Near Field Array Tube Inspection

Near Field Array (NFA) tube testing is an electromagnetic testing method for detecting discontinuities on the internal surface of fin-fan type tubes and ferromagnetic (Carbon steel) heat exchanger tubes.
NFA – Near field Array testing uses an array of coils (up to 30 coils) that activate in sequences, similar to ECA – Eddy current array testing. Unlike traditional Eddy current testing, which only uses a bobbin coil, NFA – Near field Array testing includes tangential coils that help gather detailed data and discontinuities in all directions.The most efficient test method for examining Aluminum finned carbon steel tubes is NFA – Near field Array tube testing. Because the external aluminium fins interfere with the quality of the signals acquired, aluminium finned carbon steel tubes are the most difficult to check. Internal pitting, internal cracks at the tubesheet, internal erosion, and the resulting wall loss can all be detected with NFA – Near field Array tube testing, which can also discriminate the location and size of discontinuities.For signal analysis and reporting,
This NFA method is:
Fast, Accurate, Traceable, and Archivable a digital paper trail
LMATS employs Eddyfi's Magnifi software. The software allows NFA – Near field Array tube testing data to be shown and reported in 2D and 3D 'C' scan formats, which can help asset owners make informed decisions based on the accurate position and precision of the discontinuity.

Ideal Applications:

• Most ideal for efficient and reliable inspection of Aluminum finned tubes and ferromagnetic heat exchangers
• NFA – Near field Array tube testing is ideal for inspecting tubes in the range of 19.05mm to 38.10mm diameter
• NFA – Near field Array tube testing is ideal for detecting internal diameter discontinuities such as pitting, cracks at tube sheet, erosion and wall loss on finned heat exchanger ferromagnetic tubes.

• Advantages:

  • NFA – Near field Array tube testing can provide 2D and 3D ‘C’ scan images to assist the asset owner to locate exact location of the discontinuity and its precise size
  • NFA – Near field Array tube testing can precisely measure volumetric discontinuities of approximately 3mm in a single pass
  • NFA – Near field Array tube testing can detect both axial and circumferential cracks
  • NFA – Near field Array tube testing can be performed comfortably at 6meters per minutes enabling to reduce downtime of the heat exchanger maintenance
  • NFA – Near field Array tube testing does not use magnets and hence the pull speed does not affect the sensitivity s compared to MFL -Magnetic flux leakage technique
  • NFA – Near field Array tube testing does not use water (Unlike IRIS – Internal Rotary Inspection System) and hence post cleaning and drying is not required minimizing the risk of water contamination pitting.