io report final

SCHOOL OF MECHANICAL AND AEROSPACE ENGINEERING

INDUSTRIAL ORIENTATION REPORT(23th May – 29th July 2011)

I

Name of student: Lim Chong Heng

Matriculation number: 081760G15

Company: Turbine Overhaul Services

NTU Tutor: Asst Prof Moon Seung Ki

TOS Supervisor: Process Engineer Tong Yap Chung

Table of Contents

Abstract........................................................................................................................................................ III

Acknowledgement.......................................................................................................................................IV

List of Tables..............................................................................................................................................VII

List of Figures...........................................................................................................................................VIII

List of Figures in Appendix A......................................................................................................................X

List of Figures in Appendix B.......................................................................................................................X

List of Abbreviations...................................................................................................................................XI

1. Introduction to Industrial Orientation................................................................................................1

1.1 Background................................................................................................................................1

1.2 Objective....................................................................................................................................1

1.3 Scope..........................................................................................................................................2

2. Introduction of the Company.............................................................................................................3

2.1 United Technologies Corporation..............................................................................................3

2.2 Turbine Overhaul Services........................................................................................................5

2.3 Organization Culture: ACE system...........................................................................................9

2.4 Organization Mission and Vision............................................................................................11

3. Background Technical Information.................................................................................................12

4. Improvement Project: Metal Tester.................................................................................................13

I

4.1 Introduction to ACROMAG Metal Tester...............................................................................14

4.2 Problems of current practice (coating tests).............................................................................16

4.3 Overview and Scope of Project................................................................................................18

4.4 Establishing Setup Procedure of Metal Tester.........................................................................20

4.5 Differentiating Plasma from Turbofix® Surface.....................................................................22

4.6 Differentiating coated from uncoated surface..........................................................................25

4.7 Investigating Repeatability of the Test....................................................................................28

4.8 Differentiating Different Thickness of Plasma Coating..........................................................31

4.9 Conclusion of experiment........................................................................................................37

5. Operation Facilitation: Preparation of Operation Instruction Documents.......................................40

5.1 Engine Manual.........................................................................................................................41

5.2 Drafting of Operation Instructions...........................................................................................42

5.3 SOLUMINA Database.............................................................................................................47

6. Conclusion and Author’s Reflections..............................................................................................50

7. References........................................................................................................................................54

APPENDIX A – Ace Tools................................................................................................................A1–A10

APPENDIX B – Compressor, Turbine and Transition Ducts..............................................................B1–B2

APPENDIX C – Heat Tint Testing.............................................................................................................C1

II

Abstract

The author was attached to Turbine Overhaul Services (TOS) Private Limited during his 10

weeks of Industrial Orientation. Attached to the Engineering Department, his job scope covers

two main areas – conduct improvement projects and perform facilitation work for the shop-floor

repair stations. In the ACROMAG Metal Tester Project, the author investigated the procedures

involved in initializing the equipment and also analysed the feasibility of using the equipment to

differentiate different specimens with different coating thickness. However, the author was not

able to complete the entire project due to the short attachment period. Although the project was

not completed, the author analysed his obtained results and provided an overview of the

remaining portion of the experiment. In addition, the author prepared Operation Instruction

documents to facilitate the operations of the repair process line. Other than the above mentioned

job scope, the author was also involved in many other tasks which were elaborated in the

Industrial Orientation Logbook.

This report aims to present on the work done during the 10 weeks attachment at Turbine

Overhaul Services Private Limited (TOS). It also informs the readers on the company

background and the department which the writer is attached to and includes one of the projects

done during the attachment period.

This report will also include the learning points that the author has gained in this attachment,

how it had enhanced his knowledge learnt from his course of study in NTU.

III

To protect the company’s interest, names, dimensions, materials as well as other sensitive

information would not be provided in this report.

IV

Acknowledgement

The author would like to express his gratitude to TOS Pte Ltd for providing this industrial

orientation opportunity. The pleasant working environment in TOS has also made this

attachment an enjoyable one. Throughout this internship, the author has learnt much from the

engineers in the department as well as through various projects that have been entrusted to the

author.

This author would like to thank the LPT Vanes Process and Methods Engineers from the

Engineering Department for strengthening his interest in the engineering field. The engineers are

as follows:

Mr Gary Tong Mr Sia Wee Keong

Mr Chung Boon Tat Mr Adrian Teo

Mr Hor Weng Keong Mr Lim Shi Chuan

In addition, he would like to thank the operators for their support and time in providing technical

assistance on the shop floor. Despite their busy work schedule and deadline for production, they

shared their valuable knowledge and experiences with the author, enhancing the author’s

practical knowledge.

In particular, the author would like to thank the following three people who have sacrificed their

precious time to provide support to the author throughout his internship:

V

Mr Gary Tong – Methods and Process Engineer

The author would like to express his heartfelt gratitude and sincere appreciation to his industrial

supervisor - Mr Gary Tong for his unwavering guidance and continuous support during his

attachment period at TOS. Mr Tong’s years of expertise and experience had provided the author

with many critical thinking experiences. The author was extremely grateful to Mr Tong for his

patience in explaining the rationale of tasks he was assigned with, making his learning journey in

TOS a much more fruitful one. Apart from sharing his technical knowledge, Mr Tong also

provided career advices and lifelong skills, things which cannot be learnt from books and will be

indispensible to the author’s future.

Mr Sia Wee Keong – Methods and Process Engineer

The author would like to thank Mr Sia Wee Keong for engaging him in his development

projects. Taking every opportunity in involving the author whenever he could, Mr Sia would

share with him his rich knowledge and expertise in his field of work. Through the interactive

projects Mr Sia had assigned him with, the author had improved on his analytical and

interpretation skills. By placing great trust and confidence in the author’s work, the author was

able to exhibit his capabilities to the fullest.

Dr Moon Seung Ki – NTU Tutor

Last but not least, he would like to express his appreciation to his NTU tutor, Professor Moon

Seung Ki for his support during the author’s attachment period in TOS. Dr Moon had been

extremely helpful in providing guidance to the author and clarifying the author’s uncertainties,

allowing the author to adapt to the company in the first few weeks of attachment.

VI

The author would like to thank him for finding time to visit the company despite his busy

schedule. His concern for the author regarding problems faced during the attachment was deeply

appreciated. The short interview session that the author had with Dr Moon also proved to be a

valuable experience as it aided the author to reflect on the past experiences and refresh on the

valuable knowledge learnt in TOS.

