shruti project report - intricacies in fabrication with ti
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Intricacies in Fabrication with Titanium
Shruti Jayeshbhai Shah
Production Engineering Department
Dwarkadas J. Sanghvi College of Engineering,Vile Parle (west),
Mumbai -400058
2015-16
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Intricacies in Fabrication with Titanium
Submitted in partial fulfilment of the requirements of the degree of
(Bachelor of Engineering)
by
Shruti Jayeshbhai Shah
Sap Id. 60012120022
Project Guide:
Prof. E Narayanan
Production Engineering Department
Dwarkadas J. Sanghvi College of Engineering,Vile Parle (west),
Mumbai -400058
2015-16
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CERTIFICATE
This is to certify that the project entitled Intricacies in Fabrication with Titanium
is a bonafide work of Shruti Jayeshbhai Shah (60012120022) submitted to the
University of Mumbai in partial fulfilment of the requirement for the award of the degree of
Bachelor of Engineering in Production Engineering.
Internal Guide
(Prof. E Narayanan)
External Guide
(Mr. Rakesh Deodhar)
Principal and Head of Department
(Dr. Hari Vasudevan)
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Project Report Approval for B. E.
This project report entitled Intricacies in Fabrication with Titaniumby
Shruti Jayeshbhai Shah is approved for the degree of Production
Engineering.
Examiners 1.--------------------------------------------
2.--------------------------------------------
Date:
Place:
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Declaration
I declare that this written submission represents my ideas in my own words
and where others' ideas or words have been included, i have adequately cited
and referenced the original sources. i also declare that i have adhered to all
principles of academic honesty and integrity and have not misrepresented or
fabricated or falsified any idea/data/fact/source in my submission. I understand
that any violation of the above will be cause for disciplinary action by the
Institute and can also evoke penal action from the sources which have thus not
been properly cited or from whom proper permission has not been taken when
needed.
-----------------------------------------
(Signature of student)
-----------------------------------------
(Name of student and Sap Id.)
Date:
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No Objection Certificate
This to certify that Shruti Jayeshbhai Shah, Degree student of Production
Engineering of Dwarkadas J. Sanghvi College of Engineering, Vile Parle (W), Mumbai-
400056 has satisfactorily completed her Inplant trainingfrom 01/07/2015 to 31/12/2015
at our Fertilizers, Petrochemicals, Gasifier and Power Plant Department of Heavy
Engineering Independent Company (HEIC) at M/s. Larsen & Toubro Ltd., Powai.
She has successfully carried out all the responsibilities allotted to her.
She has been allowed to include the documents, data and sketches for which we
have no objection. We sincerely appreciate all efforts made by her and wish her success in
future endeavours.
___________________________ ________________________________
Mr. Alok Tanawade Mr. Rakesh Deodhar
(Manager- PMG, FPGP) ( DGM- Project Management Group, FPGP )
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Acknowledgement
It is great pleasure to present this report, which will vouch for prolific and
invaluable training at M/s LARSEN AND TOUBRO. I consider it an honoured privilege to
have undergone Inplant training in a highly reputed and diversified company like M/s Larsen
& Toubro Ltd. The training period of 24 weeks besides enhancing my scope of thinking, has
enriched me with invaluable experience of the industrial culture of the highest repute.
I would like to thank Mrs. Pooja Acharekar (HR-CORPORATE) and Mrs.
Nishita Boricha(HR-HEIC) for giving me this unique opportunity to get trained in such an
advanced department and enhance my training knowledge.
I am deeply grateful to Mr. Rakesh Deodhar my organization training
supervisor, for providing me with freedom and encouragement to participate in various
projects involving production planning and productivity improvement analysis.
I would also thank Mr. Alok Tanawade, Mr. Vijaykumar Yadav and
Ms. Nishita Palkar who zealously guided me at every juncture of need. Their altruistic co-
operation, help and advice were found to be invaluable in most crucial stages of my training. I
will remember their advice and ideas for future progress.
My special thanks to Dr. Hari Vasudevan (Principal and HOD-Production
Engineering Department) for giving me a chance to learn and enhance my knowledge. I
would like to thank my college supervisor, Mr. E Narayanan for his valuable advices,
motivation and engender in me an impetus for innovations and a quest for learning more,
whose invaluable guidance and timely suggestion and constructive encouragement inspired
me to complete my training.
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Abstract
The project titled Intricacies in Fabrication with Titanium accounts for the successful
full-time Industrial training for a period of six months towards a partial fulfilment of the
degree of B.E. Production Engineering. Sequentially the work introduces company profile,
Titanium heat exchanger and its parts, Fabrication with Titanium, Welding and Forming
process.
It is then followed by description of Welding with Titanium, Its precaution, procedure and
cleanliness while welding Titanium, Weld colour specification, Tube to tube sheet welding,
modification in tungsten electrode as per specific requirement, Titanium welding specification
and Arc Voltage Controller (AVC) machine.
The other half is based on Nozzle Fabrication in one piece from Titanium plate without any
crack formation, buckling and misalignment. It is based on Fabrication technique, forming die
and designing a new Guiding fixture. It also contains the problem faced while forming
nozzles earlier in one piece, reasons of that problem and limitations of the current used
method (Nozzle forming in two pieces). This project includes solution for this method by
using a guiding fixture.
Finally, the report concludes displaying the improvements achieved by the fabrication process
and design modifications and replacing the older method by the new designed fixture, and the
desired results were achieved successfully. Also the Work carried out, initiated and executed
by me while working in Larsen & Toubro Heavy Engineering is concluded in this report.
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TABLE OF CONTENTS
SUBJECT PAGE NO
CERTIFICATE ..... i
PROJECT APPROVAL FOR BE .. ii
DECLARATION .. iii
NO OBJECTION CERTIFICATE iv
ACKNOWLEDGMENT .. v
ABSTRACT . vi
CHAPTERS PAGE NO
CHAPTER 1 INTRODUCTION ....
1.1 About Larsen and Toubro 01
1.1.1 Business Functions of L&T 02
1.2 Heavy Engineering Division (HED) ... 03
1.2.1 Fertilizers, Petrochemicals and Heat Exchangers Equipment department 03
1.2.2 Functions of business units of HED .. 04
1.3 Project Management Group (PMG) 04
1.3.1 Characteristics of a Project 05
1.3.2 Project Organization Structure .. 05
1.3.3 Need for PMG 06
1.3.4 Functions of PMG .. 06
1.3.5 Systems Used . 07
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CHAPTER 2 TITANIUM HEAT EXCHANGER (ZADCO) ..
2.1 Introduction to the End User of the Project .. 08
2.2 L&Ts Contribution to the Project 09
2.3 Specific benefits of Titanium . 09
2.3.1 Why Titanium Heat Exchangers? 12
2.4 Heat Exchanger . 12
2.4.1 Types of Heat Exchanger . 13
2.4.2 Parts used in Heat Exchanger . 14
2.4.3 Shell and tube Heat Exchanger .. 15
CHAPTER 3 FABRICATION WITH TITANIUM ..
3.1 Introduction to the Fabrication with Titanium .. 18
3.2 Warm Forming 19
3.2.1 Spring Back 19
3.2.2 Description warm forming with Ti channel nozzle plates . 20
3.2.3 Care to be taken during warm forming with Ti nozzle plates .. 21
3.2.4 Forming Defects . 21
PROJECT I
CHAPTER 4 INTRICACY IN WELDING TITANIUM .....
Abstract 22
4.1 A Welding Challenge .. 23
4.2 Preparing the the Welding Environment 24
4.2.1 Cleanliness is the key 25
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4.3 Precautions for Welding Titanium . 26
4.3.1 Cleaning and storage 28
4.4 Tips for Welding Titanium .. 28
4.4.1 Titanium Weld Colour Specification .. 31
4.5 Titanium Tube to Tube sheet welding .. 32
4.5.1 Modification in Tungsten electrode for groove and fillet weld 33
4.5.1.1 Why 18 and 30 offset required for tungsten electrode? . 34
4.6 Welding machine for Titanium .. 35
4.6.1 Titanium weld specification 36
4.7 Implications of colours and contamination in Titanium welding .. 37
4.8 Conclusion .. 38
PROJECT II
CHAPTER 5 NOZZLE (PIPE) FABRICATION ....
