USFD TESTING



USFD TESTING OF RAILS AND WELDS

CHAPTER  1

RAIL DEFECTS AND THEIR CODIFICATION

Rail is the most important and critical component of the permanent way.  Most common cause of rail failure is the fatigue fracture, which is due to imperfections present in the material or due to crack formation during service.  Thus successful performance of rails is based on their resistance to crack initiation and crack propagation. It is therefore essential to identify and classify the defects in rails and in turn initiate corrective action. A brief on nature of defects, their causes and classification is presented below.

1.1  Causes of defects:  

The origin and development of such cracks is due to:

1.1.1 Material defects originating during the manufacturing process such as clusters of  nonmetallic inclusions, hydrogen flakes, rolling marks, guide marks etc. which may  be present in spite of successful non-destructive tests carried out on the rails during  quality assurance examination.

1.1.2 Residual stresses induced during manufacture (cooling, rolling, gas pressing and straightening).

1.1.3 Defects due to incorrect handling e.g. plastic deformation, scoring, denting, etc.

1.1.4 Defects associated with faulty welding i.e. gas pores, lack of fusion, inclusions,  cracks etc.

1.1.5 Dynamic stresses caused by vertical and lateral loads particularly by vehicles with wheel flats or when the vehicle runs over poorly maintained rail joints etc.

1.1.6 Excessive thermal stresses due to variation in rail temperature beyond specified  limits.

1.2   Defect location:  

In order to study the fractures in rail systematically, they may be divided into the following categories based on their location of occurrence in the rail length:

(a) Defects emanating from the rail end or reaching the end of the rail.

(b) Defects observed within fish-plated zone.

(c) Defects not covered in (a) and (b).

1.2.1 Nature of defects in rails

(a) Horizontal crack in head:  These cracks run usually parallel to the rail table at a depth of 10-20 mm and may finally split the material layer.  Crushing of the railhead may also be observed in the vicinity of the crack.  Clusters of non-metallic inclusions and abnormal vertical service stresses are the factors responsible for this defect.  USFD can easily detect such flaws.

(b) Vertical-longitudinal split in head:  These cracks run parallel to the longitudinal axis of the rail and are caused by presence of non-metallic inclusions, poor maintenance of joints and high dynamic stresses.  It cannot be easily detected in early stages by USFD due to their unfavourable orientation.

(c) Horizontal crack at head web junction: Such flaws may lead to rail head separation. Contributory causes are wheel flats, bad fish-plated joint, inclusions and high residual stresses.  USFD is sensitive to such defects and can easily detect them.

(d) Horizontal crack at web-foot junction:  Such cracks develop both towards head and foot. They are caused by high vertical and lateral dynamic loads, scoring and high residual stresses.  USFD can easily detect these flaws.

(e) Vertical longitudinal splitting of the web:  It is primarily due to heavy accumulation of non-metallic inclusions and wheel flats.  USFD conducted from rail top can detect it only if the defect is severe and in an advanced stage. Vertical longitudinal defects of minor nature are not amenable to USFD examination conducted from rail top. Probing from railhead sides can detect such defects for which hand probing may be essential.

(f) Bolt hole crack:  Such cracks often run diagonally and may run towards head or the foot. They result from inadequately maintained joints and unchamfered fish boltholes and stress concentration.  USFD (37o probe) can easily detect these cracks. Normal probes provide indication as diminished back wall echo.

(g) Transverse fracture without apparent origin:  These fractures occur suddenly, especially during winter and may emanate from microscopic flaws (embedded or on surface) and are generally very difficult to detect by USFD.  These minute flaws manifest suddenly under severe service conditions or when the fracture toughness values are comparatively low.

(h) Transverse fatigue crack in head:  They resemble a kidney in shape in the railhead and USFD is ideally suited for detecting them.  They are generally inclined at the angle of 18o-23o and originate at a depth of 15-20 mm below the running surface.  Mainly hydrogen accumulation and non-metallic inclusions cause this defect.  These cracks are easily detected by 70o probe.

(i) Horizontal crack at top and bottom fillet radius:  These cracks are caused by accumulation of non-metallic inclusions and high residual stresses introduced at the time of rail straightening.  These are difficult to be detected by USFD.

(j) Vertical ± longitudinal crack in foot:  Such cracks develop from sharp chamfers on the bottom surface of the rail foot.  Cracks occurring in this way are the points of origin of transverse cracks in the foot.

(k) Transverse cracks in rail foot:  Due to localised overheating during FB welding, structural changes in the bottom surface of the rail material takes place which result in a minor crack.  These cracks under the tensile loading give rise to brittle fracture.  Such defects are not detectable by USFD. Transverse cracks originated from AT welds in the rail foot grow as half moon and are detectable by 45oprobe.

1.2.2  Nature of defects in welds:  

Joining rails by improper welding may introduce a variety of defects on the joints as well as in the heat affected zone (HAZ) e.g. lack of fusion, cracks, porosity, slag inclusion, structural variation, etc.  The quality of weld depends to a large extent on the careful execution of the welding operation.  USFD testing done by manual rail tester suffers from following deficiencies:

(i) Full cross section of weld is not covered by normal USFD examination using manual tester thereby leaving areas in head and foot, which may have flaws.

(ii) Micro structural variations in the weldment cause attenuation of ultrasonic energy.

Therefore, a separate testing procedure for welds has been developed which is elaborated in Chapters 8 and 9.

1.2.2.1 Defects in Flash Butt Welds

(a) Transverse cracks:  

The origin of these cracks is the imperfection in the weldment such as lack of fusion, inclusions, etc.  Fracture usually occurs from these imperfections, which may be in railhead, web or foot.  During the course of its propagation USFD testing is extremely effective.

(b) Horizontal cracks:  

These cracks develop in the web and propagate both in head and foot.  The principal cause is large tensile residual stresses acting in the vertical direction.

1.2.2.2 Defects in Alumino-Thermic (AT) Welds

(a) Transverse crack in head and foot:  It is caused by inclusions entrapped during welding, which leads to crack initiation on the foot and its growth in the web region causing fracture.  Such cracks can be detected by USFD.

(b) Horizontal cracks in web:  These cracks occur in AT welds in which the ends having bolt holes have not been removed.  The presence of holes result in unfavorable stress distribution caused due to non-uniform cooling.  USFD can easily detect such flaws.

1.3  Codification of rail and weld defects:

Information regarding the type and nature of rail failures and their service conditions is primarily obtained through personnel responsible for maintenance of permanent way and it is of utmost importance that they are familiar with the various types and nature of rail defects and their possible causes to enable them to report the rail failures accurately.  With this objective in view, it is necessary to devise a suitable coding system for reporting rail failures.

1.3.1 UIC has adopted an Alphanumeric system of codification of rail failures.  In view of its international status and the facility afforded for computerized statistical data analysis, this system has been adopted by Indian Railways for reporting rail failures. The code for reporting rail failures consists of two parts viz  first – Alphabetic, consisting of three code letters and second numeric, consisting of three or four digits.

1.3.1.1 First part of the code ± Alphabetic

(a) First code letter indicates the type of rail:

O indicates plain rail
X indicates point & crossing rail

(b) Second code letter which follows the first code letter, indicates the reasons for withdraw of rail.  Thus,

F indicates  Fractured rail 
C indicates  Cracked rail 
D indicates  Defective rail other than F&C
 

(c) Third code letter which follows the second code letter, indicates probable cause of failure or rail.  Thus:

R indicates  Cause inherent in rail (attributable to faults in the steel   making stage and / or its rolling into rails). 
S indicates  Fault of rolling stock 
C indicates  Excessive corrosion
J indicates  Badly maintained joint 
M indicates  Other maintenance conditions (Defects which develop due    To ineffective maintenance or delayed renewal of rails). 
D indicates  Derailment
W indicates  Associated with welding defects (through or adjacent   Within 100 mm of a welded joint) 
O indicates  Other causes
 

1.3.1.2 Second part of the code ± Numeric :  

This part of the code consisting of three or four digits indicates  the location of the failure in the rail as well as its  characteristics :

(a) The first digit indicates the location of rail failure (head, web or foot)

(b) The second digit indicates:

(i) The position in the rail section from which failure has started except where failure is associated with welding.

(ii) In case of welding, the second digit indicates the type of welding.

(c) The third digit is interpreted in relation to the first two digits of the code viz :

(i) If   failure is due to internal defect (first digit 4 or second digit 1,3 or 5), it shows the direction of the crack or fracture.

(ii) If   failure is due to surface defect (second digit 2 or 5), it indicates the nature of defect.

(iii) If failure is by damage (first digit 3), it indicates the cause of the damage (details have been given in succeeding pages)

(d) The fourth digit gives further details.

1.3.1.3 The summary of codification of rail and weld failures is given as under:

(a) First Part – Alphabetic codes

1st letter 2nd letter 3rd letter

Type of rail

O-Plain rail 

X-Points & Crossings rail 

Reason for withdrawal

F-Fractured

C-Cracked

D-Defect other than F&C

Probable cause of failure 

R-Inherent in rail 

S-Fault of rolling stock

C-Excessive corrosion

J-Badly maintained joint 

 M-Other maintenance conditions 

D-Derailment (failure developed later) 

W-Associated with welding 

O-Other causes

(c) Second Part – Numeric codes

1st digit 2nd digit 3rd digit 4st digit
Location & characteristics
 
Origin/Type Of welding
 
i) For internal defects in welding shows direction: if  2nd digit 1,3,5 Further details
1.Within fishplate limit

0-Unknown

1.within head

1. Transverse

2. Horizontal

3. Vertical longitudinal

1. At rail seat

2. Not at rail seat

1. Top fillet

2. Bottom fillet

3. Not at fillet radius

2.Other location

2. Surface of rail head

3. In web

5.In foot

5.   Diagonal at hole 

8. Diagonal not at hole

ii) For surface defects it shows nature of defects if second digit 2,3,5

0.   Corrugation

1. Shallow surface defect 

2. Breaking out

3. C rushing continuous

4.  Battering local 

5.  Wheel burns

9.   Lap, seam, roll mark

1. Short pitch 

2. Long corner 

1.Running surface 

2.Guage corner

1. Isolated 

2.Repeated

3.Damage done 0

 1 Brushing or arcing

2 Incorrect machining drilling or flame cutting

 
4.Associated with welding

Type of welding

1. Flash butt

2. Thermit  

3.  Electric arc     joint

4.  Oxy-acyty     lene joint

7.  Building up

8.  Traction      bond 

Direction of fracture

1. Transverse 

2. H orizontal 

5.  Diagonal at hole

8.  Diagonal not at hole

 
5.Corrosion  0 0  

1.3.1.4 On the basis of the system of classification described in para

1.3.1.2, a list of the failure code group to be followed is given as under, along with the meaning of the codes.

