Eddy current arrays (ECA) are the natural extension of ECT. ECAs are composed of arrays of coils that activate in sequences intended to eliminate interference between them. The array slides on top of surfaces, offering an overall wider coverage and better sensitivity to defects than conventional ECT. ECA technology can detect surface-breaking defects and, to some extent, subsurface defects. ECA probes can also be shaped to match more “exotic” geometries, which enable single-pass scanning of geometries that traditionally pose serious challenges to other inspection technologies.

ECA technology is used as an alternative to other surface inspection technologies in such industries as the oil, gas, and petrochemical industry; the power generation and nuclear industries; the aerospace industry; and the heavy equipment and mining industries. ECAs also very successfully supplement ultrasonic testing (UT) and phased-array UT because these suffer from what is often referred to as a “dead zone” near the surface, making it difficult for them to detect near-surface defects.

Therefore, surface applications of ECA technology are numerous, ranging from weld inspection on pressure vessels and pipes, to corrosion mapping between wing longerons and skin, by way of dovetail inspection in turbines.

Use Eddyfi’s ECA solutions to detect and characterize such common defects as:

  • Far-surface corrosion
  • Subsurface defects such as cracks, voids, and porosity
  • Surface-breaking defects such as cracks and pits
  • Corrosion under insulation (CUI)

Here are some of the flagship surface applications where our ECA solutions — standard or custom — were used with great success to detect defects.

Welds

Welds are used almost everywhere and are subjected to various stresses, making them a focal point for inspection, as they are often critical to structural integrity and safety. Welds can develop surface-breaking cracks and other types of discontinuities that must be detected and characterized.

Eddyfi’s ECA solutions are available for various types of weld materials (ferromagnetic or not), surface conditions (dirty, coated, abrasive), and weld shapes (different degrees of flexibility) to match the shape of the weld crown. Our ECA solutions can also cover all weld areas in a single pass — the heat-affected zone, the toe, and the cap.

The Sharck probe, incorporating tangential eddy current array (TECA) technology, was specifically designed to inspect welds.

Corrosion

Corrosion degrades the useful properties of materials and structures including strength and permeability, so it’s critical to detect it. Corrosion can be concentrated, forming pits and cracks, and it can also extend across wide areas more or less uniformly on exposed surfaces. Some corrosion mechanisms are less visible and less predictable. Our ECA surface probes are designed to detect these various forms of corrosion.

Corrosion Under Insulation

CUI is one of the most difficult processes to prevent because no matter the precautions taken, water invariably seeps into the insulation and begins its dirty work—sometimes unseen until process leakage occurs. Historical data shows that about 60% of pipe leaks are caused by CUI. The price of this is astronomical. The Eddyfi Lyft solution is specifically designed to address this plague of an issue.

Turbines

Turbines are typically found in aircraft and power plants. Moving fluids act on turbine blades to impart rotational energy to the rotor. Gas, steam, and water turbines found in the power generation and nuclear industries usually have a casing around the blades containing and controlling the working fluid.

Turbines are therefore mission critical. Modern turbines are large, complex, and costly to shut down. Safety and life extension programs demand that turbines be inspected regularly. Eddyfi’s ECA surface solutions are designed to perform fast and accurate inspections of various turbine components such as:

  • Dovetails
  • Blades (leading edge, gas path, root)
  • Generator slots
  • Retaining rings
  • Rotor bores
  • Boreholes

Technology Comparison for Surface Applications

When it comes to surface applications, the performance of any given inspection technique depends greatly on the specific conditions — mostly the types of materials and defects, but also surface conditions, cleanliness, etc. However, in most situations, the following are true:

  Liquid penetrant (PT) Magnetic particles (MT) ECT ECA / TECA™
Effective on coatings/paints No Yes Yes Yes
Computerized record keeping No No Partial Yes
3D/Advanced imaging No No No Yes
User dependence High High High Low
Speed Very low Very low Low Very high
Cleaning Yes Yes Application-specific Application-specific
Post-inspection analysis No No No Yes
Chemicals/Consumables Yes Yes No No

If our standard line of ECA surface probes doesn’t meet the specifications of your surface inspection application, we have all the necessary expertise and manufacturing capabilities to develop custom probes to address specific geometries and applications.