VII

List of Tables

Table 1: Overview of UTC’s seven business units..........................................................................4

Table 2: Turbofix® and Plasma surface readings.........................................................................24

Table 3: Coated and non-coated surface readings (ITD of Engine B)..........................................27

Table 4: Coated and non-coated surface readings (OTD of Engine B).........................................29

Table 5: Summary of results for ACROMAG Metal Tester Project.............................................37

Table 6: Incomplete Table for future continuation........................................................................38

Table 7: Illustration of Table for future continuation (non linear relationship)............................39

VIII

List of Figures

Figure 1: Flow-chart showing the companies under UTC...............................................................3

Figure 2: Pie-chart showing the units' individual revenue for 2009 [2].............................................4

Figure 3: TOS external facade.........................................................................................................5

Figure 4: TOS major shareholders...................................................................................................6

Figure 5: The ACE cycle...............................................................................................................10

Figure 6: A breakdown of 8 of the essential ACE tools................................................................10

Figure 7: Notch indication on development specimen..................................................................13

Figure 8: ACROMAG Metal Tester [3]...........................................................................................14

Figure 9: Seebeck Effect [4]............................................................................................................14

Figure 10: Testing a metal specimen.............................................................................................15

Figure 11: Theory of ACROMAG Metal Tester...........................................................................15

Figure 12: ACROMAG Metal Tester scales.................................................................................16

Figure 13: Vane before heat tint test..............................................................................................17

Figure 14: Vane after heat tint test................................................................................................18

Figure 15: Maximum deflection above scale for warming up.......................................................21

Figure 16: ITD (Engine A) Specimen...........................................................................................22

Figure 17: ITD (Engine A) terminologies.....................................................................................23

Figure 18: Plasma and Turbofix® surface.....................................................................................23

Figure 19: ITD (Engine B) Specimen............................................................................................25

Figure 20: OTD (Engine B) Specimen..........................................................................................28

Figure 21: Sectioned rear face of ITD (Engine A)........................................................................32

IX

Figure 22: Preparation stages of specimen....................................................................................33

Figure 23: Dimension to be taken..................................................................................................34

Figure 24: Zeroing of a Dial Indicator...........................................................................................35

Figure 25: ITD (A) installed on Fixture for Dial Indicator measurement.....................................35

Figure 26: Specimen after blending...............................................................................................36

Figure 27: Specimen with plasma coating (X inches thickness) on first section..........................36

Figure 28: Illustration of graph for future continuation (linear relationship)................................39

Figure 29: Visual Aids for Inspectors (1)......................................................................................43

Figure 30: Visual Aids for Inspectors (2)......................................................................................44

Figure 31: Complicated schematic from Engine Manual..............................................................45

Figure 32: Simplified schematic in Operation Instruction document............................................45

Figure 33: Visual Aids for Machinists...........................................................................................46

Figure 34: SOLUMINA database user-interface...........................................................................47

Figure 35: Standard Format of Operation Instruction Document..................................................49

X

List of Figures in Appendix A

Figure A - 1: Examples of “Straighten” concept in practice.......................................................A1

Figure A - 2: Example of a poster reminding everyone on the 5 Cardinal Rules of Safety........A2

Figure A - 3: 6S logo...................................................................................................................A3

Figure A - 4: The 5 Steps for QCPC implementation..................................................................A3

Figure A - 5: An example of a typical SIPOC chart....................................................................A5

Figure A - 6: Definition of “turn-backs”.....................................................................................A5

Figure A - 7: One possible system of recording turn-backs........................................................A6

Figure A - 8: Graph showing the number of turn-backs recorded against duration of the QCPC

programme....................................................................................................................................A7

Figure A - 9: different types of data-analysis tools available for QCPC.....................................A7

Figure A - 10: Bar-chart showing how many turn-backs, and the time lost................................A8

Figure A - 11: A QCPC trend chart before and after implementation.......................................A10

List of Figures in Appendix B

Figure B - 1: Jet engine [6].............................................................................................................B1

XI

List of Abbreviations

TOS – Turbine Overhaul Services

TCS – Turbine Coating Services

ST – Singapore Technologies

UTC – United Technologies Corporation

IAE – International Aero Engines

EBPVD – Electron Beam Physical Vapour Deposition

GSE – Global Service Engineering

LPTV – Low Pressure Turbine Vanes

ACE – Achieving Competitive Excellence

6S – Sort, Straighten, Shine, Standardize, Sustain and Safety

QCPC – Quality Clinic Process Charts

LP / LPT – Low Pressure / Low Pressure Turbine

HP / HPT – High Pressure / High Pressure Turbine

RPM – Revolutions Per Minute

TAT – Turn-around time

ITD – Inner transition duct

OTD – Outer transition duct

N.A. – Not Applicable

OEM – Original Equipment Manufacturer

QA – Quality Assurance

NTU – Nanyang Technological University

XII

FPI – Fluorescent Penetration Inspection

XIII

1. Introduction to Industrial Orientation

1.1 Background

All third year Engineering students pursuing a Bachelor’s Degree in Nanyang

Technological University (NTU) will have to undergo a 10 weeks Industrial Orientation

or a 22 weeks Industrial Attachment in a related company of their choice.

The industrial attachment prepares the student for the working industry and serves to

train the student to apply engineering practices in real life industrial environment as part

of an academic curriculum. It enhances and inculcates academic, personal and

professional competencies in the students. In terms of personal competencies, students

should observe and understand the skills of professional, engineers learn work place

ethics and values as well as re-evaluate personal career goals. Students should also use

the attachment period to hone their professional competencies in terms of improving their

oral & written communication skills, further develop their interpersonal skills whilst

working with a team and extend knowledge of life-long learning skills.

1.2 Objective

This report aims to present on the things learned and done during the 10 weeks

attachment at Turbine Overhaul Services Private Limited (TOS). It also informs the

readers on the company background and the cell information which the writer is attached

to and includes the project done during the attachment period.

1

1.3 Scope

This report covers information on the company background, the department the author

was attached to, followed by the ACE program, some background theory, an

improvement project done, and an operation facilitation work performed by the author

during the course of the attachment. The author was attached to TOS for his 10 weeks

Industrial Orientation, starting from 23th May 2011 to 29th July 2011.

2

2. Introduction of the Company

2.1 United Technologies Corporation

Turbine Overhaul Services (TOS) is under an industrial conglomerate known as the

United Technologies Corporation (UTC). UTC “researches, develops, and manufactures

high-technology products in numerous areas, including aircraft engines, helicopters,

heating and cooling, fuel cells, elevators and escalators, fire and security, and building

systems, among others.”[1] The core group of United Technologies companies was

founded in 1929 as United Aircraft and Transport Corporation through the merger of the

six different companies. United Aircraft later changed its name to United Technologies

on May 1, 1975, but has maintained its focus on the aerospace and building industries.

Today, UTC parents seven business units which are Pratt and Whitney, Otis, Carrier,

Hamilton Sundstrand, UTC Fire & Security, UTC Power and Sikorsky as shown in

Figure below.

Figure 1: Flow-chart showing the companies under UTC

3

Table 1 and Figure 2 below show the services provided by its business units, as well as

the break-down of the units’ business revenue for 2009.

Table 1: Overview of UTC’s seven business units

Figure 2: Pie-chart showing the units' individual revenue for 2009 [2]

4

2.2 Turbine Overhaul Services

Figure 3: TOS external facade

Turbine Overhaul Services Pte Ltd (TOS) is a joint venture between Pratt and Whitney

and Singapore Technology Aerospace Limited (ST Aerospace). As shown in Figure 4

below, Pratt and Whitney is the major shareholder holding 51% of TOS and ST

Aerospace with the remaining 49%. TOS provides repair and overhaul services for

aircraft jet engine turbine and compressor blades and vanes. Throughout the years of

operation, TOS has proved to be a reliable overhaul company producing high quality

products within the shortest Turn-Around-Time (TAT).

Other than the two major shareholders mentioned above, SIA Engineering Company also

invested in one of the facilities in TOS named as Turbine Coating Services (TCS) as

shown in Figure 4 below. Located within TOS’s facilities, TCS focuses on the

application of Thermal Barrier Coatings onto the products via the EBPVD (Electron

5

Beam Physical Vapour Deposition) process. The EBPVD facilities in TCS are the only

ones that can be found in the world other than in United States.

Figure 4: TOS major shareholders

2.2.1 Facilities Capabilities

Majority of its sales are derived from the turbine blades and vanes where its customers

come from all parts of the world. Some examples include Lufthansa, MTU, Volvo, Fiat

Avio and so on.

