🔩 Visual testing (VT) of welded joints — direct and remote inspection with illumination of min. 350 lx
In short
Inspection of the welded joint with a white-light illuminance of at least 350 lx (500 lx recommended), with the eye at a distance of up to 600 mm and at an angle of not less than 30° to the surface; where there is no access — remote testing with mirrors, borescopes, optical fibres or cameras. The test is performed according to PN-EN ISO 17637:2017-02; Illuminance: White light, minimum 350 lx on the surface under test; 500 lx recommended (tinted glasses raise the required minimum). The procedure comprises 8 steps; it is used for: Inspection of the joint preparation before welding: shape and dimensions of the bevel, cleanliness of the fusion faces, alignment of the parts with each other, In-process inspection during welding: cleaning of runs, absence of cracks and cavities, transitions between runs, depth and shape of gouging, Acceptance testing of the finished joint: excess weld metal, width and regularity of the face, root concavity, penetration, undercuts, pores, cracks, stray arc strikes.
At a glance
- Standard: PN-EN ISO 17637:2017-02
- Category: Materials and NDT
- Procedure steps: 8
- Illuminance: White light, minimum 350 lx on the surface under test; 500 lx recommended (tinted glasses raise the required minimum)
- Viewing distance: Eye within 600 mm of the surface under test (direct testing)
- Viewing angle: Not less than 30° to the surface under test
Overview
The standard specifies the visual testing of fusion welds in metallic materials; it may also be applied to the visual testing of the joint prior to welding. The second edition, ISO 17637:2016, cancels and replaces the first edition, ISO 17637:2003, which has been technically revised. The standard contains no normative references and no definitions of terms.
Visual testing is the first stage of product quality control; for welded joints it is mandatory. It allows incorrect geometry (e.g. an improper weld shape) and surface discontinuities — cracks, pores, laps, undercuts, lack of fusion and craters, as well as in-service defects from corrosion, erosion and fatigue wear — to be detected quickly and cheaply. The visual method can detect cracks from about 0.01 mm wide, from about 0.1 mm long and from about 0.1 mm deep. The probability of detection depends on the position and dimensions of the discontinuity, the geometry of the object, the preparation and roughness of the surface, the illuminance, the direction of incidence of the light beam, the viewing distance, and the experience and visual acuity of the examiner.
The standard does not specify the extent of visual testing — it should be determined in advance, e.g. by reference to a product standard or an application standard. The standard describes testing of the joint preparation, testing during welding, testing of the finished joint (cleaning and dressing, profile and dimensions, root and surfaces, post-weld heat treatment) and testing of repaired joints. Acceptance criteria are taken from the product standard or from agreed criteria, e.g. ISO 5817 or ISO 10042. If the result of the visual test is inconclusive, it is recommended to supplement it with other surface non-destructive methods.
Method principle
The surface of the welded joint and the adjacent zones are inspected and assessed against the acceptance criteria. In direct testing, access must allow the eye to be placed within 600 mm of the surface under test and at an angle of not less than 30°. The illuminance of the surface with white light must be at least 350 lx, with 500 lx recommended; wearing tinted glasses (e.g. sunglasses) raises the required minimum. An additional light source may be used to increase contrast and make imperfections stand out against the background. Where the access required for direct testing is not possible, or where the application standard so requires, remote testing using mirrors, borescopes, fibre-optic cables or cameras is specified.
Applications
- Inspection of the joint preparation before welding: shape and dimensions of the bevel, cleanliness of the fusion faces, alignment of the parts with each other
- In-process inspection during welding: cleaning of runs, absence of cracks and cavities, transitions between runs, depth and shape of gouging
- Acceptance testing of the finished joint: excess weld metal, width and regularity of the face, root concavity, penetration, undercuts, pores, cracks, stray arc strikes
- Testing of repaired joints before and after re-welding
- Stage preceding penetrant, magnetic particle, ultrasonic and radiographic testing
Key parameters
| Parameter | Value |
|---|---|
| Illuminance | White light, minimum 350 lx on the surface under test; 500 lx recommended (tinted glasses raise the required minimum) |
| Viewing distance | Eye within 600 mm of the surface under test (direct testing) |
| Viewing angle | Not less than 30° to the surface under test |
| Angle of incidence of light | Testing is most accurate with an angle of incidence of the beam of 45–85° to the surface (literature of the Silesian University of Technology) |
| Remote testing | Mirrors, borescopes, fibre-optic cables, cameras — when direct access is not possible or when required by the application standard |
| Detectability | Cracks from approx. 0.01 mm wide, from approx. 0.1 mm long and from approx. 0.1 mm deep |
| Acceptance criteria | Product standard or agreed criteria, e.g. ISO 5817 or ISO 10042 |
Standard
- Standard number
- PN-EN ISO 17637:2017-02
- Title (PL)
- Badania nieniszczące złączy spawanych — Badania wizualne złączy spawanych
- Title (EN)
- Non-destructive testing of welds — Visual testing of fusion-welded joints
Step-by-step procedure
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Determining the extent and documentation
Determine the extent of testing in advance, e.g. by reference to a product standard or an application standard. The examiner must have access to the necessary inspection and production documentation. Plan the test while physical access to the joint is still possible.
