ELECTROMAGNETIC TECHNIQUES LOW FREQUENCY ELECTROMAGNETIC TECHNIQUE

LFET – Low Frequency Electromagnetic Technique for Tube and Pipe Inspection

IRISNDT uses this low frequency electromagnetic technique (LFET) on pipe ranging from NPS 2 to NPS 36, and on flat surfaces. We test outer diameter (OD) ferrous and non-ferrous pipe surfaces to identify inner diameter (ID) corrosion. LFET works more speedily than ultrasonic testing, yet it can detect pitting, and more generalized losses such as flow accelerated corrosion.

IRISNDT APPLIES LFET TO INSPECT

• Piping for corrosion wall losses.
• Tubing for corrosion wall losses, including some finned tubing.
• Piping and tubing with internal coatings.

ADVANTAGES

• A fast and effective screening tool to rapidly detect corrosion losses on piping.
• As a non-contact/couplant free inspection method, LFET can be used to inspect through thin coatings like Yellow Jacket.
• LFET requires little to no surface preparation (though the surface must be relatively smooth).
• Equipment is highly portable and easy to deploy.
• Highly reproducible electronic data for reference/audits and integration into plant software. In-depth defect morphology allows for the prioritization of resources.
• Equipment being inspected can be tested while online.
• High temperature scanners can be used to test equipment over 150 degrees C.
• LFET can reliably identify 30% deep ¼” diameter pits in most pipe sizes.

CONSIDERATIONS

Sensitivity is reduced in thicker materials to an upper limit between ½”- ¾”, depending on material. LFET is typically used as a screening tool with defects sized with ultrasonic testing. Pipe bends generally are not tested as the standard scanners aren’t contoured to navigate them. Insulation and other surface obstructions (heat trace) must be removed to access the area to be inspected.

BFET – Balanced Field Electromagnetic Technique

IRISNDT uses BFET on small diameter welds to detect cracking, lack of fusion, porosity, and other flaws.

IRISNDT APPLIES BFET TO INSPECT

• Piping/tubing
• Compressor bottles
• Socket welds

ADVANTAGES

• Paints/coatings and corrosive products do not impact the flaw signal.
• Up to ⅜” deep subsurface defects can be detected.
• Minimum surface preparation is required.
• A couplant is not needed. Unlike ultrasonics, this is a dry method.
• Examinations can be performed at up to 1 ft./sec.
• Equipment being inspected can be tested while online.
• High temperature probes are available for testing.

LIMITATIONS

BFET is a screening inspection. Its results are not quantifiable. Based on BFET, one cannot easily determine what type of discontinuity is causing an indication.