CEN/TC 256

Date: 2025-09

prEN 16729‑1:2026

Secretariat: DIN

Railway applications — Infrastructure — Non-destructive testing on rails in track —Part 1: Requirements for ultrasonic inspection and evaluation principles

Bahnanwendungen — Infrastruktur — Zerstörungsfreie Prüfung an Schienen im Gleis — Teil 1: Anforderungen an Ultraschall-Inspektionen und Bewertungsgrundlagen

Applications ferroviaires — Infrastructure ─ Test non-destructiv sur des rails en voie — Partie 1: Exigences pour l'inspection par ultrasons et les principes d'évaluation

CCMC will prepare and attach the official title page.

Contents Page

European foreword 3

Introduction 4

1 Scope 5

2 Normative references 5

3 Terms and definitions 5

4 Basics 7

4.1 General 7

4.2 Principle of ultrasonic testing in track 7

4.3 Ultrasonic testing speed and detection of discontinuities 7

4.4 Simulation of internal reflectors in reference rails 7

5 Detection of artificial reflectors 11

6 Control of positioning accuracy 16

Annex A (normative) Artificial reflectors in reference rails 17

Annex B (informative) Ultrasonic test areas in rails tested with test vehicles or manually-propelled devices 36

Bibliography 40

European foreword

This document (prEN 16729‑1:2026) has been prepared by Technical Committee CEN/TC 256 “Railway applications”, the secretariat of which is held by DIN.

This document is currently submitted to the CEN Enquiry.

This document will supersede EN 16729‑1:2016.

prEN 16729‑1:2026 includes the following significant technical changes with respect to EN 16729‑1:2016:

a) Normative references have been updated;

b) Terms and definitions have been revised;

c) General requirements, requirements on testing in track, testing speed and simulation of internal reflectors have been revised;

d) Requirements on detection of artificial reflectors have been revised;

e) Requirements on detection of artificial reflectors have been revised;

f) Requirements on control of positioning accuracy have been revised;

g) Normative Annex A has been revised;

h) Informative Annex B has been revised;

i) Annex ZA has been removed;

j) Bibliography has been updated.

A list of all parts in the EN 16729 series consists of:

— EN 16729‑1, Railway applications — Infrastructure — Non-destructive testing on rails in track — Part 1: Requirements for ultrasonic inspection and evaluation principles;

— EN 16729‑2, Railway applications — Infrastructure — Non-destructive testing on rails in track — Part 2: Eddy current testing of rails in track;

— EN 16729‑3, Railway applications — Infrastructure — Non-destructive testing on rails in track — Part 3: Requirements for identifying internal and surface rail defects;

— EN 16729‑4, Railway applications — Infrastructure — Non-destructive testing on rails in track — Part 4: Qualification of personnel for non-destructive testing on rails;.

— EN 16729‑5, Railway applications — Infrastructure — Non-destructive testing on rails in track — Part 5: Non-destructive testing on welds in track;

— CEN/TR 16729‑6, Railway applications — Infrastructure — Non-destructive testing on rails in track — Part 6: Non-destructive testing of manganese cast steel components in switches and crossings.

Introduction

This document represents the actual state of the art of automated ultrasonic testing of rails in track applied by European railway companies.

This document applies to testing of rails installed in track for detecting internal discontinuities.

This part applies to testing equipment fitted to dedicated test vehicles or manually-propelled devices. This document does not define the requirements for vehicle acceptance. This part of the series does not apply to ultrasonic testing of rails in a production plant.

The document specifies the requirements for testing principles and systems in order to produce comparable results with regard to location, type and size of discontinuities in rails. This document is not aiming to give any guidelines for managing the result of ultrasonic rail testing.

This document applies only to rail profiles meeting the requirements of EN 13674‑1.

The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 5577:2025, Non-destructive testing – Ultrasonic testing – Vocabulary

EN 13674‑1, Railway applications - Track - Rail - Part 1: Vignole railway rails 46 kg/m and above

For the purposes of this document, the following terms and definitions given in ISO 5577:2025 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

parts of the rail

components that constitute the rail itself as shown in Figure 1

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Figure 1 — Parts of the rail

3.2

artificial reflector

artificial feature designed to represent a discontinuity of a known size, orientation and position to test an ultrasonic system

In order to verify the performance of the automated ultrasonic systems for rail testing there shall be defined artificial reflectors in a test track. These artificial reflectors shall be recorded and reported at the normal operational speed of the test vehicle/system.

The reference rail 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 ultrasound prior to any testing, for example using a powered steel wire brush.

A signal shown on the display of an ultrasonic instrument or system as a result of received ultrasonic pulse is called an indication. Evidence obtained by non-destructive testing.

In test systems according to this document ultrasound at a frequency range of 2 MHz to 5 MHz is used.

A flat-bottom 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.

The accuracy of the diameter and the vertical depth shall be within 0,1 mm and 1,0 mm respectively. The accuracy of the angle shall be within 1,0°.

Due to wear of the rail, dimension might vary. If the rail is used for distance and sensitivity setting of Ultrasonic Testing (UT) inspection devices this needs to be taken into account.

Ultrasonic waves transmitted into the rail will be reflected from the surfaces of the rail body. Fractures and other discontinuities within the rail, as well as the boundary of the rail will 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 B gives examples of test areas in rails tested with test vehicles or manually propelled devices.

