Alternating Current Field Measurement

Offshore platform setup requiring ACFM Inspection

Alternating Current Field Measurement (ACFM) is utilized to detect and size surface breaking cracks and discontinuities. A benefit of Alternating Current Field Measurement (ACFM) is that it can be utilized on coated surfaces which are strictly adhered to the surface. ACFM can also identify material thickness, electrical conductivity, and resistance due to material discontinuities. Pre-cleaning is not typically a necessity in most cases with ACFM, as inspections may still be performed with minor surface rust, dust, and debris. This causes for a quicker inspection time. Oil and gas industries utilize this test method in off shore platform setups as ACFM can be utilized in situations of high temperatures. ACFM is widely used for in-service inspections and as an alternative to the Magnetic Particle or Dye Penetrant test methods. Commonly used for inspecting things such as cranes and bridges, this test method can also be utilized underwater. This is essential when inspecting things like ship hulls without the use of a dry-dock. ACFM was derived from the methods used in eddy-current and can be used on all metals, whether they are ferrous or non-ferrous. Through ACFM, an alternating current is induced and a magnetic field is detected in the resulting current near the surface.