Abstract 39
5.1 Nozzle (Pipe) Fabricated in Two pieces having Two Long Seams Recently
used method . 41
5.1.1 Reasons for making pipe in Two Pieces . 41
5.2 Nozzle Forming 42
5.2.1 Crack Formation .. 42
5.2.2 Buckling of top die 45
5.2.2.1 Calculation for deflection due to buckling .. 47
5.2.2.2 Finite Element Analysis of Top die 49
5.2.3 Misalignment . 54
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LIST OF FIGURES
Fig. No. Description Page No.
1.1 Different Departments of HED 03
2.1 ZADCO Upper Zakum Oilfield, Abu Dhabi 08
2.2 Titanium Element Coin 09
2.3 Titanium Metal 10
2.4 Comparison between Titanium and Stainless Steel with Temperature
and iron concentration (Mass %)11
2.5 Heat Exchanger 12
2.6Parts Used in Heat Exchanger
14
2.7 U tube Heat Exchanger 15
3.1 Properties of Titanium 18
3.2 Spring Back 20
4.1 Welding with Titanium 23
4.2 Welding with Titanium Precautions and Cleanliness 27
4.3 Titanium Weld colour Indicates Weld Quality 31
4.4 Ti - Tube to Tube sheet welding and AMI Machine 32
4.5 Tube to Tube Sheet groove and fillet weld 33
4.6 Modified Tungsten Electrodes 34
4.7 Tungsten Electrodes used for tube to tube sheet welding 35
4.8 Block Diagram of AVC Machine 36
4.9 Varying level of discoloration 37
5.1 Nozzle (Pipe) Fabrications by Warm Forming 40
5.2Cause and Effect Diagram for Nozzle (Pipe) Fabrications in One
Piece without cracking40
5.3 Nozzle Fabrications in Two Piece 41
5.4 Heat Treatment Cycle 42
5.5 Crack Formation on the surface of Titanium Plate while forming 42
5.6 Reason of Crack Formation 43
5.7 Solution to avoid Crack Formation 43-44
5.8 Aluminium Template to measure the curved surface 44
5.9 Thermo Pen 44
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5.10 Buckling of Top Die 45
5.11 Reasons for Buckling 45
5.12 Solutions to avoid Buckling 46
5.13 Misalignment of two ends of Nozzle while forming 54
5.14 Misalignment of Nozzle due to manual feeding of plate 54
5.15 Basic calculations for Guiding Fixture Plate 55
5.16 Different parts of Guiding Fixture 56
5.17 Movable Plate base part assembly 57
5.18 Movable plate upper part 57
5.19 Marking on the Base plate 57
5.20 Groove at the end of Square threaded bolt 58
5.21 Square threaded bolt 58
5.22 Support Plate 59
5.23 Guiding Fixture assembly steps 59
5.24 Guiding Fixture Drawing 62
LIST OF TABLES
Table. No. Description Page No.
2.1 Different Parts of Heat Exchanger 14
4.1 Welding with Titanium Interpretation based on Weld Colour 32
5.1 Different parts of Guiding Fixture 56
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Introduction,AboutL&T
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Chapter 1
Introduction
1.1About Larsen and Toubro ( L & T)
Larsen and Toubro Limited (L&T), a brand name known to the whole world for its
marvelous extraordinary service is a dream for many. The Company owes its name, origin
and history of achievements to two Danish engineers, Henning Holck-Larsen and Soren
Toubro. Its all about Imagineering the tag line of L&T is the blend of two words
Imagineand Engineeringand L&T makes something that one can only imagine.
In this age of cutting edge technologies, the scenario of the race for the technology is like
the more we try to chase the horizon; the more difficult it becomes to maintain the pace. And
till they hope to overrun the horizon survives, newer technologies will keep on emerging.
Prior to this, the tag line wasWe make the things that make India Proud. They really
make those things that our motherland is proud of. This organization has excelled in everyfield be it Engineering, Construction, IT, Machinery, Electrical etc. and now they are stepping
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ahead with Ship Building. L&T is a technology driven engineering and construction
organization, and one of the largest companies in Indias Private sector. L&T enjoys in
virtually every district of India.
1.1.1 Business Functions of L & T
L&T is consistently expanding the magnitude, scope and range of its operations to offer
value-addition to its clients and shareholders. In the pursuit of becoming one of the
leading and world renowned organizations across the globe, L&T has diversified into
different sectors.
The L&T group has diversified into following operating divisions:
InfrastructureThermal Power GenerationPower Transmission and DistributionHydrocarbonDefence SectorHeavy EngineeringMetallurgical and Material HandlingElectrical and Automation (E&A)RealtyInformation Technology and Technology
Services (IT & TS)
Financial ServicesDevelopment Projects
The Engineering groups of L&T as above, consists of a large number of highly
qualified, trained and experienced staff in various engineering disciplines required by theproject. These groups are equipped with state-of-the-art computer hardware and software
and the same is used for the development of designs and providing assistance during
engineering phase. Specifications, drawings, quality requirements, Bill of Materials and
other documents are released by the Engineering group for the project team to carry out
other execution activities.
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1.2Heavy Engineering Division (HED)
Different Departments of HED
FPGP(Fertilizers,
Petrochemical,
Gasifier
and
PowerPlant)
NuclearPower
Refinery
OilandGas
Aerospace
Defence
Figure 1.1 Different Departments of HED
1.2.1 Fertilizers, Petrochemicals and Heat Exchangers Equipment
department (FPEX)
FPEX is a part of Fertilizers, Petrochemicals, Gasifier and Power plant (FPGP). Fertilizers
and Petrochemicals unit deals with the manufacturing of equipment required in refiners. It
deals in producing various types of equipment required in various petroleum as well as
fertilizer plants all around the world. This unit also deals in making equipment with all
possible materials, even Titanium. All types of shell and tube heat exchangers, high
pressure heat exchangers, spiral and plate heat exchangers, threaded lock closure high
pressure heat exchangers for refineries, carbonate condensersfor fertilizer industries and
specialized multi-tubular reactors for manmade fibres, systems/subsystems related to heat
exchangers.
Also special purpose equipment which includes multi-wall ammonia converters,
converter internals, process gas waste heat boiler system, urea reactors and urea
strippersfor ammonia and urea plants, reactors/regeneratorsand hydro cracking reactors,
Polymerizesand special purpose reactors with Electro-polished internals.
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1.2.2 Functions of Business Units of HED
Each Business Unit is self-reliant & covers the following major functional areas such as:
1. Marketing
2. Design & Product Engineering
3. Material Procurement
4. Project Management
5. Manufacturing
1.3Project Management Group (PMG)
Project management is the process and activity of planning, organizing, motivating, and
controlling resources, procedures and protocols to achieve specific goals in scientific or daily
problems. The primary challenge of project management is to achieve all of the project goals
and objectives while honouring the preconceived constraints. The primary constraints are scope,
time, quality and budget. The secondary and more ambitious challenge is to
optimize the allocation of necessary inputs and integrate them to meet pre-defined objectives.
Earlier there were different departments like shop planning, progress, machine shop planning,
etc. All of them used to work independently of each other. But for any job to get fabricated it
had to go through all the departments. This required the different departments to have co-
ordination with each other.
The new department - PROJECT MANAGEMENT GROUP (P.M.G.) is now structured.
PMG consists of four people drawn from various departments and one group head. Each
PMG is assigned some projects. The PMG has to perform all the planning functions on the
project right from the beginning to the end. This has resulted in better co-ordination and less
confusion while dealing with the customer.
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1.3.1 Characteristics of a project
1. Project is a one-time activity which will never be repeated exactly in the same manner.
2. A project has a definite start and finish i.e. a project is executed in a definite time bound
schedule.
3. A project uses a cross functional relationship because it needs diversified skills and talents
from different professions.
4. A project has definable goals or end results that can be defined in terms of cost, schedule
and performance requirements.
5. Project demands the investment and the benefits are spread for number of future periods.
6. Once the project goals are achieved, the project team will be either disbanded or
reconstituted for another new project.
7. Project passes through several distinct activities which constitute a project life cycle.
1.3.2 Project Organization Structure
If a highly complex project exists, it requires major resources commitments and involves
heavy stakes in results. In such a situation, an organization considers a pure project
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organization. Project organization is a separate organizational entity headed by a project
manager. The hierarchy of project organization is shown below:
1.3.3 Need for PMG (Project Management Group)
To group manufacturing related planning activities together like material planning, shop
planning, machine shop planning and scheduling.