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Viewing conditions
Provide white-light illumination of at least 350 lx (500 lx recommended) and measure it with a lux meter, access allowing the eye to be positioned within 600 mm of the surface, and a viewing angle of at least 30°. Where such access is not available, switch to remote testing.
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Testing the joint preparation
Check whether the shape and dimensions of the preparation meet the requirements of the welding procedure specification (WPS), whether the fusion faces and adjacent surfaces are clean and have received the required surface treatment, and whether the parts are correctly aligned with each other in accordance with the drawings or instructions.
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Testing during welding
Check the cleaning of each run and layer before the next is deposited (with particular attention to the junction between the weld metal and the fusion face), the absence of visible imperfections (cracks, cavities), the profile of the transitions between runs and between the weld and the parent material, and the depth and shape of gouging; after repairs check conformity with the original WPS requirements.
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Cleaning and dressing of the finished joint
Check the removal of slag, the absence of tool marks and pits from arc strikes, the absence of overheating and grinding marks when dressing the face, and the smooth blending of fillet welds and butt welds dressed flush into the parent material, without underflushing.
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Profile and dimensions
Check the profile of the face and the height of the excess weld metal against the acceptance criteria, the regularity of the surface and the spacing of the runs, the weld width along the entire length of the joint and — for butt welds — complete filling of the preparation.
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Root and surfaces
For single-sided butt welds assess the penetration, root concavity, burn-through and shrinkage grooves; check undercuts, cracks and porosity of the face and the heat-affected zone (with the help of optical instruments where necessary), the removal of temporary attachments and the absence of cracks at their attachment points, and stray arc strikes. Carry out the final test after heat treatment.
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Test report
In the report give the manufacturer of the component, the testing body, the identification of the object, the material, the type of joint and the material thickness, the welding process, the acceptance criteria, the imperfections exceeding the criteria with their location, the extent of testing, the instruments used, the result referred to the criteria, and the name of the examiner and the date. Joints tested and accepted should be marked; where permanent documentation is required, take photographs or make accurate sketches.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| White light source | Lamp or torch giving at least 350 lx (500 lx recommended) on the joint surface; additional source to increase contrast | — |
| Lux meter | Measurement of the illuminance before testing, with the value recorded in the report | — |
| Weld gauge | Measurement of excess weld metal, concavity, fillet weld throat thickness and undercuts | — |
| Magnifier or microscope | For direct testing of accessible surfaces when fine cracks and pores are suspected | — |
| Endoscope or videoscope | An endoscope transmits the image through lenses and optical fibres to the eyepiece, a videoscope records the image with a high-resolution camera; probe with its own light source, tip articulated by cables or hydraulically | — |
| Inspection mirrors | For assessing the root and locations not directly accessible | — |
| Calliper and gauges | Geometric measurements of the joint and checking the correct assembly of the components | — |
Health and safety (OHS)
- Hot components, slag and spatter after welding — gloves, wait for cooling before close inspection
- Arc radiation during in-process inspection — eye protection, do not look at the arc
- Tinted glasses raise the required minimum illuminance — do not use them instead of proper lighting of the workstation
- Work in confined spaces and at height (tanks, pipelines, structures) — ventilation, safety harness, fall protection
- Sharp edges, burrs and chips — gloves and safety glasses
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN ISO 17637:2017-02 — “Non-destructive testing of welds — Visual testing of fusion-welded joints”.
How does this method work?
The surface of the welded joint and the adjacent zones are inspected and assessed against the acceptance criteria. In direct testing, access must allow the eye to be placed within 600 mm of the surface under test and at an angle of not less than 30°.
What is the measuring range and accuracy?
Illuminance: White light, minimum 350 lx on the surface under test; 500 lx recommended (tinted glasses raise the required minimum); Viewing distance: Eye within 600 mm of the surface under test (direct testing); Viewing angle: Not less than 30° to the surface under test; Angle of incidence of light: Testing is most accurate with an angle of incidence of the beam of 45–85° to the surface (literature of the Silesian University of Technology).
How long does the test take?
The procedure comprises 8 steps. The standard does not give a duration for every stage — the laboratory's own procedure decides.
What equipment is required?
White light source, Lux meter, Weld gauge, Magnifier or microscope, Endoscope or videoscope, Inspection mirrors, Calliper and gauges.
Where is this test used?
Inspection of the joint preparation before welding: shape and dimensions of the bevel, cleanliness of the fusion faces, alignment of the parts with each other; In-process inspection during welding: cleaning of runs, absence of cracks and cavities, transitions between runs, depth and shape of gouging; Acceptance testing of the finished joint: excess weld metal, width and regularity of the face, root concavity, penetration, undercuts, pores, cracks, stray arc strikes; Testing of repaired joints before and after re-welding; Stage preceding penetrant, magnetic particle, ultrasonic and radiographic testing.
What safety precautions apply?
Hot components, slag and spatter after welding — gloves, wait for cooling before close inspection; Arc radiation during in-process inspection — eye protection, do not look at the arc; Tinted glasses raise the required minimum illuminance — do not use them instead of proper lighting of the workstation; Work in confined spaces and at height (tanks, pipelines, structures) — ventilation, safety harness, fall protection; Sharp edges, burrs and chips — gloves and safety glasses.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN ISO 17637.