Visual Weld Inspections, Before, During, and After
By Ken Fields, CET, CWI
Visual inspection is the most powerful tool in structural steel welding when implementing a robust quality control (QC) and assurance (QA) program. Unfortunately, many involved in the development, procurement, and execution of QA/QC programs do not fully understand what is involved in leveraging visual weld inspection to the greatest extent.
Visual inspection of structural steel welding is often misconstrued as part of non-destructive testing (NDT). In most circumstances, NDT testing of structural steel is done at the end of the fabrication or erection processes. On the other hand, proper visual weld inspection is not just conducted after the welds are complete. A Certified Weld Inspector (CWI) must begin introducing quality control and assurance measures before a weld takes place and continue throughout the welding process rather than starting the inspection process upon project completion.
Visual inspections are highly effective if actively performed during all three phases of welding: pre-welding, welding, and post-welding. Unfortunately, the first two phases are typically overlooked by contractors and owners alike. These phases are by far the most critical and will detect the majority of weld discontinuities when employed correctly. This early phase detection results in the ability to correct errors earlier while a contractor is working on fabrication and other welding activities. This allows for the most efficient use of resources and corrects errors in a timely manner for all parties. Waiting until the last phase for inspection can result in costly and complicated repairs.
Phase 1 – Pre-Welding
The first phase, pre-welding, needs to start with visual inspections. During this phase, the CWI should have received and reviewed the governing documents (e.g. construction documents and project specifications) to which welding activities must adhere. The CWI, at this time, will review welding procedure specifications (WPS), welder performance qualification test records (WPQR), and welding materials for compliance with the governing documents. This is also when inspection plans are developed and critical weld locations are identified. Once the WPS, WPQR, inspection plan, and materials have been approved, visual inspections will focus on periodic joint geometry and fit-up inspections. Visual inspections during the pre-welding phase may seem premature, but it sets the groundwork for quality outcomes.
Phase 2 – Welding
The welding phase—or the second phase—is the most critical time for visual inspections and will yield the best return on investment when locating discontinuities because it will reduce costly repairs and avoid interruptions to the schedule. During this phase, the CWI is required to periodically perform visual inspections of initial welding activities. Initial activities include maintaining pre-heat and interpass temperatures, cleaning and removing slag after each pass, developing proper weld layer thickness and profile, and ensuring the welding is conducted by qualified welders and performed within the approved WPS parameters. With teamwork and repetition during this phase, quality will become commonplace.
Phase 3 – Post-Welding
Lastly, the post-welding phase should be quick and easy if adequate visual inspections have been conducted during earlier welding phases. If not, this phase often becomes difficult and costly. Common governing documents require that 100% of all welds be visually inspected during this phase and include verification of the final weld appearance, size, length, and location. The weldments most often inspected are those with dimensional tolerances and distortions and post-weld heat treatments. A properly conducted post-welding visual inspection may reveal some minor discontinuities and require some minor repairs, but the majority of the issues should have been resolved and corrected before this phase as a result of a complete visual inspection program.
As discussed, visual inspections— throughout all three phases of the welding process—are highly effective ways to ensure weld quality. Whether welding is a small or large part of your construction project, visual inspection is an important and often necessary process for a successful project outcome. On your next project, consider a holistic visual inspection approach that will contribute to better project schedules, reduce construction costs, and improve final project outcomes.
Morrison-Maierle has AWS Certified Welding Inspectors on staff that would be happy to answer any questions regarding weld inspections for your current or upcoming projects.