SIST EN 16729-5:2023

SLOVENSKI STANDARD
oSIST prEN 16729-5:2021
01-oktober-2021
Železniške naprave - Infrastruktura - Neporušitveno preskušanje na progi - 5. del:
Neporušitveno preskušanje zvarnih spojev na progi
Railway applications - Infrastructure - Non-destructive testing on rails in track - Part 5:
Non-destructive testing on welds in track
Bahnanwendungen - Oberbau - Zerstörungsfreie Prüfung an Schienen im Gleis - Teil 5:
Zerstörungsfreie Prüfung an Schweißungen im Gleis
Ta slovenski standard je istoveten z: prEN 16729-5
ICS:
19.100 Neporušitveno preskušanje Non-destructive testing
25.160.40 Varjeni spoji in vari Welded joints and welds
93.100 Gradnja železnic Construction of railways
oSIST prEN 16729-5:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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DRAFT
EUROPEAN STANDARD
prEN 16729-5
NORME EUROPÉENNE

EUROPÄISCHE NORM

August 2021
ICS 25.160.40; 93.100
English Version

Railway applications - Infrastructure - Non-destructive
testing on rails in track - Part 5: Non-destructive testing on
welds in track
 Bahnanwendungen - Oberbau - Zerstörungsfreie
Prüfung an Schienen im Gleis - Teil 5: Zerstörungsfreie
Prüfung an Schweißungen im Gleis
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 256.

If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.


EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 16729-5:2021 E
worldwide for CEN national Members.

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Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Symbols and abbreviations . 6
5 NDT methods to detect defects in rail welds . 6
5.1 General . 6
5.2 Visual testing – VT. 8
5.2.1 General . 8
5.2.2 VT inspection zone . 8
5.2.3 Example of defects . 8
5.3 Ultrasonic Testing — UT . 8
5.3.1 General . 8
5.3.2 UT inspection zone . 8
5.3.3 Example of defects . 8
6 Description of weld defects . 9
6.1 Defects in electric arc repair welds . 9
6.1.1 Volumetric defects - Porosity . 9
6.1.2 Planar defects . 10
6.2 Defects in flash butt welds (Tri-metallic welds) . 13
6.2.1 Volumetric defects - Lack of fusion. 13
6.3 Defects in aluminothermic weld . 16
6.3.1 Volumetric defects . 16
6.3.2 Planar defects . 22
6.3.3 Thermal contraction (Hot Tear) . 27
6.3.4 Fatigue cracks . 28
7 Documentation . 29
7.1 General . 29
7.2 Requirements of documentation VT . 29
7.3 Requirements of documentation UT . 30
Annex A (informative) Operating visual testing procedure on welds . 31
Annex B (informative) Ultrasonic testing procedures on welds . 32
Bibliography. 56
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European foreword
This document (prEN 16729-5:2021) 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.

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Introduction
The procedures are intended for new welds but are applicable to all welds on demand of the responsible
IM. If welds are to be tested, they should be tested by the procedures defined in this document.

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1 Scope
This document specifies the procedures of visual testing and ultrasonic testing of rail welds in track for
rail profiles meeting the requirements of EN 13674-1.
This document specifies the principles for testing procedures for manufactured welds. This document
defines the procedure for joint welds and repair welds. This document does not define the number of
welds to be tested.
This document is not concerned with the approval of the welding procedure.
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.
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological 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
collar
excess of weld material outside the rail profile
3.2
registration level
ultrasonic signal amplitude where indications shall be recorded, not to be confused with acceptance
criteria
3.3
tandem rig
rig that ensures a correct distance between two ultrasonic probes
3.4
testing zone
location where probes or devices are placed/moved on the rail surface
3.5
inspection zone
area or volume which is checked for indications
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4 Symbols and abbreviations
For the purposes of this document, the abbreviations in Table 1 apply.
Table 1 — Abbreviations
Abbreviation Abbreviated term
DAC Distance Amplitude Curve
FBH Flat Bottom Hole, see EN 16729-1
FSH Full Screen Height
H Phase H for testing with hand-held single probes
T Phase T for testing with tandem 45° on the running surface
TS Phase TS for testing with tandem 70° on the side of the rail head, web and foot
UT Ultrasonic testing
VT Visual testing
W Phase W for testing with a walking stick
IG Inspection gain
G
Gain distance amplitude curve
DAC
ΔG Transfer gain compensation
G
Gain needed for 80 % FSH in the weld
weld
G
Gain needed for 80 % FSH in the plain rail
plain_rail

