The importance of welding procedure specification (WPS)

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Last time, I discussed the need to clarify the acronyms and abbreviations we use within our specific industries. I made this statement at the end: “I hope I can help those working their way into the industry understand the importance of the hierarchy of a paper trail, how and when to use correct terminology, or why we might need a WPS—I mean, a welding procedure specification—for a specific weld.”

That statement generated the following comment: “What is so important about having a WPS? I have worked for years, I set the machine to my favorite settings, and I weld.” I will try to clear the muddy waters and address why a WPS is important. Bear with me as I try to unpack a tremendous amount of information in a small space.

There are essentially two types of welds: those that fall under a specific code and those that do not. However, this discussion is not about code use but rather the importance of the WPS used within various welding codes. We will be looking at welds governed by a welding code.

For those unfamiliar with the process, in the broadest of explanations, a code book will include proven techniques, pre- and postweld evaluation processes, design requirements, and weld process requirements, among many other things. By design, these codes meet a vast spectrum of applications. Some may be broader, while others are material-specific, industry-specific, or application-specific. Depending on the code or codes used, the requirements will cover all aspects of the weld from start to finish.

Various levels of documentation make up the paper trail of a completed weld. Often referred to as the “recipe for the weld,” the WPS contains the information the welder needs to follow regarding amperage, voltage, polarity, electrode, filler metal specifications, base metal specifications, applicable joint designs, travel direction, and weld sequencing.

The thing to remember in this whole hierarchy of welds and documents is that if done correctly through code-required testing, a WPS is based on facts from successful welds. These successful tests are recorded in the procedure qualification record (PQR). Welds done for a PQR will undergo various destructive and possibly nondestructive testing. If successful, the WPS is generated and used for qualifying welders and with welds as outlined in the project.

So, back to the original question: Why is a WPS important? To answer this simply, companies often work under contractional obligations dictated by the scope of work, municipality, or agency as a contract requirement. When a contract requires a specific code, the code will dictate WPS usage. Failure to use a WPS on a project that requires it is a risk that could lead to job loss, fines being levied against your employer, or a host of other issues.