SNT-TC-1A is ASNT's recommended practice for qualifying and certifying nondestructive testing (NDT) personnel, and the employer, not ASNT, does the certifying through its own written practice. Published summaries of the 2024 edition recommend 40 training hours and 210 hours of method experience for UT Level I, an annual near-vision check and recertification at least every 5 years.
Because SNT-TC-1A is guidance, the figures in it become binding only when an employer adopts them in a written practice, or when a code or contract calls for them. That is why the same "SNT-TC-1A Level II" can mean slightly different things at two companies, and why an auditor asks for the written practice before anything else.
In this guide: what SNT-TC-1A is · the written practice · Levels I, II and III · 2024 hours for UT, MT and PT · exams · vision · recertification · CP-189 and ASNT 9712 compared · where codes call for it (AWS D1.1, ASME, FRA 213.238) · worked example · limits · FAQ
What is SNT-TC-1A?
SNT-TC-1A is a recommended practice published by the American Society for Nondestructive Testing (ASNT) that tells employers how to set up their own program for qualifying and certifying NDT staff. The current edition is SNT-TC-1A (2024), with an addendum issued in 2025.
ASNT's standards page describes it as "Employer guidance for in-house NDT personnel qualification and certification programs." It covers the recommended education, training, experience, examinations and vision checks for each NDT method and level. Secondary histories date the first edition to 1966; the original article's claim that adoption "accelerated" in the 1970s and 1980s had no source and is not repeated here.
SNT-TC-1A is not a certificate, a license or a federal rule. Nobody is "certified by SNT-TC-1A". A technician is certified by an employer, in accordance with SNT-TC-1A, under that employer's written practice.
Key takeaway: SNT-TC-1A is a framework an employer adopts, not a credential a person holds.
Who certifies NDT personnel under SNT-TC-1A?
The employer certifies. ASNT publishes the document and answers formal interpretation requests, but it does not examine or certify anyone under SNT-TC-1A.
ASNT made this point sharply in a June 2026 advisory. It had found certificates issued by training organizations, often signed by a Level III, that claimed SNT-TC-1A compliance with no real link to an employer's program:
"Training institutes may provide NDT training but cannot independently issue certifications under SNT-TC-1A." (ASNT, Advisory on SNT-TC-1A Certification Practices and Use of ASNT Credentials, P. Lang, June 11, 2026)
The same advisory says SNT-TC-1A certifications "should only be issued by employers as part of their internal qualification system", and that "The use of ASNT's name or logo on certificates is prohibited." So a training course certificate is evidence of training hours. It is not a certification.
This is the most common error in articles on the subject, including the original version of this page, which called ASNT "the certifying organization that administers SNT-TC-1A." That is wrong. ASNT does run its own central certification programs (the ASNT NDT Level III and ASNT 9712), but those are separate from SNT-TC-1A.
Key takeaway: a training school trains, the employer certifies, and ASNT certifies only under its own central programs.
What is an SNT-TC-1A written practice?
The written practice is the employer's own procedure that says how it will train, qualify, examine, certify and recertify its NDT personnel. ASNT's director of standards described it in 2020 as "a written practice (procedure) that addresses how the employer will train, qualify, and certify NDT personnel." Once the employer and its Level III approve it, the employer must follow it.
A sound SNT-TC-1A written practice normally covers:
| Topic | What the written practice should state |
|---|---|
| Scope | The NDT methods and techniques covered, and the levels used (trainee, I, II, III) |
| Duties | What each level may and may not do, including who may sign reports and accept or reject |
| Training | Hours per method and level, course content (ANSI/ASNT CP-105 outlines), and who may teach |
| Experience | Method hours and total NDT hours, how they are logged and verified |
| Examinations | General, specific and practical exams, question counts, passing grades, retake rules, who administers them |
| Vision | Near-vision and color-contrast tests, the chart, distance and interval |
| Certification | Who signs as the certifying authority, and what the certification record holds |
| Recertification | Interval, and whether by evidence of continued performance or by re-examination |
| Interrupted service | What happens after a break in the method |
| Records | Where qualification records are kept and for how long |
| Outside agencies | Use of an outside Level III or an examination supplier, if any |
The written practice can adopt SNT-TC-1A's numbers as they are, or raise them. An employer that lowers them can still have a written practice, but the program may no longer satisfy a code or customer that asks for SNT-TC-1A, so the reductions need a documented reason.
