Megatherm deals in Metal Heating & Melting and possesses the strength to meet Thermal Challenges through Induction. This report is based on the site visit.

1. E.M.T MEGATHERM : A SITE
VISIT REPORT
Soumyodeep Mukherjee
Soumyodeep1312@gmail.com
Abstract
Megatherm deals in Metal Heating & Melting and possesses the
strength to meet Thermal Challenges through Induction. This report is
based on the site visit.

2. Acknowledgement
I owe all my thanks to all the great many people who have
helped and supported me during the training at the company and
finally in making the project.
My deepest thanks to Miss Shaswati Dutta, the regional HR
manager & Miss Manashi Dasgupta without whose
permission the training at the Megatherm would have been
possible.
I would also like to thank my Leader Mr.Sujit Das
Mr. Kamal Bera who had helped me constantly during the
course of the training. He was very friendly and
I express my thanks to Mr. Arup Roy Chowdhury (In charge)
[Panel Section], Mr. Khan (In charge) [Transformer Section];
Megatherm. Thanks and appreciation to the helpful people at
Megatherm, for their support.
I would also like to thank my institution and my faculty members
without whom this project would have been a distant reality.
I also extend my heartfelt thanks to my well wishers.

3. Introduction
Megatherm deals in Metal Heating & Melting and possesses the
strength to meet Thermal Challenges through Induction.
In 1989 as Megatherm sparked-off, Megatherm banked upon
their troupe of Electro Thermal Processing experts and the capital
of experience that Megatherm had gathered since the 1970.
Megatherm made their presence felt across Steel, Foundry,
Forging and various other Metal Working Sectors, surging forward
with spirits held high and the fire burning within.
Today, Megatherm is recognized and preferred by its over-
extending list of Domestic and International Clientele. Their
installations are spread over 40 Countries over the globe.
Megatherm is committed to customer delight and performance
excellence. Megatherm has invested in progressive in-house R &
D which in turn has yielded both profit and praise for the
company. On an aggregate Megatherm have over 1500 satisfied
customers of Electro Heating Equipment till date. Their systems
are incorporated with the best contemporary technology that
ensures optimum utility and comprehensive productivity.
Being certified as an ISO 9001-2000 Company, the name
Megatherm today is synonymous to quality.

4. History:
In 1989, the Company led by its Chief Entrepreneur, Mr.
S. B. Chanda, ventured into manufacturing of "Electric
Induction Melting & Heating Equipments" and started its
maiden journey in the diverse field of Metallurgical &
Metal Working Sectors.
Market:
The Company made deep inroads in almost every metal
sector. It is present in melt shops, be it for Steel or Iron
or Copper or Aluminum, whether an SME or Large
Foundry or an integrated Steel Plant. It is present in
diverse metal working segment, be it forging or rolling,
hardening or tempering, whether Automotive sector or
Defense production or a Critical Engineering Application.
Global Reach:
The Company has made impact in the markets in Europe,
Latin America, Africa, Gulf & CIS Countries, and Saudi
Arab besides South Asian Nations & South East Asia.

5. Installed Capacities:
Company has nearly 1500 installations to its credit all
aggregating to about 8000 MW of Electric ratings out of
which exports account for 250 installations.
Corporate OfficeEMT Megatherm (P) Ltd.
Induction furnace
transformer
Core Coil Assembly

6. Principal Products:
 Induction Melting & Holding Furnace
 Induction Mass Heating Equipment
 Induction Hardening & Heat Treating Equipment
 Medium & High Frequency Induction Heating Power
Sources
Allied Products:
 Electric Arc Furnace
 Ladle Refining Furnace
 Continuous Casting Machine
 Process Control & Automation Equipment
 Transformer
Solution & EPC Contracts:
 Steel Melt Shop Solution
 Foundry Melt Shop Solution
 Forging & Rolling Mill Preheating Solution

7. -: COIL ASSEMBLY :-
1.Cooper Rectangular Tip
2.V cutting at the end surface of the tube
3.Coil capacity wise I.D
1. For 4 Ton – 1000 mm
2. For 5 Ton – 1125 mm
3. For 6 Ton – 1175 mm
(Used 2 Jigs at coil bending in Coil Bending Machine)
4.After bending the coil
5.Coil Checking
6.Putting the coil into Heat Chamber at 880▫C for Strength
Lacking
7.Taking out from the chamber erasing the dust
8.Then Taper Cutting at the end at 45◦
9.Then Marking of the coil is done
10.Drilling of the holes for water supply
11.Adding Copper Rod to flow the water

