GB1567166A - Apparatus and method for the non-destructive testing of ferromagnetic material - Google Patents

Apparatus and method for the non-destructive testing of ferromagnetic material Download PDF

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Publication number
GB1567166A
GB1567166A GB376376A GB376376A GB1567166A GB 1567166 A GB1567166 A GB 1567166A GB 376376 A GB376376 A GB 376376A GB 376376 A GB376376 A GB 376376A GB 1567166 A GB1567166 A GB 1567166A
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magnetic field
flux
magnet
pipe
detector
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GB376376A
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British Gas Corp
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British Gas Corp
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Priority to GB376376A priority Critical patent/GB1567166A/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
    • G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)

Description

(54) APPARATUS AND METHOD FOR THE NON DESTRUCTIVE TESTING OF FERROMAGNETIC MATERIAL (71) We, BRITISH GAS CORPORATION, of 59 Bryanston Street, London, W1A 2AZ, a British Body Corporate, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:- This invention relates to the non-destructive testing of ferro-magnetic materials and, in particular, to the testing of pipes usable for the transport of gas and other substances.
Manufacture of perfect piping materials is not economically feasible. Commercially available pipe will have defects ranging from atom-sized disclocations in the metal to gross flaws, such as major metal discontinuities, which are visible to the unaided eye. Typical defects are cracks or tears, shrinkage cavities, pits, inclusions, porosity and surface scabs and blisters. For a given application, a specifiication will have been established setting permissible limits to the defects which may be present. It is therefore necessary for the development of a non-destructive testing method to ascertain whether or not the materials comply with the desired specifications.
Among the methods of non-destructive testing commonly applied to piping and tubing, fabricated pipe components and welded joints are radiographic inspection with xrays and radioactive isotopes, ultrasonic inspection, dye penetrant inspection, magnetic particle inspection and eddy current testing. Most of these methods have the disadvantage that they are not readily applicable to the testing of pipelines in situ.
Development of methods to overcome this drawback has been carried out and a new method of non-destructive testing particularly applicable to ferromagnetic materials has been devised. This method depends on the principle that when a magnetic field is created in a ferromagnetic material, local imperfections cause variations in the leakage flux. These variations can be detected and thus provide an indication of the presence of imperfections.
According to the present invention there is provided a method for the non-destructive testing of a body of ferromagnetic material for mechanical defects and inhomogeneities comprising the successive application to a region of said body of a first magnetic field produced by first magnetic field producing means and of a second magnetic field, of different intensity from that of said first magnetic field, produced by second magnetic field producing means, measuring the leakage flux induced adjacent said region by said first and second field producing means by means of first and second flux detector means associated with said first and second magnetic field producing means respectively and determining from the output signals of said flux detector means the presence or absence of defects and inhomogeneities in said region.
The invention further provides apparatus for non-destructive testing of a body of ferromagnetic material comprising first means for applying a first magnetic field to said body, second means for applying a second magnetic field of different intensity from that of said first field, to said body, first and second detector means for detecting leakage flux adjacent said body induced by said first and second magnetic field application means respectively, and carrier means for transporting said first and second magnetic field application means and said detector means past a predetermined region of said body.
The invention will now be described with reference to the accompanying drawings in which: Figure 1 shows in schematic section a length of pipeline being traversed by a pig used in the invention, Figure 2 is a graphical representation showing typical leakage signals from various defects A to F, both internal and external, with an arrangement shown in Figure 5.
Figure 3 is a graphical representation of signals from the same defects as in Figure 2, but detecting only the internal defects A, C, D, E with an arrangement shown in Figure 6.