Key takeaway: the written practice is what an auditor reads, and it is what makes SNT-TC-1A's recommendations binding inside one company.
What do SNT-TC-1A Level I, Level II and Level III personnel do?
SNT-TC-1A recognizes three certified levels, plus an uncertified trainee, and each step up adds responsibility for setting up, interpreting and approving the work. The summaries below follow the level definitions as published summaries describe them; check the wording against the licensed 2024 text.
| Level | Typical scope under SNT-TC-1A | What is reserved to a higher level |
|---|---|---|
| Trainee | Works alongside certified personnel to build experience hours | Can't conduct tests independently, interpret, accept or reject, or sign reports |
| Level I | Performs specific calibrations (standardizations), specific NDT and specific accept/reject evaluations according to written instructions, and records results | Interpreting and evaluating results against codes, standards and specifications |
| Level II | Sets up and calibrates equipment, interprets and evaluates results against codes, standards and specifications, organizes and reports results, and guides Level I staff and trainees | Writing and approving procedures; establishing techniques |
| Level III | Develops, qualifies and approves procedures and techniques; interprets codes, standards and specifications; selects methods; runs the examinations; and normally writes or approves the written practice | Nothing above it, though the employer remains responsible for the program |
One point is often reported wrongly: under SNT-TC-1A a Level I can make specific accept/reject decisions, as long as they follow written instructions and work under a Level II or III. What a Level I can't do is interpret a code or decide how a criterion applies. The rule that a Level 1 does not interpret results comes from ISO 9712, not SNT-TC-1A.
The 2025 addendum, as summarized by training providers, formalizes a Responsible Level III: the designated Level III with overall responsibility for the employer's program. An employer without its own Level III can use an outside Level III, which the written practice should name.
The original article also said a Level III "requires completing Level 1 and 2 first." Published summaries of the Level III routes describe them by education and years of Level II-comparable experience in the method, not by holding Level I and II certificates first.
Key takeaway: Level I follows instructions, Level II interprets against the code, and Level III decides how the method is applied.
How many training and experience hours does SNT-TC-1A recommend for UT, MT and PT?
Published summaries of SNT-TC-1A 2024 recommend, for a high-school graduate, 40 training hours for UT Level I, 12 for MT Level I and 4 for PT Level I, with method and total NDT experience hours set separately for each level. The Level II figures are in addition to Level I.
| Method | Level | Training hours | Experience in the method (h) | Total NDT experience (h) |
|---|---|---|---|---|
| Ultrasonic (UT) | I | 40 | 210 | 400 |
| Ultrasonic (UT) | II (additional) | 40 | 630 | 1,200 |
| Ultrasonic (UT) | Direct to Level II (sum) | 80 | 840 | 1,600 |
| Magnetic particle (MT) | I | 12 | 70 | 130 |
| Magnetic particle (MT) | II (additional) | 8 | 210 | 400 |
| Magnetic particle (MT) | Direct to Level II (sum) | 20 | 280 | 530 |
| Liquid penetrant (PT) | I | 4 | 70 | 130 |
| Liquid penetrant (PT) | II (additional) | 8 | 140 | 270 |
| Liquid penetrant (PT) | Direct to Level II (sum) | 12 | 210 | 400 |
Sources: Trace NDT's 2024 SNT-TC-1A summary (secondary) for the per-level figures, and Atlantis NDT's 2020-edition comparison, whose cumulative MT and PT figures (20/280/530 and 12/210/400) match the sums. The licensed Table 6.3.1A governs; a Level III should confirm it before relying on these numbers.
Three points are commonly misread:
- The hours aren't split into "classroom" and "practical" bands. The original article's table (Level I 40–80 hours, Level II 120–400 hours, Level III "1,000+ hours", with theory and practical percentages) doesn't match the structure of SNT-TC-1A at all, which sets hours by method and level.
- Total NDT experience means NDT in any method. A trainee's PT hours count toward their MT total-NDT column, but not toward the MT method column.
