2. DEVELOPMENT OF FLAWS IN
RAILS
Development of flaws in rails is inevitable
Two main reasons are the inherent defects
and fatigue of rails due to passage of
traffic
Rail stresses are increasing day by day
due to which mechanical properties of rail
steel are being exceeded with passage of
wheels
2
15. SONIC & SOUND
Sonic is related to or using sound.
Sound waves are categorized by their
frequencies as.....
Subsonic ( less than 20 Hz)
SONIC ( BETWEEN 20 & 20,000 Hz)
Ultrasonic ( > 20,000 Hz)
Sound Waves are Mechanical Waves
Other Waves are Electro Magnetic
Waves
17
16. CLASSIFICATION OF SOUND WAVES
LONGITUDINAL OR COMPRESSION
WAVES
TRANSVERSE OR SHEAR WAVES
SURFACE WAVES
18
17. LONGITUDINAL WAVES
Vibration of the particles of the material
are in the same direction as that of
propagation of the wave
Sound energy is transmitted from one
particle to another by alternating
compression & hence these are also
called compression waves.
These can travel through solids , liquid
& gases.
These are the fastest of all wave types.
19
19. TRANSVERSE WAVES
Vibration of the particles of the material
are in a direction perpendicular to the
direction of propagation of the wave
Energy is transmitted from one particle
to another by shear. Hence also known as
shear waves.
These can travel only through solids and
on surface of liquids. These can not travel
through liquids and gases as they do not
have any shear strength.
Their velocity in any given media is
approx. half the velocity of longitudinal
Waves.
21
21. SURFACE WAVES
These are confined to a very thin layer of
material surface and are therefore not
important from the point of view of rail
flaw detection
23
22. WAVE VELOCITIES
MEDIUM VELOCITY IN m/sec
LONG. WAVES TRANS. WAVES
STEEL 5900 3230
COPPER 4700 2260
PERSPEX 2730 1430
WATER 1480 CAN'T TRAVEL
AIR 330 CAN'T TRAVEL
24
23. WAVE PROPAGATION
Velocity of travel v depends upon
the material through which the wave
is to propagate
V = f *
HIGHER THE FREQUENCY, LOWER
WILL BE THE WAVELENGTH
25
25. TRASFORMATION OF WAVES
i
MEDIUM - I
MEDIUM - II
INCIDENT
WAVE
r
REFLECTED
WAVE
REFRACTED
WAVE
PERSPEX, v1
STEEL, v2
i=r
2
1
sin
sin
v
v
i
27
26. Mode Conversion
When a longitudinal wave hits an interface
at an angle, some of the energy can cause
particle movement in the transverse
direction to start a shear (transverse)
wave.
Mode conversion, occurs when a wave
encounters an interface between material
of different accoustic impedance and the
incident angle is not normal to interface.
28
27. TRASFORMATION OF WAVES
i
MEDIUM - I
MEDIUM - II
INCIDENT
WAVE
rT
REFLECTED
WAVES
REFRACTED
WAVE
PERSPEX, v1
STEEL, v2
rL
T L
T
L
T
L
L
vL1=2730 m/s
vT1=1430 m/s
vL2=5900 m/s
vT2=3230 m/s
29
32. TRASFORMATION OF WAVES
ic1
MEDIUM - I
MEDIUM - II
INCIDENT
WAVE
PERSPEX, v1
STEEL, v2
T
L
T
L
L
ic1=27.70
L=900
T=33.30
TOTAL
INTERNAL
REFLECTION
34
33. TRASFORMATION OF WAVES
ic2
MEDIUM - I
MEDIUM - II
INCIDENT
WAVE
PERSPEX, v1
STEEL, v2
T L
T
L
L
ic2=57.70
L=900
T=900
TOTAL
INTERNAL
REFLECTION
35
34. Total internal reflection
FIRST CRITICAL ANGLE - 27.70
SECOND CRITICAL ANGLE - 57.7O
This phenomenon is used for testing by
Angular Probes
37
36. ACOUSTIC IMPEDANCE
It is a property of the material
which determines its affinity for
propagation of sound waves.
The acoustic impedance (Z) of a material is
defined as the product of density (p) and
acoustic velocity (V) of that material.
