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GOVERNMENT OF
INDIA
MINISTRY OF
RAILWAYS
MANUAL
FOR
FLASH BUTT
WELDING OF RAILS
1996
RESEARCH
DESIGNS AND STANDARDS ORGANISATION
LUCKNOW-226011
MANUAL FOE FLASH BUTT WELDING
OF RAILS
FOREWORD
On Indian Railways, Alumino
Thermic (A. T.) Welding, Flash Butt (Electric Resistance) Welding and Gas
Pressure Welding processes are presently in use for welding of rail
joints.
Flash Butt Welding is being done on Zonal Railways
departmentally, using Stationary Flash Butt Welding Plants of different
makes. Mobile Flash Butt Welding Plants, capable of in situ Flash Butt
Welding of rail joints, are also in operation on some of the Zonal
Railways.
The Code of Practice for Flash Butt Welding of Rails
(tentative) was issued in January, 1972. Revision of this Code is being
made to cover procedures for Flash Butt Welding of heavier and higher
strength rails now used on Indian Railways and to incorporate the latest
practices. This Code of Practice is being renamed as "Manual for Flash
Butt Welding of Rails".
MANUAL FOR FLASH BUTT WELDING
OF RAILS
1. SCOPE
1.1 The manual gives details of the types and
suitability of rails to be welded by stationary Flash Butt Welding
Plant prewelding inspection, preparation of rail ends before
welding, the general procedure of execution of welding and finishing
of welded joints. It also defines geometrical tolerances for the
finished joints and acceptance tests to ensure quality
control.
1.2 Weld parameters for different rail sections/ chemistry
have been prescribed by manufacturers and are unique to the particular
welding plants. Should any change in these parameters be considered
necessary, the same may be carried out in consultation with
RDSO.
2. SELECTION OF RAILS TO BE WELDED
2.1
SECTION OF RAILS : Capacity of the individual plant will determine the
heaviest section and type of rail that can be welded. New as well as
released but serviceable rails of same type (section and metallurgy) shall
only be welded together. Welding of rails of different sections metallurgy
shall not be attempted. It is preferable that rails, rolled by the same
manufacturer are welded together. Minimum length of old but serviceable
rails for welding shall be 6 metres.
2.2 WELDING OF OLD RAILS
: While welding old rails, it shall be ensured that only serviceable
rails are welded. Old rails to be welded shall preferably be match marked
before releasing from track to achieve maximum uniformity of profiles in
weld zone.
2.3 FISHBOLT HOLES : Welded panels (10/20 rails)
for laying long welded rails shall, as far as possible, be without
fishbolt holes. If drilling of fishbolt hole is necessitated for the
purpose of handling during end unloading, only the second fishbolt hole
(one away from the rail end) need be drilled. In case, welding of new
rails with fishbolt holes cannot be avoided, it shall be ensured that the
outer edge of the hole nearest to the rail end is at least 40 mm away from
the end to be welded to avoid the heat affected zone of the weld extending
upto the edge of the hole. Ail fishbolt holes shall be chamfered before
welding.
2.3 1 Ends of old rails with fishbolt holes/bond wire
holes shall be cropped by a minimum length of 450 mm before
welding.
2.4 ULTRASONIC TESTING OF RAILS TO BE WELDED : New
and old but serviceable rails shall be free from internal defects. In the
case of new rails, the ultrasonic testing is required to be done at the
rail manufacturer's premises. Old but serviceable rails shall invariably
be tested ultrasonically before they are taken to Flash Butt Welding
Plants.
3. SUITABILITY OF RAILS FOR
WELDING
3.1 OLD
RAILS
3.1.1 Defective rails :
Rails having cracks or other defects such as heavy corrosion pits or which
are worn by more than 2 mm depth at rail seat shall not be
welded.
3.1.2 Permissible vertical wear of rails to be welded
: The vertical wear in old rails to be welded [measured as per para
302 (b) (iii) of Indian Railways Permanent Way Manual] shall be within the
limits specified below : —
| Rail
Section |
Standard height of the
new rail |
Minimum height of worn
rail |
| 60 kg |
172.00 mm |
164 mm |
| 52 kg |
156.00 mm |
150 mm |
| 90 R |
142.88 mm |
139 mm |
| 75 R |
128.59 mm |
126 mm |
| 60 R |
114.30 mm |
112
mm |
3.1.3 Permissible lateral
wear of rails to be welded : Old rails to be
welded shall preferably show similar pattern of side wear and the minimum
width of rail head shall be as specified below
:—
| Rail
Section |
Standard
width of the head of new rail |
Minimum
width head of old rail |
| 60 kg |
72.00 mm |
66 mm |
| 52 kg |
67.00 mm |
61 mm |
| 90 R |
66.68 mm |
61 mm |
| 75 R |
61.91 mm |
56 mm |
| 60 R |
57.15 mm |
51
mm |
3.1.4 Rails with cyclic
wear shall not be welded
3.2
DIFFERENCE IN HEIGHT OF RAIL ENDS TO BE WELDED : The individual rail
ends for new rails may have a maximum difference in height of 1.2 mm at
the welded joints. Rails manufactured by SAIL with dispensations (having
letter 'D' in the rolling mark), may have a maximum difference in height
of 1.5 mm. This is illustrated in Fig. 3.2. The difference in height shall
be transposed to the foot of the rail.
3.3 DIFFERENCE IN WIDTH
OF RAIL HEADS TO BE WELDED
3.3.1 The difference in the width of
rail heads of two rails to be welded shall not exceed 1.0 mm for new and
2.0 mm for old rails. New rails manufactured by SAIL with dispensations
(having letter 'D' in the rolling mark) may have a maximum difference of
1.5 mm in the width of rail heads. For new rails, it is preferable to
restrict the difference in width of rail heads to 0.5 mm by adopting
procedure laid-down in para 4.2.