Figure 4a shows the signals from various defects, both itnernal (I1, I2) and external (eel, E2) using high flux magnets, Figure 4b shows the signals indicating only internal defects as detected by the arrangement shown in Figure 7, the arrangement having a detector oriented to detect the component of flux parallel to the pipe surface and scanning over the same sample of pipe as in Figure 4a, and Figures 5, 6 and 7 show different arrangements of permanent magnetic poles for obtaining the desired geometry of magnetic flux.
Referring now to Figure 1 of the drawings, this shows schematically a pig or godevil such as is typically used in gas pipeline cleaning operations. The pig has a body 1 carrying at each extremity a rubber cup 2 which co-operates with the wall 3 of the pipeline to form a partial seal. The pig is driven along the pipeline by the differential pressure on the cups created by gas flowing through the pipe. The cups also serve to clean the inner surfaces of the pipe. The pig carries apparatus 4 for the non-destructive testing of the pipeline. In an alternative embodiment, it may tow a further section or sections suspended by cups or other means which carry the apparatus for the nondestructive testing of the pipeline.
It has been found that a magnetic field measurement device oriented to detect the component of flux normal to the pipe surface at a point between the poles of a magnet acts as a convenient defect sensor.
The detector can also be oriented to detect the component of field parallel to the pipe surface either axially along the pipe or around its circumference. Typical signals created by defects are shown in Figure 2.
It is possible to utilise this method in an apparatus mounted on a pig. Typical arrangements for creating the desired magnetic fields are shown in Figure 5. In the arrangement of Figure 5 two completely separate magnet sections 7, 8 are employed, the larger magnet section 8 providing a strong uniform magnetic field tangential to the pipe surface near the detectors 10 to detect faults on both internal and external surfaces, and a smaller magnet 7 giving a small area field adjacent to the magnet and of lower intensity than that generated by magnet section 8, with detectors 9 to detect defects on the internal surface of the pipe only. The magnetic field detectors 9, 10 can be magnetodiodes, Hall detectors, or coils.
An alternative device is shown in Figure 6. This consists instead of magnet 7 of a magnet 11 with a magnetisation direction normal to the pipe surface and detector alongside and at an oblique angle to both the direction of motion and the normal to the surface. The selection of position of the magnet and detector and angle of the detector is small to give a minimum change in the output signal for motion of the arrangement away from the pipe (lift-off) since increasing lift-off will reduce the magnet strength but increase the angle of field through the detector, giving compensation of the system to pig vibrations.
In the arrangement of Figure 7 the pole 13 on either the leading or trailing pole of the magnet 14 bleeds some of the flux to provide a relatively low intensity magnetic field nearly normal to the pipe surface. In both embodiments the pole leakage flux is detected by magneto-diode pairs 9, 10, Hall probes or coils.
It will be apparent to those skilled in the art that other features may be included without departing from the scope of the invention as defined by the claims. For example the pig may carry a tape recorder to log meausrements, or alternatively the measuring apparatus on the pig may communicate in real time by cable or radio link direct with data processing or indicating apparatus without the pipe.
The pig may also carry drive means to cause it to traverse the pipe at a predetermined velocity and/or assume a desired orientation with respect to the pipe.
WHAT WE CLAIM IS: 1. A method for the non-destructive testing of a body of ferromagnetic material for mechanical defects and inhomogeneities comprising the successive application to a region of said body of a first magnetic field produced by first magnetic field producing means and of a second magnetic field, of different intensity from that of said first magnetic field, produced by second magnetic field producing means, measuring the leakage flux induced adjacent said region by said first and said second field producing means by mean of first and second flux detector means associated with said first and second magnetic field producing means respectively and determining from the output signals of said flux detector means the presence or absence of defects and inhomogeneities in said region.
2. A method for the non-destructive testing of a body of ferromagnetic material as claimed in Claim 1, wherein means for application of said magnetic fields and means for the measurement of said leakage flux are mounted on transporting means which is
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (14)