Z=pV
39
37. ACOUSTIC IMPEDANCE
MATERIAL ACCOUSTIC IMPEDENCE
STEEL 4.68
CAST IRON 2.5 TO 4.0
ALUMINIUM 1.72
AIR 0.0004
WATER 0.149
MACHINE OIL 0.15
PERSPEX 0.32
40
38. Reflection and Transmission
Coefficients
Ultrasonic waves are reflected at
boundaries where there is a difference
in acoustic impedance (Z) .
Fractional amount of transmitted sound
energy plus the fractional amount of
reflected sound energy equals one.
The greater the impedance mismatch,
the greater the percentage of energy
that will be reflected. 41
39.
R is reflection coefficient.
Multiplying the reflection coefficient by 100, yields
the amount of energy reflected as a percentage
of the original energy.
Since the amount of reflected energy plus the
transmitted energy must equal the total amount
of incident energy, the transmission coefficient is
calculated by simply subtracting the reflection
coefficient from one.
Reflection and Transmission
Coefficients
2
1
2
1
2
Z
Z
Z
Z
R
42
40. REFLECTION AT INTERFACES
MEDIUM 1 MEDIUM 2 % REFLECTED % REFRACTED
STEEL AIR 100 0
WATER STEEL 88 12
STEEL PERSPEX 76 24
PERSPEX WATER 13.3 86.7
PERSPEX AIR 100 0
AIR WATER 99.9 0.1
44
43. When sound travel through a medium, its
intensity diminishes with distance.
The combined effect of scattering and absorption
is called Attenuation.
Absorption .. is energy consumed in the process of
causing vibrations of the particles of matter.
Scattering.. is energy lost by dispersion of waves all
over in the material.
Ultrasonic attenuation is, therefore, the rate of
decay of the wave as it propagate through
material.
ATTENUATION
47
44. ATTENUATION
ATTENUATION = D3 f4 / V4
i.e.. A = D3 /
Where D = avg. Grain size of the
material
Thus loss of energy is more for
Coarse material .. welds
Smaller wavelengths (or higher
frequencies) in a given material & for
shear waves as compared to long.
Waves of same frequency in same
material.
48
45. WAVE LENGTH & DETECTABLE FLAW
SIZE IN STEEL
FREQ. WAVE LENGTH IN MM FLAW SIZE mm
MH Z LONGITUD.TRANSVERSE LONGITUD.TRANSV.
1 5.9 3.23 2.95 1.6
2 2.95 1.61 1.48 0.8
3 2 1.08 1 0.54
4 1.5 0.81 0.75 0.4
5 1.2 0.64 0.6 0.32
Detectable size of flaw=wavelength/2
49
47. FLAW DETECTION
An ultrasonic wave is first introduced
into the rail steel
The ultrasonic wave will travel through
the rail until it comes across a
boundary with a dissimilar medium .
At the boundary the wave will either get
reflected or refracted depending upon
the acoustic impedance of the two
media.
51
48. FLAW DETECTION (contd)
The boundary could be the other surface
of the rail or an internal flaw.
A flaw in rail is air void /crack or any
other material (slag) having acoustic
impedance much different from that of
steel.
The reflected US wave can be detected
and the location & size of the source of
reflection can be interpreted.
52
49. FLAW DETECTION (contd)
This is called “pulse echo” or reflection
technique.
Due to the shape & fixity of rail, the
transmission & reception of signals has to
be done from the same side ( rail head)
The other but less commonly used method
is called “transmission technique”
53
50. A plane (two-dimensional) discontinuity
(e.g. material separation, crack) OR a
volumetric discontinuity (hollow space,
foreign material) reflects the ultrasonic
waves mostly in a certain direction.
If the reflected portion of the sound wave is
not received by the probe then it is unlikely
that the discontinuity will be detected. The
possibilities of detection only increase when
the plane discontinuity is hit normally by the
sound beam.
FLAW DETECTION (contd)
54
51. GENERATION OF US WAVES
PIEZO ELECTRIC CERAMIC CRYSTALS
A property of material which converts electrical
energy into mechanical energy & vice-versa.
