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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Introduction,HeavyEngineeringDivision


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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Chapter1,Section1.3


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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Introduction,ProjectManagementGroup


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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Chapter1,Section1.3


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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Introduction,ProjectManagementGroup


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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Chapter2,Section2.1


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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Chapter2,Section2.3


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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Chapter2,Section2.3


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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2.4.1 Types of Heat Exchanger


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Chapter2,Section2.4


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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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


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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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


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


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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Chapter3,Section3.2


(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


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


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


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


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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IntricacyinweldingTi,Weldingenvironment


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


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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IntricacyinweldingTi,PrecautionsforweldingTi


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


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


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


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


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


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


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


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


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


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


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


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 %.


55/82

Chapter5,Section5.1


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


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


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


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


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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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


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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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


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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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


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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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


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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Name Type Min Max

Strain1 ESTRN:EquivalentStrain 1.29906e009

Element:3357

1.26746e007

Element:1922

Part1Study 1StrainStrain1


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Chapter5,Section5.2


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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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


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


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


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


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


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

Shruti Project Report - Intricacies in Fabrication With Ti

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