3.3.2 Any difference in the widths
of rail heads at the welded ends, in case of both new and old rails, shall
be transposed to one side of the head keeping the other side as perfectly
aligned as practicable. The aligned side of such welded panels, shall be
distinctly marked. To facilitate pairing of panels, aligning on operator
side as well as non-operator side may be resorted to .
3.4 RAIL
END GEOMETRY : Rail ends to be welded shall meet following geometrical
standards :—
(a) End-bends in the vertical plane not greater than
0.7 mm on a 1.5 metre straight edge [Fig. 3.4(a)]. Sagging ends not
permitted.
(b) End-bends in the horizontal plane not greater than ±
0.7 mm on a 1.5 metre straight edge [Figs. 3.4 (b) & (c)].
(c)
Deviation of the end from the square not greater than ± 0.6 mm [Fig. 3.4
(d)].
3.5 A thorough inspection shall be carried out at the
plants with a view to avoid welding of rails with visible surface detects
such as rolling/guide marks, wheel burns etc.
3.6 The rails
rejected due to non-compliance of the requirements of paras 3.1 to 3.5
shall not be welded. Such rails shall be marked and stacked separately for
other uses.
4. PREPARATION OF RAILS TO BE
WELDED
4.1 PRE-STRAIGHTENING OF RAILS : Rails not
meeting the geometrical standards stipulated in clause 3.4 are to be
rectified before welding using a pre-straightening machine so as to
conform to the standards.
4.2 In order to minimise the
difference in head width of rail ends to be welded, actual head width of
rails shall be checked using template shown in Fig. 4.2(a), (b) & (c).
The deviations shall be marked on the rail head so that rails with same or
minimum relative deviations are selected for welding.
4.3
END-CLEANING: Before welding, end faces of the rails to be welded and
electrode contact locations shall be thoroughly cleaned of loose scales,
rust, paint etc. by brushing and shot blasting/grinding. Cleaning of rail
bottom shall be ensured by placing a mirror and watching the cleaned
surface. The electrode contact locations should be marked with chalk on
each rail end to be welded to serve as guidance for cleaning. Oil and
grease, if; present, shall be removed by Carbon Tetrachloride or Benzene.
If any internal defect such as piping is noticed during end cleaning, the
rail shall not be welded.
5. PROCEDURE OF WELDING OF
RAILS
5.1 ELECTRICAL CONTACT : The electrical contacts,
i.e., Copper/ Melloroy electrode in the welding machine must be cleaned by
compressed air pistol to ensure freedom from loose oxides and other
foreign matter so that no arcing takes place at the contact points on the
rail and to eliminate the possibility of rail failure near joint due to
Copper penetration and formation of brittle martensite structure. The
electrodes must be replaced and machined whenever surface depressions
exceeding 1 mm in depth are formed due to wear. For this purpose, adequate
spare electrodes should be kept in the plant.
5.2 RAIL ALIGNMENT
: The running surfaces of rails at interface shall be aligned
carefully to avoid any 'Step' defect except as provided in para 3.3.2, the
gauge face corner generally being the reference line.
5.3
WELDING SEQUENCE : The Stationary Flash-butt Wilding Plants adopt
following , welding sequence :—
-Aligning (along with detwisting,
if possible).
-Initial burn off.
-Preheating.
-Flashing.
-Forging (upsetting).
-Stripping.
The mobile
Flash butt welders, however, give continuous flashing instead of initial
burn off, preheating and flashing cycles separately.
Air pressure
and voltage/current recommended by the manufacturer must be ensured
throughout the welding cycle.
5.3.1. Initial, Burn-off :
Relevant to the specifications of rail and welding machine, controls
shall be adjusted so that at the end of this phase weld interface has good
overall contact.
5:3.2 Preheating :—The rail ends are
brought into contact to allow a low voltage high amperage current flow
which preheats the rail ends. Lower voltages are preferred to minimise
crater damage on the rail ends. The movable rail is alternatively moved
backward and forward producing a series of electrical contacts with the
fixed rail end. The objective is to heat the rail faces uniformly by
flashes upto the red. hot stage. The rail ends are brought in and out of
contact for certain duration a number of times depending on the
specifications of the welding plant, the section and the metallurgy of the
rail. This pre-heating cycle executed in a fully controlled automatic mode
once the parameters are selected.
5.3.3 Flashing:-Flashing,,
consists of moving the rail in continuous manner initially at a fixed
speed but during the last few seconds, at an accelerated rate. The
flashing speed is so arranged that the rail ends bum off without short
circuiting or giving rise to an open circuit condition.
5.3.4.
Forging (upsetting) : Immediately following flashing, the platten
movement is accelerated so that the rail ends are butted together to a
stage of fusion under a heavy butting force whose magnitude depends on the
make of the welding Plant. The welding current automatically gets cut off
during the later part of the forging operation. The joint should be left
undisturbed in damped position for ten seconds after the welding
cycle.
5.3.4.1 The recommended butting pressure for
different types of rails is indicated below ;—
—72 UTS
rails—5kg/mm2 on cross, sectional area.
—90 UTS rails
& Head Hardened rails—6 kg/ mm2 on cross sectional
areas.
—110 UTS rails—7 kg/mm2 on cross section
area.
The heaviest rail section which can be welded of plant should
be decided on this basis.
Welding of higher UTS and higher section
rail; on low butting load plant by increasing the number of
pre-heats causes very pronounced heat affected zone (HAZ) and is
detrimental to. the service life of the joints.
5.3.5
Stripping
(i) Automatic stripper : A stripper, Which may be
integral with the welding plant or installed either just adjacent to
welding machine or at 13/26 m distance from it, shall strip the hot upset
metal all round the rail section in such a way that minimum grinding. is
required to achieve final finished profile at weld.
(ii) Manual
removal of upset metal : Wherever automatic stripper is not installed,
manual chipping using pneumatic chisel may be adopted. Recommended width
of flat chisel is 50 mm for removal of upset metal from junction of head
& web and web & foot of the rail, half round chisel should be
used. Care should be taken to ensure that chipping does not create any
notches or under cutting. However, hot upset metal all round the rail
shall be stripped.
