Eddy current array (ECA) technology uses several individual coils grouped together in one assembly. So, in essence, ECA is supercharged eddy current testing (ECT).

How it Works

An eddy current array, in its simplest form, is a series of single elements arranged in a row, allowing users to cover a larger area in a single pass than conventional, single-coil probes (i.e., pencil probes using ECT). However, this could lead to suboptimal results. That’s why ECA probes use multiplexing.

Multiplexing involves activating and deactivating coils in specific sequences to leverage the probe’s width. Multiplexing also minimizes the interference between coils in close proximity (mutual inductance) and maximizes the resolution of the probe.

ECA probes effectively eliminate the raster scanning necessary when using ECT pencil probes. This has a significant impact on inspection speeds.

Benefits

ECA is a major improvement over single-element ECT because:

  • Faster inspections
  • Wider coverage
  • Less operator dependent — eddy current array probes yield more consistent results compared to manual raster scans
  • Better detection capabilities
  • Easier analysis because of simpler scan patterns
  • Improved positioning and sizing because of encoded data
  • Eddy current array probes can easily be designed to be flexible or shaped to specifications, making hard-to-reach areas easier to inspect

Tubing Applications

Detection Capabilities According to Defect Type in Tubing

Defect/Tech ECT ECA IRIS RFT NFT NFA MFL PSEC
ID pitting

Excellent

Excellent

Excellent

Acceptable, but limited

Acceptable, but limited

Excellent

Excellent

Excellent

OD pitting

Excellent

Excellent

Excellent

Acceptable, but limited

Not suitable 

Not suitable

Acceptable, but limited 

Acceptable, but limited 

Axial cracking

Acceptable, but limited

Excellent

Not suitable

Acceptable, but limited

Acceptable, but limited

Acceptable, but limited

Not suitable

Acceptable, but limited

Circumferential cracking

Acceptable, but limited

Excellent

Not suitable

Not suitable

Not suitable

Acceptable, but limited

Acceptable, but limited

Acceptable, but limited

ID corrosion

Excellent

Excellent

Excellent

Excellent

Excellent

Excellent

Excellent

Excellent

OD corrosion

Excellent

Excellent

Excellent

Excellent

Not suitable

Not suitable

Acceptable, but limited

Acceptable, but limited

At tubesheet

Acceptable, but limited

Excellent

Excellent

Acceptable, but limited

Not suitable

Not suitable

Acceptable, but limited

Acceptable, but limited

Excellent

Acceptable, but limited

Not suitable

Sizing Capabilities According to Defect Type in Tubing

Defect/Tech ECT ECA IRIS RFT NFT NFA MFL PSEC
ID pitting

Good

Excellent

Excellent

Good

Not suitable

Excellent

Not suitable

Not suitable

OD pitting

Excellent

Excellent

Excellent

Good

Not suitable 

Not suitable

Not suitable 

Not suitable

Axial cracking

Good

Excellent

Not suitable

Not suitable

Not suitable

Good

Not suitable

Not suitable

Circumferential cracking

Not suitable

Excellent

Not suitable

Not suitable

Not suitable

Good

Not suitable

Not suitable

ID corrosion

Good

Excellent

Excellent

Excellent

Not suitable

Excellent

Not suitable

Not suitable

OD corrosion

Excellent

Excellent

Excellent

Excellent

Not suitable

Not suitable

Not suitable

Not suitable

At tubesheet

Good

Good

Excellent

Not suitable

Not suitable

Not suitable

Not suitable

Not suitable

Excellent

Good

Not suitable

Suitability According to Tubing Material

Material/Tech ECT ECA IRIS RFT NFT NFA MFL PSEC
Non-ferromagnetic Tube

Yes

Yes

Yes

No

No

No

No

No

Integral finned tube

Yes

Yes

Yes

No

No

No

No

No

Low ferromagnetic Tube

No

No

Yes

Yes

Yes

Yes

Yes

Yes

Integral finned tube

No

No

Yes

Yes

Yes

Yes

Yes

Yes

Ferromagnetic Tube

No

No

Yes

Yes

Yes

Yes

Yes

Yes

Integral finned tube

No

No

Limited

Yes

Yes

Yes

Yes

Yes

Aluminum finned tube

No

No

Yes

No

Yes

Yes

Yes

Yes

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
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