What an SNT-TC-1A Written Practice Must Contain to Survive an Audit
A written practice survives audit when it converts SNT-TC-1A's "should" recommendations into enforceable "shall" requirements specific to your operation, covers every core element — scope, qualification levels, training and experience hours, examination administration and grading, vision testing, certification records, recertification, and interrupted service — and is backed by a record proving each stated requirement was actually met.
SNT-TC-1A is a recommended practice, not a standard. It becomes binding only through your written practice — the employer-controlled document that states how personnel are qualified and certified at your company. Auditors from ASME shops, API facilities, primes, and nuclear vendors walk a three-layer chain: the recommended practice, your written practice, and the individual certification records. A gap at any layer is a finding. The 2024 edition (with Addendum) explicitly permits modifying detailed recommendations, but modifications may alter — never eliminate — the basic provisions of training, experience, examination, and recertification, and the technical rationale for each deviation belongs in an annex. Once approved, the written practice is a procedural requirement: partial compliance with your own document is itself a finding.
Source: ASNT Recommended Practice No. SNT-TC-1A (2024 edition with Addendum), asnt.org — verified August 2026
| Element | What SNT-TC-1A says | What YOUR written practice must state | The record that proves it |
|---|---|---|---|
| Scope | Employer defines applicability to its own operations | The exact NDT methods, techniques, and business units the document governs, by name | Controlled-document register with revision history and approval signatures |
| Levels of qualification | Defines Trainee, Level I, Level II, Level III responsibilities | Duties per level as they exist in your operation — who runs tests, who interprets and reports, who approves procedures | Job descriptions and certifications that match duties actually performed |
| Training | Recommends minimum training hours per method and topical outlines (CP-105) | Committed hour counts per method and level, the outline followed, and which providers are acceptable | Training certificates showing hours, dates, content outline, and instructor |
| Experience | Recommends minimum experience per method and level | Required hours, how simultaneous multi-method experience is credited, and who supervises trainees | OJT logs signed and dated by the supervising certified individual |
| Examinations | General, specific, and practical exams; composite grade of at least 80% with no individual exam below 70% | Question counts, who administers and grades, and the checkpoints scored in the practical (minimum ten) | Graded exam papers, practical checklists, and the examiner's signature |
| Vision | Near-vision acuity (Jaeger No. 1 or equivalent at not less than 12 inches) annually; color contrast differentiation at intervals not exceeding five years | The chart or method used, who administers it, and how the schedule is tracked | Vision examination records with date, administrator, and result |
| Certification | The employer certifies; records must document the basis of certification | Who signs certifications (the Level III or designee) and every item each certification record contains | Certification records: method, level, exam results, dates, and signatures |
| Recertification | Maximum five-year interval, by continuing satisfactory performance evidence or re-examination | Your interval and exactly what evidence of continued performance you accept | Recertification records and documented performance evaluations |
| Interrupted service | The written practice defines what interruption triggers requalification | The threshold (months away from the method) and the reinstatement rules | Assignment and employment history showing continuity |
| Modifications | May alter but shall not eliminate basic provisions; rationale documented | Each deviation from SNT-TC-1A's detailed recommendations, with technical rationale in an annex | The annex itself, approved by the responsible Level III |
Why "should" copied as "should" fails every audit
The failure is mechanical, not stylistic. SNT-TC-1A is written entirely in recommendation language because ASNT designed it to be tailored by each employer. When a written practice reproduces that language — "the candidate should complete the training hours" — it commits the employer to nothing. An auditor cannot cite a company for missing a target the company never adopted, so instead the auditor writes the deeper finding: the written practice does not establish requirements at all, which invalidates every certification issued under it.
The fix is a full should-to-shall conversion pass. Every operative sentence either becomes a "shall" your records can prove, or becomes a documented deviation with technical rationale in the annex. There is no third state. Companies that run this conversion element by element — using a checklist like the table above — turn an unpassable audit into a records-retrieval exercise, because each "shall" points to exactly one record type.
The three-layer chain an auditor actually walks
Audits of employer-based certification follow a fixed route: the invoked edition of SNT-TC-1A, then your written practice, then the certification records of the individuals on the job. The auditor is checking two seams. Seam one: does the written practice address every element the recommended practice covers, with requirements at least as coherent as the original? Seam two: does every record match what the written practice says must exist — same hour counts, same grading, same signatures?
Most findings live at seam two, because written practices are often drafted once and never reconciled against how the company actually trains and examines. If your document commits to a specific training-hour count for a method but the training certificates in the file show fewer, the certification fails against your own requirement — regardless of whether the technician is competent. Before any external audit, run the reconciliation internally: pull three technician files at random and trace every claim in the written practice to a physical record.
The edition matters too. State on the cover which edition of SNT-TC-1A the document is based on, because the governing code or customer contract usually invokes a specific one. Certifying to the 2024 edition when the contract calls the 2016 edition — or the reverse — is a finding an auditor can write in the first five minutes.
Training and experience: commit to numbers, don't gesture at tables
SNT-TC-1A carries recommended minimum training and experience hours for each method and level, and points to ANSI/ASNT CP-105 for topical outlines. A written practice that says "training per SNT-TC-1A tables" without restating the numbers creates two audit problems: the requirement changes silently whenever the edition changes, and the auditor cannot tell whether you adopted the recommendation or modified it. State the hour counts explicitly, per method, per level, in your own table.