5.4 POST WELD HEAT TREATMENT : 72 UTS and
90 UTS rails do not require any special post weld heat treatment. However,
alloy steel rails of 110 UTS and head hardened rails need post weld heat
treatment to ensure variation in hardness within acceptable limits in heat
affected zone. Typical post weld heat treatments for 110 UTS alloy steel
rails and head hardened rail are given in, Annexure I & II
respectively.
5.5 WELD PARAMETERS: Welding parameters will
depend on section and metallurgy of rail to be welded and they shall be as
per manufacturer's recommendations or as fixed by
RDSO.
5.5.1 Changing weld parameters arbitrarily like
changing platten travel, increasing duration and/or number of preheat
cycles so as to increase interface temperature to achieve fusion with
lower butting pressure (wherever butting capacity of the plant is low) or
to retain heat in weld for easy upset metal removal when stripping is done
away from welding machine, shall strictly be prohibited.
6.
RECORD OF WELDS : Record of all the joints shall be maintained in a
register as per proforma as Annexure III. The register shall be signed
daily by the welder at the end of the shift and shall be verified and
.countersigned by the supervisor incharge. For those welding plants which
are equipped with Automatic weld recorder, the chart of the weld recorder
shall be analysed every day with respect to voltage, current, upsetting
force and platten travel for each weld. Any parameter not conforming with
the standard parameter should be set right. The chart shall also be
preserved in addition to the register to facilitate investigations in case
of defective joint and joints failing in service.
7. POST WELD
STRAIGHTENING : A post straightening machine shall be installed at
suitable distance from the welding machine for straightening the joint if
required to achieve required geometrical tolerances in vertical/lateral
alignment.
7.1 WATER COOLING : It is desirable to do post
weld straightening after the weld has cooled down to ambient temperature.
Water spray cooling shall be done at such suitable distance from the
welding plant where the temperature of the weld is not more than 350
degree Celsius which normally is achieved in 7-8 rail length.
8.
FINISHING : The top, side and bottom surfaces of the rail head shall
be ground smooth so that the weld surface is absolutely flush with the
parent rail surfaces. Particular care is necessary to ensure that fish
grinding does not bum or notch the rail surfaces. After grinding, the top
table and the sides of the rail head shall comply with the geometrical
standards given in Annexure IV. Grinding shall be done preferably using a
profile grinding trolley, in the absence of which manual grinding can be
done using a cup grinder. Depending upon whether it is done mechanically
or manually, grinding may be done in stages.
9. MARKING OF
JOINTS: Every joint shall have distinctive mark indicating the weld
number, month and year of welding and the code of the plant as shown
below. This should preferably be done by punching on an Aluminium strip
which should be fixed to the web of the rail with suitable epoxy adhesive
beyond 300 mm from joint.
XXXX MM YY AAA
The first
four digits indicate the weld number starting from 0001 for rust weld of
every month, the next two digits month of welding followed by last two
digits of the year of welding. The letters in the end shall be code of the
Welding Plant. For example, 32810891 MGS indicates that the particular
weld is 3281st weld of August 1991. of Mughalsarai Flash Butt Welding
Plant.
10. TESTING OF WELD : It shall be the responsibility,
of the Plant in-charge and the quality control supervisor to device
adequate stage inspections before final acceptance tests are conducted.
Causes for failure either of weld or in heat affected zone at any stage in
production shall be investigated and corrective action taken before
regular welding is continued. Some common causes for failure and the
precautions to be taken are listed in Annexure-V for guidance. Acceptance
test comprises of all the weld being checked by visual inspection,
dimensional tolerances and ultrasonic test. Sample welds should be subject
led to transverse bending test and detailed metallurgical tests in a
laboratory as a quality assurance measure. Results of ail the tests shall
be maintained' in register by the plant in-charge assisted by quality.
control supervisor. Details and method of conducting the tests are as
follows:—
10.1 TESTS FOR EVERY
JOINT
10.1.1 Visual
inspection: After finish grinding, all welds shall be visually
inspected for possible cracks, lack of fusion and other surface defects
like notching, damage in heat affected zone etc Welds with visible defects
shall be rejected.
10.1.2 Dimensional check : All welds
shall be inspected using standard 1 m and 10 cm straight edges and feeler
gauges, as shown in figure 8 (a) to 8 (j) for compliance of geometrical
standards as given, in. Annexure-IV. Welds not meeting these standards,,
if rectifiable by grinding, can be re-ground, failing which they shall be
rejected. Results shall be maintained as per proforma. given in
Annexure-VI 'A'.
10.1 .3 Ultrasonic Test ((USFD) : All welds
shall be subjected to ultrasonic testing for detecting presence of
internal defects in the weld. This test can be done by installing an
on-line USFD equipment or as an interim measure manually with portable
USFD machine. Entire cross section of the rail i.e. head, web and foot
shall be tested by trained personnel following the procedure laid down in
Annexure-VII for USFD test of weld to detect internal flaws. Welds having
defects shall be rejected. Results shall be maintained as per proforma
given in Annexure VI 'B'. Defective' joint shall be distinctly marked and
panels with defective joints shall be separately stacked. The defective
joint shall be cut and removed before the panel is despatched from the
Flash Butt Welding Plant. Another panel of matching length should be
welded and the short panels (minimum 3 rail lengths) despatched in
pairs.
10.2 TEST ON SAMPLE JOINT : Sample test joints shall
be made on pieces of rails of similar section and conforming to the same
specifications as the rails being welded. The length of each piece shall
not be less than 750 mm. Following tests shall be carried out on sample
test joint frequency of test is indicated in Table I. These test shall
also be carried out whenever there is a change in type of rail being
welded. In case a sample joint does not comply with the requirements of
the test, two more sample joints will be made and tested. If both the
sample joints meet the requirements of the tests, welding may continue. In
case of failure of any of the retest joints, RDSO should be consulted for
investigation and fixing revised welding parameters.
