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US-12625061-B2 - Method and inspection device for examining the cathodic protection of a ferromagnetic pipeline

US12625061B2US 12625061 B2US12625061 B2US 12625061B2US-12625061-B2

Abstract

A method is provided for examining the cathodic protection of a metallic and in particular ferromagnetic pipeline. An inspection device is also provided for examining the cathodic protection of a pipeline, in particular of a ferromagnetic pipeline. The inspection device is formed to be able to pass through the pipeline and in particular be driven by the medium, and includes a magnetizing device serving to create an alternating magnetic field. A magnet unit and a measuring device are provided, and includes at least one magnetic field sensor serving to measure a magnetic field formed on the inner side of the wall of the pipeline.

Inventors

  • Andrey Danilov
  • Ben BOSSE
  • Patrik Rosen

Assignees

  • ROSEN IP AG

Dates

Publication Date
20260512
Application Date
20220506
Priority Date
20210507

Claims (20)

  1. 1 . A method for examining a cathodic protection of a ferromagnetic pipeline, the method comprising: creating a primary alternating magnetic field and herewith a local change in permeability in a wall of the ferromagnetic pipeline by a magnetizing device of an inspection device moved through the pipeline, wherein a secondary direct current (DC) magnetic field is caused by a DC current of cathodic protection being formed in the wall of the ferromagnetic pipeline; using a measuring device of the inspection device moved through the ferromagnetic pipeline to measure a resultant magnetic field that emerges from superposition of the primary alternating magnetic field and the secondary DC magnetic field; using a computing device to analyze signal components of at least the secondary DC magnetic field giving consideration to the local change in the permeability; and determining a magnitude of the DC current of the cathodic protection based on the signal components of the secondary DC magnetic field.
  2. 2 . The method as claimed in claim 1 , wherein measurement of the resultant magnetic field takes place while the primary alternating magnetic field is created.
  3. 3 . The method as claimed in claim 1 , further comprising: determining, with the computing device, a spectrum of the secondary DC magnetic field.
  4. 4 . The method as claimed in claim 3 , wherein using the computing device to analyze signal components of at least the secondary DC magnetic field includes: selecting, from the signal components, an even multiple of a frequency of a directional change of the primary alternating magnetic field for determining the DC current.
  5. 5 . The method as claimed in claim 1 , further comprising: determining the magnitude of the DC current of the cathodic protection using one or more regression functions in the computing device based on an amplitude of at least one even multiple of a frequency of a directional change of the primary alternating magnetic field.
  6. 6 . The method as claimed in claim 5 , wherein the magnitude of DC current is determined additionally with analysis data of the secondary DC magnetic field being normalized and/or calibrated by analysis data of the primary alternating magnetic field.
  7. 7 . The method as claimed in claim 1 , further comprising: determining, with the computing device, measurement conditions associated with measurement of the resultant magnetic field based on a spectrum of the primary alternating magnetic field.
  8. 8 . The method as claimed in claim 1 , further comprising: varying and at least increasing a voltage of the cathodic protection for a measurement run of the inspection device through the ferromagnetic pipeline.
  9. 9 . The method as claimed in claim 1 , further comprising: determining the magnitude of the DC current of the cathodic protection by fusing a multiplicity of data from a measurement run of the inspection device through the ferromagnetic pipeline.
  10. 10 . The method as claimed in claim 1 , wherein measurement of the resultant magnetic field is implemented by at least one magnetic field sensor which is positioned at least substantially at a fixed distance from the wall at a time of the measurement.
  11. 11 . The method as claimed in claim 10 , wherein the magnetizing device revolves on a carrier in a longitudinal direction of the ferromagnetic pipeline.
  12. 12 . The method as claimed in claim 10 , wherein a distance of at least two magnet units of the magnetizing device from an inner side of the wall varies.
  13. 13 . The method as claimed in claim 1 , further comprising: applying, during a measurement run of the inspection device through the ferromagnetic pipeline, an additional current to an inner wall side of the ferromagnetic pipeline by two contacts spaced apart in a longitudinal direction of the ferromagnetic pipeline.
  14. 14 . The method as claimed in claim 1 , wherein the magnitude of the DC current is derived based on a database with calibration data.
  15. 15 . An inspection device for examining a cathodic protection of a pipeline, the inspection device being formed to be able to pass through a pipeline, the inspection device comprising: a magnetizing device configured to create an alternating magnetic field, the magnetizing device having: a measuring device including at least one magnetic field sensor configured to measure a magnetic field formed on an inner side of a wall of the pipeline, at least one carrier configured to be rolled through the pipeline in a longitudinal direction thereof in an operational state, the at least one carrier having an at least substantially circular perimeter in a section running transversely to an axis of rotation, and, at least two magnet units positioned along the perimeter of the at least one carrier, the at least two magnet units configured to create an alternating magnetic field, magnetic field directions of which run opposite one another, wherein the at least two magnetic units are configured such that the magnetic field formed on the inner side of a wall of the pipeline is caused by a DC current of cathodic protection being formed in the wall of the ferromagnetic pipeline.
  16. 16 . The inspection device as claimed in claim 15 , wherein the magnetic field directions of the at least two magnet units are formed parallel or radially to the axis of rotation of the at least one carrier.
  17. 17 . The inspection device as claimed in claim 15 , wherein, along the perimeter of the at least one carrier, at least one magnetic field sensor is arranged on or in the at least one carrier.
  18. 18 . The inspection device as claimed in claim 17 , wherein the at least one magnetic field sensor is a coil with windings running in a circumferential direction.
  19. 19 . The inspection device as claimed in claim 17 , further including a multiplicity of magnetic field sensors arranged next to one another along the perimeter.
  20. 20 . The inspection device as claimed in claim 15 , wherein a part of the measuring device is arranged in a holder for arrangement close to the wall.