8. COIL DETAILS OF PROJECT
ALLIANCE INTERNATIONAL
 Capacity – 20 TON J/K Type
 Power – 10000 KW
 Voltage – 40000V
 Frequency – 500Hz
Copper Coil
SS Coil (Bottom)
Sl.
No.
Description Size Unit
1 Coil I.D 1715 mm
2 Coil Section 40x45x5 mm
3 Vertical 40 mm
4 No. of Turn 9 NOS
5 No. of Zone 4 NOS
6 Inter Turn Spacer 9.5 mm
7 Inter Zone Spacer 12 mm
8 No of Water Path 24 NOS
9 Nipple 38 mm O.D
10 Coil Height 1834 mm

9. SS Coil (Top)
Total Coil Height – 2254 mm
The Bar – 75X100 mmlg – 12 NOS
Sl. No. Description Size Unit
1 Coil I.D 1715 mm
2 Coil Section 30x30x3 mm
3 Vertical 30 mm
4 No. of Turn 3 NOS
5 No. of Zone 1 NOS
6 Inter Turn Spacer 30 mm
7 Inter Zone Spacer 30 mm
8 No of Water Path 2 NOS (1 In 1 Out)
9 Nipple 38 mm O.D
10 Coil Height 180 mm
Sl. No. Description Size Unit
1 Coil I.D 1715 mm
2 Coil Section 30x30x3 mm
3 Vertical 30 mm
4 No. of Turn 4 NOS
5 No. of Zone 1 NOS
6 Inter Turn Spacer 30 mm
7 Inter Zone Spacer 30 mm
8 No of Water Path 2 NOS
9 Nipple 38 mm O.D
10 Coil Height 240 mm

10. COIL BASIC INFORMATION
Capacity (KG) 1500
Power (KW) 1000
Rated Voltage (V) 1500
Rated Frequency (Hz) 1000
Coil Design Voltage (V) 1343
Coil Design Frequency (Hz) 634
No of Zone 1
Taping/Coating Coat + Tape
Total Insulation Add Up (mm) 1.50
Stagger/Helical ST
Coil I.D (mm) 730
Coil Height (mm) 900
Charge Dia (mm) 560
No of Turns 14.00
Coil 14
Coil Section:-
Section Height (mm) 50
Section Width (mm) 30
Section Thick in (mm) 5
Depth of Curr Pentra in Cooper Condition(mm) 2.8268
Inter Turn MICA Thickness in (mm) 13
Yoke Area Required (sq. mm) :- 64104
Coil Current (Amp) 6747
Coil Efficiency (%) 82.2860
Capacitor In (MFD) 1253.47

11. Capacitor
Capacitor in 1253.47
Capacitor Number 6
KVAR 3000
Voltage 1500
Frequency 1000
Capacitance/can (MFD) 212.21
Actual Coil Height (mm) 890
Actual Space Factor 1.2714
Coil Q Factor 9.006092066
Copper section
Apparatus used:-
 Drilling machine (Geared drilling machine)
 Punching machine
 Surface grinding machine
 Lathe machine
 Change over switch
 Shaping machine
 Horizontal milling machine
 Vertical milling machine
 Auto band saw machine

12. Static Frequency Converter:
Two types of Frequency converters in use:-
1) Solid state converter.
2) Rotary converter.
Solid State Converter:-
Solid state converter is a combination of a solid state rectifier
(usually bridge or double bridge) into which the input Alternating
Current (AC) of one frequency is changed (Rectified) into Direct
Current (DC).
This DC is supplied to a solid state Inverter which by switching
the DC on and off produces an output AC of the frequency
required.
Rotary Converter:-
Rotary converter is usually only used where large powers are
required, is a combination of a Synchronous Induction Motor into
which the AC supply of a given frequency is fed. The input starts
the motor as Induction and then runs it as Synchronous. (Some
switching device is required) These motor drives an AC generator
at such a speed as to produce the output frequency required.

