`

PROJECT WORK
ON
ALUMINO THERMIC WELDING
SKV PROCESS

SUBMITTED BY

SHRI.M.RAVINDRA RAO,ADEN/SWR
&
SHRI.S.RAGHAVENDRA,ADEN/Spl/ASK
ALUMINO THERMIC WELDING
 ALUMINO THERMIC WELDING

CODES & MANUALS

Manual For Fusion Welding Of Rails By Alumino

Thermic Process Revised (2012) up to CS 1

Indian Railway Standard Specification For Fusion

Welding Of Rails By Alumino Thermic Process
Revised (IRS-T-19-2012 up to CS 2)

MANUAL FOR FUSION WELDING OF RAILS BY ALUMINO THERMIC

PROCESS (2012)

SCOPE –
 Method of welding- covers only SKV AT welding technique with short
pre-heating process.

 Precautions & steps to be taken before, during & after welding by short
pre-heating process for achieving satisfactory weld.

 Tolerances of finished weld & acceptance tests.

 List of equipment.

 Record maintenance of A.T. welding.

 Training & certification of welders.

INDIAN RAILWAY STANDARD SPECIFICATION

 FOR FUSION WELDING OF RAILS BY ALUMINO
THERMIC PROCESS (IRS-T-19-2012)

IR Standard covers –

 Technical requirements for thermit portions and welded joints including

various acceptance tests.

 Procedure for approval of Alumino-Thermic “portion manufacturers”

 Procedure for approval of A.T. welding Supervisors, welders & contracting

firms.

 Acceptance tests for in-situ & cess A.T. joints.

 Procedure for approval of alumino thermic portion manufacturers with

upgraded alumino thermic welding technology.

Principles of Thermit Welding and Thermic reaction:

 Alumino thermic process is based on the chemical reaction of iron oxide

and aluminium.

 Reaction is ‘exothermic’ i.e. heat is generated.

 Due to generation of very high heat energy, iron in molten state is

available.

 Equal volumes of molten steel and liquid Al 203 are separated at a

temperature of about 24000C.

 Al203 (slag), being lighter, floats on top of the molten metal.

Thermit Welding and Thermic reaction

 Ferro-manganeseis added to the mixture together with pieces of mild steel
to control exothermic reaction to match wear resistance of thermit steel to
that of the various grades of rail steel to be welded.

 On Indian Railway, Alumino thermic welding with short pre-heating process

called SKV welding is used for welding of rails of different chemistry and
sections.

Advantages of SKV welding

 It is possible to do it at site under field constraints with reasonable quality.

 It is used to weld flash butt panels of 3 rail/ 10 rail/ 20 rail into long panels.

 Most suitable for taking up repair work of fractures and isolated welding.

 No pressure application is required and needs normal surface preparation

compared to other types of welding.

AT welding in Costruction Projects

(Ref: RB letter no. 2011/Tracl-1/5(1)/8 dtd. 13.07.16)

AT welding may be carried out in construction projects with approval

of CAO (Con) in following cases

 Installation of SEJs & Glued Joints.

 Stock joints & lead portions in turnouts.
 Welding of 10/20 rail panels to convert into LWR.
 Dead ends, sidings, loop lines, etc.

For other locations, CAO (Con) to obtain PCE’s approval giving due
justification.

WELDING MATERIALS

 Welding materials required :

 Thermit welding kits
 Welding portions & Sand Mould Units
 Luting sand for luting the moulds
 Igniters-
(Store igniters separate from the welding portions, never store together in the
welding portion containers)
 Multiple-Use crucible/One shot crucible
 Crucible thimbles/ auto thimbles
 Necessary compressor with torch for pre heating

Should available in sufficient quantities and have to be

stored in a secure and dry place.

STEPS IN WELDING

 Rail end preparation

 Rail end alignment
 Mould preparation
 Mould selection
 Mould installation
 Mould packing
 Choice of portion as per rail type and section
 Crucible assembly preparation
 Preheating of rail ends
 Ignition of welding portion in the crucible & Tapping
 Mould waiting and stripping
 Finishing of welded joint

SELECTION OF RAIL
 Rail should be ultrasonically tested.
 Rail wear (head & side ) should be within permissible limits.
 Rail should not be twisted or warped.
 Rail ends should not be hogged or battered.
 Rail should not be corroded.
 Rail ends should not be flame cut.

