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GB/T 46978-2026Non-destructive testing - Methods of alternating current field measurement (ACFM) for metal structures (English PDF)

无损检测　金属结构交流电磁场检测方法

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Issued by

SAMR; SAC

Level / Type

National · Recommended

Issue date

January 28, 2026

Implementation date

January 28, 2026

Scope

GB/T 46978-2026 is the English-translated version of 无损检测　金属结构交流电磁场检测方法.

GB/T 46978-2026 is the Chinese standard "Non-destructive testing - Methods of alternating current field measurement (ACFM) for metal structures".

Its scope clause reads: This document describes a method for inspecting metal structures using alternating electromagnetic field technology, and specifies the procedures for using alternating electromagnetic field technology to inspect metal structures.

The testing method includes the process specifications, testing system, testing procedures, testing data and result evaluation, and testing report. This document applies to the detection of defects on and near the surface of metal structures with non-conductive coatings/covers less than 5 mm thick. Its clauses include terms and definitions.

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Document preview — GB/T 46978-2026

National Standard of the People's Republic of China

ICS: 19.100
Classification: J 04

Issued by: State Administration for Market Regulation; Standardization Administration of the PRC

Preface
1.Scope
2 Normative References
3.Terms and Definitions
4.Principle
5.Testing process specifications 6.
6.Detection System
7.Testing Procedures 9.
8.Evaluation of test data and results
9 Test Report
Appendix A (Normative) Performance Testing Requirements for AC Electromagnetic Field Detection Systems
Appendix C (Informative) Detection of AC Electromagnetic Fields on Underwater Metal Structures
Appendix D (Informative) AC Electromagnetic Field Testing of Drill Pipe Threads

1 Scope

This document describes a method for inspecting metal structures using alternating electromagnetic field technology, and specifies the procedures for using alternating electromagnetic field technology to inspect metal structures.

The testing method includes the process specifications, testing system, testing procedures, testing data and result evaluation, and testing report.

This document applies to the detection of defects on and near the surface of metal structures with non-conductive coatings/covers less than 5 mm thick.

2 Normative references

The contents of the following documents, through normative references within the text, constitute essential provisions of this document. Dated citations are not included.

For references to documents, only the version corresponding to that date applies to this document; for undated references, the latest version (including all amendments) applies.

This document.

GB/T 12604.6 Nondestructive Testing Terminology. Eddy Current Testing

3 Terms and Definitions

The terms and definitions defined in GB/T 12604.6 and the following terms and definitions apply to this document.

3.1 excitation element

A device that generates an alternating electromagnetic field.

Note. Includes coil and yoke.

3.2

A device for measuring magnetic fields and their changes.

Note. This is usually a magnetic sensor.

3.3

The excitation unit (3.1) induces a uniform alternating current locally in the inspected component. The defective part causes a disturbance in the induced current, which in turn leads to...

The surface magnetic field distortion is detected by measuring the magnetic field distortion signal using a magnetic measurement unit (3.2) to achieve defect detection.

3.4 ACFMprobe

probe

It can induce a uniform current field in a metal structure and measure changes in the magnetic field, and includes an excitation unit (3.1) and a magnetic measurement unit (3.2).

Probe.

3.5 BX signal

The signal of the X-direction component of the magnetic induction intensity obtained by the probe, parallel to the scanning direction of the probe (3.4).

Note. See Figure 1.

......
This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 23 pages — is available in the English PDF.

Referenced standards

Normative references

GB/T 12604.6Non-destructive testing - Terminology - Eddy current testing

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