Eddy current is the most theory-dependent method in NDT. A technician who has memorised a setup procedure without understanding the impedance plane will misread the first unfamiliar signal they meet.
Training covers electromagnetic induction, skin depth and why frequency selection determines what depth is examinable, the impedance plane and how lift-off, conductivity, permeability and defects each move the operating point along characteristic paths, and phase analysis — reading angle and amplitude together, which is the whole skill.
Level I performs examinations to a written instruction with an established setup. Training focuses on probe handling, reference-standard calibration, fill factor in tube work, and recognising when a signal is lift-off rather than a finding.
Level II selects frequency and probe, sets up against reference standards, and interprets and evaluates. This is where tube inspection (bobbin screening with array or rotating probes for prosecution), surface crack detection and coating-thickness work are learned, along with the phase discipline that separates a defect from noise.
Level III approves procedures and qualifies personnel, including technique justification for the material and geometry, and the saturation techniques required where permeability would otherwise swamp the examination.
Under ASNT SNT-TC-1A the employer sets training hours and documented experience hours per method and level in its own Written Practice, so the requirement you must satisfy is your employer's — not a universal number. Under ISO 9712 a central body examines and certifies, and the certificate travels with you between employers. Either way the pattern is the same: classroom or structured theory, supervised practical work, then general, specific and practical examinations. Training hours and experience hours are separate requirements, and candidates most often stall on the experience log rather than the coursework. Start documenting hours before you need them. How employers run the programme · the certification pathway in full.
The practical examination tests calibration on reference standards, correct interpretation of the impedance display, and sizing consistency. Candidates who read amplitude alone fail — two signals of identical height with different phase angles are different things, and the examination is designed to expose exactly that.
ASME Section V Article 8 and its tubing appendices, ISO 15548, ASTM E243 for tube examination.
Aerospace (the dominant surface method for airframe and engine components), heat-exchanger and condenser tube inspection across refining, petrochemical and power, plus conductivity and coating measurement in manufacturing.
Array eddy current and ACFM extend the method to wider coverage and to sizing through coatings. Both build on the same impedance-plane foundation and should follow conventional ET, not replace it. ACFM · the full ET guide.
Programmes are built and taught by practising ASNT Level IIIs. For companies, delivery is on-site at your facility — the practical work uses specimens representative of what your people actually examine, which is the single biggest difference between training that transfers to the job and training that does not. For individuals, scheduled cohorts and blended delivery combine structured theory with supervised practical. We are straightforward about the model: Atlantis does not operate walk-in training centres, and we will tell you when a local provider is the better answer for a single candidate.
It depends on the level and on how quickly you accumulate documented experience hours, which is usually the binding constraint rather than the coursework. A candidate already working under supervision progresses considerably faster than someone starting cold, because the experience accrues while they work.
Yes for Level I — it is designed as an entry point. Level II requires documented Level I experience in the method, so the sequence matters. The Level I route · Level II requirements.
Under SNT-TC-1A, no — employer-based certification lapses when you leave, though your documented experience travels with you and the new employer can certify you against their Written Practice. Under ISO 9712 the certificate is yours. This distinction is worth understanding before choosing a route. The comparison in full.
Next: all NDT training programmes · finding training near you · ask about ET training for your team.
ET certification in the US runs under ASNT SNT-TC-1A, which recommends 40 training hours and 210 ET experience hours for Level I, and 40 further training hours with 630 cumulative ET hours for Level II — the same tier as UT and RT. ASME BPVC Section V Article 8 governs tubular product examination.
Eddy current carries the same 40-hour classroom recommendation as UT and RT because the interpretation is electromagnetic rather than geometric: the technician reads phase angle and amplitude together on the impedance plane, and phase is what separates a through-wall defect from lift-off. SNT-TC-1A's recommended table lists ET Level I at 40 training hours, 210 hours of ET experience and 400 total NDT hours, and ET Level II at 40 further training hours, 630 cumulative ET hours and 1,200 total NDT hours. Test frequency governs what depth is examinable: standard depth of penetration is the depth at which eddy current density falls to about 37 percent of the surface value, and it decreases as frequency, conductivity or permeability rises. US demand concentrates in two places — heat-exchanger and condenser tube inspection across refining, petrochemical and power generation, and aerospace surface and bolt-hole examination under NAS 410.