To have effective and better co-ordination and decision making.
To facilitate effective implementation of ERP.
Customer focus Single window contact during execution .
To avoid Chain linking during execution .
To have Better accountability for the various projects .
Hence, on 9th October 1999 the formation of the new department known as Project
Management Group (PMG) took place.
1.3.4 Functions of PMG
Pre manufacturing planning
Co-ordination with various departments
Material planning
Material tracking
Operating instructions
Despatch
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1.3.5 Systems Used
1. Product Lifecycle Management (PLM) - Role in PLM
Define Items in PLM.
Export them to Baan or ERP LN.
Give Project Rights to the Concerned Employee
2. ERP LN (Enterprise Resource Planning)
ERP LN is an ERP (Enterprise Resource Planning) software suite produced by Infor
Global Solutions. The product provides manufacturing companies with a complete
planning system that covers full business processes from planning and purchasing to
sales and customer service.
3. CCPM (Critical Chain Project Management)
The Critical Chain is defined as the longest chain of dependent tasks. Project
Management addresses these issues in the following ways,
1. Planning
2. Estimations3. Safety
4. Project Buffer
5. Resource Buffers
6. Execution
7. Review
In short, CCPM gives us the projected delivery date, rate at which buffer is
consumed, delay, longest chain complete, warns about the delay and also calculates
the project completion date without buffer.
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Chapter 2
Titanium Heat Exchanger
(ZADCO)
2.1 Introduction to the End User of the Project
Figure 2.1 ZADCO Upper Zakum Oilfield, Abu Dhabi
ZADCO Zakum Development Companyis Upper Zakum Oilfield, located approximately
84km offshore to the north-west of Abu Dhabi islands, has an estimated 50 billion barrels of
oil reserves. The field currently produces 500,000 barrels of oil a day (bpd).
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ZADCO, on behalf of its shareholders, has strategic target to increase the production rate
from Upper Zakum from 550 thousand to 750 thousand barrels of oil per day, sustainable for
25 years. Upper Zakum is the second largest offshore oilfield and fourth largest oilfield in the
world, and is owned by Zakum Development Company (ZADCO)
2.2 L&Ts Contribution to the Project
23 Titanium Heat exchangers will be manufactured by L&T in this Project.
4 MP Gas Coolers
3 Booster Gas Compressor Interstage Cooler
6 Booster Gas Compressor Discharge Cooler
4 Gas Lift Compressor Interstage Cooler
2 Gas Lift Compressor Discharge Cooler
And four Spare Tube Bundles
2.3 Specific benefits of Titanium
Since Titanium metal first became a commercial reality in 1950, corrosion resistance has
been an important consideration in its selection as an engineering structural material.
Titanium has gained acceptance in many media where its corrosion resistance and
engineering properties have provided the corrosion and design engineer with a reliable and
economic material.
Many Titanium alloys have been developed for aerospace
applications where mechanical properties are the primary
consideration. In industrial applications, however,
corrosion resistance is the most important property. The
commercially pure and alloy grades typically used in
industrial service.
Figure 2.2 Titanium Element Coin
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Titanium is as strong as steel, nearly half its weight, and highly resistant to corrosion,
which makes it a highly desirable, cost-effective choice for industry, especially defence
and aerospace. Titanium has the following positive characteristics:
30% or better strength to weight ratio over aluminium or steel.
40% lighter than steel, high tensile strength.
High corrosion resistance. Titanium pipe is preferred for marine applications because of its
excellent resistance to salt water.
Low thermal conductivity and expansion.
Much greater stiffness than either aluminium or magnesium.
Operating temperatures up to 900F.
Self sealing against many corrosives (forms Titanium dioxide on its surface).
Titanium and its alloys provide excellent resistance to general localized attack under most
oxidizing, neutral and inhibited reducing conditions. They also remain passive under mildly
reducing conditions, although they may be attacked by strongly reducing or complexing
media.
Titanium metals corrosion resistance is due to a stable, protective, strongly adherent oxide
film. This film forms instantly when a fresh surface is exposed to air or moisture. The oxide
film formed on Titanium at room temperature immediately after a clean surface is exposed
to air is 12-16 Angstroms thick.
Figure 2.3 Titanium Metal
After 70 days it is about 50 Angstroms. It continues to grow slowly reaching a thickness of
80-90 Angstroms in 545 days and 250 Angstroms in four years. The film growth is
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accelerated under strongly oxidizing conditions, such as heating in air, anodic polarization in
an electrolyte. This film is transparent in its normal thin configuration and not detectable by
visual means. A study of the corrosion resistance of Titanium is basically a study of the
properties of the oxide film. The oxide film on Titanium is very stable and is only attacked by
a few substances, most notably, hydrofluoric acid. Titanium is capable of healing this film
almost instantly in any environment where a trace of moisture or oxygen is present because of
its strong affinity for oxygen. Anhydrous conditions in the absence of a source of oxygen
should be avoided since the protective film may not be regenerated if damaged. Titanium
alloys commonly used in industry. Titanium is considered one of the best corrosion-resistant
materials available for seawater service.
Important differences between Titanium and steel or nickel-base alloys need to be recognised.
These are:
Titaniums higher melting point
Titaniums sensitivity toward contamination during welding
Titaniums corrosion resistance has been an important consideration
Compensation for these differences allows Titanium to be fabricated, using techniques similar
to those with stainless steel or nickel-base alloys.
Figure 2.4 Comparison between Titanium and Stainless Steel with Temperature and iron
concentration (Mass %)
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2.3.1 Why Titanium Heat Exchangers?
Titanium Heat Exchanger doesnt mean that all parts of the Heat Exchanger are made up of
Titanium. All these heat exchangers are used in an artificial island located in Abu Dhabi
which is owned by Zakum Development Company (ZADCO). Since it is an artificial island
and no man power is working on that island, also no pure water is available hence sea water is
used in tube side for heat exchanger and sea water is highly corrosive medium. Also Titanium
is considered one of the best corrosion-resistant materials available for seawater service.
Hence as per customer requirement Titanium is used for Tubes, Tube sheet and channel head
assembly (tube side) for long term corrosion resistance effect.
Similarly on shell side H2S (Hydrogen sulphide) gas passes through the shell hence shell is
made up of carbon steel with (Incoloy 825) clad.
2.4 Heat Exchanger
Figure 2.5 Heat Exchanger
A Heat Exchangeris a piece of equipment built for efficient heattransfer from one
medium to another. Heat exchangers are the equipment used to facilitate the process of heat
transfer between the fluids. Heat exchangers find their application in many industries such as
chemical, refineries, petrochemical, fertilizers and power plants. The process of heat transfer
takes place by conduction, convection or direct contact of fluids.
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TitaniumHeatExchanger,HeatExchanger
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2.4.1 Types of Heat Exchanger
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2.4.2 Parts used in Heat Exchanger
Table 2.1 Different Parts of Heat Exchanger
1 Shell 7 Channel Cover
2 Dish Ends 8 Flanges
3 Tubes 9 Partition Plate
4 Tube Sheets 10 Nozzles
5 Baffles 11 Saddles
6 Tie Rods 12 Gaskets and Fasteners
Figure 2.6 Parts Used in Heat Exchanger
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TitaniumHeatExchanger,HeatExchanger
D.J.SanghviCollegeofEngineering 15 ProductionEngineeringdepartment
2.4.3 Shell and tube Heat Exchanger
Shell and tube heat exchangers consist ofseries of tubes. One set of these tubes
contains the fluid that must be either
heated or cooled.
SHELL
Shell is the most important part of the
heat exchanger, as it bears the majority of
pressure inside the heat exchanger. It
houses the whole tube bundle and other
arrangements inside it. The nozzles for the
inlet and outlet of shell side fluid are
welded on the nozzle cut-out over the shell
itself.
The shell is generally manufactured by rolling the plates of the required thickness into the
cylindrical shape of the required diameter. The joint of the rolled plate is welded (the long
seam) to form the shell. If the length of the shell is considerably big then the whole shell is
made in sections and these are welded (the circular seam) to form the shell of required length.
If diameter of the shell is small then pipe can also be used as shell.
DISH ENDS
Dish ends are the dish like structures used to close the end of the shell. The purpose of
using dish ends to close the end of the shell and is to avoid stress concentration at the
corner of the shell and flat plate (generally in case if cover plate is used) and increase the
pressure bearing capacity of the shell.
