Advancing Eddy Current Inspections with Voliro’s Drone-Enabled PEC Technology

Voliro’s drone-enabled Pulsed Eddy Current (PEC) technology, developed with Sixpec, enhances non-destructive testing by enabling accurate, efficient inspections of hard-to-reach, insulated metal structures without direct contact, while addressing limitations of traditional eddy current testing methods.

By emitting short, high-energy electromagnetic pulses, PEC systems can penetrate coatings and insulation to identify hidden corrosion or metal loss without direct contact.

Tested at a Tupras refinery, Voliro’s PEC-equipped drones demonstrated the ability to detect early-stage CUI through up to 100 mm of insulation. The integration of the lightweight, second-generation Sixpec® module onto the Voliro T drone supports inspections in hard-to-reach areas. 

While this reduces the need for scaffolding or invasive preparatory work, certain conditions, such as surface coatings or electromagnetic interference, may still require preparatory steps to maintain measurement accuracy.

Understanding Eddy Current Testing (ECT)

Eddy Current Testing (ECT) is a non-destructive method used to identify flaws such as cracks, corrosion, and thickness loss in conductive materials. It operates on the principle of electromagnetic induction, where an alternating current generates eddy currents in a conductive surface. Variations in these currents can indicate potential defects.

Modern ECT techniques, including high-frequency eddy currents, pulsed eddy current testing, and eddy current arrays, improve sensitivity and inspection efficiency. Digital signal processing methods, such as Wavelet Transform and Fourier Transform, enhance the signal-to-noise ratio and resolution. Some systems rely on computer vision models, including neural networks, to assist in detecting and classifying flaws.

Applications of Eddy Current Testing

ECT is used for detecting surface and near-surface defects, measuring material thickness, and inspecting welds and tubing. Inspections are typically recommended every 3 to 5 years for critical assets. Including ECT in annual inspection schedules can support maintenance planning and help reduce the risk of unplanned downtime.

Advantages and Limitations of ECT

Advantages:

• Sensitive to surface and near-surface changes, voids, or defects
• Allows for non-contact inspections with minimal prep time needed
• Adjustable for various material thicknesses through controlled eddy current penetration
• Provides immediate results with visual reporting for follow-up actions
• Does not use chemical penetrants or gamma rays, which could potentially harm workers, making it eco friendly

Limitations:

• Applicable only to conductive materials like metals (aluminum, copper, titanium, gold), alloys (stainless steel, invar, cupronickel), graphite, and carbon structures)
• Limited depth penetration, which restricts the detection of deep subsurface flaws
• Surface conditions, such as roughness, coatings, or paint, can affect test accuracy
• Test accuracy is influenced by the operator’s technical expertise and environmental factors, such as temperature fluctuations and mechanical vibrations

Voliro’s Drone-Mounted ECT Solutions

Traditionally, ECT required close-proximity manual inspections. Voliro offers drone-mounted ECT probes, including the PEC system, to conduct inspections of hard-to-reach assets, such as insulated pipes and storage tanks, without direct contact. Certain inspection environments may still require considerations, such as mitigating electromagnetic interference or preparing surfaces for optimal probe performance.

The Voliro T drone, equipped with the Sixpec module, can perform inspections through wall thicknesses of 3 to 18 mm and at lift-off distances up to 100 mm. This approach can reduce downtime, improve safety, and increase inspection efficiency while maintaining measurement accuracy.

Recommended Eddy Current Testing Instruments

The most basic eddy current test requires an ammeter or voltmeter to measure voltage changes, a wire coil, and an alternating current source.

However, the instruments for industrial use are more sophisticated and have five standard components:

• Oscillator, providing alternating current to the test coil at different frequencies, typically between 100 Hz to 6 MHz.
• Coil assembly — a single or multi-current probe used to induce eddy currents into the expected material.
• Bridge circuits process and display signals resulting from changes in eddy current magnitude and distribution.
• Signal processing circuits convert readings into digital format and perform noise filtering.
• Output display shows results as meter readings, diagrams, and visuals.

All of these elements are condensed into compact handheld or remotely operated devices used for multiple types of inspections.

Performing Eddy Current Testing with Voliro

Eddy current testing is a versatile method for assessing conductive structures for signs of corrosion, thickness loss, or wear and tear.

Voliro’s drone-enabled ECT solutions support inspections at heights and in confined spaces. By reducing the need for scaffolding or rope access, these technologies help minimize asset downtime and operational disruptions. The accuracy of inspections depends on factors such as probe configuration, operator expertise, and specific environmental conditions.