Description

CROSS REFERENCE This application claims priority to PCT Application No. PCT/EP2022/062342, filed May 6, 2022, which itself claims priority to Belgian Patent Application No. BE2021/5375, filed May 7, 2021, the entireties of both of which are hereby incorporated by reference. FIELD OF THE INVENTION The present invention relates to a method for examining the cathodic protection of a metallic and in particular ferromagnetic pipeline. Further, the invention relates to an inspection device for examining the cathodic protection of a pipeline, in particular of a ferromagnetic pipeline, the inspection device being formed to be able to pass through the pipeline and in particular be driven by the medium, and comprising a magnetizing device serving to create an alternating magnetic field and having at least a magnet unit and a measuring device comprising at least one magnetic field sensor and serving to measure a magnetic field formed on the inner side of the wall of the pipeline. BACKGROUND OF THE INVENTION Metallic pipelines are often laid in the ground or in water. As a rule, these surroundings represent an electrolytic medium. A charge transport from the metal of the pipeline in the direction of the electrolyte arises at defects in the coating of the pipeline. The pipeline corrodes as a result of the transport of metal ions. To prevent corrosion from developing, the prior art provides for the application of a DC current to the pipelines to be protected. This protective current creates a cathodic polarization of the pipeline and prevents metal ions from being detached from the pipe surface. The corrosion can develop very quickly at the coating defects in the pipeline walls if this so-called cathodic protection fails. Therefore, the cathodic protection is checked at relatively short intervals of one month or a few months. Moreover, such inspections help to find and remedy the coating defects in a timely manner. A hole in a pipeline formed as an oil or gas pipeline, for example, may lead to catastrophic environmental damage. As a rule, the cathodic protection is checked at a few critical measurement points by measuring the installation-ground potential. The appropriate devices are fixedly installed at the measurement locations. Additionally, the potential field at the surface can be measured along the pipeline and in the pipeline surroundings. For offshore pipelines, potential measurements are performed with the aid of remote-controlled underwater vehicles. As a rule, the potential measurement is very expensive and connected with a great manual outlay. A further method for checking the cathodic protection is based on the measurement of the DC current directly in the pipeline wall using an inspection device that is able to pass through the pipeline, which is to say movable within the pipeline, and also referred to as a pig. This approach enables measurements along the entire pipeline and represents a cost-effective, reliable method for estimating the efficiency of the cathodic protection and for detecting coating defects. However, the measurement requires a robust method which can also be used under difficult measurement conditions in a pipeline in the form of an oil pipeline for example. A method known from the prior art for measuring the current intensity using a pig is based on the measurement of potential values in the pipeline wall in front of and behind an inspection device moved through the pipeline in the longitudinal direction of the latter. The currents in the pipeline wall and the potential distribution along the pipeline can be determined from the measured potential difference. However, this approach requires a good galvanic contact with the wall for a reliable measurement. Thus, the pipeline must be cleaned well for the measurement. As a rule, such a measurement is not possible in the case of pipelines with internal coating and/or an oil medium transported in the pipeline. BRIEF SUMMARY OF THE INVENTION It is the object of the present invention to develop a cost-effective and reliable method and an associated inspection device for examining the cathodic protection of a pipeline. In the method according to the invention for examining the cathodic protection of a pipeline, in particular a ferromagnetic pipeline, a primary alternating magnetic field and, accompanying this, a local change in the permeability in the wall of the pipeline is created by means of a magnetizing device of an inspection device moved through the pipeline. At the same time, a secondary DC magnetic field caused by a DC current of the cathodic protection is formed in the wall of the pipeline. Further, a resultant magnetic field which emerges from the superposition of the primary alternating field and the secondary DC magnetic field is measured by means of a measuring device which is moved through the pipeline and comprises at least one magnetic field sensor, said measuring device likewise being part of the inspection device in particular.