What it is, how it works, personnel levels, training and experience requirements, examinations, and the questions nobody answers clearly.
BY DAN YAMASHITA · ASNT/PCN LEVEL 3 · SIMPLE NDT · · 7 MIN READ
SNT-TC-1A (Recommended Practice No. SNT-TC-1A) is a document published by the American Society for Nondestructive Testing (ASNT) that serves as a guideline for companies to develop their own internal programs for the qualification and certification of Nondestructive Testing (NDT) personnel.
A crucial point: SNT-TC-1A is not a standard. It is a recommended practice. This means each company has the flexibility to adapt the guidelines to its own reality, as long as those adaptations are documented in its Written Practice.
Certification performed in accordance with SNT-TC-1A is often referred to as "ASNT certification" — incorrectly. Only certificates issued directly by ASNT (such as ASNT NDT Level III or ACCP) can properly be called ASNT certification. SNT-TC-1A certification is issued by the employer, not by ASNT.
SNT-TC-1A is recognized by codes such as ASME, API, AWS, ASTM, and AMPP.
The Written Practice is the internal document each company prepares to define how it qualifies and certifies its own NDT personnel. It is built from SNT-TC-1A: it takes the guidelines of the recommended practice and turns them into the organization's own rules.
The name can be misleading. "Practice" sounds operational, almost like a test instruction — but it is not. The Written Practice is the document that establishes the company's qualification and certification requirements: scope of methods and levels, education, training and experience hours, examinations and pass criteria, validity, recertification, and responsibilities. It is the document that governs the company's NDT program, not a step-by-step inspection procedure.
One detail captures its nature: SNT-TC-1A is written in advisory language, using "should." When a company transcribes those guidelines into its Written Practice and the Level III approves it, every "should" becomes "shall." From that point on, compliance is mandatory within the company.
SNT-TC-1A is not a standard or a specification — it is a recommended practice. On its own, it certifies no one and creates no mandatory requirements. What gives those guidelines binding force is the company's Written Practice. Without it, there is no valid qualification and certification system under SNT-TC-1A: it is the document that turns the program into reality.
That is why, when a fabrication code (ASME, AWS, API) or a customer requires "qualification in accordance with SNT-TC-1A," what an audit expects to find is the company's Written Practice — approved by the Level III — together with the records proving each inspector was certified according to it.
Under the SNT-TC-1A model, the employer is the certifying authority. The company trains, examines, and certifies its own inspectors, based on its own Written Practice and under the responsibility of its Level III. The certification is valid within that company and according to that document — it is not automatically transferable to another employer.
This is the key contrast with centralized certification. Under a central scheme such as ISO 9712 (for example, PCN, or the SNQC operated by ABENDI in Brazil), an independent body issues the certification: the inspector is certified by that body, carries the certification with them, and takes it from one employer to another. Under SNT-TC-1A, that role belongs to the company — and the Written Practice is the document that underpins this authority.
In practice, both the Written Practice and the certificates issued under it are always tied to a company. A self-employed professional can only operate in this model by setting up (or being attached to) a legal entity that maintains the Written Practice and takes responsibility for certification. For those without employment ties, the natural route is centralized certification under ISO 9712.
The term is worth clarifying, because it causes confusion. The certifying authority is who issues the certification and answers for it — who signs off and takes on the commitment that the person was evaluated and is qualified. Under SNT-TC-1A, that role belongs to the employer: the certification is an act of the employer's program, described in its Written Practice, and is valid within it.
The most common misconception is to think that "the ASNT Level III is the one who certifies people." The Level III is the program's technical authority: they develop and approve procedures, prepare and administer the examinations, evaluate the candidates, and sign the certificate. But they do all of this on behalf of the employer, not in their own name. The certification belongs to the employer's program, not to the Level III. In fact, when an employer hires an external Level III to run the process, that person does not issue their own certification: they work within that employer's Written Practice, and the employer remains ultimately responsible. Holding an ASNT NDT Level III credential qualifies someone to act as the Responsible Level III, but it does not, by itself, make that person the authority that certifies the inspectors.
Need to develop or review your company's Written Practice? See the personnel qualification service.
Full responsibility for certification rests with the employer. Even when external agencies (independent Level 3 consultants) are engaged for training or examination, the employer remains responsible for ensuring that these services comply with its Written Practice — and for the final certification.
In practice, many companies adopt an inadequate interpretation of this principle: they delegate full responsibility to the external Level 3 and exempt themselves from process oversight. This compromises inspector technical competence and can lead to serious problems during audits.
Each company creates its own Written Practice describing the requirements for qualification and certification. Employers may adapt SNT-TC-1A guidelines — for example, by creating limited certifications (sub-levels) for specific scopes.
Although limiting scope is not common practice (e.g., certification valid only for butt welds), it is the employer's responsibility to understand the complexity of the inspections, know the limitations of their inspectors, and provide adequate training for each type of application.
Performs all test steps except evaluation of results. Must receive instruction and supervision from a certified Level II or III. May segregate parts and record indications. The employer's Written Practice may allow Level I to perform and sign final acceptance, provided it is in accordance with written procedures.
Interprets procedures and standards. Performs and evaluates results in accordance with procedures. Issues test reports. May train and supervise Level I personnel and trainees.
The highest level. Responsible for establishing techniques, developing, qualifying, and approving NDT procedures. Interprets codes, standards, and specifications. Recommends the most appropriate method when not pre-established. Certifies Level I and Level II inspectors in NDT methods.
Learn more about Level 3 services: personnel qualification and procedure development.
SNT-TC-1A defines minimum hours of formal training and supervised practical experience for each method and level. Values vary by method — ultrasonic testing and radiographic testing require significantly more hours than visual testing or liquid penetrant testing.
An individual may be qualified directly to Level II without prior Level I certification, provided the training and experience requirements include the combined hours for both levels.
Need training for your team? See the available training programs.
Covers the basic principles of the applied method: physics, equipment, terminology, and technique fundamentals.
Covers equipment, operating procedures, and test techniques, as well as codes, standards, specifications, and acceptance criteria applicable to the employer.
The candidate demonstrates familiarity and ability to operate equipment and analyze results. At least one specimen containing a discontinuity must be tested.
Annual mandatory examination: near-distance visual acuity capable of reading Jaeger Number 1 at 12 inches (30.5 cm), natural or corrected. Additionally, color differentiation testing (typically Ishihara) and/or gray-scale discrimination for radiography.
The interval is 5 years for all levels. Recertification requires evidence of satisfactory performance or re-examination at the discretion of the Level III. For ASME, technical performance evaluation is mandatory prior to recertification of Level I and Level II personnel.
Examinations, Written Practice, training, or consulting. All certified methods available.