JP3226071B2 - Magnetic flaw detection - Google Patents
Magnetic flaw detectionInfo
- Publication number
- JP3226071B2 JP3226071B2 JP33439793A JP33439793A JP3226071B2 JP 3226071 B2 JP3226071 B2 JP 3226071B2 JP 33439793 A JP33439793 A JP 33439793A JP 33439793 A JP33439793 A JP 33439793A JP 3226071 B2 JP3226071 B2 JP 3226071B2
- Authority
- JP
- Japan
- Prior art keywords
- magnetic
- flux density
- steel pipe
- magnetic flux
- flaw detection
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Landscapes
- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
Description
【0001】[0001]
【産業上の利用分野】本発明は、鋼管の、特に曲管部の
腐食減肉等の欠陥を検査するのに好適な磁気探傷法に関
するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic flaw detection method suitable for inspecting a steel pipe, particularly a curved pipe portion, for defects such as corrosion thinning.
【0002】[0002]
【従来の技術】従来、鋼管の腐食減肉等の欠陥を検査す
る方法として、以下に記載するような磁気探傷法が広範
に用いられている。すなわち、かかる磁気探傷法は、図
6に示した磁化ヘッド1を使用して鋼管2の減肉箇所3
を探知するものである。かかる磁化ヘッド1は一対の永
久磁石4a、4bと、永久磁石4a、4bに設けたワイ
ヤブラシ5とを有し、これら一対の永久磁石4a、4b
の中間の位置に磁気センサ6を配置構成したものであ
る。かかる磁化ヘッド1を、前記ワイヤブラシ5を介し
て鋼管2にそれぞれ接触させるようにする。すると、鋼
管2は磁化され、一方の永久磁石4a側から、他方の磁
石4bに向かって、ワイヤブラシ5を介して鋼管2を通
り抜けるような磁力線が形成される。その際、検査にか
かる鋼管2の減肉箇所3において前記磁力線が一部漏洩
し、その漏洩してくる磁力線を磁気センサ6によって検
知することで、減肉量を計測することができる。2. Description of the Related Art Conventionally, a magnetic flaw detection method as described below has been widely used as a method for inspecting defects such as corrosion thinning of a steel pipe. That is, the magnetic flaw detection method uses the magnetization head 1 shown in FIG.
Is to detect. The magnetization head 1 has a pair of permanent magnets 4a and 4b and a wire brush 5 provided on the permanent magnets 4a and 4b.
The magnetic sensor 6 is arranged at an intermediate position between the two. The magnetized head 1 is brought into contact with the steel pipe 2 via the wire brush 5. Then, the steel pipe 2 is magnetized, and lines of magnetic force are formed from one permanent magnet 4 a side to the other magnet 4 b so as to pass through the steel pipe 2 via the wire brush 5. At this time, the magnetic line of force partially leaks at the thinned portion 3 of the steel pipe 2 to be inspected, and the amount of thinned wall can be measured by detecting the leaked magnetic line of force with the magnetic sensor 6.
【0003】[0003]
【発明が解決しようとする課題】しかしながら、上記磁
気探傷法が適用可能なのは、直線状である鋼管2の場合
のみで、図7に示すような曲管状の箇所においては、ヨ
ーク毎にワイヤブラシと管壁の倣い状態が変わるため、
鋼管2の磁化レベルにばらつきが生じ、安定した計測が
困難であった。すなわち、倣い状態の変化により鋼管2
中の磁束密度と、永久磁石4a、4b間の空間に形成さ
れる浮遊磁界の浮遊磁束密度が変動し、これによって磁
気センサ6による漏洩磁束の検出値が変動するためであ
る。本発明は、このような不都合を改善するためになさ
れたものであって、検査すべき鋼管との倣い状態によっ
て変動する浮遊磁界を測定し、その値を基に漏洩磁力線
の磁束密度の測定値を補正するようにして安定した計測
を可能とする磁気探傷法を提供することを目的とする。However, the magnetic flaw detection method can be applied only to a straight steel pipe 2, and in a curved tubular portion as shown in FIG. Because the profiling state of the tube wall changes,
The magnetization level of the steel pipe 2 varied, and stable measurement was difficult. In other words, the steel pipe 2
This is because the magnetic flux density in the medium and the stray magnetic flux density of the stray magnetic field formed in the space between the permanent magnets 4a and 4b fluctuate, and the detection value of the leakage magnetic flux by the magnetic sensor 6 fluctuates. The present invention has been made in order to improve such inconvenience, and measures a stray magnetic field that fluctuates depending on a copying state with a steel pipe to be inspected, and based on the measured value, measures a magnetic flux density of a leakage magnetic flux line. It is an object of the present invention to provide a magnetic flaw detection method that enables stable measurement by compensating for flaws.