TUBES
The tube provides the main heat transfer surface. The tube side fluid flows inside the tube
and the shell side fluid flows outside the tube. So the heat exchanger to be more effective
Figure 2.7 U tube Heat Exchanger
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Chapter2,Section2.4
D.J.SanghviCollegeofEngineering 16 ProductionEngineeringdepartment
the thickness of the tubes must be minimum but at the same time the thickness of the tube
should be enough to bear the pressure difference between the shell side and tube side fluid
TUBE SHEET
Tube sheets are flat plates with holes drilled in it for the insertion of tubes. A tube sheet
serves many purposes:
It holds all the tubes rigidly.
It acts as partition between the shell side fluid and the tube side fluid.
As per the type of the heat exchanger there may be one, two or more number of tube
sheets, that also stationary or floating.
BAFFLES
Baffles are the metallic plates with holes for the tubes drilled in it. Baffles are used to
increase the rate of heat transfer by increasing the turbulence of the shell side fluid. The
clearance between the shell and baffles and tubes and baffles must be minimum required; it
avoids the bypassing of fluid. However the clearance should be enough to permit the
insertion of tubes into baffles and the insertion of whole tube bundle into shell.
TIE RODS AND SPACERS
Tie rods are used to hold the baffles firmly while Spacers hold the baffles at the required
distance and prevent it from moving. Tie rods and spacers are the skeletons of the tube
bundle. The tie rods are held into the tapped holes of tie-rod tube sheet, and its other end is
bolted on the last baffle.
GASKETS
The function of the gasket is to serve as a semi-plastic material between the flange facings.The material, through deformation, under loads, seals the minute surface irregularities to
prevent leakage of the working fluid. Gaskets can be of various types Rubber,
Compressed Asbestos, Fibre, Metal, Soft Iron, Spiral Wound etc.
PARTITION PLATE
Partition plates are welded in the middle of the header to make a wall between the
incoming and outgoing tube side fluid. This is a must to prevent the incoming fluid to enter
directly into nozzle for outgoing fluid and bypassing the flow through the tubes.
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TitaniumHeatExchanger,HeatExchanger
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NOZZLES
Nozzles are the spots for the working fluid to enter and leave the heat exchanger. The
following are the nozzles generally provided on the heat exchanger, named according to
their use:
Inlet / outlet nozzle for shell side fluid & tube side fluid.
Intermediate
Drain
Vent
Nozzles are generally welded on the shell. It may protrude inside the shell, except for drain
and vent nozzles.
SADDLES
Saddles are used for supporting and mounting of heat exchanger at the place of installation.
There are generally two saddles, one of which is fixed and other is sliding. Sliding saddle
allows the shell to expand freely so that there is no thermal stress developed in it.
CHANNEL COVER
It is a circular plate bolted to the cover. It is provided to close the outerside of the channel.
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Chapter3,Section3.1
D.J.SanghviCollegeofEngineering 18 ProductionEngineeringdepartment
Chapter 3
Fabrication with Titanium
3.1 Introduction to the Fabrication with Titanium
The fabrication of Titanium product forms into complex shapes is routine for many
fabricators. These shops recognized long ago that Titanium is not an exotic material requiring
exotic fabrication techniques. They quickly learned that Titanium is handled much like other
high performance engineering materials, provided Titaniums unique properties are taken into
consideration.Important differences between Titanium and steel or nickel-base alloys need to
be recognized. These are:
Titaniums lower density
Titaniums lower modulus of elasticity
Titaniums higher melting point Titaniums lower ductility
Titaniums propensity to gall
Titaniums sensitivity toward contamination during welding
Compensation for these differences allows Titanium to be fabricated, using techniques
similar to those with stainless steel or nickel-base alloys.
Figure 3.1 Properties of Titanium
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TitaniumFabrication,WarmForming
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3.2 Warm Forming
Warm Forming is the process of deforming metal heated to a temperature that maximizes
the materials malleability without allowing re-crystallization, grain growth, or metallurgical
fracture. The process allows the part to be successfully formed with net shape features and to
final tolerance that eliminate secondary machining operations. The temperatures are
determined by part material, geometry and final specifications and tolerances.
Warm forming has been done on forming machines for decades, primarily in the aerospace
industry because of materials such as Titanium.
Process temperatures are determined by part material, geometry, and final specifications and
tolerances. Temperatures can range from 200-850C. Possible material applications include:
Commercial Stainless Steels
FA 286 SS
High Carbon & Alloy Steels
Inconel
Titanium (6-2, 6-4)
Heating Titanium will increase their formability and reduces spring back. There will be
greatest improvements in the ductility and uniformity of properties for most Titanium alloys is
at temperatures above 500 C. At still higher temperatures, some alloys exhibit super
plasticity.
Warm Formingis the process of deforming metal at elevated temperature without allowing
re-crystallization, grain growth, or metallurgical fracture.
The temperatures are determined by part material, geometry and final specifications and
tolerances.
3.2.1 Spring back
Spring back of Titanium is due to,
(1) The elastic recovery of metal after cold forming.
(2) The degree to which metal tends to return to its original shape or contour after undergoing
a forming operation.
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(3) In flash, upset, or pressure welding, the deflection in the welding machine caused by the
upset pressure.
A loss of 15 to 25 degrees in included bend angle must be expected, due to spring back of
Titanium after forming. Higher the strength of the alloy, greater the degree of spring back is
to be expected. Compensation for spring back is made by over forming. Hot sizing of cold
formed Titanium alloy parts has been successfully employed. This technique virtually
eliminates spring back when the hot sizing temperature is high enough to allow stress relief.
Figure 3.2 Spring Back
3.2.2 Description warm forming with Titanium channel nozzle plates
1. Carry out inspection of half nozzle segment.
2. Carry out first pass heat treatment of plate before initial forming as per cycle mentioned
below ,
Loading Temp 150 C (Max)
Rate of heating 50 C/hr. (Max)
Soaking temp 3503770 C
Soaking time 30 Min (minimum)
3. Carry out forming activity such that temperature does not drop below 300C.
4. Continue forming till the temp does not drop below 300C. If the entire segment can be
formed in single stage without drop of temp below 300C, then directly cool the segment
to room temp after forming by slow cooling (use insulation wrapping for cooling
activities).
5. If the temp in the course of forming approaches 300C, stop the forming activity & put the
partially formed segment in furnace again for reheating to 350370C followed by 30
minutes soaking time.
6. This activity to be repeated till the complete segment is not formed.
[Based on progress of forming & temp drop, forming may require 2/3 stages].
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TitaniumFabrication,WarmForming
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After forming is completed, cool the segment to room temp. after forming by slow cooling
(use insulation wrapping for cooling activities).
4. Clean nozzle half segment after cool down.
8. Clear nozzle half segment through inspection.
9. Measure the inside circumference of each half.
10. In case of additional length in circumferential direction trim the half to meet the
requirement.
11. Send each half for long seam WEP machining.
12. Final circumference after setup of 2 halves & considering root gap as mentioned in
drawing should be Final circumference.
13. Circseam WEP to be prepared after long seam welding and rerolling, if required.
3.2.3 Care to be taken during warm forming with Titanium nozzle plates
1 Warm forming to be carried out in temp of range 300350 C.
2 Temperature shall bee monitored during forming operation. Charts for the specific part
heating in furnace to be submitted to QC after forming is completed.
3 During forming if temperature drops below 300 C then forming operation to be
terminated and reheat the plate as per cycle mentioned above.
4 If possible, die and punch to be heated to 200 C to avoid the heat sink during forming
operation.
5 Proper lubricant to be used during warm forming on the die to minimise the surface
indications.
6 Check for indication of cracks / linear indication at any point of forming. Stop further
forming at the juncture of any crack development and report the detail.
7 After successful completion of forming, carry out PT on entire outer surface of nozzle
pipe. This to ensure no crack has developed during forming.
8 Round of all sharp corners to 2R (min).
3.2.4 Forming Defects
There are certain surface and internal defects that can be caused by improper forming
techniques.Surface defects include surface tears, cracks, thinning, laps, embedded material
while internal defects may include strain induced porosity (SIP), grain separation,
intermetallic compound.
