maintenance of track in ghat section (ksr section) on... · for ultrasonic testing of welds by hand...

GOVERNMENT OF INDIA

MINISTRY OF RAILWAYS

Centre

for

Advanced

Maintenance

TECHnology

Maharajpur, Gwalior - 474 020 (INDIA)

: 0751 - 2470869 & Fax : 0751 - 2470841

UULLTTRRAASSOONNIICC TTEESSTTIINNGG OOFF

AATT WWEELLDDSS

BBYY HHAANNDD PPRROOBBIINNGG (Need Based Concept)

CAMTECH/C/2006/USFD-W/1.0

January - 2006

EXECELLENCE IN MAINTENANCE

(For Official Use Only)


AATT WWEELLDDSS

BBYY HHAANNDD PPRROOBBIINNGG (Need Based Concept)

Foreword

Ultra Sonic Flaw Detection (USFD) technique

is widely used on Indian Railways for detecting flaws in

rails/welds for safety consideration of the track. This

booklet gives correct knowledge for detecting flaws in

AT welds by hand probing.

This booklet mainly focuses on testing

procedure, calibration & sensitivity setting of machine,

defect classification and action to be taken during USFD

testing of AT welds by hand probing (need-based

concept), for ensuring reliable testing and optimum

output of machines.

Civil Engineering branch of CAMTECH has

made excellent effort to bring out this booklet. I am sure

that this booklet would be useful as reference book for

USFD machine officials & field staff of engineering

branch.

CAMTECH/Gwalior R.N.Misra

Date : 01 .02.2006 Executive Director

Preface

Detection of flaws in rails & welds and their timely

replacement is an ongoing process to avoid fracture in track,

which at times can have dangerous consequences.

The objective of this booklet is to provide basic and

technical details regarding ultrasonic testing of AT welds by

hand probing (Need based concept) for the guidance of testing

staff and inspecting official. It covers frequency of testing,

calibration and sensitivity setting of machine, defect

classification, and action to be taken.

This booklet is not statutory & contents are for the

purpose of guidance only. It also does not supersede any

existing instructions from Railway Board, RDSO, Zonal

Railways and provisions of IRPWM & USFD manual (CS upto

16) on the subject.

I am grateful for the assistance given by Shri Neeraj

Shrivastava, STA/Civil/CAMTECH, who went through the

complete text, collected information, data etc. Nice data entry

has done by Shri Ramesh Bhojwani, Console Operator,

CAMTECH.

We welcome valuable suggestions from our readers

for further improvements.

CAMTECH/Gwalior Manoj K. Agarwal

Date : 17.01.2006 Director/Civil

CONTENTS Sr.

No.

Description/Topic Page

Nos. Foreword i

Preface ii

Content iii

Correction Slip iv

1.0 General 01

2.0 Equipment 02

3.0 Probes 02

4.0 Couplant 03

5.0 Periodicity of weld testing 04

6.0 Competency of testing 06

7.0 General Condition of AT Weld for

Testing

07

8.0 Visual examination of welds 07

9.0 Inspection of equipment and accessories 07

10.0 Standard AT welded rail 08

11.0 Guidelines for the Operators during weld

testing

10

12.0 Procedure for Ultrasonic testing of SKV/

Conventional AT Weld

12

13.0 Procedure for Ultrasonic testing of 75mm

wide gap AT Welds

20

14.0 Action to be taken after detection of

defects in AT welds

22

15.0 Record Keeping 23

Notes 24

***

ISSUE OF CORRECTION SLIPS

The correction slips to be issued in future for

this handbook will be numbered as follows:

CAMTECH/2006/C/USFD-W/1.0/CS. # XX date …

Where “XX” is the serial number of the

concerned correction slip (starting from 01 onwards).

CORRECTION SLIPS ISSUED

Sr. No.

of

C.Slip

Date

of

issue

Page no. and

Item No.

modified

Remarks


Ultrasonic Testing of AT welds by hand probing January - 2006

1

GGOO TTOO IINNDDEEXX


AATT WWEELLDDSS BBYY HHAANNDD PPRROOBBIINNGG (Need based concept)

1.0 General

To ensure that AT welds provided in the track are free

from flaws they are inspected visually as well as by ultra

sonic flaw detection techniques. Welds are inspected

visually and by ultrasonic technique immediately, after

execution of new weld, for detecting lack of fusion,

porosity, blowhole, slag inclusion, cracks etc. in head,

web and flange of AT welds, and, then periodically

during service life to detect the development of flaws.