The height of rail and width of rail head shall not be less than the values as
indicated in Table given below
Rail Normal Min. height Width of head
Min. width of head of
Section height of of old rail of new rail
old rail (as measured
new rail (mm) (mm)
at the gauge corner)
(mm
(mm)

60 kg 172 163 72 66

52 kg 156 150 67 61
90 R 143 139 67 61
75 R 129 126 62 56

60 R 114 112 57 51

 For SH rails, rail ends may be cropped to suitable distance to eliminate

bolt holes and heat affected zone if any.

 No bolt holes within 40mm from the rail ends.

 If rail ends do not have bolt holes, the ends may be cropped to a
distance of 150mm for AT welds and 85mm for flash butt welds
from the center of welded joint to eliminate HAZ.

 Rail shall be free from excessive wear at rail seat, scabs or wheel
burns and corrugations.


MATERIAL : WELDING PORTION

Only RDSO certified/passed portions should be used for welding.

Hygroscopic in nature

Double packing, polythen & cloth bag

Bag should not be damaged or torn,

Portion should not be moist/damp,

Drying not permitted, proper storage

Should be stored in water tight stores kept 0.3m away from wall and
0.5m above Ground to avoid ingress of moisture.
 ‘Acceptance slip’ inside bag by RDSO & RDSO seal on top,
 The ‘portion’ used for welding shall conform to the technical requirements as
mentioned in IRS : T-19-2012.

 Supply only from RDSO approved firms

 Portion to be used must match the rail section, grade of rail and the welding
technique.
 Pouring of portion into the crucible through fingers with a spraying action and
striking the crucible wall so that the bottom plugging remains undisturbed.

WELDING PORTION

Portion should not be mixed with any foreign material or any amount of
additional portion.

 The crucible cap should then be placed in position and an igniter (sparkler)
hooked on to the crucible cap ready for use.
 Particulars of portion contained in the acceptance slip such as Batch No.,
Portion No., Date of Manufacture, etc. should be recorded in a register kept for
this purpose.

WELDING PORTION

 Different main ingredients used in manufacture of AT portion are

(1) Mill scales (2) Aluminum (3) Ferro-manganese (4) Steel chips (5)
Silicon carbide (6) Ferro vanadium (7) Flour spar (calcium fluoride)

The proportion and quantity of the same depends upon the type of rail
section and type of welding and is the trade secrete of the manufacturing
company.

WELDING PORTION shelf life

 There is no specific shelf life for portions. It depends on the quality of

packing and storage conditions.
 If packing is intact and there is no entry of moisture, the portion can be used
even after a long time.
  However, following procedure may be adopted for permitting use of portions
beyond two years after the date of manufacturing :

 (a) One random sample per batch of 300 or part there-of may be drawn from
the portions available in stores.

 (b) The sample shall be tested for reaction test. If the reaction is normal, the
batch represented by the sample can be used without further tests.

 (c) In case the reaction is found to be quiet or boiling, a test joint should be
made from one more sample selected from the batch.

WELDING PORTION

 Following tests should be conducted on the test joints.

(i) Weld Metal Chemistry Test
(ii) Load deflection test

 These tests should be conducted at Zonal CMT’s organisation and/or the

Flash Butt Welding Plant. If the values obtained in above tests are within the
specified values as given in para 4.1 and 4.2.3.1 of IRS:T-19-2012, the batch
represented by the sample can be used otherwise batch should be rejected.

 (d) The rejected portions are to be disposed-off by igniting five portions at a

time in pit away from the store.

 In India, many labour contracting firms are approved by RDSO for executing
AT welding with portion and technique developed by Thermit Portion
Plant(TPP), N. Railway, Luknow,

 Approved firms for manufacturing of portions and execution of welding, are

• India Thermit Corporation Ltd., Kanpur. • Chakradhar Industries Ltd.,

Mumbai • Harshad Thermit Industries, Raipur.
• Sagar Electrical and General Industries, Hyderabad.
• Raybon Metals Private Limited, Bilaspur.
 Material : Prefabricated mould & mould shoe

 Only prefabricated moulds supplied by the RDSO approved portion

manufacturer shall be used for welding.

 Moulds are made by mixing high silica sand to IS: 1987 with sodium
silicate to the required consistency, followed by passage of carbon dioxide
gas.

 These prefabricated moulds shall have adequate permeability for escape

of mould gases and adequate reinforcement to avoid mould crushing
during transportation and welding.