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 the vehicle and / or manually-propelled device travels along the track. Ultrasound will be reflected and detected by the transducer. All ultrasonic systems use a threshold level in a gate and the system will record a response when the reflection is above the 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.

A reflector can be sized by setting the system parameters so that a known number of responses are received from a known sized artificial reflector. The relationship of the number of responses and the size of the artificial reflector is known. This applies to all the reflectors in Annex A.

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.

In semi- and full automatic systems, the inspection results shall be documented so that the evaluation can be reviewed.

Reference rails incorporating sets of artificial reflectors selected from Annex A 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 rails is not defined by this document. When in track carrying traffic, the distance between the artificial reflectors should be assessed by the Infrastructure Manager with consideration to the structural integrity of the rail. Artificial reflectors shall be orientated to check probes scanning in both directions.

To prevent the influence of water and dirt on the ultrasonic responses, reference holes and notches shall be plugged with a synthetic compound.

Where the reference rails carry traffic, the Infrastructure Manager shall carry out a risk assessment to determine if reinforcement of the artificial reflectors is necessary (fishplates or similar) and determine the maintenance regime of the reference rails.

Table 1 — Artificial reflectors in reference rails (normative references)

To assess the detection capability of an ultrasonic rail inspection system, artificial reflectors are used. The design of the artificial reflectors is defined by the figures in Annex A and the dimensions given in Table 1.

This document presents two sets of artificial reflectors:

Which artificial reflector belongs to Set A or Set B is indicated in Table 1 and Table 2.

The IM shall decide, if Set A or Sets A and B are used for the system assessment. An assessment based only on the artificial reflectors of Set B does not comply with this document.

The ultrasonic probe angles listed in Table 2 are used in most ultrasonic test vehicles or manually propelled devices. The IM shall identify and list the probes and corresponding probe angles of the UT system to be assessed. By comparing the list of probes with the detection requirements in Table 2 the IM shall define which probe of the system is required to detect a given artificial reflector.

All angled transducers shall be configured to scan in both directions (forward and backward). Artificial reflectors shall be orientated to check probe scanning in both directions.

When evaluating an indication from a reflector, a signal-to-noise ratio of at least 3:1 is required.

A loss of backwall echo shall be indicated when passing a bolt hole.

The B-scan display of a reflector should not contain noise striations.

Table 2 — Reference reflectors (Table 1) to be detected with defined probe angles

The positioning system shall be tested to assure that reflectors, defects and track features are detected with an accuracy of ± 0,2 %. This requirement shall be tested in a track section between 200 m and 500 m, with a minimum of four consecutive runs.

Different configurations of test direction and speeds, including maximum speed of the tested system, shall be used.

1. 
   (normative)
   
   Artificial reflectors in reference rails

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Figure A.1 — Volumetric reflector in rail head

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Figure A.2 — Central transverse reflector (20°) in rail head

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Figure A.3 — Gauge or field transverse reflector (20°) in rail head

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Figure A.4 — Full width transverse reflector (20°) in rail head

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Figure A.5 — Full width transverse reflector (35°) in rail head

Dimensions in millimetres

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Figure A.6 — Full width transverse reflector (53°) in rail head

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Figure A.7 — Volumetric reflector gauge side of rail head

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Figure A.8 — Volumetric reflector field side of rail head

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Figure A.9 — Horizontal reflector in rail head

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Figure A.10 — Horizontal bolt hole slot

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Figure A.11 — Bolt hole slot position A

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Figure A.12 — Bolt hole slot position B

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Figure A.13 — Bolt hole slot position C

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Figure A.14 — Bolt hole slot position D

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Figure A.15 — Volumetric reflector at head – web radius

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Figure A.16 — Volumetric reflector mid – web

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Figure A.17 — Volumetric reflector at foot – web radius

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Figure A.18 — Head – web radius transverse reflector (35°)

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Figure A.19 — Foot – web radius transverse reflector (53°)

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Note This figure is kept for historical purposes, this reflector is no longer in use.

Figure A.20 — Vertical longitudinal reflector

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Figure A.21 — Vertical longitudinal reflector

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Figure A.22 — Change in rail foot depth

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Figure A.23 — Rail foot notch 5 mm

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Figure A.24 — Rail foot notch 10 mm

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Figure A.25 — Multiple repeated reflector

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Figure A.26 — Resolution check reflector

1. 
   (informative)
   
   Ultrasonic test areas in rails tested with test vehicles or manually-propelled devices

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Figure B.1 — Ultrasonic test area for a 0° probe

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Figure B.2 — Ultrasonic test area for a centred 65°-70° probe

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Figure B.3 — Ultrasonic test area for a 35°-45° probe

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Figure B.4 — Ultrasonic test area for a centred transverse 45° to 55° probe

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Figure B.5 — Ultrasonic test area for transverse 30° probe

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Figure B.6 — Ultrasonic test area for a 65° to 70° probe parallel with the gauge side or field side

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Figure B.7 — Ultrasonic test area for a centred 65° to 70° probe squinting in the direction of gauge side or field side

Bibliography

[1] EN 16729‑3:2018, Railway applications - Infrastructure - Non-destructive testing on rails in track - Part 3: Requirements for identifying internal and surface rail defects