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GB/T 31212-2014Non-destructive testing—Magnetic flux leakage testing—General principles (English PDF)

无损检测漏磁检测总则

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Issued by

SAMR; SAC

Level / Type

National · Recommended

Issue date

September 3, 2014

Implementation date

May 1, 2015

Scope

GB/T 31212-2014 is the English-translated version of 无损检测漏磁检测总则.

GB/T 31212-2014 specifies the general principles for the magnetic flux leakage testing of ferromagnetic materials and components. Clause 1 states that it applies to the magnetic flux leakage testing of material elements and components of regular geometry such as ropes, rods, bars, tubes and plates.

For terminology it draws on GB/T 12604.5 and GB/T 12604.6 and adds two definitions of its own in clause 3: defect equivalent, the defect magnitude assigned from the specific signal characteristics obtained in accordance with the standard, and defect sizing, the geometric description of a defect derived from the signal characteristics obtained.

Clause 4 is the general outline and opens with the principle of the method: when a ferromagnetic component is magnetised a magnetic field is generated inside it, and where corrosion, mechanical damage or another defect is present the flux lines leak out of the component and form a leakage field at the surface, which a magnetic field sensor placed in the middle of the magnetiser, usually a Hall element or a sensor coil, can detect; because the strength of the leakage field is related to the depth and size of the defect, analysis of the leakage field signal yields the defect found in the component.

The same clause illustrates the arrangement in Figure 1 and gives typical signals of different measured magnetic field components in Figure 2. The normative references include GB/T 9445 on the qualification and certification of non-destructive testing personnel and NB/T 47013.3 on the non-destructive testing of pressure equipment.

The standard was prepared and is administered by the National Technical Committee on Non-destructive Testing Standardization (SAC/TC 56), and among the drafting organisations the page names the China Special Equipment Inspection and Research Institute and the Huazhong University of Science and Technology. It was issued on 3 September 2014 and has applied since 1 May 2015.

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Document preview — GB/T 31212-2014

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

Foreword
1 Scope
2 Normative references
3 Terms and Definitions
4 Summary

Foreword

This standard was drafted in accordance with GB/T 1.1-2009 given rules.

The standard non-destructive testing by the National Standardization Technical Committee (SAC/TC56) made and centralized.

1 Scope

This standard specifies the general principle of ferromagnetic materials and components magnetic flux leakage detection.

Magnetic flux leakage inspection This standard applies to ropes, rods, bars, tubes, plates and other rules of material element geometry and components.

2 Normative references

The following documents for the application of this document is essential. For dated references, only the dated version suitable for use herein Member. For undated references, the latest edition (including any amendments) applies to this document.

GB/T 9445 NDT personnel qualification and certification

GB/T 12604.5 Terminology for nondestructive testing - Magnetic particle testing

GB/T 12604.6 Terminology for nondestructive testing Eddy current testing

NB/T 47013.3 pressure equipment NDT ultrasonic testing

3 Terms and Definitions

GB/T 12604.5 and GB/T 12604.6 defined and the following terms and definitions apply to this document.

3.1 Defects equivalent

With a particular value or common law equivalent amount, in accordance with this standard is specific signal characteristics obtained given the magnitude of the defect.

3.2 Defects quantization

According to signal characteristics obtained are given defect geometry description.

4 Summary

4.1 Principle of magnetic flux leakage detection method

The principle of magnetic flux leakage testing shown in Figure 1. When the ferromagnetic member is applied magnetizing, generates a magnetic field within the member, if the member The presence of corrosion or mechanical damage and other defects, the magnetic field lines will leak to the outside member, thereby forming a leakage magnetic field on the surface, as in the middle of magnetizer Place - a magnetic field sensor (usually a Hall element or a magnetic field sensor coil) can be detected by the leakage magnetic field due to the leakage magnetic field strength The depth and size of the defect, it can signal by the leakage magnetic field analysis to obtain the occurrence of defects on the member. Figure 2 is the measured Different amounts of magnetic field components of a typical signal Fig.

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This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 15 pages — is available in the English PDF.

Referenced standards

Normative references

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