A Magnetic Flux Leakage (MFL) pig is the most widely used inline inspection (ILI) tool for detecting metal loss, corrosion, and wall thinning in pipelines.

A Magnetic Flux Leakage (MFL) pig is the most widely used inline inspection (ILI) tool for detecting metal loss, corrosion, and wall thinning in pipelines. MFL pigs magnetize the pipe wall to saturation level as they travel through the pipeline — any wall thickness reduction causes magnetic flux to leak outward, which is detected by Hall-effect sensors on the pig body.

MFL pigs detect external and internal metal loss, general corrosion, pitting, and certain types of mechanical damage. Advanced MFL tools offer high-resolution (HR-MFL) and extra-high-resolution (XHR-MFL) capabilities for detecting smaller defects with greater accuracy.

MFL pig inspections require piggable pipelines with launching/receiving facilities, consistent diameter, and sufficient product flow. For unpiggable pipelines, EMPIT’s CMI technology provides an aboveground magnetometry-based alternative that detects corrosion and metal loss from the surface — using related magnetic principles without requiring internal access.