- The table is a recommendation. Summaries note that the employer's written practice sets the figures the technician is actually held to, and the table's notes allow adjustment for some education routes.
For how the UT figures play out for a single technician, see our guides to ultrasonic testing Level 1 and ultrasonic testing Level 2. Those pages cover UT careers in depth; this page covers the program that sits behind them.
Key takeaway: UT needs roughly six times the MT and PT experience, and every Level II figure is on top of Level I.
What examinations does SNT-TC-1A require?
Levels I and II take a general written exam, a specific written exam and a practical exam; published summaries give passing grades of 70% on each written exam, 80% on the practical and 80% on the composite.
| Exam | What it tests | Recommended minimum |
|---|---|---|
| General (written) | Principles of the method | 40 questions for common methods at Levels I and II (Table 8.3.3, as summarized) |
| Specific (written) | The employer's equipment, procedures, codes and acceptance criteria | 20 questions for common methods |
| Practical | Handling the equipment and testing at least one flawed specimen, scored against a checklist | At least 10 checkpoints |
| Passing grades | Each written exam ≥70%; practical ≥80%; composite ≥80% | Composite is a simple average in published summaries |
| Retake | A failed exam may be retaken | After at least 30 days, or after additional training set by the Level III |
A Level III takes a Basic exam once (covering general NDT knowledge across methods), then a Method exam and a Specific exam for each method, and in most cases a practical. Summaries report that an employer may accept a current ASNT NDT Level III certificate in place of the Basic and Method exams if its written practice allows it.
The Level III is responsible for the examinations, and the 2024 edition (as summarized) adds training for exam administrators and documentation of outside examination suppliers.
Key takeaway: passing each exam is not enough; the composite must also reach 80%.
What are the SNT-TC-1A vision requirements?
Published summaries of SNT-TC-1A 2024 recommend an annual near-vision test, reading at least Jaeger No. 2 (or equivalent) at not less than 12 inches, in at least one eye, with or without correction, plus a color-contrast test. The 2024 edition adds that acuity-improving eye drops may not be used for the test.
| Vision test | Requirement (as summarized) | Interval |
|---|---|---|
| Near vision | Jaeger No. 2 or equivalent at ≥12 in. (305 mm), at least one eye, natural or corrected | Annually |
| Color contrast | Ability to distinguish the colors or shades of gray used in the method | Sources disagree: at initial certification and every 5 years (Trace NDT, 2024), or annually (other guides) |
| Eye drops | Acuity-improving drops not allowed | 2024 change |
The color-contrast interval is the one point where secondary sources conflict, so follow your written practice and have a Level III check it against the 2024 text. Central schemes differ: ASNT 9712 uses the Jaeger J1 chart, which is a stricter line.
The original article left out vision checks entirely. They are among the most frequently audited items in a written practice, because a lapsed vision exam suspends the technician's ability to work even when the certification itself is current.
Key takeaway: the near-vision check runs on its own annual clock, separate from the 5-year certification.
How does SNT-TC-1A recertification work?
SNT-TC-1A recommends a maximum recertification interval of 5 years for Levels I, II and III, counted from the date the certifying authority signs the certification. Recertification is by evidence of continuing satisfactory performance, or by re-examination in whatever parts the Level III decides are needed.
The original article described "annual renewal fees", "continuing education credits" and "renewal applications" to a certifying body. None of that is in SNT-TC-1A. There is no outside body to apply to: the employer recertifies its own staff under its written practice. Fees and credits belong to central programs such as ASNT 9712 or the ASNT NDT Level III, not to employer certification.
A certification under SNT-TC-1A also ends when the technician leaves the employer, because it belongs to that employer's program. A new employer can review the person's records and recertify them, but it signs its own certification.
Key takeaway: at most 5 years between recertifications, done by the employer, with no renewal fee to ASNT.
How does SNT-TC-1A compare with CP-189 and ASNT 9712?
SNT-TC-1A and ANSI/ASNT CP-189 are both employer certification, but CP-189 is a mandatory standard while SNT-TC-1A is a recommended practice; ASNT 9712 is a third-party program in which ASNT itself examines and certifies. ASNT 9712 has replaced the old ASNT Central Certification Program (ACCP).