When the parts are delivered, they are differentiated by engine models. Each production

line starts from receiving, followed by inspection, repair and final checks before

shipment. There are more than 20 processes to be performed in each production line such

as milling, blending, blasting, grinding, polish, etc.

6

TOS focuses on four main parts of an aircraft engine as follows:

Turbine blade and vanes

High-pressure compressor blades

Industrial gas turbine

Turbine duct systems

Apart from its own P&W engines, TOS also services engine parts from other OEMs such

as General Electric, Rolls Royce, and International Aero Engines (IAE). Some of the

engines models which TOS repairs include:

PW4000 – P&W engine powering Boeing 747, 767 and Airbus A300

PW2000 – P&W engine powering Boeing 757 and Iiyushin IL-96

JT8D - P&W engine powering Boeing 727, 737 and Douglas DC-9

JT9D - P&W engine powering Boeing 747, Airbus A300 and McDonnell

Douglas DC-10

V2500 – IAE engine powering Airbus 320

CFM56 – CFM engine powering Boeing 737, Airbus A320 and A340

2.2.2 Organization Structure

TOS is made up of four buildings, each catering to different types of overhauling as

follows:

Building 1 : Special Process equipment & Machinery HF Furnace, Stripping, Coating

Building 2 : High Pressure Turbine blades/Vanes

Building 3 : Low Pressure Turbine Vanes

7

Building 4: Low pressure turbine blades and high pressure compressor blades

The department which the author was attached to was located in building 3. It consists of

5 storeys as follows:

Ground floor : Repair line for high pressure compressors

Level 1M : Tooling department

Level 2 : LPTV Offices & Shop floor

Level 2M : Chemical Metallurgical Lab

Level 3 : EH&S Office/Training Room/GSE (Global Service Engineering) Office

2.2.3 Low Pressure Turbine Vanes Departments

The author was attached to the Low Pressure Turbine Vanes (LPTV) process line. The

shop floor process line is divided into 4 cells, with each cell repairing different models of

LPTV. Apart from the machinists and operators at the shop floor, the LPTV office

consists of three departments as follows:

a. Operations Department (Headed by Operations Manager)

Each cell at the shop floor is managed by a cell leader who handles the overall

operations of the repair processes in their respective cells. Cell leaders ensure that

their cells are able to meet customers’ requirements and strive to be as efficient as

possible.

b. Engineering department (Headed by Principal Engineer)

The engineers in the Engineering Department work closely with the cell leaders in the

Operations Department to facilitate their operations in the technical aspect. The

8

engineers also develop and improve on existing repair methods to improve the

efficiency of each repair stages.

c. Special Process Department (Headed by Special Process Manager)

The engineers in the Special Process Department are in charge of developing and

qualifying new repair processes.

The author was attached to the Engineering Department in the LPTV office and details

regarding the job scope of this department will be discussed further in this report.

2.3 Organization Culture: ACE system

ACE is an important aspect of all companies under UTC. Understanding the nature of

ACE is necessary for the author to be immersed in the work culture of the company.

2.3.1 What is ACE?

ACE is a UTC company-wide strategy and stands for “Achieving Competitive

Excellence”. It is the approach to relentlessly improving the value that is delivered to the

customers and investors. It focuses on the drivers of customer and investor values - the

process and people who run it.

ACE involves all employees – leaders and associates alike – and it touches all

manufacturing, business and supporting processes that create and deliver customer value.

It seeks feedback on areas where the business, product or service has fallen short. ACE

paves a way to solve problems, make critical decisions, eliminate wastes and ensure a

safe working environment. Figure 5 below highlights how the ACE Cycle works within

UTC.

9

Processes Discrepancies

- Results vs. Goals- Waste

Quality & FlowClinics

Problem Solving

Process I mprovement and Waste Elimination

Decision Making

Customer and Employee Feedback



Problem Solving


Decision Making



Problem Solving


Decision Making


Problem Solving


Decision Making

CorrectiveActions

Processes

Problem Solving


BusinessStrategy

Decision Making- Results vs. Goals

- Waste

Problem Solving


Decision Making

BusinessGoalsResults

Customer

ValueMarket

Feedback

Requirements



Quality & FlowClinics

Problem Solving


Decision Making

Customer and Employee Feedback



Problem Solving


Decision Making



Problem Solving


Decision Making


Problem Solving


Decision Making

CorrectiveActions

Processes

Problem Solving


BusinessStrategy

Decision Making- Results vs. Goals

- Waste

Problem Solving


Decision Making

BusinessGoalsResults

Customer

ValueMarket

Feedback

Requirements

Figure 5: The ACE cycle

2.3.2 Ace Operating System

The ACE operating system consists of a set of tools that helps an organization identify

and solve problems; improve its processes and also to make strategic decisions. All the

tools supporting the ACE operating system as shown in Figure 6 below have training

modules and qualified instructors to teach staff. The details for the most commonly used

ACE tools – the 5S and QCPC can be found in Appendix A.

Figure 6: A breakdown of 8 of the essential ACE tools

10

2.4 Organization Mission and Vision

VISION

“To be the best airfoil repair organization in the world”

MISSION

“Excellence in turbine airfoil repair with the highest quality, most competitive prices and

fastest turn-around-time while ensuring TOS’s long term sustainable growth.”

11

3. Background Technical Information

Refer to Appendix B for information regarding compressor, turbine and transition ducts.

12

4. Improvement Project: Metal Tester

The author was attached to the engineering department which required him to perform

improvement projects for the repair process line. Improvement projects are ongoing and

practiced in conjunction with the daily routine jobs of an engineer, with the aim of

improving the efficiency and TAT of incoming products. Improvement projects are

usually not specifically laid out for engineers to work on, but developed by the engineers

themselves via a continuous self motivated analysis of the current situation and how

certain aspects can be improved. By continuously assessing the current practices in the

process line, engineers will be able to generate more ideas for increasing the efficiency

and develop improvement projects to analyse the feasibility of the new ideas.

In most improvement projects, scraped vanes/blades are used as development specimens

for engineers to perform testing. In order to prevent confusion between scraped parts and

production parts, a notch is machined on the development specimen as shown in Figure 7

below. Most of the development specimens as described in this report are scraped parts.

Figure 7: Notch indication on development specimen

13

The author was involved in several improvement projects during his attachment period.

However, the most prominent one is the ACROMAG Metal Tester project and shall be

discussed in the following section.

4.1 Introduction to ACROMAG Metal Tester

Figure 8: ACROMAG Metal Tester [3]

The ACROMAG metal tester as shown in Figure 8 above is a non destructive testing

equipment used to test for alloys of different compositions. It makes use of thermocouple

concept, the Seebeck Effect [4] whereby a temperature difference between two points

generates a potential difference, as shown in Figure 9 below.

Figure 9: Seebeck Effect [4]

14

As shown in Figure 10 below, there are two surface contacts- a cold surface plate and a

hot probe operated at 125 degree Celsius. The metal to be tested is to be placed on the

cold plate and the hot probe is to be in contact with the surface of the metal specimen to

be tested.

Figure 10: Testing a metal specimen

The magnitude of potential difference generated as shown on the meter depends on the

type of metal (type of composite or alloy) used as the conducting path, which is

illustrated in the schematic diagram in Figure 11.

Figure 11: Theory of ACROMAG Metal Tester

15

There are four scales of different ranges which are to be adjusted to obtain a suitable

reading – scales A, B, C and D as shown in Figure 12.

