In North America, most organizations qualify their NDT personnel using one of two ASNT documents: SNT-TC-1A (Recommended Practice) or CP-189 (Standard for Qualification and Certification). While both aim to ensure competent NDT personnel, they differ significantly in approach, prescriptiveness, and industry acceptance.
\nChoosing the right standard affects your audit outcomes, client acceptance, regulatory compliance, and the portability of your personnel certifications. This guide provides a detailed comparison to help you make an informed decision.
\n\nFull title: Recommended Practice No. SNT-TC-1A — Personnel Qualification and Certification in Nondestructive Testing
\nType: Recommended practice (not a mandatory standard)
\nFirst published: 1966
\nCurrent edition: 2020
\nSNT-TC-1A is the most widely used NDT personnel qualification document in North America. As a \"recommended practice,\" it provides guidelines that employers adapt through their own written practices. The employer retains significant flexibility in how they implement the recommendations.
\n\nFull title: ASNT Standard CP-189 — Standard for Qualification and Certification of Nondestructive Testing Personnel
\nType: National consensus standard (ANSI-approved)
\nFirst published: 1991
\nCurrent edition: 2020
\nCP-189 is a more prescriptive standard that mandates specific requirements rather than providing recommendations. It was developed to address industry concerns about inconsistent implementation of SNT-TC-1A across different employers.
\n\n| Feature | SNT-TC-1A | CP-189 |
|---|---|---|
| Document type | Recommended practice | National standard (ANSI) |
| Language | \"Should\" (advisory) | \"Shall\" (mandatory) |
| Employer flexibility | High | Limited |
| Examination source | Employer-developed or ASNT | ASNT exams required |
| Written practice | Required, employer-customized | Required, must meet standard |
| Training documentation | Recommended | Mandatory with specific records |
| Certification portability | Employer-specific only | More portable (standardized exams) |
| Vision requirements | Near-vision acuity, annual | Near-vision acuity, annual + documented |
| Level III certification | Employer-administered exams | ASNT exams mandatory |
SNT-TC-1A: Requires general, specific, and practical examinations, but the employer develops or selects the exams. Exam content and passing criteria are determined by the employer's written practice.
\nCP-189: Requires ASNT-administered examinations for the general and specific portions. The employer may only develop the practical examination. This ensures consistent exam quality across organizations.
\nImpact: CP-189's use of standardized ASNT exams provides greater confidence in personnel competence and makes certifications more meaningful when reviewed by clients or auditors.
\n\nSNT-TC-1A: Provides recommended training hours per method and level as guidelines. The employer may adjust these based on the candidate's education and experience. Training documentation is recommended but the format is flexible.
\nCP-189: Specifies mandatory minimum training hours that cannot be reduced. Training must be formally documented with instructor qualifications, course content, and attendance records.
\n\nBoth documents require employers to maintain a written practice that documents their qualification program. However:
\nSNT-TC-1A: The written practice can deviate from the recommended practice as long as deviations are documented and justified. This provides flexibility but can lead to inconsistent implementation.
\nCP-189: The written practice must meet all mandatory requirements of the standard. Deviations are not permitted for mandatory (\"shall\") requirements.
\n\nSNT-TC-1A: Recommends maintaining certification records but provides limited guidance on format and content.
\nCP-189: Mandates specific certification record contents including training documentation, exam results, experience verification, vision test results, and authorized signature.
\n\nSNT-TC-1A: Recommends recertification at intervals not to exceed 5 years for Level I and II, and 5 years for Level III. Recertification methods are flexible.
\nCP-189: Requires recertification at intervals not exceeding 5 years. Re-examination is mandatory—experience alone does not qualify for recertification.
\n\nASME Section V accepts both SNT-TC-1A and CP-189 for personnel qualification. The referencing construction code or client specification typically determines which is required.
\n\nRegardless of which standard you choose, these are the most common audit findings:
\nAtlantis NDT provides Level III consulting services for personnel qualification programs under both SNT-TC-1A and CP-189:
\nNeed the fundamentals first? See our SNT-TC-1A certification overview for what the employer-based model actually is and how it stacks up against CP-189, ISO 9712, ASNT 9712, and Canada's CGSB-derived scheme.
\nContact us for expert guidance on your NDT personnel qualification program.
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