### Abstract

Non-destructive testing techniques are gen-erally used for the evaluation of material properties and the detection of defects in pipelines. Especially, the measure-ment of magnetic flux leakage (MFL) is one of the most used methods for in-service monitoring of corrosion in buried oil and gas pipelines. However, for the geometrical reconstruction of defects in a pipeline from measured signals (the inverse problem), the magnetic properties of the mate-rial need to be known accurately. Due to the pipe geometry and wall thickness measurement of the bulk properties is complicated. In particular, the permeability of ferromagnetic steels shows a non-linear and hysteretic behaviour.

Current research is focussed on the measurement and simulation of the permeability of pipeline material. The magnetic properties of a small ferromagnetic test sample is first investigated using a transformer set up in order to find a correct fitting equation for the non-linear permeability as a function of the magnetic flux density. This equation is then used for model simulations of a MFL test set up. Refitting the parameters of the permeability equation to the perme-ability of the pipeline material in the MFL set up proved that flux leakage signals could be predicted accurately for sev-eral defects by model simulation.

Current research is focussed on the measurement and simulation of the permeability of pipeline material. The magnetic properties of a small ferromagnetic test sample is first investigated using a transformer set up in order to find a correct fitting equation for the non-linear permeability as a function of the magnetic flux density. This equation is then used for model simulations of a MFL test set up. Refitting the parameters of the permeability equation to the perme-ability of the pipeline material in the MFL set up proved that flux leakage signals could be predicted accurately for sev-eral defects by model simulation.

Original language | English |
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Title of host publication | 10th International IMEKO TC7 Symposium |

Place of Publication | Tomsk |

Publisher | Tomsk Polytechnic University |

Pages | 321-326 |

ISBN (Print) | 5-93629-167-7 |

Publication status | Published - 30 Jun 2004 |

Event | 10th IMEKO TC7 International Symposium on Advances of Measurement Science 2004 - Saint-Petersburg, Russian Federation Duration: 30 Jun 2004 → 2 Jul 2004 Conference number: 10 |

### Conference

Conference | 10th IMEKO TC7 International Symposium on Advances of Measurement Science 2004 |
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Abbreviated title | IMEKO TC7 |

Country | Russian Federation |

City | Saint-Petersburg |

Period | 30/06/04 → 2/07/04 |

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## Cite this

Heida, C., & Regtien, P. (2004). Estimation of permeability for magnetic flux leakage modelling. In

*10th International IMEKO TC7 Symposium*(pp. 321-326). Tomsk: Tomsk Polytechnic University.