SpirALL® Magnetic Flux Leakage

Magnetic Flux Leakage

With SpirALL® magnetic flux leakage (SMFL) technology, pipeline owners and operators have an easier and more efficient way to detect crack-like defects in the pipe wall and long seams—including selective seam weld corrosion, hook cracks, lack of fusion, and surface-breaking laminations.

Proven over thousands of kilometers of pipeline, the SMFL tool overcomes the limitations of traditional high resolution magnetic flux leakage (MFL) in characterizing axially oriented defects. That means a more accurate assessment of seam weld anomalies, other longitudinally oriented defects, and even traditional metal loss – all to help you satisfy fiscal, operational requirements.  

Scaled for pipelines ranging from 6 inches to 30 inches in diameter, SMFL technology is included on our Multiple Dataset (MDS) platform.

Best used for: detecting axial planar or crack-like defects in the pipe wall and long seams

Key features:

  • Uses a single, compact magnetizer to create a spiral or oblique magnetic field that provides 100 percent coverage of the pipe wall.
  • Detects axial planar or crack-like defects not detected by axial MFL.
  • As part of the MDS platform, provides comprehensive threat assessment using only one tool in a single inspection run. That reduces inspection time compared to using individual technologies.
  • Able to distinguish attributes of long seam types – electric resistance welded (ERW), electric fusion welded (EFW), double submerged arc welded (DSAW), lap welded.


  • Why can’t axial MFL detect long seam anomalies? Traditional axial MFL technology detects volumetric pipeline anomalies, general corrosion, and wide circumferential flaws. But because its magnetic field is longitudinal, abnormalities that run in parallel with MFL technology go undetected.
  • How does the combination of MFL and SMFL help improve probability of detection, identification, and sizing? Consider the difference between 2D and 3D images. According to SONY, when shooting a 3D image, two lenses are used to capture separate images of the same object from different angles. Containing twice as much information as conventional 2D images, 3D images are then created while maintaining the information from both angles. In a similar way, MFL and SMFL together offer “two lenses” that are used to capture separate images of the same anomaly. Anomalies may be detected in both or either of the technologies depending on the defect geometry – the result offers insight into the actual classification of a detected feature. Additionally, interacting threats such as mechanical damage become readily apparent through utilization of multiple field angles.
  • What is the difference between a crack and a crack-like defect? American Petroleum Institute API 1163 defines a crack as a “very narrow elongated separation caused by mechanical splitting.” Pipeline Operator Forum Version 2009 defines a crack as “a planar, two-dimensional feature with possible displacement of the fracture surfaces.” National Association of Corrosion Engineers NACE 35100 defines a crack, or cracking, as “very narrow elongated defects caused by mechanical splitting into parts.” NACE SP0102-2010 defines a crack, or cracking, as “a fracture type of discontinuity characterized by a sharp tip and high ratio of length to width to opening displacement.”
  • Crack-like defects are those that exhibit characteristics of cracks as defined above, but have enough width to allow detection by MFL-based technology. Crack detection is performed by acoustic technologies, while crack-like defects can be detected by MFL-based technologies.