 Moulds shall be handled with due care to avoid any breakage.

 Should be intact, dry & of correct size

 Pouring channels & riser holes should be cleared of any obstruction or

fins.

 Mould shoe fixed with mould should be of correct size & free from
geometric distortions

RAIL END PREPARATION

 The ends should be cropped to eliminate fish bolt holes/HAZ.

 Bent/hogged/battered rail ends to be cut away.
 Cut should be vertical and square

 Rails should be cut using sawing/ abrasive rail cutter only.

CUTTING OF RAILS

PREPARATORY WROK

 Rails should be got tested with USFD.

 Rails should be match-marked to match the rail ends for welding.

 50 mm to be cleaned with wire-brush, kerosene / petrol

 All burrs to be removed

 Rail fastenings for at least five sleepers on either side to be loosened

 Joint sleepers to be shifted to obtain clear working space

 Rails to be aligned – horizontally and vertically

 Any difference in lateral alignment to be kept on non-gauge side

 Vertical alignment with the help of wedges.

ALIGNMENT OF RAILS
 Tolerances at Rail End before welding

Tolerances at Joint before welding

 Gap between Rail Ends
 The two rail ends to be welded shall be held in position with a uniform vertical
gap of 25mm+/-
1mm for normal welding and
 a wide gap of 50±1/75±1 mm for repairing fractured/defective welds.

 The uniformity and verticality of the gap shall be measured by a gauge prior to
welding.

 The gap is measured at four corners of rail section.

 The permissible tolerance in squareness of joint is 0.6mm.

 In LWR/CWR territory, hydraulic / mechanical rail tensor of suitable and

approved design should be used for maintaining correct rail gap during
welding.

 To be rechecked after completion of alignment

FIXING OF MOULD
 To be fixed centrally w.r.t. gap
 After fixing, mould jacket / shoe to be tightened.

 Gap between mould and rail to be well packed with luting sand

 To protect the rail table from metal splashes during reaction, the adjacent rail
surface on either side of the moulds shall be covered with metal cover or
smeared with luting sand up to 15cm on either side of the moulds.

PLACING THE MOULD

 Luting
 It is the process of sealing the gaps of moulds. The material used is called
luting sand.
 After fixing of the mould shoes, luting of the junction of the mould should be
done, starting from the underside of the rail foot and continuing on both sides
towards the head of the rail.
 Luting sand with minimum moisture content (6%) supplied for this purpose only
should be used

 To avoid any sand particle dropping into the mould, a luting cover may be
placed over mould aperture.
 Improper luting may result in leakage of weld metal. It may lead to formation of
a ‘fin’ at the underside of flange which may lead to development of half moon
crack under repetitive loading and may cause failure of the weld.
 Per weld consumption of luting sand is 3.5 to 4.0 kg
 Pre-heating
 Pre-heating is done to remove moisture from surface of rails using torches.

 The rail ends shall be uniformly pre-heated throughout the rail section with
specially designed air petrol/ compressed air petrol/oxygen-LPG burner.

 The burner shall be properly adjusted during preheating to ensure that the
head, web and foot of both the rail ends are heated uniformly to the desired
rail temperature.

 The pre-heating shall be done from the top of the mould box for stipulated
period for welding technique adopted, so as to achieve a temperature of
around 6000±200C.

 Higher temperature will cause metallurgical transformation and therefore

should be avoided.

 Presently, on Indian Railways air-petrol mixture, compressed air petrol

mixture and Oxy-LPG are being used requiring about 10- 12min, 4-5 min &
2-3 min preheating time respectively.
 The pre-heating torches should not be bent or damaged or their holes
blocked.

 Positioning of the pre-heating torch in the mould box must be carefully

adjusted because it affects the quality of pre-heating.

 Recommended pressure should be ensured while pre-heating

 Proper pre-heating of the rail ends consists of fulfilling three

requirements namely:

 Pre-heating equipment
 Pre-heating pressure
 Minimum pre-heating time
  Pre heating equipment

 Air Petrol Mixture

 Compressed Air Petrol Mix
 Oxy – LPG Mix

Preheating pressure
Air-petrol burner - 7 + 0.70 kg/cm2 or 100 + 10 PSI

Compressed Air-petrol – 0.2 to 0.3 kg/cm2

Oxy-LPG Preheating process

Pressure for Oxygen -7.0-8.0 kg/cm2 Pressure
for LPG - 2 to 3 kg/cm2

While preheating with oxy LPG burner, LPG supply should be opened first,
ignited and thereafter oxygen supply should be opened.
While closing, oxygen supply should be stopped first followed by LPG
supply.

