UT Level I: the Scope, the Hours and the Examinations

What a Level I is allowed to do, and what it is not

The Level I definition in SNT-TC-1A is precise and worth reading literally. A Level I is qualified to perform specific calibrations, specific tests and specific evaluations for acceptance or rejection determined by written instructions, and to record results — all under the direction of qualified higher-level personnel. Every constraining word in that sentence carries weight. Specific means the task is named in advance. Written instructions means someone else decided the technique. Under the direction of means a Level II or III owns the outcome.

The confusion arises around the phrase 'evaluations for acceptance or rejection'. It does not mean a Level I evaluates. It means the Level I may apply a criterion that has already been reduced to a written instruction — for example, flag any reading below 0.312 in on this circuit. That is a comparison against a number someone else supplied. Deciding whether an indication in a weld is lack of fusion or geometry, or whether a thin reading represents general wastage or a localised pit, is evaluation and it belongs to Level II.

In practice this boundary is where good crews are built. The Level I who understands the boundary escalates early, records what they saw rather than what they concluded, and gives the Level II clean data. The Level I who quietly makes calls to keep the survey moving generates a corrosion database nobody can trust, and that shows up two years later as a remaining-life calculation built on invented numbers.

Texas City: the industrial base that hires UT Level I technicians

Texas City occupies the western shore of Galveston Bay inside the Houston-Galveston industrial complex, one of the densest concentrations of refining and petrochemical capacity anywhere in the United States. The local base runs to crude refining, olefins and derivative chemicals, specialty chemical production, bulk liquid terminals and the deepwater berths and pipelines that connect them. Around the plants sits a large population of maintenance and turnaround contractors drawing labour from across Galveston County and the wider bay area.

That base consumes ultrasonic thickness measurement at industrial scale. Piping circuits carry condition monitoring locations that must be re-read on a schedule to feed corrosion rates and remaining life. Vessels have shell and head grids. Storage tanks have shell courses read by course and by orientation. Docks, loading lines and marine transfer piping add their own populations. Most of these readings are straight beam pulse-echo on carbon steel, and most of them are taken by Level I technicians working from a written instruction that names the transducer, the calibration block, the couplant and the exact grid.

The region also carries an unusually sharp process safety culture, shaped by a catastrophic refinery incident in 2005 and the investigation that followed. One practical consequence for a technician is that mechanical integrity data receives real scrutiny. Readings are traceable to a location, a date, an instrument and a person. A Level I here is not producing numbers for a file; they are producing numbers that will be used to justify continued operation, and the audit trail is expected to hold up.

Calibration is the Level I's real job

Everything a Level I is trusted to do rests on calibration. A pulse-echo gauge measures elapsed time between pulses and converts it to distance using an assumed velocity, corrected by a zero offset that accounts for the delay through the transducer, wear face and couplant layer. Get either wrong and the instrument reports a confident, precise, incorrect number. There is no signal on the screen that tells you the velocity was wrong.

Velocity is a property of the material, not a setting you choose for convenience. Longitudinal velocity in carbon steel is around 5,900 m/s, roughly 0.233 in/µs, but austenitic stainless, cast components, weld metal and clad layers all differ, and anisotropy in coarse-grained austenitic material makes the assumption shakier still. The correct practice is a two-point calibration on a step block of the same material as the part, covering thicknesses either side of the expected range, followed by verification on a known thickness before and after the survey and at the interval the procedure sets.

Temperature is the correction most often skipped. Sound velocity in steel falls as temperature rises, and ASME Section V requires the calibration block temperature to be within a defined tolerance of the examination surface temperature. On a line running hot, a probe zeroed at ambient on a bench block will over-read. The procedure will either require calibration on a heated block, a high-temperature delay line transducer, or a stated correction factor. A Level I who does not know which of the three the procedure calls for is not ready for the field.

Thickness gauging: where the readings go wrong

The classic failure is doubling. On thin material, or when the gauge misreads which echo is which, the instrument locks onto the second back-wall echo and reports twice the actual thickness. It reads as a plausible number and nothing looks wrong. The defence is knowing the minimum thickness capability of your probe and instrument combination, watching the A-scan rather than trusting the digital readout alone, and treating any reading that suddenly doubles from its neighbours as suspect until proven.

Coating is the second. In standard pulse-echo mode the gauge measures from the outer surface of the paint to the back wall and adds the paint into the answer. Echo-to-echo mode with a dual element transducer measures between successive back-wall echoes and therefore ignores the coating entirely. Knowing which mode the procedure requires, and confirming the instrument is actually in it, prevents a survey where every reading is systematically thick by the coating thickness. On heavily coated dock piping that error is not trivial.

Then come the surface and geometry effects. Loose scale and rust break couplant contact and attenuate the return. Internal pitting reflects from a pit floor rather than the general wall, so a single low reading may be a real pit or a mis-seated probe — the correct Level I response is to re-take, note the condition and escalate rather than average it away. Curvature on small diameter piping reduces contact area and can lose the back wall entirely unless a contoured shoe or a smaller probe is used. Every one of these is a documentation event, not a judgement call.