Within fish-plate limits
 
Elsewhere on rail Description
 
100 200  Transverse breakage without apparent origin (i.e. sudden fracture) 
111 211  Internal flaw in head, transverse breakage
112 212  Internal flaw in head, horizontal crack.
113 213  Internal flaw in head, vertical longitudinal split. 
1211 2211 Head, surface, shallow surface defect (flaking) 
1212 2212 Head, surface, shallow surface defect (line). 
1221 2221 Head, surface, breaking out running surface (scabbing) 
1222 2222 Head, surface, breaking out, gauge corner (shelling) 
123 223  Head, surface crushing or battering 
124 224  Head, surface local batter
- 2251 Head, surface, wheel burn isolated 
- 2252 Head surface, wheel burn repeated
1321 2321 Web, horizontal cracks, at top fillet radius 
1322 2322 Web, horizontal crack, at bottom fillet radius 
1323 2323 Web, horizontal crack, not at fillet radius
133 233 Web, vertical longitudinal splitting (pipe) 
135 235 Web, cracks at hole 
- 238 Web, diagonal cracks not at hole.
139 239 Web, lap
1511 2511 Foot, transverse break at rail seat
1512 2512 Foot transverse break starting away from rail seat. 
153 253  Foot vertical longitudinal split (halfmoon crack)
301 - Damage to rail by brushing or arcing
302 -

Damage to rail by bad machining, drilling or flame cutting 

411 - Welding,flashbutt joint, transverse crack 
421 - Welding, thermit joint, transverse crack 
422 -  Welding, thermit joint, horizontal crack
431 -  Welding, electric arc joint, transverse crack 
441 - Welding oxyacetylene joint transverse crack
471 -  Welding, building up transverse cracking of head across the built up portion
472 - Welding, building up, built up part breaks away. 
481 -  Welding, traction bond welding crack, at weld
500 - Corrosion.

1.4 Typical rail/weld failure photographs with their codes are given in Figs. 31 to 56.

CHAPTER 2

ULTRASONIC TESTING OF RAILS AT MANUFACTURERS’ WORKS

The defects in rails may be due to manufacturing deficiencies, defects arising during service or defects generated due to a combination of manufacturing defects and service conditions.  The most important source of defects is the manufacturing deficiencies during steel making, rolling and subsequent processing.

2.1   Testing methods in Steel Plants :  Testing in the Steel Plant is carried out with the help of an on-line ultrasonic testing equipment having multiple probes covering entire cross-section of the rail.  A typical arrangement of probes is shown inFig.1.

All these probes are 0o (Normal probes) of frequency varying between 2.5 – 4.0 MHz. They detect defects oriented perpendicular to the direction of the beam.

2.2   Criteria for acceptance : The criteria of acceptance  is as per clause 10 of IRS :T-12-96 (specification of  flat bottom railway rails).  These are reproduced below:

³10     Freedom from defects

10.1 The rails shall be of uniform section throughout and shall be free from all detrimental defects such as cracks of all kinds, flaws, piping or lack of metal, etc. having an unfavourable effect on the behaviour of the rail in service.

10.2 The absence of harmful internal defects shall be ensured by the continuous on-line ultrasonic examination.  This examination shall be carried out for all rails by the manufacturer to the satisfaction of the inspecting agency.

10..3 The manufacturer in his offer shall furnish the detailed method of on-line ultrasonic testing of rails to be followed by him.  The limits of permissible defects for ultrasonic testing of rails shall be as follows and the standard test piece shall be as shown in Annexure-I

Head    : 1.5 mm dia through hole

Web    : 2.0 mm dia through hole

Web & Foot junction  : 2.0 mm dia through hole

Foot    : 0.5 mm deep, 12.5 mm long and 1.0 mm wide notch     (Inclined at 20o with vertical axis)´

2.3 In case initial testing of rails has not been done in the rail manufacturing plant, the rails shall be tested either at Flash Butt Welding Plant or at site.  In no case rail should be laid in track without USFD testing.

CHAPTER 3

ULTRASONIC RAIL TESTING EQUIPMENT AND ACCESSORIES

3.0 Ultrasonic testing of rails is a specialized activity and the inspectors carrying out the ultrasonic testing of rails shall be trained by RDSO, in the techniques of USFD testing.  Each Zonal Railway shall create adequate no. of Ex-cadre post of inspectors to ensure that entire track length in their jurisdiction is ultrasonically tested at the laid down periodicity.

3.1 On Indian Railways, flaw detection by ultrasonics is carried out with the help of two different types of equipments viz. Single rail tester and double rail tester. The single rail tester has been utilised on Indian Railways for over 40 years and the double rail tester is of a relatively recent origin (developed Ten years back). In addition hand testers of some designs are also being used.  Current list of RDSO approved sources for ultrasonic rail/weld testers with their respective models, is contained in latest version of ‘Masters list of approved venders’ circulated biannually by Quality Assurance (Mechanical) Directorate of RDSO.   Procurement of USFD equipments should be done only from the RDSO approved sources.

3.1.1 Total Life of USFD machine is approximately 8 years.

3.1.2 Maintenance spares be procured along with the machine and should be as per para 4.4 pertaining to maintenance spares.

3.2 Single rail tester :

Single rail tester is capable of testing only one of the rails at a time and is provided with five probes i.e. 0o , 70o Forward (F), 70o Backward (B), 37o Forward (F) and 37o Backward (B). The normal probe (0o) is utilised for the purpose of detecting horizontal defects situated in head, web or foot. The 70o probe has been specifically provided for detecting defects in the rail head, the most typical of which is the transverse fissure or kidney fracture. 37o probes have been provided to find out defects originating from the bolt hole (star cracks). The approximate coverage of the rail section with the help of the above arrangement is indicated in Fig.2A,2B. & 2C.
The signal received from the defects by any of the above probes is indicated on the cathode ray tube (CRT) screen. In order to find out the origin of detection i.e. which probe has picked up the defect, provision for eliminating the individual probe operation has been made in the equipment.

3.3 Double Rail tester:

3.3.1 The double rail tester is capable of testing both the rails at a time. However, for each rail only three probes have been provided for the present i.e. 0o, 70o Forward and 70o Backward. This equipment, unlike the single rail tester, has multichannel facility i.e. the signal received from each probe can be instantaneously distinguished without taking recourse to process of elimination. This equipment has also been provided with a threshold arrangement, LED display and audio alarm in addition to the CRT screen. Thus there are three modes of defect indication i.e., CRT, audio alarm and LED display.

3.3.2 The normal probe is provided for detection of horizontal defects and 70o probes have been provided for transverse defects in the head. For detection of bolt hole defects, the equipment works on the principle of backwall drop, which in the event of a bolt hole crack shows reduction in echo-amplitude of the backwall. It is also supported by separate audio alarm with distinctly different tone and LED display.

3.3.3 The introduction of double rail tester has been specifically made for enhancing the productivity of testing and as well as improving the quality and accuracy of flaw detection. Due to pre-calibrated arrangement, frequent setting of the equipment is not considered necessary.

3.3.4 Due to frequent misalignment of probes on the fishplated joints and limitations of detection of bolt hole cracks having unfavourable orientation and size, it is desirable to deploy double rail testers on LWR/CWR sections.
It is desirable to deploy only the ultrasonic machine of the “single rail tester” for  testing sections other than LWR/CWR.

3.4  Specification of rail testers

3.4.1 The single and double rail testers shall be procured to RDSO specification. The responsibility of inspection for these equipment rests with Director General, RDSO.

3.5 Types of probes:

Following types of probes other than mentioned in para 3.2 and 3.3 are also in use. Details of probes and their uses are given at Fig. 30.

45o probe For  testing Gas Pressure, Flashbutt Welded rail joints and Half Moon Defect in AT Welds below web foot junction. and SEJ.

70o , 2MHz probe (20mm circular or 20mm x 20mm square crystal)  Flange & Head testing of AT welds

700,2MHz (8mm x 8mm)    Half Moon defect in AT welds  below web foot junction.

CHAPTER-4

CALIBRATION, SENSITIVITY SETTING, MAINTENANCE OF MACHINES AND FUNCTIONS OF PROBES

4.1 Rail testing by ultrasonic method shall be carried out by conventional single rail testing trolley or by double rail tester in which ultrasonic rail testing unit is connected with probes through a junction box. Details of frequency and number of each type of probes are as under: 

Ty pe Frequency  No. of pro bes
Single Rail Tester D oub le R ail Tester
Normal/0o  4MHz  One  One each
70o  2MHz  Two(F+B)  Two(F+B) each
37o  2MHz  Two(F+B)  --

Water is used as couplant. This is supplied through a water container attached with the trolley

4.1.1 The procedure laid down for ultrasonic testing of rails is broadly divided in the following steps:

a) Visual inspection of Equipments and accessories

b) Calibration of equipment

c) Sensitivity setting of the equipment and probes

d) Checking of the equipment characteristics

e) Testing and interpretation

a)  Visual inspection of Equipments and accessories - Daily check

Ultrasonic equipment is to be inspected daily before start of work for proper function of  plug holders, cable etc.  In addition battery condition, proper functioning of echo control, proper control and smooth movement of control wheel and alignment of the probe shall be checked by the USFD operator before commencement of the Tests. After checking proper functioning of the aspects mentioned, the instrument shall be calibrated according to the procedure indicated below.

b) Calibration of USFD:

The ultrasonic rail tester is to be calibrated for 300mm depth range (longitudinal wave) with the help of a 60x50x50mm block of steel to grade  45 C8 of IS:1875 – 1992.

