Visual weld inspection
Planning and documenting visual examination of metallic fusion welds, with limits on access, measurement and acceptance.
Tags: inspection, welding, visual-testing, quality-control
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ISO 17637:2016, edition 2 (December 2016, confirmed in 2022), covers visual testing of metallic fusion welds and joint preparation. Accessible surfaces and dimensions are visible evidence. Embedded imperfections require an appropriate examination. ISO 17637:2016
For direct testing, ISO 17637 specifies at least 350 lx of white-light illuminance at the surface, recommends 500 lx, and requires access allowing the eye within 600 mm at an angle of at least 30° to the examined surface. These values belong to that method, not every visual-inspection application. It calls for considering mirrors, borescopes or cameras where direct access is unavailable or remote examination is specified. ISO 17637:2016, test conditions
Establish the inspection basis
Identify the joint, drawing revision, welding procedure specification (WPS), applicable product or fabrication standard, acceptance criteria and examination extent. The AWS B1.11M/B1.11:2015 preview describes examination before, during and after welding and says visual acceptance criteria should be defined before welding begins. Personnel responsibilities and any qualification or certification requirements come from the applicable documents; one certification scheme is not universally mandatory for every weld inspection. AWS Guide for the Visual Examination of Welds, third edition
An imperfection is an observed departure; deciding that it is rejectable requires the governing criterion. For example, ISO 5817:2023, edition 4, dated February 2023, defines workmanship quality levels B, C and D for its specified steel, nickel and titanium fusion-welded joints, excluding beam welding. B has the most stringent finished-weld requirements. Its scope starts at 0.5 mm material thickness and does not cover metallurgical properties such as hardness or grain size. Do not apply its limits automatically to aluminum, every welding process or a complete component's service fitness. ISO 5817:2023: scope and quality levels
Inspect while the relevant surfaces remain accessible
A practical inspection sequence should separate three opportunities:
| Stage | Examination objective |
|---|---|
| Before welding | Check joint preparation, fit-up, accessible surfaces and positioning against the WPS and drawings. |
| During welding | Examine exposed runs, cleaning and visible imperfections before subsequent deposits hide them. |
| After welding | Examine the cleaned finished surface and accessible root, geometry and specified dimensions. |
Plan access before assembly conceals the surface. ISO 17637 addresses these stages and examination after cleaning or dressing. ISO 17637:2016, visual-testing stages
The table is a planning aid, not a requirement that an inspector continuously watch every production weld. Define hold points, sampling or full coverage through the controlling inspection plan. If a required stage was missed, record the gap and obtain an approved disposition rather than inferring what the hidden surface looked like.
Lighting, access and viewing aids
Use lighting and viewing positions that reveal the feature rather than create misleading shadows or glare. A remote image must actually show the required region and support the intended observation. A photograph documenting a location is not automatically adequate for dimensional measurement, especially without a scale, suitable perspective and known resolution. Record inaccessible areas explicitly.
Measure the specified characteristic
Common observations include surface cracks, undercut, visible pores, overlap, excess or insufficient weld metal, misalignment and dimensional uniformity. TWI describes visual testing as one technique used alongside other NDT methods for these kinds of surface and dimensional observations. Use consistent terminology and location references so another inspector can find the same indication. TWI: visual inspection services and scope
As a bounded equipment example, the G.A.L. Gage Cat. 4 Bridge Cam Gauge sheet lists preparation-angle measurement from 0° to 60°, excess weld metal, undercut depth, pitting depth, fillet throat and misalignment capabilities, in inch or metric units. This list establishes intended functions, not a universal accuracy or acceptance tolerance. Select a gauge that fits the joint and measures the required feature; inspect its contact surfaces and verify its condition through the quality system. G.A.L. Gage: Cat. 4 product sheet
The manufacturer's demonstration places the gauge squarely on the reference surface and uses different contacts or slides for reinforcement, fillet dimensions and pits. Seating on spatter or an irregular reference can change the result. Fillet leg length, throat dimension and excess convexity are different characteristics: identify which the drawing specifies. An exterior gauge reading cannot independently establish internal fusion or penetration. G.A.L. Gage: Bridge Cam measurement demonstration
Interpret indications and examination limits
A visually satisfactory face does not prove internal fusion. TWI identifies penetrant or magnetic particle inspection as options for surface-breaking lack-of-fusion indications and radiography or ultrasonics for subsurface imperfections. Method effectiveness depends on material and flaw characteristics; additional testing needs an appropriate procedure and specified acceptance basis. Do not prescribe an NDT method solely from the external appearance. TWI: detecting lack of fusion
Original reporting example: suppose a joint drawing requires inspection of the face and root. The face is accessible and measured, while a backing arrangement blocks the root. The defensible record is “face examined at the identified locations; root not visually accessible,” with the measured results and an unresolved coverage item. “100% VT accepted” would overstate the work. A separate required volumetric examination remains a separate obligation even if every accessible surface passes visual criteria.
For a questionable linear indication, record its position, orientation and visible extent before authorized cleaning or further examination. Keep observation separate from diagnosis: an apparent line is not automatically a confirmed crack, while uncertainty is not a reason to mark the area acceptable. Route it through the specified evaluation procedure.
Repairs and reporting
ISO 17637 requires re-examination of repaired welds to the original requirements. Its records identify the object, joint, criteria, extent, devices, findings, result, examiner and date, with relevant imperfections located in photographs or sketches. ISO 17637:2016, repairs and records
Report the applicable standard editions and acceptance clauses, inspected surfaces and stages, access limitations, measured dimensions, instrument identity and disposition. “Passed visual inspection” should refer to a defined scope and criterion, not imply mechanical-property testing or universal service suitability.
Sources were reviewed November 1, 2026. The AWS preview explicitly identifies the 2015 third edition; the ISO 17637 PDF identifies 2016-12-01. The G.A.L. product sheet and demonstration did not display revision dates. Their examples are equipment guidance, not code acceptance limits.