MTM-G: Magnetic Gradient Tomography Method - Anomaly Detection and Pipeline Integrity Evaluation

A non-destructive testing (NDT) solution for anomaly detection, technical examination, and evaluation of pipeline integrity. MTM-G can be used to inspect above ground, underground, and offshore pipelines of all types and sizes.

MTM-G Principle

MTM-G is based on the Villari effect, which is the change in magnetization of a ferromagnetic metal when it is subjected to mechanical deformation or stress. MTM-G uses a portable magnetometer to scan the pipeline and measure the magnetic field. The changes in the magnetic field are then used to identify anomalies and stress concentrations in the pipe.

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Advantages of MTM-G

  • No Blind Spots MTM-G can inspect the entire length of a pipeline, even around bends and turns.
  • No interruptions MTM-G can be used to inspect pipelines without interrupting their operation.
  • No special preparations MTM-G does not require any special preparations of the pipeline, such as cleaning or depressurization.
  • Detects all types of anomalies MTM-G can detect all types of anomalies inside and outside of the pipe, including metal loss, corrosion, and cracks.
  • Identifies stress concentrations MTM-G can identify stress concentrations in the pipe, which are areas that are more likely to fail.
  • Accurate and reliable MTM-G has been shown to be accurate and reliable, with a 90-97% correspondence with conventional NDT methods.
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Scanning and Calibration

  1. The pipeline axis position is determined under the ground surface.
  2. The pipeline is scanned using a portable magnetometer that automatically records magnetic data and GPS tracks.
  3. The data is preliminary processed and reviewed for quality.
  4. If the data quality is not acceptable, the pipeline is rescanned.
  5. A final report is prepared that includes a list of dangerous (anomalous) areas of the pipeline, matched with the map and having their respective danger degree reported.
MTM-G Subsea

Subsea MTM-G

The Subsea MTM-G is a variant of the MTM-G that is designed for inspecting underwater pipelines. The Subsea MTM-G can inspect pipelines up to 1500 meters deep and can detect metal anomalies such as metal loss, corrosion, and cracks.

Additional analytical and integrity assessment capabilities can be gained by applying a seismic activity map used together with MTM-G anomaly map.

This technology can be used to inspect offshore pipelines along their entire span with POD > 80%.

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MTM-G Requirements and Limitations

  • 25D to 30D Maximum inspection distance between pipe axis and magnetometer
  • No Limit No minimum nor maximum limit for pressure.
  • 50mm 50mm is the minimum diameter of the pipeline. No maximum limit.
  • 2.8mm 2.8mm is the minimum wall thickness. No maximum limit.
  • Any Length No limitations on the length of the pipeline section being inspected.
  • 1m A clear path is required for an operator to be able to walk above the pipeline. Minimum width is 1m.