SIST EN 583-6:2009

Non-destructive testing - Ultrasonic examination - Part 6: Time-of-flight diffraction technique as a method for detection and sizing of discontinuities

This European Standard defines the general principles for the application of the Time-Of-Flight Diffraction (TOFD) technique for both detection and sizing of discontinuities in low alloyed carbon steel components. It could also be used for other types of materials, provided the application of the TOFD technique is performed with necessary consideration of geometry, acoustical properties of the materials and the sensitivity of the examination.
Although it is applicable, in general terms, to discontinuities in materials and applications covered by EN 583 1, it contains references to the application on welds. This approach has been chosen for reasons of clarity as to the ultrasonic probe positions and directions of scanning.
Unless otherwise specified in the referencing documents, the minimum requirements of this standard are applicable.
Unless explicitly stated otherwise, this standard is applicable to the following product classes as defined in EN 583 2:
- class 1, without restrictions;
- classes 2 and 3, restrictions will apply as stated in Clause 9.
The inspection of products of classes 4 and 5 will require special procedures. These are addressed in Clause 9 as well.
The techniques to use TOFD for weld inspection are described in CEN/TS 14751.
The related acceptance criteria are given in prEN 15617.

Zerstörungsfreie Prüfung - Ultraschallprüfung - Teil 6: Beugungslaufzeittechnik, eine Technik zum Auffinden und Ausmessen von Inhomogenitäten

Diese Europäische Norm legt die allgemeinen Prinzipien für die Anwendung der Beugungslaufzeittechnik
(TOFD) für das Auffinden und die Größenbestimmung von Inhomogenitäten in Bauteilen aus niedrig legierten
Kohlenstoffstählen fest. Das TOFD-Verfahren kann auch auf andere Werkstoffarten angewendet werden,
wenn es mit der notwendigen Berücksichtigung von Geometrie, akustischen Eigenschaften der Werkstoffe
sowie Nachweisempfindlichkeit der Prüfung angewendet wird.
Obwohl es im allgemeinen bei Inhomogenitäten in Werkstoffen anwendbar ist, die in EN 583-1 behandelt
werden, sind Hinweise für die Prüfung von Schweißnähten enthalten. Dieser Weg wurde zur Verdeutlichung
der Ausrichtungen des Ultraschallkopfes und der Prüfrichtungen gewählt.
Soweit in Bezugsdokumenten nichts anderes festgelegt worden ist, sind die Mindestanforderungen dieser
Norm anwendbar.
Wenn es nicht ausdrücklich anders angegeben wird, ist diese Norm auf folgende in EN 583-2 festgelegten
Produktklassen anwendbar:
⎯ Klasse 1, ohne Einschränkungen;
⎯ Klassen 2 und 3, mit den in Abschnitt 9 angegebenen Einschränkungen.
Die Prüfung von Produkten der Klassen 4 und 5 erfordert Spezialverfahren. Auf diese wird auch in Abschnitt 9
hingewiesen.
Die Verfahren mit TOFD zur Inspektion von Schweißnähten sind in CEN/TS 14751 beschrieben. Die
entsprechenden Zulässigkeitskriterien sind in prEN 15617 festgelegt.

Essais non destructifs - Contrôle ultrasonore - Partie 6: Technique de diffraction du temps de vol utilisée comme méthode de détection et de dimensionnement des discontinuités

La présente Norme européenne définit les principes généraux pour l’application de la technique de diffraction du temps de vol (TOFD) pour la détection et le dimensionnement des discontinuités dans les composants en acier au carbone faiblement allié. Elle peut également être employée pour d’autres types de matériaux, à condition que l’application de la technique TOFD tienne compte de la géométrie, des propriétés acoustiques des matériaux et de la sensibilité de l’examen.
Bien qu’elle soit applicable, en termes généraux, aux discontinuités des matériaux et aux applications couvertes par l’EN 583-1, elle contient des références aux applications sur les soudures. Cette approche a été choisie pour des raisons de clarté en termes de position des traducteurs ultrasonores et de direction de balayage.
Sauf indications contraires dans les documents de référence, les exigences minimales de la présente norme sont applicables.
Sauf dispositions contraires explicites, la présente norme s’applique aux classes de produits suivantes, telles que définies dans l’EN 583-2 :
- classe 1 : sans restriction ;
- classes 2 et 3 : les restrictions de l’Article 9 s’appliquent.
L’examen des produits des classes 4 et 5 requiert des modes opératoires particuliers. Ceux-ci sont également traités dans l’Article 9.
Les techniques d’utilisation de la méthode TOFD pour l’examen des soudures sont décrites dans la CEN/TS 14751.
Les critères d’acceptation associés sont donnés dans le prEN 15617.

