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The Fundamental Difference: Who Certifies?
This is the single most important distinction between the two systems. ASNT SNT-TC-1A is an employer-based certification system — your employer sets the qualification requirements (within SNT-TC-1A guidelines), trains you, examines you, and certifies you. The certification is company-specific and does not follow you to another employer.
ISO 9712 (and its UK implementation, PCN — Personnel Certification in NDT) is a third-party central certification system. An independent certification body (BINDT, CICPND, etc.) examines and certifies you. That certification is portable — it belongs to you, not your employer, and is accepted internationally.
Comparison Table: ISO 9712 vs ASNT SNT-TC-1A
| Feature | ASNT SNT-TC-1A | ISO 9712 / PCN |
|---|---|---|
| Certification authority | Employer | Independent third-party body |
| Certificate portability | Company-specific, not portable | Portable — belongs to individual |
| International recognition | US/Canada dominant, some global | Widely recognised globally (Europe, Middle East, Asia) |
| Qualification levels | Level I, II, III | Level 1, 2, 3 (same concept, different numbering convention) |
| Level III exam | Employer OR ASNT central exam | Mandatory central exam by certifying body |
| Recertification interval | 5 years (per SNT-TC-1A 2020) | 5 years (ISO 9712:2021) |
| Eye examination | Jaeger J1 at 12 inches | Near vision: Jaeger J1 or N4.5; colour vision if required |
| Sector qualification | General only (by default) | Sector-specific for advanced methods (weld, cast, wrought, etc.) |
| Hearing requirement | Not required | Required for AE examination |
| Written practice | Required by employer | Handled by certification body scheme rules |
How Each Standard Affects Your NDT Procedure
When Your Procedure References SNT-TC-1A
Your procedure must include a reference to your company's Written Practice document number. The procedure should state: "Personnel performing examinations under this procedure shall hold a minimum Level II certification in [method] per [Company] Written Practice [doc. no.], Rev. [X], which conforms to ASNT SNT-TC-1A, [edition]."
The Written Practice itself must be compliant with SNT-TC-1A and must be available for review.
When Your Procedure References ISO 9712
The procedure should state: "Personnel performing examinations shall hold a minimum ISO 9712 Level 2 certification in [method], certified by an accredited certification body."
For advanced methods (PAUT, TOFD, ECT), the procedure should also specify the required sector/application qualification. ISO 9712 uses specific sector codes that define the scope of the personnel's qualification — e.g., "Level 2 UT Welds" does not automatically qualify someone for PAUT or for pressure vessel base material examination.
When Both Are Referenced
Many clients and codes accept either standard, stating: "Personnel shall be qualified and certified in accordance with ASNT SNT-TC-1A or ISO 9712, as applicable." In this case, both systems are acceptable alternatives — your procedure should clearly state which one applies to your company.
Level III Differences — Critical for Procedure Approval
Both systems require a Level III (or Level 3) engineer to review and approve NDT procedures. The key practical difference:
- SNT-TC-1A Level III: Employer-certified, or may hold an ASNT Central Certification (ACCP — ASNT Central Certification Program). The ACCP exam is optional but provides independent verification of competence.
- ISO 9712 Level 3: Always independently examined and certified. Level 3 is the highest level and includes responsibility for procedure approval and personnel oversight.
For your procedures, the reviewing Level III must hold the appropriate certification for the method being reviewed. A UT Level III cannot formally approve an RT procedure unless they also hold RT Level III (or the applicable equivalent under ISO 9712).
Which Standard Should Your Procedure Reference?
Use the standard required by your client or the applicable code:
- ASME, API, AWS in North America: Typically call up SNT-TC-1A or CP-189
- EN ISO standards, European client specs: Typically require ISO 9712
- Offshore oil & gas (global): Often require ISO 9712 PCN Level 2/3 minimum
- Aerospace (AS9100): May require NAS 410 or EN 4179 in addition to or instead of SNT-TC-1A
Is Your Personnel Qualification Section Compliant?
NDTVerify checks your procedure's personnel qualification section against both ASNT SNT-TC-1A and ISO 9712 requirements — and flags missing elements with exact corrective actions.
Review Your Procedure — $20