dengan kedalaman 2 mm dan 1 mm lebar.

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TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

ACKNOWLEDGEMENT iii

ABSTRACT iv

ABSTRAK v

TABLE OF CONTENTS vi

LIST OF TABLES ix

LIST OF FIGURES x

LIST OF SYMBOLS xii

LIST OF ABBREVIATIONS xiv

LIST OF APPENDICES xvi

1 INTRODUCTION

1.0 Introduction 1

1.1 Overview 1

1.2 Problem Statement 4

1.3 Objectives 4

1.4 Scope 5

1.5 Significance of Study 5

2 LITERATURE REVIEW

2.0 Introduction 6

2.1 Non-Destructive Testing (NDT) 6

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2.1.1 Theory of Magnetism 7

2.1.2 Types of Defects 8

2.1.3 Detection Methods 9

2.1.3.1 Wire Inspection using the

Radiography Technique 10

2.1.3.2 Ultrasonic Testing 12

2.1.3.3 Eddy Current 14

2.1.3.4 Electromagnetic Testing 16

2.1.3.5 Type of Inspection Methods 18

2.2 Magnetic Flux Leakage (MFL) 21

2.3 Magnetic Sensor 25

2.3.1 Hall Effect Sensor 25

2.3.2 Inductive Coils 27

2.4 Mobile Application 28

2.5 Graphical User Interface (GUI) 29

3 DESIGN AND CONSTRUCTION OF MAGNETIC FLUX

LEAKAGE SYTEM

3.0 Introduction 30

3.1 The Design of Magnetic Flux Leakage (MFL) 31

3.2 Magnetizers 34

3.3 Sensor 35

3.4 Sensor Circuit 37

3.5 Data Acquisition System (DAQ) 39

3.5.1 Data Acquisition (DAQ) for Computer

Program 40

3.5.2 Data Acquisition (DAQ) for Mobile Phone

Program 43

4 RESULTS AND DISCUSSIONS

4.0 Introduction 49

4.1 Results 50

4.2 Discussions 56

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5 CONCLUSIONS AND RECOMMENDATIONS

5.0 Introduction 58

5.1 Conclusions 58

5.1 Recommendations 59

REFERENCES 61

Appendices A - G 65

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LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Performance comparison for similar inspecting technology (Wang,

2011) 11

2.2 Type of NDT Inspection Methods 19

4.1 The photo and dimension for different depth of discontinuities 51

4.2 The location and amplitude for different depth of discontinuities 53

4.3 The photo and dimension for different width of discontinuities 54

4.4 The location and amplitude for different width of discontinuities 56

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LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Radiographic testing method (August, 1999) 10

2.2 System structure (Wang, 2011) 12

2.3 Block diagram of the magnetostrictive guided wave inspection

system (Xu, 2013) 13

2.4 Information taken from a strand without flaws, at three separate

separations between the receiver and transmitter (Xu, 2013) 14

2.5 Schematic of the eddy current detection setup (Cao, 2012) 15

2.6 The principle used in the LMA rope tester (Weischedel, 1989) 17

2.7 The principle used in the LF rope tester, different coil

arrangement 18

2.8 Modified main-flux system for wire rope inspection

(Jomdecha, 2007) 22

2.9 Wire rope sample with artificial defect (Jomdecha, 2007) 23

2.10 LMA examination signals of ten artificial defects

(Jomdecha, 2007) 23

2.11 Magnetic field lines of refraction at the interface

(Jomdecha, 2007) 23

2.12 Magnet line in wire rope (Zhong, 2012) 24

2.13 Diagram of MFL field of disability (Chai, 2009) 25

2.14 The operation principle of the Hall Effect plate (Kalwa, 1987) 27

2.15 The inductive sensor principle for the radial component

(Kalwa, 1987) 27

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3.1 Actual photo of the MFL system 31