Procedure of calibration

(i) Switch on normal probe

(ii) Adjust the on set of the surface echo from the perspex of normal probe to  zero by using horizontal shift control /delay control, provided in the  electronic unit.

(iii) Place the calibration block below normal probe using water as couplant.

(iv) Adjust the range by H-shift/Delay and range control simultaneously so that following signals appear on the screen.

(v) The location of signals for 300mm for machines having 5/10 main scale divisions on horizontal scale has been indicated below:

On set of the surface echo from the perspex at 0 main scale div.

60mm Signal at 1/2 main scale Horiz.Div.

120mm Signal at 2/4 main scale Horiz Div.

180mm Signal at 3/6 main scale Horiz Div.

240mm Signal at 4/8 main scale Horiz Div.

300mm Signal at 5/10 main scale Horiz Div.

The equipment is now calibrated for 60/30mm of steel per main scale horizontal div. for longitudinal wave.

c) Sensitivity setting of the equipment  and probes– Weekly check

The sensitivity of the USFD equipment shall be set up once in a week with the help of standard rail pieces as mentioned below:

Sensitivity (gain) setting: For the sensitivity setting of ultrasonic equipment and the probes, the following sequence is to be maintained.:

(i) Place the testing trolley on the standard rail piece having artificial flaws as Shown in Fig. 3 for need based criteria .  Check the alignment of probes to make sure that they travel centrally in line with the axis of the rail head and web.

(ii) Set the acoustic barrier of the normal probe at right angle to the longitudinal direction of rail.

(iii) Adjust the gap of 0.2mm approx. in between the contact face of the normal probe and the sole of probe shoe.  Check the gap by keeping the straight edge of a 150mm steel scale on the sole using a feeler gauge or a stainless steel  blade.

(iv) Adjust the gap of the angle probes as in (iii) above.

(v) Open the water nozzle and regulate water flow on the probes at an optimum speed.

d)  Checking of equipment characteristics– Monthly check

The characteristics of the equipment shall be checked at least once in  a month according to IS:12666 – 88.

The following characteristics shall be checked –

i)    Linearity of time base of  flaw detector

ii)   Linearity of Amplification of flaw detector

iii)  Penetrative power

iv)  Resolving power

v)   Probe Index

vi)  Beam angle

e) Testing and Interpretation :

After sensitivity setting, actual testing of rails is to be carried out and interpreted for follow up actions.

4.1.2 Checking the function and sensitivity of probes

(a) Normal Probe:

The equipment shall be able to detect 5 mm dia. hole at the web-foot junction of the standard rail. The amplitude of the flaw echo shall be adjusted to 3 div. i.e. 60% of full screen height by the adjustment of gain control of USFD. (position of potentiometer knobs in the junction box should be set at 50% rotation).

(b) Angle probe 70o  (forward & backward) :

The equipment shall be able to detect 12 mm dia. hole for need based criteria in the head portion of the standard rail as shown in Fig. 3  by both forward and backward probes. The amplitude  of the flaw shall be set to 3 div. i.e. 60% of screen height. This adjustment shall be done by individual potentiometer provided in the junction box.

(c) Angle probe 37o (Forward & backward) (provided in single rail tester only):

This equipment shall be able to detect a 5 mm length saw cut at the bolt hole location as shown in Fig. 3 and 4 by both forward backward probes. The amplitude of signal shall be adjusted to 3 div. i.e. 60% of full screen height. This adjustment should also be done with the help of respective potentiometer.

Note :  Procedure to be followed for  adjustment in sensitivity setting  on account of variation in  rail temperature:

Following procedure shall be used for adjustments in sensitivity setting of Ultrasonic Rail tester on account of variation in rail temperature before starting the testing of rails.

(a) Switch on the Ultrasonic rail tester and keep the equipment for two minutes for thermal acclimatization of the component of the equipment before starting the adjustment in sensitivity setting operation.

(b) In the Morning at 8.00hrs.

(i) Normal Probe:  

Set the sensitivity of the equipment as per Para 4.1.2(a) and note the gain required to setup the amplitude of the signal to 60% of full screen height.

(ii) Angle probe 70 degree (Forward and Backward):  

Set the sensitivity of the equipment as per Para 4.1.2(b)  and note the gain required to set up the amplitude of the signal to 60% of full screen height.

(iii)Angle Probe 37 degree (Forward & Backward):

Set the sensitivity of the equipment as per Para 4.1.2(c)  and note the gain required to set up the amplitude of the signal to 60% of full screen height.

(iv) Note the rail temperature.

(c)  After setting the sensitivity of the probes, the ultrasonic rail tester shall be retained on the standard rail test piece in ON condition and the signal amplitude of individual probe set as per above procedure, shall be checked on hourly basis.  If the drop in the signal is observed then the drop shall be compensated by applying extra gain with use of gain control  (dB).  The height of signal amplitude is maintained to 60% of full screen height. Note the  change in rail temperature  from rail temperature at 8.00 Hrs. and corresponding extra gain used.

(d) Actual Testing:  

During actual testing on the track, the gain set by the above procedure shall be maintained depending upon the time and rail temperature during testing.  Any variation in the signal amplitude shall be compensated by giving measured extra gain (dB) as per step (c) above to carry out ultrasonic testing.

(e) Periodicity of setting the sensitivity:  

The above procedure for sensitivity calibration against temperature variation shall be carried out at least once in a month.  The adjustments in sensitivity setting of ultrasonic equipment in respect of gain (dB) shall be employed accordingly.

4.2 Machine Maintenance- Repairs and Half yearly Schedule

Maintenance: The manufacturer shall guarantee the satisfactory performance of the entire rail tester system for a period of one year from the date of commissioning of the equipment by the supplier.

For proper maintenance after expiry of the guarantee period, railway should make proper arrangements for half yearly repairs of electronic and mechanical parts either under AMC with the manufacturer of the equipment or may develop suitable departmental  facilities.

Each Zonal railway should create centralised depots for carrying out mechanical repairs and checking the Characteristics of the equipment etc., at least, once in a month.

4.3 Sectional AEN should spent at least few hours (min. two hours) each month during his routine trolley inspection with USFD team and cross check the  working  including accuracy/ sitting/calibration of USFD machines. In addition, the SE and SSE (in-charge) should also associate themselves occasionally.

4.3.1 The officer having technical control over the SE/JE (USFD) shall exercise regular checks as per Annexure-VIII of USFD Manual once in between two successive half yearly maintenance schedule carried out in the maintenance depots.

4.4 Spares:  

The recommended spares for normal maintenance of the equipment are given below: 

Sl. No. Item Number
1 0o 4MHz Double crystal probe  8Nos
2 0o 2MHz Double crystal probe  4 Nos
3 70o (F&B) Probe 2 MHz Single crystal 8Nos
4 37o (F&B) probe 2 MHz Single crystal 8Nos
5 45o 2 MHz Single crystal probe 2 Nos
6 70o 2MHz Single Crystal Probe  4 Nos
7 70o 2 MHz single crystal probe (8mm x 8mm)  2 Nos
8 Connecting Cable (Flaw Detector. with junction box) 6 Nos
9 BNC connector (Junction box to probes) 6 Nos
10 Batteries 4 Nos
11 Battery charger 1 no.
12 IIW Block (as per IS: 4904) 2 per depot
13 60x50x50mm steel block ( as per steel grade 45C8 to IS:1875-1992) 1 no.
14 Fuse (Cadtodge type) 0.5 / 0.75 6 Nos

Besides the above, the “spare” shall also include probe holder, probe shoes, wheel drum and wheel tyre. The procurement of spares for a machine shall be done from Original Equipment Manufacturer (OEMs) of that machine only,   in order to ensure compatibility of spares with the machine and to achieve consistent and assured quality of testing.  However, mechanical spares of trolley, standard items such as, battery, battery charger etc. can be procured  from open market also

4.5 Defects detectable by different probes

a) 0o / Normal probe

  1. Horizontal split in head due to presence  of seams (type 212)
  2. Horizontal split in head-web and web foot junction due to presence of rolling  seams (type 2321, 2322)
  3. Vertical longitudinal split in rail head and web due to presence of internal seams and pipes (type 213, 233)
  4. Bolt hole crack (type 135, 235)
  5. Segregation in head and web junction
  6. Flakes (type 1211, 2211)
  7. Web-lap (type 239)

b) 70o angle probe

  1. Transverse fissure (type 211) due to presence of mostly shatter cracks and some time due heavy inclusions.
  2. Transverse cracks originating from surface defects like scab (type 1221, 2221)
  3. Wheel burns (type 2251, 2252)
  4. Shelling cracks (type 1222, 2222)

c) 370 angle probe

  1. Bolt hole cracks (type 135, 235)

Typical indications received for various types of defects are indicated in Fig. 5 to 20.

(For 52 Kg. rail section, 300mm. depth range, longitudinal wave calibration).

CHAPTER 5

PROCEDURE TO BE FOLLOWED BY USFD OPERATORS FOR UNDERTAKING ULTRASONIC  TESTING OF RAILS.

5.1USFD operators must adhere to the following instructions:

5.1.1 Before testing

(i) Check the battery condition as indicated by the voltage needle or indicator lamp of USFD (or ascertain the voltage with the help of a voltmeter).  Only fully charged battery is to be used during testing.

(ii) Check proper functioning of all controls of electronic unit i.e. depth range, gain, reject, etc.

(iii) Check proper functioning of trolley and probes.

(iv) Check junction box, water outlet, probe cable contact and ensure smooth movement of trolley wheels.

(v) Maintain proper gap between probing face and probe shoe (0.2 mm).  Check with the help of a feeler gauge.

(vi) Check probe alignment by keeping the rail tester on the rail.

(vii) Calibrate the instrument everyday before conducting ultrasonic test. Set the depth range to 300 mm. with the help of 60 mm. steel cube (Five echoes shall be observed on CRT).