13.  Thyristor Controlled Rectifiers:
The Megatherm Static converters are the result of development
from experience in solving Induction Heating & Melting problems
for the Industries. Designs have been re-engineered to achieve
easy maintenance, minimum breakdown and operate continuous
operation at full power under all adverse site conditions. A high
availability rate and higher operating efficiency are the salient
features. Megatherm converters are equipped with proven reliable
parallel resonant type Inverters for the entire frequency range.
Depending on power levels and customer's harmonics
specifications converter grade thyristors are employed to build
either and pulse (Single Rectifier), 12 Pulse (Dual Rectifier in
Series) or 24 Pulse (Quad Rectifier in Series) Rectifier assemblies.
Thyristor controlled
Rectifier

14. Megatherm has a separate unit at Salt Lake, Sector- V, where the
construction of PCB takes place. These PCB’s are used for the construction of
several frequency converters. Thus, a series of different types of PCB’s are
developed. Some of them are:-
 Remote KVA Reference Feedback
 Inverter Firing Amplifier
 CT burden Board
 KVA Controller
 Inverter SCR Firing Control Board
 Trip and Metering Board
 Rectifier FA Supply with Shut Down
 Inter Connecting Board
 PSU Terminal Board
 Megatherm Sequence Board
 Burden Board D.C. Current Transformer
 Relay Board
 Mains Failure Shut Down Board
Many other also controller PCB also developed at the megatherm for driving
the power electronic devices (like thyristors, rectifiers, free wheel diodes)
and electric devices (such as di/dt coil, current transformer, fuses, etc.).

15. Transformers
A transformer is a device that transfers electrical energy from one
electrical circuit to another electrical circuit through the medium
of magnetic field and without a change in the frequency. The
electric circuit which receives energy from the supply mains is
called the primary windings and the other circuit which delivers
electric energy to the load is called the secondary windings.
A step-up transformer can be used as a step-down transformer,
in which the secondary of step-up transformer becomes the
primary of step-down transformer. Therefore, by referring to the
windings of a particular transformer, the terms high-voltage
winding and low-voltage winding should be used instead of
primary and secondary windings.
In a transformer, the electrical energy transfer from one circuit to
another circuit takes place without the use of moving parts---it
has, therefore, the highest possible efficiency out of all the
electrical machines and requires almost negligible amount of
maintenance and supervision.

16. Design and R & D
Megatherm started Transformer manufacturing in the year 2007
with an aim to provide Energy efficient Transformers to Furnace &
Other Industrial User.
With in short span of time, Megatherm has supplied 130
Transformers globally for Furnace, Power and other applications
and contributed over 615 MVA in aggregate Transformer capacity.
Megatherm is equipped with Routine Test & Temperature Rise
Test facility as per IS-2026 / 1977, CBIP Spec & BS 171/1570 for
all type of Transformer including 132 kV Class.
Apart from in house test, Megatherm has arranged Impulse &
Temperature Rise Test conducted by Central Power Research of
India (C.P.R.I).
Transformers are designed to meet all the latest national and
international standards, including are, IEC, ANSI, BS, DIN, etc.
All transformers are designed in accordance with customers’
specific requirement.

17. High levels of experience and expertise in transformer
design and regular investment in research and development
has enabled Megatherm to ensure excellence and
competiveness in quality, performance, price and delivery.
Wide range of transformers are tested and validated by
authorized testing laboratories. All materials used are of
best quality and of the class most suitable for working
under the specified conditions withstanding variations of
temperature and atmospheric conditions. Above all, the
design incorporates every reasonable precaution and
provision for the safety of all those concerned in the
operation and maintenance.

18. Product Profile:
Converter Transformers
For Induction Melting / Heating Equipment, AC-DC Drives,
Industrial Rectifier etc. Up to 25 MVA @ 6.6 / 11 / 22 / 33 kV
Class
Electric Arc and Ladle Refining Furnace
Transformers
Up to 20 MVA @ 11 / 22 / 33 kV Class
Distribution Transformers
Up to 5 MVA @ 11 / 22 / 33 kV Class
Power Transformers
Up to 40 MVA @ 33 / 66 / 132 kV Class
Locomotive Transformers
Single & Three Phase: up to 7.5 MVA @ 6.6 / 11 / 22 / 33 kV
Class
CRNGO
Core
Assembly