Timely detection of flawed/defective weld and their

replacement is very important, to avoid fracture in track,

which at times can have dangerous consequences.

In ultrasonic testing, flaws are detected by using

ultrasonic waves i.e. sound waves of 2-4 MHz. These

waves are generated, transmitted to the rail/weld and

received back from the rail/weld by small piece of Piezo

electric crystal fitted in the probe, which moves over the

rail/weld. Ultrasonic waves transmitted from the probe

get reflected backward whenever they encounter any

change in medium.



2

Reflection received back is displayed on the oscilloscope

screen. With correct calibration and correct interpretation

of oscilloscope pattern, it is possible to detect type of

flaw, its magnitude and location.

2.0 Equipment

For testing of AT welds, RDSO approved model of

ultrasonic equipment confirming to RDSO specification

No. M&C/NDT/120/2001(Rev.1) Mar.2001 shall be used.

Both SRT and DRT as per RDSO specification are also

suitable for this purpose.

3.0 Probes

For AT weld testing by hand probing, Lead Zirconate-

Titanate Piezo electric crystal probes are used, as under:

Probe

Type

Freq. Crystal /

Size

Scanned Area

00

Normal

probe

2

MHz Double

crystal,

18 mm

circular

For detecting

defects in head and

upto mid-web of the

AT weld joint.



3

700 Probe 2

MHz Single

crystal,

20 mm

circular / 20 x

20 mm square

For detecting

defects in head and

flange.

450 Probe 2

MHz Single

crystal, 20 mm

circular /

20 x 20 mm

square

For detecting half

moon shaped defect

at weld foot when

there is no hole in

the web of rail in

the welding zone.

700 Probe 2

MHz Single

crystal, 8mm x 8mm

square

For detecting half

moon shaped defect

at weld foot when

there is hole in the

web of rail in the

welding zone.

For each probe co-axial cable shall be used. Length of

cable used shall not be more than 2 metres.

4.0 Couplant

To wet the surfaces of the probe and the scanning

surface and to eliminate any air gap between the two,

soft grease or oil is used as couplant. GGOO TTOO IINNDDEEXX



4


5.0 Periodicity of weld testing

There are two systems of ultrasonic testing of welds,

based on inspection frequency and permissible defect

size viz. conventional and need based system. In need

based system, frequency of weld testing is as under :

(i) Initial testing

The welds are tested just after their execution. This

test is also known as Initial Acceptance Test. In this

test, complete ultrasonic scanning of weld i.e. head,

web and flange, is carried out by hand probing with

the use of 00

2 MHz, and 700

2 MHz (20 mm size)

probes.

Weld found defective during initial testing shall be

cropped, rewelded and tested again ultrasonically till

found good.

A thermit welding done in situ shall be joggled fish

plated with two clamps till tested as good by USFD.

(ii) Periodic testing

After initial testing, periodic testing of weld is

carried out as under.



5

(a) Complete scanning of weld by hand probing

In this test a complete weld i.e. head, web and bottom

flange is scanned by using (i) 00 2 MHz, (ii) 70

0 2 MHz

(20 mm size) and (iii) 450 2 MHz or 70

0 2 MHz (8 mm

size) probes.

As per this testing defects detected in welds are classified

as ‘DFW’.

The frequency of periodic testing of complete AT welds

by hand probing is as under:

Sr.

No.

Type of

Welds

Type of Testing Testing Schedule

1 SKV First Periodic

Test

On completion of

one year service life

by weld.

Second Periodic

Test

On passage of 120

GMT after First

Periodic Test

Third Periodic

Test

On passage of 120

GMT after second

periodic Test.

Subsequent

Periodic Test

Nil



6

2 Conven

-tional

AT

First Periodic

Test

On completion of

one year service life

by weld.

Subsequent

Periodic Test

Every 40 GMT after

First Periodic Test.

Note: Due to unusually high weld failure or other abnormal

development in some sections, Chief Engineer may order

testing of welds early, as per need.

The USFD testing can be dispensed with in case of those welds,

which are more than 15 years old and protected by joggled fishplates with two far end tight bolts.

(b) During through periodic Rail Testing

Ultrasonic scanning of weld i.e. head and web portion, is

also carried out during through periodic rail testing by

SRT/DRT. As per this testing defects detected in weld

heads are classified as ‘IMRW’ and ‘OBSW’. The

action to be taken for such defective welds is same as for

defective rail.

