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Evaluation of Welded Attachments on Pipe and Elbows

E. C. Rodabaugh, E. A. Wais, G. B. Rawls

WRC Bulletin 448


January 2000, (40pp)(ISBN#1-58145-455-4)
In piping systems, lugs are often used on elbows and straight pipe. Over the years Code Cases (N-122 and N-318) were developed and used to evaluate lugs on straight pipe. Report (1) describes the background and history of the development of these Code Cases. Until recently, there was very little test data on the fatigue life and limit load data for lugs on straight pipe and elbows. These lug configurations can be of various configurations, e.g. a rectangle with the long dimension parallel to the axis of the pipe (or elbow), a rectangle with the long dimension perpendicular to the axis of the pipe (or elbow), and a cross configuration. Report (2) discusses the results of a testing program on these lug configurations for both straight pipe and elbows.Report (2) documents, in detail , the test specimens data, test methodology, test results and the methodology used in the analysis of the data. Eight limit load and eight fatigue tests were performed. All specimens were NPS 12 inch schedule 20 ASTM A53 GR B. The lug material was ASTM A588 GR B. The elbows were long radius ANSI B16.9 fittings. The limit load tests were performed by incrementally increasing the load until the deflection was twice that predicted assuming elastic behavior. The fatigue tests were deflection-controlled tests where failure was defined as when through wall cracks occurred allowing water leakage. Report (1) uses this information , in addition to other data, in its in its evaluation of the Code Cases N-122 and N-318. As a result of the evaluation, specific recommendations are suggested for revisions to Code Cases N-122-2 and/or N-318-5. Report (2) suggests a general methodology for evaluating other configurations in addition to those tested. This methodology is based on an application of Code Case N-318-5. Specific examples of the application of this methodology are provided for two parallel longitudinal lugs on pipe, two parallel circumferential lugs on pipe, and a “H” lug configuration on pipe. These two reports....

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