10.2.1
Hardness Test: Brinnel hardness test shall be conducted on the test
weld sample before conducting transverse load test. The hardness value in
HAZ shall not vary from the hardness of the parent rail by more than 20
HB. Results shall be maintained as per proforma given in Annexure-VI
'C.'
10.2.2 Transverse Test: The finished test weld samples,
not less than 1.5 metre long with the weld at the centre shall be
subjected to transverse load test in a transverse testing machine in the
following manner :—
10.2.2.1 The test joint shall be
supported on cylindrical or semi-cylindrical supports having a diameter of
30 to 50 mm and distance of one metre between them. In case of 60kg 110
UTS/head hardened rail joints the test span shall be 1.25 metre. The
mandrel diameter shall be between 30 to 50 nun. The mandrel axis should be
perpendicular to the horizontal axis of the rail section and it should be
positioned at the centre of the weld. The weld shall be in the centre of
the span and loaded in such a manner that the foot of the rail is in
tension. The load shall be uniformly and gradually increased. The rate of
application of the load should not exceed 2.5 tons/sec. The test joints
shall withstand the minimum load and shall show minimum deflection as
given in Table 1 without showing any signs of cracking or failure.
The minimum deflection values are corresponding to stipulated minimum
loads. Results shall be maintained as per proforma given in Annexure-VI
'D'.
VALUES OF MINIMUM BREAKING LOAD AND INFLECTION IN TRANSVERSE
LOAD TEST
10.2.3 Macro
examination One test joint for ever 5000
joints welded shall be subjected to macro examination. 150 mm length of
rail with weld at centre shall be cut and the sample shall be sectioned in
vertical longitudinal direction through the weld. One of the
sections shall be etched with 5—10% Nitric and also subjected to
mangnaflux test to ensure freedom from cracks, lack of fusion or oxide
inclusion Extent of heat affected zone shall be measured for head, foot
and web of the rail. Results shall b maintained as per proforma at
Annexure-VI 'E'.
11. HANDLING OF HIGH STRENGTH RAIL (90 UTS, MI
AND 110 UTS)
11.1 The 90 UTS head hardened and 110 UTS rail are
comparatively brittle having less fracture thought ness as compared to 72
UTS (MM) RAILS. There fore, such rails require special care in handling.
visional guidelines for handling and maintenance such rails are given in
Annexure-VIII. Flash Welding Plants shall create adequate handling
facility to follow these guidelines.
12. CHECK LIST FOR FLASH
BUTT WELD1N PLANTS
A check list containing items to be checked
daily and weekly is placed at Annexure-IX. This she list should be
followed meticulously as a quality ass lance measure.
Annexure
(Para 5.4)
POST WELD CONTROLLED
COOLING TREATMENT FOR 110 UTS ALLOY STEEL RAILS
The rails being 60 Kg. Cr-Mn alloy steel rails are
required to be subjected to controlled post weld cooling treatment, as
detailed below, so as to avoid formation of undesirable micro-structure
and cracks in weld and HAZ.
(i) Asbestos cement pipe of internal
dia. 250—300 mm, wall thickness 15 to 25 mm and length not less than 1
metre shall be installed after the flash butt welding machine along the
welding line. Necessary arrangement to roll the rail through this pipe
shall be made so that the pips walls are not damaged due to movement of
rails. Two holes of 30mm dia. (to suit the burner head of the kerosene
blow lamp) on the horizontal diameter are to be made as shown in Fig.
5.4(a), in such a way that the holes are staggered by 25—30 mm with
respect to the mid length of the pipe. Two nos. kerosene blow lamps of
about 1.5 liters capacity .ire fixed through these holes in such a way
that flame from the burners strike at the centre of the web on each side.
The air pressure in the burners is to be adjusted in such a way that blue
flame is always available from these. Asbestos cloth/Asbestos lined mild
steel gadget are to be always kept ready to cover both the ends of the
pipe, to the extent possible so that cool air draught is not allowed to
enter inside the pipe. The blow lamp burners are kept in 'ON' position at
least 10 minutes before the flash butt welded joint enters the pipe to
ensure warming up of the pipe and the enclosed air pocket to retard the
rate of cooling.
(ii) After stripping, the welded joint should be
quickly moved forward and brought exactly at the mid length of the A.C.
pips. This operation is to be completed within 120 seconds of butting. At
this time, the temperature of tile weld is generally above 850 degree C.
Depending upon the travel speed of the rail panel, the mid length of 1he
pipe may be located at about 13m (rail
length) from the welding head to facilitate setting up of the next rail
joint to be welded during the period the rail joint already welded is
being slowly cooled. The flash butt welded joint shill be kept inside the
A.C. pipe for not less than 10 minutes till the weld temperature drops to
about 400—450 decree C. Two standby kerosene Wow lamp burners in perfect
working condition shall be kept ready to be utilised in case of
necessity.
Annexure-II
(Para
5.4)
POST WELD AIR QUENCHING
TREATMENT FOR FLASH BUTT WELDING OF 60 Kg MEAD HARDENED
RAILS
During welding of head hardened
rails using the normal welding procedure. the average hardness of the HAZ
of the rail becomes,. considerably less than the parent rail
hardness This lower hardness is due to transformation of rail steel
occurring at a cooling rate much lower than that archived during the
original head hardening operation. Such a hardness difference can lead to
differential plastic deformation during wheel-rail contact which may cause
localized cupping on the running surface at the welds.
Head
hardened rails, therefore, must be subjected to controlled cooling
treatment (slack quench) to improve the sagging heat affected zone
hardness.