Neporušitveno preskušanje - Ultrazvočne preiskave - 6. del: Tehnika zvočne poti kot metoda za odkrivanje in ugotavljanje velikosti nezveznosti

General Information

• Status: Withdrawn
• Publication Date: 22-Feb-2009
• Withdrawal Date: 29-May-2014
• ICS: 19.100 - Non-destructive testing
• Technical Committee: PKG - Testing of metallic materials
• Current Stage: 9900 - Withdrawal (Adopted Project)
• Start Date: 29-May-2014
• Due Date: 21-Jun-2014
• Completion Date: 30-May-2014
• Ref Project: EN 583-6:2008 - Non-destructive testing - Ultrasonic examination - Part 6: Time-of-flight diffraction technique as a method for detection and sizing of discontinuities

Relations

• Revised: SIST ENV 583-6:2000 - Non-destructive testing - Ultrasonic examination - Part 6: Time-of-flight diffraction technique as a method for detection and sizing of discontinuities
• Effective Date: 01-Apr-2009
• Replaced By: SIST EN ISO 16828:2014 - Non-destructive testing - Ultrasonic testing - Time-of-flight diffraction technique as a method for detection and sizing of discontinuities (ISO 16828:2012)
• Effective Date: 01-Jul-2014

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 583-6:2009
01-april-2009
1HSRUXãLWYHQRSUHVNXãDQMH8OWUD]YRþQHSUHLVNDYHGHO7HKQLND]YRþQHSRWL
NRWPHWRGD]DRGNULYDQMHLQXJRWDYOMDQMHYHOLNRVWLQH]YH]QRVWL
Non-destructive testing - Ultrasonic examination - Part 6: Time-of-flight diffraction
technique as a method for detection and sizing of discontinuities
Zerstörungsfreie Prüfung - Ultraschallprüfung - Teil 6: Beugungslaufzeittechnik, eine
Technik zum Auffinden und Ausmessen von Inhomogenitäten
Essais non destructifs - Contrôle ultrasonore - Partie 6: Technique de diffraction du
temps de vol utilisée comme méthode de détection et de dimensionnement des
discontinuités
Ta slovenski standard je istoveten z: EN 583-6:2008
ICS:
19.100 Neporušitveno preskušanje Non-destructive testing
SIST EN 583-6:2009 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 583-6:2009

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SIST EN 583-6:2009
EUROPEAN STANDARD
EN 583-6
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2008
ICS 19.100 Supersedes ENV 583-6:2000
English Version
Non-destructive testing - Ultrasonic examination - Part 6: Time-
of-flight diffraction technique as a method for detection and
sizing of discontinuities
Essais non destructifs - Contrôle ultrasonore - Partie 6: Zerstörungsfreie Prüfung - Ultraschallprüfung - Teil 6:
Technique de diffraction du temps de vol utilisée comme Beugungslaufzeittechnik, eine Technik zum Auffinden und
méthode de détection et de dimensionnement des Ausmessen von Inhomogenitäten
discontinuités
This European Standard was approved by CEN on 29 October 2008.
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. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN Management Centre or to any CEN member.
This European Standard exists 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 Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 583-6:2008: E
worldwide for CEN national Members.