**WARNING** start of CLMS field may overlap end of DESC **. Figure 2 is a graphical representation showing typical leakage signals from various defects A to F, both internal and external, with an arrangement shown in Figure 5. Figure 3 is a graphical representation of signals from the same defects as in Figure 2, but detecting only the internal defects A, C, D, E with an arrangement shown in Figure 6. Figure 4a shows the signals from various defects, both itnernal (I1, I2) and external (eel, E2) using high flux magnets, Figure 4b shows the signals indicating only internal defects as detected by the arrangement shown in Figure 7, the arrangement having a detector oriented to detect the component of flux parallel to the pipe surface and scanning over the same sample of pipe as in Figure 4a, and Figures 5, 6 and 7 show different arrangements of permanent magnetic poles for obtaining the desired geometry of magnetic flux. Referring now to Figure 1 of the drawings, this shows schematically a pig or godevil such as is typically used in gas pipeline cleaning operations. The pig has a body 1 carrying at each extremity a rubber cup 2 which co-operates with the wall 3 of the pipeline to form a partial seal. The pig is driven along the pipeline by the differential pressure on the cups created by gas flowing through the pipe. The cups also serve to clean the inner surfaces of the pipe. The pig carries apparatus 4 for the non-destructive testing of the pipeline. In an alternative embodiment, it may tow a further section or sections suspended by cups or other means which carry the apparatus for the nondestructive testing of the pipeline. It has been found that a magnetic field measurement device oriented to detect the component of flux normal to the pipe surface at a point between the poles of a magnet acts as a convenient defect sensor. The detector can also be oriented to detect the component of field parallel to the pipe surface either axially along the pipe or around its circumference. Typical signals created by defects are shown in Figure 2. It is possible to utilise this method in an apparatus mounted on a pig. Typical arrangements for creating the desired magnetic fields are shown in Figure 5. In the arrangement of Figure 5 two completely separate magnet sections 7, 8 are employed, the larger magnet section 8 providing a strong uniform magnetic field tangential to the pipe surface near the detectors 10 to detect faults on both internal and external surfaces, and a smaller magnet 7 giving a small area field adjacent to the magnet and of lower intensity than that generated by magnet section 8, with detectors 9 to detect defects on the internal surface of the pipe only. The magnetic field detectors 9, 10 can be magnetodiodes, Hall detectors, or coils. An alternative device is shown in Figure 6. This consists instead of magnet 7 of a magnet 11 with a magnetisation direction normal to the pipe surface and detector alongside and at an oblique angle to both the direction of motion and the normal to the surface. The selection of position of the magnet and detector and angle of the detector is small to give a minimum change in the output signal for motion of the arrangement away from the pipe (lift-off) since increasing lift-off will reduce the magnet strength but increase the angle of field through the detector, giving compensation of the system to pig vibrations. In the arrangement of Figure 7 the pole 13 on either the leading or trailing pole of the magnet 14 bleeds some of the flux to provide a relatively low intensity magnetic field nearly normal to the pipe surface. In both embodiments the pole leakage flux is detected by magneto-diode pairs 9, 10, Hall probes or coils. It will be apparent to those skilled in the art that other features may be included without departing from the scope of the invention as defined by the claims. For example the pig may carry a tape recorder to log meausrements, or alternatively the measuring apparatus on the pig may communicate in real time by cable or radio link direct with data processing or indicating apparatus without the pipe. The pig may also carry drive means to cause it to traverse the pipe at a predetermined velocity and/or assume a desired orientation with respect to the pipe. WHAT WE CLAIM IS:
1. A method for the non-destructive testing of a body of ferromagnetic material for mechanical defects and inhomogeneities comprising the successive application to a region of said body of a first magnetic field produced by first magnetic field producing means and of a second magnetic field, of different intensity from that of said first magnetic field, produced by second magnetic field producing means, measuring the leakage flux induced adjacent said region by said first and said second field producing means by mean of first and second flux detector means associated with said first and second magnetic field producing means respectively and determining from the output signals of said flux detector means the presence or absence of defects and inhomogeneities in said region.
2. A method for the non-destructive testing of a body of ferromagnetic material as claimed in Claim 1, wherein means for application of said magnetic fields and means for the measurement of said leakage flux are mounted on transporting means which is
caused to traverse said region.
3. A non-destructive method as claimed in Claim 1 or Claim 2, wherein a second magnetic field is derived by diverting part of the magnetic flux of a first magnetic field.
4. A non-destructive method as claimed in either Claim 1 or Claim 2, wherein first and second magnetic fields are created by independent magnet systems.
5. A non-destructive method as claimed in any one of the preceding Claims wherein the orientation of said magnetic fields with respect to the body of ferromagnetic material is so chosen as to reduce the sensitivity of the measurement of flux to variations in separation of the measuring means and the body.
6. Apparatus for the non-destructive testing of a body of ferromagnetic material comprising first means for applying a first magnetic field to said body; second means for applying a second magnetic field of different intensity from that of said first field to said body, first and second detector means for detecting leakage flux adjacent said body induced by said first and second magnetic field application means respectively, and carrier means for transporting said first and second magnetic field application means and said detector means past a predetermined region of said body.
7. Apparatus for the non-destructive testing of a body of ferromagnetic material as claimed in Claim 6, wherein said first and second magnetic field application means comprise independent magnet systems.
8. Apparatus for the non-destructive testing of a body of ferromagnetic material as claimed in Claim 6, wherein said second magnetic field application means is integral with said first magnetic field application means and consists of diverting means to divert a portion of the magnetic flux emanating from said first magnetic field applications means.
9. Apparatus as claimed in any one of the preceding Claims 6 to 8, wherein said carrier means is operable by differential fluid pressure.
10. Apparatus as claimed in any one of Claims 6 to 9, wherein said carrier means also carries signal processing means for processing signals derived from said detector means.
11. Apparatus as claimed in Claim 10, wherein said signal processing means is a tape recorder.
12. Apparatus as claimed in Claim 10, wherein said signal processing means is a data transmitter.
13. Apparatus for the non-destructive testing of a body of ferromagnetic material substantially as herein described with reference to and as shown in the accompanying drawings.
14. A method of testing a body of ferromagnetic material using apparatus as claimed in any one of the preceding Claims 6 to 13.
GB376376A 1976-12-16 1976-12-16 Apparatus and method for the non-destructive testing of ferromagnetic material Expired GB1567166A (en)