19. Megatherm’s corporate thinking is driven by the commitment to
quality. The complete in house manufacturing process helps the
company to ensure optimum quality of the transformer.
Megatherm has complete testing facility to test and check all the
major raw-materials used in manufacturing the transformer.
CRGO laminations are cut and annealed in house to achieve
minimum magnetic flux distortion. To ensure the best quality of
the Coils of the transformer, winding wires and strips are also
manufactured in house.
Fabrication section ensures the robustness, quality and fine finish
of the tank and radiators of the transformer.
The manufacturing process of Transformer
covers the following departments:-
 Coil Winding
 Core Assembly
 Core-Coil Assembly
 Tank-up
 Transformer Tank
 Painting & Finishing

20. Coil Winding is of two types:-
 High Voltage Coils:
H.V. Coils are the components of finished transformers. They
are made on automatic layer setting winding machines.
1. A solid cylindrical former of predetermined diameter and length is being used
as base over which is made.
2. Generally round insulated wire of either copper (Cu) or Aluminum (Al) is used
as basic raw material.
3. The coils are made in number of layers.
4. The starting and finishing leads of each coil are terminated on either side of
the coil.
5. These leads are properly sleeved and locked at number of points.
 Low Voltage Coils:
6. L.V. Coils are also one of the components of transformer. The procedure of
making low voltage coil is generally same as described earlier.
7. The shape of the basic raw-material (Al or Cu) is rectangular.
• Coil winding

21. Core Assembly
 The basic raw-material is COLD ROLLED GRAIN ORIENTED
(CRGO)Silicon Steel
 It is in the form of thin sheets & cut to size as per design.
 Generally three different shapes of core laminations are used in one
assembly.
 Notching is performed to increase the magnetic path.
 The laminations are put through annealing process.
 These laminations are assembled in such a manner that there is no
air gap between the joints of two consecutive sheets.
 The entire assembly is done on a frame commonly known as core
channel. These frames being used as a clamping form the support of
the core assembly.

22. Core-coil Assembly
 The components produced in the coil winding and core
assembly stage is then taken into core-coil assembly
stage.
 The core assembly is vertically placed with the foot plate
touching the ground. The top yoke of the core is removed.
The limbs of the core are tightly wrapped with cotton tape
and then varnished.
 Cylinder made out of insulating press board paper is
wrapped on all the three limbs.
 Low Voltage Coil is placed on the insulated core limbs.
 Insulating block of specified thickness and number are
placed both at the top and bottom of the L.V.Coil.
 Cylinder made out of corrugated paper or plain cylinder
with oil ducts are provided over L.V.Coil.
 H.V. Coils are placed over the cylinder.
 Gap between each section of H.V. Coils including top &
bottom clearances is maintained with the help of oil ducts,
as per the design/drawings.
 The Top Yoke is refilled. Top core frame including core
bolts and tie rods are fixed in position.
 Primary and secondary windings are connected as per the
requirements. Phase barrier between H.V. phases are
placed as per requirement.
 Connections to the tapping switch (if required) are made.
 Finally, the component is placed in the oven.

24.  The core-coil assembly and tank supplied by the
fabrication department are taken into tank-up
stage.
The procedure is:-
 The core-coil assembly is
taken out of the oven and the
"Megger test" is carried out.
 Only if the Megger value is as
per the specification, the
assembly may be taken for tank-up.
 The tanks, supplied by fabrication department are brought
to tank-up department duly painted.
 Fittings like drain valves, HV& LV Bushings, conservator,
oil level indicator and explosion vent are fitted in the
tanks.
 The Core-coil assembly is then placed into the tank and
properly locked up.
 Pure filtered transformer oil is filled in the tank to
immerse the assembly only.
 Connections of primary and secondary to the terminal
bushings are made. Operating handle for ratio switch is
fitted, wherever required.
•Tank- Up

25. Megatherm has a state-of-art in-house facility for manufacturing
transformer tanks.
All tanks are made of high quality steel and can withstand
vacuum as specified by the international standards and the
customer. All welds are tested, ensuring 100%
leak proof of seams and mechanical strength.
Transformer with Corrugated Fin-Type radiators
can also be supplied. The fins are manufactured
of Gold-rolled steel. The fin height and length are
according to customer's specifications and fins can be plain or
embossed. All transformer tanks are given a smooth finishing by
using the "SHOT BLASTING" process.
TRANSFORMER TANKS

