What Is Tube ECT?
Tube Eddy Current Testing uses a bobbin probe — a multi-coil electromagnetic sensor — pulled
through the bore of a tube at controlled speed. The probe induces eddy currents in the tube wall
and measures the electromagnetic response. Wall loss, pitting, cracking, and support plate wear
alter the eddy current signal in characteristic ways that a qualified analyst interprets to identify
and quantify defect type, severity, and location.
Multi-frequency ECT uses simultaneous acquisition at multiple test frequencies — enabling
differential analysis that suppresses the signal from tube support plates and allows defect signals
beneath supports to be evaluated. This is particularly important in heat exchangers where baffle
plate and support plate corrosion zones are often the most critical defect locations.
Applicable tube materials: Copper alloys (admiralty brass, Cu-Ni 70/30 and 90/10), titanium,
austenitic stainless steel, Inconel, and other non-ferrous, non-magnetic alloys. For ferrous
(carbon steel) tubes, RFET or IRIS is the appropriate technique — see those pages.
ECT can detect and quantify:
- General wall thinning and pitting — top-side, bottom-side, and through-wall
- Stress corrosion cracking (SCC) and intergranular attack (IGA)
- Erosion and impingement damage at inlet zones
- Baffle cut wear at support plate locations
- Tube-end degradation and crevice corrosion