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SIST EN 583-6:2009
EN 583-6:2008 (E)
Contents Page
Foreword .4
1 Scope .5
2 Normative references .5
3 Terms, definitions, symbols and abbreviations .6
3.1 Terms and definitions .6
3.2 Abbreviations .6
3.3 Symbols .6
4 General .7
4.1 Principle of the technique .7
4.2 Requirements for surface condition and couplant .9
4.3 Materials and process type .9
5 Qualification of personnel .9
6 Equipment requirements .9
6.1 Ultrasonic equipment and display .9
6.2 Ultrasonic probes . 10
6.3 Scanning mechanisms . 11
7 Equipment set-up procedures . 11
7.1 General . 11
7.2 Probe choice and probe separation. 12
7.2.1 Probe selection . 12
7.2.2 Probe separation. 13
7.3 Time window setting . 13
7.4 Sensitivity setting . 13
7.5 Scan resolution setting . 14
7.6 Setting of scanning speed . 14
7.7 Checking system performance . 14
8 Interpretation and analysis of data . 14
8.1 Basic analysis of discontinuities . 14
8.1.1 General . 14
8.1.2 Characterisation of discontinuities . 14
8.1.3 Estimation of discontinuity position. 15
8.1.4 Estimation of discontinuity length . 15
8.1.5 Estimation of discontinuity depth and height . 16
8.2 Detailed analysis of discontinuities . 16
8.2.1 General . 16
8.2.2 Additional scans . 17
8.2.3 Additional algorithms . 18
9 Detection and sizing in complex geometries . 18
10 Limitations of the technique . 18
10.1 General . 18
10.2 Accuracy and resolution . 19
10.2.1 General . 19
10.2.2 Errors in the lateral position . 19
10.2.3 Timing errors . 19
10.2.4 Errors in sound velocity . 19
10.2.5 Errors in probe centre separation . 19
10.2.6 Spatial resolution . 20
10.3 Dead zones . 20
2

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EN 583-6:2008 (E)
11 TOFD examination without data recording . 20
12 Test procedure . 21
13 Test report . 21
Annex A (normative) Reference blocks . 22
Bibiliography…………………………………………………………………………………………………….23

3

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SIST EN 583-6:2009
EN 583-6:2008 (E)
Foreword
This document (EN 583-6:2008) has been prepared by Technical Committee CEN/TC 138 “Non-destructive
testing”, the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by June 2009, and conflicting national standards shall be withdrawn at
the latest by June 2009.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes ENV 583-6:2000.
The relevant changes from the previous edition are as follows:
− the terminology was revised;
− the references were updated.
EN 583, Non-destructive testing — Ultrasonic examination consists of the following parts:
 EN 583-1, Non-destructive testing — Ultrasonic examination — Part 1: General principles
 EN 583-2, Non-destructive testing — Ultrasonic examination — Part 2: Sensitivity and range setting
 EN 583-3, Non-destructive testing — Ultrasonic examination — Part 3: Transmission technique
 EN 583-4, Non-destructive testing — Ultrasonic examination — Part 4: Examination for discontinuities
perpendicular to the surface
 EN 583-5, Non-destructive testing — Ultrasonic examination — Part 5: Characterization and sizing of
discontinuities
 EN 583-6, Non-destructive testing — Ultrasonic examination — Part 6: Time-of-flight diffraction technique
as a method for detection and sizing of discontinuities
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.

4

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SIST EN 583-6:2009
EN 583-6:2008 (E)
1 Scope
This European Standard defines the general principles for the application of the Time-Of-Flight Diffraction
(TOFD) technique for both detection and sizing of discontinuities in low alloyed carbon steel components. It
could also be used for other types of materials, provided the application of the TOFD technique is performed
with necessary consideration of geometry, acoustical properties of the materials and the sensitivity of the
examination.
Although it is applicable, in general terms, to discontinuities in materials and applications covered by
EN 583-1, it contains references to the application on welds. This approach has been chosen for reasons of
clarity as to the ultrasonic probe positions and directions of scanning.
Unless otherwise specified in the referencing documents, the minimum requirements of this standard are
applicable.
Unless explicitly stated otherwise, this standard is applicable to the following product classes as defined in
EN 583-2:
 class 1, without restrictions;
 classes 2 and 3, restrictions will apply as stated in Clause 9.
The inspection of products of classes 4 and 5 will require special procedures. These are addressed in
Clause 9 as well.
The techniques to use TOFD for weld inspection are described in CEN/TS 14751.
The related acceptance criteria are given in prEN 15617.
2 Normative references
The following referenced documents are indispensable for the application 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.
EN 473, Non-destructive testing — Qualification and certification of NDT personnel — General principles
EN 583-1, Non-destructive testing — Ultrasonic examination — Part 1: General principles
EN 583-2, Non-destructive testing — Ultrasonic examination — Part 2: Sensitivity and range setting
EN 12668-1, Non-destructive testing — Characterization and verification of ultrasonic examination
equipment — Part 1: Instruments
EN 12668-2, Non-destructive testing — Characterization and verification of ultrasonic examination
equipment — Part 2: Probes
EN 12668-3, Non-destructive testing — Characterization and verification of ultrasonic examination
equipment — Part 3: Combined equipment
5

