Validating Magnetic Flux Leakage Reports Under SNT-TC-1A
Any US inspection service provider whose customer, code or purchase order invokes SNT-TC-1A: weld and fabrication NDT under ASME BPVC Section V and Section VIII, structural work under AWS D1.1, refinery, piping and tank work under the API inspection codes, and pipeline construction where 49 CFR 192.243 requires NDT performed to written procedures by trained, qualified persons.
Under SNT-TC-1A the recurring finding is: Written Practice is a copy of the standard rather than a description of how the firm actually trains, examines and. On a Magnetic Flux Leakage report specifically, detection performance claimed generically rather than qualified on a reference plate for the wall thickness in question Both are what an independent review of a MFL report opens first.
Detection performance claimed generically rather than qualified on a reference plate for the wall thickness in question. SNT-TC-1A is a recommended practice, not law. It gives an employer the framework for qualifying and certifying its own NDT personnel. For an inspection service provider the deliverable is a Written Practice covering training, examination, experience, vision and recertification for every method and level the firm sells, reviewed and approved by the employer's NDT Level III and retained on file for audit. Customers then audit the firm against its own Written Practice rather than against the standard directly. A validation that finds the report sound is as useful as one that does not: the point is a defensible answer, not a defect.
Source: ASNT Recommended Practice No. SNT-TC-1A (2024), with Addendum — ASNT product listing (source.asnt.org) and ASNT standards page (asnt.org/standards-publications/standards); the addendum took effect May 2025 and ASNT recommends use with ANSI/ASNT CP-105 (2024).
| Factor | What applies | Why it matters |
|---|---|---|
| Method under review | Magnetic Flux Leakage (MFL) | Each method leaves a different evidence trail |
| What the reviewer opens | the reference plate qualification for the wall thickness examined, tool speed and lift-off, and the stated probability of detection against a defined defect size | The items a dispute turns on |
| Most common way it fails | detection performance claimed generically rather than qualified on a reference plate for the wall thickness in question | Usually a records failure, not a technique failure |
| Governing regime | ASNT Recommended Practice No. SNT-TC-1A, Personnel Qualification and Certification in Nondestructive Testing | Enforced by American Society for Nondestructive Testing |
| Personnel basis | Employer-based certification — the written practice is part of the evidence | Whether the certification itself can be verified independently |
| Records regime | Recertification is periodic and the interval is fixed by the employer's own Written Practice, not by ASNT. | How far back the trail has to reach |
What does a MFL report have to show under SNT-TC-1A?
The reference plate qualification for the wall thickness examined, tool speed and lift-off, and the stated probability of detection against a defined defect size — plus the procedure number and revision, the technician's MFL certification current on the date of work, and the acceptance criteria with the code edition they came from. Missing any one of those makes the examination unprovable rather than merely undocumented.
What most often makes a MFL report indefensible?
Detection performance claimed generically rather than qualified on a reference plate for the wall thickness in question. It is a records failure rather than a technique failure — the examination was very likely performed correctly, and the evidence supporting it cannot be produced, which under SNT-TC-1A is treated the same way as not having done the work.
Can a MFL report be validated without re-inspecting?
Partly. A document review establishes whether the examination as recorded was adequate and correctly interpreted, and whether the personnel and equipment evidence holds. It cannot establish that the examination was performed as recorded, because MFL leaves no reviewable data set — for that, targeted re-inspection is the only answer.
Who is qualified to validate a MFL report under SNT-TC-1A?
A Level III qualified in MFL specifically. Method scope is the constraint people miss: a Level III qualified in another method cannot approve or credibly challenge a MFL interpretation, and an opposing reviewer will test that first because it is documentary and binary.
How far back do SNT-TC-1A records have to reach?
Recertification is periodic and the interval is fixed by the employer's own Written Practice, not by ASNT. ASNT describes a recommended maximum interval of five years between renewals for NDT personnel. Recertification requires evidence of continued competence — re-examination or documented continuing activity — plus current vision records. Accreditation of the programme itself under the ASNT EBC route runs three years, with some registrations on one-year terms requiring annual surveillance. Where a validation is being done for a dispute or a purchase, the retention period is what decides whether the question can be answered at all — records that were never kept cannot be reconstructed afterwards, and a reconstruction is worth markedly less than a contemporaneous record.
What happens if the validation finds the report was correct?
That is a normal and useful outcome. The buyer gets a defensible position to accept the work, pay the invoice, close the claim or proceed with the purchase — supported by an independent review rather than by assertion. A validation is commissioned to settle the question, not to find a defect.
What the reviewer traces
The reference plate qualification for the wall thickness examined, tool speed and lift-off, and the stated probability of detection against a defined defect size.
Personnel and records under SNT-TC-1A
Employer-based. The employer — not ASNT, not a third party — issues the certificate, and ASNT is explicit that where the person holds no third-party certification the credential is revoked on termination of employment. Because SNT-TC-1A states that in no case shall a certification examination be administered by oneself or by a subordinate, and because the Written Practice must be approved by an NDT Level III, a firm with no Level III on staff routinely engages an outside agency Level III.
Related: the report validation service, what makes a report defensible, SNT-TC-1A requirements, MFL under SNT-TC-1A and outsourced ASNT Level III cover.
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