Burn-Through
Burn-through is a weld defect in which excessive heat melts completely through the joint root, creating a hole or excessive root reinforcement, common on thin-wall pipe welds.
Definition
Burn-through is caused by excessive amperage or travel speed too slow at root pass. It is visible from the inside of pipe and rejectable per ASME B31.3 and API 1104.
How this damage forms
Excess penetration melting through the root, leaving a void or globular sag on the inside of the joint — a root-side defect common in open-root pipe welding on thin wall.
How it is detected
RT shows it plainly (localised dark area at the root, often with a light halo of sagged metal); direct visual finds it where the root is accessible; UT root evaluation flags it less legibly.
What causes it, and what prevents it
A heat-input and fit-up message: too much current, too slow travel, too wide a gap. In corrosion service the sagged pocket also becomes a preferential attack site, which is why some owners treat burn-through more severely than its structural effect alone suggests.
Codes that govern assessment
Acceptance per API 1104, ASME B31.3 or the governing construction code — criteria address it under root concavity/excess penetration families.
The common reporting error
Confusing burn-through with internal undercut or root concavity on film. The verdicts differ; the film reader who lumps root anomalies together applies the wrong table.
Where Burn-Through fits in an inspection programme
A term is only useful when it connects to a decision. Burn-Through appears in written procedures, in technique sheets, and in the records an owner or accreditation body reviews afterwards — which means the way it is defined in your documentation has to match the way it is applied on site. Where the two drift apart, audits find it. Atlantis writes and reviews procedures against the governing codes, trains inspection personnel to apply them, and builds the record-keeping that makes the evidence retrievable years later. Procedure development and code consulting · NDT training and certification · Ask us about your programme.
Related terms
- Lack of Penetration (LoP) — Lack of penetration is a weld defect in which the weld root fails to extend completely through the joint thickness, leaving an unfused area at the root face.
- Undercut — Undercut is a groove melted into the base metal adjacent to the weld toe that is not filled with weld metal, reducing wall thickness and acting as a stress concentrator.
More defect terms
Crack · Lack of Fusion · Slag Inclusion · Porosity · Overlap · Weld Spatter · Lamination · Lamellar Tearing · Hydrogen-Induced Cracking · Stress Corrosion Cracking
Where this comes up in practice
Terms like this one appear in three places that matter commercially: the written practice that governs how your personnel are qualified, the procedures and technique sheets that define how an examination is actually performed, and the evidence an auditor or client asks for when they want to know why an inspection was accepted. Getting the terminology right is the easy part; being able to produce the qualification record, the calibration traceability and the procedure revision that applied on the day of the inspection is the part that decides audits.
Atlantis NDT provides NDT training and certification against ASNT SNT-TC-1A and ISO 9712, ASNT Level III consulting for written practices and procedure approval, inspection management software that holds qualification, calibration and procedure-revision evidence in recoverable form, and an asset integrity platform that binds inspection results to the asset they describe. Browse the full NDT glossary or ask a Level III directly.