(viii) Set the equipment for proper sensitivity at least once a week as explained in para 4.1.1(c) of  Chapter 4.

(ix) The ultrasonic equipment shall be ensured for its characteristics as per IS: 12666 – 88 at least once a month.

5.1.2 During testing

(i) Conduct test as per procedure mentioned in Chapters 6.

(ii) Maintain proper alignment of all probes during testing, otherwise false echoes may appear.

(iii) Ensure adequate supply of water for coupling.

(iv) Check proper functioning of 37o probes and 70o probes near boltholes and rail ends at fishplated joints respectively.

(v) Look out for the back echo corresponding to normal probe throughout testing.

(vi) Lift the machine at crossings/change of rail table height at joints to protect the probes.

(vii) Mark the locations found defective as per classification.

5.1.3 After testing

(i) Maintain proper record of testing, observations, echo pattern and echo amplitude of defects in the register in the following format.

Section Line… Km from Km to…. Dateof testing S.No LOCATION (km) Rolling mark Rail/we Id No & LH/RH Defect position (head/web/foot) Defect indicated by (0o/70o/37o/45oProbe) Naturwe of echo (shift/fixed) echo amplitude Classification Remarks
Previous Present

(ii)     Charge the battery after every day’s work.

IMPORTANT

YOUR ULTRASONIC TESTER IS A DELICATE ELECTRONIC EQUIPMENT. TAKE ALL POSSIBLE CARE DURING HANDLING, TRANSPORTATION AND STORAGE TO AVIOD IMPACT, DAMAGE, ETC. LUBRICATE MECHANICAL PARTS PERIODICALLY  AND  CHARGE  BATTERY REGULARLY.

CHAPTER 6

NEED BASED CONCEPT IN PERIODIC USFD TESTING OF RAILS AND WELDS

6.1GENERAL

  1. Need based concept of testing of rails have been implemented on all BG routes? However, for other sections Chief Engineer of the railway may adopt suitable frequency on his discretion.
  2. After the initial testing of rails in rail manufacturing plant, the first retesting need not normally be done until the rails have undergone 15% of the service life in GMT as given below (para 302(i) (d) of IRPWM).

For rails rolled in April 1999 and later, the test free period shall be 25% instead of 15%. Whenever rails are not tested in rail manufacturing plant, the test free period shall not be applicable and the rail testing shall be done at the periodicity of NBC testing as the case may be right from the day of its laying in field.

6.2. FREQUENCY OF TESTING OF RAILS AND WELDS IN NEED BASED CONCEPT.

In view of the revised criteria of defect, the testing frequency of 8 GMT has been prescribed.

After the initial testing of rails in rail manufacturing plant, the first retesting need not normally be done until the rails have undergone 15% of the service life in GMT as given below (para 302(i) (d) of IRPWM). For rails rolled in April 1999 and later, the test free period shall be 25% instead of 15%.

For rails rolled in April 1999 and later, the test free period shall be 25% instead of 15%.

Gauge

Rail Section

Assessed GMT service life for T-12/72 UTS rails

Assessed GMT service life for T-12/90 UTS rails

B.G.

60KG

550

800

52KG

350

525

90R

250

375

M.G.

75R

150

225

60R

125

-

Whenever rails are not tested in rail manufacturing plant, the test free period shall not be applicable and the rail testing shall be done at the periodicity given below right from the day of its laying in field. However, the rails having sectional weight and grade equal to or higher than 52Kg/90UTS shall be ultrasonically tested covering gauge face corner of rail head on passage of every 40GMT traffic during test free period.

6.3 Frequency of testing for all BG (rail head centre and gauge face corner) and MG routes is given as under: For other sections Chief Engineer of the Railway may adopt a frequency at his discretion.

Route

Routes having GMT

Testing frequency once in

All MG routes

< 2.5

5 years

2.5 - 5.0

3 years

> 5

2 years

All BG routes(rail head centre and gauge face comer testing)

≤ 5

2 years

> 5 ≤ 8

12 months

> 8 ≤ 12

9 months

> 12 ≤ 16

6 months

 

> 16 ≤ 24

4 months

 

> 24 ≤ 40

3 months

 

> 40 ≤ 60

2 months

 

> 60

112  months

Frequency of testing of welded joints by 0o & 70o probes shall be as per para 1.2 given above.

6.4Testing of AT welded joints shall comprise of testing by probes as per table below:

S.no

Probes

Scanned area

remarks

1

0° 2 MHz

Head, web

-

2

70° 2 MHz

Head, web foot

-

3

70° 2 MHz(8mm x 8mm)

Weld foot (Half Moon Defect)

-

4

45° 2 MHz

Weld foot (Half Moon Defect)

To be done as an alternative to S. No. 3 wherever feasible.

 (Testing mentioned in item 3 and 4 above are not required to be conducted in case of initial acceptance test of welds).

The frequency of testing AT welds with above listed probes shall be as under

S.No.

Types of Welds

Type of Testing

Testing Schedule

1.

Conventional AT

Initial Acceptance

Just after execution of weld as per AT Welding Manual

2.

First Periodic Test

On Completion of one year service life by weld.

3.

Subsequent Periodic Tests

Every 40 GMT after First Periodic Test.

4.

SKV

Acceptance Test

Immediately after welding

5.

First Periodic Test

1 Year

 

 

Routes having GMT

Frequency

6.

Further test based on route GMT

> 45

2 years

7.

 

> 30 < 45

3 years

8.

 

> 15 < 30

4 years

9.

 

0 – 15

5 years

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 fish plates with two far end tight bolts.

6.5 Through Weld Renewal should be planned after the welds have carried 50% of the stipulated GMT of rails. Among the various sections, due for Through Weld Renewal (TWR) as per this criteria, Chief Track Engineer will decide inter se priority based on incidences of defects detection and weld failures.

6.6 For Flash Butt Welds

45oand 70o , 2MHz hand probing for web and flange: In case of flash butt welds normally there is no need for hand testing (with 45oand 70oprobes); however, Chief Engineer may order hand probing with these probes in case failure rates are high in his opinion.

6.7. ACTION TO BE TAKEN AFTER DETECTION OF DEFECTS IN NEED BASED CONCEPT

6.7.1 Following action shall be taken in respect of defective rails & welds    (Through rail testing):         

S.No.

Classification

Painting on both faces   of web

Action to be taken

Interim Action

1.

IMR

Three cross with red paint

The flawed portion should be replaced by a sound tested rail piece of not less than 6m length within 3 days of detection.

SE/JE (P-Way) /USFD shall impose speed restriction of 30 Kmph or sticker immediately and to be continued till flawed rail/weld is replaced.

He should communicate to sectional SE/JE (P-Way) about the flaw location who shall ensure that clamped joggled fish plate is provided within 24 hrs.

2.

OBS OBSW

One cross with red paint

Rail/weld to be provided with clamped joggled fish plate within 3 days.

SE/JE (P-Way) / USFD to advise sectional SE/JE (P-Way) within 24 hrs. about the flaw location.

 

 

 

SE/JE (P- Way)/ USFD to specifically record the observations of the location in his register in subsequent rounds of testing.

Key man to watch during

daily patrolling till it is joggled fish plated.

6.7.2 Action to be taken for defects in AT welds shall be same as at Para 2.1 above and in addition to the following shall also be applicable for welds classified as defective (DFW) in periodic testing of AT welds with 0o 2MHz, 70o 2 MHz, 45o 2 MHz, 70o 2 MHZ (8 mm x 8 mm) probes:

Classification

Painting on both faces of weld

Action to be taken

Defective weld

'DFW' with 0o

2MHz, 70o

2MHz, 45o 2

MHz or 70o

2MHz (8 mm X

8 mm) probe

Two cross with red paint

SE/JE (P.Way)/USFD hall 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 up to 75 Kmph for goods train & 100 Kmph for passenger trains on BG and 30 Kmph for goods train & 60 Kmph for passenger trains on MG.

(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.

Action to be taken for flash butt and gas pressure weld defect shall be same as given in Para 6.7.1 above.

CHAPTER – 7

LIMITATIONS OF ULTRASONIC FLAW DETECTION OF RAILS

7.0 Every scientific method/technique/equipment functions on certain principles and its applicability depends upon fulfillment of preconditions necessary to be satisfied. It accordingly implies that USFD examination is based on certain guiding principles and its flaw detection success depends upon  thorough understanding of the governing factors.

Thus, the limitations being mentioned are not per-se the deficiency of the USFD technique rather in the existing arrangement under field conditions the equipment utilised incorporates facility only for specified defects. This aspect may be kept in view and the technique is to be pursued accordingly

Limitations in respect of rail examination considering the various arrangements presently available have been elaborated below.  It may also be mentioned here that limitations with regard to AT welding i.e. defects in web foot junction half moon cracks, vertical defects in web portion etc. are no longer limitations of the USFD equipments since in the newly developed equipment special probes have been provided for detection of these defects

7.1 (i) To detect the defect efficiently, ultrasonic beam is to be directed towards the flaw perpendicularly, otherwise, the reflected beam may not be received by the receiver crystal, resulting in absence/reduction in amplitude of flaw signal in the CRT. Cracks normally have facets and hence even under misorientation provide reflecting surfaces leading to flaw indication

(ii) For detection of defects in rails, probes having incidence angle 0o, 70 o (F), 70 o (B), 37 o (F), and 37 o (B) have been provided in the USFD trolley. The angles have been chosen in a manner so as to detect defects which are generally observed during service and have been the cause of rail fractures.

The section of rail which is scanned by each type of probe has been indicated in Fig. 2A, 2B, 2C and 2D.