Pre-heating
 Minimum pre-heating time

Air-petrol – 10 to 12 min

Compressed Air-petrol – 4.0 to 5.0 min

Oxy-LPG Preheating process – 2.0 to 3.0 min

Control over heating time:By stop watch or by temperature measuring

devices like optical pyrometer, contact type pyrometer or temperature
indicating crayons may be used for measuring rail end temperature.
CRUCIBLE
 Pre-heat before first weld

 Slag to be cleaned after each reaction

 Repair of crucible only with magnesite powder or sodium silicate

WELDING PROCESS

 Hand mix the portion

 Ensure 50 mm gap between tap hole and sand core / top of pouring
gate
 Reaction Time – 20 +/- 3 sec.

 Tapping
 After reaction subsides, allow 3 seconds for separation of slag before
taping.

Mould waiting time

4 to 6 min – 25mm gap joints
12 min – 75mm gap joints
 TRIMMING AND GRINDING
 Mould to be removed after ‘mould waiting time’
 Trimming by weld trimmers only
 Wedges not to be removed for 20 min after stripping
 Risers to be cut after cooling to ambient temperature
 Grinding by profile grinder

 First train to pass after 30 minutes since pouring of weld metal.

 Minimum block period required for SKV welding is 75 mints

FINISHING TOLERANCE OF WELDS

 ACCEPTANCE TEST
 VISUAL INSPECTION
 DIMENSIONAL CHECK

 USFD

SAMPLE TEST JOINT

 ONE OUT OF 100 JOINT RANDOMLY

(AS PER IRS-T-19-2012)

 HARDNESS
 TRANSEVERSE LOAD/DEFLECTION TEST
 POROSITY
 GUARANTEE
 FOR A MIN PERIOD OF 2 YRS

Training and certification of welders :

Separate Competency for

 Welding of 72 UTS & 90 UTS with Std. gap

 110 uts rails
 Wide gap welding

 As per provisions of IRST-19-2012, Specification for Fusion Welding

of
Rails by Alumino Thermic Process,
 Certification of Welders/Supervisors of Approved portion
manufacturing firms shall be done by RDSO.

 Training and Certification of welders/Supervisors of labour

contracting firms shall be done by RDSO.

 Training and certification of Departmental welders and supervisors

shall be done by Thermit Portion Plant (TPP), Northern Railway,
Lucknow and Thermit Welding Centre (TWC), South Central
Railway, Vijayawada as per procedure for certification given in
Annexure-1.
 TRAINING COURCES FOR WELDERS & SUPERVISORS

Category Course Syllabi Periodicity Duration Agency

TW-1 - 2 weeks TPP/TWC

Initial
TM/ Welder
Course

TW-2 1 week TPP/TWC

Refresher Based on
TM/ Welder
Course performance

Course for TW-3 1 week TPP/TWC

JE, SE, Sup. Based on
SSE performance
(P.Way) in field

PROCEDURE FOR TRAINING & CERTIFICATION OF DEPARTMENTAL

WELDERS BY TPP, LUCKNOW & TWC, SCR, VIJAYAWADA Annexure-1

TPP, Lucknow & TWC, SCR,Vijayawada shall impart initial and refresher
training to departmental welders and supervisors for execution of A.T.

welds and issue necessary competency certificates to welders/ supervisors

whose training performance is satisfactory.

 Procedure for awarding Competency Certificates to Welders:

Provisional Competency Certificate:
 The welders whose performance is adjudged satisfactory in initial course
(TW1) shall be awarded Provisional Competency Certificate valid for
executing 100 joints in presence of trained Supervisor.
 Provisional Competency Certificate shall be valid for executing 100 joints or
six months whichever is earlier.

Regular Competency Certificate

 On execution of 100 joints in the field by the Welders or six months from
date of issue of Provisional Competency Certificate, whichever is earlier, the welder
shall be deputed to TPP/TWC along with one test piece (2m long having weld at the
center), USFD testing reports of welds executed by him, working performance
certificate of SSE/SE(P.Way) and relevant welding records as per proforma for
thermit weld register (Annexure -5), duly signed by SSE/SE(P.Way) with counter
signature of concerned DEN/ADEN.
 For the purpose of evaluation the welder should have executed at least 50
welds.