26. Painting:
The entire procedure of painting is done under two stages:
 Cleaning of tanks
1. The cleaning of tank is done normally by
chipping/grinding.
2. The outside surface of the tank is short blasted to
achieve a very fine and smooth finish
 Painting of tanks
1. After cleaning the tanks, a coat of hot oil resistance
paint is applied on the internal surface of the tank.
2. The outside surface is painted with a coat of Red Oxide
primer and subsequently with one coat of enamel paint
as per customer's requirement.
Paint
Process

28. Each & every transformer undergoes routine tests as per IS: 2026 & IS: 1180,
BS, DIN & IEC requirements.
In accordance with IS: 2026 and IS: 1180 following tests are carried out on
finished Transformer as per sequence.
Megatherm’s provides uncompromising quality to our valued customers to ensure
lasting satisfaction. In addition, supplementary tests are carried out as part of an
internal sampling procedure to ensure continuous quality monitoring.
Necessary field conditions are maintained in the testing lab while testing the
transformers. Special type of tests may also be conducted at an authorized
external lab as per customer request. Megatherm is fully equipped to carry out all
kinds of maintenance work and the service engineers here are well trained to
guide the customer for proper commissioning and handling.
Testing
Transformers
of

29. Routine Test Conducted on all Transformers
1 - Measurement of Insulation Resistance
2 - Measurement of Voltage Ratio and Check of Voltage Vector Relationship
3 - Separate Source Voltage Withstand Test
4 - Induced Over-voltage Withstand Test
5 - Measurement of No Load Loss and Current
6 - Measurement of Impedance Voltage/Short Circuit Impedance and Load
Loss
7 - Measurement of Winding Resistance
8 - Unbalance Current
9 - Oil Dielectric Test
10 - Temperature Rise Test
11 - Air Pressure Test
12 - Vacuum Test
13 - Oil Leakage Test

30. Fittings and accessories as per customer's specification and
drawing are checked.
Transformers are filled with oil up to the minimum level marking,
wherever necessary.
Loose accessories like, earthing terminals, bimetallic connectors;
dial type thermometers are also checked for proper fittings.
Thus, this is how a transformer gets manufactured and it is ready
to be handed over to the customer.
Poly Glass Tape: - The taping material used to bind the core of
the transformer together is intaf poly glass tape. Intaf poly glass
tape is a high strength unidirectional glass binding tape impregnated
and bonded with specially formulated fully catalyzed high
temperature thermosetting polyester resin system. It is more over
very resistant and has high tensile strength and possesses 155 °C
thermal class.

31. Induction Melting & Holding Furnace (Crucibles)
Built in capacities up to 50 Ton, the design offers extremely rugged construction, easy
maintainability, negligible stray heating due to extensive magnetic shielding, high
degree of safety due to optimum grading of electrical insulations, optional accessories
such as Protective Net Guards, Closed Capture Fume Hoods, Stationery Fume
Suctions Rings with Swiveling Lid, Quick Lining Removal Mechanism Pneumatically
operated remote furnace charge over cum isolation switches, Load Cell Arrangement
etc.
The Coil and the magnetic shield are designed using latest Electro-magnetic software
programs. The result is optimum impedance matching with the Power Source and
faster melting rates even with loose initial charges, besides high energy efficiency.
The Structural Designs are based on FEM Software Programs, which consider both
Static and Dynamic load of the charge as well as the Crucible, besides accounting for
the three dimensional electro-magnetic forces.

33. joining
process
permanent
welding
brazing
soldering
temporaray
riveting bolting
welding
electric
TIG
rectifier/generators/
transformer
gas welding
acetylene and
oxygen

34.  TIG: - known as Tungsten Inert Gas welding.
 Mainly done on metals like- stainless steel (ss), aluminum and mild steel
 Specially recommended for thin metals.
 Use non- consumable electrodes.
Rectifier/generator:-
 Uses consumable electrodes.
 Done mainly with ferrous (mild steel).
MIG: - Metal Inert gas welding.
 Uses consumable electrodes.
 Mig wire diameter of 1.2 to 1.6 mm used normally.