For detection of defects originating from Gauge Face Corner, a dedicated test set-up has been developed. This set-up incorporates three 70 o probes covering approx. the full width of the rail head and a set of two 45 o probes. The area scanned by this arrangement is shown in Fig.2E.  A defect located at 5mm from the corner is detectable using this equipment

All commonly observed defects in rails are detectable by the above arrangement.  In the event of gross mis-orientation of defect at times it may not be amenable for detection, however such situations are rare

(iii) Severe pipe in the rail may give indication of flaw echo by 0 o probe, But in case of hairline or fine central shrinkage (pipe), negligible drop occurring in bottom signal may remain unnoticed by the USFD operator. (Ref  Fig- 8 & 11 )

 (iv) For detection of bolt hole cracks, 37 o probe have been provided.  This is because the cracks emanating from bolt holes are generally oblique and propagate in the zig-zag manner.  However, bolt hole cracks are also detectable by using 0 o probe since they obstruct the path of sound waves and lead to drop/loss of back wall echo 

37o  probes have been provided both in forward and backward direction.  Forward probes detect defects in second and fourth quadrant where as back ward probes detect cracks in 1st and 3rd quadrant.   At fish plated joint, as shown in Figure 22, if the cracks are not favourably oriented detection may not be possible.  Similarly, if the cracks are propagating vertically downwards or upwards,  detection is not possible.  In case of double rail testers which do not have 37o probes, detection is possible by 0o probe. Under such situations if the cracks are so located that they are unable to be  scanned by 0o probes, initially due to smaller size, such  cracks may not be detected

(v) If sensitivity of the machine is poor or battery gets discharged the operator may miss the flaw signal.  Hence, it is essential to ensure full charging of the battery.

( vi)  The ultrasonic probes used in the rail testers have a frequency of 4MHz (longitudinal wave) and 2MHz (transverse waves).  Therefore, cracks lesser than 0.8mm size cannot be detected by the present arrangement.

The sizes and frequency of the probes employed in the single rail tester/double rail tester are as under.

S.No Probe type  Size of Crystal  Shape of crystal
 
Frequency
 
1 0 o(Double crystal) 18mm Circular 4MHz
18mm x 18mm Square
2 70o(Single crystal)  20mm Circular 2MHz
20mm x 20mm Square
3 37o (Single Crystal) 20mm Circular 2MHz
20mm x 20mm Square

 (vii) 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.

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.

7.2 Testing of SEJs,  points and crossings

Testing of these components is accomplished in the same way as rails.   However due to its 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 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 crossings or in the USFD manual (chapter 10 & 11).

Since the testing of SEJs, Points and Crossings specially in the nose portion poses practical problems during USFD examination of the track, it is essential to carry out thorough testing of these items before they are put in to service and also before they are taken up for reclamation.

7.3 Testing on sharp curves,  gradients, slack gauge etc.

The USFD trolley has been designed to operate under normal conditions of gauge.  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.  This is indicated by loss of backwall echo or also by alarm provided in DRTs for backwall drop.  Wherever it is not possible to ensure proper acoustic coupling due to these reasons,  testing by hand probing or by single rail tester may be resorted to. Acoustic coupling needs to be ensured under all circumstances to detect the flaws.

CHAPTER 8

PROCEDURE FOR ULTRASONIC TESTING OF ALUMINO- THERMIC WELDED RAIL JOINTS

8.1Scope:

Following types of testing for Alumino Thermic (AT) welds have been prescribed. These are:

a) Testing of weld head/web, which gets covered during through periodic rail testing by SRT/DRT as per Para 6.8. The frequency of testing in this case is as per Para 6.8.1.1. As per this testing defects detected in weld heads are classified as ‘IMRW’ and ‘OBSW’ vide Annexure II. The action to be taken for such defective welds is as per Para 6.4.

b) Periodic testing of complete weld by hand probing of weld head/web and bottom flange, using 00 2MHz, 700 2 MHz, 450 2 MHz and 700 2 MHz (8mmX8mm) probes.  The frequency of testing in this case is as per Para 6.8.2.1. As per this testing defects detected in welds are classified as ‘DFW’. The action to be taken for such defective welds is as per Para 6.6.

c) Besides this, welds are also tested after their execution using 00 2MHz and 700 2MHz probes. This test is termed as Initial Acceptance Test. As per this testing, defects detected in welds are classified as ‘DFW’. The action to be taken for such defective welds is as per Para 8.10.

This Chapter covers the requirement of complete ultrasonic testing of Aluminothermic welded rail joints by hand probing immediately after execution of the weld described at c) above and for periodic examination of complete weld described at b) above only.

8.2 Apparatus required:

8.2.1  Equipment:

Any RDSO approved model of ultrasonic equipment for Alumino-thermic welded rail joints as per RDSO specification No. M&C/NDT/120/2001(Rev. 2) May. 2005 or its latest version. 8.2.2  Probes: The following probes having Lead zincronate- titanate crystal shall be used for Ultrasonic testing of Alumino-thermic joints.

a) Normal ( 0° ) 2 MHz, 18 mm. φ  Double crystal.

b) 45°/ 2 MHz, 20mm.dia. or 20mm.x20 mm.( square ) crystal size, Single crystal –1 no.

c) 70°/2 MHz, 20mm.dia. or 20mm.x20 mm. ( square )crystal size, Single crystal -  1 no.

d) 70°/2 MHz, 8mm.x8 mm. crystal size, Single crystal   - 1 no.

8.2.3  Cables: C

o-axial cable for each probe shall be used .The length shall not be more than 2.0 metre. 8.2.4 Couplant: soft grease/oil shall be used as couplant.

8.3 General Condition:

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 rail head surface shall be dressed to obtain reasonably flat and smooth surface. The flange of the weld up to 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.

8.3.1  Visual Examination:

All the welded joints shall be cleaned and examined carefully to detect any visible defects like cracks, blow holes. Any joint which shows any visible defect shall be declared defective.

8.4 Sensitivity setting procedure:

8.4.1 Standard test rail:

The sensitivity of the ultrasonic equipment shall be set with the help of a standard AT welded rail piece of 1.5 m length having a simulated flaw at standard locations as shown in Fig.23 (a).

8.5  0°/2 MHz, Double crystal Normal Probe:

This scanning is used to detect  Porosity , Blow hole, Slag inclusion  in head and up-to mid web of the AT welded joint.      

8 .5.1   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.

8.5.2 Sensitivity setting:

Place 0°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.

8.5. 3 Test Procedure:

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.

8.5.4 Defect classification:

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). 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).

8.6 70°/ 2 MHz (Head scanning):

This scanning is used to detect lack of fusion, porosity, blow hole, slag inclusion, cracks in head of AT welded joint.

8.6.1  Calibration:

The equipment shall be calibrated for a depth range of 300 mm. (Longitudinal wave).

8.6.2  Sensitivity setting:

Connect the 70°/ 2 MHz by means of co- axial cables and select (T+R) mode. Place the probe on the railhead directing the beam towards 3mm. 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 . This gain shall be used for testing.

8.6.3  Test procedure:

Place the probe on the rail head on one side of the AT welded reinforcement and move toward the weld in zig-zag manner. This exercise shall be repeated 2-3 times. The same shall be carried out from both sides of the weld.

8.6.4  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).

8.7 450 / 2MHz probe:

This scan is used to inspect the bottom of weld foot to detect half moon shaped defect.(Fig. 25)

8.7.1  Range calibration:

The equipment shall be set for a depth range of 500mm for longitudinal wave using 0o  probe

8.7.2   Sensitivity setting:

Place 450 /2MHz probe on the rail head surface at a distance equal to height of rail from the centre of the AT weld.(Fig. 25).  Move the probe 20mm either side of this position (probe index marking) to pick up half-moon crack in the central region of weld reinforcement as shown in Fig 26.  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 400mm for 52-kg 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 .

8.7.3  Test Procedure:

The probe (450/2MHz probe /single crystal) shall be placed on the rail head at a distance equal to height of the rail from the centre of AT weld (Probe index marking) under test with same sensitivity as per para 8.7.2.  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. 8.7.4  Defect classification: Any flaw signal obtained by this probe of 20% height or more shall be treated as defective AT welded joint (DFW).

8.8       70o/2MHz size (8mm x 8mm) probe:

This technique shall be used when due to presence of hole in the web, it is  not possible to use the procedure mentioned in para 8.7.

8.8.1 Range calibration:

The equipment shall be set for a depth range of 300mm (longitudinal wave) by manipulating the depth control  suitably.

8.8.2  Sensitivity setting:

One 70o/2 MHz, size 8mm x 8mm, size probe shall be connected to the unit by means of one co-axial cable.  The selector switch shall be in T+R (single crystal) mode.  Apply the Couplant and place the probe at a distance of 100mm from edge of the weld near to upper zone of the flange with beam direction towards simulated flaw (Fig. 25).  Move the probe slightly in zigzag manner to get reflection from simulated flaw. Set the height of signal to 60% of full screen height.  This gain level will be utilised during testing.

8.8.3 Test procedure:

70o probe shall be placed on the upper zone of the flange at a suitable distance (100mm approx.) with beam directing towards web-foot 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 sides of weld collar. Any moving signal on the screen shall be recorded. This method is not capable  of detecting all half moon defects due to its position of probing.

8.8.4  Defect Classification:

Any flaw signal of height 20% of full screen height or shall be treated as defective AT welded joint (DFW).

8.9 Flange testing by 70°/2 MHz, 20 mm x 20 mm single crystal probe:

This scanning is done for detecting lack of fusion, porosity, blow hole, slag inclusion in flange of AT weld.

8.9.1 Range calibration:

The equipment shall be set for a depth range of 300mm (longitudinal wave) by manipulating the depth control suitably.

8.9.2  Sensitivity setting:

70°/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 Fig. 23(a) and manipulate gain control to obtain a maximum signal height 60% full screen height on the screen.

8.9.3  Test Procedure:

70° probe shall be placed on the flange at a suitable distance (180mm.) corresponding to position ‘L’in Fig. 24(a) such that ultrasonic waves are directed towards the weld. The probe shall thereafter be moved slowly in a zig-zag manner towards the weld. Similar testing shall be carried out from ‘C’ and ‘U’ region as shown inFig.24(a).

8.9.4  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).

8.10       Initial Testing :

A thermit welding done in situ shall be joggled fish plated with two clamps till tested as good by USFD.