【0004】[0004]
【課題を解決するための手段】前記した課題を解決する
ために、本発明は、一対の磁石を有する磁化ヘッドによ
り鋼管を磁化して鋼管から漏洩する磁力線の磁束密度を
検出することにより、鋼管の腐食減肉等の欠陥を探知す
る磁気探傷法において、鋼管の減肉箇所において漏洩す
る磁力線を検知する一方、一対の磁石間の空間に形成さ
れる浮遊磁束密度を検知し、この浮遊磁束密度にかかる
検知信号から鋼管中の磁束密度を求め、この鋼管中の磁
束密度から、漏洩磁力線にかかる検知信号の補正係数を
求めて、漏洩磁力線にかかる検知信号に加味して補正
し、補正された検出値を取り出すことを特徴とする。SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to a steel pipe by magnetizing a steel pipe with a magnetizing head having a pair of magnets and detecting the magnetic flux density of lines of magnetic force leaking from the steel pipe. In a magnetic flaw detection method to detect defects such as corrosion thinning of steel, leakage occurs at the thinned part of the steel pipe.
While detecting the magnetic flux lines formed in the space between the pair of magnets, detecting the magnetic flux density in the steel pipe from the detection signal applied to the floating magnetic flux density, and detecting the magnetic flux density in the steel pipe.
From the flux density, find the correction coefficient of the detection signal applied to the leakage magnetic field line, and correct it by taking into account the detection signal applied to the leakage magnetic field line
Then, the corrected detected value is taken out .
【0005】[0005]
【作用】浮遊磁束密度を検知し、この浮遊磁束密度にか
かる検知信号から鋼管中の磁束密度を求め、この鋼管中
の磁束密度から、漏洩磁力線にかかる検知信号の補正係
数を求めて、漏洩磁力線にかかる検知信号に加味して補
正し、補正された検出値を取り出すようにしたので、浮
遊磁束密度の変動によらず、安定した計測が可能とな
る。[Function] Detects the stray magnetic flux density, finds the magnetic flux density in the steel pipe from the detection signal concerning the stray magnetic flux density,
From the magnetic flux density, the correction coefficient of the detection signal applied to the leakage magnetic field line is calculated and compensated by taking into account the detection signal applied to the leakage magnetic field line.
Since the corrected and detected value is taken out , stable measurement is possible regardless of the fluctuation of the stray magnetic flux density.
【0006】[0006]
【実施例】次に、本発明にかかる磁気探傷法について、
一実施例を挙げ、以下詳細に説明する。図1に磁気探傷
を実施するための磁化ヘッド10を検査すべき鋼管11
に接触させたところを示す。前記磁化ヘッド10は、一
対の永久磁石12a、12bと、永久磁石12a、12
bに設けたワイヤブラシ13とを有し、これら一対の永
久磁石12a、12bの中間の位置に磁気センサ14、
そして、この磁気センサ14から図中、下方へ適宜間隔
離れた位置に磁化レベル補正用センサ15を配置構成し
たものである。かかる磁化ヘッド10により、鋼管11
の減肉箇所16において漏洩する磁力線を磁気センサ1
4によって検知する構成である。前記磁化レベル補正用
センサ15は、永久磁石12a、12b間の空間に形成
される浮遊磁束密度を測定するものである。なお、かか
る磁化レベル補正用センサ15は、図2に示すように、
永久磁石12aに近接した位置の空間部に配置するよう
にしてもよい。Next, a magnetic flaw detection method according to the present invention will be described.