3.2 (a) Schematic diagram from the top, side and bottom of the MFL

system 32

3.2 (b) Schematic diagram from both sides of the MFL system 33

3.3 Block diagram for the MFL system 33

3.4 The magnetizer with backing plate/yoke 34

3.5 Hall Effect sensor circuit 36

3.6 Hall element with center of max sensitivity (Appendix A) 37

3.7 Hall Effect sensor IC with resistor 38

3.8 Modified sensor array 38

3.9 Circuit diagram 39

3.10 3.3V regulator (Appendix E) 40

3.11 Flowchart in DAQ for the computer based system 41

3.12 GUI using Tkinter 42

3.13 The icons for Android application used in this research (Test

EMANT380, SL4A and Python for Android) 43

3.14 Flowchart in DAQ for the mobile based system 44

3.15 Website for Android DAQ installation 45

3.16 Script Layer for Android 45

3.17 Py4A 46

3.18 Test Emant380 46

3.19 Interface for tablet using UI 47

4.1 Layout of an example cable at the set of the experimental setup 50

4.2 100 cm wire rope sample with different depth artificial defects 51

4.3 (a) Signal from computer based system for different depth of

discontinuities 52

(b) Signal from mobile based system for different depth of

discontinuities 52

4.4 120 cm wire rope sample with different width artificial defects 54

4.5 (a) Signal from computer based system for different width of

discontinuities 55

(b) Signal from mobile based system for different width of

discontinuities 55

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LIST OF SYMBOLS

H - Magnetic field

B - Magnetic induction

μ - Permeability

μ - Micro

M - Magnetization

- Susceptibility

Ui - Excitation signal input

Uo - Sensing signal output

V - Finite speed

Bt - Tangential component

Br - Radial component

RH - Hall coefficient

dH - Plate thickness

I - Current

VH - Current voltage

R - Distance

zi - Number of turns in ith coil

Øi - Magnetic flux passing through the core of the ith coil

T - Time

k - kilo

Hz - Heartz

V - Volt

mm - milimeter

sec - second

T - Tesla

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M - Mega

m - meter

kH - Hall generator sensitivity

tan - tangent

π - phy

Ω - Ohm

VDD - IC power supply pin

GND - Ground

AIN - Analog input

F - Farad

COM - Component Object Model

CSV - Comma Separated Value

Py - Python

t - Thickness

n - Number of electron

e - electron

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LIST OF ABBREVIATIONS

NDT - Non-Destructive Testing

NDE - Non-Destructive Evaluation

MFL - Magnetic Flux Leakage

AE - Acoustic Emission

EM - Electromagnetic Testing

DR - Digital Radiography

UT - Ultrasonic Testing

A/D - Analog to Digital

ADC - Analog to Digital Converter

NN - Neural Network

RBF - Radial Basis Function

LMA - Loss of Metallic Cross-sectional Area

LF - Localized-Flow

DC - Direct Current

API - Application Programming Interface

RPC - Remote Procedure Call

GUI - Graphical User Interface

UI - User Interface

DAQ - Data Acquisition System

N - North

S - Sourth

PC - Personal Computer

Py4A - Python for Android

SL4A - Script Language for Android

HTML - Hyper Text Markup Language

xv

Tk - Tkinter

Tcl - Tool Command Language

IC - Integrated Circuit

RS - Radiospares

Ltd. - Limited

IDLE - Integrated Development Environment

xvi

LIST OF APPENDICES

APPENDIX NO. TITLE PAGE

A Hall Effect Sensor – Honeywell 634SS2 Datasheet 65

B Neodymium Iron Boron NdFeB - N816 Datasheet 66

C EMANT380 68

D Bridge Sensor Application Adaptor for Emant300, Emant380 72

E MCP1700 74

F Python script for collecting data using GUI 84

G Python script for display graph on mobile screen using UI 89

CHAPTER 1

INTRODUCTION

1.0 Introduction

This chapter elucidates the background study of the wire rope, its usage in the

industry and the flaws of the ropes when utilized for public purposes. Methods on the

cable‟s damage detection are discussed briefly in this chapter, whereas problems and

objectives of this study are stated with sufficient information which enables the

execution of this study. In order to ensure that this research can be carried out

efficiently, the scope of the study is explained evidently. Last but not least, in order

to reveal the contributions of the wire rope to the world of research the significance

of the study is framed with precise information.

1.1 Overview

A cable or rope is one of the most ancient inventions invented by humans.

Ropes were created either from natural or man-made fibers and metal wires to adapt

2

to our living conditions (Laura, 1995). A wire rope is composed of twisted wires

which constitutes of a very complex structure which makes it flexible in bending and

combines the strength on the axis and stiffness. Nowadays, modern rope offers a

variety of constructions for different levels of diameter with helical complexity

(Chaplin, 1995). Ropes are widely used as a major burden in various industrial

applications and often involve critical safety components (Wang, 1988). Many ropes

degrade due to broken wires and strands caused by fatigue, abrasion or mechanical

damage. Since the introduction of security codes, regular inspections were conducted

by the responsible authorities.

Wire rope malfunctions lead to damage in expensive equipments and

fatalities. Therefore, there are a number of Non-Destructive Testing (NDT) methods

to be applied, such as visual inspection, magnetic flux leakage methods, X-ray,

ultrasonic and acoustic emission (Kwun, 1988). One of the most common methods is

the visual examination and measurement of the rope‟s external diameter. However

by implementing this method, only the flaws on the surface can be detected and it

also requires an extensive experiment. This basic methodology must be used as an

addition to other test procedures such as electromagnetic (EM) method, a method

used on wire ropes and cables which are constructed from synthetic materials.

