11.3 Qualification Framework: ASNT SNT-TC-1A, CP-105, and ISO 18436-7

11.3 Qualification Framework: ASNT SNT-TC-1A, CP-105, and ISO 18436-7

Infrared thermography is an established non-destructive testing (NDT) method and condition monitoring diagnostic technology. Because thermographic inspection findings directly influence decisions regarding catastrophic plant shutdowns, life-safety remediation, and insurance underwriting, personnel performing these inspections must possess verified technical competency. Industry relies on standardized qualification and certification frameworks to validate practitioner capabilities. In the global marketplace, two dominant systems govern thermographer credentials: the employer-based certification system administered under the American Society for Nondestructive Testing (ASNT), and the central certification system administered under the International Organization for Standardization (ISO). Certified thermographers must understand the operational rules, scopes of responsibility, and visual acuity requirements that define their professional practice.

Central Certification Versus Employer-Based Certification Systems

A critical distinction on professional certification examinations is the difference between employer-based and central certification models:

1. Employer-Based Certification System (ASNT SNT-TC-1A):

   • Predominant in the United States across industrial manufacturing, aerospace, petrochemical, and electrical utility sectors.
   • Under ASNT Recommended Practice No. SNT-TC-1A (Personnel Qualification and Certification in Nondestructive Testing), the employer is legally and administratively responsible for qualifying and certifying its own inspection personnel.
   • The governing document is the employer's formal Written Practice, customized to the company's specific equipment, codes, and operational risks.
   • Non-Portability Rule: An SNT-TC-1A certification is owned by the employer, not the employee. When a certified thermographer terminates employment with Company A, their certification terminates immediately. Company B cannot simply "accept" the physical certificate; Company B must review the technician's prior training and experience records, administer company-specific examinations, and formally issue a new certification under Company B's Written Practice.

2. Central Certification System (ISO 18436-7 and ASNT ACCP):

   • Predominant in international markets, condition monitoring sectors, and European industrial facilities.
   • Governed by ISO 18436-7 (Condition monitoring and diagnostics of machine systems — Requirements for qualification and assessment of personnel — Part 7: Thermography), or the ASNT Central Certification Program (ACCP).
   • An accredited, independent third-party certification body administers standardized examinations and maintains practitioner registries.
   • Portability: Central certifications belong to the individual practitioner and remain valid regardless of employer changes, provided periodic surveillance and renewal requirements are fulfilled.

Comparison of Certification Frameworks

The Governing Document: The Employer's Written Practice

Under SNT-TC-1A Section 5, an employer utilizing NDT must establish a Written Practice. The Written Practice is the operational charter governing the qualification program. It must explicitly specify:

• Minimum prerequisite educational background.
• Required classroom training hours based on ANSI/ASNT CP-105 (ASNT Standard Topical Outlines for Qualification of Nondestructive Testing Personnel).
• Minimum documented on-the-job experience (practical hours scanning in the field under qualified supervision).
• Administration and grading of three qualification examinations: General Examination (basic physics and radiation theory), Specific Examination (application of specific equipment, client procedures, and codes), and Practical Examination (hands-on camera operation and measurement).
• Minimum passing grade thresholds: typically a minimum of 70% on each individual examination and a composite average grade of at least 80%.
• Vision examination protocols and recertification intervals.

Scopes of Responsibility: Level I, Level II, and Level III

ASNT SNT-TC-1A establishes three distinct tiers of technical certification. Understanding the strict functional boundaries separating these tiers is paramount for compliance and quality assurance:

Level I Thermographer

• Authorized Scope: Qualified to perform specific calibrations, specific inspections, and specific data evaluations for acceptance or rejection determinations strictly in accordance with documented, approved written instructions or procedures. A Level I can set up infrared equipment, record radiometric data, perform environmental baseline logging, and identify thermal anomalies against established criteria.
• Strict Professional Restrictions: A Level I CANNOT independently evaluate or interpret test results, cannot select inspection techniques or methods, cannot write or modify inspection procedures, and cannot sign off or approve final inspection reports without direct Level II or Level III oversight and authorization.