An embodiment will be described in detail below. FIG. 1 shows a steel pipe 11 to be inspected for a magnetized head 10 for performing magnetic flaw detection.
The place where it contacted is shown. The magnetizing head 10 includes a pair of permanent magnets 12a and 12b and permanent magnets 12a and 12b.
b, and a wire brush 13 provided at a position between the pair of permanent magnets 12a and 12b.
In addition, a magnetization level correction sensor 15 is arranged at a position spaced apart from the magnetic sensor 14 by a suitable distance in the figure. With such a magnetized head 10, a steel pipe 11
The line of magnetic force leaking at the thinned portion 16 of the magnetic sensor 1
4. The magnetization level correction sensor 15 measures a floating magnetic flux density formed in a space between the permanent magnets 12a and 12b. In addition, such a magnetization level correction sensor 15 is, as shown in FIG.
You may make it arrange | position in the space part of the position close to the permanent magnet 12a.
【0007】次に、以上のような磁化ヘッド10により
磁気探傷を実行するための手順を図3に示したブロック
図に基づき、以下説明する。図3に示すように、磁気セ
ンサ14の検知信号と磁化レベル補正用センサ15の検
知信号を演算手段16に取り込み、所定の演算結果にか
かる信号を出力する構成である。すなわち、ワイヤブラ
シ13と鋼管11とのならい状態によって変動する浮遊
磁束密度を磁化レベル補正用センサ15によって検知
し、演算手段16において、磁化レベル補正用センサ1
5による浮遊磁束密度にかかる値から鋼管11中の磁束
密度を求め、この鋼管11中の磁束密度から、さらに磁
気センサ14の補正係数を求めて、磁気センサ14の検
知信号に加味して補正し、補正された検出値を取り出す
構成である。ここで、図4、図5にそれぞれ、浮遊磁束
密度−鋼管中の磁束密度、鋼管中の磁束密度−磁気セン
サの補正係数についての関係の一例を表すグラフを示
す。図4によると、浮遊磁束密度と鋼管中の磁束密度と
の間には、浮遊磁束密度の増加と共に鋼管中の磁束密度
は減少し、図5によると鋼管中の磁束密度と磁気センサ
の補正係数との間には、鋼管中の磁束密度の増加により
磁気センサの補正係数が減少するという関係がある。言
い換えれば、浮遊磁束密度と磁気センサの補正係数と
は、浮遊磁束密度が増加すると磁気センサの補正係数が
増加するという関係にある。すなわち、前記演算手段1
6は、前記浮遊磁束密度−鋼管中の磁束密度、鋼管中の
磁束密度−磁気センサの補正係数の関係に基づいて、磁
気センサ14の補正された出力値を取り出す構成であ
り、その具体的構成手段は、適宜である。Next, a procedure for executing magnetic flaw detection by the above-described magnetization head 10 will be described with reference to a block diagram shown in FIG. As shown in FIG. 3, a detection signal of the magnetic sensor 14 and a detection signal of the magnetization level correction sensor 15 are taken into the calculation means 16 and a signal relating to a predetermined calculation result is output. That is, the floating magnetic flux density that varies by copying the state of the wire brush 13 and the steel pipe 11 is detected by the magnetization level correction sensor 15, the arithmetic unit 16, the magnetization level correction sensor 1
The magnetic flux density in the steel pipe 11 is obtained from the value related to the stray magnetic flux density according to 5, and the correction coefficient of the magnetic sensor 14 is further obtained from the magnetic flux density in the steel pipe 11 and corrected in consideration of the detection signal of the magnetic sensor 14. , And takes out the corrected detection value. Here, FIGS. 4 and 5 are graphs each showing an example of the relationship between the stray magnetic flux density—the magnetic flux density in the steel pipe and the magnetic flux density in the steel pipe—the correction coefficient of the magnetic sensor. According to FIG. 4, between the stray magnetic flux density and the magnetic flux density in the steel pipe, the magnetic