Metal fabrication has a lot of moving parts. The more complex a project becomes, the more moving parts it has, incorporating a variety of skilled trades and professionals: mechanical, coating, designers, engineers, architects. The number of variables that need to be accounted for to achieve a successful, structurally sound, and safe fabrication project can be truly mind-boggling.
Qualify Welding Procedures per the Code
“Companies with weld tests often miss the fact that, to do the specific [code-level] welding the customer is asking for, our codes require very specific tests. It could be a butt-joint test on 3/8 or 1-in. plate, or 12-in pipe,” Cameron said. “First off, welders would need to do it in a specific position. Once they’ve passed the test in that position, they are allowed to weld only in the positions qualified. But they wouldn’t be qualified to weld in other positions that the particular test didn’t qualify.”
Welders might pass that horizontal groove weld test on 3/8-in.-thick plate. “I then walk into the shop and find them welding in the vertical-down position. That wouldn’t be allowed,” Cameron said. “It’s easy to make a weld that looks nice in that position, but you might not get the quality you want.” Quite often he conducts a destructive test on a beautiful-looking weld made in the vertical-down position—“and I get weld failure after failure after failure.”
Gravity makes the vertical-down welding position deceiving. The molten metal travels downward fast, which means the welding gun needs to travel fast as well. “Many people don’t do it correctly,” Cameron said. “They do it slowly, and they start using the welding gun like a caulking gun, applying layers but not fusing into the previous pass in any way.”
Cameron sees similar welder qualification problems when it comes to material thickness. If a welder is qualified per AWS D1.1, that’s great—but it also means that he or she can weld only a specific thickness range, starting at 0.125 in. “Then you walk into the weld shop and see those welders [performing code-level work] on 12- and 16-gauge sheet metal.”
If welders need to perform code-level welding on thinner material, “they need to be qualified to AWS D1.3, which is the structural code for sheet metal.” Cameron added that, ideally, this should be spelled out in the contract documents.
Yet another common welder qualification issue has to do with the weld joint geometry. As Cameron explained, “Say a welder is qualified to weld on groove welds in the flat position, as well as fillet welds in the flat and horizontal position. That encompasses quite a bit of what’s done in a typical fabrication shop.”