A fabricated air quenching gadget as shown in Figure 5.4
(b) shall be used for enhanced cooling of the rail joints made with head
hardened rafts. The length of this gadget is approx. 250 mm and width 190
mm. There are series of drilled holes of 3 mm diameter in the gadget and
their position is shown in figure. The gap maintained between the inner
faces of in. gauge' is approx. 120 m which will enable gap of approx. 25mm
between the railhead side surfcasting the gadget. This will result in
efficient application of air quenching jet. Within one minute of wedding
air quenching should be carried out while the rail surface temperature is
in the region 900—950° C. The air pressure should be approximately
2kg./cm2 and duration of application should be about 1
minute.
Annexure - III
(Para
6)
RECORD OF
WELDS
MACHINE — — — —
1. Date of
welding
2. Shift (day/night)
3. Joint No.
4. Length
of rail
5. Section of rail
6. Welding current Primary,
amps)
7. Primary voltage (volts)
8. Clamping
pressure
9. Butting pressure Kg/cm-
10. No, of
pre-heats
11. Pre-heating time On....
Off...............
12. Burn off time (secs.)
13. Flashing
time (secs.)
14. Post welding heat treatment if any
15.
Whether automatic weld recorder chart available
16. Remarks (Any change of voltage
during welding etc.)
17. Signature of welder
18. Signature
of Foreman
Annexure-IV
(Para
8)
FINISHING TOLERANCES FOR
WELDS
|
A. Welds with new rails |
| (i)
Vertical misalignment |
±0.3 mm at the
centre of a 1 m —0 mm straight edge. |
| (ii) Lateral misalignment |
± 0.3 mm at the
centre of a 1 m straight edge. |
| (iii) Head finishing (in. Width) |
Side of rail head
should be finished to :— |
| . |
±0 25 mm on gauge side at the centre of 10 cm
straight edge |
| (iv) Finishing of top table surfaca |
± 0.2 mm at the
centre of 10 am — 0 mm straight edge. |
| (v) Web zone (under side of head, web, top
of base, both fillet each (ide). |
± 3.0 mm of the
parent centre — 0 mm |
| (vi)
Underside of rail foot shall be suitably finished without any
minus tolerance to ensure proper seating on sleepers and unhindered
movement of welded panels on end unloading rakes. |
| NOTE :
Tolerances for BSP rail rolled as per Explanatory Note to
IR.3T-12/1988 shall be as under :— |
| (a) Vertical misalignment |
+0.4 mm at the
centre of —0.00 1 m straight edge |
| (b) Lateral misalignment |
± 0.4 mm
-do- |
|
B. Welds with old
rails |
| (i)
Vertical misalignment |
±0.5 mm at the
centre a 1 m straight edge. |
| (ii) Lateral misalignment |
±0.5 mm at
the centre aim straight edge. |
| (iii) Head finishing (on sides) |
±0.3 mm on
the gauge side at the centre of a 10 cm straight edge. |
| (iv) Head finishing (on top table
surface) |
±0.2 mm at the centre of a 10 cm straight
edge. |
| (v) Web zone (under side of head, web, top of
base and both fillets on each side) |
+ 3.0 mm 0.0 mm
of parent contour |
Annexure V
(Para 10)
PRECAUTIONS TO AVOID DEFECTS
IN FLASH BUTT WELDED RAIL JOINTS
Following precautions shall be
taken to avoid defects in the welded joints :—
1. Oxide
inclusion—The rail end faces and the adjoining surface of the rail profile
to a width of about 25mm all round shall be cleaned properly by portable
grinders or blushing machine or shot blasting to remove loose scale, rust,
scabs, dust, paint etc. Oil and grease, if present shall be removed by
Carbon Tetrachloride or Benzene.
2. Lack of fusion—Preheating cycle
and time, flashing and butting stroke as standardised shall be strictly
maintained during welding to avoid this defect.
3. Poor joints due
to defect in rails—Rail ends having cracks and other visible rolling
defects should be cropped before welding.
4. Notches and chisel
marks adjacent to the weld joints—During stripping by chiseling and
finishing by grinding, care should be taken that notches, dents or chisel
marks are not formed on the rail surface as such flaws may act as stress
raisers in service leading to premature failure.
5. Copper
penetration/arcing on rail foot bottom surface—During flash butt welding,
the two copper blocks (electrodes) below the rails get worn out and
grooved/ dented due to rail movement. Besides this, after the
flashing/burning off operations, lot of loose oxides of metal are
deposited on the copper blocks. Due to the above reasons, current flow
between the rail foot surfaces and the copper block is not continuous
resulting in arcing 'and formation of local melting/denting and even
copper penetration at the rail foot surface. Such affected area results in
premature fracture. Therefore, after each operation loose oxide/metal
shall be cleaned by brushing the copper block surfaces and the copper
blocks shall be periodically reconditioned or replaced with new
ones.
6. Use of treated water for cooling system—The pipes/ tubes
for circulation of water for cooling purpose are, generally, of
small diameter. Due to presence of impurities in water, scaling on the
inner side of the pipe takes place resulting in less circulation of
cooling water and consequent problems. Therefore, suitably treated
water should be used for cooling system. The welding plant should
not be operated if the cooling system is nonfunctional.
Annexure-VIA
(Para
10.1.2)
DIMENSIONAL CHECK OF WELDED
JOINTS (AFTER FINISHING)
1. Date, month &
year
2. Joint No.
3. Rail section
4 1 m straight edge
Top LH RH
5. 10 cm straight edge Top LH RH
6
Remarks
7. Signature
8 Summary — (at the end of the
month)
No. of joints welded during the month (Rail
section-wise)
No. of joints checked (Rail
section-wise)
No. of joints rejected (Rail section-wise)
Annexure-VI
B
(Para 10.1.3)
ULTRASONIC TESTING OF WELDED
JOINTS
Date/Month/Year/Name of Operator
Welding Machine USPD'
1. Joint No.
2. Rail section &
chemistry
3. Day Night shift
4. Result of testing
5.