Figure 12: ACROMAG Metal Tester scales

4.2 Problems of current practice (coating tests)

Before a turbine blade/vane can undergo repair processes such as plasma spraying and

Turbofix® repair, it must be stripped off its previous plasma, Turbofix and protective

coatings. If the part is not fully stripped, further repair processes will not be as effective

as desired as new coating layers will not be well bonded to the part surface. The stripping

process involves milling and grinding and the depth of material removal can be

accurately computed. However, it is not possible to accurately predict the thickness of the

previous coating layers and hence unable to determine the accurate depth of cut to ensure

a total removal. This problem is usually solved by setting a larger depth of cut to remove

more of the surface, thus decreasing the probability of having any remaining coatings on

the surface. However, it poses another problem regarding the reparability of the

16

blade/vane in future. A larger depth of cut will result in excessive removal of parent

material and reduces its lifespan in terms of reparability for subsequent overhauls.

Another way of identifying the presence of coating is to use the Heat Tint Testing. The

presence of coating can be seen by the purplish colour portion on the vane after it has

undergone Heat Tint testing as shown in Figures 13 and 14 below. However, Heat Tint

Testing requires considerable amount of time and is inefficient (Refer to Annex C).

Figure 13: Vane before heat tint test

17

Figure 14: Vane after heat tint test

4.3 Overview and Scope of Project

Due to the limitations of the current practice, there is a need to develop new ways of

testing for the presence of coating layers. As part of process development process, the

author was tasked to investigate if the equipment can be used to test for different coating

materials and different coating thickness, since the concept behind the equipment

involves the fact that different materials produce different potential difference which in

turn produces different readings.

18

Theoretically, the equipment is expected to produce different readings for metals as

follows:

1. Metals with different coatings thickness, resulting in different electrical resistance

between the surface contact plate and the hot probe. A thicker coating is expected

to result in a larger electrical resistance and a lower meter reading (as shown in

Figure in the previous section).

2. Metals made of different parent materials with different resistivity, resulting in

different electrical resistance between the surface contact plate and the hot probe.

3. Different coating materials with different resistivity, resulting in different

electrical resistance between the surface contact plate and the hot probe.

However, some issues on its practicability needs to be considered, such as the following:

1.Reliability of the equipment manual such as the specified warm up time and

procedures. This is due to the fact that the equipment is old and the specified

information may not longer be applicable.

2.Sensitivity of the meter reading with respect to the thickness of coating and the type

of material used.

3.Time required performing the test and warm up time.

4.Repeatability of the test

a.Whether the meter is able to produce a consistent reading for the same

specimen.

b.Its sensitivity towards external factors, such as the positioning of the specimen

on the cold surface plate and the positioning angle of the hot probe.

19

After the author established the setup procedure for the Metal Tester, the author

conducted tests to determine if the Metal Tester is able to differentiate between a

Turbofix® treated area from a plasma built-up area, followed by its ability to differentiate

a surface coated with protective coating from one without. After obtaining positive

results from the tests, the author proceeded on to determine if the equipment is sensitive

enough to differentiate protective coating of different thickness.

4.4 Establishing Setup Procedure of Metal Tester

In order to ensure the reliability and accuracy of results, warm-up time of a testing

equipment must be established. Past experimental documentations indicated the warm-up

time to be 45 minutes, while the equipment manual stated it as 5 minutes [3]. Due to the

large discrepancy in the values, the author investigated the warm up time of the metal

tester for the hot probe to reach its steady temperature.

Using an ITD (Inner transition duct) of Engine A as the development specimen, the

author performed repeated tests and obtained readings at different time interval. The time

required for the meter to reach a steady reading was taken and was concluded to be 15

minutes. However in addition to the warm-up time, the author also discovered that the

Metal Tester requires a repeated imposed deflection of the meter needle out of the scale

range (as shown in Figure 15 below) for about 10 times so as to achieve a stable reading.

The author deduced that this was due to large friction in the needle contact which arose

from the old age of the equipment. This could be the reason why the past experimental

results showed such as long warm up time of 45 minutes as the meter needles are not yet

ready although the hot probe is already at its maximum steady temperature.

20

(Note: For more information regarding ITDs, refer to Appendix B.)

Figure 15: Maximum deflection above scale for warming up

Hence as part of the setup procedure, the author concluded that the equipment takes 15

minutes to warm up and should be tuned to the smallest scale C, followed by a minimum

of 10 repeated tapping of the hot probe on any specimens that can cause a maximum

needle deflection past the scale’s range. Further tests in the later part of this report will

reveal that an uncoated specimen is suitable for the warm up purpose.

21

4.5 Differentiating Plasma from Turbofix® Surface

4.5.1 Test Specimen:

The author was provided with an ITD specimen for Engine A as shown in Figures 16

below. The entire rear and trailing edge surface (refer to Figure 17) had undergone

Turbofix® treatment. As shown in Figure 18, an additional layer of plasma coating was

thickness of 0.005” was applied on half of the rear and trailing edge surface.

Figure 16: ITD (Engine A) Specimen

22

Figure 17: ITD (Engine A) terminologies

Figure 18: Plasma and Turbofix® surface

23

4.5.2 Purpose:

The author conducted tests on this specimen and to determine the feasibility of using the

metal tester to differentiate between a Turbofix® treated area and a plasma coated area.

4.5.3 Results and Conclusions:

Table 2: Turbofix® and Plasma surface readings

15 min 30 min 35 min 40 min Best reading

Turbofix® 26 27 25 26 26

Plasma 8 9 8 8 8

From the experiment, scale D is accepted to be the ideal range for this application as the

readings for both areas fall within an acceptable range. The plasma surface showed a

reading of 8 and the Turbofix® surface showed a reading of 26 as shown in Table above.

The distinct difference indicates that the metal tester is feasible for differentiating

between the two types of surfaces.

24

4.6 Differentiating coated from uncoated surface

4.6.1 Test Specimens:

Figure 19: ITD (Engine B) Specimen

The author was provided with three ITD specimens of Engine B and shall be named ITD-

Alpha, Beta and Charlie for reference in this report with their specifications as follows:

ITD-Alpha was a brand new production part which had a coating of known thickness.

The thickness value is not disclosed in this report to protect the interests of TOS.

25

ITD-Beta was coated but had a portion blended away for this test. The blended

portion was assumed to have no more coatings left on it, which was to be verified

from my test results concurrently.

ITD-Charlie was totally stripped off its coating and its parent material was exposed.

4.6.2 Purposes:

The primary purpose of this test was:

1. To determine if it was feasible to use the metal tester to differentiate between a coated

and an uncoated surface.

The secondary purposes were:

2. To determine if the blended surface on specimen ITD-Beta was fully blended and if

there is any more coatings left on it, based on the readings for the fully stripped

specimen ITD-Charlie.

3. To determine the consistency of the metal tester reading based on the entire coated

surface of specimen ITD-Alpha and the coated (non-blended) portion of specimen

ITD-Beta. If the metal tester is consistent and reliable, it should give the same reading

for both specimens.

26


Table 3: Coated and non-coated surface readings (ITD of Engine B)

ITD-Alpha ITD-Beta ITD-Charlie

Coated area Below scale Below scale N.A.

Non-coated area N.A. 26 27

From the experimental tests, the author obtained the results as shown in table above and

made his conclusion as follows:

1. The coated surface of ITD-Alpha gave a reading below the range of the scale D. This

was consistent with the readings for the coated (non-blended) portion of ITD-Beta

which was also below the range of scale D, indicating that the metal tester was

consistent.

