GB/T 29712-2023 English PDF (GBT29712-2023)

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GB/T 29712-2023: Non-destructive testing of welds -- Ultrasonic testing -- Acceptance levels
GB/T 29712-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 25.160.40
CCS J 33
GB/T 29712-2023 / ISO 11666:2018
Replacing GB/T 29712-2013
Non-Destructive Testing of Welds – Ultrasonic Testing –
Acceptance Levels
(ISO 11666:2018, IDT)
ISSUED ON: NOVEMBER 27, 2023
IMPLEMENTED ON: JUNE 1, 2024
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative References ... 5
3 Terms and Definitions ... 6
4 Determination of Discontinuity Length ... 6
5 Sensitivity Setting and Levels ... 6
6 Acceptance Levels ... 7
Annex A (Normative) Levels ... 11
Annex B (Normative) Fixed-Amplitude Level Technique ... 22
Foreword
This Document was drafted as per the rules specified in GB/T 1.1-2020 Directives for
Standardization – Part 1: Rules for the Structure and Drafting of Standardizing Documents.
This Document replaced GB/T 29712-2013 Non-Destructive Testing of Welds - Ultrasonic
Testing - Acceptance Levels. Compared with GB/T 29712-2013, the major technical changes of
this Documents are as follows besides the structural adjustments and editorial modifications:
a) Change the scope (see Clause 1 of this Edition; Clause 1 of the 2013 Edition);
b) Add terms and definitions (see Clause 3 of this Editon; Clause 3 of the 2013 Edition);
c) Delete the provision "If otherwise specified, alternative techniques may be used to
measure the display length" (see Clause 3 of the 2013 Edition);
d) Change the expression of the adoption method of horizontal hole technology, the flat
bottom hole technology, the rectangular slot technology, and the serial technology of the
sensitivity setting and level (see Clause 5 of this Edition; Clause 4 of the 2013 Edition);
e) Change the expression of the detection technology and level according to ISO 17640 in
Table 1 (see 6.1 of this Edition; 5.1 of the 2013 Edition);
f) Change the description of the provisions of Tables A.2 and A.3 (see 6.2 of this Edition;
5.2 of the 2013 Edition);
g) Change "group display" to "discontinuous group"; and change the definition of
discontinuous group (see 6.4 of this Edition; 5.4 of the 2013 Edition);
h) Add the assessment requirements for single acceptable discontinuities exceeding the
record level; change the definition of “cumulative length of single acceptable
discontinuities exceeding the record level”; and change the acceptance criteria for the
cumulative length of weld discontinuities (see 6.5 of this Edition; 5.5 of the 2013 Edition).
This Document equivalently adopts ISO 11666:2018 Non-Destructive Testing of Welds –
Ultrasonic Testing – Acceptance Levels.
This Document made the following minimum editorial modifications:
--- Add NOTE to Clause 5.
Please note some contents of this Document may involve patents. The issuing agency of this
Document shall not assume the responsibility to identify these patents.
This Document was proposed by China Machinery Industry Federation.
Non-Destructive Testing of Welds – Ultrasonic Testing –
Acceptance Levels
1 Scope
This Document specifies two ultrasonic acceptance levels known as acceptance level 2 (AL 2)
and acceptance level 3 (AL 3) for full penetration welded joints in ferritic steels, which
correspond to ISO 5817:2014, quality levels B and C. An acceptance level corresponding to
ISO 5817:2014, quality level D is not included in this document, as ultrasonic testing is
generally not requested for this weld quality.
These acceptance levels are applicable to testing carried out in accordance with ISO 17640.
This Document applies to the testing of full penetration ferritic steel welds, with thicknesses
from 8 mm to 100 mm. It can also be used for other types of welds, materials and thicknesses,
provided the tests have been performed with necessary consideration of the geometry and
acoustic properties of the component, and an adequate sensitivity can be employed to enable
the acceptance levels of this document to be applied. The nominal frequency of probes used in
this document is between 2 MHz and 5 MHz, unless attenuation or requirements for higher
resolution call for other frequencies. It is important to consider the use of these acceptance
levels in conjunction with frequencies outside this range carefully.
2 Normative References
The provisions in following documents become the essential provisions of this Document
through reference in this Document. For the dated documents, only the versions with the dates
indicated are applicable to this Document; for the undated documents, only the latest version
(including all the amendments) is applicable to this Document.
ISO 5577 Non-destructive testing – Ultrasonic testing – Vocabulary
NOTE: GB/T 12604.1-2020 Non-destructive testing – Terminology - Ultrasonic testing (ISO 5577:2017,
MOD)
ISO 5817:2014 Welding - Fusion-welded joints in steel, nickel, titanium and their alloys (beam
welding excluded) - Quality levels for imperfections
ISO 17635 Non-destructive testing of welds — General rules for metallic materials
using straight-beam scanning with longitudinal waves.
For techniques 1 (side-drilled holes) and 3 (rectangular notch), see Figures A.1 to A.4.
For techniques 2 [flat-bottomed holes (disk-shaped reflectors)] and 4 (tandem technique), see
Figures A.5 to A.10.
Any discontinuities providing an amplitude below the acceptance level but with a length (above
evaluation level) exceeding t,
a) for the thickness range of 8 mm ≤ t < 15 mm, or
b) for t/2 or 20 mm, whichever is larger; for all other thickness ranges beyond the provisions
a).
It shall be subject to further testing. This requires the use of additional beam angle(s), and, if
specified, the tandem technique.
The final evaluation shall be based on the maximum echo amplitude and the measured length.
6.3 Indications from transverse discontinuities
When detection of transverse discontinuities is specified, the acceptance levels stated in 6.2
apply.
6.4 Grouping of discontinuities
Grouping of discontinuities is based on the length and the separation of individually acceptable
discontinuities providing amplitudes above the recording level. The length of a group shall not
be used for further grouping.
For evaluation, a group of discontinuities shall be considered as a single one if:
a) the distance, dx, between two discontinuities is less than twice the length of the longer
discontinuity (see Figure 1);
b) the distance, dy, between two discontinuities is less than half of the thickness but not more
than 10 mm; and
c) the distance, dz, between two discontinuities is less than half of the thickness but not more
than 10 mm.
The combined length of the group of two discontinuities is l12=l1+l2+dx (see Figure 2).
The combined length, l12, and the larger maximum amplitude of the two discontinuities shall
then be assessed against the applicable acceptance levels given in Table A.1.