Training hours, experience hours and the written practice

SNT-TC-1A recommends 40 hours of organised classroom training for ultrasonic Level I, and 210 hours of documented experience in ultrasonics against 400 hours of total NDT experience. Those are recommendations in a recommended practice, which is a distinction that matters: they become requirements only when your employer adopts them in its written practice. The written practice may exceed them, and on Galveston Bay client specifications frequently push contractors past the table, particularly for work feeding fixed equipment integrity programmes.

Experience is counted in documented hours performing ultrasonic work, not in months on the payroll. Keep a log as you work: date, location, equipment, technique, hours, and the name of the Level II or III directing the work. Reconstructing an experience record eighteen months later from timesheets is the single most common reason a technician who is genuinely ready gets held back. It also becomes the finding an auditor writes up when the record shows 'two years, ultrasonics' with nothing behind it.

ISO 9712 counts the same substance differently. It asks for training hours plus industrial experience expressed in months — for ultrasonics generally around three months at Level 1 — and it hands the examination to an independent certification body rather than the employer. A technician on Galveston Bay will normally certify under an SNT-TC-1A written practice because that is what the local market runs on, but keeping the experience log in a form that would also satisfy ISO 9712 costs nothing now and preserves the option later.

Inside the three examinations

Level I certification in ultrasonics requires three examinations. The general examination covers method principles: wave modes and how they propagate, velocity and acoustic impedance, reflection and refraction at interfaces, Snell's law, near field and beam spread, attenuation, transducer construction and damping, and instrument controls. The specific examination covers your employer's equipment, procedures, techniques and the acceptance criteria in the specifications you will actually work to. The practical requires you to do the job on real specimens. SNT-TC-1A recommends a composite grade of at least 80 percent with no single part below 70 percent.

The practical is where the level is genuinely tested. You will be handed an instrument, a transducer, couplant, calibration blocks and a written instruction, and asked to calibrate, perform the specified examination and record the results on the employer's forms. Graders score two things separately: whether you obtained the correct data, and whether you followed the procedure. Points are lost far more often on the second — a verification check skipped, the wrong block used, surface temperature not recorded, the couplant not identified, the form left unsigned.

The specific examination is deliberately not portable. It is written against the employer's own procedures, so a technician moving between contractors in the bay area sits a new specific examination at the new employer even holding a valid certification at the same level in the same method. Treat that as normal rather than as a setback, and arrive with the prior training certificates, experience log and vision examination records that let the new employer credit everything else.

DAC and DGS: what a Level I meets but does not own

Distance amplitude correction and distance gain size are the two ways ultrasonic amplitude is normalised against range, and a Level I will encounter both without being responsible for either. A DAC curve is built empirically: the same reference reflector — typically a side-drilled hole in a basic calibration block — is scanned at several depths, the peak response at each depth is marked, and the marks are joined to form a curve that shows how the response from an identical reflector decays with sound path. Amplitude is then reported as a percentage of DAC.

DGS, also called AVG, does the same job theoretically rather than empirically. It uses probe-specific diagrams relating distance, gain and equivalent reflector size, so a single set of curves for a characterised probe replaces a block-built curve. It requires accurate probe characterisation and a transfer correction between the reference block and the actual part, and it is used where building a representative DAC block is impractical.

For a Level I, the practical point is this: you may be instructed to construct a DAC curve as part of a calibration, because construction is a procedural task with a defined sequence. You do not decide whether DAC or DGS applies, what reference reflector is appropriate, what transfer correction to allow, or what an amplitude of 60 percent DAC means for acceptance. Those are Level II and Level III decisions. Understanding the mechanics anyway is exactly what shortens the road to Level II.

From Level I to Level II, and keeping certification alive

The transition to Level II is where the job changes in kind rather than degree. A Level II selects the technique for the task, sets up and calibrates for it, interprets and evaluates against codes, standards and specifications, prepares the written instructions the Level I works from, organises and reports results, and provides on-the-job training. The recommended additional training is another 40 hours, and the experience requirement steps up to 630 hours in ultrasonics against 1,200 hours total. The step that actually takes time is accumulating varied work — welds as well as thickness, different geometries, different materials.

Certifications lapse, and recovering one is easier than re-earning it. Written practices carry recertification intervals, commonly not exceeding five years, and interrupted service provisions covering technicians who have been away from the method. Recertification typically requires evidence of continuing satisfactory performance or re-examination, plus a current near-vision acuity examination. Bring the paperwork: prior certificates, the experience log, examination records and vision history. Without them, a straightforward recertification turns into starting from Level I.

Atlantis delivers UT Level I and Level II training in classroom, on-site corporate and blended formats, using the employer's own instruments and procedures where the training is delivered on site, so the specific examination reflects the work rather than a generic syllabus. We also provide ASNT Level III consulting for employers who need a written practice built or rewritten, examinations prepared and graded, or a Level III of record. Contact info@atlantisndt.com for a consultation or a quote.

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