2. The entire uncoated surface of ITD-Charlie gave a reading of 27, and the blended

portion of the specimen ITD-Beta also gave a similar reading of 26. This suggested

that the blended portion of the specimen ITD-Beta was fully stripped off its coatings,

and the metal tester was consistent.

Although the readings for coated surface were below the range of the scale and no

quantitative values were obtained, it is applicable as far as the application of

differentiating coated and un-coated surface is concerned. The distinct difference in

readings between the coated and uncoated surface shows that the equipment was feasible

to be used to differentiate between the two. However, if the metal tester was to be used to

27

differentiate between different thicknesses of coatings, a smaller scale would be needed

and further tests were required, which was conducted by the author in the section 4.8.

4.7 Investigating Repeatability of the Test

4.7.1 Test Specimen:

Figure 20: OTD (Engine B) Specimen

The author was provided with an OTD (Outer transition duct) specimen of Engine B

which had a layer of protective coating and a portion of it fully stripped as shown in

Figure 20 above. The difference in colour between the coated and uncoated surface is due

to the Heat Tint Test as discussed earlier in section 4.2. The parent material and the type

of protective coating of the OTD specimen is the same as that of the ITD specimens in

section 4.6. However, the thickness of the protective coating was unknown as the

specimen was a scraped part and no previous records of its repair were available.

28

4.7.2 Purposes:

The primary purpose of this test was to:

1. Investigate if the metal tester is specimen-shape dependent. Although they were made

from the same parent material, the readings for the uncoated portion of the OTD

might be different from that of the uncoated ITD in section 4.6 as they have different

shape.

The secondary purposes were to:

2. Investigate if the readings for the coated portion of OTD and the coated ITD

specimens are similar. Although they were coated with the same type of protective

coating, the readings between the two might vary since the coating thicknesses were

unknown. Furthermore, the different shapes between the OTD and ITD might result

in different reading which was to be verified as stated in the primary purpose.

3. Investigate if the readings were consistent with the trends of the results from previous

tests.


Table 4: Coated and non-coated surface readings (OTD of Engine B)

16 min 30 min 40 min Best reading

Coated area 2 1 2 2

Non-coated area 37 38 37 37

29

From the experimental tests, the author obtained the following results as shown in table 4

above and made his conclusions as follow:

1. The reading obtained from the coated surface was 2, while that of the uncoated

surface was 37. This further reinforced the trend from the previous tests which

suggested that a thicker coating layer would give a smaller meter reading.

2. The uncoated surface of OTD gave a reading of 37 as compared to the previous

reading of 26 for the ITD uncoated specimen. Given that the parent material of both

specimens were the same, the author deduced that the readings from the metal tester

were dependent on the shape of the specimen. Thus, in order to conduct a test on a

specimen, it is necessary to have a standard set of readings for a specimen of the same

model number with known specifications in order to make comparison with.

3. The coated surface of the OTD gave a reading of 2 as compared to the previous

reading of the coated ITD which was below the range of scale D. This discrepancy

might be simply due to the fact that both specimens are of different shape as deduced

above, or it could be due to the fact that the coating thickness of specimen of OTD is

thicker than that of the ITD.

30

4.8 Differentiating Different Thickness of Plasma Coating

Having obtained a positive result from the above tests, the author proceeded on to the

most important portion of the experiment – to determine if the Metal Tester could be used

to differentiate different thickness of coating on a specimen. The outcome of this

experiment would determine if the Metal Tester can be utilised to facilitate the repair

process in TOS. However, due to the short attachment period of 10 weeks, this project

was not completed and was to be continued by future students attached to TOS.

4.8.1 Analysis of specimens:

Due to the limited number of development specimens available, the author was provided

with only two scraped ITDs of Engine A. Unlike the previous few experiments, the two

specimens available for this test required further processing before they could be used

due to the following reasons:

i. Both specimens do not have any protective coating. Both specimens had

undergone Turbofix® repair in their previous overhaul at TOS which had to be

removed before the author could apply coating layers on them.

ii. To suit the purpose of this test, there must be sufficient number of surfaces with a

variety of coating thickness and coating materials (plasma and protective coating)

so as to establish a useful set of result. Thus, the author must divide each

specimen into sections with different coating thickness and different coating

materials.

31

In order to have sufficient amount of space to perform tests without compromising the

range of coating thickness to be tested, each specimen was to be divided into three

sections. The first specimen were to be coated with plasma as shown in Figure below,

and the second specimen were to be coated with protective coating instead.

Figure 21: Sectioned rear face of ITD (Engine A)

\

Before the plasma coating could be applied on the rear and trailing edge surface, the old

Turbofix® layer must be removed by performing grinding on the entire rear and trailing

edge surface. Due to the nature and limitation of the grinding machinery, the portion with

the thinnest layer of plasma must be prepared first so that subsequent grinding on the

other two thicker portions will not affect the thinner portion as shown in Figure above.

32

Hence, plasma should be applied onto the thinnest section first and to be grinded to the

required thickness of X inches as shown in Figure above. Subsequently, plasma was to be

applied onto the mid section and grinded to the desired thickness of Y inches, and the

same procedure to be applied for the coating of the last section with plasma thickness of

Z inches.

Figure 22 below shows the preparation stages of the specimens for each section. In step 2

and 4, the measurement readings would enable the author to determine the thickness of

plasma coating applied onto the rear surface in step 3. Steps 4 and 5 would enable the

author to ensure that the final thickness of the plasma coating is of the correct thickness –

“X” inches, “Y” inches and “Z” inches respectively for each section.

Figure 22: Preparation stages of specimen

33

1. Grinding:To remove old Turbofix® surface

3. Plasma coating:Applied on one section of rear surface (Thinnest section first)

2. Dimension measurement:Obtain dimensions before coating. Vernier Calipers Dial indicator

4. Dimension measurement:Obtain dimensions after coating. Vernier Calipers Dial indicator

5. Grinding:To desired plasma coating thickness

6. Dimension measurement:Confirm thickness of plasma coating. Vernier Calipers Dial indicator

4.8.2 Preparation of Specimens:

As the author had not undergone trainings for the operation of the machineries involved

in this project, the grinding and plasma spraying processes as shown in steps 1, 3 and 5 in

Figure above were performed by the machinists instead. The author measured the

dimensions of the rear surface of the specimen as shown in Figure 23 below.

Figure 23: Dimension to be taken

The author used two measuring devices - vernier callipers and Dial Indicator to measure

the dimensions. Figure 24 below shows a picture of the zeroing process of the Dial

Indicator. Vernier callipers have a precision of 0.001” while the Dial Indicator has a

precision of up to 0.0001”.

34

Figure 24: Zeroing of a Dial Indicator

Although the Dial Indicator has a higher precision, the measurement process required the

specimen to be installed onto a fixture (as shown in Figure 25 below) and the process of

installation is prone to human error. The repeatability of the Dial Indicator measurement

is low if the person installing the specimen onto the fixture is inexperienced. Hence, the

author decided to record down the vernier callipers reading as well in case the Dial

Indicator readings were inaccurate. This was especially important since each machining

steps 1, 3 and 5 were irreversible.

Figure 25: ITD (A) installed on Fixture for Dial Indicator measurement

35

Figures 26 and 27 below show the picture of the specimen surface after stages 1 and 3

respectively. Due to the short attachment period, the author did not manage to finish this

project and stopped at stage 4 after taking the dimensions of the specimen shown in

Figure below.

