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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
Processes Discrepancies
- Results vs. Goals- Waste
Problem Solving
Process I mprovement and Waste Elimination
Decision Making
Processes Discrepancies
- Results vs. Goals- Waste
Problem Solving
Process I mprovement and Waste Elimination
Decision Making
Processes Discrepancies
Problem Solving
Process I mprovement and Waste Elimination
Decision Making
CorrectiveActions
Processes
Problem Solving
Process I mprovement and Waste Elimination
BusinessStrategy
Decision Making- Results vs. Goals
- Waste
Problem Solving
Process I mprovement and Waste Elimination
Decision Making
BusinessGoalsResults
Customer
ValueMarket
Feedback
Requirements
Processes Discrepancies
- Results vs. Goals- Waste
Quality & FlowClinics
Problem Solving
Process I mprovement and Waste Elimination
Decision Making
Customer and Employee Feedback
Processes Discrepancies
- Results vs. Goals- Waste
Problem Solving
Process I mprovement and Waste Elimination
Decision Making
Processes Discrepancies
- Results vs. Goals- Waste
Problem Solving
Process I mprovement and Waste Elimination
Decision Making
Processes Discrepancies
Problem Solving
Process I mprovement and Waste Elimination
Decision Making
CorrectiveActions
Processes
Problem Solving
Process I mprovement and Waste Elimination
BusinessStrategy
Decision Making- Results vs. Goals
- Waste
Problem Solving
Process I mprovement and Waste Elimination
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
4.6.3 Results and Conclusions:
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.
4.7.3 Results and Conclusions:
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
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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
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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