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International
Standard
ISO 5735-1
First edition
Railway infrastructure — Non-
2024-03
destructive testing on rails in track —
Part 1:
Requirements for ultrasonic testing
and evaluation principles
Infrastructure ferroviaire — Essais non destructifs sur les rails
de voie —
Partie 1: Exigences pour les principes d'évaluation et d'inspection
par ultrasons
Reference number
© ISO 2024
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General . 3
5 Principle of ultrasonic testing in track . 3
6 Ultrasonic testing speed and detection of discontinuities . 3
7 Simulation of internal reflectors in reference rails . 4
Annex A (normative) Reflectors for reference rails in Europe . 5
Annex B (normative) Reflectors for reference rails in China .29
Annex C (normative) Reflectors for reference rails in Japan .39
Annex D (informative) Ultrasonic test areas in rails tested with test vehicles or manually
propelled devices .49
Bibliography .55
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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This document was prepared by Technical Committee ISO/TC 269, Railway applications, Subcommittee SC 1,
Infrastructure.
A list of all parts in the ISO 5735 series can be found on the ISO website.
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iv
Introduction
This document represents the actual state of the art of continuous ultrasonic testing of rails in track applied
by railway companies.
Timely detection of discontinuities (irregularities) in the rails installed in track is very important to ensure
the strength and stability of the rails in track. Discontinuities pose a threat to the strength and integrity of
the rails and should be identified in order to ensure safer transportation.
Welded joints are included but do not get a specific focus.
v
International Standard ISO 5735-1:2024(en)
Railway infrastructure — Non-destructive testing on rails
in track —
Part 1:
Requirements for ultrasonic testing and evaluation principles
1 Scope
This document specifies the requirements for testing principles and systems to produce comparable results
with regard to location, type and size of discontinuities in rails. This document does not aim to give any
guidelines for managing the result of ultrasonic rail testing. This document only applies to flat bottom
(Vignole) railway rail profile 43 kg/m and above.
This document only applies to continuous testing of rails installed in track for detecting internal
discontinuities.
This document only applies to testing equipment fitted to dedicated test vehicles or manually propelled
devices. This document treats welded joints as plain rail.
This document does not define the requirements for vehicle acceptance. This document does not apply to
ultrasonic testing of rails in a production plant.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 5577:2017, Non-destructive testing — Ultrasonic testing — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5577 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
structure of the rail
components that constitute the rail as shown in Figure 1
Key
1 field side
2 gauge side
3 rail head
4 rail web
5 rail foot
running surface
gauge corner area
rail head side area
rail head fillet radius area
rail web area
rail foot fillet radius area
rail foot area
Figure 1 — Structure of the rail
3.2
reference reflector
artificial feature designed to represent a discontinuity of a known size, orientation and position for
continuous testing of an ultrasonic system
3.3
indication
signal shown on the display of an ultrasonic instrument or system as a result of received ultrasonic pulse
[SOURCE: ISO 5577:2017, 6.5.14, modified — "which can be separated from noise, surface and back-wall
echoes" has been replaced with "or system as a result of received ultrasonic pulse" in the definition.]
4 General
In order to verify the performance of the continuous ultrasonic systems for rail testing, there shall be
defined reference reflectors in a test track. These reference reflectors shall be recorded and reported at the
normal operational speed of the test vehicle/system.
The reference rails in the test track shall be constructed from new rail to provide the correct head profile
and running surface condition. Rails with corrosion on the running surface shall be cleaned to allow the
transmission of sound prior to any testing, for example using a powered steel wire brush.
Evidence of an indication is obtained by non-destructive testing.
In this document, a test system uses sound at a frequency range of 2 MHz to 5 MHz.
A flat-bottomed hole (FBH) shall be machined using a twist drill at the appropriate diameter followed by
a slot drill hole of the same diameter to the required depth to generate the flat end of the hole. Accuracy in
diameter and depth shall be within 0,1 mm. Accuracy in angle shall be within 0,1°.
A side-drilled hole (SDH) shall be machined using a twist drill at the appropriate diameter. Accuracy in
diameter shall be within 0,1 mm. Accuracy in angle shall be within 0,1°.
An electrical discharge machined (EDM) notch shall be machined to the desired shape and orientation with
an accuracy of 0,1 mm. Accuracy in angle shall be within 0,1°. As an alternative for the manufacturing of
reflectors in longer sections of rail, water jet cutting can be used instead of EDM.
Due to wear of the rail, dimension can vary. If the rail is used for distance and sensitivity setting of ultrasonic
testing (UT) inspection devices, this needs to be taken into account.
A verification of the ultrasonic testing inspection devices shall be carried out to the specification and
intervals required by the infrastructure manager.
5 Principle of ultrasonic testing in track
Ultrasonic waves transmitted into the structure of the rail, see Figure 1, are reflected from the surfaces of
the rail body. Fractures and other discontinuities within the rail, as well as the boundary of the rail act as
reflecting surfaces. By receiving, recording and interpreting the returned ultrasonic signals, it is possible
to detect discontinuities within a rail installed in track before they present an unacceptable risk to the
integrity and strength of the rail. Annex D gives examples of test areas in rails tested with test vehicles or
manually propelled devices.
6 Ultrasonic testing speed and detection of discontinuities
Ultrasonic beams have a width which is determined by the size of the transducer and the frequency. All
reflectors interact with the ultrasonic beam. The beam sweeps across the reflector when either the vehicle
or the manually propelled device, or both, travels along the track. The sound wave is being reflected and
detected by the transducer. All ultrasonic systems use a gate threshold level and the system records a
response when the reflection is above the gate threshold level. By controlling the gain in the ultrasonic
system and the gate threshold level the number of responses for a given size of reflector can be defined.
When evaluating an A-scan, a signal to noise ratio of at least 3 is required.
The B-scan display of a reflector should not contain unwanted representation of spurious and multiple echoes.
A reflector can be sized by setting the system parameters so that a known number of responses are received
from a known sized reference reflector. The relationship of the number of responses and the size of the
reference reflector is known. This applies to all the reflectors given in Annex A, Annex B and Annex C.
The maximum testing speed depends upon the rail profile (longitudinal and transverse), reflector size to be
detected, the beam width, sampling frequency and the number of responses required for an indication to be
recorded.
The non-direct tested zone depends on the sensitivity of used ultrasonic system and testing speed.
7 Simulation of internal reflectors in reference rails
Reference rails incorporating sets of reference reflectors selected from the given tables of reflectors shall
be created. They shall be installed in the left and right rails of a section of track if test vehicles are used. If
only trolleys or manually propelled devices are used, the reference rails may be installed out-of-track. The
length of the reference
...