to prove Weld Quality.
- Visual Weld Inspection Criteria
- Aws Visual Inspection Criteria
- Visual Weld Inspection Acceptance Criteria Aws D1.1
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All suppliers and visual weld inspectors shall be approved in accordance with RQN HK. 4.2 All weldments shall be inspected inch-by-inch to the print requirements. Specifically, the size, length and location of each weld required by the print shall be verified on the part and no unspecified welds have been added. When conducting remote inspection the use of visual aids such as telescopes, bore scopes, fiber scopes, cameras, or other suitable instruments shall be used. Such systems shall have a resolution capability at least equivalent to that obtainable by direct visual observation.
All Important Visual weld inspection |
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Visual-weld-inspection consists in the immediate critical observation of the external features visible on all welds.
It is the first and most important quality assessment to be performed as soon as the welding operations are accomplished.
Other inspection procedures may be required to detect discontinuities not visible to the eye or present below the external surface.
Whatever additional non destructive inspection methods are applied, they are performed only after Visual-weld-inspection is successfully completed.
The subject was addressed in our general page on Welding Inspection and in the even more general introduction to Weld Quality.
A short article on Visual weld inspection was published (11) in Issue 8 of Practical Welding Letter for April 2004. Click on PWL#008 to see it.
A page listing online resources on Visual Inspection and Requirements was published in Issue 49B of Practical Welding Letter, Mid Month Bulletin for September 2007. Click on PWL#049B.
What is included in Visual-weld-inspection?
Visual-weld-inspection includes two different aspects of the operation.
The first is the visual assessment of the external look of the weld.
Correct location, extent, dimensions and tolerances per engineering drawing requirements have to be checked with suitable measuring instruments, assessed and recorded.
The appearance has to correspond to regular best practice, by anyone looking with critical eye at its characteristic features.
This part has to be done first and foremost by the welder. The welder has to be proud of the production coming from under his/her hands.
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Any hints to indications of less than perfect results should be used to look for their causes and drive the search for required improvements of the welding technique.
The second has to do with the formal documented assessment of the Visual Weld Inspector, the person in charge of verifying that procedures, materials and workmanship used to perform the job are indeed those specified and approved for the project.
The Inspector has to be formally instructed and qualified, and his/her minimum visual acuity must be checked, certified and documented in writing, periodically, by an approved optometrist.
Visual Inspection has to be performed according to a specific written procedure.
Note: If you think on a career as a Certified Welding Inspector, you may take a look at the following page:
http://www.aws.org/certification/CWI/
http://www.aws.org/certification/CWI/
To conduct adequate Visual-weld-inspection there is need of sufficient illumination to be checked periodically with a calibrated photometer.
A low power magnifying glass is a useful tool for Visual-weld-inspection.
Surfaces inaccessible to unobstructed view may need additional aids like mirrors (dental or otherwise) and borescopes, slender instruments that include illumination and magnification, that can be introduced through narrow openings.
When performing the Visual-weld-inspection job, the Certified Welding Inspector has to ascertain that each requirement of the approved WPS (Welding Procedure Specification) is correctly been taken care of.
This is done by looking at the prepared check list and verifying that each clause is met.
Visual Welding Inspectors must know the requirements of Codes and standards, must be able to identify base metals and consumables, with reference to adequate documentation and markings.
They must measure dimensions and control tolerances, must check adequate fit-up and weld preparation, processes, positions, preheat application when required and correctness of welding parameters applied.
The requirement to verify that Welding Consumable storage and control are indeed adequate means to check that conditions are suitable to prevent degradation and that mixing of products is carefully avoided.
Visual-weld-inspection addresses completeness of welding performed, including eventual post weld heat treatments required, all dimensions and tolerances, visual indications of discontinuities and features of the weldments to determine if they are within the approved limits.
In case of discrepancy a suitable Nonconformance Report has to be prepared by the Inspector and submitted to the person responsible for quality approval.
![Visual Weld Inspection Criteria Visual Weld Inspection Criteria](/uploads/1/2/6/5/126511326/673169437.jpg)
Visual-weld-inspection is intended to find and mark for repair obvious visual nonconformances such as cracks, surface porosity, dimensional discrepancies, excess concavity or convexity, unfilled areas, undercut, misalignment, craters, unacceptable arc striking spots and any other objectionable visual features.