5 NDT methods to detect defects in rail welds
5.1 General
This part of this European Standard specifies non-destructive testing methods for the detection of
internal and surface defects in rail welds and the suitability of the test methods for the detection and
assessment of weld defects in rails in track. The description of the defects can be found in Table 3 to
Table 17, including the respective Figure 1 to Figure 19. The procedures for detecting indications in rail
welds are presented in the Annex A and Annex B. The procedures according to defect and inspection
number are presented in Table 2.
The requirements to inspect welds are determined by the IM. If the inspection of a selection or all the
welds is required by the IM, the IM should define which procedure and which inspection number shall be
performed.
The informative annexes do not give acceptance criteria. The acceptance criteria can be defined on the
basis of the reference blocks and the level of sensitivity, including the numbers of indications which
exceed the testing level and the minimum recording level. These parameters should be defined in the
inspection instruction approved by the IM.
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Table 2 — Testing procedures of the weld defects according to the inspection number in Annex A and Annex B
Procedures in Annex VT UT
a
 W.1 W.2 W.3 H.1 H.2 H.3 H.4 T.1 TS.1 TS.2 TS.3
Inspection phase
Volumetric defects Porosity X X X X X X X  X X
Surface cracking X X X X X X X  X X
Electric arc repair
welds
Planar defects Transverse cracking X X X X X X X  X X
Lack of fusion X X X X X X X  X X
Flash butt welds Volumetric defects Lack of fusion   X X  X X X X   X
Porosities  X X X X X X X X X X X
Inclusions  X X X X X X X X X X X
Volumetric defects
Shrinkage           X
Lack of fusion  X X X X X X X X X X X
Sand burn X X X X X X X  X X
Surface defects in the weld
X          X
Alumino-thermic
collar
welds
Thermal contraction (hot
X X X X X X X X X  X X
tear)
Planar defects
Fatigue cracks X X X X X X X X X X X X
Transversal tearing of the
X X X X X X X  X
surface weld material
Weld collar damage at vent
X       X   X X
riser
a
Overview of inspection numbers in Annex B, Table B.1.
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5.2 Visual testing – VT
5.2.1 General
Visual testing of welds in rails is an examination of the surface, to detect the presence of a defect and to
define and measure it.
5.2.2 VT inspection zone
Visual testing can inspect all surface areas of welds.
5.2.3 Example of defects
Examples of defects identified by visual testing are:
— broken welds;
— gas holes;
— porosity;
— surface breaking cracks;
— sand inclusions;
— geometrical errors.
5.3 Ultrasonic Testing — UT
5.3.1 General
Ultrasonic testing of welds in rails is an examination of the internal volume, to detect the presence of a
defect and to define and measure it.
5.3.2 UT inspection zone
Ultrasonic testing can inspect the internal volume of the weld, fusion zone and heat affected zone. The
inspection zone depends on welding type and expected indications.
5.3.3 Example of defects
Examples of defects identified by ultrasonic testing are:
— lack of fusion;
— cracks;
— inclusions;
— porosity;
— hot tear.
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6 Description of weld defects
6.1 Defects in electric arc repair welds
6.1.1 Volumetric defects - Porosity
Table 3 — Porosity
Weld type: Electric arc repair welds
Defect type: Porosity
Appearance, causes and location:
— Porosity in electric arc repair welds is characterized by small inclusions on the welding material.
— It is presented on the surface or inside the welding material itself, more common on the
longitudinal limits of the repair weld.
— It can derive from poor execution on the part of the welder, unfavourable environmental conditions
and the quality/suitability of the electrodes used.
— It can develop cracks under impact loads.


Figure 1 — Porosity on electric arc repair welds (a)
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Figure 2 — Porosity on electric arc repair welds (b)

6.1.2 Planar defects
6.1.2.1 Surface cracking
Table 4 — Surface cracking
Weld type: Electric arc repair welds
Defect type: Surface cracking
Appearance, causes and location:
— Surface cracking on electric arc repair welds is characterized by superficial cracks on the welding
surface material.
— It originates either isolated or associated with superficial porosities.
— It is presented on the surface of the repair weld, more common on the longitudinal limits of the
repair weld.
— It can derive from poor execution on the part of the welder, unfavourable environmental conditions
and the quality/suitability of the electrodes used.
— It has accelerated propagation due to impact loads, especially at joints in poor conditions.
— It may progress into spalling and at a later stage pieces of welding material may break away.

