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Part 1: Evaluation of Small (r/R<0.5) Branch Connections with Through-Run Moments: Run Moment Fatigue Tests on Pipes with Small (d/D) Branch Connections

Small branch connections are frequently installed on piping systems for the attachment of vent, drain, test and instrumentation connections. The ASME and ANSI piping design codes provide stress intensification factors i (SIF) to guide the piping designer on the design of such components. Appendixes A, B and C are copies of the ASME and ANSI subsections pertinent to this area. In summary, the ASME Code requires i to be no less than 1.5 and the calculated i must be doubled (minimum of 2.1) for a component without sufficient branch to run radius r₂ (per ASME NC 3673.2(b)-2). Since there is no such control of r₂ in the tests described in this report an index of no less than 2.1 would be required. The ANSI SIF's for this type of connection are equal to 0.9h2/3 which is approximately 1.7 for the component tested in this report. For ANSI B31.1 an SIF of 1.0 could possibly be applied for the run-side loads of a branch connection since the SIF indicates only "for checking branch ends." The goal of this program was to obtain run moment bending fatigue test data on such connections. The tests are displacement controlled 4-point bending tests on 4" schedule 40 carbon steel pipe, type A106-B with three types of branch connections. This configuration was selected due to the extensive amount of test data on similar pipes by Markl and to meet the requirements of reference 7 in this report.

Part 2: Evaluation of Small (r/R<0.5) Branch Connections with Through-Run Moments: Evaluation of Branch Connections with r/R Less than 0.5 Subjected to Through-Run Moment Loadings

Until recently, there were no available through-run moment fatigue tests on branch connections with r/R < 1.00. This report describes and gives results of recently completed, through-run moment fatigue tests on branch connections with r/R between 0.1 and 0.25. These tests were made to assist in examining the validity of Code methods for evaluating the adequacy of branch connections loaded by cyclic, through-run moments. The fatigue test results, in conjunction with available theoretical and measured stress data, lead to suggested changes in the Code; these are shown in Section 6.2 of this report. Section 2 describes the background and present status of Code requirements for evaluation of through-run moments on branch connections. It also indicates the major motivation for review of the requirements by example of a 30 in. pipe with a 1 NPS drain line. Section 3 describes the fatigue tests and their evaluation in terms of i-factors, for Class 2/3 piping, and in terms of C2r and K2r, for Class 1 piping. Section 4 describes the available theoretical and measured stress data on branch connections with through-run moment loadings. The theory is used to extrapolate the test data over the range of parameters intended to be covered; i.e., R/T<50, r/R<0.50 and t/T>0.5(r/R). Section 5 develops the suggested changes to Code requirements for evaluation of branch connections subjected to through-run moment loadings. These include suggested changes to equations for i, C2r, K2r and B2r. Section 6 summarizes the motivations and available data, as well as the suggested Code changes.

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Published: 1998 Number of Pages: 44 File Size: 1 file , 3.2 MB