Figure 26: Specimen after blending

Figure 27: Specimen with plasma coating (X inches thickness) on first section

36

4.9 Conclusion of experiment

The specific readings obtained for each duct model with different coating surfaces is

summarised in Table in the following section. Although the author did not manage to

complete the entire project in the attachment period, he managed establish the feasibility

of using the Metal Tester to identify coated and non coated surfaces for three different

duct models. The results shown in Table below as well as the setup procedure established

by the author in section would be used as a reference guide for future analysis in

continuation of the project by future students attached to TOS.

4.9.1 Summary of results

Table 5: Summary of results for ACROMAG Metal Tester Project

Parent material Turbofix® Plasma Protective Coating

Engine A ITD NA 26 8 Below scale

Engine B ITD 26-27 NA NA Below scale

Engine B OTD 37 NA NA 2

4.9.2 Suggestions for Further Studies

The author proposed the following tests for further study:

37

a. Continuation in the project where the author left off and establish the data as follows:

Table 6: Incomplete Table for future continuation

The results in Table 6 will determine if the Metal Tester was sensitive enough to

differentiate between different coating thicknesses. Should a positive result be

obtained, the author proposed that further tests be conducted as described in part b.

b. Examining the linearity of the coating thickness with the Metal Tester readings for

each specimen model and each type of coating. As the results obtained in Table 6 has

only three different thickness for each coatings as variable, the author proposed that

more tests should be conducted with more variables to establish a more accurate

relationship. If these parameters show a linear relationship, a simple linear graph can

be established (as illustrated in Figure 28 below) and any unknown coating thickness

can be obtained from the Metal Tester readings. However, if there is no linearity

38

Plasma Coating ITD (Engine A) Protective Coating ITD (Engine A)

X inches X inches

Y inches Y inches

Z inches Z inches

relationship, a table (as illustrated in Table 7 below) is required to be compiled from

many repeated tests with different coating thickness, coating type and specimen

model as parameters. Coating thickness can then be obtained by linear interpolation

method from the table given its Metal Tester reading.

Figure 28: Illustration of graph for future continuation (linear relationship)

39

Table 7: Illustration of Table for future continuation (non linear relationship)

5. Operation Facilitation: Preparation of Operation Instruction

Documents

As part of the job scope of an engineer in the Engineering Department, the author

participated by facilitating the repair operations in the process line. One of them was to

prepare Operation Instruction documents.

An Operation Instruction is a document prepared by the engineers to assist the process

line operators in their work. The technical information inside the Operation Instruction is

based on the Engine Manuals provided by the OEM and approved by the relevant

aviation authorities. However, the technical information provided from the Engine

Manual is described in words. When it comes to practical application, this information is

not user friendly and the operators need to use their own judgement in decision making.

As a result, there is a risk of double standard practice especially when it comes to

40

deciding whether to scrap or to repair the vane/blade. The information in the Operation

Instructions is much more simplified and user-friendly as compared to the Engine Manual

so as to ensure that process line operators can understand them.

The author was involved in the entire generation process of an Operation Instruction.

Operation instructions were first drafted into Word format, with the technical information

provided in the Engine Manual for a specific model of turbine vane/blade undergoing a

specific repair process. In addition to the technical details, enhancements such as visual

aids in pictorial or schematic forms were added in relevant portions of the Operation

Instructions.

After the draft was completed, they were uploaded onto the company database called

“SOLUMINA”. The author was involved in uploading of new Operation Instructions

onto SOLUMINA as well as updating existing ones.

5.1 Engine Manual

The engine technical data provides technical details on all the parts in a specific engine

model, such as low/high pressure turbine parts, turbine exhaust case parts, gearbox parts,

low/high pressure compressor parts and so on. Technical data includes quantitative and

qualitative information such as operation theory of the part, disassembly and assembly

instructions of the parts, cleaning instructions, inspection guidelines and repair

instructions. These technical data can be accessed by all other companies under Pratt and

Whitney via their intranet as well. However, as far as TOS is concerned, the most

commonly accessed data are those of turbine and compressor. During the attachment

41

period in TOS, the author created Operation Instructions for process line inspectors and

he mainly accessed the repair instructions and inspection guidelines in the Engine

Manual.

The inspection guidelines in the Engine Manual provide technical details on the

serviceable and repairable limits based on different types of damages (sulfidation, wear,

cracks etc) and different locations (leading/trailing edge of airfoil, on shroud etc). The

serviceable and repairable limits are much stricter for high stress areas and damage prone

regions. For example, the crack size limits for leading edge will tend to be stricter than

that for the trailing edge, due to the fact that the leading edge tends to suffer damages at a

faster rate than the trailing edge. If the damage on the incoming part is within serviceable

limit as specified on the technical data, it does not require repair for that particular

damage and the repair processes for that damage can be skipped. Similarly, if the damage

as beyond the repairable limits as specified on the technical data, the part cannot be

repaired to the serviceable conditions and will be sent to the scrap stage in the process

line. The inspection guidelines improve the efficiency of the production in TOS as it

saves valuable time by filtering out parts which cannot be repaired and omits processes

that can be skipped.

5.2 Drafting of Operation Instructions

A typical Operation Instruction contains the following sections: Objectives of the

process, Equipments required, Drawings, Acceptable limits, Procedures and reference.

42

The technical information from the Engine Manual is the building block and forms the

skeleton of the entire Operation Instructions.

Under the Drawings section, the author made improvements to the technical information

by creating visual aids for frontline inspectors as well as machinists to assist them in their

work. In the process of preparing visual aids, photographs of production parts showing

the damaged areas need to be taken. To perform this task, the author must be familiar

with the information provided in the Engine manual so as to identify the right specimen

to be photographed and used as an illustration. This is especially so when the Engine

Manual only provides qualitative description, whereby the author must be able to

exercise correct judgement.

5.2.1 Visual Aids for Frontline Inspectors

The job scope of frontline inspectors is to inspect incoming vanes/blades and separate the

repairable and un-repairable ones. Inspectors also must identify what repair processes are

to be performed for each part based on the degree of defect. Visual aids provide visual

guides for inspectors to decide if the product needs certain processing, or whether the

process can be skipped as the damage falls within the limit specified in the technical data.

The specimens to be photographed were obtained from the frontline inspection stage.

Some of the visual aids prepared by the author for frontline inspectors are shown in

Figures 29 and 30 below.

43

Figure 29: Visual Aids for Inspectors (1)

Figure 30: Visual Aids for Inspectors (2)

44

An example of simplification of technical data can be illustrated in Figures 31 and 32

below. Figure 31 shows the complicated schematic of a turbine vane with all its parts

labelled obtained from the Engine Manual. The complicated schematic is simplified and

split into its respective area as shown in Figure 32 in the Operation Instructions. The

serviceable and repairable limits pertaining to that area is compiled beside the simplified

schematic, making it much more user-friendly.

Figure 31: Complicated schematic from Engine Manual

45

Figure 32: Simplified schematic in Operation Instruction document

46

5.2.2 Visual aids for Machinists

The job scope of machinists is to ensure that the part under repair in his station fulfils the

criteria stated on the Engine Manual. Criteria include qualitative and quantitative

dimensions of the part after the repair in his station is completed. The author prepared

visual aids for the machinists performing blending repair as shown in Figure 33 below.

Figure 33: Visual Aids for Machinists

47

5.3 SOLUMINA Database

Figure 34: SOLUMINA database user-interface

5.3.1 Introduction to SOLUMINA

With the introduction of the new SOLUMINA database a few years back, all previous

Operation Instructions and information has to be transferred into the database.