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Figure 3 — Surface cracking

6.1.2.2 Transverse cracking
Table 5 — Transverse cracking
Weld type: Electric arc repair welds
Defect type: Transverse cracking
Appearance, causes and location:
— Transverse cracking on electric arc repair welds has its point of origin in the head of the rail in or
under the repair weld.
— It can derive from either not sufficient removal of rail material to eliminate pre-existing cracks in
the rail head or by slag intrusion at the fusion face of the weld.
— It may occur due to residual stresses caused by incorrect welding procedure such as incorrect pre-
heat or wrong consumables.
— It can rapidly develop in size and severity, mainly associated with the heating produced during the
weld repair procedure.

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Figure 4 — Transverse cracking

6.1.2.3 Lack of fusion
Table 6 — Lack of fusion
Weld type: Electric arc repair welds
Defect type: Lack of fusion
Appearance, causes and location:
— Lack of fusion between the welding and the rail material is characterized by poor contact between
the two materials.
— It can develop in to a breakaway of a significant piece of welding material, down to the rail material
under the repair weld.
— It derives mainly from insufficient preheating of the rail under repair, but it can also be associated
with poor execution on the part of the welder, unfavourable environmental conditions and the
quality/suitability of the electrodes used.
— It has accelerated propagation due to impact loads, especially at joints in poor conditions.
— It shall not to be confused with a severe stage of spalling on the weld material.

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Figure 5 — Lack of fusion

6.2 Defects in flash butt welds (Tri-metallic welds)
6.2.1 Volumetric defects - Lack of fusion
Table 7 — Lack of fusion
Weld type: Flash butt welds
Defect type: Lack of fusion
Appearance, causes and location:
— Lack of fusion on tri-metallic weld is characterized by a transverse crack between the stainless-
steel insert and the pearlitic rail or within the stainless-steel insert running into the manganese
crossing.
— It is presented on the surface generally at the fusion face at the lower half of the weld and may be
visible only from the underside of the foot.
— It can derive from inclusions within the cast stainless steel insert, insufficient weld process control
or heavy grinding of the weld.
— It can have accelerated propagation under impact loads, especially large cracks on the pearlitic side
due to small stress raisers. Defects within the stainless insert and manganese generally propagate
slower, but this is dependent on local conditions.

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Figure 6 — Transverse tri-metallic zone weld defect (a)
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Figure 7 — Transverse tri-metallic zone weld defect (b)

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6.3 Defects in aluminothermic weld
6.3.1 Volumetric defects
6.3.1.1 Porosity
Table 8 — Porosity
Weld type: Aluminothermic weld
Defect type: Porosity
Appearance, causes and location:
— Porosity in aluminothermic weld is an accumulation of gas bubbles with a smooth and clean
surface. Porosity can appear either in the surface of the weld or within the welding material.
— It is caused by humidity, insufficient preheating or damp mould, crucible and consumables.
— It weakens the weld but is unlikely to propagate due to fatigue. Breaks can occur due to load
conditions or poor track geometry.


Figure 8 — Porosity on aluminothermic welds

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6.3.1.2 Inclusions
Table 9 — Non-metallic volumetric inclusions
Weld type: Aluminothermic weld
Defect type: Non-metallic volumetric inclusions (Slag or sand)
Appearance, causes and location:
— Non-metallic volumetric inclusions in aluminothermic weld are foreign materials within the weld.
Inclusions usually have a rough surface and irregular shapes. Inclusions due to slag appear as black
and are more likely to occur at the upper parts of the rail web and head; inclusions due to sand
appear as white and can occur anywhere in the weld.
— Slag inclusions may be caused by
— inadequate cleaning of long-life crucible for multiple use,
— inadequate slag removal after flame cutting of the rail ends,
— missing mould plug and
— early pouring of the aluminothermic portion due to automatic thimble malfunction.
— Sand inclusions may be caused by
— inadequate covering of rail gap during sealing, causing luting sand to fall into the rail gap,
— luting sand pressed into the rail gap, when sealing moulds covering rail ends with a height
difference and
— piece of mould broken off when mounting the moulds or due to too hard pre-heating.
— It weakens the weld but is unlikely to propagate due to fatigue. Breaks can occur due to load
conditions or poor track geometry.

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Figure 9 — Non-metallic volumetric inclusion (a)
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Figure 10 — Non-metallic volumetric inclusion (b)

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6.3.1.3 Shrinkage
Table 10 — Shrinkage
Weld type: Aluminothermic weld
Defect type: Shrinkage
Appearance, causes and location:
— Shrinkage in aluminothermic weld is a three-dimensional retraction of metal, appearing as a cavity
located in the rail web. It is positioned in the middle of the collar or in the profile of the rail.
— Its dimension is variable, the length could be of several millimetres (>50 mm) with a width of a
maximum of 10 mm.
— It is caused by excessive preheating or rapid cooling of the weld material in or around the weld
collar.
— It may grow and lead to breaking of the weld, especially when the width of the shrinkage exceeds
5 mm.