flux density in the steel pipe decreases as the stray magnetic flux density increases, and according to FIG. 5, the magnetic flux density in the steel pipe and the correction coefficient of the magnetic sensor. There is a relationship that the correction coefficient of the magnetic sensor decreases due to an increase in the magnetic flux density in the steel pipe. In other words, the relationship between the stray magnetic flux density and the correction coefficient of the magnetic sensor is such that as the stray magnetic flux density increases, the correction coefficient of the magnetic sensor increases. That is, the calculating means 1
Reference numeral 6 denotes a configuration for taking out a corrected output value of the magnetic sensor 14 based on the relationship between the floating magnetic flux density—the magnetic flux density in the steel pipe, and the magnetic flux density in the steel pipe—the correction coefficient of the magnetic sensor. Means are appropriate.
【0008】以上のような磁気探傷法によれば、リフト
オフが変化して浮遊磁束密度が変動しても、その浮遊磁
束密度に応じて磁気センサ14の補正された出力を取り
出すようにしているので、リフトオフ、すなわち浮遊磁
束密度の変動によらず、安定した計測が可能となる。従
って、鋼管11の直線部分のみならず曲線形状の箇所に
おいても問題なく、腐食減肉等を探知することができ
る。According to the magnetic flaw detection method described above, even if the lift-off changes and the stray magnetic flux density fluctuates, the corrected output of the magnetic sensor 14 is taken out according to the stray magnetic flux density. Thus, stable measurement can be performed regardless of the lift-off, that is, the fluctuation of the stray magnetic flux density. Accordingly, corrosion thinning and the like can be detected without any problem not only in the straight portion of the steel pipe 11 but also in a curved portion.
【0009】[0009]
【発明の効果】以上、本発明によれば、検査すべき鋼管
との倣い状態によって変動する浮遊磁界を測定し、その
値を基に漏洩磁力線の磁束密度の測定値を補正するよう
にしたので、検査すべき鋼管の曲管部等において発生す
る、ワイヤブラシの倣い状態の変化に起因するヨーク毎
の漏洩磁力線の磁束密度の測定値のばらつきを補正する
ことができ、安定した計測が可能となる。As described above, according to the present invention, the measured value of the magnetic flux density of the leakage magnetic force lines is corrected based on the measurement of the stray magnetic field which fluctuates according to the state of following the steel pipe to be inspected. It is possible to correct the variation of the measured value of the magnetic flux density of the leakage magnetic force line for each yoke caused by the change of the copying state of the wire brush, which occurs in the curved pipe portion of the steel pipe to be inspected, thereby enabling stable measurement. Become.
【0010】[0010]
【図1】本発明にかかる磁気探傷法を実施するための磁
化ヘッドの一例を示す模式的な側面説明図である。FIG. 1 is a schematic side view illustrating an example of a magnetization head for performing a magnetic flaw detection method according to the present invention.
【図2】本発明にかかる磁気探傷法を実施するための磁
化ヘッドの別例を示す模式的な側面説明図である。FIG. 2 is a schematic side view showing another example of the magnetization head for performing the magnetic flaw detection according to the present invention.
【図3】本発明にかかる磁気探傷法を実施するための磁
気センサの出力信号の補正手順を示すブロック図であ
る。FIG. 3 is a block diagram showing a procedure for correcting an output signal of a magnetic sensor for performing a magnetic flaw detection method according to the present invention.