Source: ASNT SNT-TC-1A (2020 edition); ASME BPVC Section V, Article 8 and its mandatory appendices for tubular products; ISO 15548-1 and ISO 15548-2 (eddy current equipment characteristics); ASTM E243 Standard Practice for Electromagnetic (Eddy Current) Examination of Copper and Copper-Alloy Tubes; NAS 410 for aerospace personnel qualification.
| Technique | Detects | Does not detect | Primary US application |
|---|---|---|---|
| Bobbin coil, tube | Volumetric wall loss, pitting, general thinning and through-wall holes, at full-bundle screening speed | Circumferential cracking, and flaws masked at tubesheets and support plates without supplementary probes | Heat exchanger and condenser screening across refining, petrochemical and power generation |
| Array probe, tube | Axially and circumferentially oriented cracking with positional resolution around the tube circumference | Outer-diameter wall loss in ferromagnetic tube without magnetic saturation | Prosecution of bobbin indications; air cooler and steam generator tubing |
| Rotating pancake coil | Discrete cracks with length and orientation, at the highest spatial resolution of the tube techniques | Full-length coverage at production speed — inspection rate is a fraction of bobbin | Confirmation of bobbin calls; nuclear steam generator tubing |
| Surface and pencil probe | Surface-breaking cracks on non-ferrous, painted and thinly coated components | Subsurface flaws beyond a few standard depths of penetration; anything under thick ferromagnetic material | Aerospace airframe and engine component inspection |
| Bolt-hole probe | Fatigue cracking initiating at fastener holes, with the fastener removed | Cracks masked by an interference-fit bushing without a qualified technique | Aircraft structural inspection to the OEM NDT manual |
| Remote field testing | Wall loss through the full wall of ferromagnetic tube — carbon steel and ferritic stainless | Small, sharp surface-breaking cracks; RFT is a volumetric wall-loss technique | Boiler, feedwater heater and carbon-steel exchanger tubing |
Because ET interpretation is indirect. MT produces a visible indication at the flaw. ET produces a point moving on an impedance plane, and lift-off, conductivity change, permeability change and a real defect each move it along a different path at a different phase angle. Reading amplitude alone fails the practical examination. The classroom hours buy the theory that makes the display legible.
No. Conventional ET, array eddy current, rotating-probe examination and remote field testing are separate sub-methods. The employer's Written Practice names which techniques a certificate covers, and adding one requires documented training plus a practical demonstration on that technique's data. Nuclear steam generator work layers site-specific performance demonstration on top of that.
Frequency sets standard depth of penetration, the depth at which current density falls to about 37 percent of the surface value. Penetration falls as frequency, conductivity or permeability rises, so high frequency buys surface resolution and low frequency buys depth. Tube work adds a second constraint: the frequency that cleanly separates outer-diameter from inner-diameter phase response on the reference standard.
Not with conventional ET alone — permeability variation in ferromagnetic material swamps the defect signal. Two routes exist. Magnetic saturation coils suppress the permeability response and let conventional or array ET work on ferritic tube. Remote field testing operates through the wall instead and measures volumetric wall loss in carbon steel and ferritic stainless tubing directly.
When absolute wall thickness is required, when the tube is ferromagnetic or thick-walled, and when eddy current indications need quantifying. IRIS is an ultrasonic internal rotary technique: slower, requiring clean tubes and water coupling, but it measures thickness rather than inferring it. Standard practice screens the full bundle with eddy current and prosecutes a sample with IRIS.
Aerospace qualifies personnel under NAS 410 rather than SNT-TC-1A alone, with the employer's NDT Level 3 issuing written method approval per person. On top of that, airframe and engine work requires qualification to the OEM's NDT manual procedure for the specific part and technique — bolt-hole, sliding-probe and conductivity examinations each qualify separately.
Tell us the methods and levels you need and how many technicians. We reply with available dates, the delivery options that fit, and what your written practice requires — usually the same working day.
Request a quote / enrol · Employer-sponsored cohorts · info@atlantisndt.com
Training scopes are quoted from the national eddy current testing service: bobbin, array and rotating-probe tube inspection plus surface examination on non-ferrous and coated components.