8.10.1 The defective joints based on the criteria mentioned in preceding para 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.

8.11 Periodic testing of welds in service

8.11.1 The periodic  testing of welds using  00 2MHz, 700 2MHz, 450 2MHz and 700 2MHz (8mmx8mm) probes shall be done the as per para 6.8.2.1

8.12 Procedure for  initial and periodic Ultrasonic Examination of 75mm gap AT welded Joints

8.12.1 Standard Test Sample –

The sensitivity of ultrasonic equipment shall be set with respect to AT weld standard test sample of 1.5 m length having a simulated flaw at standard location as shown at Fig.23 (b).

8.12.2  Sensitivity setting:

The signal from the simulated flaw of 3mm dia. hole in the head shall be set to 60% of full screen height with 00, 2 MHz and 700, 2 MHz probes for detection of discontinuities in the rail head.  For Flange testing a signal from a saw cut of 30mm in the weld metal  in the flange 15mm away from the edge of the weld collar as per Fig. 23(b) shall be set to 60% of full screen height using 700 2 MHz probe.

8.12.3 Defect Classification:

a) Head - With 00 & 700 probes, rejection criteria will be same as for 25mm gap AT weld joint. ( Para 8.5.4 and Para 8.6.4)

b)Flange- With 00 & 700 2MHz/  probe,de Any moving signal of height more than 20% of the full screen height shall be treated as defective weld (DFW)

Note : Guidelines for the Operators:

a) The correctness of angles and index marking of the probe shall be ascertained before testing.  Only probes meeting the specified values shall be used during testing

b) 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:

(i) Horizontal distance of the flaw from probe index mark shall be calculated using formula

H= S Sin θ   [Fig.24 (b)]

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=Rl /1.82

S=(Horizontal Screen Reading (in No. of Div.) x Rs )/(Total No. of divisions on Horizontal Scale)

(ii) 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.

(c) 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.

CHAPTER 9

ULTRASONIC TESTING OF FLASH BUTT AND GAS PRESSURE WELDED JOINTS

9.1 Scope:

This procedure covers the ultrasonic testing technique of flash butt and gas pressure welded rail joints by using pulse-echo, A-scan examination method of detecting weld discontinuities.

9.1.1  This practice utilises only shear wave probe having 450 & 700 refracted angle in steel, 450 probes to test head and 700 probe to test web and foot of the welded joints.

9.1.2 Significance: It is essential that evaluation be performed properly by trained and qualified personnel.

9.2     Code of procedure

9.2.1    Equipment and accessories

(i) Pulse-echo type ultrasonic flaw detector approved by RDSO.

(ii) Two single crystal 450  2 MHz probes, one single crystal 700  2 MHz probe.

(iii) 00 4 MHz double crystal probe (00 2 MHz single crystal probes, shall be used to check equipment characteristics.)

(iv) Battery with specific voltage suitable for the USFD to be used.

(v) Battery charger

(vi) Voltmeter

(vii) Standard rail piece of 2.5 m length having standard simulated defects at standard locations (Fig. 4).

(viii) Calibration block 60 X 50 X 50 mm of steel grade 45C8 to IS : 1875 – 1992.

(ix) Steel measuring tape.

(x) IIW-VI or V2 block

9.3    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 IIW 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 200 mm.

Couplant: The couplant should wet the surfaces 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 60 X 50 X 50 mm steel block of steel  to grade 45C8 to IS : 1875 – 92 .

9.4     Calibration and sensitivity setting

(i) Calibration the ultrasonic flaw detector for 250 mm depth range (longitudinal wave) with help of 0o 4 MHz double crystal probe. Adjust the onset of surface echo from the perspex wedge of the probe at zero on the screen by using zero shift/delay/shift control. In case the gain setting is high, multiple echoes of the surface echo may occur.

(ii) Place the 0o probe on the calibration block.

(iii) Adjust the depth and zero shift/delay/h-shift controls simultaneously so that onset  of the following signal appears on the screen (Incase of machine having 5/10 main division on horizontal scale):

On set of the surface echo

: at 0

main scale hor. Div.

-do-

50 mm

: at 1/2

-do-

-do-

100 mm (i.e.Ist multiple)

: at 2/4

-do-

-do-

150 mm (i.e. 2nd multiple)

: at 3/6

-do-

-do-

200 mm (i.e. 3rd multiple)

: at 4/8

-do-

-do-

250 mm (i.e. 4th multiple)

: at 5/10

-do-

(iv) Remove the 0o probe and connect the 45o probes, one to transmitter connector and the other to receiver connector. Place the 45o probes on standard rail piece as shown in Fig. 27 (a). Move the probes forward and backward alternately and set the gain to achieve 60% height of full screen from a 5 mm dia drill hole drilled in head.

(v) Remove the 45o probes and connect 70o probe (Turn the probe selector switch to single crystal mode). Place the probe at approximately 100mm from the 5 mm dia hole on the web as shown in Fig. 27(b). Move the probe to and fro from 5 mm dia hole and set the gain to achieve 60% height of full screen and this gain level shall be reference gain for testing of web and flange of the joints.

(vi) The equipment is now calibrated for depth range of 60 mm per main scale division of longitudinal wave and gain of the UFD is set separately for conducting the test using 45o and 70o probes.

9.5 Examination  of flash butt/gas pressure welded rail joints in depot (Initial testing):

Examination of flash butt welded joints is performed separately for the rail head, web and flange. In case of scanning of weld at rail head, two single crystal 45o angle probes of 2.0 MHz shall be used, one of which shall act as transmitter and the other as receiver. A 70o single crystal angle probe of 2 MHz frequency shall be employed for examining the welds at web and flange. All the above probes have index marks on their housing to denote the point at which the central beam emerges.

9.5.1 Testing of weld at rail head:  

After calibration has been done, the two 45o angle probes shall be connected to the unit by means of two probe cables one acting as transmitter and other as receiver. The probe selector switch shall be operated in T/R mode in which one works at Transmitter and the other as receiver.
Used machine oil, water or grease (of adequate viscosity) shall be applied as couplant along the right and left hand side faces of the rail head, up to 100 mm from the joint on both sides of the weld.

9.5.1.1 Two 45o angle probes shall be placed and moved along the two side 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. 27 (a). In order to examine the entire width of rail head as well as the height, maximum mutual displacement at start shall 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. 27(a). 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 traverse 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.

9.5.1.2 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 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 on 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 center of the rail head as shown in Fig. 27(a). 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 flaw signal shall be considered defective.

9.6 Testing of weld at rail web and flange

9.6.1 Setting of sensitivity:

To examine the web and flange locations of flash butt welded rail joints the gain level of flaw detector’s setting shall be changed and set as per para 9.4(v) and probe selector switch shall be turned to single crystal operation i.e.  in T + R mode.

9.6.2 Couplant:

Used machine oil, water or grease (of adequate viscosity) shall be applied as couplant along the right and left hand side surfaces of the rail web and foot up to 100 mm and 180mm. respectively away from the joint on both sides of the weld.

9.6.3 Testing procedure:

 The probe shall be positioned 100 mm away from the weld in web region and transversed in a zigzag manner towards the weld. The probing  should be done on the web so as to cover the entire width as  shown in Fig 27(b).   Testing of the flange should be done as per the procedure described in Para 8.9.3 (Fig.24 a).

9.6.4 Detection of defects:

To detect 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 flange 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, 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.

9.7     Periodic Testing

9.7.1   Frequency of testing with 00 & 700 probe:

Same as for rails and shall be carried out along with rail testing.

9.7.2 Frequency of testing with 700 hand probing for web and flange:  

Normally there is no need for hand testing after first testing of welds.  Additional hand probing be carried out as per para 6.8.2.2.

CHAPTER 10

ULTRASONIC TESTING OF RAILS REQUIRED FOR FABRICATION OF POINTS AND CROSSINGS

10.1 New rails without bolt holes and suitable for laying in track are used for the  fabrication of points and crossings.  These rails, therefore, do not have any chance of  fish bolt hole cracking or any progressive type of defects.  The defects like pipe,  seam, lap, inclusions, segregation can only be expected in these rails.  Therefore, in  the procedure for ultrasonic testing of these rails only normal probe (0o) is required.   Probing shall be carried out from top of the rail head, side of the rail head and side of  the web. The use of angle probe has not been included as transverse progressive  crack of fish bolt hole cracks are not expected.  This testing will be undertaken  besides visual examination of rails for freedom from any surface defects.

10.2   Scope:

This chapter stipulates the ultrasonic testing technique of new rails required for fabrication of points and crossings by hand probing using ultrasonic flaw defector and lays down the acceptance standard.

10.3   Accessories

10.3.1 Probes:

One single crystal normal probe 20/25 mm dia, 2/2.5 MHz frequency for checking the efficiency of the ultrasonic flaw detector.  One double crystal normal probe of 4 MHz frequency, 18mm dia (overall), stainless steel casing and with perspex insert having a path length equal to 50mm of steel required for testing of  rails. Both the probes shall meet the requirement of the tests stipulated in equipment specification.

10.3.2 Battery:

The battery shall be a rechargeable, plug-in type (preferably Ni-Cd type) 6V/12V suitable for working about eight hours continuous operation per charge.

10.3.3  Battery charger:

The battery charger shall be suitable for charging the battery provided with the flaw detector.

10.3.4  Co-axial cable:

Two meter co-axial cable fitted with BNC connector for connection with single crystal probe.

10.3.5 Calibration block:

60x50x50mm  block of steel to grade 45C8 of IS:1875 – 1992.

10.3.6 Standard test rail:

The rail piece shall be 250/300 mm in length preferably of the  same section used for the manufacture of crossings, having 1.5mm dia and 2.0mm dia flat bottom holes drilled along the central axis of the head, web and foot locations as indicated in Fig. 28.

10.3.7 Checking the sensitivity of the probe:

The double crystal normal probe shall be  able to detect 1.5mm, 2.0mm and 2.00mm dia flat bottom holes in the rail head, web and foot respectively of the standard test rail.  The amplitude of the  peaks  shall  be set at 60% height.

