GB/T 20490-2023 in English

《GB/T 20490-2023钢管无损检测 无缝和焊接钢管分层缺欠的自动超声检测》由TC183（全国钢标准化技术委员会）归口，TC183SC19（全国钢标准化技术委员会钢产品无损检测分会）执行，主管部门为中国钢铁工业协会。

GB/T 20490-2023 Non-destructive testing (NDT) methods of steel tubes - Automated ultrasonic testing of seamless and welded steel tubes for the detection of laminar imperfections

1 Scope

This document specifies requirements for automated ultrasonic testing for the detection of laminar imperfections

a) in the pipe body (full peripheral testing) of seamless and welded, except submerged arc-welded, steel tubes,

b) in the area adjacent to the weld seam of welded steel tubes,

c) at the ends (full peripheral testing) of seamless and welded tubes.

This document can also be applicable to the testing of circular hollow sections.

Note: For welded tubes, see ISO 10893-9 for an alternative test method for the detection of laminar imperfections in steel strip/plate prior to tube forming.

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.

ISO 5577 Non-destructive testing- Ultrasonic inspection - Vocabulary
Note: GB/T 12604.1-2020 Non-destructive testing - Terminology - Ultrasonic testing (ISO 5577 :2017, MOD)
ISO 9712 Non-destructive testing- Qualification and certification of NDT personnel
ISO 10893-6 Non-destructive testing of steel tubes- Part 6: Radiographic testing of the weld seam of welded steel tubes for the detection of imperfections
Note: GB/T 40791-2021 Non-destructive testing of steel tubes - Radiographic testing of the weld seam of welded steel tubes for the detection of imperfections (ISO 10893-6:2019, IDT)
ISO 10893-7 Non-destructive testing of steel tubes- Part 7 : Digital radiographic testing of the weld seam of welded steel tubes for the detection of imperfections
Note: GB/T 40385-2021 Non-destructive testing of steel tubes - Digital radiographic testing of the weld seam of welded steel tubes for the detection of imperfections (ISO 10893-7 :2019, IDT)
ISO 11484 Steel products - Employer's qualification system for non-destructive testing (NDT) personnel

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 5577 and ISO 11484 and the following apply.

3.1
reference standard
artificial defect for the calibration of non-destructive testing equipment (e.g. drill holes, notches, recesses)

3.2
reference tube
tube or length of tube containing the reference standard(s)

3.3
reference sample
sample (e.g. segment of tube, plate or strip) used for validation

Note: Only the term "reference tube" is used in this document, also covering the term "reference sample".

3.4
laminar imperfection
imperfection located in the wall thickness and generally parallel to the pipe surfaces

Note: Its extension can be calculated by measuring its outlined area on the external surface.

3.5
tube
hollow long product open at both ends, of any cross-sectional shape

3.6
seamless tube
tube made by piercing a solid product to obtain a tube hollow, which is further processed, either hot or cold, into its final dimensions

3.7
welded tube
tube made by forming a hollow profile from a flat product and welding adjacent edges together, and which after welding can be further processed, either hot or cold, into its final dimensions

3.8
manufacturer
organization that manufactures products in accordance with the relevant standard(s) and declares the compliance of the delivered products with all applicable provisions of the relevant standard(s)

3.9
agreement
contractual arrangement between the manufacturer and purchaser at the time of enquiry and order

4 General requirements

4.1 Unless otherwise specified by the product standard or agreed on by the purchaser and manufacturer, an ultrasonic testing shall be carried out on tubes after completion of all the primary production process operations (rolling, heat treating, cold and hot working, sizing and primary straightening, etc.).

4.2 The tubes under test shall be sufficiently straight to ensure the validity of the test. The surfaces shall be sufficiently free of foreign matter which can interfere with the validity of the test.

4.3 This test shall be carried out by suitable trained operators qualified in accordance with ISO 9712, ISO 11484 or equivalent and supervised by competent personnel nominated by the manufacturer. In the case of third-party inspection, this shall be agreed on by the purchaser and manufacturer.

The operating authorization issued by the employer shall be according to a written procedure. Non-destructive testing operations shall be authorized by a level 3 NDT individual approved by the employer.

Note: The definition of levels 1, 2 and 3 can be found in appropriate standards, e.g. ISO 9712 and ISO 11484.

5 Test method

5.1 General

5.1.1 As specified in the product standard, the test shall be executed using an ultrasonic pulse echo technique for the detection of laminar imperfections in accordance with 5.2 or 5.3 and/or 5.4. The ultrasound shall be transmitted in the direction normal to the tube surface.

5.1.2 For testing in accordance with 5.2 or 5.3, the relative speed of movement during testing shall not vary by more than ±10%. For determining the extent of the laminated suspect area, adjacent suspect areas separated by less than the smaller of the two minor axes of the laminations shall be considered as one lamination. There may be a short length at both tube ends which cannot be tested in the case of testing in accordance with 5.2 or 5.3.

Any untested ends shall be dealt with in accordance with the requirements of the appropriate product standards (see also 5.4).

5.1.3 The ultrasonic test frequency that shall be applied shall be in the range of 2 MHz to 10 MHz.

5.1.4 The suggested maximum width of each transducer, or each active aperture when using phased array transducers, should be 25 mm measured in any direction. However, manufacturers may use larger transducers providing their capability for detecting the adopted reference standard; on request, this capability shall be demonstrated.

5.1.5 The equipment shall be capable of classifying tubes as either acceptable or suspect by means of an automated trigger/alarm level combined with a marking and/or sorting system.

5.1.6 Where manual ultrasonic testing is required, this shall be carried out in accordance with Annex A.

Note: For wall thicknesses less than 5 mm, where difficulties can occur in detecting and sizing laminar imperfections using this method of test, an alternative method of test can be agreed on by the manufacturer and purchaser

5.2 Full peripheral testing of seamless and welded (except SAW) tubes

During testing, the tubes and the transducer assembly shall be moved relative to each other such that the tube surface is scanned in order to detect laminar imperfections with a size equal to or greater than the relevant minimum lamination size, Bmin, with a circumferential dimension, Cmin, calculated as given in Table 1.