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EN 583-6:2008 (E)
3 Terms, definitions, symbols and abbreviations
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
scanning surface dead zone
zone where indications may be obscured due to the interface echo (lateral wave)
3.1.2
back wall dead zone
dead zone where signals may be obscured by the presence of the back wall echo
3.1.3
A-scan
display of the ultrasonic signal amplitude as a function of time
3.1.4
B-scan
display of the time-of-flight of the ultrasonic signal as a function of probe displacement
3.1.5
non-parallel scan
scan perpendicular to the ultrasonic beam direction (see Figure 4)
3.1.6
parallel scan
scan parallel to the ultrasonic beam direction (see Figure 5)
3.2 Abbreviations
 TOFD: Time-Of-Flight Diffraction
3.3 Symbols

Figure 1 — Coordinate definition
x coordinate parallel to the scanning surface and parallel to a predetermined reference line. In
case of weld inspection this reference line should coincide with the weld. The origin of the
6

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SIST EN 583-6:2009
EN 583-6:2008 (E)
axes may be defined as best suits the specimen under examination (see Figure 1);
discontinuity length;
∆x
y coordinate parallel to the scanning surface, perpendicular to the predetermined reference
line (see Figure 1);
δy error in lateral position;
z coordinate perpendicular to the scanning surface (see Figure 1);
discontinuity height;
∆z
d depth of a discontinuity tip below the scanning surface;
error in depth;
δd
D scanning-surface dead zone;
ds
D back wall dead zone;
dw
c
sound velocity;
error in sound velocity;
δc
R spatial resolution;
t time-of-flight from the transmitter to the receiver;
time-of-flight difference between the lateral wave and a second ultrasonic signal;
∆t
δt error in time-of-flight;
t time-of-flight at depth d;
d
t duration of the ultrasonic pulse measured at 10 % of the peak amplitude;
p
t time-of-flight of the back wall echo;
w
S half the distance between the index points of two ultrasonic probes;
δS error in half the probe separation;
W wall thickness.
4 General
4.1 Principle of the technique
The TOFD technique relies on the interaction of ultrasonic waves with the tips of discontinuities. This
interaction results in the emission of diffracted waves over a large angular range. Detection of the diffracted
waves makes it possible to establish the presence of the discontinuity. The time-of-flight of the recorded
signals is a measure for the height of the discontinuity, thus enabling sizing of the defect. The dimension of
the discontinuity is always determined from the time-of-flight of the diffracted signals. The signal amplitude is
not used in size estimation.
7

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EN 583-6:2008 (E)

Key
1 transmitter d discontinuity
2 receiver e lower tip
a lateral wave f back wall echo
b upper tip
Figure 2 — Basic TOFD configuration
The basic configuration for the TOFD technique consists of a separate ultrasonic transmitter and receiver (see
Figure 2). Wide-angle beam compression wave probes are normally used since the diffraction of ultrasonic
waves is only weakly dependent on the orientation of the discontinuity tip. This enables the inspection of a
certain volume in one scan. However, restrictions apply to the size of the volume that can be inspected during
a single scan (see 7.2).
The first signal to arrive at the receiver after emission of an ultrasonic pulse is usually the lateral wave which
travels just beneath the upper surface of the test specimen.
In the absence of discontinuities, the second signal to arrive at the receiver is the back wall echo.
These two signals are normally used for reference purposes. If mode conversion is neglected, any signals
generated by discontinuities in the material should arrive between the lateral wave and the back wall echo,
since the latter two correspond, respectively, to the shortest and longest paths between transmitter and
receiver. For similar reasons the diffracted signal generated at the upper tip of a discontinuity will arrive before
the signal generated at the lower tip of the discontinuity. A typical pattern of indications (A-scan) is shown in
Figure 3. The height of the discontinuity can be deduced from the difference in time-of-flight of the two
diffracted signals (see 8.1.5). Note the phase reversal between the lateral wave and the back wall echo, and
between echoes of the upper and lower tip of the discontinuity.
Where access to both surfaces of the specimen is possible and discontinuities are distributed throughout the
specimen thickness, scanning from both surfaces will improve the overall precision, particularly in regard to
discontinuities near the surfaces.

