2.1 SNT-TC-1A: The Employer-Based Recommended Practice

SNT-TC-1A: The Employer-Based Recommended Practice

Recommended Practice No. SNT-TC-1A is the most-cited personnel document in North American nondestructive testing (NDT), and a Level III must know exactly what it is and, just as importantly, what it is not. It is published by the American Society for Nondestructive Testing (ASNT), and its formal name announces its legal character: it is a recommended practice — a set of guidelines, not a specification, standard, or code. It uses the permissive word should rather than the mandatory word shall. Nothing in SNT-TC-1A binds an employer until that employer chooses to adopt it.

The classic Basic-exam trap is treating SNT-TC-1A as a rulebook that a technician must pass or 'meet.' You are never certified to SNT-TC-1A; you are certified by your employer under a program that SNT-TC-1A helped shape. Understanding that one distinction unlocks a large fraction of the certification-and-qualification questions on the exam.

Employer-based certification

SNT-TC-1A describes an employer-based (in-house) model in which the employer is the certifying authority. Through its NDT Level III, the employer weighs each candidate's training, experience, examination results, and vision, then issues a certification that authorizes specific NDT tasks within that organization. The certification is not portable: when the employee leaves, the certification normally ends, because it reflected the employer's judgment about that person inside that program. This is the sharp contrast with the central schemes in the next section, where an independent body issues a credential the individual carries between jobs.

The written practice — the document that actually governs

Because SNT-TC-1A only recommends, the operative document at any facility is the written practice. SNT-TC-1A recommends that each employer establish a written practice describing how it qualifies and certifies personnel. The written practice states the levels used; the education, training, and experience minimums for each method and level; the examinations required and their passing scores; certification and recertification intervals; vision requirements; and records retained. The employer's NDT Level III normally writes, reviews, and approves the written practice and revisits it periodically so it stays aligned with current codes and business needs.

Two consequences matter for the exam. First, an employer may make its written practice more restrictive than SNT-TC-1A and is expected to tailor it, but it must not quietly relax a requirement that a governing code or contract has made mandatory. Second, an auditor checks personnel files against the written practice, not directly against SNT-TC-1A. The audit question is always, 'Does this record match the written practice?'

What SNT-TC-1A recommends

Vision, examinations, and recertification

SNT-TC-1A recommends annual near-vision and color/contrast checks, with near-vision acuity of Jaeger Number 2 (or equivalent) at not less than 12 inches. For Level I and II it recommends a general, a specific, and a practical examination, plus interpretation of a test specimen; the Level III examination is structured as a basic, a method, and a specific portion. It recommends a maximum certification interval of five years, with recertification based on either evidence of continued satisfactory performance or re-examination, and it addresses interrupted service, where a significant break may trigger additional training or re-examination as defined in the written practice.

A worked scenario

Suppose an ASME-code job references SNT-TC-1A for personnel qualification. The employer cannot simply hand inspectors a copy of SNT-TC-1A; it must implement the recommended practice through a written practice, then qualify and certify each inspector against that written practice. If the code demands a specific certification but the written practice is silent about it, the written practice is deficient and must be revised. The Level III who signs the written practice owns that gap.

Records and the trainee tier

SNT-TC-1A also recommends a records framework: the employer keeps documentation of each individual's education, training, experience, examination results, and current vision status, retained for the certification period so an auditor can reconstruct the qualification decision. Below Level I sits the trainee, who is not certified and works only under the direct supervision of a certified individual; a trainee may not independently accept or reject material. Recognizing the trainee tier prevents a common error — assuming everyone performing NDT tasks must already be certified. The certification ladder is trainee, then Level I, Level II, and Level III, and each rung is defined by the written practice.

The 2024 edition and the exam

SNT-TC-1A is revised periodically, and the 2024 edition is current. This is not trivia for Level III candidates: effective January 1, 2026, ASNT changed the Basic-exam recommended self-study references from the 2020 editions of SNT-TC-1A and CP-189 to the 2024 editions. Study the current edition's structure and its should-based language, because exam items frequently hinge on telling a recommendation apart from a requirement.