Ferrous materials have always been a challenge for eddy current. Until now.
The innovative design of Sharck probes* is capable of addressing the inspection needs of several industries that rely heavily on carbon steel welds, such as the oil and gas (onshore and offshore), wind power, and structural industries.
The Sharck probe is a new type of ECA probe. It is based on tangential ECA (TECA™) technology, which was specifically developed for cracking in carbon steel. This probe is not only capable of measuring crack position and length, but also of sizing cracks as deep as 7 mm (0.28 in). All this without surface preparation and paint removal.
Benefit 1 — Advanced Array Technology
• Based on tangential eddy current array
• Fast — Maximum scan speed of 200 mm/s
• Single-pass detection of longitudinal and transverse cracks
• Wide coverage — Simultaneously scan weld cap, toe area, and heat-affected zone
• High-performance multiplexing for optimal sensitivity
• Reliable, less operator dependent compared to alternatives
Benefit 2 — Advanced Software
• Easy interpretation with intuitive encoded 2D/3D C-scans
• Actual crack depth measurements — Not based on theoretical modelling
• Automatic readings — Crack length and depth, liftoff
• Auto-compensation — Live monitoring of liftoff and permeability variations
• Full data recording and archiving capabilities
Benefit 3 — In Line With Recognized Eddy Current Certifications and Standards
Sharck probes return signals similar to conventional eddy current testing signals, making the technology easy to learn. Sharck probes also comply with ASTM E3052.
How Does it Work?
Traditional pancake coil axes are perpendicular to the surface under test. The patent-pending Sharck probe, on the other hand, incorporates the tangential ECA (TECA™) technology where tangential coils are positioned on their sides, their central axes parallel to the surface. Tangential also means that eddy currents flow parallel to the surface and are capable of “diving” under cracks to measure their depth.
Each finger in Sharck probes contains three coils. Two are tangential, working in a transmit-receive mode. Using several small coil arrangements yields great resolution, while multiplexing channels over many fingers provides a large, uniform eddy current distribution for optimal sensitivity. The third coil is a pancake coil used to monitor crack position and detect transverse cracks.
While tangential eddy current is not an entirely new concept, it has never before been used in an array technique with high-performance multiplexing. One key advantage of TECA is that it offers signals similar to traditional ECT pencil probe signals, making TECA easy to learn, minimizing the ramp-up time, while still being a more information-rich technique.
TECA offers extremely valuable information:
• An almost flat liftoff signal
• Crack-like indications approximately 90° relative to the liftoff signal
• All crack-like indications feature the same phase shift
This has several major benefits, one being the capability of monitoring liftoff — unlike orthogonal coils that simply cancel the liftoff signal.
Obviously, the vertical amplitude of a given indication is impacted by liftoff. But thanks to a coil design capable of monitoring liftoff, the Sharck probe can compensate, offering accurate depth measurements.