6.0 Competency for testing

Inspector carrying out the ultrasonic testing of AT welds

shall be RDSO trained, in the techniques of USFD

testing.



7


7.0 General Condition of AT Weld for

Testing

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 top

of railhead surface shall be dressed to obtain reasonably

flat and smooth surface. The flange of the weld upto a

distance of 200 mm on either side of the weld collar shall

be thoroughly cleaned with a wire brush to ensure

freedom from dust, dirt, surface unevenness etc.

8.0 Visual examination of welds

All the welded joints shall be cleaned and examined

carefully to detect any visible defects like cracks,

blowholes. Any joint, which shows any visible defect,

shall be declared defective. Inspe

9.0 Inspection of equipment and

accessories

a. Visual inspection of equipment and accessories

(daily check)

Ultrasonic equipment is to be inspected daily before start

of work for proper functioning of plugs, holders, cables,

etc. In addition, battery condition, proper functioning of



8

echo-control knobs i.e. depth range, gain, reject etc.

shall also be checked by the USFD operator before

commencement of the testing.

Gap between probe faces and probe shoe should be

checked with the help of a feeler gauge and the gap

adjusted to 0.2mm.

b. Checking the equipment characteristics (monthly

check)

The characteristics of the equipment shall be checked

atleast once in a month according to IS: 12666 - 88.

Following characteristics are checked :

Linearity of time base of flaw detector

Linearity of amplification of flaw detector

Penetrative power

Resolving power

Probe index

Beam angle

10.0 Standard AT welded rail

For ultrasonic testing of welds by hand probing, the

sensitivity of ultrasonic equipment for the various probes

shall be set with the help of a standard AT welded rail

piece of 1.5 metre length having a simulated flaw at

standard locations as shown in figures below :



9

(a) For 00 (18 mm) & 700 (20 mm) probes

For SKV and conventional welds

30 mm deep saw cut in weld collar, 15 mm away from edge of weld collar.

BOTTOM PLAN

For 75 mm wide gap welds



10

(b) For Half moon defect - 45º (20 mm) & 70º (8mm)

probes

Weld profile bottom

SECTIONAL ELEVATION AT AA

Weld profile bottom Up to 2 mm max.

depending on cutting tool

DETAILS AT A SECTIONAL ELEVATION AT BB

11.0 Guidelines for the Operators during

weld testing

The correctness of angles and index marking of the

probe shall be ascertained before testing. Only

Rail

bottom

Weld

portion



11

probes meeting the specified values shall be used

during testing.

Mere appearance of moving signal during flange

testing of weld shall not be the criterion for rejection

of a joint. These signals may come from the

geometry of the flange weld reinforcement.

Therefore, while declaring a joint defective in flange

testing, operator shall ensure that signals are flaw

signals and not the signals coming due to

geometrical configuration of the weld. Following

method shall be adopted for taking decision in this

regard:

a) Horizontal distance of the flaw from probe

index mark shall be calculated using formula :

H= S Sin θ Where,

H = Horizontal distance of the flaw

from probe index mark.

θ = Probe angle

S = Beam Path, calculated using

horizontal screen reading as given

below:

Rl = Range set for longitudinal wave

Rs = Range set for shear wave

Rs = R1

1.82



12

S = Horizontal Screen Reading (in No. of Div.) x Rs

Total No. of divisions on Horizontal Scale

b) Measure the distance equal to H from probe

index to confirm if the flaw signal is coming

from the weld collar/reinforcement or from the

weldment.

Oil or grease shall be used for proper acoustic

coupling instead of water for AT weld testing.

Operator shall use the same couplant during testing

and setting the sensitivity.

12.0 Procedure for Ultrasonic testing of

SKV/ Conventional AT Weld (By hand

probing)

After dressing of AT welds and adjoining area as

mentioned in Para 7.0, each weld is visually examined as

mentioned above and ultrasonically tested by using

prescribed probes in the following steps:

a. Calibration of the equipment

b. Sensitivity setting of the equipment and probes

c. Testing

d. Defect Classification



13

Depth range is calibrated with the help of 60 X 50 X 50

mm of 45C8 grade steel block confirming to IS : 1875-

92.

Detailed procedure of Ultrasonic testing of AT Welded

rails joints by hand probing using 0º 2MHz, 70º 2MHz

and 45º 2MHz or 70º 2MHz (8mm x 8mm) probes is as

under:

(i) 0º - 2 MHz, Normal Probe

Testing by this probe is carried out both in initial and

periodic testing for scanning head and upto mid web

portion of AT weld.

