12.1 SNT-TC-1A Overview and Written Practice

ASNT NDT Level III Basic Examination Exam

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1 Introduction & Exam Overview

1.1 Current Exam Facts 1.2 Level III Role and Certification Path 1.3 Eligibility, Fees, Scheduling, and Retakes 1.4 Study Strategy and Exam-Day Approach

2 Chapter 2: Materials Fundamentals for NDT

2.1 Ferrous Metals and Iron-Carbon Phases 2.2 Non-Ferrous Metals and Alloys 2.3 Mechanical Properties and Crystal Structure

3 Chapter 3: Manufacturing Processes

3.1 Casting Processes and Cast Discontinuities 3.2 Forging, Rolling, and Forming 3.3 Extrusion, Drawing, and Machining 3.4 Heat Treatment Effects

4 Chapter 4: Welding and Joining Processes

4.1 Fusion Welding Processes 4.2 Weld Metal and HAZ Discontinuities 4.3 Brazing, Soldering, and Mechanical Joining

5 Chapter 5: Discontinuity Classification

5.1 Inherent Discontinuities 5.2 Processing Discontinuities 5.3 Service Discontinuities

6 Chapter 6: Specific Discontinuity Types

6.1 Cracks and Fracture Modes 6.2 Porosity, Inclusions, and Lack of Fusion 6.3 Laminations, Seams, Laps, and Undercut 6.4 Relevant vs Non-Relevant Indications

7 Chapter 7: NDT Method Selection and Inspection Planning

7.1 Method Selection Principles 7.2 Surface vs Volumetric Methods 7.3 Inspection Planning and Flaw Expectations

8 Chapter 8: Ultrasonic and Radiographic Testing

8.1 Ultrasonic Testing Principles and Applications 8.2 UT Limitations, Calibration, and Evaluation 8.3 Radiographic Testing Principles and Applications 8.4 RT Limitations, Image Quality, and Safety Basics

9 Chapter 9: Magnetic Particle, Liquid Penetrant, and Visual Testing

9.1 Magnetic Particle Testing 9.2 Liquid Penetrant Testing 9.3 Visual Testing

10 Chapter 10: Electromagnetic, Leak, Acoustic Emission, and Infrared Testing

10.1 Electromagnetic / Eddy Current Testing 10.2 Leak Testing 10.3 Acoustic Emission Testing 10.4 Thermal / Infrared Testing

11 Chapter 11: Specialty Methods and Method Comparison

11.1 Neutron Radiography 11.2 Magnetic Flux Leakage 11.3 Method Comparison and Supplemental Examinations

12 Chapter 12: SNT-TC-1A Recommended Practice

12.1 SNT-TC-1A Overview and Written Practice 12.2 SNT-TC-1A Training and Experience 12.3 SNT-TC-1A Examinations and Recertification

13 Chapter 13: CP-189 Standard Practice

13.1 CP-189 Overview and Scope 13.2 CP-189 Mandatory Requirements 13.3 SNT-TC-1A vs CP-189 Comparison

14 Chapter 14: CP-105 and NDT Training Programs

14.1 CP-105 Purpose and Topical Outlines 14.2 Developing and Approving NDT Training 14.3 OJT, Mentoring, and Instructor Oversight

15 Chapter 15: Building and Managing Certification Programs

15.1 Building Qualification and Certification Programs 15.2 Administering Examinations and Evaluating Competency 15.3 Program Audits and Managing Certifications

16 Chapter 16: Codes, Standards, Procedures, and Quality

16.1 Interpreting Codes, Standards, and Specifications 16.2 Developing and Approving NDT Procedures 16.3 Acceptance Criteria and Quality Control 16.4 External Audits and Inspection Documentation

12.1 SNT-TC-1A Overview and Written Practice

Key Takeaways Explain This Topic AI

SNT-TC-1A is an ASNT recommended practice for employer-based qualification and certification of NDT personnel—not a federal regulation and not a central-certification scheme by itself.

The employer’s Written Practice is the controlling local document that adopts and tailors SNT-TC-1A guidelines for training, experience, examinations, vision, and recertification.

For ASNT NDT Level III Basic exams after 1 January 2026, study the 2024 edition of SNT-TC-1A (replacing the 2020 edition as the recommended reference).

Level I works under supervision with limited evaluation authority; Level II sets up and calibrates equipment, interprets results, and may supervise Level I; Level III owns procedures, training design, examinations, and technical program leadership.