NATURAL
QUARTZ
TOURMALINE
RECHELLE SALT
ARTIFICIAL
BARIUM TITANATE (first used)
LEAD ZIRCONATE TITANATE (PZT) ( most commonly used)
LITHIUM SULPHATE
55
52. The piezoelectric element, excited by an
extremely short electrical discharge,
transmits an ultrasonic pulse.
The same element on the other hand
generates an electrical signal when it
receives an ultrasonic signal thus
causing it to oscillate.
The probe is coupled to the surface of
the test object with a liquid or coupling
paste so that the sound waves from the
probe are able to be transmitted into
the test object.
GENERATION OF US WAVES
56
54. PROBES
It is a metallic housing containing the crystal,
damping material, electrical leads & a Perspex
face.
Probes can be classified on the basis of
number of crystals as single or double crystal
probes
angle of wave transmission as normal or angle
probe
frequency
58
55. Normal probe or 0 Degree Probe - uses
longitudinal waves (2 MHz & 4MHz)
Angle Probes – 70 Degree & 45 Degree are
used (2MHz)
PROBES (contd)
59
58. PROBES (contd)
Angle probe uses transverse waves
The transverse waves propagate at
around only half the sound velocity of
longitudinal waves
The area in which an angle of incidence
is present between the 1st and 2nd
critical angle (27.3° - 57.7°) gives us
a clear sound wave in the test object
(made of steel), namely the transverse
wave between 33.3° and 90°
62
61. Calibration & sensitivity setting
Visual inspection of equipment & accessories ----
daily check
Calibration of equipment --- daily check
Sensitivity setting of equip. --- Weekly check
Sensitivity setting of equip. for temp. Variation ---
monthly check
Checking of equip. Characteristics. ---- Monthly
check
65
62. Calibration of Equipment
Probes :- 0o
Calibration :- USFD tester is to be calibrated for 300
mm/200mm depth range (long wave) with II W (VI)
Block on 100 mm side.
(i) Adjust surface echo at ‘Zero’ using ‘Shift/Delay’
control.
(ii) Adjust Range by ‘H-shift/Delay’ and range’ control
simultaneously to get signals at 3.3/6.7/10 for 300mm
range and 5/10 for 200 range.
66
63. Calibration of Equipment
Probes :- 70o
(F), 70o
(B), 70o
GF(F), 70o
GF(B).
Calibration :- USFD tester is to be calibrated for 300 mm
depth range (long wave)/165mm Shear wave with II
W (VI) Block on 100 mm side.
(i) Adjust surface echo at ‘Zero’ using ‘Shift/Delay’
control.
(ii) Adjust Range by ‘H-shift/Delay’ and range’ control
simultaneously to get signals at 6.0on 100 mm
cirvature.
67
67. Sensitivity setting
For 70oGFC probe:- Adjust max. signal from 5Ф FBH in
head (at 15 mm from rail top) to 60% of FSH.
For 45o Test Rig (for locations having scabs/wheel burns)-
Machine to be calibrated for 150 mm range for shear wave.
Sensitivity Setting – Use a 300 mm rail piece (having
vertical ends) of same sectional weight, i.e. 52/60 kg.
Keep 45o probe 30 mm from rail end and below 20 mm
rail top on side of rail head. Receiver probe (at 95 mm
for 52 kg rail and 103 mm for 60 kg rail) signal to be
adjusted to 100% of FSH.
Sensitivity is to be adjusted to cater for variation in temp
also (monthly checking)
71
68. TYPES OF PROBES USED IN USFD OF RAILS
S.NO. ANGLE FREQ. DOUBLE/CRYSTAL WHERE
USED
1 0
0
4 MHz DOUBLE MACHINE
2 70
0
2 MHz SINGLE MACHINE
3 700
2 MHz SINGLE HAND
4 70
0
2 MHz SINGLE(8x8 mm) HAND
5 45
0
2 MHz SINGLE HAND
6 70
0
Shifted
2 MHz DOUBLE MACHINE
72
69. DEFECTS DETECTABLE BY VARIOUS
PROBES
HORIZONTAL FLAWS - 0o PROBE
TRANSVERSE FLAWS - 70o PROBE
LONG. VERT. FLAWS (LVF) - 0o PROBE
BOLT HOLE FLAWS - 0o PROBE
GAUGE FACE CORNER(GFC) FLAWS - 70o
SHIFTED PROBE
NON GAUGE FACE CORNER(NGFC) FLAWS -
70o SHIFTED PROBE 73
70. HIGH FREQUENCY SOUND WAVES ARE INTRODUCED
INTO A MATERIAL AND THEY ARE REFLECTED BACK
FROM SURFACES OR FLAWS.