Calibration: The equipment shall be set for a depth

range of 300 mm (Longitudinal wave). Connect the

double crystal probe with ultrasonic equipment and

select T/R (Double crystal) mode by selector switch.

Sensitivity Setting: Place 0º normal probe on test

rail. The reflection from 3 mm dia. hole in head of

standard AT welded rail test piece shall be set to

60% of full screen height by suitable manipulation

of gain control knobs.



14

Testing: The probe shall be placed on the head of

the AT welded joint ensuring proper acoustic

coupling. The probe shall be moved on the weld

centre to scan the weld area.

Defect Classification

o Any flaw signal obtained by normal probe from

the head region of 40% height or more shall be

treated as defective AT welded joint (DFW).

o Any flaw signal of height more than 20% from

the web or foot location shall also be cause for

rejection of AT welded joint (DFW).

(ii) 70º - 2 MHz, (size 20mm x 20mm) Probe

Testing by this probe is carried out both in initial and

periodic testing by scanning (i) head, as well as, (ii)

bottom flange.

a. Head scanning

Calibration: The equipment shall be calibrated for a

depth range of 300mm (Longitudinal wave).



15

Sensitivity Setting: Connect the 70º- 2MHz probe

by means of co-axial cables and select (T+R) mode.

Place the probe on the railhead directing the beam

towards 3 mm dia drilled hole in the head of the

standard AT welded test piece. Move the probe in

longitudinal direction on the rail so that reflection

from the hole is obtained. Now set the height of the

reflected signal to 60% of full screen height by

suitable manipulation of the gain control knob.

Testing: Place the probe on the railhead on one side

of the AT welded reinforcement and move toward

the weld in zigzag manner. This exercise shall be

repeated 2-3 times. The same shall be carried out

from both sides of the weld.

Defect Classification: A welded joint showing

moving signal of 40% or more of the full screen

height shall be considered as defective welded joint

(DFW).

b. Flange testing

Calibration: The equipment shall be set for a

depth range of 300mm (longitudinal wave) by

manipulating the depth range control.



16

Sensitivity setting: 70º- 2MHz, single crystal

probe shall be connected to the socket available in

the ultrasonic equipment. The selector switch shall

be set to single crystal mode. Move the probe

towards the 3mm. dia hole drilled in the middle of

flange of the AT weld and manipulate knobs to

obtain a maximum signal height to 60% of full

screen height on the screen.

Testing: 70º probe shall be placed on the flange at

a suitable distance (180mm) corresponding to

position 'L' (lower zone) as shown in Figure below

such that ultrasonic waves are directed towards the

weld. The probe shall thereafter be moved slowly

in a zigzag manner towards the weld. Similar

testing shall be carried out from 'C' (central zone)

and 'U' (upper zone) position as shown in figure.

The same shall be carried out from both sides of

the weld.



17

Defect classification: A welded joint showing a

flaw echo of 40% vertical height or more with the

stipulated gain setting shall be treated as a

defective welded joint (DFW).

(iii) 45º (20 mm) / 70º (8mm) probes

Testing by either of these probes is carried out only

during periodic testing to detect half moon shaped

defect at bottom of weld foot as under:

(a) When there is no hole in the web of rail in the

welding zone - by 45º- 2 MHz probe.

or

(b) When there is hole in the web of rail in the

welding zone - by 70º- 2 MHz (size 8mm x

8mm) probe.

(a) By 45º- 2 MHz probe


range of 500 mm for longitudinal wave using 0º

probe.

Sensitivity Setting: Place 45º- 2MHz probe on the

railhead surface at a distance equal to height of rail

from the centre of the AT weld. Move the probe

20mm either side of this position (probe index



18

marking) to pick up half moon crack in the central

region of weld reinforcement as shown in figure

below.

This exercise shall be carried out two-three times

from each side of the weld and signal from

simulated flaw should appear at a distance of

approximately 400 mm for 52kg rail. This distance

will vary with respect to rail section height. The

signal so obtained shall be adjusted to 60% of full

screen height by manipulating the gain control knob.

Probe positions



19

Testing: The probe shall be placed on the railhead at

a distance equal to height of the rail from the center

of AT Weld (Probe Index Marking) under test. This

testing technique will scan the bottom of the weld in

the central zone. The probe shall be moved 20 mm

on either side of the probe index marking. The

scanning shall also be repeated from other side of

weld with beam directing towards the foot region of

the weld.

