WRC 392:1994

$26.65

Part 1: Developing Stress Intensification Factors: Standardized Method for Developing Stress Intensification Factors for Piping Components; Part 2: Developing Stress Intensification Factors: Effects of Weld Metal Profile on the Fatigue Life of Integrally Reinforced Weld-On Fittings

Published By	Publication Date	Number of Pages
WRC	1994	34

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Description

Part 1: Developing Stress Intensification Factors: Standardized Method for Developing Stress Intensification Factors for Piping Components

The study described in the first paper of this Bulletin was initiated in 1990 by the PVRC Design Division?s Committee on Piping and Nozzles (formerly the Subcommittee on Piping, Pumps, and Valves) under PVRC Grant No. 90-9 to Mr. Rodabaugh. The study was conducted in response to an informal request from the ASME Boiler and Pressure Vessel Committee, Working Group on Piping (WGPD)(SGD)(SC-III) to document the method to be used in the experimental determination of stress intensification factors (i-factors) for piping components and joints. Although a significant number of studies and tests have been conducted over the years, beginning with the Markl testing of the 1940's, there was no universally accepted method to follow if one had need of an i-factor which did not appear in the ASME-B31 piping codes or Section III of the ASME Boiler and Pressure Vessel Code. As a most significant contributor to the development of i-factors, Mr. Rodabaugh was chosen to develop such a procedure.

In developing the proposed Appendix for Section III, Mr. Rodabaugh has reviewed what the i-factor represents and how it fits into the fatigue analysis concepts of Class 2 and 3 piping of Section III (and the ASME-B31 piping codes). In doing so, he points out the approximations of the code fatigue analysis methodology, which is an added benefit to this study. That portion of the report should be of significant interest to both the ASME Boiler and Pressure Vessel Committee and the ASME B31 Mechanical Design Committee.

Part 2: Developing Stress Intensification Factors: Effects of Weld Metal Profile on the Fatigue Life of Integrally Reinforced Weld-On Fittings

The cyclic fatigue life of fabricated tee intersections, including integrally reinforced weld-on fittings, has been a topic of discussion in the recent past. The discussion has centered around questions concerning the accuracy of the Code equations in calculating the stress intensification factors, (SIFs), for these types of intersection geometries. The SIF of an intersection is an indicator of the fatigue life of the intersection when it is subjected to bending moments caused by thermal, flow, or mechanically induced cyclical displacements. Schneider, 2 Rodabaugh, and Woods concur that inaccuracies in the Code SIF equations do exist and that these equations should be revised.

This report presents new Markl type SIF data on the B. W. Pipet, (BWP), an integrally reinforced weld-on branch fitting, manufactured by WFI International, Inc, in Houston Texas. The scope of this research project was to determine the influence of the installation weld metal profile of the Pipet to the run pipe on the SIF. The SIF data were then compared to calculated SIF values using equations from the American Society of Mechanical Engineers (ASME) B31.1, ASME B31.3, and ASME Section III, Subsection NC, for the purpose of determining which Code equation may be the most appropriate for calculating the SIF for these particular fittings.

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