REFLECTED SOUND ENERGY IS DISPLAYED VERSUS
TIME, AND OPERATOR CAN VISUALIZE A CROSS SECTION
OF THE SPECIMEN SHOWING THE DEPTH OF FEATURES
THAT REFLECT SOUND.
f
plate
crack
0 2 4 6 8 10
initial
pulse
flaw
echo
back echo
Oscilloscope, or flaw
detector screen
ULTRASONIC INSPECTION
(PULSE-ECHO)
74
87. Ultrasonic Testing of Rails in
Steel Plant
Most important source of defects is the
manufacturing deficiencies
Testing in Steel plant is done by an on line
USFD machine having multiple probe
covering entire section
In case the initial testing of rails has not
been done in the steel plant the rail shall
be tested either at FBWP or at site
92
89. Ultrasonic Rail Testing Equipment
and accessories
Inspectors carrying out the ultrasonic
testing of rails shall be trained by RDSO
USFD is carried out by
(a) Single rail tester (SRT)
(b) Double Rail Tester (DRT)
(c) Hand Testers
(d) SPURT Car
94
90. Procurement of USFD equipments should
be done only from the RDSO approved
sources (as per latest list)
Maintenance spares should also be
procured along with machine from
original equipment manufacturer
Total life of USFD machine is eight years
Ultrasonic Rail Testing Equipment
and accessories
95
91. Single Rail Tester
Capable of Testing only one rail at a
time
Provided with 7 probes i.e. normal/
0° (4 MHz), 70°(F) (2 MHz), 70°(B)
(2MHz), 70°(GF/F) (2 MHz), 70 °
(GF/B) (2MHz), 70°(NGF/F) (2 MHz)
and 70 ° (NGF/B) (2MHz)
96
92. Contd…
The signal received from the defects by any
of the probes is indicated on the cathode
ray tube (CRT) screen
In order to find out the origin of detection,
provision for displaying the individual
probe operation has been made in the
equipment
To be used for testing sections other than
LWR / CWR and new AT welds
Single Rail Tester (Contd)
97
93. Double Rail Tester
Capable of testing both the rails at a time
Probes are same as for SRT
Provided with multi-channel facility i.e.
signal from each probe can be
instantaneously distinguished without
taking recourse to process of elimination.
Also provided with a threshold arrangement,
LED display and audio alarm .
98
94. Due to frequent misalignment of probes
on the fish plated joints and limitations
of detection of bolt hole cracks, it is
desirable to deploy on LWR/CWR
sections
Double Rail Tester (contd)
99
95. Checking USFD Testing by AEN
AEN should spend at least few hours (min
2 hours) each month during his routine
trolley inspection with USFD team and
cross check the work incl accuracy,
setting, calibration of machine etc.
SE and SSE should also associate
themselves occasionally
100
96. Safety against failures of rails in track
depends upon the inspection frequency and
the permissible defect size
The inspection frequency and condemning
defect sizes are related parameters
If the inspection frequency is high, the
condemning defect size can be suitably in
creased.
Increase in condemning defect size also
enhances the reliability of inspection as
chances of non detection for smaller size
defects are high.
NEED BASED CRITERIA
101
97. After the initial Testing of Rails in Rail
manufacturing Plant ,the first Retesting need
not normally be done before Test Free Period.
Whenever Rails are not tested in rail
manufacturing plant ,the test free period
shall not be applicable and the rail testing
shall be done as per laid down periodicity
right from the day of its laying in field.