Defect Classification: Any flaw signal obtained by

this probe of 20% height or more shall be treated as

defective AT welded joint (DFW).

(b) By 70º- 2 MHz (size 8mm x 8mm) probe


range of 300 mm (longitudinal wave) by

manipulating the depth range control.

Sensitivity Setting: One 70º- 2 MHz, of 8mmx8mm

size probe shall be connected to the unit by means of

one coaxial cable. The selector switch shall be in

T+R (single crystal) mode. Apply the couplant and

place the probe at a distance of 100 mm from edge

of the weld near the upper zone/root of the flange

with beam direction towards simulated flaw. Move

the probe slightly in zig-zag manner to get reflection



20

from simulated flaw. Set the height of signal to

60% of full screen height by suitable manipulation

of the gain control knob.

Testing: 70º (8mm x 8mm) probe shall be placed

on the upper zone/root of the flange at a suitable

distance (100mm approx.) with beam directing

toward webfoot junction. This exercise shall be

carried from all the four sides of rail flange on top

and also the bottom of rail flange on both the sides

of weld collar. Any moving signal on the screen

shall be recorded.

Defect classification: Any flaw signal of height

20% or more than the full screen height shall be

treated as defective AT welded joint (DFW).

13.0 Procedure for Ultrasonic testing of

75mm wide gap AT Welds (By hand

probing)

Procedure for ultrasonic testing of 75 mm wide gap AT

welds is same as for SKV/ conventional welds except for

sensitivity setting and defect classification.



21

(i) Sensitivity setting

For head testing

The signal from the simulated flaw of 3mm dia.

hole in the head shall be set to 60% of full screen

height with 0° 2 MHz and 70° 2 MHz probes for

detection of discontinuities in the rail head.

For Flange testing

The signal from the simulated flaw of a 30 mm saw

cut in the weld metal in the flange 15mm away

from the edge of the weld collar shall be set to 60%

of full screen height.

(ii) Defect Classification

Head: With 0° & 70° probes, rejection / defect

criteria will be same as for 25mm gap AT weld

joint.

Flange: Any moving signal of height more

than 20% of the full screen height shall be

treated as defective weld (DFW).



22


14.0 Action to be taken after detection of

defects in AT welds

Action during initial testing

The defective joints shall not be allowed to remain in

service and these joints shall be cropped, re-welded and

tested again. The re-welded joints shall be scanned

ultrasonically again with the same set of acceptance

criteria to ensure freedom from any harmful defects.

Action during periodic testing

Classi-

fication

Painting

on both

faces of

weld.

Action to be taken

Defective

weld

‘DFW’.

Two

Cross

with red

paint

PWI/USFD shall impose speed

restriction of 30 kmph or stricter

immediately. He should

communicate to sectional PWI about

the flaw location who shall ensure

following:

(i) Protection of defective weld by

joggled fishplates using

minimum two tight clamps/2

far end tight bolts one on each

side after which speed

restriction can be relaxed upto

75kmph.



23

(ii) In case the protection of weld

has been done using joggled

fishplates with clamps, the

defective weld shall be replaced

within 15 days. However, in

case the protection has been

done using joggled fish plates

with 2 far end tight bolts, the

speed restriction imposed in (i)

above, shall continue till the

defective weld is replaced

which should not be later than 3

months. The defective weld

with speed restriction as (i)

above may be continued in

track if the track is to be

renewed within 12 months.

15.0 Record Keeping

A proper record of the testing, observation, and echo

pattern & echo amplitude of the defects detected during

testing, shall be maintained.

***




24

NOTES



25


OUR OBJECTIVE

The contents of this booklet are for guidance only

& are not statutory. It also does not supersede any

existing instructions from Railway Board, RDSO

and zonal Railways & the provisions of IRPWM,

USFD Manual on the subject.

Contact person : Director (Civil)

Postal Address : Centre for Advanced

Maintenance Technology,

Maharajpur, Gwalior (M.P.)

Pin code – 474 020

Phone : (0751) - 2470869, 2470803

Fax : (0751) - 2470841

To upgrade Maintenance

Technologies and Methodologies and

achieve improvement in productivity and

performance of all Railway assets and

manpower which inter-alia would cover

Reliability, Availability, and Utilisation. ________________________________

maintenance of track in ghat section (ksr section) on... · for ultrasonic testing of welds by hand...

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