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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2117116A (en) * 1982-03-24 1983-10-05 British Gas Corp Pipeline gauging vehicles
GB2159954A (en) * 1984-06-06 1985-12-11 British Gas Corp Apparatus, system and method for detecting a discontinuity in a pipe or conduit
EP0176932A2 (en) * 1984-09-27 1986-04-09 Nukem GmbH Method and apparatus for the non-destructive testing of ferromagnetic bodies by means of magnetisation
EP0193168A2 (en) * 1985-02-25 1986-09-03 Kubota Limited Method of inspecting carburization and probe therefor
FR2587492A1 (en) * 1985-07-16 1987-03-20 Nukem Gmbh METHOD AND DEVICE FOR THE NON-DESTRUCTIVE EXAMINATION OF FERROMAGNETIC PARTS HAVING SECTIONS OF SURFACES THAT CONNECT TO ARRAYS OR CORNERS, IN PARTICULAR TO PARTS WITH ROTATION SYMMETRY
US4789827A (en) * 1986-10-31 1988-12-06 Electric Power Research Institute Magnetic flux leakage probe with radially offset coils for use in nondestructive testing of pipes and tubes
US5739685A (en) * 1994-06-23 1998-04-14 Sumitomo Metal Industries Limited Method and apparatus for flaw detection by leakage fluexes and leakage flux sensor
WO2006042025A1 (en) * 2004-10-07 2006-04-20 Battelle Memorial Institute Pipeline inspection apparatus and method
WO2015055995A3 (en) * 2013-10-14 2015-06-11 Advanced Engineering Solutions Ltd Pipeline condition detecting apparatus and method
WO2019094169A1 (en) * 2017-11-13 2019-05-16 Exxonmobil Research And Enginering Company Methods and systems for nondestructive material inspection using magnetic means
WO2019094171A1 (en) * 2017-11-13 2019-05-16 Exxonmobil Research And Engineering Company Methods of using nondestructive material inspection systems
US10823701B2 (en) 2017-11-13 2020-11-03 Exxonmobil Research And Engineering Company Methods and systems for nondestructive material inspection
US10883965B2 (en) 2017-11-13 2021-01-05 Exxonmobil Research And Engineering Company Methods of using nondestructive material inspection systems