TEST FREE PERIOD
102
98. YEAR OF ROLLING TEST FREE PERIOD
RAILS ROLLED PRIOR
TO APRIL 1999
15% OF SERVICE LIFE
OF RAIL
RAILS ROLLED LATER
TO APRIL 1999
25% OF SERVICE LIFE
OF RAIL
TEST FREE PERIOD for RAILS
Rails having wt. and grade equal to or more than 52Kg/90UTS
shall be tested covering GFC of rail head after every 40GMT
during test free period 103
99. SERVICE LIFE OF RAILS
RAIL SECTION SERVICE LIFE (GMT)
72 UTS 90 UTS
60 Kg 550 800
52 Kg 350 525
90R 250 375
104
100. Frequency of testing for Rails
ROUTE FREQUENCY
ALL BG
ROUTES
ROUTE GMT FREQUENCY
<=5 2 YEARS
>5 <=8 12 MONTHS
>8 <=12 9 MONTHS
>12 <=16 6MONTHS
>16 <=24 4 MONTHS
>24 <=40 3MONTHS
>40 <=60 2 Months
>60 <=80 1.5 Months
>80 1 MONTHS 105
101. Frequency for SKV Welds
Initial acceptance just after execution
( as per AT Weld Manual)
First periodic test - after one year
Further tests based on route GMT-
GMT FREQUENCY
>45 2 YEARS
>30<=45 3 YEARS
>15 <=30 4 YEARS
0-15 5 YEARS
106
102. Frequency for Conventional AT
Welds
Periodic Test – Every 40 GMT OR 5 Years
whichever is earlier.
107
103. CS - 2
In case of welds on Major Bridges and on
Approaches (100 m either side) and in
Tunnel and on Tunnel Approaches (100 m
either side) minimum frequency of testing
shall be once a year.
108
105. Classification of rail/Welds defects and
Action to be taken
SN Clas
si-
ficati
on
Painting
on both
faces of
web
Action to be
taken
Interim action
1 IMR
/
IMR
W
Three
cross
with red
paint
The flawed
portion
should be
replaced by
sound tested
rail piece of
not less than
6m length
within 3 days
of detection
PWI/USFD shall impose
speed restriction of 30
km/h or stricter
immediately and to be
continued till flawed
rail/weld is replaced. He
should communicate to
sectional PWI about the
flaw location who shall
ensure that clamped
joggled fish plate is
provided within 24 hrs.
110
106. :
2 OBS
OBSW
One
cross
with
red
paint
The rail/weld to
be provided
with clamped
joggled fish
plate within 3
days.
PWI/USFD to
specifically
record the
observations of
the location in
his register in
subsequent
round of testing
PWI/USFD to advise
Sectional PWI
within 24 hrs about
the flaw location
Key man to watch
during his daily
patrolling till it is
joggled fish plated.
Classification of rail /Welds defects and Action
to be taken (contd)
111
107. CS- 2
In case of DFWR/DFWO on Major Bridges and
Approaches (100 m on either side) and Tunnel
and approaches (100 m on either side) following
action is to be taken:
a) SE/JE(P.Way) USFD shall impose SR of 30 KMPH
or stricter immediately and to be continued till
Defective weld is replaced. He shall communicate
the flaw location to SE/JE (P Way) who shall
ensure:
b) i) Protection of defective weld by clamped joggle fish plate
within 24 hours
c) Ii) Replacement of defective weld within 3 days.
112
118. Limitation of Ultrasonic Flaw
Detection of Rails
Equipment utilized incorporates facility
only for specified defects
To detect the defect efficiently,
ultrasonic beam is to be directed
towards the flaw perpendicularly – the
defect may not be oriented favourably
for detection
A 4 mm deep layer from rail table can
not be tested as it falls in the dead zone
of the probe 123
119. Severe pipe in the rail may give indication of
flaw echo by 0° probe, but in case of
hairline or fine central shrinkage (pipe),
negligible drop occurring in bottom signal
may remain unnoticed by the USFD operator
Limitation of Ultrasonic Flaw
Detection of Rails
124
120. Bolt hole cracks can be best detected by
37 deg probe, which is not now
available on testing machine. BHF are
now detected by 0 deg probe only. At
fish plated joint, if the cracks are not
favorably oriented or are of smaller size,
their detection may be difficult in initial
stages.
Similarly, if the cracks are propagating
vertically downwards or upwards,
detection is not possible.