In case of doubt the indications have to be marked and then their importance assessed relative to drawings or applicable specifications.
Visual-weld-inspection is conducted generally on production welds immediately after welding.
But it may be required also for maintenance purposes at any time during the service life of welded items, to determine if corrosion or other damage intervened, and if there is a need for more accurate evaluation and eventual repair to assure continued usability.
A note on Inside Tube Inspection was published (3) in Issue 82 of Practical Welding Letter for June 2010.
Click on PWL#082 to see it.
Click on PWL#082 to see it.
An Article on Advancements in Assisted Visual Inspection was published (11) in Issue 117 of Practical Welding Letter for May 2013.
Click on PWL#117 to see it.
Click on PWL#117 to see it.
An Article on Improved Visual Inspection was published (2) in Issue 148 of Practical Welding Letter for December2015.
Click on PWL#148.
Click on PWL#148.
An Article on Avoiding Overwelding was published (3) in Issue 159 of Practical Welding Letter for November 2016.
Click on PWL#159.
Click on PWL#159.
A different but correlated subject is Visual inspection of fractured surfaces, that can contribute to determine the failure root cause.
Click on Fractographic Examination to read this new page.
See the instructive article on Visual Inspection
http://www.aws.org/itrends/2007/04/it200704/it0407-15.pdf
http://www.aws.org/itrends/2007/04/it200704/it0407-15.pdf
The following video is just an example of modern trends to automate visual inspection. No recommendation or endorsement is intended: only information to be validated by independent means.
Watch the Video!Wiki-SCAN: The Visual Handheld Welding Inspection System |
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To reach a Guide to the collection of the most important Articles from Past Issues of Practical Welding Letter, click on Welding Topics.
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This article covers the weld defect acceptance criteria as per ASME Section VIII Div 1
Acceptance criteria for Visual Inspection
(Refer: UIG-97, Page – 345 of ASME BPVC Section VIII Div 1, 2017 Edition.)
(a) The surface shall be free of any visible laminations, spalling, or cracks. Cracks in tubes shall not be repaired and shall be considered cause for rejection.
(b) For tubes, the depth of scratch shall not exceed 1/32 in. (0.8 mm). For all other material, the scratch depth shall not exceed 1/8 in. (3 mm).
For an acceptable limit of thickness reduction, Refer to UW-35 (sub-para b, page – 144) which states that:
- The reduction in thickness shall not exceed 1mm (1/32 in.) or 10% of material nominal thickness whichever is less, provided that the material of the adjoining surfaces below the design thickness at any point.
For the allowable limit of Weld Reinforcement, Refer UW-35 (sub-para d, Page – 144)
![Visual weld inspection criteria tool Visual weld inspection criteria tool](/uploads/1/2/6/5/126511326/131487125.jpg)
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Acceptance criteria for Radiography Test (RT)
(Refer: UW-51: Sub Para b (Page 148 and 149) and Mandatory Appendix 4 (Page 400 and Page 403) of ASME BPVC Section VIII Div 1, 2017 Edition.)
Following terminologies have been used to explain the acceptance/rejection criteria for Radiography Test (RT);
Linear Indication: Any indication with length greater than three times the width. Linear indications are mainly cracks, lack of penetration, lack of fusion, and elongated slag inclusions.
Rounded Indication: Any indication with the length equal to or less than three times the width. A rounded indication may be of circular, elliptical, conical, or irregular in shape and may have tails. While determining the size of an indication, the tail shall also be included. Rounded indications may appear on radiographs from any imperfection in the weld, such as porosity, slag, or tungsten.
Acceptance criteria for Linear Indication (UW – 51):
- Any crack, lack of penetration and lack of fusion shall not be accepted
- Any other elongated indication shall be considered unacceptable, which has a length greater than;
- 6 mm (1/4 in.) for T up to 19 mm (3/4 in.)
- T/3 for T greater than or equal to 19 mm (3/4 in.) and less than or equal to 57 mm (2-1/4 in.) i.e. 19 mm ≤ T ≤ 57 mm.
