ACFM (Alternating Current Field Measurement) is an electromagnetic technique for detecting and sizing surface breaking cracks in metallic components and welds. It combines the benefits of the alternating current potential drop (ACPD) and Eddy Current Testing (ECT) techniques in terms of defect sizing without calibration and the ability to work without electrical contact.

The ACFM probe introduces an electric current into the part locally and measures the associated electromagnetic fields near the surface. When a defect is present, the associated fields are disrupted, and the information is graphically presented to the system operator. The ends of a defect are easily identified, revealing information about the defect’s location and length. The extent of the flaw in the wall plays an important role in determining structural integrity, and it is calculated using mathematical computation, allowing for an immediate evaluation of the indication’s implication.

Advantages

• Applicable for base material or welds, ferritic or non-ferritic conductive metals.
• Can be used on hot surfaces, underwater, or in irradiated environments.
• Provides both depth and length information.
• Accurate sizing of defects up to 25mm in depth.
• Requires minimal surface preparation and can be applied over paint and other coatings.
• Applicable for under water inspection as well as normal inspection.
• Inspection data can be stored and analysed offline.