GB/T 7735-2016 in English

《GB/T 7735-2016无缝和焊接（埋弧焊除外）钢管缺欠的自动涡流检测》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。

ChinaStandards.net is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.

This standard is prepared according to the rules given in GB/T 1.1-2009.

This standard supersedes GB/T 7735-2004 Steel tubes—The inspection method on eddy current test. This standard includes the following significant technical changes with respect to GB/T 7735-2004:
——change of the standard name;
——change of the scope (See Clause 1, and Clause 1 in 2004 edition);
——addition of contents of Normative references, Terms and definitions and General requirements (See Clause 2, 3 and 4);
——modification of content of test method (See Subclause 5.1, and Subclause 5.1 in 2004 edition)
——modification of content of test equipment (See Subclause 5.2, and Clause 7 in 2004 edition)
——modification of requirements on material quality of reference tubes (See Subclause 6.1.2, and Subclause 6.1.1 in 2004 edition)
——modification of requirements on the width and length of reference notch (See Subclause 6.5.2.2, and Subclause 6.4 in 2004 edition)
——modification of content of acceptance level and identification (See Subclause 6.5.1 and 6.5.3.2, and Subclause 6.4.1 and 6.4.2 in 2004 edition)
——addition of NOTEs after the acceptance levels, to specify the acceptance level for replaced hydrostatic test (See Subclause 6.5.1 and 6.5.2.2, and Subclause 6.4.1 and 6.4.2 in 2004 edition)
——modification of specification on equipment calibration and checking (See Clause 7, and Clause 8 in 2004 edition)
——modification of determination on suspect tubes (See Subclause 8.2, and Subclause 9.2 in 2004 edition)
——modification of content of Annex A(See Annex A, and Annex A in 2004 Edition)
This standard is identical to ISO 10893-2:2011 Non-destructive testing of steel tubes -- Part 2: Automated eddy current testing of seamless and welded (except submerged arc-welded) steel tubes for the detection of imperfections (English version), by using translation method.
The following standard has a consistency corresponding relationship to the international standard listed in the Normative references of this standard:
GB/T 9445-2015 Non-destructive testing—Qualification and certification of NDT personnel (ISO 9712:2012, IDT)
The following editorial changes are made in this standard:
——Change of the standard name according to China’s language customs;
——For the purpose of convenient use, “NOTE: Acceptance level E4H may be used as the acceptance level of eddy current testing which replaces hydrostatic test ” is added on Subcluase 6.5.1. “NOTE: Acceptance level E4 may be used as the acceptance level of eddy current testing which replaces hydrostatic test ” is added on Subclause 6.5.2.2.
This standard was proposed by China Iron and Steel Industry Association.

This standard is under the jurisdiction of the National Technical Committee 183 on Steel of Standardization Administration of China (SAC/TC 183).

This standard was drafted by Hunan Hengyang Steel Tube (Group) Co., Ltd., Shanxi Taigang Stainless Steel Tube Co., Ltd. and China Metallurgical Information standardization Institute.

The previous editions of the standards superseded by this standard are as follows:

——GB/T 7735-1995;

——GB/T 7735-2004.

Automated eddy current testing of seamless and welded (except submerged arc-welded) steel tubes for detection of imperfections


1 Scope
This standard specifies requirements for automated eddy current testing of seamless and welded tubes with the exception of submerged arc-welded (SAW) tubes, for the detection of imperfections according to the different acceptance levels as shown in Tables 1 and 2.
It is applicable to the inspection of tubes with an outside diameter greater than or equal to 4 mm. This standard can also be applicable to the testing of hollow sections.
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 9712 Non-destructive testing — Qualification and certification of personnel
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 11484 and the following apply.
3.1
reference standard
standard for the calibration of non-destructive testing equipment (e.g. drill holes, notches and 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) containing the reference standard(s)
NOTE: Only the term “reference tube” is used in this standard, also covering the term “reference sample”.
3.4
tube
hollow long product open at both ends, of any cross-sectional shape
3.5
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
3.6
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
3.7
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)
3.8
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, this eddy current inspection shall be carried out on tubes after completion of all the production process operations, such as rolling, heat treating, cold forming and hot working, sizing and primary straightening.
4.2 The tubes being tested 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 inspection shall be carried out by 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 between the purchaser and manufacturer.
The operating authorization issued by the employer shall be according to a written procedure. NDT 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 International Standards, e.g. ISO 9712 and ISO 11484.
5 Test method
5.1 Test techniques
5.1.1 The tubes shall be tested by the eddy current method for the detection of imperfections using in “absolute mode” and/or in “differential mode” one of the following alternative automated or semi-automated techniques:
a) concentric coil technique — full peripheral (see Figure 1);
b) fixed or rotating probe/pancake coil technique — full peripheral (see Figure 2);
c) segment coil technique — weld seam only (see Figure 3) or full body (see Figure 4).
For all techniques, the chosen relative speed of movement during the testing shall not vary by more than ±10 %.
It is recognized that there may be a short length at both tube ends which cannot be tested. Any untested ends shall be dealt with in accordance with the requirements of the appropriate product standards.
NOTE: See Annex A for guidelines on the limitations of the eddy current test method.
5.1.2 When testing tubes using the concentric coil technique, the maximum tube outside diameter that shall be tested shall be restricted to 180 mm (250 mm for E4H). Square and rectangular tubes, used for structural purposes, with a maximum dimension across the diagonal of 180 mm may also be tested using this technique with adequately shaped coils.
5.1.3 When testing tubes using the rotating or fixed probe/pancake coil technique, the tube and the probe/pancake coil shall be moved relative to each other or the movement shall be simulated by electronic commutation through the individual probes composing the pancake, such that the whole of the tube surface is scanned. There is no restriction on the maximum tube outside diameter using this technique.
NOTE: It is emphasized that only external surface breaking imperfections can be detected using this technique.
5.1.4 When testing the weld of welded tubes using the segment coil technique, there is no restriction on the maximum tube outside diameter. The test coil shall be maintained in proper alignment with the weld, such as that the whole of the weld is scanned.
5.1.5 When testing the full body of tubes using the segment coils technique, the maximum tube outside diameter that shall be tested shall be limited to:
— the maximum tube outside diameter shall be 219.1 mm for 2 × 180° coils,
— the maximum tube outside diameter shall be 508.0 mm for 4 × 100° coils.
NOTE It is emphasized that the test sensitivity is at a maximum at the tube surface adjacent to the test coil and decreases with increasing thickness (see Annex A).
5.2 Test equipment
The equipment shall be capable of classifying tubes as either acceptable or suspect tubes by means of an automated trigger/alarm level combined with a marking and/or sorting system.

Foreword iii
1 Scope
2 Normative references
3 Terms and definitions
4 General requirements
5 Test method
6 Reference tube
7 Equipment calibration and checking
8 Acceptance
9 Test report
Annex A (Informative) Guidance notes on limitations of eddy current test method