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ProjectI
D.J.SanghviCollegeofEngineering 22 ProductionEngineeringdepartment
PROJECT I
INTRICACY IN WELDING TITANIUM
Abstract
This text covers the state of the art of welding procedures for Titanium and methods
employed in the present are described. Necessary additional processing such as pre-weld
cleaning, joint preparation, post-weld cleaning, post-weld operations, Precautions and Tips for
welding Titanium are also included, since they form an integral part of the welding processes
without which successful welding cannot be accomplished. The need for proper pre-weld
cleaning operations and proper shielding to prevent contamination of Titanium welds is
emphasized throughout.
This text also contains the welding of tubes to tube sheet which are made up of Titanium.
And problem faced while joining tube to tube sheet due to groove provided on tube sheet.
Hence modification is done on the tungsten electrode for proper welding between tubes and
tube sheet. It also contains the implications of colours and contamination in Titanium
welding.
This chapter contains the areas in obtaining better weld quality of Titanium, to reduce the
cost of the fabrication and obtaining desired service performance in structures fabricated from
Titanium.
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IntricacyinWeldingTi,Aweldingchallenge
D.J.SanghviCollegeofEngineering 23 ProductionEngineeringdepartment
Chapter 4
Intricacy in Welding Titanium
Figure 4.1 Welding with Titanium
4.1 A Welding Challenge
Many of the less than optimum qualities of Titanium directly affect welding, resulting in it
getting a reputation as being difficult to work with because manually welding with Titanium
is very difficult and it requires high skilled labour. Also Titanium is very expansive material
than carbon steel and it is very susceptible to damage. So handling and storage of titanium has
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Chapter4,Section4.1,4.2
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to be very careful and precise. Also manually welding with Titanium is limited to 1 mm to 25
mm (approx.) thick.
At high temperature, Titanium becomes highly reactive to chemicals in its environment. In
regular air, welding contaminates Titanium with carbides, nitrides, and oxides that make the
weld and HAZ (heat-affected zone) brittle, resulting in lower fatigue resistance and notch
toughness. In addition, chlorine from your sweat or from cleaning compounds can create
corrosion on the weld. Thus, the weld and its back side must be protected from contamination
to ensure a decent weld. Even friction from grinding wheels (especially aluminium oxide
wheels) can develop enough heat and provide the contaminants to undermine the weld.
Manual welding of tube to tube sheet joint cause more defect and requires skilled person
which directly affect the cost of the process. To save the cost, special method for tube to tube
sheet joint is achieved and also automatic welding machine is used. Even there is a special
requirement of tungsten electrode for groove and fillet weld. Given these considerations, with
careful preparation, any professional welder can obtain quality Titanium welds.
Difference between TIG Welding of Steel and Titanium
TIG Welding of Steel
Tig welding steel is very easy. The polarity typically used is DCEN (direct current
electrode negative), Argon gas, and Thorium Tungsten. For welding steel and stainless
steel the Tungsten needs to be shaped to a fine point
TIG Welding of Titanium
Welding Titanium uses Argon gas and many times requires an Argon bath to be welded
in. In many cases the gas coverage that the TIG torch gives is not enough. Titanium canbe welded using 2% Thorium Tungsten with an AWS classification of EWPTh-2 and
with DCEN (direct current electrode negative)
4.2 Preparing for the Welding Environment
Because contamination is a primary concern, Titanium fabrication demands exacting attention
to cleanliness of the metal itself and the shop environment. Often welders working with
Titanium along with other metals will set an area aside exclusively for Titanium fabrication.
For acceptable results, that area must be free of air drafts, moisture, dust, grease, and other
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contaminants and contamination contributors. That means machining, painting, grinding,
torch cutting, and the like should not occur in the same area. Ideally, you should minimize
humidity to maintain a low dew point.
4.2.1 Cleanliness is the key
It is critical to keep Titanium clean prior to and during welding. Because it is a highly
reactive metal, Titanium responds quickly (and negatively) to contaminants such as oils from
forming and drawing process, shop dust, paint, dirt, body oils (from hands), cutting fluids and
more. Encountering any or all of these contaminants can easily lead to localized corrosion or
cause weld embrittlement and failure. To prevent such issues, always keep the welding
environment as clean as possible and minimize airflow to avoid disrupting the shielding gas
coverage that protects the weld pool.
Prior to welding, it is critical to pre-clean both the base material and the filler rod. During
this process, always wear nitrile gloves dedicated to the task and begin by degreasing both
components. Remove surface contamination by wiping the material with methyl ethyl ketone
(MEK), acetone or other non-chlorinated solvent soaked into a clean, lint-free cloth. After
cleaning them, place the filler rods in an airtight container until ready for use, as it protects
against re-contamination.
Due to its reactivity, Titanium easily forms a very hard oxide layer on its surface (similar to
Aluminium). This layer provides Titanium with its corrosion resistance, but it also melts at a
higher temperature than pure Titanium. For that reason, it must be removed from the area to
be welded. Use a die grinder with a carbide deburring tool or carbide file set to a low
grinding speed to remove the layer of Titanium oxide without overheating the base metal,
which can also lead to embrittlement. After removing the oxide layer, once again wipe the
area to be welded using MEK, acetone or other non-chlorinated solvent, and allow it to dry
completely before welding.
Two important words of caution: 1) Be certain to use the grinder exclusively for the task so
as to avoid introducing contaminants from other jobs. 2) Never use steel wool or other
abrasives to remove the Titanium oxide layer as it can contaminate the metal and lead to weld
defects.
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Chapter4,Section4.3
D.J.SanghviCollegeofEngineering 26 ProductionEngineeringdepartment
4.3 Precautions for Welding Titanium
1. Titanium welding shall be performed in clean, totally enclosed separate fabrication
facility free from iron contamination.
2. Tools and hand brushes shall be stainless steel and restricted to use on Titanium only and
to be colour coded: Pink.
3. Titanium clad shall be protected from weld spatter, damage and iron contamination using
Aluminium cover plates, stick on plastic covering and blanks during all phases of
fabrication.
4. Dew Point and Purity of gas used for Titanium WeldingDew Point: < -51C
Gas Purity: shall be confirmed by measurement of oxygen level in gas (
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13. In addition to primary shielding of the weld pool, secondary shielding i.e. back purging
shall be used until the Titanium surface temperature falls below 300C. A trailing shield
of 100-150 mm shall be used.
14. If any contact occurs between tungsten electrode and filler wire in arc, welding shall be
stopped immediately, tungsten electrode changed or redressed and contaminated area
removed before welding is resumed.
15. After completion of one bead, stop the arc (Post flow of gas still on) and hold the torch
and trailing shield for minimum two minutes to allow the weld to cool down.
16. Fillet welds (of any sizes) shall be done with a minimum of 2 passes.
17. Finished Titanium weld shall be left in as welded condition with no wire brushing,
buffing or grinding.
18. Welds shall be visually inspected on completion. Welds shall be compared with
comparator.
19. Contact welding engineering for rectification of weld having other colour.
20. Filler wire shall be kept wrapped when not in use.
Figure 4.2 Welding with Titanium Precautions and Cleanliness
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Chapter4,Section4.3
D.J.SanghviCollegeofEngineering 28 ProductionEngineeringdepartment
4.3.1 Cleaning and storage
1. Titanium shall be prevented from possible cut, scratch, spatter, arc burn etc. on the
Titanium clad / Titanium plates during fabrication activities such as forming, machining,
welding and transportation.
2. During cutting, grinding, machining, welding etc. the Titanium surface shall be applied
with calcium oxide paste in order to protect the surface from adhesion of foreign
contamination.
3. Cleaning of base metal and filler wires shall be cleaned upto 100 mm on both sides of the
weld edge preparation. Filler wires and Base metals after cleaning shall suitably be
wrapped till use.
4. Titanium should be stored in area identified for Titanium only.
5. Storage racks or supports should be covered with non-contaminating materials (Rubber /
Plastic / Wood).
6. During storage Titanium should be covered with rubber sheet covering or plastic film
sheet.
4.4 Tips for Welding Titanium
1. Before start of welding, filler wires and both the edges of base metal shall be cleaned
upto 30 mm minimum on either side. Base metal and filler wire shall be cleaned and
degreased with Non-chlorinated solvent (acetone). Use of methyl alcohol is not allowed.
Cleaning shall be done using a clean lint-free, starch-free white cloth dipped in acetone.
2. Before start of each welding session a bead on plate trial shall be done to verify there is
good shielding gas coverage. A silver or straw colour weld indicates satisfactory
shielding.