If defective, details of flaw
Defective zone Flaw peak
pattern
Head/Web/Foot Probe
Trace
6. Remarks
7. Signature
Summary (at the end of the
month)
No. of joints welded during; the
month (Rail section-wise)
No. of joints tested (Rail
section-wise)
No. of joints found defective
(Rail section-wise)
Annexure-VIC
(Para
10.2.1)
HARDNESS TEST OF WELDED
JOINTS
1. Date, month and year
2.
Joint No.
3. Rail section & UTS
4. Hardness
(BHN)
Parent rail
Weld metal
Heat affected
zone
5. Remarks
6. Operator's signature
Summary (at the end of the
month)
No. of joints welded during the month (Rail section
wise)
No. of joints tested (Rail
section-wise)
No. of joints rejected (Rail section-wise)
Annexure-VI
(Para
10.2.
TRANSVERSE TESTING OF WELDED
JOINTS
1. Date, month and year
2.
Joint No.
3. Rail section & UTS
4. Machine on which
welded
5. Load applied (Tonne)
6. Deflection (mm)
7.
Span (m)
8. Broken or not
9. Remarks
10.
Signature
8. Summary — (at the end of the month)
No. of joints welded during the
month
(Rail section-wise)
No. of
joints tested (Rail section & UTS-wise)
No. of joints failed (Rail section
& UTS-wise)
Annexure-VIE
(Para
10.2.3)
MACRO EXAMINATION OF WELDED
JOINTS
1. Date, month and year
2.
Joint No.
3. Rail section
4. Machine on which
welded
5. Extent of head affected zone (mm)
Head
Web
Foot
6. Result of visual
examination
7. Remarks
8. Signature
Annexure-VII
(Para
10.1.3)
PROCEDURE FOR ULTRASONIC
TESTING OF FLASH BUTT WELDED RAIL JOINTS
1. Synopsis
: This procedure has been prepared to test
flash butt welded rail joints to examine the presence of weld unsoundness
using USK-4 of M/s. Kraut Kramer, UFD 6251 of M/s. ECIL, ESM2MRT of M/s.
Electronic Engineering Co., USFD 301R of M/s. Vibrancies Pvt. Ltd and
similar kind of ultrasonic flaw detectors.
2.
Scope
2.1 This procedure covers the ultrasonic testing
technique of flash butt welded rail joints by using pulse-echo, a scan
examination method to detect weld discontinuities.
2.2 This
practice utilizes only shear wave probe having 45 degree & 70 degree
refracted angle in steel, 45 degree probes to test head and 70 degree
probe to test web and foot of the welded joint.
3.
Significance
3.1 PERSONNEL QUALIFICATION : It is
essential that evaluation be performed by properly trained and qualified
testing personnel.
4. Code of Procedure
4.1
EQUIPMENT & ACCESSORIES
(i) Pulse-Echo type Ultrasonic Flaw
Detector.
(ii) Two single crystal 45 degree (steel), one single
crystal 70 degree (steel) shear wave/2MHz probes.
(iii) 0 degree-2
or 4 MHz single or double crystal probe-one.
(iv) Battery with
specific voltage suitable for the UFD to be used.
(v) Battery
Charger,
(vi) Voltmeter.
(vii)
Standard rail piece of 2.5M length having standard simulated defects at
standard locations.
(viii) Calibration block 50mm x 50mm x 50mm of
Class IV steel to IS : 1875-70.
(ix) Steel measuring
tape.
(x) IIW-V1 or V2
block.
4.2 PRE REQUISITE
(i) Battery Power : Before
undertaking testing, check the power of the battery to ensure that it is
fully charged.
(ii) Check the correct functioning of the ultrasonic
flaw detector and all angular probes on II W block.
(iii) Coupling
condition/surface preparation : The protruding upset metal around welded
joint shall be removed by any suitable mechanical means in such a way that
the remaining protruded metal does not produce sharp corner and the
finished surface of the protruded metal if any left should merge smoothly
into the surfaces of the adjacent base metal. The scanning surfaces must
be free from weld spatter, scale, dirt, rust and extreme roughness on each
side of the weld for a distance equal to 200mm.
Couplant:
The couplant should wet the surface for the probes and the scanning
surfaces and eliminate any air space between the two. Depending upon
availability and feasibility of the testing, water, oil or grease can be
used as couplant.
(iv) Calibrate the depth range of ultrasonic flaw
detector with the help of 50mm x 50mm x 50mm Class IV Steel
block.
5. Calibration
(i) Calibrate the ultrasonic
flaw detector for 250mm range with help of 0 degree probe. If the 0 degree
probe to be used is a double crystal rail tester probe, then adjust the
onset of surface echo from the perspex wedge of the probe at zero on the
screen by using zero shift/delay/X-shift control. In case the gain setting
is high, multiple echoes of the surface echo may occur. In case of single
crystal probe having no perspex wedge, the onset of the initial echo
should be set at zero.
(ii) Place the 0 degree probe on the
calibration block.
(iii) Adjust the depth and zero
shift/delay/X-shift controls simultaneously so that onset of the following
signal ,appears on the screen.
Onset of the surface
echo
: at 0 main scale divn
„ ,, „ 50mm
signal
: ,, 1 ,, ,, ,,
„ ,, „ 100mm (i.e. 1st
multiple)
: ,, 2 ,, ,, ,,
„ „ „ 150mm (i.e. 2nd
„)
: ,, 3 ,, ,, ,,
„ „ „ 200mm (i.e. 3rd
„)
: ,, 4 ,, ,, ,,
„ ,, ,, 250mm (i.e. 4th
„)
: ,,5 ,, ,, ,,
(iv)
Remove the 0 degree probe and connect a 45 degree probe, turn the probe
selector switch to single crystal operation and set the gain of the UFD
with the help of 5mm dia drilled hole on the standard rail piece. The flaw
signal amplitude should be adjusted to 60% of the screen
height.
The equipment is now calibrated for depth range of 50mm per
main scale division for longitudinal wave and gain of the UFD is set for
conducting the test.
