ACFM is used for detecting and sizing surface breaking flaws. ACFM is also applied to structure both in and out of the water (It has the advantage that the structure requires minimal cleaning and that it can be applied over paint and other coatings up to several millimeters in thickness).
How it works:
ACFM is an electromagnetic technique. A sensor probe is placed on the surface to be inspected and an alternating current is induced into the surface. When no defects are present the alternating current t produces a uniform magnetic field above the surface. Any defect present will perturb the current, forcing it to flow around and underneath the defect; this causes the magnetic field to become non-uniform and sensors in the ACFM probe measure these se field variations.
ACFM is particularly suited to the detection and sizing of fatigue cracks at the toes of welds, including all butt, fillet, node and nozzle welds.
ACFM to inspect fillet welds in Mobile Offshore Drilling Units
(MODUs) to detect any possible original fabrication hydrogen cracking present at weld toes.
It has also been successfully deployed in the laboratory in a joint industry project to detect stress corrosion cracking in duplex stainless steel pipe welds.
- Offshore cranes
- Storage tanks floor & roof ‘lap’ joints
- Storage tank annular welds internal & external
- Vessel nozzles
The main technical advantages of ACFM are:
- The ability to detect defects through several millimeters of coating.
- Works equally well on plain material or welds, ferritic or non – ferritic metals.Can be used on hot surfaces, underwater, or in irradiated environments.
- Provides both depth and length information. Defects up to 25mm (1″) in depth can be sized accurately.
- Rope access and ROV deployed Real time evaluation of the weld area.
- ACFM products are accepted by leading Approval and Standards bodies.