Pipeline Technology Conference 2020, Berlin

Dents are among the most critical anomalies threatening pipeline integrity, as they induce plastic deformation and alter the magnetic properties of steel. Skipper NDT conducted an experimental study to evaluate the influence of dent depth on residual magnetic signals using Large Stand-Off Magnetometry (LSM) technology. The goal was to enhance the detection and characterization of dents during non-contact inspections.

Tests were performed on X42 steel pipes (168 mm diameter, 7 mm wall thickness) with dents of 5%, 10%, and 15% depth. Mechanical behavior was simulated using finite element modeling (Ansys) to predict stress distribution and validate strain gauge measurements. Magnetic properties were recorded before and after denting using high-resolution fluxgate magnetometers on a proprietary non-magnetic test bench.

Key Findings:

• Magnetic signal intensity increases with dent depth, enabling correlation between magnetic anomalies and defect severity.

• Even shallow dents (5%) produce detectable magnetic variations.

• Stress distribution around dents is complex, confirming the need for advanced signal processing and machine learning for accurate characterization.