6. Examination of Flash butt welded rail
joints: Examination of flash butt welded joints is performed
separately for the rail head, web & foot. In case of scanning of weld
at rail head, two single crystal 45 degree high angle probes of 2 MHz
shall be used, one of which shall act as transmitter and the other as
receiver. A 70 degree single crystal high angle probe of 2 MHz frequency
shall be employed for examining the welds at web and foot. All the above
probes have index marks on their housing to denote the point at which the
central beam emerges.
6.1 TESTING OF WELD AT RAIL HEAD :
After calibration has done, the 45 degree angle probes shall be connected
to the unit by means of two probe rubies one acting as transmitter and
other as receiver. The probe selector switch shall be operated in T/R mode
in which one works as Transmitter and the other as receiver.
Used
machine oil of adequate viscosity shall be applied as couplant along the
right and left hand side faces of the rail head, upto 100mm away from the
joint on both sides of the weld.
6.1.1 Two 45 degree angle probes
shall be placed and moved along the two aide faces of the rail head in the
longitudinal direction of the rail. Slight twisting movements, with the
beam directed towards the weld, shall be imparted mutually to the probes
as shown in the Fig. (1) In order to examine the entire width of rail head
as well as the height, maximum mutual displacement shall, for a start be
70mm. If, for example, the left-hand probe is 70mm away from the weld, the
right hand probe shall be directly over the weld and vice-versa. The probe
shall then be advanced from the weld as shown in the Fig. (1). The
movement shall be continued until the probes are in reversed positions
with respect to the beginning of the test. This operation shall be
repeated several times and at the end of each transverse slight horizontal
twisting movements shall be given to the probes. Probing may be continued
from the other side of the joint also to take care of defects unfavorably
oriented to the search beam applied from the other side.
6.1.2
Detection of defects: The common flash butt welding defects are
lack of fusion and oxide inclusions. They are generally transversally
oriented. If the rail head is free from the defects, no flaw signal will
appear on the screen. If there are flaws, the beam will be reflected at
the discontinuities and picked up by the receiver probe. For a particular
rail section, the flaw signal shall always appear at a fixed graduation en
the horizontal scale. The location of the flaw can be determined by the
position of the probes. Invariably the flaw will be on that side of the
rail head, which is nearer to the weld. If both the probes are at equal
distance from the weld, the flaw will be in the centre of the rail head as
shown in Fig. (1). An indication of the flaw size can be made from the
amplitude of the flaw signal and the extent of the transverse of the
probes. Any welded joint when tested with gain setting specified showing
any flaw signal shall be considered as defective.
6.2 TESTING OF
WELD AT RAIL WEB AND FOOT
6.2.1 Checking of Sensitivity:
For examining the web and tool locations of flash butt welded rail joins
the detector's setting requires no change apart from switching over to T +
R mode in which case the probe works both as a transmitter as well as
receiver. The 70 degree angle probe shall be connected to the transmitting
socket of the instrument and the sensitivity setting of the system shall
remain unchanged.
6.2.2 Couplant Used machine oil of
adequate viscosity: shall be applied as couplant along the right and left
hand side surfaces of the rail web and foot upto 100mm away from the joint
on both sides of the weld.
6.2.3 Testing Procedure: The
probe shall be positioned 100mm away from the weld and traversed in a
zigzag manner towards the weld. The probing should be done on the web as
well as the foot so that entire width is scanned (See Fig.
2).
6.2.4 Detection of defects: To defect flaws in the web,
the probe must be twisted slightly in the direction of the Web. No .flaw
signal will appear on the screen if the rail foot and web are sound. If
there are discontinuities in the weld, moving flaw signals will appear on
the screen. When the flaw signal is at its maximum height, the distance of
the probe from the weld joint shall be measured, so as to determine the
location of the flaw.
Any welded joint when tested with normal gain
setting showing any moving signal shall be considered as
defective.
Annexure-
VIII
(Para 11)
HANDLING INSTRUCTIONS FOR 90
UTS AND HEAD HARDENED RAILS
Protection of straightness:
Barely visible straightness iations, for example, a deflection of 0.75 mm
over 1.5 res span, renders a rail unacceptable and require careful dling
and stacking. Therefore,
AVOID
— Heavy static
loading.
— Sudden impact or dynamic loading.
— Localised
point or line contact loading in stacking.
— Excessive end drop and
flange overlaps while lilting/moving.
— Criss-cross stacking of
rails of alternative layers at right angles as far as
possible.
DO
— Keep rails horizontal and straight
while lifting/ moving.
— Stack rails of same length on firm level
base of well-drained platform, preferably of concrete, as per drg. No.
RDSO/T-4962 (enclosed).
— Stack subsequent layers on uniformly
placed spacers in vertical alignment with base supports.
— Keep
rail ends in vertical alignment.
— Place rails of shorter length in
upper layers.
2. Protection of rail surface : Surface
notches of even less than 0.75 mm in depth are liable to cause rail
fracture in service. Therefore,
AVOID
— Impact
abrasion of rails against separators in wagons.
— Round link chain
slings for securing the rails.
DO
— Use conventional
slings for lifting rails made of Hat link chains.
— Lifting of
rails preferably with magnet lifting device.
3 Prevention of
metallurgical damage: These rails are thermally very sensitive and are
likely to develop metallurgical defects, if exposed to localised heating,
which produces very hard, brittle and cracked metallurgical structures
which may lead to sudden failures. Therefore,
AVOID
—
Heating, flame cutting, on or adjacent to rails.
— Contact with
electric arcs and molten metal splashes, i.e., from loose cables or
adjacent welding operations.
DO
— Flame cutting when
found essential, after preheating minimum of 10cm of rail length on either
side of me cut to about 250—350 degree C by uniform movement of heating
torch.
4. Protection from contact with injurious substances:
These rails can withstand normal degree of rusting but localised
corrosion pitting may cause subsequent rail fractures
Therefore,
AVOID
— Contact with injurious substances
which produce high corrosion of steel, i.e. acids, alkalis, salts,
etc.