Limitation of Ultrasonic Flaw
Detection of Rails
125
121. The ultrasonic probes used in the rail
tester have a frequency of 4MHz
(longitudinal wave) and 2 MHz
(transverse waves). Therefore,
cracks lesser than 0.8mm size cannot
be detected by the present
arrangement.
Limitation of Ultrasonic Flaw
Detection of Rails
126
122. Rails having rust, pitting, hogging, battering
of rail end, misalignment of joints, scabs,
wheel burns and other surface
imperfections restrict proper acoustic
coupling between probe and rail table and
may not permit detection of flaws. Side
probing should be done in such cases.
When ever such defects are encountered,
loss of back wall echo or an alarm signal is
obtained. This indicates that defects if any
below these patches may remain
undetected. Under such circumstances
hand probing may be done.
Limitation of Ultrasonic Flaw
Detection of Rails
127
123. In the Testing of SEJs, CMS crossing, points
and crossings, due to specific shape near
the nose, it is difficult to move the trolley
for testing and achieve acoustic coupling.
Therefore except the stock rail, the balance
portion (machined portion) is not amenable
for detection by USFD trolley.
Under such circumstances, hand probing is
required to be carried out according to the
procedure laid down in the manual for
points and crossing or in the USFD manual.
Limitation of Ultrasonic Flaw
Detection of Rails
128
124. USFD trolley has been designed to operate
under normal conditions of gauge. While
testing on sharp curves gradients, slack
gauge etc, the problem of proper coupling
may arise.
In the event of dimensional variations in the
gauge and also at sharp curves it is possible that
the probes are not properly contacting the rail
surface while testing with DRT.
Testing by hand probing or by single rail tester
may be resorted to.
The test result are not reproducible, no
documentary record for future is generated.
Limitation of Ultrasonic Flaw
Detection of Rails
129
125. Following tests are prescribed for BG and MG
routes .
Testing of Weld Head/Web, which get
covered during Through Periodic Rail Testing
by SRT/DRT.
As per this test defects are classified as
IMRW and OBSW.
Procedure for Ultrasonic testing of
Alumino- Thermic Welded Rail Joints
130
126. 0
0
2 MHz DOUBLE CRYSTAL PROBE
70
0
2 MHz SINGLE CRYSTAL PROBE
45
0
2 MHz SINGLE CRYSTAL PROBE
(foot scanning for clustered defect/
micro porosity in web foot region)
45
0
2 MHz Tandem Probe for Lack of
Fusion
AS PER THIS TEST DEFECTS ARE
CLASSIFIED AS DFW
Initial acceptance test of AT weld
using
131
127. 0
0
2 MHz double crystal probe
70
0
2 MHz single crystal probe
45
0
2 MHz single crystal probe for foot
for half moon crack detection and
70
0
2 MHz ( 8x8 mm) single crystal
probe for half moon crack detection
Periodic testing of AT weld using
132
128. TWR should be planned after welds have carried 50%
of the stipulated GMT of rails . CTE will decide the
priority.
The USFD Testing can be dispensed with in case of
those welds which are >15 years old and protected
by joggled fish plate with two far end tight bolts.
After execution of AT weld, welded zone shall be
dressed properly to facilitate placement of probes and
to avoid incidence of spurious signal on the screen.
The flange of the weld up to a distance of 200mm.
on either side of the weld collar shall be thoroughly
cleaned with a wire brush to ensure freedom from
dust, dirt, surface unevenness etc.
Ultrasonic testing of AT Weld Joints
133
129. Sensitivity setting to be done with the help of
a standard AT welded rail piece of 1.5m length
having a simulated flaw at standard locations
as shown in USFD manual.
Ultrasonic testing of AT Weld Joints
134
131. AT Welds Testing by Hand Probing
At the time of execution – using 0o 2 MHz, 70o 2
MHz probes, 45o 2 MHz (foot scanning for
clustered defects and micro porosities) and 45o
2 MHz (Tandem probe scanning for lack of
fusion;
Periodic Testing :- by 0o 2 MHz (Dbl crystal 18 mm
dia), 70o 2 MHz, 45o 2 MHz (foot scanning for
half moon defects) and 70o 2 MHz (8mm x 8
mm) (single crystal) probes.
