By Albert J. Moore Jr. Feature Writing the Welding Procedure Specification Here’s help in writing useful WPSs that will ensure welders meet the customer’s requirements This is the fourth and final article in a series aimed at helping you understand the concept of Welding Procedure Specifications (WPSs). This article aims to help you write an actual WPS. Before getting into a lot of detail about what a Welding Procedure Specification (WPS) must contain, I believe it is useful to define what the purpose of the WPS is. The WPS is a formal written instruction that provides the welder with the directions necessary to deposit welds in a consistent manner that meets the project specifications. To use the same analogy as in the previous three articles, the WPS is a recipe a welder can follow to make a weld much like a cook follows a recipe to make brownies. This article shows you how to write a WPS that the welder can use and will ensure the customer’s requirements are met. While the approach works for both prequalified WPSs and those qualified by testing, we will develop a WPS that is qualified by testing and review some essential variables typically required by a welding standard. However, keep in mind that no two welding standards are the same. Each welding standard has unique requirements that have to be reviewed to ensure the WPS complies with all the requirements. While our approach is applicable for writing a WPS for any standard, never forget that a WPS written to meet ASME Section IX (and the applicable construction code) is different from a WPS written to meet AWS D1.5 or NAVSEA S9074- AR-GIB-010/278. Fig. 1 — An example of a numbering system for Welding Procedure Specifications. What the WPS Needs to Include Identification Each welding document must have a unique identification. Welding standards do not define the system of identification. It is left to the manufacturer to devise a system suitable for its needs. A simple numbering system is fine when there are a limited number of WPSs. However, as the number of WPSs increases, too simple of a numbering system becomes clumsy to use. I prefer an identification system that provides the user with some basic information about the WPS. Remember that it is not a good idea to use the same system for both the Procedure Qualification Record (PQR) and the WPS. I use an alpha numeric system that lists the welding process, base metals, filler metal, and, finally, a single letter discriminator to differentiate between two similar WPSs. Figure 1 is an example of this system. There is nothing sacred about this system. Use what works for you, but keep in mind that a system with a rational basis is easier to remember and use. Supporting PQRs Welding procedures that are qualified by testing must list the supporting PQR(s). A WPS qualified by testing must be supported by one or more PQRs. An example in which more than one PQR is used to support a single WPS is when the welding positions used in production must be qualified by testing. Once all the required PQRs are approved, they can be combined into one WPS. Welding Process The WPS has to list the welding process and, when applicable, any variation such as transfer mode, whether pulsing is used, and whether the process is manual, semiautomatic, mechanized, automatic, or robotic. Inspection Trends / Winter 2011 29
Inspection Trends - January 2011 - Winter
To see the actual publication please follow the link above