Examination of Rails

Rails should be inspected for flaws specially, when the rails show signs of fatigue and the rail wear is excessive. The detection of rail flaws is done either by visual examination of the rail or by ultrasonic rail flaw detection.

1.Visual examination of Rails –

Most of the rail flaws develop at the rail ends. Rail ends should be examined for cracks during the lubrication of rail joints by cleaning the surface of the rail by wire brushes and using a magnifying glass. A small mirror is of assistance in examining the underside of rails. Such an inspection on the important girder bridges and their approaches should be done twice a year.

2.Ultrasonic testing of rails–

Ultrasonic testing of rails is specialized activity and the inspectors carrying out the ultrasonic testing of rails shall be trained by RDSO, in the technique of USFD  testing. Each zonal railway shall create adequate number of excadre posts of inspectors to ensure that entire track length in their jurisdiction is ultrasonically tested at the laid down periodicity. 

Rail testing by ultrasonic method shall be carried out by RDSO approved single rail testing trolley or double testing trolley and rig for 450 probes. Details of frequency and number of each type of probes are as under:

(As per USFD Manual Cs.no 2)

Water is used as couplant while testing with Single Rail Testers/Double Rail Testers.

This is supplied through a water container attached with the trolley. Soft grease to RDSO Specification No. WD-17-MISC. - 92 is to be used as couplant while deploying 45º probes with test rig”.

(As per USFD Manual Cs.no 3)

"Any sweeping signal on horizontal baseline that does not extend beyond 2.5 divisions from the left edge of the screen or vice versa shall be recorded as Gauge Corner Cracking (GCC) and not as OBS"

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 knob 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 and 5 mm dia. hole for conventional criteria in the head portion of the standard rail as shown in Fig. 3 and 4 respectively 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) Gauge face corner 70° (forward & backward).

The equipment shall be able to detect 5 mm dia.FBH hole for need based criteria in the head portion of the standard rail made by use of suitable machine(electron drilling machine) 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.

Classification of Rail Failure:

While testing of rails the rail flaws detected were classified into 2 types:

1. IMR Defects.                                                               2.OBS Defects

Rail Testing Frequency: (As per USFD Manual Cs.no 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), 70ºBackward (B)central probes and, 70º Forward (F) and 70º Backward (B) gauge face corner. 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. 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.

Double Rail tester:

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

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.

Due to frequent misalignment of probes on the fish plated joints and limitations of detection of bolt hole cracks having unfavorable 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.

Action to be taken after Detection of defects:

 Following action shall be taken in respect of defective rails & welds.

Register of Rail failures –

 All the cases of rail failures have to be entered in thesection register by the Permanent Way Inspector as laid down in. For this purpose all

failures whether in running lines, points and crossing rails etc. and irrespective of

type and age of the rails, have to be entered in the section register. This record is

intended to serve as a basic record which should be available in the office of the

Permanent Way Inspectors and will serve to furnish data, if required subsequently for

any statistical analysis or for framing out proposals for track renewal works. Care

should therefore be taken by the Permanent Way Inspectors for filling up all the

details. The Assistant Engineer concerned shall call for the P. W. Is register once

every year and initial the same in token of his perusal.

Reports of Rail failures –

 In addition to the records maintained in the section register, as detailed above, a report has to be prepared as per Annexure 2 / 10 in all cases of rail failures occurring in track with the exception of the cases noted below –

( a ) Rail failures occurring in non running lines.

( b ) Non standard and obsolete rails.

( c ) Rail removed due to casual renewals on account of accidental damages to the rails such as wheel burns and scabbings, buckling, kinks, derailments, abnormal slipping of loco wheels, excessive wear, loss of section by corrosion, battering, elongation of holes etc.

( d ) Machined rails such as mitred joints, switch expansion joints, switches and

crossings.

For this purpose, the Permanent Way Inspector will prepare a ‘Rail Failure’ Report in quadruplicate as per proforma at Annexure 2 / 10 and shall forward 3 copies to the Assistant engineer, who will transmit all the copies with his remarks to Divisional Engineer, for onward transmission of one copy each to the Chief Engineer and Executive Director ( M & C ) / RDSO / Lucknow. In case of failures requiring metallurgical investigation, the report should be prepared in quintuplicate, the extra copy being sent to the Chemist and metallurgist of the Zonal Railway along with the samples as detailed in the sub – para ( 7 ) below. Efforts should be made y Divisional Engineer so that the report reaches the Executive Director ( M & C ) / RDSO within a fortnight of the rail failure. Sketches illustrating the fractures will be prepared and submitted with the failure reports on each case, care being taken that the running face of the rail indicated thereon. It is particularly essential to record the type of failure in the failure reports against item No. 5.3 as per R.D.S.O. monograph ‘’Rail Failures – Description, Classification and Reporting’’. 

