Near Field Testing (NFT)
Near Field Testing (NFT) is an electromagnetic inspection technique engineered specifically for the rapid identification of internal diameter (ID) thinning and defects in finned carbon steel tubing, as typically encountered in air-cooled heat exchangers (fin-fan coolers).
NFT employs a specialised probe assembly comprising a transmitter driver coil and a detector coil located in close proximity within the \"near field\" of the driver. The driver generates low-to-medium frequency eddy currents that interact predominantly with the internal surface layer of the ferromagnetic tube. Unlike standard eddy current methods, NFT signals are confined to the inner bore, meaning exterior aluminium fins produce zero background interference.
NFT requires no magnetic saturation units or couplant water supply. It provides exceptional velocity for screening internal erosion, inlet turbulence damage, and pitting in carbon steel fin-fan bundles, furnishing asset managers with rapid condition assessments during brief shutdown windows.
Key Technical Highlights & Capabilities
Zero Fin Interference
Immune to signal noise from external aluminium or copper fins, eliminating false reject indications on fin-fan air coolers.
Internal (ID) Flaw Specialism
Superior sensitivity for detecting internal wall loss, erosion-corrosion pitting, and inlet-end tube degradation.
High-Speed Couplant-Free Operation
Requires no water couplant or heavy electromagnet, permitting continuous pull-through speeds up to 1 m/s.
Turnaround Outage Screening
Delivers swift qualitative defect sorting to isolate compromised tubes for targeted plugging or scheduled retubing.
Require Near Field Testing (NFT) for Your Facility?
Contact our experienced Level III inspection specialists for technical consultation, procedures, or expedited site mobilisation.