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2117116A (en) * 1982-03-24 1983-10-05 British Gas Corp Pipeline gauging vehicles
GB2159954A (en) * 1984-06-06 1985-12-11 British Gas Corp Apparatus, system and method for detecting a discontinuity in a pipe or conduit
EP0176932A2 (en) * 1984-09-27 1986-04-09 Nukem GmbH Method and apparatus for the non-destructive testing of ferromagnetic bodies by means of magnetisation
EP0176932A3 (en) * 1984-09-27 1986-12-30 Nukem Gmbh Method and apparatus for the non-destructive testing of ferromagnetic bodies by means of magnetisation
US4763070A (en) * 1984-09-27 1988-08-09 Nukem Gmbh Method and apparatus to compensate for lateral changes of a ferromagnetic body during magnetic testing
EP0193168A2 (en) * 1985-02-25 1986-09-03 Kubota Limited Method of inspecting carburization and probe therefor
EP0193168A3 (en) * 1985-02-25 1989-01-25 Kubota Limited Method of inspecting carburization and probe therefor
US5128613A (en) * 1985-02-25 1992-07-07 Kubota Ltd. Method of inspecting magnetic carburization in a non-permeable material and probe therefore
FR2587492A1 (en) * 1985-07-16 1987-03-20 Nukem Gmbh METHOD AND DEVICE FOR THE NON-DESTRUCTIVE EXAMINATION OF FERROMAGNETIC PARTS HAVING SECTIONS OF SURFACES THAT CONNECT TO ARRAYS OR CORNERS, IN PARTICULAR TO PARTS WITH ROTATION SYMMETRY
US4789827A (en) * 1986-10-31 1988-12-06 Electric Power Research Institute Magnetic flux leakage probe with radially offset coils for use in nondestructive testing of pipes and tubes
US5739685A (en) * 1994-06-23 1998-04-14 Sumitomo Metal Industries Limited Method and apparatus for flaw detection by leakage fluexes and leakage flux sensor
WO2006042025A1 (en) * 2004-10-07 2006-04-20 Battelle Memorial Institute Pipeline inspection apparatus and method
US7218102B2 (en) 2004-10-07 2007-05-15 Battelle Memorial Institute Pipeline inspection apparatus and method
WO2015055995A3 (en) * 2013-10-14 2015-06-11 Advanced Engineering Solutions Ltd Pipeline condition detecting apparatus and method
AU2014335928B2 (en) * 2013-10-14 2017-09-07 Advanced Engineering Solutions Ltd Pipeline condition detecting apparatus and method
US9976986B2 (en) 2013-10-14 2018-05-22 Advanced Engineering Solutions Ltd. Pipeline condition detecting apparatus and method
WO2019094169A1 (en) * 2017-11-13 2019-05-16 Exxonmobil Research And Enginering Company Methods and systems for nondestructive material inspection using magnetic means
WO2019094171A1 (en) * 2017-11-13 2019-05-16 Exxonmobil Research And Engineering Company Methods of using nondestructive material inspection systems
US10823701B2 (en) 2017-11-13 2020-11-03 Exxonmobil Research And Engineering Company Methods and systems for nondestructive material inspection
US10883965B2 (en) 2017-11-13 2021-01-05 Exxonmobil Research And Engineering Company Methods of using nondestructive material inspection systems

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PS Patent sealed
732 Registration of transactions, instruments or events in the register (sect. 32/1977)
PE20 Patent expired after termination of 20 years

Effective date: 19961215