ULTRASONIC TESTING OF RAILS AT MANUFACTURERS’ WORKS

  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 0deg (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:

10     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 20deg 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.