In eddy current testing, a coil carrying an AC current is placed close to the specimen surface, or around the specimen. The current in the coil generates circulating eddy currents in the specimen close to the surface and these in turn affect the current in the coil by mutual induction. Flaws and material variations in the specimen affect the strength of the eddy currents.
The presence of flaws etc is therefore measured by electrical changes in the exciting coil. Both voltage and phase changes can be measured, but some simpler instruments measure only the voltage changes.
The strength of the eddy currents produced depends on the:
as well as the presence of flaws, and much of the success of eddy current testing depends on separating the effects of these variables. Most eddy current instruments require calibration on a set of test specimens and the flaw sensitivity can be very high.
Equipments vary from simple portable meter read-out instruments to more complex oscilloscope read-out displaying both phase and voltage; recently the outputs have been digitised to produce fully-automated computer-programmed equipment with monitored outputs for high-speed testing.
Applications vary from crack detection, to the rapid sorting of small components for either flaws, size variations or material variation. Many applications are to bar, tube and wire testing. Metal sorting is also a common application of eddy current testing.
Pulsed Eddy Current
Pulsed Eddy Current testing and inspection give essential information on the actual status of your assets, allowing you to monitor and manage any production or safety issues more quickly and easily than previously. Insulation materials do not need to be removed, and surfaces do not require any special preparation, lowering overall and underwater inspection expenses dramatically. In general, PEC services require substantially less time than conventional methods, allowing for quick and convenient in-operation testing and inspection with no disruption of output.
Pulsed Eddy Current readings taken repeatedly at the same spot can be accurately duplicated, regardless of casing, coatings, or insulation. PEC technology yields data with a plus/minus 10% accuracy for corrosion detection and a plus/minus 0.2% accuracy rate for corrosion mapping.
TUBE INSPECTION EDDY CURRENT
Eddy current testing of tubes is an effective way of assessing the condition and lifespan of tubes, particularly in the power generation, petrochemical, chemical, fertilizer, and air conditioning industries. The technique is applied to detect corrosion, pitting, cracks, erosion, and other changes to both the tube’s interior and exterior surfaces.
It is a high-speed inspection technology, and one of its primary benefits is that it can be used on paint and coatings. The process is only applicable to nonferrous materials like stainless steel, copper, and titanium. We also conduct remote field and magnetic biased eddy current tests on carbon tubing.
Eddy current testing uses electromagnetic induction to detect flaws in tubing. A probe is put into the tube and pushed throughout its full length. The electromagnetic coils in the probe generate eddy currents, which are simultaneously monitored by measuring the probe's electrical impedance. The probe's findings will give details about the tube flaws. The software will record the scanning data and store it as a backup for the future.