35. Heat exchanger
Heat exchangers are used to transfer heat from one medium to another through thin metal
plates which have been pressed into a very special pattern.
A plate heat exchanger is a type of heat exchanger that uses metal plates to transfer heat
between two fluids. This has a major advantage over a conventional heat exchanger in that the
fluids are exposed to a much larger surface area because the fluids spread out over the plates.
This facilitates the transfer of heat, and greatly increases the speed of the temperature
change. Plate heat exchangers are now common and very small brazed versions are used in
the hot-water sections of millions of combination boilers. The high heat transfer efficiency for
such a small physical size has increased the domestic hot water (DHW) flowrate of
combination boilers. The small plate heat exchanger has made a great impact in domestic
heating and hot-water. Larger commercial versions use gaskets between the plates, smaller
version tend to be brazed.

36. The main components of heat exchanger are: -
1. FRAME PLATE & SUPPORT COLUMN: - the two bars are suspended between the
FRAME PLATE- to which in most cases the piping is connected and a support column.
2. CONNECTIONS: - Holes matching the piping lead through the frame plate, permitting
the media to enter into the heat exchanger.
Threaded studs around the holes secure the pipes to the apparatus.
Depending on the application metallic or rubber-type LINNINGS may protect the
edges of the holes against corrosion.
3. CARRYING BAR AND GUIDING BAR: - the cassettes hang from a carrying BAR and are
kept in the line by a GUIDING BAR at the lower end.
4. TIGHTENING BOLTS: - with the package of the cassettes hanging between the frame
plate and the pressure plate, a number of TIGHTENING BOLTS are used to press the
cassettes together, to bring them into metallic contacts, and to seal off the narrow
passages which have now been formed between the cassettes.
5. PREESURE PLATES: - a steel plate called pressure plate is also hung on the carrier bar
and is movable, as are the heat transfer plates. In some cases pipes may be
connected to the pressure plate.
6. CASETTES AND GASKET: - the plates pack consists of cassettes with alternating
welded channels and traditional gaskets channels. Heat is transferred through the
surface which is contained by the weld/gasket, except for some small areas near the
corners. The number of cassettes in the package determined by the size of the heat
transfer surface required.

37. Advantages
 Compactness- The units in a plate heat exchanger occupy less floor space and
floor loading by having a large surface area that is formed from a small volume.
This in turn produces a high overall heat transfer coefficient due to the heat
transfer associated with the narrow passages and corrugated surfaces.
 Flexibility- Changes can be made to heat exchanger performance by utilizing a
wide range of fluids and conditions that can be modified to adapt to the various
design specifications. These specifications can be matched with different plate
corrugations.
 Low Fabrication Costs- Welded plates are relatively more expensive than
pressed plates. Plate heat exchangers are made from pressed plates, which
allow greater resistance to corrosion and chemical reactions.
 Ease of Cleaning- The heat exchanger can be easily dismantled for inspection
and cleaning (especially in food processing) and the plates are also easily
replaceable as they can be removed and replaced individually.
 Temperature Control- The plate heat exchanger can operate with relatively
small temperature differences. This is an advantage when high temperatures
must be avoided. Local overheating and possibility of stagnant zones can also
be reduced by the form of the flow passage.
Disadvantages
 The main weakness of the plate and frame heat exchanger is the necessity for
the long gaskets which holds the plates together. Although these gaskets are
seen as drawback, plate-and-frame heat exchangers have been successfully run
at high temperatures and pressures.
 There is a potential for leakage. The leaks that occur are sent to the atmosphere
and not between process streams.

38.  The pressure drop that occurs through a plate heat exchanger is relatively high
and the running costs and capital of the pumping system should be considered.
 When loss of containment or loss of pressure occurs, it can take a long time to
clean and reinitialize this type of exchanger as hundreds of plates are common
in larger builds.
 The narrow spacing between plates can become blocked by particulate
contaminants in the fluid, for example oxide and sludge particles found in
central heating systems.
 for the reason above most manufacturers will only guarantee their units for 12
months, furthermore replacement plate and gasket sets can be as much as the
plate to buy
CLEANING:-
 GROSS FOULING is mainly caused by the seaweeds, wood chips/fibres, mussels,
barnacles. Mechanical cleaning is done after opening. Soft brush and running water
is used to clean the plates. Back flushing of the unopened heat exchangers can
sometimes be sufficiently effective.
 BIOLOGICAL GROWTH (SLIME)- like bacteria, nematodes and protozoa must be
cleaned using alkaline chemical agents like sodium hydroxide, sodium carbonate,
cleaning effects can be considerably increased by the addition of small quantities of
hypochlorite or agents for the formation of complexes and surfactants.
 INCRUSTATION- SCALING like calcium carbonate, calcium sulphates, silicates can be
cleaned by using nitric acid, sulfamic acid, citric acid, phosphoric acid, complexing
agents (edta, nta) and sodium polyphosphates.
GTAW Welding

