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Visual-weld-inspectionto prove Weld Quality.SOLUTIONS with Effective, Practical Advice
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.
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.
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: 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 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. An Article on Advancements in Assisted Visual Inspection was published (11) in Issue 117 of Practical Welding Letter for May 2013. An Article on Improved Visual Inspection was published (2)
in Issue 148 of Practical Welding Letter for December2015. An Article on Avoiding Overwelding was published (3) in Issue 159 of Practical Welding Letter for November 2016. 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 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.
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