10.4    Testing procedure

10.4.1 Surface preparation:

The probing faces of the rail shall be cleaned with hard wire brush to make it free from dirt, etc. for achieving acoustic coupling.

10.4.2 Checking the equipment:

Check the correct functioning of the flaw detector or  probe and adjust the sensitivity of the unit with standard test rail as in para 10.3.7

10.4.3 Calibration:

Calibrate the unit for 300mm range for testing the rail while probing  from top of the rail and for 100mm range while testing from the side head and web.

10.4.4 Testing:

After calibration of the unit the rails shall be tested manually using double crystal normal probe 4.0 MHz frequency with water/oil as couplant.  The rails shall be tested by probing from the rail head top, rail head side and web.  Typical oscillogram pattern for various probe positions are given for guidance as indicated below:

(i) Probing from the rail table:

Oscillogram pattern for sound rail will be as given at Fig.5.

The pattern obtained on the defective rails will be as in Fig.14 for segregation, Fig.11 for vertical longitudinal split in web.

(ii) Side probing from rail head:

Oscillogram pattern for sound rail shall be as given at Fig. 9.

The pattern obtained on defective rails will be as given in Fig.10 for vertical split in head.

(iii) Side probing from web:

Oscillogram pattern for sound rail shall be as given in Fig.12.

The pattern obtained on defective rails will be as given in Fig.13 for vertical split in web.

10.5 Acceptance standards:

Any flaw peak appearing on the cathode ray tube of amplitude higher than 60% of the full screen height shall indicate a defective rail and such rails shall not be used for fabrication of points and crossings

CHAPTER 11

ULTRASONIC TESTING TECHNIQUE OF WORN OUT POINT AND SPLICE RAILS PRIOR TO RECONDITIONING BY WELDING AND SWITCH EXPANSION  JOINT

11.1. The worn out points and crossings are taken to the Reconditioning Depot for reclamation of the same by suitably depositing hard facing electrode over the worn out areas to enhance the service life and also for effecting savings thereby.  As per extant practice, the worn out areas of the wing rails and point and splice are ground for removing loose metals and oxides over the surface before undertaking welding. Freedom from any fatigue crack over the surface to be built-up is also ensured by MPI/DPI before reclamation.  As the nose portion of the crossing consisting of the point and splice is subjected to heavy impact and dynamic stresses during service, it is felt necessary to check them ultrasonically to ensure their freedom from any internal flaw prior to reconditioning, so that the defective points and splices can be rejected for ensuring safety in the train operation.

11.2    Scope: This testing procedure stipulates the ultrasonic testing techniques of worn out point and splice rails which need reclamation. Zone I of the crossing shall be tested utilising probes fitted in USFD trolley and zone II and III shall be tested by hand probing with 0o and 70o probes wherever necessary for detection of internal flaws {Fig.29(a)}. The testing is required to be carried out in dismantled condition in the welding depot.  It also suggests to subject some vulnerable locations to MPI/DPI to ensure freedom from surface/sub-surface defects.

11.3   Personnel qualification:

 It is essential that evaluation be performed by properly  trained and qualified testing personnel.

11.4 Equipment and accessories

11.4.1 Equipment:

Pulse-echo type ultrasonic flaw detector approved by RDSO.

11.4.2 Accessories

(i) Probes: The rail test trolley shall have following probes made of PZT, barium titanate or similar type of piezo electric crystals:

(ii) (a)  Double crystal 4 MHz, 18mm(crystal dia) 0o probe-1 No. fitted in trolley.

(b)  Single  crystal 2 MHz, 20mm(crystal dia)70o probe- 2 No. fitted in trolley.

(c)  Single crystal 2 MHz, 20mm(crystal dia) 70o probe -1 No. for hand probing.

(iii) Battery with specific voltage suitable for the USFD to be used.

(iv) Battery charger

(v) Voltmeter.

(vi) Standard rail piece of 2.5m length having standard simulated defects at standard locations (Fig.4)

(vii) Calibration block 60 x 50 x 50 mm of steel grade 45C8 to IS: 1875 – 1992.

(viii) Steel measuring tape.

(ix) IIW-VI or V2 Block

(x) Co-axial cable-2.5m length fitted with BNC connector for connection with single crystal probe.

11.4.3  Pre-requisites

(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 on IIW block as per IS: 12666- 1988.

(iii) The couplant should wet the surfaces of the probes and the scanning surfaces properly. Depending upon the availability and feasibility of the testing – water, oil or grease can be used as couplant.

(iv) Calibrate the depth range of USFD with help of calibration block for 300mm depth range (longitudinal wave) with the help of 0o double crystal 4 MHz probe.  The equipment is thus calibrated for depth range of 60/30mm per main scale division for longitudinal wave for equipment having 5/10 main scale div. on horizontal scale.

11.5 Checking the sensitivity

11.5.1 0 o and 70o probes fitted with the rail tester trolley shall be able to detect 5mm dia flat bottom hole at the foot/5mm dia through hole at web-foot junction and 5mm dia through hole at head respectively of the standard 2.5m long test rail. (see Fig.4) and set gain of the USFD so that the flaw signal amplitude is adjusted to 60% of the vertical screen height.

11.5.2 During hand probing by 70o single crystal 2 MHz probe it should be connected with the equipment by a coaxial cable.  Turn the probe selector switch to single crystal operation and set the gain of the USFD with 5mm dia drilled hole in the head of the standard rail by side probing.  The flaw signal amplitude shall be similarly adjusted to 60% of the vertical screen height.

11.6 Testing procedure {Ref.Fig.29(a)} :

The points and splices of different turnouts shall be divided into three zones, viz.

Zone –I :

(Towards

the heel

of the

crossing)

To  be tested by the  rail tester  trolley according to  accessibility   utilising 0and 70o probes.

Zone-II:

(Middle

of the

crossing)

To be tested by 0o and 70o probes provided in the rail tester trolley by hand probing from the rail head top surface.

Zone–III:

(Toward

the nose

of the

crossing)

To be tested by the 70o 2 MHz single crystal probe by hand probing at the head portion from both the sides of the head. The web and flange location of zone III shall be tested by the same probe.

Besides the above, the bolt hole locations at the web shall be thoroughly examined visually and magnetic particle/dye penetrate inspection shall be conducted to ensure freedom from cracks since ultrasonic testing of the bolt hole strip on the web is not feasible

11.7  Acceptance standard

Zone I,II&III:Any point or splice when tested with gain setting as specified  in para 11.5.2, showing any moving signal shall be considered as defective.

11.8 PROCEDURE FOR ULTRASONIC TESTING OF SWITCH EXPANSION JOINT

11.8.1 A number of SEJs have been found to fail in service due to fatigue cracks generated from the bottom of the rail and also from rail head endangering safety. It was therefore considered essential to develop a procedure for detection and classification of defects in SEJs . Details of the procedure are described below.

11.8.2 Scope: This procedure stipulates the ultrasonic testing technique of new SEJs as well as those in service and lays down the acceptable standard with regard to defects noticed. In view of the design of the SEJs, testing is to be accomplished by hand probing.

11.8.3. Accessories:

11.8.3.1 Probes:

The following probes shall be used for ultrasonic examination of SEJs

(i) 0oNormal probe, 18mm dia./2MHz, Double crystal for time scale calibration.

(ii) 45o/2MHz, 20x20mm PZT crystal, Single crystal for locating flaws in middle of web-flange area.

(iii) 70o/2MHz, 20x20mm PZT crystal, Single crystal for locating flaws in nose of the SEJ.

(iv) A 60mmx50mm x 50mm rectangular block of steel to grade 45C8 of IS1875-1992.

11.8.3.2     Couplant:

Water/soft grease/thick oil shall be used as couplant.

11.8.3.3   Cables:

Co-axial cable for each probe shall be used.  The length shall not exceed 2 meters.

11.8.3.4    Standard test piece:

 A 1000mm long rail piece having nose of SEJ stock shall be used for preparation of standard test piece.  One simulated flaw of 3mm x 5mm shall be made in the bottom of flange as shown in fig 29(b) at location A.  This simulated flaw shall be used for sensitivity setting of 45o angle probe.  Another 5mm. Dia. through hole shall be made in the rail head at location B, 25mm. below the top of the rail surface and away from nose portion (as shown in fig. 29 (b) for sensitivity setting of 70o angle probe.

1 1.8.4   Range calibration:  

The  time  scale  shall  be  calibrated  for 500mm longitudinal wave for setting depth range for 45o angle probe and 300mm longitudinal wave for 70oangle probe with the help of 0o (normal)  probe. Rectangular block of 60mm.x50mm.x 50mm steel to 45C8,IS- 1875-1992 shall be used.

11.8.5       Sensitivity setting

11.8.5.1 The depth range shall be set for 500mm longitudinal wave using normal probe.  There after 45o /2MHz single crystal probe shall be placed on the rail head at a distance of 160mm (for 52 Kg.)/ 175mm.(For 60 Kg.) approx. from the junction of flange as shown in Fig. 29 (c). The probe shall be placed so as to direct the beam towards the simulated flaw as shown in Fig. 29 (c).  The probe shall be moved towards the saw cut in zig-zag manner so as to get maximum reflection from saw cut. The height of this reflected signal shall be adjusted to 40% of full screen height with the use of gain control.  This gain setting shall be utilized during examination of SEJ using 45o angle probe while maintaining the movement towards the nose of SEJ.

11.8.5.1.1 Any flaw peak of amplitude higher than 20% of full screen height shall be classified as IMR. The SEJ should be adequately protected till it is replaced.

11.8.5.2 70o angle single crystal probe:  The depth range shall be set to 300mm longitudinal wave with the help of normal probe.  Thereafter 70o/2MHz single crystal probe shall be  placed on the rail head at a distance of  approx. 70mm from 5mm dia hole so as to direct the beam towards the hole.  The reflection from 5mm dia. hole shall be adjusted to 60%of full screen height with use of gain control . This gain setting shall be utilized during testing of SEJ while testing with 70o angle probe with probe movement towards SEJ.