ASNT's standards page says CP-189 (2024) "Establishes minimum requirements for employer-based NDT personnel certification, building on SNT-TC-1A." Because CP-189 is written as requirements, an employer can't relax its minimums the way an SNT-TC-1A written practice can. Secondary sources and forum posts also report that CP-189 requires the employer's Level III to hold an ASNT NDT Level III certificate; check the standard before relying on that.
On ASNT 9712, ASNT's certification site states: "The ASNT 9712 Certification Program has replaced the ASNT Central Certification Program (ACCP)." ASNT reports that the last active ACCP certifications expire in 2029.
| SNT-TC-1A (2024) | ANSI/ASNT CP-189 (2024) | ASNT 9712 (ISO 9712:2021 based) | 49 CFR 213.238 (rail flaw detection) | |
|---|---|---|---|---|
| Type | Recommended practice | ANSI standard | Third-party certification program | Federal regulation |
| Who certifies | Employer | Employer | ASNT | Employer authorizes "qualified operators" |
| Levels | Trainee, I, II, III | I, II, III | II and III only (no Level 1) | None |
| Can the employer change the numbers? | Yes, in its written practice | No, minimums are mandatory | No | Sets only its own minimums |
| Training and experience | Hours by method and level (table above) | Not verified for this article | UT Level II: 18 days training, 180 days experience; MT and PT Level II: 5 days training, 60 days experience; a day is at least 7 hours | Documented training program; ≥160 h supervised rail flaw detection experience |
| Near vision | Jaeger No. 2 at ≥12 in., annually (summaries) | Covered; detail not verified | Jaeger J1 chart | Not specified |
| Validity | Recommended maximum 5 years | Check the standard | Renewal every 5 years by re-exam or credits | Reevaluation per the employer's program |
| Portable between employers? | No | No | Yes, the certificate is the person's | No |
Sources: ASNT standards page; ASNT 9712 Level II requirements page; P. Lang, Understanding ASNT 9712, ASNT, August 2026; 49 CFR 213.238.
An ASNT 9712 certificate doesn't by itself authorize work under an employer's procedures; the employer still decides, in its written practice, how it credits a central certificate and what specific exam or authorization it adds.
Key takeaway: choose SNT-TC-1A for flexibility, CP-189 when the contract demands mandatory minimums, and ASNT 9712 when the certificate must travel with the person.
Where do codes call for SNT-TC-1A: AWS D1.1, ASME and FRA?
AWS D1.1 and ASME Section V both point to SNT-TC-1A for NDT personnel; FRA's rail flaw detection rule, 49 CFR 213.238, does not mention SNT-TC-1A at all. Always check the code edition named in the contract, because the referenced SNT-TC-1A edition changes with it.
| Code or rule | What it calls for | Confidence |
|---|---|---|
| AWS D1.1 (structural steel welding) | NDT personnel other than visual qualified to the current edition of SNT-TC-1A: a Level II, or a Level I working under a Level II. Quotations of older editions add that the Level III who certifies them must hold an ASNT Level III certificate or have passed the SNT-TC-1A Level III exams, and later editions may also accept other schemes. This is separate from CWI visual inspection | Med (code quotations on the AWS forum; D1.1 is paywalled, so check the clause in your edition) |
| ASME BPVC Section V, Article 1, T-120 | ASME administratively approved SNT-TC-1A (2024) in December 2024 for reference in the 2025 Section V, para. T-120(e)(1). The approved version is "without Addendum" and incorporates the errata; per a pending interpretation, written practices must meet the errata but need not meet the May 2025 addendum | High (secondary: HSB Pressure Points, Dec 2025) |
| ASTM guides (e.g. E709-21 for MT) | Scope 1.5: personnel "should be qualified and certified in accordance with ASNT Recommended Practice No. SNT-TC-1A, ANSI/ASNT Standard CP-189, NAS 410, or as specified in the contract or purchase order" | High (ASTM store scope text) |
| 49 CFR 213.238 (FRA, rail flaw detection) | A provider's documented training program, written authorization for four duties, at least 160 hours of supervised rail flaw detection experience, a proficiency demonstration for each type of equipment, reevaluation and records. No levels, and no reference to SNT-TC-1A or ASNT | High (Cornell LII; the 2026 text contains no "ASNT" or "SNT") |
The FRA rule is the one most often misstated. Section 213.238(a) reads:
"Each provider of rail flaw detection shall have a documented training program in place and shall identify the types of rail flaw detection equipment for which each equipment operator it employs has received training and is qualified." (49 CFR 213.238(a))
A UT Level II under SNT-TC-1A is therefore not automatically a 213.238 qualified operator, and a 213.238 operator holds no SNT-TC-1A level. A railroad or transit agency can still require SNT-TC-1A certification in its contract, on top of 213.238, and some rail RFPs do. For how 213.238 fits with the testing intervals, see our guide to 49 CFR 213.237.