Couplant :- Soft grease to be used.
136
132. AT Welds Testing by Hand Probing
0o 2 MHz Probes : - to detect porosity, blow hole,
slag inclusion in head and up to mid-web.
Calibration – 300 mm for longitudinal wave.
Sensitivity :- Set signal 60% of FSH on 3Ф through
hole in head at 25 mm from weld top
Defect marking:- Move on weld area;
signal ≥ 40% and up to 60% of FSH in head and ≥
20% and up to 40% of FSH in web/foot
DFWO
signal ≥ 60% of FSH in head and ≥ 40% of FSH in
web/foot DFWR 137
133. AT Welds Testing by Hand Probing
70o 2MHz Probe:- to detect lack of fusion, porosity,
blow hole, slag inclusion, cracks in Head.
Calibration – 165 mm for Shear waves.
Sensitivity - Set signal 60% of FSH on 3Ф through
hole in head at 25 mm from rail top.
Defect marking:- Move towards weld in zig-zag
manner;
moving signal ≥ 40% and up to 60% of FSH
DFWO
moving signal ≥ 60% of FSH DFWR
A bunch of moving signal ≥ 10% of FSH DFWR138
134. AT Welds Testing by Hand Probing
45o 2MHz Probe:- to inspect bottom of weld foot
for detection of clustered defect, micro porosities
and half moon defects.
Calibration – 275 mm for shear wave.
Sensitivity – adjusted signal from simulated half
moon defect (5Ф semi circle at weld bottom) to
60% of FSH. (Probe moved on rail top at a
distance equal to rail ht.)
Defect marking – any signal ≥ 20% of
FSHDFWR.
139
135. AT Welds Testing by Hand Probing
45o 2MHz Probe ( Tandem probe scanning):- to
detect any vertically oriented defect like lack of
fusion in the rail head, web and foot region
below the web.
Calibration – 275 mm for shear wave.
Sensitivity – adjust signal from bottom of rail by the
receiving probe to 100% of FSH. Increase the
gain further by 10 dB.
Defect marking – any signal ≥ 40% of
FSHDFWR.
140
136. AT Welds Testing by Hand Probing
70o 2MHz (8 mm x 8 mm) Probe:- This is used when 45o
probe can not be used for detection of half moon crack
due to presence of holt hole.
Calibration – 300 mm for longitudinal wave
Sensitivity – keep on flange upper zone at 100 mm
distance and move in zig-zag fashion to catch simulated
half moon defect – set signal at 60% FSH.
Defect marking – move on all four sides of weld foot on
upper and lower zones - any signal ≥ 20% of
FSHDFW.
Limitation : Can not detect all half moon defects
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137. AT Welds Testing by Hand Probing
70o 2MHz (20 mm x 20 mm) Probe for flange testing :- to
detect lack of fusion, porosity, blow hole, slag inclusion
in the flange of AT weld.
Calibration – 300 mm for longitudinal wave
Sensitivity – set signal to 60% FSH on 3Ф drilled hole in
middle of flange. .
Defect marking – keep probe of lower ‘L’ zone at 180 mm
and move towards weld in zig-zag manner. Also repeat
for ‘C’ and ‘U’ zones. Any signal ≥ 40% of FSHDFW.
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138. 75mm Gap AT Weld Testing by Hand
Probing
0o 2MHz Probe :- set signal to 60% FSH on 3Ф hole in
head.
Defect marking – Any signal ≥ 40% of FSH from head or ≥
20% of FSH from web/foot DFW.
70o 2MHz Probe; Head Testing :- set signal to 60% FSH on
3Ф hole in head.
Defect marking – moving signal ≥ 40% of FSH DFW.
70o 2MHz Probe; Flange Testing :- set signal to 60% FSH
on a saw cut of 30 mm in the weld metal in the flange 15
mm away from the edge of weld collar.
Defect marking – moving signal ≥ 20% of FSH DFW
143
144. Testing of web and flange of FBW by 45
0
and 70
0
2 MHz hand probe
Normally there is No need
However CE may order , if failure rate is high
Due to unusually high Weld Failure or abnormal
developments in some section, CE may order,
testing of AT welds early as per need.
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