How to Write an NDT Company Written Practice: ASNT SNT-TC-1A Complete Guide

What is a Written Practice and Why is It Mandatory?

A Written Practice is a company-level document that governs the entire qualification and certification program for NDT personnel. Under ASNT SNT-TC-1A, every employer that performs NDT must maintain a Written Practice. Without one, no certification issued by that company is valid — and every NDT procedure that references SNT-TC-1A is technically non-compliant because the Written Practice it should reference does not exist.

The Written Practice is not an NDT procedure — it does not describe how to examine a specific component. It describes how personnel are qualified, trained, examined, and certified. Individual NDT procedures reference the Written Practice to demonstrate that the personnel performing examinations meet defined competency standards.

Mandatory Sections of an ASNT SNT-TC-1A Written Practice

SNT-TC-1A Section 6 defines the minimum content. Annex A provides a recommended format. Your Written Practice must address all of the following:

1. Scope — NDT Methods and Techniques Covered

State which NDT methods and techniques are performed by the company and covered by this Written Practice. Methods not listed are not covered and cannot be used by company personnel for formal examination work under this Written Practice. Example:

"This Written Practice covers the following NDT methods: UT (Ultrasonic Testing), RT (Radiographic Testing), MT (Magnetic Particle Testing), PT (Liquid Penetrant Testing), and VT (Visual Testing), as performed by [Company Name] in accordance with ASNT SNT-TC-1A, [Edition]."

2. Training Requirements

For each method covered, state the minimum training hours required for Level I and Level II. SNT-TC-1A 2020 Table 6.3 provides the minimum hours — your Written Practice must meet or exceed these:

Training content must be specified: whether it is provided in-house or by an external training centre, and the topics covered per method (general principles, equipment, technique, codes and standards, evaluation, reporting).

3. Examination Requirements

The Written Practice must state the three types of examinations required and the minimum passing scores:

• General Examination: Questions on the basic principles of the method. Minimum passing score: typically 70% per SNT-TC-1A Section 8.3 — state the score your company requires (may exceed 70%).
• Specific Examination: Questions on the specific procedures, equipment, and codes applicable to the company's work. Minimum passing score: 70%.
• Practical Examination: Hands-on demonstration of ability to operate equipment and evaluate test specimens. Pass/fail based on demonstrated performance.

The Written Practice must also state who is authorised to administer examinations — typically an ASNT Level III in the applicable method.

4. Eye Examination Requirements

This is one of the most frequently missing elements. SNT-TC-1A Section 6.6 requires annual vision testing:

• Near vision acuity: Must be demonstrated by reading Jaeger J-1 letters or equivalent at a minimum distance of not less than 30 cm (12 inches) with one or both eyes, corrected or uncorrected.
• Colour differentiation (if applicable): For fluorescent PT and fluorescent MT, the candidate must be able to distinguish the colours used in the examination.
• The Written Practice must state the frequency of eye examination (annually) and the form used to document results.

5. Certification Levels and Responsibilities

Define the responsibilities of each certification level:

• Level I: Qualified to set up and calibrate equipment, perform examinations, and record results — only under the supervision of a Level II or Level III. Cannot independently evaluate or interpret indications.
• Level II: Qualified to set up, calibrate, conduct, supervise, and evaluate/interpret examinations. Must be able to train and direct Level I personnel. Must be able to organise and report results.
• Level III: Qualified to establish techniques and procedures, interpret codes, standards, and specifications, and designate methods and techniques. Approves NDT procedures. Responsible for training and qualifying Level I and II.

6. Certification Periods and Recertification

• Initial certification: state the validity period (SNT-TC-1A 2020: maximum 5 years)
• Recertification interval: every 5 years for Levels I and II per SNT-TC-1A Section 10.4
• Recertification requirement: pass the Specific and Practical examinations; OR the Level III may require retaking all three
• Recertification trigger: if a Level II has not performed NDT in the applicable method for 12 consecutive months, recertification is required per SNT-TC-1A Section 10.5

7. Record Keeping

The Written Practice must define:

• What records are maintained (training records, examination scores, certification certificates, eye examination records)
• Format of records (paper, electronic)
• Retention period — typically minimum 5 years or for the duration of the certified individual's employment plus 5 years
• Custodian of records (QA Manager, HR, or NDT Level III)

8. Supplement Training and OJT Documentation

On-the-Job Training (OJT) hours must be documented. The Written Practice should specify:

• How OJT hours are logged (daily log, supervisor sign-off, or electronic system)
• Who may supervise OJT (Level II or Level III in the applicable method)
• Whether OJT from previous employers can be accepted and what documentation is required

Common Written Practice Deficiencies Found During Audit

1. Written Practice does not exist — Company performs NDT and references SNT-TC-1A but has never created a Written Practice document
2. Training hours below SNT-TC-1A minimums — Written Practice states lower hours than required by Table 6.3
3. Eye examination not mentioned — Annual near-vision acuity requirement entirely absent
4. Passing scores not defined — Written Practice states examinations are required but does not define minimum passing scores
5. Level responsibilities not defined — Does not clearly state what Level I can/cannot do without supervision
6. No recertification requirement — 5-year recertification absent or incorrectly stated
7. No 12-month lapse provision — Does not address what happens when a certified individual stops performing NDT for over 12 months
8. Record retention period absent — Training and certification records must be kept for a defined period
9. Written Practice not controlled document — No document number, revision history, or approval signatures (Level III must approve)
10. Methods covered not listed — Written Practice is generic and does not specify which NDT methods it governs

Relationship Between Written Practice and NDT Procedures

Every individual NDT procedure (for UT, RT, MT, PT, etc.) should reference the Written Practice by document number and revision. The typical reference in a procedure reads:

"Personnel performing examinations under this procedure shall hold a minimum NDT Level II certification in [Method] in accordance with [Company] Written Practice [Doc. No. WP-NDT-001], Revision [X], which conforms to ASNT SNT-TC-1A, [Edition]."

If your Written Practice is not current, not controlled, or does not meet SNT-TC-1A requirements, every NDT procedure that references it inherits those deficiencies.