【図4】浮遊磁束密度と鋼管中の磁束密度との関係を示
すグラフである。FIG. 4 is a graph showing a relationship between a stray magnetic flux density and a magnetic flux density in a steel pipe.
【図5】鋼管中の磁束密度と磁気センサの補正係数との
関係を示すグラフである。FIG. 5 is a graph showing a relationship between a magnetic flux density in a steel pipe and a correction coefficient of a magnetic sensor.
【図6】従来の磁気探傷法を実施するための磁化ヘッド
の一例を示す模式的な側面説明図である。FIG. 6 is a schematic side view showing an example of a magnetized head for performing a conventional magnetic flaw detection method.
【図7】探知すべき鋼管の曲管部を図6に示す磁化ヘッ
ドにより、欠陥箇所を検出する際の概略的な要部説明図
である。FIG. 7 is a schematic explanatory view of a principal part when detecting a defective portion in a bent portion of a steel pipe to be detected by the magnetization head shown in FIG. 6;
10 磁化ヘッド 11 鋼管 12a、12b 永久磁石 13 ワイヤブラシ 14 磁気センサ 15 磁化レベル補正用セ
ンサ 16 演算手段DESCRIPTION OF SYMBOLS 10 Magnetization head 11 Steel pipe 12a, 12b Permanent magnet 13 Wire brush 14 Magnetic sensor 15 Magnetization level correction sensor 16 Calculation means
───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.7,DB名) G01N 27/72 - 27/90 ──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. 7 , DB name) G01N 27/72-27/90
Claims (1)
鋼管を磁化して鋼管から漏洩する磁力線の磁束密度を検
出することにより、鋼管の腐食減肉等の欠陥を探知する
磁気探傷法において、鋼管の減肉箇所において漏洩する
磁力線を検知する一方、一対の磁石間の空間に形成され
る浮遊磁束密度を検知し、この浮遊磁束密度にかかる検
知信号から鋼管中の磁束密度を求め、この鋼管中の磁束
密度から、漏洩磁力線にかかる検知信号の補正係数を求
めて、漏洩磁力線にかかる検知信号に加味して補正し、
補正された検出値を取り出すことを特徴とする磁気探傷
法。In a magnetic flaw detection method for detecting defects such as corrosion thinning of a steel pipe by magnetizing the steel pipe with a magnetizing head having a pair of magnets and detecting a magnetic flux density of lines of magnetic force leaking from the steel pipe, Leaks at thinning points
While detecting the lines of magnetic force, the stray magnetic flux density formed in the space between the pair of magnets is detected, and the magnetic flux density in the steel pipe is obtained from the detection signal applied to the stray magnetic flux density.
From the density, the correction coefficient of the detection signal applied to the leakage magnetic field line is obtained, and corrected in consideration of the detection signal applied to the leakage magnetic field line,
A magnetic flaw detection method wherein a corrected detection value is taken out .
