Experimental results of ten girth weld and two unreinforced piping intersections recently tested at Paulin Research Group (PRG) are reported. Results are compared to the original Markl work [1–5] and to current ASME piping design code practices [6]. In addition, approximately 800 experimental tests from the literature [7–32] are compared to the new test results and the existing Mark1 equations. Findings indicate that the original mean girth weld equation provided by Mark1, which serves as the basis of the ASME piping codes, does not match trends expected for as-welded fatigue data. Discrepancies are apparent in the low and high cycle regimes. Finally, the new PRG test data and the existing data from literature are used to develop a new mean girth butt weld curve and to modify the existing ASME piping design codes.
The 2010 version of B31.3 introduced sustained stress indices (SSI's) in paragraph 320. Using methods in references [1],[2],[3],[4],[5], and [11], a test procedure was developed to evaluate these SSI's for standard metallic piping components. The test procedure has been incorporated into draft versions of B31J so that the sustained stress index can be produced at the same time stress intensification or flexibility factor tests are performed for a particular component. This paper describes the sustained stress index and the B31J test procedure used to determine the SSI. NOMENCLATUREde = elastic specimen displacement calculated from de = Fm / Ee. D = mean diameter of pipe Dnom = nominal diameter of pipe dn = displacement at the measurement point calculated from the elastic model of the test assembly used to find the elastic constant G 1
Part 1 of this paper was presented by Mr. Chris Hinnant at the 2008 PVP Conference in Chicago. Since 2008 additional fatigue test data has become available to the Paulin Research Group (PRG) which includes tests on unreinforced fabricated tees intended to support the fatigue curve approach established in the 2008 paper, and twenty-five additional straight pipe cantilever fatigue tests on carbon, stainless, duplex, CuNi, P91, X42 and X65 materials. These more recent experimental results confirm the fatigue slope recommended for cantilevers in the 2008 paper, but suggest that the original Markl slope may be more suited for some configurations of branch connections. Comparisons of the B31 Code allowable with failure data, tests, reviews of ratcheting behavior in pipe systems, and crack growth monitoring help draw conclusions about design equations in the B31 Codes and fatigue test procedures.
This paper presents the results of a small sample of ASME B16.9 welding tee burst tests. The intent of this study was to make a comparison between what is commonly accepted in industry as a B16.9 welding tee to the burst test requirements of B16.9 paragraph 9. The tests conducted show that the current fabrication techniques and some accepted criteria for B16.9 certification can produce thin sections in the tee which do not meet the required burst test pressures. The test descriptions and results are presented as well as recommendations for future study and potential modifications to the ASME B16.9 standard to address the concerns.
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