3. For welding Titanium an adequate inert gas shield is required for the weld metal pool
and adjacent base metal (primary shielding) but also for hot solidified weld metal and
HAZ (secondary shielding), and the back side of the weld joint (Backing).
4. For primary shielding the largest nozzle consistent with accessibility and visibility and
which give laminar flow of the shielding gas must be used on the arc welding torch.
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IntricacyinWeldingTi,TipsforweldingTi
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5. Argon gas flow must be started well in advance before the actual start of welding to
ensure that any air entrapped in the gas delivery hoses and shielding / trailing
compartments gets completely displaces.
6. Purity of Shielding and backing Argon shall be 99.997%. Whereas, trailing Argon may
be 99.995% minimum. Maximum permissible oxygen content in backing gas shall be
0.5%.
7. Each Argon cylinder shall be verified for proper certification before use on job. Based on
plate trials with colour test shall be done every time a new cylinder is deployed.
8. Welding power source shall have facilities such as pre-flow, high-frequency start, up-
slope, down-slope / crater filling, post-flow and shall deliver DCEN current.
9. Autogenously Welding shall not be done. GTAW torches shall be fitted with Gas-lens.
10. As the primary gas shielding advances with the arc welding gun, a secondary inert gas
shield must be supplied till the weld metal and surrounding HAZ has cooled to a
temperature of at least 300C. A trailing shield of 100-150 mm (min.) length shall be
used welding activity.
11. The proportion of shielding and baking Argon gas flow rate must be adjusted so as to
achieve proper weld penetration.
12. Contact type thermometer / infrared devices shall be used to check preheat and interpass
temperature.
13. After turning off the arc, the torch must be held in position so that the post-flow shielding
gas continues to cool the weldment until its temperature drops below 300C.
14. Because moisture content rises as cylinder pressure drops, gas cylinders shall be switched
when the pressure reaches about 25 bar.
15. When adding filler rod it must be made sure that the rod end always stays within the gas
envelop.16. To prevent contaminants from entering the weld pool via the filler rod the end of the filler
rod must clipped off before every use. The filler rods must be stored in an air tight
container when not in use.
17. Fillet welds (of any sizes) shall be done with a minimum of 2 passes.
18. All Titanium welds shall be done using string / weave technique. Weaving width shall be
bare minimum to ensure side wall fusion.
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Chapter4,Section4.4
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19. Welding once started must be completely in that welding session itself. No seam shall be
left in tack / partially welded condition for prolonged time. In event of such time gap, re-
cleaning of the joint shall be done prior to continuation of welding.
20.No grinding or wire brushing is permitted on finished weld surfaces. Grinding shall only
be done for removal of local indications or discontinuities or iron contamination, if any.
21. Grinding wheels and wire brushes used shall be dedicatedly used on Titanium surfaces
and shall be of Austenitic stainless steel only.
22. All ground surfaces shall be dressed using metallic burr-wheel / cutter to remove 0.5-1
mm metal prior to welding.
23. All tools used during cutting, handling, forming, fitment (set-up), welding shall be of
Austenitic Stainless steel / Plastic coated / wood.
24. Iron contamination check (Ferroxyl Test) may be done on Titanium surfaces as and how
required.
25. Visual examination shall be done after completion of each weld pass on weld bead and
area adjacent to the weld. Acceptance and interpretation shall be done as per table below.
Unacceptable welds and base metal surfaces shall be repaired as per weld repair method
L &T- ZADCO-Ti-Weld Repair and re-examined. Re-melting of welding onto material
that has been dis-coloured by heating is not allowed until the cleaning measures
stipulated earlier for base metal and weld preparation are complied with.
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IntricacyinWeldingTi,TipsforweldingTi
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4.4.1 Titanium Weld Colour Specification
Figure 4.3 Titanium Weld colour Indicates Weld Quality
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Chapter
4,
Section
4.5
D.
J.
Sanghvi
College
of
Engineering
32
Production
Engineering
department
Table 4.1 Welding with Titanium Interpretation based on Weld Colour
Acceptable colour: Silver and Light Straw
4.5 Titanium Tube to Tube sheet Welding
Figure 4.4 Ti Tube to Tube sheet welding and AMI Machine
Colour Interpretation
Silver Correct Shielding, SatisfactoryLight Straw Slight Contamination, but Acceptable
Brown or Dark Straw Slight Contamination, may be Acceptable
Brown-BlueHeavier Contamination, but may be Acceptable-
depending on services
Bright-Blue Heavier Contamination, unlikely to be Acceptable
Green-Blue Very heavy contamination, Unacceptable
Dull salmon Pink Very heavy contamination, UnacceptableWhite Oxide Very heavy contamination, Unacceptable
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IntricacyinWeldingTi,TubetoTubesheetwelding
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The Tube to Tube sheet welding for most material grades is performed prior to expanding
for two principal reasons as follows and the advances in tube end joining are,
1) To enable the welding gases that may be trapped behind the weld to escape down the
gap between the tube and tubehole thereby avoiding blowoout through the weld
2) To avoid the situation where the presence of oil and fluids used during expansion do
not have the opportunity to contaminate the weld pool.
Tube to Tubesheet Weld, Provides tubesheet Integrity and Eliminates Crevices at Water
side.
Usually in tube to T/S welding the angle between electrode and T/S is 20 and the angle
between elctrode tip is 60 for fillet weld.
4.5.1 Modification in Tungsten electrode for Groove and Fillet weld
Figure 4.5 Tube to Tube Sheet Groove and Fillet weld
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Chapter4,Section4.5
D.J.SanghviCollegeofEngineering 34 ProductionEngineeringdepartment
In Tube to Tubesheet welding with Titanium, first tack welding is done to hold the tubes
with tube sheet properly. After tack welding Root pass (Stage I) is done. In Root pass filler
wire is not used. Only Tungsten electrode is used to fuse the tubes with tubesheet. In Stage II
Titanium filler wire is used with Tungsten electrode to weld the tube with tube sheet.
Here in some tubesheets, there are groove provided as shown in above figure. But for root
pass normal electrode with 60 offset of diameter 2.5 mm was not properly fuse the tubes
with tubesheet, the gas fumes which came out will puncture or dont allow to properly fuse
both (Tube and T/S) in the groove, which cause improper welding.
4.5.1.1 Why 18 and 30 offset required for tungsten elctrode ?
In this project the tubesheets are provided with groove as shown in figure 4.5 and for better
penetration on wall side of tube sheet, eccentric electrodes are required because normal
electrode with 60 offset will try to puncture the tube or it dont allow to fuse both (Tube and
T/S) properly in the groove. This eccentricity is such that the electrode will properly weld
tube and tubesheet for root pass.
Figure 4.6 Modified Tungsten Electrodes
Hence specially machined electrode with offset of 18 and 30 are used for root pass and final
stage welding respectively (refer figure 4.7). Also this welding is done by AMI (Arc Machine
Incorporation) machine (Refer figure 4.5) for better welding properties. While welding this
machine provides purging from inside the tubes for better weld quality.
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IntricacyinWeldingTi,TubetoTubesheetwelding
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Figure 4.7 Tungsten Electrodes used for tube to tube sheet welding
4.6 Welding Machine for Titanium
Titanium Welding Machine is used to weld the Titanium for Long Seam (LS) and CircSeam
(CS) welding. Here we use AVC Arc Voltage Controller Machine for Automatic LS and CS
Welding.
In this Machine Gear box, PLC (Power Logic Control), Process Control System, Human
Machine Interface, DC motor and Driver is used for different function.
DC motor and Driver gives the supply to the Machine.
Gear Box will reduce the speed of the column to move the electrode slowly at the speed
of 80-130 mm/min.
Arc gap of 15 V is maintained by the Voltage drop.
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Chapter4,Section4.6
D.J.SanghviCollegeofEngineering 36 ProductionEngineeringdepartment
If Arg gap is out of defined range 0.3 (i.e. 14.7 V-15.3 V), then the signal goes to PLC.
Process Control System senses the voltage drop and adjust as per defined range i.e. 15 V
This signal passes to the column through by HMI, which resricts the movement of the
column to the predefined range.
After all adjustment the automatic welding process starts as per following specifications.