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP33439793A JP3226071B2 (en) | 1993-12-28 | 1993-12-28 | Magnetic flaw detection |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP33439793A JP3226071B2 (en) | 1993-12-28 | 1993-12-28 | Magnetic flaw detection |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH07198683A JPH07198683A (en) | 1995-08-01 |
JP3226071B2 true JP3226071B2 (en) | 2001-11-05 |
Family
ID=18276915
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP33439793A Expired - Fee Related JP3226071B2 (en) | 1993-12-28 | 1993-12-28 | Magnetic flaw detection |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP3226071B2 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN111337566A (en) * | 2020-02-25 | 2020-06-26 | 清华大学 | Method for identifying defect edge in magnetic flux leakage detection |
Families Citing this family (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB0112983D0 (en) * | 2001-05-30 | 2001-07-18 | Advanced Eng Solutions Ltd | Pipe condition detecting apparatus |
KR101250559B1 (en) | 2011-01-06 | 2013-04-03 | 한국표준과학연구원 | Crack detection device |
JP6359858B2 (en) * | 2014-04-04 | 2018-07-18 | キヤノン電子株式会社 | Magnetic field detection device and magnetic identification device |
CN111044605B (en) * | 2019-12-13 | 2021-08-06 | 清华大学 | Method and device for magnetic flux leakage detection lift-off compensation and defect depth analysis |
CN111060587B (en) * | 2019-12-13 | 2021-08-20 | 清华大学 | Magnetic flux leakage detection probe attitude compensation method and device |
CN111089896B (en) * | 2019-12-13 | 2021-12-14 | 清华大学 | Magnetic excitation isotropic defect contour imaging device and imaging method |
JP2021162360A (en) * | 2020-03-30 | 2021-10-11 | Jfeスチール株式会社 | Method and device for inspection |
CN112098507A (en) * | 2020-08-20 | 2020-12-18 | 云浮(佛山)氢能标准化创新研发中心 | Pipe wall defect determining method |
CN112834606B (en) * | 2021-01-07 | 2022-11-29 | 清华大学 | Method and device for identifying defects of inner wall and outer wall based on focusing magnetic flux leakage composite detection |
-
1993
- 1993-12-28 JP JP33439793A patent/JP3226071B2/en not_active Expired - Fee Related
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN111337566A (en) * | 2020-02-25 | 2020-06-26 | 清华大学 | Method for identifying defect edge in magnetic flux leakage detection |
CN111337566B (en) * | 2020-02-25 | 2021-10-22 | 清华大学 | Method for identifying defect edge in magnetic flux leakage detection |
Also Published As
Publication number | Publication date |
---|---|
JPH07198683A (en) | 1995-08-01 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US6265870B1 (en) | Eddy current sensor assembly for detecting structural faults in magnetically permeable objects | |
JP3226071B2 (en) | Magnetic flaw detection | |
KR100671630B1 (en) | On-line flaw detection method of magnetic leak detector and strip of magnetic flaw detector | |
CN107850570B (en) | Defect measuring method, defect measuring device, and inspection probe | |
WO2012165296A1 (en) | Magnetic property measurement method and magnetic property measurement device | |
Kim et al. | A new design of MFL sensors for self-driving NDT robot to avoid getting stuck in curved underground pipelines | |
CN110187001B (en) | Defect detection method adopting surface magnetic conductance technology | |
JPH04269653A (en) | Leakage magnetic flux detector | |
JP2002005893A (en) | Method for judging defect and method for calibrating sensor in apparatus for inspecting inside of pipe | |
JPH1183808A (en) | Leakage flux flaw detecting method | |
JPH01110251A (en) | Evaluation of integrity for one-side weld part | |
JPH07260745A (en) | Magnetic shield structure of magnetic sensor | |
JPH075408Y2 (en) | Metal flaw detection probe | |
JPH03105245A (en) | Remote field type probe for eddy current flaw detection | |
KR20210079551A (en) | Apparatus and Method for Sensing Quality of Steel Plate Surface | |
JP3589375B2 (en) | Correction method of individual difference of magnetic sensor in inspection of pipe using leakage magnetic flux pig | |
JP3680977B2 (en) | Data correction method for pipe inspection using leakage flux pig | |
JPH11211407A (en) | Position detecting method for in-pipe moving device | |
JP2001235090A (en) | In-pipe inspecting device | |
JP2002168665A (en) | Electromagnetic flowmeter | |
JP3568084B2 (en) | Detection method of vertical seam position of pipe using leakage magnetic flux pig | |
JP2001349873A (en) | Data processing method in in-tube inspection device | |
JPH06324022A (en) | Eddy current flaw-detecting device | |
JPS63138259A (en) | Magnetism probing method | |
JP4634628B2 (en) | Degradation diagnosis method for steel |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
LAPS | Cancellation because of no payment of annual fees |