Distinguish employer certification under an SNT-TC-1A Written Practice from ASNT Central Certification: the Basic exam tests knowledge of both frameworks, but they serve different authority models.

Last updated: July 2026

12.1 SNT-TC-1A Overview and Written Practice

Quick Answer: SNT-TC-1A is an ASNT recommended practice that gives employers guidelines to build their own qualification and certification program for NDT personnel. It is not a mandatory regulation by itself. The employer’s Written Practice is the controlling local document. For ASNT NDT Level III Basic exams after 1 January 2026 , prioritize the 2024 edition (it replaces the 2020 edition as the recommended reference). Always verify exact tables and wording in the published document —do not rely on memorized hour cells from older editions or secondary notes.

This chapter starts the personnel-qualification block of the Basic exam. Domain 1 (NDT Certification) and Domain 3 (NDT Training) both lean heavily on how employer programs work. If you confuse recommended practice with mandatory standard , or confuse employer certification with ASNT Central Certification , you will miss high-yield items even when your method physics is solid.

What SNT-TC-1A Is—and Is Not

SNT-TC-1A ( Personnel Qualification and Certification in Nondestructive Testing ) is published by ASNT as a recommended practice . Its stated objective is to provide guidelines employers can use to establish their own programs for the qualification and certification of NDT personnel.

Read those words carefully for the exam:

Term Meaning on the Basic exam
Recommended practice Guidance the employer may adopt and tailor; not self-enforcing law
Qualification Demonstrated skill, training, experience, and examination readiness
Certification Written testimony by the employer that an individual has met the Written Practice
Employer-based The company (or organization) is the certifying authority for its program

What SNT-TC-1A is not :

Not a federal regulation enforced by OSHA or another agency on its own authority

Not (by itself) an ANSI consensus standard with inviolable mandatory minimums—that role is closer to CP-189 , covered in the next chapter

Not an ISO central-certification scheme that automatically certifies individuals independent of an employer
Not a weld acceptance code or a method procedure for performing inspections

Customers, codes, or contracts may invoke SNT-TC-1A and require an employer program “in accordance with” it. Once invoked, the Written Practice and customer requirements become binding for that work—but the document itself remains framed as a recommended practice that the employer implements through its Written Practice.

Scope and Purpose

SNT-TC-1A addresses personnel —who may be trained, examined, certified, and recertified in NDT methods at Level I, II, and III. It does not set acceptance criteria for discontinuities in hardware. It does not replace ASNT’s own central certification products or method exam outlines.

Typical scope elements candidates should expect on Basic:

Methods covered by the employer program (for example PT, MT, UT, RT, VT, ET, and others the employer uses)
Levels of qualification and the general duties associated with each level
Training, experience, and examination frameworks
Vision requirements
Certification and recertification control
Responsibilities of the NDT Level III and of management

When an item asks “what is the purpose of SNT-TC-1A?”, the safest answer points to employer guidelines for qualification and certification of NDT personnel —not product acceptance, not equipment calibration tables, and not government licensing.

The Written Practice: The Real Controlling Document

Under SNT-TC-1A (and likewise under CP-189), the employer establishes a Written Practice for the control and administration of NDT personnel training, examination, and certification . On the Basic exam, if a question asks which document establishes the employer’s specific qualification and certification practices, the answer is almost always the employer’s Written Practice —not the SNT-TC-1A foreword alone, not a Level III wallet card, and not a test-center candidate handbook.

What a Written Practice should address

A well-built Written Practice typically covers:

Methods and techniques within the program scope
Qualification and certification requirements by method and level
Training content and hour expectations (often tied to SNT-TC-1A tables and CP-105 topical outlines)
Experience requirements and how experience is documented
Examination types, administration, grading, and re-examination rules
Vision examination requirements and intervals
Certification records, signatures, and control of certificates
Recertification intervals and acceptable recertification methods
Use of outside agencies or outside Level IIIs, if any
Suspension, revocation, and reinstatement concepts as the employer defines them

What a Written Practice is not responsible for: manufacturing welding electrodes, writing product design codes, or replacing the governing fabrication code’s acceptance criteria. Those traps appear when options mix personnel documents with product documents .

Why Level IIIs care so much about the Written Practice

As a Level III candidate, you are the person who will be asked in an audit: “Show me where your program requires X.” The answer lives in the Written Practice, supported by training records, exam records, experience logs, vision records, and procedure approvals. SNT-TC-1A gives you the skeleton; the Written Practice is the living program you defend.