Figure 4.8 Block Diagram of AVC Machine
4.6.1 Titanium Weld Specification
Arc Gap : 15 V
Arc gap Band : 0.3 (i.e. 14.7-15.3 v)
Weld Speed : 100 mm/min
Weld current : 100 A
Arc Speed : 80-130 mm/min
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IntricacyinWeldingTi,Tiweldcolourandcontamination
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4.7 Implications of colours and contamination in Titanium Welding
The worst problems arise from:
1) Using a filler rod other than Titanium (like stainless steel or nickel alloy rod). If you weld
Titanium with anything other than Titanium, you will hear the sound of the weld cracking like
glass: tink, tink, tink you can actually break the weld by tapping it lightly with a ball peen
and man is it brittle.
2) Not shielding the back side of the weld with argon. If what you are welding is thin enough
to penetrate or even get red hot, you absolutely must shield both sides of the weld adequately
or the weld will be very brittle.
3) Not using a large nozzle/cup or trailing shield to shield the weld puddle. Using a normal
size nozzle like #7 (7/16 diameter) will not effectively shield the heated area to prevent the
embrittlement that occurs when Titanium gets too hot without shielding gas.
Titanium absorbs elements like oxygen and nitrogen at these temperatures and depending on
what reference you use, 800F seems to be the cut off for keeping it argon shielded.
Discoloration on Titanium is not a problem by itself and is more of an indicator that there
might be a problem. Because it is known that it happens in a certain sequence: straw, brown,
purple, blue, dull salmon pink, grey with oxide flakes. It is part of the inspection criteria.
These images show the varying levels of discoloration.
Figure 4.9 Varying level of discoloration
Some welding codes limit discoloration to straw colour. Some welding codes allow a little
blue discoloration in certain applications. Ideally the weld will be perfectly silver like the first
weld shown. That should be the goal. Light straw and even brown discoloration can be
acceptable if the discoloration is on the welded side. Discoloration on the penetration side of a
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Chapter4,Section4.8
D.J.SanghviCollegeofEngineering 38 ProductionEngineeringdepartment
full penetration weld means that the actual puddle was exposed to contamination (The
unwanted pollution of something by another substance) from air. Thats why purge monitors
should be used to verify purity of purge when welding Titanium.
4.8 Conclusion
Titanium has one of the most difficult crystal structures and quite often don't lend
themselves to standard forming techniques.This material, however, can be formed even into
complex parts if the proper equipment and procedures are used. This material is costly and
very susceptible to damage.
The objective of this project is to understand Titanium welding procedure, pre-weld and
post-weld cleaning, precautions and Tips for welding with Titanium for good fabrication
practice and achieve better weld quality as per weld colour required. For tube to tube sheet
joint, modified tungsten electrode is used with 18 and 30 offset for root pass (without filler
wire) and final stage (with Titanium filler wire) welding respectively, for groove and fillet
weld between Titanium tubes and tube sheet. Filler wire is not used during root pass to reduce
the cost of welding process. Also automatic welding machine (AMI Machine) is used for
Tube to tube sheet joint which gives better penetration and better weld quality than manualwelding.
Since Titanium welding needs high skilled and experienced welders, Titanium welding
needs more time. As there is automatic welding machine is used with modified tungsten
electrode lead to achieve better weld quality for tube to tube sheet joint and also reduces the
cost of fabrication process.
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ProjectII
D.J.SanghviCollegeofEngineering 39 ProductionEngineeringdepartment
PROJECT II
NOZZLE (PIPE) FABRICATION
Abstract
This text covers the method by which the Titanium Nozzle (Pipe) can be fabricated by
warm forming technology in one single piece for which cause and effect diagram is made to
understand the problem.
Fabrication of Nozzle in one piece cause the defects like crack formation on the curved
surface of Titanium plate, buckling of top die and misalignment of two ends of the formed
nozzle. These reasons lead to the making of titanium Nozzle in Two pieces, which will
improve the machining and fabrication time and cost of the fabrication process.
This chapter contains the solution to avoid all these defects and fabrication of nozzle in one
single piece to increase the productivity and decrease the cost of fabrication process. For
which calculation for deflection and analysis of top die is done and guiding fixture is made. It
is expected to increase the quality of the product by decreasing one long seam (because
welding with Titanium is very critical process) and reduce the cost of fabrication up to 50 %.
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Chapter5,Section5.1
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Chapter 5
Nozzle (Pipe) Fabrication
Figure 5.1 Nozzle (Pipe) Fabrications by Warm Forming
Figure 5.2 Cause and Effect Diagram for Nozzle (Pipe) Fabrications in One Piece without cracking
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NozzleFabrication,Recentlyusedmethod
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5.1 Nozzle (Pipe) Fabricated in Two pieces having Two Long
Seams Recently used method
Figure 5.3 Nozzle Fabrications in Two Piece
Since Titanium welding requires high skilled labour and specific weld parameters, its
fabrication consumes more time.
Limitation of this process-
a. Nozzle fabrication in two pieces consumes more holding and cutting time, Also Two
more Weld Edge Preparations (WEP) and one extra long seam welding adds to the
fabrication process.
b. This process indirectly affect the time and cost of the welding process and also
increases the cost of the filler wire (refer figure 5.2).
If only one long seam can be done then half time will be reduced.
This will improve the productivity and make the fabrication easier.
5.1.1 Reasons for making pipe in Two Pieces are,
1) Crack Formation on the curved surface
2) Buckling of Top Die (Punch)
3) Misalignment of two ends
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Chapter5,Section5.2
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5.2 Nozzle Forming
To Form the Nozzle in One Piece from Titanium Plate using Warm Forming Technology,
We have to overcome the issue of Crack Formation, Buckling and Misalignment.
Figure 5.4 Heat Treatment Cycle
5.2.1 Crack Formation
Figure 5.5 Crack Formation on the surface of Titanium Plate while forming
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NozzleFabrication,NozzleForming
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Reason of Crack Formation
Figure 5.6 Reason of Crack Formation
The chance of crack formation takes place while forming the Ti Plate at 370C in only one
stage. Because of sudden change in crystalline structure at surface and decrease in
temperature forms crack on the curved surface.
Solution to avoid Crack on the Curved Surface
Figure 5.7 a) Solution to avoid Crack Formation
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Chapter5,Section5.2
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Figure 5.7 b) Solution to avoid Crack Formation
First heat the Ti plate in Furnace up to 370C then form it to required shape on preheated
die until temperature goes down to 300C. Measure the required entity with the help of
template.
Figure 5.8 Aluminium Template to measure the curved surface
To check the temperature of Ti plate Thermo-pen of that
particular temperature is used.
Figure 5.9 Thermo-pen
STAGE 1 STAGE 2
REHEAT UP TO 370C
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NozzleFabrication,NozzleForming
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5.2.2
Buckling of Top Die
Figure 5.10 Buckling of Top Die
Reasons for Buckling
1. Thickness of the both Holding Plate of Top Die is different, which cause uneven load
on Die.
2. Diameter of the Top Die (Material: Low Carbon Steel and 100 mm) is small to
handle 250 ton load at 200C.
Figure 5.11 Reasons for Buckling
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Chapter5,Section5.2
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Solution to avoid Buckling
1. Thicknessof both the Holding Plate of Top Die should be Same, to avoid uneven
Load Distribution.
2. Diameter of Top Die should be more (approx. 200 mm) to avoid Buckling made up of
same material.
Figure 5.12 Solutions to avoid Buckling
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NozzleFabrication,NozzleForming
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5.2.2.1 Calculation for the Deflection due to Buckling
Top Die Material: Low Carbon Steel (< 0.3 % C)
Pre-heated up to 200C
Modulus of Elasticity = E (at 200C) = 27.7 x 10^6 psi (Pound per Square Inch)
= 1.9098 x 10^11 Pa
= 1.9098 x 10^5 MPa
Top Die Diameter = D = 200 mm
Load applied = P = 250 N
For Fixed Beam,
RB = RC= P/2 = 250/2 = 125 N
Deflection : Yx = ( P*X2 / E*I ) [(x/12) (L/16)] .. for 0 < x < L/2
But YMaxat x = L/2
YMax = ( P*L3) / (192*E*I ) ..... . (I)
Where,
YMax : Maximum Deflection at Centre (i.e. at A)
I : Moment of Inertia
I = ( / 64) * (D^4) ........ (II)
Therefore,
YMax= ( 250 x L3) / [192 x 1.9098 x 10^5 x ( / 64) x (D^4)] .. From Eqn. (I) & (II)
= (1.3986 x 10-4)*[( L3/ (D^4)] .... (III)
1) Maximum Length = L = 600 mm
Therefore,
YMaxat L= 600 mm and Dia. D = 200 mm
= (1.3986 x 10-4)*[( 6003/ (200^4)]
= 0.01888 x 10-3mm
= 0.0188 (micrometer)
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Chapter5,Section5.2
D.J.SanghviCollegeofEngineering 48 ProductionEngineeringdepartment
2) Maximum Length = L = 334 mmTherefore,
YMaxat L= 334 mm and Dia. D = 200 mm
= (1.3986 x 10-4)*[( 3343/ (200^4)]
= 0.003257 x 10-3mm
= 0.003257 (micrometer)
Hence the design is safe.