Level II Thermographer

• Authorized Scope: Qualified to set up and calibrate equipment, interpret and evaluate results with respect to applicable codes, standards, and specifications. A Level II possesses the technical authority to organize and report the results of NDT inspections, prepare written inspection instructions, and provide day-to-day on-the-job guidance to Level I personnel.

Level III Thermographer

• Authorized Scope: Capable of establishing techniques and procedures; interpreting codes, standards, and specifications; and designating the particular NDT methods, techniques, and procedures to be used. A Level III must have the technical competence to establish the employer's Written Practice, design training curricula, administer qualification examinations, and audit overall program compliance.

Training and Experience Thresholds

Vision Acuity and Physical Perception Standards

Thermal imaging requires high-fidelity spatial resolution and visual differentiation of subtle temperature gradients rendered in false-color palettes (such as Ironbow, Rainbow, or Gray scale). The two frameworks handle vision differently, and the difference is examinable:

1. ASNT SNT-TC-1A — near-vision acuity, annually. Personnel must undergo an annual near-vision examination demonstrating natural or corrected near-distance acuity sufficient to read a minimum of Jaeger Number 1 (J-1) or Jaeger Number 2 (J-2) letters on a standard Jaeger card at a distance of not less than 12 inches (30.5 cm), or equivalent Snellen 20/25. Colour-contrast differentiation must also be demonstrated, at an interval set by the employer's written practice (commonly every 3 to 5 years) using Ishihara pseudoisochromatic plates or an equivalent test.
2. ISO 18436-7 — colour perception, advisory but consequential. ISO 18436-7 advises that every candidate have colour perception assessed with the Ishihara 24-plate test, that the result be retained and produced to the assessment body on request, and that misreading four or more of the 24 plates trigger a further task-specific test by the employer. If that task-specific test shows the deficiency affects palette interpretation, the candidate may be required to work in a monochrome palette, and both the test and the restriction must be documented.

The practical point for a working thermographer: red-green deficiency does not automatically disqualify you, but it must be documented, and it can formally restrict you to grayscale imagery.

Recertification Intervals and Documentation

Under ASNT SNT-TC-1A, the maximum recommended interval for recertification of Level I and Level II personnel is 5 years (many corporate Written Practices specify a more conservative 3-year cycle). Recertification may be accomplished via comprehensive re-examination or documented evidence of continued satisfactory technical performance.

The employer must maintain comprehensive qualification records for every certified individual throughout their tenure and for a minimum specified period (typically 3 to 5 years) following departure. Auditable records must include: training certificates, certified examination score sheets, annual vision test reports, documented experience logs, and the formal certification sign-off executed by the designated Level III or corporate officer.

Realistic Industry Scenario: Level I Scope Breach

Inspection Scenario

A contract thermographer holding a valid Level I certification conducts a quarterly baseline infrared survey of an automotive assembly plant. While scanning a 480 V, 1,200 A main distribution switchboard, the thermographer identifies an overheated fuse clip operating with a 38 °C temperature rise over adjacent phases. Believing the condition presents an imminent fire hazard, the Level I technician writes a formal "Emergency Red Tag" report, signs the document as "Lead Certified Thermographer," and directly orders the facility manager to de-energize the assembly line immediately, halting production.

During the post-outage corporate audit, the plant's insurance underwriter investigates the USD 180,000 production shutdown loss and discovers that the inspection report was issued solely under a Level I signature without Level II or Level III technical review.

Professional Standards Analysis

1. Violation of ASNT SNT-TC-1A: Under SNT-TC-1A Section 4.3, a Level I technician is strictly prohibited from independently evaluating inspection results, determining operational disposition, or approving inspection reports. The technician exceeded their legal and technical scope of authority.
2. Corrective Protocol: The Level I thermographer was legally obligated to record the thermal pattern, log electrical load and ambient parameters, and immediately transmit the raw radiometric data to a supervising Level II or Level III thermographer. The Level II/III is the sole authority qualified to evaluate the anomaly against NETA MTS standards, determine severity grading, prepare the engineering evaluation, and sign the official corrective recommendation.