DO
— Stack rails on well drained platform
preferably of concrete as per drawing No. RDSO/T-4962.
5. Slinging
principles : The single point slinging increases risk of excessive-
bending and surface damage to the rails. The overhang beyond the outer
lifting point should not be greater than one-half the distance between
lifting points. Therefore,
AVOID
— Single point
slinging.
DO
— Use two-point slinging for rail length
upto 13m.
— Recommended locations of lifting points for various
rail lengths are tabulated below :
| Rail length
metres |
No. of lifting
points |
Distance between lifting
points (m) |
Max. rail and overhang
(m) |
| 12-13 |
2 |
6-6.5 |
3-3.25 |
| 26 |
4 |
6.5 |
3.25 |
| 35 |
6 |
6.5 |
3.25 |
| 130 |
20 |
6.5 |
3.25 |
| 260 |
40 |
6.5 |
3.25 |
— Use of lifting beams fitted with
slings is desirable.
6. Safety of
Personnel
AVOID
— Standing
under suspended loads.
DO
Use protective gloves and
clothing to minimise the risk of skin abrasion.
Wear distinctive
coloured helmet and clothing for easy identification by crane and
machinery drivers to avoid accidents.
Annexure IX
|
CHECK LIST FOR FLASH
BUTT WELDING PLANTS |
Yes |
No |
| 1. ITEMS TO BE
CHECKED DAILY |
. |
. |
| 1.1 UNLOADING OF
LOOSE RAILS |
. |
. |
| 1.1.1 Rails of
same section and UTS are stacked together. |
. |
. |
| 1.1.2 Spacers
arc provided between successive layers of rails. |
. |
. |
| 1.1.3 Rails are
stacked in head up position. |
. |
. |
| 1.1.4 Numbers of
layers in each stack is not exceeding 15. |
. |
. |
| 1.2 FEEDING OF
RAILS |
. |
. |
| 1.2.1 Rail ends
have been checked for— |
. |
. |
| (a)
Straightness |
. |
. |
| (b)
Squareness |
. |
. |
| (c) Width of
head and height |
. |
. |
| 1.2.2 Fish bolt
holes/any other hole drilled are chamfered. |
. |
. |
| 1.2.3 Rail ends
are cleaned of rust, scales, paint etc. |
. |
. |
| 1.2.4 Top of
rail head and bottom of rail foot are clear at electrode
position. |
. |
. |
| 1.2.5 Grease/oil
at rail ends, if present, has been removed with Carbon tetra
chloride/ Benzene. |
. |
. |
| 1.3
WELDING |
. |
. |
| 1.3.1 Alignment
of rail ends is proper and checked with 1m straight edge |
. |
. |
| 1.3.2 Electrodes
surfaces are clean (cleaning after every welding
operation). |
. |
. |
| 1.3.3 Stipulated
oil & air pressure is available in the welding
machine. |
. |
. |
| 1.3.4 Record of
each weld is kept in prescribed proforma. |
. |
. |
| 1.4 FINISHING OF
JOINT |
. |
. |
| 1.4.1
Stripping/trimming of entire weld cross section has been
done. |
. |
. |
| 1.4.2
Notches/undercuts are avoided while stripping with pneumatic
chisel. |
. |
. |
| 1.4.3 Post weld
controlled cooling is done for Cr-Mn/head hardened rails. |
. |
. |
| 1.4.4 Joint has
been checked for— |
. |
. |
| (a) Straightness
on |
. |
. |
| (i) 10 cm st.
edge, |
. |
. |
| (ii) 1 m st.
edge, |
. |
. |
| (b) Dimensional
tolerances. |
. |
. |
| 1.4.5 Joint is
numbered. |
. |
. |
| 1.5 TESTING OF
JOINT |
. |
. |
| 1.5.1 Joint is
ultrasonically tested using normal, D.E. 70°, 45° and 80°
probes. |
. |
. |
| 1.5.2
Ultrasonically defective joint is prominently marked. |
. |
. |
| 1.5.3 Joint is
dimensionally correct (checking with 10 cm & 1 m straight
edge). |
. |
. |
| 1.5.4 Records of
each test are maintained in prescribed proforma. |
. |
. |
| 1.6 DESPATCH OF
PANELS |
. |
. |
| 1.6.1. Panels of
same rail section and UTS are stacked together.. |
. |
. |
| 1.6.2 Spacers
are provided between successive layers of panels. |
. |
. |
| 1.6.3 Panels are
stacked in head up position. |
. |
. |
| 1.6.4 Number of
layers of panels is not exceeding 15. |
. |
. |
| 1.6.5 Rails are
placed on rollers without impact. |
. |
. |
| 1.6.6 Loading of
weided panels in EUR is being done in pairs of equal
length. |
. |
. |
|
Signature of Shop
Supdt./Supervisor |
. |
. |
| 0.1TEMS TO BE
CHECKED WEEKLY |
. |
. |
| 2.1 Electrodes
have been machined before formation of 1 mm deep groove. |
. |
. |
| 2.2 Standard
welding parameters are correctly set for the type and section of
rails x. being welded. |
. |
. |
| 2.3 Panels with
defective joints are separately stacked. |
. |
. |
| 2.4 Movement of
hoists in lateral and vertical direction is well
synchronised. |
. |
. |
| 2.5 Work, spot
is clean and tidy. |
. |
. |
| 2.6 While
unloading, the rails are held at two points 6-6.5m apart and
overhang of ends does not exceed 3-3.5m. |
. |
. |
| 2.7 Rails/Panels
are stacked on levelled and well drained platform and they have no
contact with soil. |
. |
. |
| 2.8 Transverse
testing & macro examinations of test welds is done at prescribed
frequency and records are maintained. |
. |
. |
| 2.9 Transverse
testing machine is calibrated. |
. |
. |
| 2.10 Workmen are
provided with required protective clothing. |
. |
. |
Signature of XEN/Dy.
CB
|