Zetec puts a fresh twist on flexible ECA probes
Eddy current array (ECA) technology has long been used for nondestructive testing in aerospace, power generation, oil and gas, and other industrial applications. It’s a fast, accurate, chemical-free method for detecting surface and sub-surface indications including cracks, pits, corrosion, and damage due to temperature or fatigue.
ECA has the added benefit of generating an electronic inspection record for advanced analysis and reporting, a big advantage over dye penetrant testing (PT), magnetic particle testing (MT), and other types of manual examinations. Unlike PT or MT, ECA results can be saved, shared, stored, processed, and compared at any time. Indeed, with the right probe, software, and instrument, an operator can set up an inspection quickly, capture more information in a single pass, see results instantly on a C-scan display, and dramatically increase the speed and reliability of the test.
Closeness Counts
For an ECA test to be accurate, the excitation coils need to be close to the material. It’s a challenge when you’re dealing with complex geometries, different weld shapes and materials, rough surface conditions, and inspection areas that are hard to reach.
Consider a circumferential butt weld joint on a pipe, where the positive curvature of the pipe exterior, the positive curvature of the circumferential weld crown bead, and the negative curvature of the joining area at the toe of the weld intersect. It’s a good example of a complex geometry: the joint between the weld and the base material is difficult for an eddy current probe to reach because of the planar nature of typical array assemblies. In addition, the weld itself is a non-uniform surface.
So you need a probe design that helps the operator keep the excitation coils and sensing devices closely and properly aligned with the surface of the material.
Fresh Approach
Customized and flexible surface array probes can quickly and accurately test a wide range of materials and geometries but you have to replace the whole assembly if one element of the probe wears out or fails.
One new approach to improving the versatility and service life of ECA probes is a modular one. In 2019, Zetec introduced its Surf-X flexible ECA probe with swappable coil sets for specific applications. Each probe is comprised of an electronics module and detachable encoder that can be used interchangeably with different Surf-X array probe coil set. Users in the field can switch out a coil set in less than a minute.
Zetec offers a growing range of coil sets, including a coil set for butt or t-welds uses a mix of array coils for the weld crown and heat affected zone and two +point coils for the weld crown; a coil set for testing rows of rivets on an airplane skins; and another coil set for testing for far side flaws on thick sheets of aluminum. There are also multiple tape probe coil sets that find surface flaws on complex geometries. The encoder can connect in multiple locations on both the handle and electronics module. As Zetec introduces additional coil sets in the future, the Surf-X module, encoder, and cables can be re-used, improving the return on investment.
Zetec offers Surf-X coil sets with three wear-surface options: no wear surface for inspecting small indications on smooth materials; a cloth wear surface for protecting the array coils on smooth or polished surfaces, like airplane skins; and SuperFabric for protecting array coils on rough surfaces like butt and t-welds.
More Coverage and Versatility
Regardless of whether you use a custom probe shape, a flexible surface array probe, or a modular approach like Surf-X, today’s ECA probes are simpler to use and provide greater inspection coverage in a fraction of the time compared to PT, MT, or pencil probes.
The key is to focus on a probe’s flexibility—literally, in terms of the surfaces and geometries it can handle, and in its ability to help technicians be more productive in their inspections while maximizing the value, versatility, signal quality, and service life of the probe.
