Eddy Current Testing (ET)
Couplant-free electromagnetic examination of conductive components for surface and near-surface indications.
Eddy current testing (ET) uses electromagnetic induction to evaluate suitable conductive oilfield components for surface and near-surface conditions. An alternating current in a probe coil generates a varying magnetic field, which induces circulating eddy currents in the part. Where a discontinuity disrupts those currents, the change appears as a shift in the coil’s impedance that the instrument displays for interpretation.
ET does not require couplant, although material, geometry, coatings, scale, surface condition, probe lift-off, and probe access can affect applicability and signal quality. It is sensitive to surface and near-surface conditions and provides indications during scanning. Two things define a sound ET inspection: choosing the probe and frequency appropriate to the material and geometry, and calibrating against a reference standard so indications can be evaluated against a repeatable baseline.
How eddy current signals are produced
Common ET applications
- Surface and near-surface examination of suitable conductive oilfield components
- Inspection of accessible machined surfaces where probe geometry permits
- Examination where a couplant-free electromagnetic method is advantageous
- Component-specific inspection performed under an approved procedure and calibration setup
Why calibration and probe selection matter
The ET signal is shaped by the probe geometry, frequency, material conductivity and permeability, surface contour, and probe-to-surface spacing. A calibration that does not match the part produces indications that are not meaningful, and an unsuitable probe may not detect the condition of concern. Each job starts with a probe and frequency appropriate to the material and the condition of interest, verified against a reference standard before scanning.
Benefits and limitations
Can identify
- Couplant-free electromagnetic inspection of conductive components
- Sensitive to surface and near-surface conditions
- Real-time indications during scanning
- Applicable where a couplant-free method is advantageous
Does not directly establish
- Only electrically conductive materials
- Surface and near-surface examination only; not a volumetric method
- Sensitive to geometry, edge effects, and lift-off; interpretation requires care
- Probe and frequency must be appropriate to the part and the condition of interest
- Best where the geometry can be scanned with a suitable probe
When to schedule
- Before redeployment of conductive machined components
- After machining, repair, or welding of conductive parts
- When near-surface indications are suspected on a conductive surface
- Before returning repaired conductive equipment to service
- As part of a recurring customer inspection program
Reporting and customer experience
Depending on the method and scope, inspection documentation may include equipment identification, inspected areas, probe and frequency settings, calibration reference, and relevant indications by location. Where connected to the customer account and inspection workflow, results may be made available through Basin’s customer-facing reporting platform.
If you need to evaluate conductive machined components for surface or near-surface indications using a couplant-free method, we’ll scope an ET inspection with the appropriate probe, frequency, and calibration for the part and applicable acceptance criteria.
Request This ServiceTypical Applications
- Surface and near-surface examination of suitable conductive oilfield components
- Inspection of accessible machined surfaces where probe geometry permits
- Examination where a couplant-free electromagnetic method is advantageous
- Component-specific inspection under an approved procedure and calibration setup
Inspection Basis
Inspections are performed using applicable Basin procedures, customer requirements, and project-specific acceptance criteria. Contact Basin NDT to confirm the inspection basis for your equipment and scope.
What You Receive
Depending on the method and scope, inspection documentation may include equipment identification, inspected areas, probe and frequency settings, calibration reference, and relevant indications by location.
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