Key takeaway: for structural and pressure work the code names SNT-TC-1A; for rail flaw detection the federal hook is 213.238, and SNT-TC-1A comes only from the contract.
Worked example: an MT and PT technician's path to Level II
A new technician who logs 24 hours of MT and 16 hours of PT each week reaches the SNT-TC-1A experience minimums for both MT Level II and PT Level II in week 14. This uses the 2024 figures as summarized above, and assumes the employer's written practice adopts them unchanged.
Inputs: a high-school graduate joins a structural steel fabricator's NDT department to inspect welds to AWS D1.1. They log 40 hours of supervised NDT a week: 24 hours of MT and 16 hours of PT. They complete a 20-hour MT course and a 12-hour PT course in their first weeks. The written practice credits each hour to one method only.
Step 1: experience
| Requirement (direct to Level II) | Needed | Weekly rate | Weeks to meet | Hours logged at week 14 |
|---|---|---|---|---|
| MT method hours | 280 | 24 | 280 ÷ 24 = 11.7, so week 12 | 14 × 24 = 336 |
| MT total NDT hours | 530 | 40 | 530 ÷ 40 = 13.25, so week 14 | 14 × 40 = 560 |
| PT method hours | 210 | 16 | 210 ÷ 16 = 13.1, so week 14 | 14 × 16 = 224 |
| PT total NDT hours | 400 | 40 | 400 ÷ 40 = 10, so week 10 | 560 |
The later figure in each method governs. MT is held back by the 530 total-NDT hours (week 14), and PT by its 210 method hours (also week 14). Training hours (20 MT, 12 PT) are counted separately from experience.
Step 2: the MT Level II exams
| Exam | Score | Minimum | Result |
|---|---|---|---|
| General (written) | 78% | 70% | Pass |
| Specific (written) | 72% | 70% | Pass |
| Practical | 85% | 80% | Pass |
| Composite | (78 + 72 + 85) ÷ 3 = 78.3% | 80% | Fail |
Every individual exam passed, but the composite missed 80%. Under the retake rule as summarized, the technician waits at least 30 days or completes extra training set by the Level III, then retakes.
On the retake the scores are 82%, 76% and 88%. The composite is (82 + 76 + 88) ÷ 3 = 246 ÷ 3 = 82.0%, a pass.
Step 3: vision and dates
The technician passed the near-vision test on June 10, 2026, and the Level III signs the MT and PT Level II certifications on June 24, 2026. Summaries say vision exams and certifications expire on the last day of the month they fall due. So:
- the next near-vision test is due by June 30, 2027, and every year after;
- recertification is due by June 30, 2031, at most 5 years after signing.
Under 213.238, the same person would need a separate documented program and 160 supervised hours on rail flaw equipment before testing rail; the MT and PT certifications don't count toward it.
Key takeaway: plan around the slowest column, and check the composite score, not just each exam.
What doesn't SNT-TC-1A cover?
SNT-TC-1A sets out how to qualify people; it doesn't qualify procedures, set acceptance criteria, or certify anyone on its own. Its limits matter when you write a contract or audit a supplier:
- It isn't a certification. A course certificate or a "certified to SNT-TC-1A" card from a training school is not an SNT-TC-1A certification. Only the employer's signed record under its written practice is.