Experience requirements need one more sentence most documents omit: how simultaneous multi-method experience is credited. Technicians commonly log MT and PT hours on the same shift; SNT-TC-1A permits crediting concurrent experience under defined conditions, and your written practice must state the rule you apply. The proving record is the OJT log — dated, method-specific, and signed by the supervising certified individual. An experience claim with no signed log behind it is an experience claim the auditor rejects.
Examinations: the five records the auditor asks for by name
For each certified individual, expect to produce: the general examination (method fundamentals), the specific examination (your procedures and equipment), the practical examination checklist, the composite grade computation, and the examiner's identity and qualification. SNT-TC-1A recommends the composite passing grade be at least 80 percent with no individual exam below 70 percent, and the practical demonstration be scored against a checklist covering a minimum of ten different checkpoints. Your written practice must state all of this as requirement, plus who administers and who grades.
The practical exam checklist is where files most often thin out. A signed sheet that says "passed" with no checkpoints is not a practical examination record — it is an assertion. Build the checklist into the written practice as an appendix or controlled form so every examiner scores the same items: equipment setup, calibration, coverage, detection of the seeded or known discontinuity, interpretation, and reporting. The specific exam earns similar scrutiny: it must test your procedures, not generic method knowledge, and auditors check whether its questions reference documents that actually exist in your system.
Vision, recertification, and interrupted service — the quiet failures
Vision records lapse more often than any other element because they are annual while everything else runs on multi-year cycles. SNT-TC-1A calls for near-vision acuity in at least one eye — Jaeger No. 1 or equivalent at a distance of not less than 12 inches — checked annually, and color contrast differentiation examined at intervals not exceeding five years. Your written practice must name the chart or method, the administrator, and how due dates are tracked. A certified technician with a fifteen-month-old vision record is performing NDT while unqualified under your own document.
Recertification and interrupted service are defined by you, within the five-year ceiling. State whether recertification runs on continuing-performance evidence, re-examination, or both — and define what "evidence of continuing satisfactory performance" physically is, because an auditor will ask to see it. Interrupted service is the clause companies forget entirely: define how many months away from a method triggers requalification and what the reinstatement path is. Silence here means an auditor decides for you, mid-audit, with your technician's certification in the balance.
Modifying SNT-TC-1A defensibly: the annex is your shield
The 2024 edition is explicit: the employer shall modify SNT-TC-1A as necessary to fit the work its personnel actually perform, and modifications may alter but shall not eliminate the basic provisions — training, experience, examination, recertification. This is permission, not a loophole. Reducing a training-hour recommendation for a narrowly-scoped technique can be legitimate; deleting the practical examination never is.
Every deviation needs its technical rationale documented, and the recommended home for that rationale is an annex to the written practice. The annex converts a deviation from "the company ignored the recommended practice" into "the responsible Level III evaluated the recommendation against the actual work scope and documented why the alternative provides equivalent assurance." Auditors accept the second and cite the first, even when the underlying change is identical. Have the Level III sign the annex, date it, and revise it whenever scope or edition changes — an unsigned rationale is a memo, not a control.
Using an outside Level III without creating a new finding
Most employers running employer-based certification do not staff a full-time Level III — they contract one. SNT-TC-1A supports this: an outside agency's Level III can author the written practice, design and administer examinations, evaluate OJT, and act as the employer's designee. What the arrangement cannot do is move responsibility. The employer certifies its own personnel; the outside Level III's signature appears as designee under authority your written practice explicitly grants. The full division of authority is mapped in what an outside NDT Level III can and cannot do.
The audit-relevant details: name the outside Level III arrangement in the written practice itself, keep the Level III's own certification records on file as evidence of examiner qualification, and ensure the document states which signatures the designee provides versus which stay with company management. Atlantis provides outsourced ASNT Level III services on exactly this model — written practice authorship, exam administration, and annual program maintenance — affordable, accessible, and fully customizable to your methods and codes. Quote on request.
Is SNT-TC-1A mandatory?
No — it is a recommended practice, and every requirement in it is written as "should." It becomes mandatory only when your written practice adopts it as "shall," or when a governing code, contract, or customer specification invokes it. At that point your written practice, not SNT-TC-1A itself, is the auditable requirement.
Who writes and approves a written practice?
The employer owns it, and an NDT Level III writes or approves the technical content — training hours, exam design, method-specific requirements. That Level III can be an employee or a contracted outside Level III acting as the employer's designee; responsibility for certification always remains with the employer.
What is the most common audit finding in written practices?
SNT-TC-1A's "should" language copied verbatim into the written practice. An auditor reading "examinations should be administered" has no requirement to verify — the document describes a recommendation instead of committing the employer to anything. Every operative "should" must become "shall" or an explicitly justified deviation.
What exam grades does SNT-TC-1A recommend?
A passing composite grade of at least 80 percent, with no individual examination — general, specific, or practical — graded below 70 percent. Your written practice must state these as requirements and name who computes and signs the composite grade, because the graded papers are the records an auditor pulls first.
How often are recertification and vision checks due?
Recertification at intervals not exceeding five years, by evidence of continuing satisfactory performance or by re-examination as your written practice defines. Near-vision acuity is checked annually; color contrast differentiation at intervals not exceeding five years. Lapsed vision records are among the fastest findings to write.
Can an outside Level III sign our certifications?
Yes — SNT-TC-1A allows the employer to use an outside agency's Level III to write the practice, administer exams, and act as designee. What never transfers is responsibility: the employer certifies its own personnel. The split of duties is detailed in what an outside NDT Level III can and cannot do.