11.8.5.2.1 Any flaw peak of amplitude higher than 20% of full screen height shall be classified as IMR. The SEJ should be adequately protected till it is replaced.

11.8.6 Testing frequency :

Same as that for normal track as stipulated in the need based concept.

Note: The probe positions indicated are for 52kg rail section. For other rail sections, the distance may be suitably modified

CHAPTER 12

ULTRASONIC TESTING OF RAILS BY SPURT CAR

12.1  Introduction

12.1.1 Continuous testing of rails by manual flaw detectors is strenuous and demands continuous concentration on CRT screen, also the speed achievable is only 2/6 track km in a day. An equipment which can shortlist likely defective spots quickly can improve the effectiveness of the testing.

12.1.2 Self Propelled Ultrasonic Rail Testing (SPURT) Car has been procured for this purpose and is in operation since May’88 over Indian Railways. This car tests both the rails while traveling up to 30 km/h. Most of the testing operations have been automated in this car.

12.2 Description of SPURT Car

12.2.1 SPURT Car has water supply system with a capacity of 4000 litres guiding system for probe beam positioning and air system for lifting and lowering of probe. Probes used are of the following types:

Probes

Defect type

0o (Normal)

Horizontal flaws

70o Central

Vertical transverse flaw

(forward and backward)

 

70o side wise

Vertical transverse flaw

35o (forward and backward)

Star cracks

550

Vertical longitudinal flaws.

12.2.2 As SPURT car tests at higher speed, observation for flaws can not be  done manually.  Identification of defect is done electronically according to laid down logics. Also it has computer for tabulating, printing and storage of data.

12.2.3 Comparative characteristics of manual USFD tester and SPURT car are tabulated below:

SPURT car USFD manual machine 
Real time recording of defects No automatic recording of defect.
Analysed by computer hence less strenuous Concentration.Testing is objective Testing requires sustained and intense Testing depends on the interpretation by operator
Testing of 80-120 track km per day.  Testing of 2 to 6 track km per day.
Testing of 2 to 6 track km per day.and severity classification is dependent on visual information. So classification is not possible Ultrasonic information is supplemented by visual information also. So severity classification is done
Repetition of test at a spot is difficult due speed and path constraint  Repetition of test at a spot can be conveniently to done

To take advantage of both machines, the method used by Railways having SPURT car is to use both as complementary to each other. SPURT car short lists the likely defective spots and manual equipment is used to check only these locations. During this check the severity classification is done.

12.3  Locations not tested by SPURT Car

12.3.1 Fishplated joint causes damage to SPURT car probes and also efficacy of testing reduces depending upon condition of joints, therefore only LWR/CWR lengths are normally tested by SPURT car. Also probes are lifted on points and crossings, SEJ’s and buffer rails and these remain untested. At locations fitted with ground rail lubricators, probes are also lifted and hence testing is not done at such locations.

12.3.2 Testing of rail with surface defects like wheel burn and scab is also to be done manually.

12.3.3 The real time out put as well as final defect report contains the information about stretches not tested by SPURT car.

12.4 Role of Railways

12.4.1 From the time of drawing a programme by RDSO for testing of rails by SPURT car until the testing work gets completed, action in Railways is required at three levels.

(i) Headquarter

(ii) Devision and

(iii) USFD and sectional SE/JE(P. Way)

12.4.2 Headquarter

12.4.2.1 Programme of testing will be drawn by RDSO in consultation with CTE of a Railway. For this, information about LWR stretches, frequency of testing, rail sections will be made available by USFD cell of the Railway to RDSO for drawing the programme of testing.

12.4.2.2 On  receipt  of  the  programme  from  RDSO,  Engg.  headquarter  is to get the confirmation of path and deputation of crew by operating branch. It is to be ensured that proper messages are transmitted by operating branch to all concerned. Reference is also to be made to Rly. Board’s letter No. 90/Track III/TK/72 dated 9.7.90 in this regards. Relevant extracts are reproduced below: The monitoring special shall be accompanied by following officers from the

railway and division:

All routes :Any officer from the track modernization cell preferably dealing with rail testing and SE/JE(P.Way)/USFD of the section.

Division :Sectional DEN/AEN

One nominated Sr.DEN/DEN at the divisional headquarter shall ensure that there is proper liaison in the control office to ensure suitable path for the monitoring special. Any other special requirement as indicated by RDSO should also be taken care of. The confirmation of the programme is also to be conveyed back to RDSO.

12.4.2.3 Headquarter is also to ensure through divisions for any other assistance requested by RDSO for successful and effective testing by SPURT car. Clear instructions are to be issued to division that sectional AENs/DENs should accompany SPURT car and movement should be watched by Sr.DENs with proper intercommunication.

12.4.2.4 For follow up testing within reasonable time of 10-15 days after the SPURT car run, additional USFD machines are to be sent to the section. The distribution of machines and operators is to be programmed at this stage by USFD cell of headquarter. Also push trolley are to be provided to USFD operators so that  average progress of about 8 km follow up testing is achieved.

12.4.3 Division

12.4.3.1Though the programme of running is confirmed initially by COM, yet the real day-today control is at divisional level and divisions role is most critical in effective utilization of SPURT car.

12.4.3.2On receipt of testing programme from headquarter, Sr.DEN will study the same along with COM confirmation and actual train paths available. Slight modifications in timing, keeping the constraints that

(i) the testing can start earliest 8 o’clock

(ii) spread of working should not be much and  (iii) testing to be done in day light, is possible. Keeping all these in view, testing path is to be planned in consultation with operating branch and the path schedule is to be drawn and get confirmed by operating branch. RDSO official in charge of SPURT car is to be informed about the change, in advance.

12.4.3.3At the time of testing, sectional AENs, SE/JE(P. Way) and SE/JE(P. Way)/USFD are to accompany the test special. During the run, AEN will liase with control, Sr.DEN and Sr.DOM regarding path. It should be ensured that movement is through main line only to avoid any length untested.

12.4.3.4At the end of the run SPURT car is to stabled in proper siding. It may also require fuelling and watering arrangements as required for SPURT car, for fuelling, watering, shunting and placement, are all to be arranged by AEN.

12.4.3.5AEN is also to ensure that SE/JE(P. Way) USFD knows clearly about the follow up testing to be done. In case knowledge is lacking, RDSO official will coach the SE/JE(P. Way) about the procedure to be followed by him for follow up testing.

12.4.4  SE/JE(P. Way) /USFD

12.4.4.1  During testing

(a) SE/JE(P.Way) will accompany testing run of SPURT car. He will supply the information regarding the section of rails, GMT and left and right rail convention followed in the section.

(b)  SE/JE(P.Way) will carry results of last USFD testing with  him for prima facie checking of results reported by SPURT car. (c) After the testing run SE/JE(P. Way) /USFD will collect the testing output for real time, final defect computer out put and statement of the untested stretches for follow up work.

12.4.4.2 Follow up testing

(a) SE/JE(P. Way) /USFD are required to carry out follow up testing on the locations, indicated in final defect report, which gives the location of the defect in kilometer , defect type, and its size. Also the location is paint marked and thus gets identified. The paint marks will be more than the defects contained in final defect report, the excess being caused by definite noise edited later by SPURT car operator. For the sequencing, real time report can be used as in this report number of defects will equal number of paint marks. Ground features like bridges, L-xing, etc. are also reported in output for use as reference in locating a defect.

(b) After locating a spot, the SE/JE(P.Way) will carry out testing for a length of 2 m i.e.  1 m on either side of the spot and classify the defect, if any, according to the criteria laid down. There is a possibility that the spurt car may have been calibrated on conventional threshold values of defect size in rail while the Need Based concept of USFD testing of rails based on a different defect size in rail has already been introduced in the section being tested.  In such a situation the follow up testing should be done with the Need Based concept of USFD testing only.

(c) Occasionally spots reported defective by SPURT car in its final defect report may be found with no defect during follow up testing. Over reporting can occur for following reason.

(i) Electronic or mechanical disturbance caused due to sudden dynamics or intrusion of foreign objects.

(ii) Physical features like fishplated joints or extra holes being interpreted as flaw.

12.5   Routes tested by SPURT car

12.5.1 SPURT car conducts tests twice a year on the routes given below:

(i)

New Delhi

-

Howrah

(ii)

New Delhi

-

Mumbai Central

(iii)

Mathura Jn

-

Chennai

12.5.3 LWR/CWR track only on the above routes are tested by SPURT car.  Fishplated/SWR track is not tested by SPURT car and will require testing by Railways.

12.6 The stretches left untested by SPURT car should be tested by manual USFD testing using Need based criteria

CHAPTER 13

REPORTING AND ANALYSIS OF RAIL/WELD FAILURES

13.1 After each fracture FAILURE REPORT shall be prepared as per proforma given in Annexure –III and Annexure- IV by SE/JE(P. Way)  and Divisions respectively.

13.1.1 All the fractured rail/weld pieces of 150mm length on each side of fractured face, except those attributable to known extraneous causes such as fractures resulting from accidents, series of fractures resulting from passage of flat wheels, etc., shall be sent to Chemist and Metallurgist for detailed investigation in the following cases:

a) Rail failure within 5 years of primary renewal/Spate of premature rail failures.

b) Weld failure within one year of execution.

c) Repetitive rail fractures of same rolling mark.

13.1.2 The Chemist & Metallurgist should submit consolidated investigation report to Headquarters and Director/M&C/RDSO for making out a management information report based on investigation carried out on the above rail failures.  The annual briefs made out by RDSO on the analysis of rail fracture must cover these details. Director (M&C) may call for specific samples from Chemist & Metallurgist for confirmation of their findings.

13.1.3 In the following instances, the samples of rail/weld shall be forwarded to Director/M&C/RDSO.

(a) Rail/ weld samples involved in accident/derailment (b) Rail samples of imported origin failed in service within guarantee period.

13.2 All the failure reports and defects detected are required to be compiled  in  the  form of Annexures -VI  & VII at divisional level.   The data including causes, nature and frequency of defects should be analysed to take managerial decisions for required preventive/ corrective action.

****