8

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EN 583-6:2008 (E)
Key
X amplitude b upper tip
Y time c lower tip
a lateral wave d back wall echo
Figure 3 — Schematic A-scan of an embedded discontinuity
4.2 Requirements for surface condition and couplant
Care shall be taken that the surface condition meets at least the requirements stated in EN 583-1. Since the
diffracted signals may be weak, the degradation of signal quality due to poor surface condition will have a
severe impact on inspection reliability.
Different coupling media can be used, but their type shall be compatible with the materials to be examined.
Examples are: water (possibly containing an agent e.g. wetting, anti-freeze, corrosion inhibitor), contact paste,
oil, grease, cellulose paste containing water, etc.
The characteristics of the coupling medium shall remain constant throughout the examination. It shall be
suitable for the temperature range in which it will be used.
4.3 Materials and process type
Due to the relatively low signal amplitudes that are used in the TOFD technique, the method can be applied
routinely on materials with relatively low levels of attenuation and scatter for ultrasonic waves. In general,
application on unalloyed and low alloyed carbon steel components and welds is possible, but also on fine
grained austenitic steels and aluminium.
Coarse-grained materials and materials with significant anisotropy however, such as cast iron, austenitic weld
materials and high-nickel alloys, will require additional validation and additional data-processing.
By mutual agreement, a representative test specimen with artificial and/or natural discontinuities can be used
to confirm inspectability. Remember that diffraction characteristics of artificial defects can differ significantly
from those of real defects.
5 Qualification of personnel
Personnel performing examinations with the TOFD technique shall, as a minimum, be qualified in accordance
with EN 473, and shall have received additional training and examination on the use of the TOFD technique
on the product classes to be tested, as specified in a written practice.
6 Equipment requirements
6.1 Ultrasonic equipment and display
Ultrasonic equipment used for the TOFD technique shall, as a minimum, comply with the requirements of
EN 12668-1, EN 12668-2 and EN 12668-3.
In addition, the following requirements shall apply:
 receiver bandwidth shall, as a minimum, range between 0,5 and 2 times the nominal probe frequency at -
6 dB, unless specific materials and product classes require a larger bandwidth. Appropriate band filters
can be used;
 transmitting pulse can either be unipolar or bipolar. The rise time shall not exceed 0,25 times the period
corresponding to the nominal probe frequency;
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 unrectified signals shall be digitised with a sampling rate of at least six times the nominal probe
frequency;
 for general applications, combinations of ultrasonic equipment and scanning mechanisms (see 6.3) shall
be capable of acquiring and digitizing signals with a rate of at least one A-scan per 1 millimetre scan
length. Data acquisition and scanning mechanism movement shall be synchronized for this purpose;
 to select an appropriate portion of the time base within which A-scans are digitized, a window with
programmable position and length shall be present. Window start shall be programmable between 0 µs
and 200 µs from the transmitting pulse, window length shall be programmable between 5 µs and 100 µs.
In this way, the appropriate signals (lateral or creeping wave, back wall signal, one or more mode
converted signals as described in 4.1) can be selected to be digitized and displayed;
 digitised A-scans should be displayed in amplitude related grey or single-colour levels, plotted adjacently
to form a B-scan. See Figures 4 and 5 for typical B-scans of non-parallel and parallel scans respectively.
The number of grey or single-colour scales should at least be 64;
 for archiving purposes, the equipment shall be capable of storing all A-scans or B-scans (as appropriate)
on a magnetic or optical storage medium such as hard disk, tape or optical disk. For reporting purposes, it
shall be capable of making hard copies of A-scans or B-scans (as appropriate);
 equipment should be capable of performing signal averaging.
In order to achieve the relatively high gain settings required for typical TOFD-signals, a pre-amplifier may be
used, which should have a flat response over the frequency range of interest. This pre-amplifier shall be
positioned as close as possible to the receiving probe.
Additional requirements regarding features for basic and advanced analysis of discontinuities are described in
Clause 8.
6.2 Ultrasonic probes
Ultrasonic probes used for the TOFD technique shall comply with at least the following requirements:
 number of probes: 2 (transmitter and receiver);
 type: any suitable probe (see 7.2);
 wave mode: usually compression wave; the use of shear wave probes is more complex but may be
agreed upon in special cases;
 both probes shall have the same centre frequency within a tolerance of ± 20 %; for details on probe
frequency selection, see 7.2;
 pulse length of both the lateral wave and the back wall echo shall not exceed two cycles, measured at
10 % of the peak amplitude;
 pulse repetition rate shall be set such that no interference occurs between signals caused by successive
transmission pulses.
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EN 583-6:2008 (E)

