Running NDT certification exams: written, practical and proctored

Every nondestructive testing (NDT) certification rests on examinations, and the examinations are where an audit most often finds something wrong: a question count below the minimum, a practical without a checklist, a score averaged the wrong way, or an exam given by someone who should not have given it. This guide walks through how certification exams work under SNT-TC-1A and NAS410 — the two schemes most US programs run on — and what it takes to run them cleanly, whether on paper or online.

The three exams, and the fourth for Level 3 or III

For each method, Levels I and II (or 1 and 2) sit three exams:

• General — the principles and theory of the method. Closed book under both schemes.
• Specific — the employer's own specifications, procedures, equipment, techniques and acceptance criteria. SNT-TC-1A treats it as a written exam that may supply the necessary reference data; NAS410 makes it open book, with the reference material provided and questions that test understanding rather than finding a page.
• Practical — doing the work on real test pieces with known discontinuities, graded against a checklist.

Level III (SNT-TC-1A) sits a Basic exam once, then a Method exam, a Specific exam and in most cases a Practical in each method. NAS410 Revision 6 makes its three-part Basic exam — methods, materials and manufacturing, and NAS410 itself — a prerequisite for Level 3 that is passed at 80% per section and kept out of the composite.

How many questions

Passing and averaging

• SNT-TC-1A (2024): at least 70% on every written exam, at least 80% on the practical, and a composite — the simple average of General, Specific and Practical — of at least 80% (8.1.4–8.1.5). CP-189's 2018 addendum sets the same marks for employer-administered exams, with every exam weighted equally.
• NAS410 (Rev 6): at least 70% on each exam, every discontinuity the Level 3 specified found on the practical, and an average of at least 80%, with exams weighted equally — so a recertification that gives only specific and practical averages only those two (7.2.3).
• Pass/fail certificates: where an outside agency or central certificate reports only pass or fail, SNT-TC-1A lets the employer count it as 80%, and NAS410 assigns 80% to a pass/fail ASNT, ISO 9712 or national-board certificate used in place of the general exam.

Who may examine

This is the rule auditors test hardest, and the one most easily broken in a small shop.

• Under SNT-TC-1A, a Level III is responsible for administering and grading. They may delegate to a representative who has documented instruction in giving and grading exams; the practical is given by a Level II or III in the method, and the Level II practical by a qualified Level III (8.1.2).
• Under NAS410, the Responsible Level 3 or an Examiner certified in the method administers and grades. Multiple-choice administration can be delegated in writing; essay and fill-in answers are judged by the Responsible Level 3 or Examiner (7.2.1).
• Under both, nobody is examined by themselves or by a subordinate.
• An internal auditor designation confers no authority to examine. Nor does a Level II certification examine a Level III.

Outside examiners are allowed, but the employer stays responsible: it documents that the service meets its written practice (SNT-TC-1A 8.1.7) or that everyone involved meets the standard (NAS410 7.2.2).

Practical exams

The practical is where a candidate proves they can do the work, and both schemes want it planned in writing:

• Specimens. SNT-TC-1A asks for at least one flawed specimen, approved and documented by the Level III with a grading key. NAS410 asks Levels 1 and 2 for at least two test samples of differing configurations per method, at least one per technique, representative of the employer's product and unfamiliar to the candidate.
• A checklist. SNT-TC-1A recommends at least ten checkpoints, with any must-pass checkpoint clearly marked, and the written practice setting the acceptable detection rate and false calls. NAS410 requires a written checklist covering the use and standardization of equipment, procedure, and interpretation and evaluation.
• Documentation. The specimen, procedure, checkpoints and results are recorded, and how the candidate documents results is decided in advance.
• Level III. Usually preparing a procedure, plus a hands-on practical if the Level III will perform NDT or accept parts.

Retakes

SNT-TC-1A recommends a 30-day wait or additional training the Level III decides on (8.7). NAS410 requires documented training on the deficient areas first, a different paper with at least 25% new questions, different test samples, and a retake within the written practice's window, which cannot exceed six months; failing a recertification exam suspends the current certification (7.2.4).

Online, on paper, and proctored

Neither standard cares whether an exam is on paper or on a screen. They care that it is closed book where required, that the right person controls and grades it, that the question counts and passing marks are met, and that you can show all of it afterwards. Online exams do some of that well — automatic grading, draw rules that give each candidate a different paper, time limits, a complete record — and some of it less well: no website can stop a phone photograph of the screen. For a high-stakes exam, pair online delivery with supervision, or sit it on paper in a room you control.

Crediting the result

The exam is not the certification. The score has to land on the certification record, with the composite, the exam or evidence of it, the Level III who verified the qualification and the certifying signature. Copying scores from a gradebook into a certificate by hand is where transcription errors creep in.

Building the questions themselves is its own discipline — see the question bank guide.

Frequently asked questions