 If the defective weld percentage is less than 1% of the welds executed by the
welder, the results of test weld and the welder’s performance in TW2 course
is satisfactory then the welder will be given regular competency certificate
valid for 2 years.

 In case the welders fails to execute the minimum number of 50 welds within
six months or is not certified successful by the TPP in the above manner, he
shall be treated is incompetent. He will have to repeat the Module TW1 and
the procedure described at Para 4.1.2.1 and 4.1.2.2 above.
 The trained welders shall attend refresher course (TW2) within 2 years of
issue of regular competency certificate.

 In case welders fail to attend the refresher course by the end of validity of
their certificate, their competency certificate shall become invalid.

 The welders who attend TW2 course after expiry of the validity of their
competency certificate but within three years of issue of competency
certificate, will be permitted to attend TW2 course for revalidating their
competency certificate.

 However, welders turning up for TW2 course after 3 years of issue of

competency certificate shall have to attend initial course (TW1) again as
fresher.
LATEST DEVELOPMENTS

 At welding with three piece moulds

 Compressed air petrol preheating system
 Combination joint & different grade rails
 Wide gap (50mm, 75mm) Welding
 One shot crucible
 Self tapping th
 THREE PIECE MOULDS
EQUIPMENT FOR AIR PETROL MIX 52 Kg 90 UTS

M/S ITC, KANPUR

OLD SYSTEM (ABANDONED)

EQUIPMENT FOR COMPRESSED AIR PETROL MIX

 NEW SYSTEM

COMBINATION JOINT

Approved vendors

M/s ITC &

M/s HTI/Raipur

COMBINATION JOINT

COMBINATION JOINTS OF DIS-SIMILAR RAIL SECTONS

The technique for welding combination joints of different rail sections has
been developed for the following sections:

60Kg (90UTS) with

52Kg (72 UTS)
60Kg (90UTS) with
52Kg (90uts)
52Kg (90UTS) with 90R (72 UTS)
52Kg (72UTS) with 90R (72 UTS)

Special pre-fabricated moulds are used for welding combination joints of

dissimilar rail sections.
 The gap between the rail ends is kept between 48-50mm.

WIDE GAP WELDING

The Thermit wide gap (75mm) welding process has been developed to replace
defective welds (Alumino-Thermic, Flash Butt or Isolated Rail Defects). This
eliminates the need to install a fresh length of rail, usually by welding on both
ends. The Thermit portion and the reaction crucible are of a bigger size.

The time for preheating the rail ends are as follows:

Preheating Time
Rail Section With Compressed Air Petrol
With Drum Vapouriser
System
60 Kg. 12 Minutes 4 ½ Minutes
52 Kg. 10 Minutes 4 Minutes
90 R 8 Minutes 3 ½ Minutes

The procedure involves removing the defective weld, aligning and creating a gap
of 75mm ±2mm between the rails and fixing the requisite wide gap prefabricated
mould around the rail gap. The remaining steps are same as the regular SKV
technique. The time forPreheating the rail ends are as follows:

THREE PIECE MOULDS

 SINGLE SHOT CRUCIBLE

SELF TAPPING THIMBLE

 MARKING OF JOINTS
 Each joint shall have a distinctive mark indicating month, year, agency,
welder’s code and weld number of the welded joint.

 This should be done by punching on an aluminium strip of suitable thickness

and dimension of 30 X 100 mm which should be fixed to the web of the rail with
epoxy adhesive at approximately 300 mm from the joint.

 The welded joints shall be serially numbered in a kilometer.

 Repair welds/additional welds done at a later date may be given

continuing weld number in that kilometer.

 For example, the last thermit weld in a particular kilometer was 88 and
subsequently a thermit weld has been executed, it shall be numbered 89,
irrespective of its location in that kilometer.

 PWI shall maintain ‘Thermit Weld Register’ as per program given in

Annexure 5 of Thermit welding manual.

 No punch marking should be done on the rail.

PRECAUTIONS
 Trained welding superviser & welder
 Supervise not more than two welding team
(With in 50 m)
 Portion matching type & chemistry
 End squareness & verticality
 Perfect alignment
 Perfect cleaning of ends

MISCELLANEOUS

 First train after 30 min of pouring of weld metal

 Before passage of train – remove wedges, shift joint sleeper,
pack shifted sleeper
 USFD testing
 Painting of weld collar