Previously, all information was saved as individual Microsoft word files for each turbine

vanes/blades. With the new SOLUMINA software, all information for different

vanes/blades can be accessed within the database itself. Operation Instructions for each

turbine vanes or blades for each stage of repair can be obtained from SOLUMINA.

Although this makes it more convenient for one to search for information, the process of

uploading the entire system over to SOLUMINA takes time and is still in progress in

TOS. The Operation Instructions for some of the vanes/blades are still undergoing

transfer due to the tedious process of converting the word format to that in SOLUMINA.

48

5.3.2 Uploading of Operation Instructions onto SOLUMINA

After the Operation Instruction draft was finalised, the Operation Instruction could be

uploaded onto the SOLUMINA database in a standardised format. SOLUMINA contains

Operation Instructions used in TOS which are categorised into their repair stations. The

word “Oper” and followed by an operation number is used to label every Operation

Instructions for easy reference.

After the relevant information was uploaded onto SOLUMINA, the system will present

the Operation Instructions in a standard format as illustrated in Figure 35 below. Before

the Operation Instructions could be finalised and published, it must obtain approval from

the Quality Assurance (QA) engineers.

As a product undergo different stages of repair in TOS, a traveller will be attached to the

product and its past completed repair stages were indicated on the traveller. Operators in

the repair line are required to look through the Operation Instructions with reference to

the traveller before beginning the repair. Thus, it is essential to update the Operation

Instructions on SOLUMINA and ensure that the updated hardcopy is made available to

the operators and inspectors in the process line.

49

Figure 35: Standard Format of Operation Instruction Document

50

6. Conclusion and Author’s Reflections

These 10 weeks of attachment in TOS has been an eye-opening experience where the

theories taught in school had been complemented by this author’s participation in projects

and assignments. Many hard skills were sharpened during the attachment and the author

had learnt to relate theoretical engineering concepts into real life engineering. Some

examples are as follows:

(Note: Some of the following were not discussed in this report but the details were

covered in the author’s Industrial Orientation Logbook.)

a. Application of electrical circuit concept on the ACROMAG Metal Tester, which

were learnt in the modules AE2004 (Circuits and electronics) and FE1002

(Physics2).

b. Applying what was learnt from the modules AE2003 (Aerodynamics1) and AE3005

(Aerodynamics2), the author was able to better appreciate why the Engine Manual

stated much stricter operational limit criteria on the leading edge than on the trailing

edge.

c. Applying what was learnt from the module AE2008 (Mechanics of Materials), the

author was able to appreciate why the curvature radius on a turbine vane must not be

too small due to the concept of stress concentration.

d. Theories of machining processes and non-destructive testing, such as Fluorescent

Penetration Inspection (FPI), ultrasonic testing, grinding and milling were further

reinforced during the attachment. These theories were learnt in the modules AE2011

51

(Introduction to Aircraft Design and manufacturing) and AE2009 (Aerospace

Materials).

e. Applying what was learnt in the module AE3006 (Aircraft propulsion), the author

was able to apply the concept of turbine efficiency and understand why the cooling

holes of turbine vanes should not be too large.

f. From the laboratory skills learnt from all the laboratory sessions in NTU, the author

was able to apply and improve on his analytical and interpretation skills on the Metal

Tester project. From the analysis of the results obtained, the author developed further

tests to continue the investigation.

Other than the hard skills benefited from the attachment, the author has picked up many

soft skills which could not be learnt from books. Some of them are as follows:

i. Interpersonal and communication skills

a. The author was required to collaborate with the machine operators in the process

of developing test specimens. Compromises had to be made due to time

constraints for both parties and interpersonal skills were required.

b. The author had to place himself in the position of others and examine if the

Operation Instructions could be understood by the process line operators,

requiring good communication skills which were learnt in the course module

HW110 (Effective Communication).

52

ii. Human management skills

a. The author observed how his supervisors, cell leaders and managers handle their

subordinates in their daily work. The skills of maintaining a balance between

work productivity and creating a joyful working environment is crucial in human

management context. The skills learnt from the course module AE4008 (Human

Resource Management) proved to be useful in aiding the author understand the

concept of managers and leaders and how to combine both roles into one.

iii. Positive learning attitude

Through the attachment period, the author came to realise the importance of

maintaining a positive attitude in the working environment. A positive learning

attitude is the fundamental attribute a student should adopt as it has a direct

impact on the working attitude, which in turn impacts on the work performance

and subsequently the career advancement.

Every tasks assigned to the author had some learning points waiting to be picked

up. A person without a positive mindset will fail to capture the learning points and

allow learning opportunities to slip by. The author has learnt to be inquisitive and

seek for answers from his supervisors, colleagues, and shop floor machinists by

asking questions. By questioning the uncertainties one face in life and seek

industriously for answers, the boundaries of self improvement become limitless.

A positive learning attitude will also serve as a driving force for one to undertake

works beyond his line of duty. A pro-active working attitude is the basic

requirement for excellence in work performance and to succeed in life.

53

Overall, the initial learning objectives set for this attachment have been met. This author

gained a better understanding of how the aerospace industry operates and TOS’s ways

and means of remaining competitive in the industry. This author also learnt more about

what it takes to be a successful aerospace engineer just like his mentors who had guided

him. This author also learnt more about the techniques used to inspect and repair the

engines, the machines that are involved and the way they operate.

In summary, the industrial attachment with TOS had provided the author with a good

introduction to the complex aerospace industry. The opportunities given to learn through

the handling of aircraft engine components have indeed been an honor and privilege, as it

proved to enhance the theoretical knowledge learnt in the classroom. This author will

definitely cherish the 10 weeks spent here in TOS as the most enriching and enjoyable

experience in the course of study in NTU.

54

7. References

1. Wikipedia. (2010). United Technologies Corporation . Retrieved 12 July, 2011, from

http://en.wikipedia.org/wiki/United_Technologies_Corporation

2. United Technologies Corporation (UTC). (2010). About UTC- History. Retrieved 12 July,

2011, from http://www.utc.com/About+UTC/History

3. ACROMAG Inc. (2010). 1100 Series Metal Tester. Retrieved 12 July, 2011, from

http://www.acromag.com/sites/default/files/MetalTester_8400534.pdf

4. The Encyclopaedia of Alternative Energy and Sustainable Living (2006). Seebeck effect.

Retrieved 19 July, 2011, from

http://www.daviddarling.info/encyclopedia/S/AE_Seebeck_effect.html

5. Farlex. (2011). By-pass ratio. Retrieved 20 July, 2011, from

http://www.thefreedictionary.com/bypass+ratio

6. Wikipedia. (2008). File:Turbofan operation lbp.svg. Retrieved 28th July, 2011, from

http://en.wikipedia.org/wiki/File:Turbofan_operation_lbp.svg

7. Patent Genius. (1980). Method For Preventing The Deposition of a Coating on a

Substrate. Retrieved 28th July, 2011, from

http://osdir.com/patents/Coating-processes/Method-protecting-local-area-component-

07083824.html

55

8. British Stainless Steel Association. (2010). Heat Tint (Temper) Colours on Stainless Steel

Surfaces Heated in Air. Retrieved 28th July, 2011, from

http://www.bssa.org.uk/topics.php?article=140

56

APPENDIX A – Ace Tools

1. 5S + 1 (Commonly known as 6s)

5S + 1, or 6S, is a methodology for organizing, cleaning, developing and sustaining a

productive work environment. The foundation of a quality mindset starts with 6S:

Sort: Eliminate what is not needed for your daily business and operations processes.