Figure 11 — Shrinkage

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6.3.1.4 Lack of fusion
Table 11 — Lack of fusion
Weld type: Aluminothermic weld
Defect type: Lack of fusion
Appearance, causes and location:
— Lack of fusion is a vertical planar failure extending along the former rail end sections. In most cases
the rail foot area is affected.
— It is caused by wrong execution of the pre-heating operation due to incorrect gas pressure, pre-
heating duration, burner alignment and too narrow gap size between the rail ends. In case of
insufficient pre-heating lack of fusion is often combined with porosity.


Figure 12 — Aluminothermic weld with lack of fusion at the rail foot and porosity

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6.3.2 Planar defects
6.3.2.1 Sand burn
Table 12 — Sand burn
Weld type: Aluminothermic weld
Defect type: Sand burn
Appearance, causes and location:
— Sand burn in aluminothermic weld is characterized by lack of metal on the top or the rail head.
— It is caused by the luting sand or mould sand vitrifying due to pouring steel or excessive pre-heating
flame causing indentations in the rail head surface.
— It can grow due to load conditions, in a similar way to a deep-seated squat by developing cracks
growing into the rail head.


Figure 13 —Sand burn

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6.3.2.2 Surface defects on the weld collar
Table 13 — Surface defects on the weld collar
Weld type: Aluminothermic weld
Defect type: Surface defects on the weld collar
Appearance, causes and location:
— Surface defects on the weld collar in aluminothermic weld can be characterized by a smooth surface
with cavities.
— It is caused by excess oxygen during preheating which will result in vitrification of the mould.
— It is unlikely to propagate.

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Figure 14 — Surface defect on the weld collar

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6.3.2.3 Transversal tearing of surface weld material
Table 14 — Transversal tearing of surface weld material
Weld type: Aluminothermic weld
Defect type: Transversal tearing of surface weld material
Appearance, causes and location:
— Transversal tearing of surface weld material in aluminothermic weld appears as a loss of material
in transversal direction on the rail head surface.
— It is caused by
— using the rail trimmer prematurely after solidification,
— using cutting blades in poor condition or
— incorrect working conditions.
— It can grow due to load conditions, in a similar way to a deep-seated squat by developing cracks
growing into the rail head.


Figure 15 — Transversal tearing of surface weld material (a)
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Figure 16 — Transversal tearing of surface weld material (b)

6.3.2.4 Weld collar damage at vent riser
Table 15 — Weld collar damage at vent riser
Weld type: Aluminothermic weld
Defect type: Weld collar damage at vent riser
Appearance, causes and location:
— Weld collar damage at vent riser in aluminothermic weld is characterized by lack of material at the
rail foot.
— It is caused by incorrect removal of risers, bending the riser too much in hot condition, using sharp
tools or angle grinders can tear away material.
— It is unlikely to propagate.

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Figure 17 — Weld collar damage at vent riser

6.3.3 Thermal contraction (Hot Tear)
Table 16 — Thermal contraction
Weld type: Aluminothermic weld
Defect type: Thermal contraction
Appearance, causes and location:
— Thermal contraction in aluminothermic weld is characterized by a tear of metal during the cooling
process.
— It is a weakening of the weld and is often located in the axis of the weld, at the junction web/foot.
— It can be caused by
— too early release of the tension from the hydraulic rail tensor during solidification of the weld,
— extreme and rapid rail temperature change during solidification of the weld and
— cooling of the weld if the rail fastenings close to the weld are not removed.
— It is a planar defect that will cause a brittle fracture of the weld, often under the first load.

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Figure 18 — Thermal contraction

6.3.4 Fatigue cracks
Table 17 — Fatigue cracks
Weld type: Aluminothermic weld
Defect type: Fatigue cracks
Appearance, causes and location:
— Fatigue cracks in aluminothermic welds are initiated in small defects in the weld material, like
inclusions and porosity.
— It can derive from poor execution on the part of the welder, unfavourable environmental conditions
and the quality/suitability of the material used. It can develop due to cyclic loading or poor track
geometry and may propagate vertically or horizontally:
— In vertical propagation the break normally initiates from stress concentration sites at the edge
of the weld collar, in the foot, lower web and under head regions.
— In horizontal propagation the break normally initiates from a surface or near-surface defect in
the weld collar, in the mid- or upper-web region.
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Figure 19 — Fatigue crack

7 Documentation
7.1 General
The content and type of documentation shall be specified by the IM.
7.2 Requirements of documentation VT
The documentation and the report for visual testing of the welds should include:
— information and qualification of the testing personnel;
— date of tes
...