The Executive Director ( M & C ) will arrange to carry out analysis of rail failures from the reports received from the Permanent Way Inspectors and the Chemist and Metallurgist and publish reports with suggestions for reducing failures. In most cases, it is possible to determine the cause of the failure by visual examination / ultrasonic detection without the need for metallurgical investigation. However, in cases mentioned in sub – para ( 5 ) below, it is obligatory to take up full metallurgical examination by the Chemist and Metallurgist of the Railway concerned with a view to ascertaining the exact cause of failure. In such cases the rail failure report should be made out in the prescribed proforma inserting the most probable code of failure against item No. 5.3 and indicating whether the sample has been sent to the Chemist and Metallurgist for metallurgical investigation. 

For the cases of rail failures detected visually a short piece of rail approximately 1 meter long ( 500 mm + 500 mm ) has to be sent to the Zonal Railway’s Chemist and Metallurgist by the Permanent Way Inspector direct, along with a copy of the rail failure report, only for such cases which come under the category listed in sub para ( 5 ) below. In other cases, i.e. those detected by ultrasonic flow detectors, the rail pieces of 1 meter long ( 500 mm + 500 mm ) containing the flaw shall be sent for metallurgical test only from those rails which are removed from track based on the criteria for removal of rails and falling in the category listed in sub – para ( 5 )below. The test pieces for metallurgical examination are to be sent only for rail failures which occur within test free period subject to maximum of 10 years of rolling and for which detailed reports are to be prepared. In case of repetitive failures of rails of same rolling mark, irrespective of the type of fracture / flaw, short rail piece of approximately 1 meter ( 500 + 500 mm ) containing the fracture / flaw detected visually or by ultrasonic flaw detector should be sent to the Chemist and Metallurgist together with a rail failure report for Metallurgical investigation. Chief Track Engineer of Zonal railway shall forward the case of repetitive failure of rails of same rolling mark on account of Chemical & Metallurgical reasons to Executive Director / M & C / RDSO along with investigation reports from Chemist and Metallurgist. The rail pieces of approximately 1 meter ( 500 + 500 mm ) containing the fracture should be sent to Executive Director / M & C / RDSO together with a rail failure report for Metallurgical investigation where rail / weld failure is prima facia cause of train accident. To sum up, before sending the test pieces to the Chemist and Metallurgist or RDSO, it should be ensured that –

( I ) The rail failure is within test free period subject to maximum of 10 years of rolling of rail, irrespective of the type of fracture / flaw.

( ii ) The rail have been removed from track as a result of visual or ultrasonic detection and rail failure falls in categories listed in sub para ( 5 ) below.

( iii ) The rail where rail / weld failure is prima facie cause of train accident should be sent to RDSO.

( iv ) The rails with repetitive failure of same rolling mark irrespective of type of

failure.

In cases of failures of imported rails occurring within guarantee period, stipulation of sub para ( 6 ) shall be followed.

Para 257 ( 6 ) – Failure of imported rails within the Guarantee period – In all cases of failure of imported rail occurring within the guarantee period, irrespective of the type of fracture / flaw rail piece approximately 1 meter ( 500 + 500 mm ) containing the fracture / flaw detected visually or by ultrasonic flaw detector should be sent to the Chemist and Metallurgist together with a rail failure report for metallurgical investigation. 

Para 257 ( 7 ) – Procedure for sending samples for metallurgical investigation – In case of fractured rail, both the pieces of approximately 500 mm long each i.e. total 1 meter long containing fractured faces / flaw should be sent to the Chemist and Metallurgist for investigation. To avoid damage in transit, the fractured faces shall be protected with mineral jelly and suitably covered with hessian cloth. Cracked rails may also be suitably protected at the crack location to avoid damage in transit. Pieces having internal defects may be dispatched as such. The Chemist and Metallurgist of the Railway will carry out metallurgical investigation, as required, and forward one copy of the report each to the Chief Engineer of the Railway and the Executive Director ( M & C ) / RDSO. In case of failures of imported rails within the guarantee period, attributable to manufacturing defects as revealed by metallurgical investigation, the Chief Engineer should immediately lodge a provisional claim with the manufacturer pending Executive Director ( M & C )’s confirmation of the findings submitted by the Chemist and Metallurgist of the Railway.

The Executive Director ( M & C ) / RDSO will scrutinize the report submitted by the Chemist and Metallurgist and if he agrees with the findings as submitted inform the Chief Engineer accordingly. Where the Executive Director ( M & C ) / RDSO feels the need for carrying out further investigation before giving his verdict, he will call For the sample from the Chemist and Metallurgist of the railway and carry out confirmatory tests, as necessary and intimate the findings to the Chief Engineer. On The basis of Executive Director ( M & C )’s advice the Chief Engineer will then finalise the claim with the manufacturer.

In case of failures of rails other than imported, the Executive Director ( M & C )

RDSO will call for samples from the Chemist and Metallurgist for confirmatory tests, where necessary. Based on the trend indicated by the numerical analysis of the rail failures for the period under review the Executive Director ( M & C ) will bring to the notice of the indigenous manufacturers and Inspecting Agency, any

predominance of failure attributable to manufacturing defects, to enable corrective action being taken. (as per cs no.122 dated /11/10)