39. Gas Tungsten Arc Welding (GTAW) is
frequently referred to as TIG welding. TIG
welding is a commonly used high quality
welding process. TIG welding has
become a popular choice of welding
processes when high quality, precision
welding is required.
In TIG welding an arc is formed between
a nonconsumable tungsten electrode and
the metal being welded. Gas is fed
through the torch to shield the electrode
and molten weld pool. If filler wire is
used, it is added to the weld pool
separately.
TIG Welding Benefits
Superior quality welds
Welds can be made with or
without filler metal
Precise control of welding
variables (heat)
Free of spatter
Low distortion
Shielding Gases
Argon
Argon + Hydrogen
Argon/Helium
Helium is generally added to
increase heat input (increase
welding speed or weld
penetration). Hydrogen will result in
cleaner looking welds and also
increase heat input, however,

40. Hydrogen may promote porosity or
hydrogen cracking.
GTAW Welding Limitations
Requires greater welder
dexterity than MIG or stick
welding
Lower deposition rates
More costly for welding thick
sections
Common GTAW Welding Concerns
We can help optimize your welding process variables. Evaluate your
current welding parameters and techniques. Help eliminate common
welding problems and discontinuities such as those listed below:

41. Weld Discontinuities
Undercutting
Tungsten inclusions
Porosity
Weld metal cracks
Heat affected zone cracks
TIG Welding Problems
Erratic arc
Excessive electrode
consumption
Oxidized weld deposit
Arc wandering
Porosity
Difficult arc starting
MIG Welding
Gas Metal Arc Welding (GMAW) is
frequently referred to as MIG
welding. MIG welding is a
commonly used high deposition rate
welding process. Wire is
continuously fed from a spool. MIG
welding is therefore referred to as a
semiautomatic welding process.

42. MIG Welding Benefits
All position capability
Higher deposition rates than SMAW
Less operator skill required
Long welds can be made without
starts and stops
Minimal post weld cleaning is
required
MIG Welding Shielding Gas
The shielding gas, forms the arc plasma,
stabilizes the arc on the metal being
welded, shields the arc and molten weld
pool, and allows smooth transfer of metal
from the weld wire to the molten weld
pool. There are three primary metal
transfer modes:
Spray transfer (MP3 Audio)
Globular transfer (MP3 Audio)
Short circuiting transfer (MP3
Audio)
The primary shielding gasses used are:
Argon
Argon - 1 to 5% Oxygen
Argon - 3 to 25% CO2
Argon/Helium
CO2 is also used in its pure form in some
MIG welding processes. However, in
some applications the presence of CO2 in
the shielding gas may adversely affect the
mechanical properties of the weld.

43. Common MIG Welding Concerns
We can help optimize your MIG welding process variables. Evaluate your
current welding parameters and techniques. Help eliminate common
welding problems and discontinuities such as those listed below:
Weld Discontinuities
Undercutting
Excessive melt-through
Incomplete fusion
Incomplete joint penetration
Porosity
Weld metal cracks
Heat affected zone cracks
MIG Welding Problems
Heavily oxidized weld deposit
Irregular wire feed
Burnback
Porosity
Unstable arc
Difficult arc starting

44. Bibliography
Websites:-
 www.megatherm.com
 www.google.com
 www.ask.com
 www.amazon.com
Books:-
 Electrical Machinery (P.S. Bhimbra),
 Electrical Machines (J.B. Gupta)
 Workshop Technology(Hazra, Chowdhury)
 Design and manufacturing of Hydraulic Presses(Q.S.
Khan)
The additional information has also been gathered
from the employees of Megatherm.