This includes clearing your folders on the computer to remove unnecessary e-mails and

removing unwanted documents and files from your table.

Straighten: Organize what remains, in a neat and systematic fashion. Every item has its

place in your work-area; tools should be in the tool-box and documents should be in clearly-

marked files. Figure (A – 1) below shows how the second ‘S’ of 6S is applied.

Figure A - 1: Examples of “Straighten” concept in practice

A1

Shine: Clean the work area. Keep it tidy by removing the dust and dirt, and cleaning the

surfaces regularly. Ensure that all items are functional.

Standardize: Schedule the cleaning and maintenance of the workplace, and maintain the

standards set.

Sustain: Make 6S a way of life and inculcate the good habit of applying 6S to the workplace

and home.

Safety: It is everyone’s responsibility to ensure a safe working environment. Posters, such as

the one in Figure (A – 2), are hung around the workplace to remind everyone.

Figure A - 2: Example of a poster reminding everyone on the 5 Cardinal Rules of Safety

A2

Figure A - 3: 6S logo

2. Quality Clinic Process Charts

Quality Clinic Process Charts (QCPC) is a simple tool that is used to analyze a process of

quality improvement opportunities and process inefficiencies known as “turn backs”. The

steps taken to implement QCPC are shown in Figure (A – 4).

Figure A - 4: The 5 Steps for QCPC implementation

A3

INITIATE QCPC

Every employee, including the QCPC team members, must be inculcated with the ITO

Philosophy: “Create a trusting environment that encourages participation.” (Yuzuro Ito is the

founder of ITO University in Japan and has his quality philosophies adopted by UTC.) They

must treat all turn backs as “golden nuggets” of information and opportunities. The senior

management must encourage and reward participation, along with not punishing employees, for

acknowledging problems. This in turn will invite enthusiastic feedback. Everyone, from the

General Manager to the intern, has to practice a quality-first mindset.

All processes are determined by the SIPOC rule (Supplier, Inputs, Process, Outputs,

Customers).This is an organized way of defining processes that are being carried out in a

particular cell. It identifies who are the suppliers to this cell, what inputs are required from them,

what processes go on in the cells, the output from these cells and finally who are the customers

of these processes. An example of the SIPOC chart is shown below.

A4

Figure A - 5: An example of a typical SIPOC chart

It is also important to define “turn-backs”, as shown below.

Figure A - 6: Definition of “turn-backs”

A5

Each turn-back is counted every time it occurs. A cross-functional team with knowledge of the

various processes is selected as it will have the necessary skills to analyse the problems from

various angles. This will thus decrease the risks of not identifying all weak points and perhaps

not even being able to solve the problem.

The process and procedures of QCPC system must be clearly disseminated to all stakeholders

(employees, customers and shareholders) as everyone is responsible. Everyone must treasure

problems as learning potentials rather than shun it and not change for the better.

COLLECT & SORT DATA

The local intranet is used, which is a good data collection and tracking methodology. The

system below also enables sorting of data at each stage of the process.

Figure A - 7: One possible system of recording turn-backs

A6

ANALYSE DATA

Normally, when a QCPC programme is started, turn-backs recorded will increase initially, and

will decrease in number when processes improve.

Figure A - 8: Graph showing the number of turn-backs recorded against duration of the QCPC programme

It is also important to choose the correct data-analysis tool shown in Figure (A – 9) below, which

depends on what types of data are obtained, and the objectives of the QCPC programme.

Figure A - 9: different types of data-analysis tools available for QCPC

A7

When analysing the data, the QCPC team must not solely focus on the quantity of turn-backs that

occur in a particular area, but must also consider areas whereby processes take an abnormally

long time to complete - even though their turn-backs are low. Here, a thorough investigation will

be conducted and results will be submitted to management for rectifying purposes.

Figure A - 10: Bar-chart showing how many turn-backs, and the time lost

If the frequencies of process steps are conducted differently, the turn-back ratio will be used so

that the performance of each process step with regards to its turn-backs will be normalized to

account for the frequency at which the step is conducted. The following steps are taken to

calculate the total turn-back ratio:

1. Count the total turn-backs per process step

2. Count the number of pieces (i.e. Engines) that run through a process step

A8

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3. Remember : re-work is considered a turn-back, not an additional engine count

4. Calculate using the formulae :

5. Calculate total turn-back ratio, which is the sum of all process turn back ratios.

Therefore, if a certain step, such as the balancing-of-turbine-blades process, experiences a

30% turn back ratio, it means that 30 % of the pieces/components that go through this step

will experience a turn back.

PRIORITIZING PROJECT LIST

The company must make sure that all resources are properly directed when engaging QCPC.

Realistic goals must be set in the QCPC project. For example, the QCPC team may target for

a 50 % reduction in 3 months and 90% reduction in turn-backs in 6 months.

DOCUMENT SUCCESS

When a design or process change has been implemented, it must be ensured that:

- The problem is mistake-proofed.

- The QCPC trend chart shows no recurrences.

- There are no adverse effects on other products or processes.

- An update on the Standard Work Documentation must be done.

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Turnbacks at Process StepPieces Into Process Step

x 100 = Turnback Ratio (%)

Figure A - 11: A QCPC trend chart before and after implementation

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APPENDIX B – Compressor, Turbine and Transition Ducts

1. Introduction of Aircraft Compressor and Turbine

Figure B - 1: Jet engine [6]

Figure above shows a typical schematic of a turbo-propeller engine. Air enters the engine from

the propeller fan and only part of it enters the compressor. The by-pass ratio refers to the mass

flow rate of air drawn in by the fan by-passing the compressor to the mass flow rate passing

through the compressor. [5]

The function of the compressor is to increase the pressure of the incoming air and should not

experience any increase in temperature in an ideal situation. The compressor is powered by the

B1

http://upload.wikimedia.org/wikipedia/commons/7/77/Turbofan_operation_lbp.svg

energy harvested from the turbine. As shown in the Figure above, the high pressure section of the

compressor is nearer towards the combustion chamber and the airfoils used are of smaller wing

span as compared to the low pressure side.

Similarly for turbine, the high pressure turbine blades and vanes are of longer wingspan as

compared to low pressure blades and vanes. However, the high pressure portion of the turbine is

at the in-coming portion as compared to that of the compressor which is at the exit portion of the

compressor.

2. Transition Ducts

Transition ducts are found at the entrance and exit between each stages of the turbine blades and

vanes. Transition ducts are separated into inner and outer portion based on their position in the

radial direction. Ducts direct the flow of air from the previous stage to the next and are equally

prone to similar damages as that of vanes and blades due to the similar conditions experienced

during operation.

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APPENDIX C – Heat Tint Testing

Heat tint testing is a process used to detect the presence of foreign materials such as coatings on

the surface of a parent metal.

Heat tint involves exposing the material to high temperature in the presence of atmospheric gas

[7].

In the heating process, the high temperature causes the metallic surface to undergo oxidation

which results in a colour change. As the oxide layer thickens with respect to the time exposed to

heat, the colour change becomes more extensive. The degree and extend of colour change will

depend on the time taken in the heat treatment, as well as the oxidation resistance of the metallic

surface. Hence, different metallic surface will result in different colour change after the heat tint

test. However, the colour changes can only prove that there is different type of metallic surface

due to the colour contrast, and is unable to identify specifically what metal is present [8].

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