ISO 4773:2023

INTERNATIONAL ISO
STANDARD 4773
First edition
2023-10
Non-destructive testing — Ultrasonic
guided-wave testing using the phased-
array technique
Essais non destructifs — Essais par ondes ultrasonores guidées
utilisant la technique multiélément
Reference number
© ISO 2023
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Personnel requirements . 1
5 Principles of phased-array guided-wave testing . 2
6 Test equipment .2
6.1 General . 2
6.2 Test instrument. 3
6.3 Probe . 3
6.4 Environmental requirements. 3
7 Periodical check of the test equipment. 4
7.1 Periodical check of the instrument . 4
7.2 Periodical check of probe . 4
7.3 Check of the complete system setting . 4
7.4 Recording level . 4
8 Test procedure .4
8.1 General . 4
8.2 Pre-requisites for object . 5
8.3 Setting of the equipment . 5
8.3.1 Coating removal process for probe setup . 5
8.3.2 Setting of sensitivity and range . 5
8.3.3 Setting of DAC and TCG . 6
8.4 Classification of signals . 6
8.5 Periodical check of settings . 7
8.6 Performing the test. 7
9 Evaluating the test results . .8
9.1 General . 8
9.2 Procedure . 8
10 Test report . 8
Annex A (normative) Checklist for the testing with ultrasonic guided-waves .10
Bibliography .18
iii
Foreword
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iv
Introduction
To improve guided-wave tests, coverage will be extended from above-ground to underground
facilities, and the technology will transition from single-element use to multi-element phased-array
technology. Noticeable advantages in using the phased-array ultrasonic guided-wave technique over
the conventional single-element technique are improvements in the signal-to-noise ratio (SN ratio) and
in the testing reliability in harsh environments like buried or coated pipelines.
A low signal-to-noise ratio in buried or coated pipe reduces the sensitivity and the range of conventional
guided-wave testing. The phased-array guided-wave focusing method presented in this document can
overcome this issue. Beam focusing and steering with the proper mode selection is a key benefit.
v
INTERNATIONAL STANDARD ISO 4773:2023(E)
Non-destructive testing — Ultrasonic guided-wave testing
using the phased-array technique
1 Scope
This document specifies a concept of application of phased-array guided-wave testing for various types
of inaccessible structures, including buried pipelines.
Materials considered are carbon steel and stainless steel. This document does not include principles
and criteria for underground facilities and the phased-array ultrasonic guided-wave testing scheme.
Furthermore, this document consists of an optimized process to draw reliable test results on inaccessible
pipe cases. This document provides guidance on the use of phased-array guided-wave testing for
various types of inaccessible structures, including buried pipelines made of carbon steel and stainless
steel. The methodology outlined in this document includes an optimized process for achieving reliable
test results on inaccessible pipe cases, with adjustments made to the beam pattern of the GW's focus
location based on the defect type, location, and frequency. The process also takes into consideration the
distribution diagram of the guided waves and the characteristics of the selected mode, with optimal
focusing and steering achieved by adjusting the excitation time delay for each transducer based on the
number of circumferential arrangement intervals of a given array probe.
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, Non-destructive testing — Ultrasonic testing — Vocabulary
ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel
ISO 18211, Non-destructive testing — Guided-wave testing of above-ground pipelines and plant piping
using guided-wave testing with axial propagation
ISO 23243, Non-destructive testing — Ultrasonic testing with arrays — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5577, ISO 18211 and ISO 23243
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/
4 Personnel requirements
The personnel performing phased-array ultrasonic guided-wave testing shall be qualified in accordance
with ISO 9712 (Level 1 with an additional 6-month training).
If ISO 9712 is not applicable to a specific situation, such as in cases where the relevant industrial sector
has established other equivalent standards, those standards shall be used instead.
The personnel shall be trained on the use of the specific test equipment because there are significant
differences between the available systems and diagnostic approaches.
5 Principles of phased-array guided-wave testing
The phased-array guided-wave testing is a technique that enables focusing and steering of ultrasonic
waves by synthesizing a plurality of ultrasonic beams having a phase difference through a time delay
between different ultrasonic probes. The phased-array guided-wave technique enables focusing and
steering of ultrasonic beams.
Previously, as shown in Figure 1, only the synthesis of bulk wave signals was used. A similar principle
can be applied to the signal synthesis of guided-waves; and this principle is applied to improve the
reliability and test signals of guided-wave ultrasonic testing.
The phased-array probe is divided into torsional-mode and multi-mode modules (torsional,
longitudinal), and each module is connected to a multi-channel instrument. The multi-channel modules
are operated sequentially with time delay, focusing and steering the ultrasonic beam to the volume to
be tested.
a) b)
Key
1 probe element
2 test object
3 imperfection
Figure 1 — Schematic showing the difference between the conventional phased-array ultrasonic
testing (UT-PA) and the described guided-wave testing; a) Conventional UT-PA; b) Described
guided-wave UT-PA.
6 Test equipment
6.1 General
The pulse-echo mode or pitch-catch mode technology shall be used.
The electronic system used for signal processing and analysis shall be capable of distinguishing the
induced wave modes used in specific detection systems.
The instrument shall also have a device to display and record data.
For covered test objects, the following procedure shall be applied:
a) determine the maximum possible distance for testing according to the covering environment;
b) dismantle the covering material and remove the buried soil to install the guided-wave array
module;
c) secure access space for the operator;
d) secure access space for equipment, equipment installation and initial software operation checks;
e) prevent interference of the initial diffusely reflected signal in the sound field near the guided-
waves.
6.2 Test instrument
The test instrument shall be able to perform the following functions:
a) to generate and receive pulses in a frequency range of 20 kHz to 1 000 kHz;
b) one or more of the following guided-wave modes:
— longitudinal guided-wave mode;
— torsional guided-wave mode;
c) a focusing function to allow specific testing of suspected areas;
d) synthetic focusing:
e) focusing:
1) deliberate concentration of guided-wave modes at a single circumferential and axial position.
2) controlling a multi-mode probe module to function differently at different positions on the
surface of an object enables the possibility of focusing the testing at a specific axial and lateral
position on the object. This enhances sensitivity and spatial selectivity. To achieve this, the
data collection process needs to be repeated for each axial and lateral position of interest.
6.3 Probe
a) Probes for transmitting and receiving signals shall be able to tune proper guided-wave modes in a
pipe.
b) When using more than two guided-wave modes, the wave modes shall be applied to test object
separately, not simultaneously.
c) Probe element with a frequency range of 20 kHz to 1 000 kHz shall be used; either one continuous
ring or an individual probe may form a ring, resulting
...