Key
1 reference line 6 lateral wave
2 direction of probe displacement (x-direction) 7 discontinuity upper tip
3 transmitter 8 discontinuity lower tip
4 receiver 9 back wall reflection
5 transit time (through wall extent)
Figure 4 — Non-parallel scan, with the typical direction of probe displacement shown on the left and
the corresponding B-scan shown on the right
6.3 Scanning mechanisms
Scanning mechanisms shall be used to maintain a constant distance and alignment between the index points
of the two probes.
An additional function of scanning mechanisms is to provide the ultrasonic equipment with probe position
information in order to enable the generation of position-related B-scans. Information on probe position can be
provided by means of e.g. incremental magnetic or optical encoders, or potentiometers.
Scanning mechanisms in TOFD can either be motor or manually driven. They shall be guided by means of a
suitable guiding mechanism (steel band, belt, automatic track following systems, guiding wheels, etc.).
Guiding accuracy with respect to the centre of a reference line (e.g. the centre line of a weld) should be kept
within a tolerance of ± 10 % of the probe index point separation (probe centre separation PCS).
7 Equipment set-up procedures
7.1 General
Probe selection and probe configuration are important equipment set-up parameters. They largely determine
the overall accuracy, the signal-to-noise ratio and the coverage of the region of interest of the TOFD
technique.
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Key
1 reference line 6 lateral wave
2 direction of probe displacement (y-direction) 7 discontinuity upper tip
3 transmitter 8 discontinuity lower tip
4 receiver 9 back wall reflection
5 transit time (through wall extent)
Figure 5 — Parallel scan, with the typical direction of probe displacement shown on the left and the
corresponding B-scan shown on the right
The set-up procedure described in this subclause intends to ensure:
 sufficient system gain and signal-to-noise ratio to detect the diffracted signals of interest;
 acceptable resolution and adequate coverage of the region of interest;
 efficient use of the dynamic range of the system.
7.2 Probe choice and probe separation
7.2.1 Probe selection
In this clause typical probe arrangements are given for TOFD in order to achieve good detection capabilities
on both thin and thick specimens. Note that these arrangements are not mandatory and that the exact
requirements to achieve a specification should be checked.
For steel thicknesses up to 70 mm, a single pair of probes can be used. The recommended probe selection
parameters to achieve sufficient resolution and adequate coverage are shown in Table 1 for three different
ranges of wall thicknesses.
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EN 583-6:2008 (E)
Table 1 — Recommended probe selection parameters for steel thicknesses up to 70 mm
Wall thickness Centre frequency Transducer size Nominal probe
angle


mm MHz mm
°
< 10 10 up to 15 2 up to 6 50 up to 70
10 up to < 30 5 up to 10 2 up to 6 50 up to 60
30 up to < 70 2 up to 5 6 up to 12 45 up to 60
For thicknesses greater than 70 mm, the wall thickness shall be divided into more than one inspection zone,
each zone covering a different depth region. Table 2 shows the recommended centre frequencies, transducer
sizes and nominal probe angles
...