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NozzleFabrication,NozzleForming
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5.2.2.2 Finite Element Analysis of Top Die
Model name: Part1Current Configuration: Default
Solid Bodies
Imported2 Treated As Volumetric Properties
Solid Body
Mass:147.034 kg
Volume:0.0188506 m^3
Density:7800 kg/m^3
Weight:1440.94 N
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Chapter5,Section5.2
D.J.SanghviCollegeofEngineering 50 ProductionEngineeringdepartment
ModelReference Properties Components
Name: Plain CarbonSteel
Modeltype: LinearElasticIsotropic
Defaultfailure
criterion: Max
von
Mises
Stress
Yieldstrength: 2.20594e+008 N/m^2
Tensilestrength: 3.99826e+008N/m^2
Elasticmodulus: 1.9e+011N/m^2
Poisson'sratio: 0.28
Massdensity: 7800kg/m^3
Shearmodulus:
Temperature:
7.9e+010N/m^2
200c
Thermalexpansion
coefficient:
1.3e005/Kelvin
SolidBody
1(Imported2)(
Part1)
Fixturename FixtureImage FixtureDetails
Fixed1
Entities: 2face(s)
Type: FixedGeometry
ResultantForces
Components X Y Z Resultant
Reactionforce(N) 0.000401258 0.000764072 212.093 212.093
ReactionMoment(Nm) 0 0 0 0
Loadname LoadImage LoadDetails
Force1
Entities: 1face(s)
Type: Applynormalforce
Value: 250N
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NozzleFabrication,NozzleForming
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Contact
Contact
Image Contact
Properties
GlobalContact
Type: Bonded
Components: 1component(s)
Options: Compatible
mesh
TotalNodes 11006
TotalElements 7265
MaximumAspectRatio 7.7265
%ofelementswithAspectRatio10
0
%ofdistortedelements(Jacobian) 0
Timetocompletemesh(hh;mm;ss): 00:00:01
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Chapter5,Section5.2
D.J.SanghviCollegeofEngineering 52 ProductionEngineeringdepartment
Name Type Min Max
Displacement1 URES:ResultantDisplacement 0mm
Node:1
2.07776e005mm
Node:9460
Part1Study 1DisplacementDisplacement1
Name
Type
Min Max
Stress1 VON:vonMisesStress 111.368N/m^2
Node:9070
59095.2N/m^2
Node:9495
Part1Study 1StressStress1
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NozzleFabrication,NozzleForming
D.J.SanghviCollegeofEngineering 53 ProductionEngineeringdepartment
Name Type Min Max
Strain1 ESTRN:EquivalentStrain 1.29906e009
Element:3357
1.26746e007
Element:1922
Part1Study 1StrainStrain1
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Chapter5,Section5.2
D.J.SanghviCollegeofEngineering 54 ProductionEngineeringdepartment
5.2.3 Misalignment
Figure 5.13 Misalignment of two ends of Nozzle while forming
Reason of Misalignment
Misalignment occurs due to manually feeding (only by hand, without any guided path) of
hot plate for forming, which cause improper alignment of two ends.
Figure 5.14 Misalignment of Nozzle due to manual feeding of plate
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NozzleFabrication,NozzleForming
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Solution to avoid Misalignment
Attach a Guiding Fixture on the Bottom Die to avoid Misalignment of plate while
forming. This fixture will form the nozzle without misalignment, which directly affect the
fabrication process of the nozzle.
Assumption : Both edges of a Ti Plate should be perfectly 90.
5.3 Guiding Fixture
Figure 5.15 Basic calculations for Guiding Fixture Plate
To decide the dimension of a fixture plate is totally depend on the range of the Nozzle
diameter (shown in figure 5.15).
To guide the plate, above mentioned shape and size of the fixture plate is required with
tongue and groove guide way.
This Fixture can be made from scrap material of low carbon steel.
In this fixture, 1) Two guiding plate, 2) One base plate, 3) One square threaded bolt and
4) Support plate is required.
In guiding plate, one fixed plate and one movable plate assembly is required.
Refer below figure.
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Chapter5,Section5.3
D.J.SanghviCollegeofEngineering 56 ProductionEngineeringdepartment
Figure 5.16 Different parts of Guiding Fixture
Table 5.1 Different parts of Guiding Fixture
1 Base plate 5 Movable plate base part
2 Fixed plate 6 Movable plate upper part
3 Support plate 7 M24 Square threaded bolt
4 Movable plate base part with keyway 8 Nut and Bolt (2 Nos.)
5.3.1 Functions of every part of the Guiding fixture
1) Guiding plates
There are two guiding Plate in the above fixture. Which is used to guide the Ti plate, so it
want get misaligned and form a perfect Nozzle with proper alignment.
On both plates there is two keyways are provided, to maintain parallelism between two
plates.
Fixed Guiding Plate is welded on one side with the Base plate of fixture.
Movable Plate Assembly is shown in below figure.
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NozzleFabrication,GuidingFixture
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Figure 5.17 Movable Plate base part assembly
1. Square threaded bolt is attached to the movable plate base part (with keyway).
2. Another part of base part is passed through the groove of bolt.
3. Align both plate of base part with one other.
4. Pass M4 bolts through respective hole, to connect the two plates.
5. Tight bolts with the help of nut to fix the movable plate base part assembly.
Movable plate upper part is slides on the keyway provided on base part.
This upper part is removable, to remove the nozzle once it forms.
Figure 5.18 Movable plate upper part
2) Base PlateThis plate is used to mount all the parts of fixture. On base plate two keyways are
provided of entity same as that of guiding plate, which will provide the guided path for
guiding plate to maintain parallelism. On this plate markings are done at required length,
to move the movable guiding plate.
The whole fixture is welded to the bottom die with
this base plate.
Figure 5.19 Marking on the Base plate
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Chapter5,Section5.3
D.J.SanghviCollegeofEngineering 58 ProductionEngineeringdepartment
3) Square threaded bolt
Square thread is used for self locking arrangement. The function of this bolt is to
provide movement (back and forth) to the movable plate at specific distance, for which at
the end of the bolt groove is provided, to fix in the movable plate base part assembly.
Figure 5.20 Groove at the end of Square threaded bolt
The size of the bolt is decided on the basis of size of the guiding plate. To rotate the bolt,
one handle is provided on another end of the bolt.
Figure 5.21 Square threaded bolt
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NozzleFabrication,GuidingFixture
D.J.SanghviCollegeofEngineering 59 ProductionEngineeringdepartment
4) Support plate
This plate is welded on another side with the Base plate of fixture.
It has an internal threading of M24 to pass the bolt through it. This
plate is working as nut and allows the bolt to move back and forth.
Figure 5.22 Support Plate
5.3.2 Steps to assemble the Guiding Fixture
Figure 5.23 Guiding Fixture assembly steps
1. First take a base plate having two keyway machined on it.
2. Weld a support plate on it and pass the Square threaded bolt through it.
3. Attach a movable plate base part on one end of bolt having groove.
4. Tight both part of base part with M4 nut and bolt. Also weld the fixed guiding plate.
5. Slide the movable plate upper part through the keyway.
6. Weld the whole fixture to the bottom die through base plate.
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Chapter5,Section5.3
D.J.SanghviCollegeofEngineering 60 ProductionEngineeringdepartment
5.3.3 Welding Calculations
For Carbon steel (C30) Material used for Fixture;
Tensile strength, ft = 400 MPa = 0.5 fs
Shear stress, fs = 800 MPa .. (I)
Eccentrically Loaded Welded Joints
The Joint will be subjected to the following two types of stresses:
1