Another technique for wire rope inspection is radiography testing. This

method uses X-rays or radioactive isotopes as a source of radiation. The radiation

passes through the material where it will be captured on a film or a digital device.

The radiation composed of high energy with short wavelength and produces an

electromagnetic wave that is seen as visible light. Once the film image had been

processed of varying densities, broken wires and the extent of damage sustained by

the core could be determined by the change in density (Halmshaw, 1982).

The screening test volume is also known as the propagation of ultrasonic

waves (Ahmet, 2012). This method uses propagation characteristics of high-

frequency sound waves caused by horizontal impulsive force of the rope. This

3

technique can detect imperfections or changes in the material properties by applying

measurement of various thickness of metal and non-metal rope material.

One of the most conventional approaches to test the wire rope is through

Magnetic Flux Leakage (MFL) inspection. MFL is a method used to identify

damages in ferromagnetic materials. It is suitable for wire rope tests because of its

resolution and high accuracy. This technique involves a magnetic field with the

material and measuring the magnetic flux leaking from the surface (Marble, 2009).

C. Jomdecha and A. Prateepasen in 2007 introduced the design of modified

electromagnetic main-flux for steel wire rope inspection where the electromagnetic

field strength can be adjusted to produce a leakage filed from flaws of various large-

diameter ropes (Jomdecha, 2007).

Back in 1987, design and operating principles of four new Hall Effect sensors

for magnetic testing of steel ropes were presented by E. Kalwa and K. Piekarski. The

radial or tangential component of the magnetic flux leakage can be measured using

these sensors (Kalwa, 1987). While in 1989, H. R. Weischedel and R. P. Ramsey

used modern non-destructive test methods for the qualitative and quantitative

inspection (Weischedel, 1989). Based on previous projects involving these topics, it

can be concluded that the scope of study is focused more on how to improve the

level of sensitivity detection of the equipment used whereas there were not many

research conducted on the transferring data network process enhancement.

Thus, through this project, the Magnetic Flux Leakage (MFL) system is

established together with the Bluetooth technology application. This system can be

used for overhead cables, cable cars, suspension bridge or moving cable in lift hoist.

Apart from that, the MFL system also benefits personnel inspector with difficult

access cables and hostile environments. This system could be adapted at any

locations and the cable can be monitored for the data could be retrieved remotely.

4

Wire ropes are inspected periodically initial from the time of installation till

the time of replacement. The closer the replacement time of the ropes, the more

frequent the inspection. For this research, it will be easier to test the cable by using

portable devices. In this study, a mobile application was used as a tool for scanning

system. The application has been developed with low cost manufacturing processes

which results in, people familiarizing in this field for it is important to the industrial

sector.

1.2 Problem Statement

The existing Magnetic Flux Leakage (MFL) system requires a set of

equipment which is incompatible in many situations. Moreover finding a Bluetooth

technology developed with a magnetic flux leakage system detector is extremely rare

in this industrial field.

1.3 Objectives

The objectives of this research are as below;

1) To design and construct a portable magnetic flux leakage system for

inspecting wire rope samples.

2) To construct a wireless data communication system for transferring data

from the device using Bluetooth module.

3) To test and evaluate the cable flaws by using the magnetic flux leakage

system.

5

1.4 Scope

Experiment that were carried out during this research implemented an MFL

system for the inspection of steel wire ropes only which follows the maximum

diameter up to 20mm the size of pipe installed on the device. It features a wireless

Bluetooth system in transferring data within room space. Meanwhile, for the

programming part, Python (script language) is used in detecting the device to

compare the result. Both end of the cable were clamped at two different tables using

an iron vice to which gave the cable sufficient stretch. By stretching the cable it

creates the required stimulated defects such as wire breakage. Finally the device goes

through the cable in one direction to detect the area of discontinuities.

1.5 Significance of Study

A portable system is generated using the MFL method. Therefore, positive

outcome of this study is the ability to detect any defects or discontinuity on steel wire

ropes from a distance simply by using the Bluetooth technology. Furthermore, the

process of transferring data from the system for data storage is further enhanced in

this study so that it is efficient and user friendly. Computer based system or mobile

based system are two of the options available that suits the program. There are two

slots (main and backup) of batteries for this device and each of them can fill up to

three AA batteries. With these two battery slots, it is enough to accommodate the

power supply over a period of time to conduct the test.

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