- Its numbers are recommendations. Hours, question counts and passing grades are recommended values. Read the supplier's written practice to see what it actually adopted.
- It doesn't travel with the person. A new employer has to recertify. Only a central program (ASNT 9712, ASNT NDT Level III) is personal.
- It sets no acceptance criteria. Whether a weld or rail indication is rejectable comes from the code (AWS D1.1, ASME, the railroad's procedures), not from SNT-TC-1A.
- It doesn't satisfy 49 CFR 213.238. Rail flaw detection operators need the FRA rule's own program, 160 supervised hours and equipment-type authorization.
- It isn't ISO 9712. Buyers outside the US, or contracts that call for ISO 9712, need third-party certification such as ASNT 9712 or PCN.
- The edition matters. ASME's 2025 Section V references SNT-TC-1A (2024) without the addendum, and older code editions reference older SNT-TC-1A editions.
- This page relies on summaries. The 2024 text is sold by ASNT and was not read for this article; the hours, exam and vision figures come from published secondary summaries and need a Level III check against the licensed document.
How EMA Industries applies this
EMA Industries provides NDT Level III services from Southern California, mobilizing nationwide, alongside ultrasonic rail flaw testing, rail weld inspection, and AWS D1.1 structural weld UT, MT and PT. For a buyer, the practical checks are to ask a supplier for its written practice, current certifications and vision records for each technician, and, for rail, its 213.238 training records. To discuss written-practice reviews or NDT program support, see our ultrasonic examination services or contact EMA Industries.
Related reading: AWS D1.1 weld inspection criteria, ASME weld ultrasonic inspection, magnetic particle examination, NDT for welding inspection and our rail inspection RFP guide.
Frequently asked questions
What is the difference between ASNT and SNT-TC-1A?
ASNT is the society that publishes SNT-TC-1A; SNT-TC-1A is its recommended practice for employer certification. ASNT doesn't certify anyone under SNT-TC-1A. It certifies people only through its own central programs, the ASNT NDT Level III and ASNT 9712.
Can I get SNT-TC-1A certified on my own, without an employer?
Not under SNT-TC-1A, because the certification is issued by an employer under its written practice. You can complete training and log experience on your own, and you can seek a central certificate such as ASNT 9712 (Level II and III) or the ASNT NDT Level III, which belong to you rather than to an employer.
How often must SNT-TC-1A certifications be renewed?
SNT-TC-1A recommends recertification at least every 5 years, by evidence of continued satisfactory performance or by re-examination, as the employer's written practice sets out. The near-vision test is separate and is recommended annually.
Does a Level III have to hold Level I and II first?
The published Level III routes are based on education and years of experience at a level comparable to Level II in the method, plus the Basic, Method and Specific exams. Holding Level I and II certificates first is a common career path, but the summaries don't describe it as a prerequisite.
Do FRA rules require SNT-TC-1A for rail flaw testing?
No. 49 CFR 213.238 sets its own qualified-operator requirements, including a documented training program and at least 160 hours of supervised experience, and it doesn't mention SNT-TC-1A or ASNT. A railroad can still require SNT-TC-1A certification by contract.
Sources
- ASNT Standards and Publications: SNT-TC-1A (2024, with Addendum), ANSI/ASNT CP-189 (2024), CP-105 (2024) and CP-9712 (2023), ASNT
- Advisory on SNT-TC-1A Certification Practices and Use of ASNT Credentials, P. Lang, ASNT, June 11, 2026
- Explaining Employer-Based Certification Programs, J. Bennett, ASNT, October 29, 2020
- ASNT 9712 Level II requirements, ASNT Certification
- Understanding ASNT 9712, P. Lang, ASNT, August 2026
- Don't miss out on ASME Code errata and notices, A. Garbolevsky, HSB Pressure Points, December 2025
- 49 CFR 213.238, Qualified operator, eCFR; text read on Cornell LII, October 2026
- ASTM E709-21, Standard Guide for Magnetic Particle Testing, scope 1.5, ASTM International store listing
- SNT-TC-1A guide (2024 edition summary), Trace NDT (secondary; training provider)
- NAS 410 vs SNT-TC-1A, Atlantis NDT (secondary; 2020 edition figures)