Edition Awareness for the Basic Exam (2024 vs 2020)

ASNT’s Basic recommended references move with the editions. For exams after 1 January 2026 , prioritize SNT-TC-1A 2024 and CP-189 2024 ; they replace the 2020 editions for that exam window. If your notes, employer program, or older study books still quote 2020 language, mark them for reconciliation against the current published editions before exam day.

Practical study rule:

Learn the concepts (recommended practice, Written Practice, levels, exam types, vision, recertification philosophy).

Verify numeric tables (training hours, experience times, any revised criteria) in the current published SNT-TC-1A —do not invent or force-memorize table cells from secondary sources if you have not checked the official document.

Know that customer/code invocation may force more restrictive rules than the minimum recommendations in SNT-TC-1A.

Level I, Level II, and Level III Definitions (Exam Mental Model)

SNT-TC-1A-style programs define three classic levels. Memorize the authority gradient , not just job titles.

Level I

A Level I is qualified to perform specific calibrations, specific NDT, and specific evaluations for acceptance or rejection according to written instructions and under the guidance or supervision expected by the Written Practice. Level I does not independently select techniques, write procedures, or own the program. Think: perform defined tasks under control .

Level II

A Level II is qualified to set up and calibrate equipment, conduct examinations, interpret and evaluate results with respect to applicable codes, standards, and specifications, organize and report results, and exercise the method-level judgment the Written Practice assigns. Level II may provide on-the-job training and guidance for Level I personnel. Think: independent method application within approved procedures .

Level III

A Level III is qualified to develop, qualify, and approve procedures; establish and approve techniques; interpret codes, standards, specifications, and procedures; designate the particular NDT methods, techniques, and procedures to be used; and train, examine, and recommend personnel for certification as defined by the employer’s program. Think: technical ownership of the system .

Dimension Level I Level II Level III
Procedures Follow written instructions Apply approved procedures Develop, qualify, approve
Technique selection Limited / instructed Within method competence Designates methods and techniques
Interpretation Per limited instructions Evaluates vs codes/specs Leads interpretation; code interface
Training/exams Receives training May train/guide Level I Designs/oversees training and exams
Program Participant Key executor Program technical authority
Role of the NDT Level III in establishing the program

Under an SNT-TC-1A-based program, a qualified Level III is typically responsible for the technical adequacy of the NDT program: procedure approval, examination content and administration (or approval of exams), training design alignment, and interpretation leadership. Management still owns employment decisions and often signs certification records as the employer’s authority—but technical content quality is a Level III problem.

Employers may use an outside agency Level III when that arrangement is allowed and documented in the Written Practice. The Basic exam likes this distinction: the employer remains the certifying authority; the outside Level III supplies technical qualification support under controlled terms.

Employer SNT-TC-1A Programs vs ASNT Central Certification

Keep these two systems separate in your head:

Employer program (SNT-TC-1A-based)
Certifying authority: employer
Controlling document: Written Practice
Certificate proves the person met that employer’s requirements for that employer’s work

Changing employers often means new certification under the new employer’s Written Practice (with possible credit for prior training/experience as that practice allows)

ASNT Central Certification (for example ASNT NDT Level III)
Certifying authority: ASNT (central body)
Examinations: ASNT Basic + Method (and program rules for eligibility, fees, recertification)
Credential is portable evidence of individual competence under ASNT’s scheme

Employers may recognize ASNT Level III credentials inside their Written Practice, but ASNT certification does not automatically equal employer certification unless the Written Practice says so

The Basic exam itself is part of the ASNT Central Certification path, yet it tests whether you understand employer-based frameworks like SNT-TC-1A and CP-189. That is not a contradiction: Level IIIs must be fluent in the systems they will run for employers and the systems that credential individuals nationally.

High-Yield Exam Traps for This Section
Calling SNT-TC-1A a regulation or mandatory standard when the correct characterization is recommended practice
Saying ASNT (or Pearson VUE) is the employer-program certifying authority under SNT-TC-1A

Treating the SNT-TC-1A document as if it alone “certifies” technicians without a Written Practice and employer action

Confusing Level II evaluation authority with Level III procedure ownership
Using 2020-edition assumptions for a post–1 January 2026 Basic sitting without checking the 2024 reference set

Inventing exact training-hour table cells from memory without verifying the published edition (the next section teaches the structure of those requirements without pretending secondary notes replace the document)

Master this overview first. Training hours, experience, vision, examinations, and recertification all hang off the same spine: recommended practice → Written Practice → Level III technical ownership → employer certification records .