Alternating Current Field Measurement ACFM
ACFM is used for in-service inspection as an alternative to MT / PT. ACFM is ideal for detecting cracks in welds, through coatings and with less extensive cleaning. In addition, it can be used to estimate crack depths.
- Through coatings including: paint, epoxy coatings, oxide layers, fire protection layers and marine growth
- Piping, Pressure vessels, pipelines, and drillpipe, structural supports in petrochemical facilities
- Pipe for ovality deviations
- And size growing fatigue cracks in –in service pressure vessels.
- Equipment operating at temperatures as high as 500 ⁰C
- During welding without having to allow each bead to cool down and without subsequent reheating
- Wind turbines
- As a non-contact inspection method, ACFM can be used to inspect through coatings of various thickness (including dirt), saving on coating removal and reapplication costs
- Equipment is highly portable, easy to deploy through rope access
- High temperature applications allow for in-service inspections, avoiding the cost of equipment shutdown
- Highly reproducible electronic data for reference/audits and integration into plant software
- In-depth defect morphology allows for prioritization of resources
- ACFM sizing models currently only sizes accurately crack depths in steel. The length assessment is not greatly affected in any material. When sizing cracks in other materials, a calibration chart is needed based on defects of known depth. The chart can then be used to convert the ACFM indicated depths into true depths
- ACFM sizing models be readily applied to cracks with a simple morphology (fatigue); they are less suitable for networks of branched cracks (stress corrosion cracking)
Alternating Current Field Measurement uses electromagnetic fields to identify and size cracks (length and depth). This non-destructive non-contact examination method uses a uniform electric current which is induced into the material under test; the magnetic field generated is disturbed if a discontinuity is present and flows around the defect’s edges. Special techniques are used to induce these electric currents and the components used are built into the ACFM probes. ACFM can be used when inspecting carbon steels, stainless steels, duplex, titanium, Inconel, bronze and aluminum.