Feature Good Practices for Inspecting Austenitic Stainless Steel Tube and Pipe Systems in Hygienic Applications The AWS D18.1/D18.1M Specification is indispensable for establishing weld inspection criteria By Michael Lang For clarity, this presentation is broken down into four parts: expectations, preconstruction weld sampling, surveillance of construction activities, and visual exam. Expectations Communication of expectations from owner, to contractor, to inspector, and finally to the welder is critical to successful welding. Unfortunately, all too often, AWS D18.1/D18.1M, Specification for Welding of Austenitic Stainless Steel Tube and Pipe Systems in Sanitary (Hygienic) Applications, is not known or specified during the project planning phase. Yet this document holds the criteria needed for the installation of safe, quality systems. In cases like this, the inspector should make the parties aware of the document and its criteria. It is the inspector’s job to inspect. It is not to engineer for the contractor, train the welder, or help end users figure out the quality their product requires. Inspectors are there to apply the relevant code and project specifications. The inspector must have clear criteria, and AWS D18.1/D18.1M is the definitive specification recognized by the industry. If the owner chooses not to follow industry codes and specifications, there should be a robust engineering argument to support such judgment. Inspectors should note any areas that are not AWS D18.1/D18.1M compliant on the appropriate inspection report. The critical aspect of this scope is that these systems carry commodities for human consumption, and the inspector is safeguarding the public health. Preconstruction Weld Sampling Preconstruction weld sampling (PWS) is an activity to prove the combination of welder/operator, machine, WPS, and materials are conducive to making repeatable quality welds. The inspector needs to verify PWS (Fig. 1) as acceptable per AWS D18.1/D18.1M Sec. 6, then use it as a standard during the production day. It needs to be understood that every change in size and/or thickness requires a different set of PWSs. AWS D18.1/D18.1M Sec. 5.2 is an excellent source of information on sampling procedures. I have seen the PWS process missed with the proposed solution being to do samples after the fact. This might sound good at first, but look deeper. Will you have the same gas, tungsten, quality of input power, and conditions? Obviously not. At this point, you have a system of indeterminate quality. There is a reason it is called preconstruction weld sampling. Inspection Trends / Spring 2013 19 Fig. 1 — Example of preconstruction weld sampling. Fig. 2 — Typical dial indicator used to check mismatch, convexity, concavity, and other conditions.
Inspection Trends | April 2013
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