- 19 mm (3/4 in.) for T greater than 57 mm (2-1/4 in.)
(Where, ‘T’ – Thickness of the weld metal excluding any allowable reinforcement).
- Any group of indications (inline) with an aggregate length of more than T (within a length of 12T) shall be considered unacceptable except when the distance between the successive discontinuities exceeds 6L.
(where ‘L’ is the length of the longest imperfection in the group).
Acceptance criteria for Rounded Indication (Mandatory Appendix 4):
According to this appendix, those rounded indications which exceed the following dimensions shall be considered relevant.
- T/10 for T less than 3 mm (1/8 in.)
- 0.5 mm (1/64 in.) for T from 3 mm to 6 mm (1/8 in. to 1/4 in.), inclusive
- 1.0 mm (1/32 in.) for t greater than 6 mm to 50 mm (1/4 in. to 2 in.), inclusive
- 1.5 mm (1/16 in.) for T greater than 50 mm (2 in.)
Apart from the above conditions, Mandatory Appendix 4 also contains some tables, charts, and figures as a reference for acceptance/rejection criteria.
Please watch the video (given below) for more clarity on acceptance criteria for Radiography test (RT);
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Acceptance criteria for Ultrasonic Test (UT)
(Refer: Mandatory Appendix 12 (Page 435) of ASME BPVC Section VIII Div 1, 2017 Edition.)
(a) Indications characterized as cracks, lack of fusion, or incomplete penetration are unacceptable regardless of length.
(b) Other imperfections are unacceptable if the indications exceed the reference level amplitude and have lengths which exceed:
- 6 mm (1/4 in.) for T up to 19 mm (3/4 in.)
- T/3 for T from 19 mm to 57 mm (3/4 in. to 21/4 in.)
- 19 mm (3/4 in.) for T over 57 mm (21/4 in.)
where T is the thickness of the weld excluding any allowable reinforcement. For a butt weld joining two members having different thicknesses at the weld, T is the thinner of these two thicknesses. If a full penetration weld includes a fillet weld, the thickness of the throat of the fillet shall be included in T.
Please watch the video (given below) for more clarity on acceptance criteria for Ultrasonic test (UT);
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Acceptance criteria for Liquid Penetrant Test
(Refer: Mandatory Appendix 8 (Page 417) of ASME BPVC Section VIII Div 1, 2017 Edition.)
The following terminologies have been used to explain the acceptance/rejection criteria for Liquid Penetrant Examination (PT).
Relevant Indications: Indications with major dimensions greater than 1.5 mm (1/16 in.) shall be considered relevant.
Linear Indication: Any indication with length greater than three times the width.
Rounded Indication: Any indication with the length equal to or less than three times the width. A rounded indication may be of circular or elliptical shape.
Acceptance Criteria for Liquid Penetrant Examination (Mandatory Appendix 8):
All surfaces to be examined shall be free of:
(a) Relevant linear indications shall be rejected.
(b) Relevant rounded indications greater than 5 mm (3/16 in.) shall be rejected.
(c) Four or more relevant rounded indications in a line separated by 1.5 mm (1/16 in.) or less (edge to edge).
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Acceptance criteria for Magnetic Particle Test (MT)
(Refer Mandatory Appendix 6 (Page 412) of ASME BPVC Section VIII Div 1, 2017 Edition. Acceptance criteria are the same as that of Liquid Penetrant Examination)
The following terminologies have been used to explain the acceptance/rejection criteria for Magnetic Particle Test (PT).
Relevant Indications: Indications with major dimensions greater than 1.5 mm (1/16 in.) shall be considered relevant.
Linear Indication: Any indication with length greater than three times the width.
Rounded Indication: Any indication with the length equal to or less than three times the width. A rounded indication may be of circular or elliptical shape.
Aws Visual Inspection Criteria
Acceptance Criteria for Magnetic Particle Examination (Mandatory Appendix 6):
All surfaces to be examined shall be free of:
(a) Relevant linear indications shall be rejected.
(b) Relevant rounded indications greater than 5 mm (3/16 in.) shall be rejected.
(c) Four or more relevant rounded indications in a line separated by 1.5 mm (1/16 in.) or less (edge to edge).