Full Description

It is well known that openings in pressure vessels constitute a major limitation in the use of higher allowable design stresses, and also constitute a potential source of failure for equipment subject to fatigue loading. Recognizing the importance of this problem, the Pressure Vessel Research Committee has, almost from its beginning, supported research in this field, considering the effects of both internal pressure and external piping loads. By 1955, in recognition of the importance of this problem to nuclear and other industries, a Subcommittee was appointed, with F. S. G. Williams as chairman, having as its assignment the development of a theory for reinforced openings. Development of such theory was to be based on present knowledge (as exemplified by classical shell theory) plus additional information obtained from tests. A three-pronged program was laid out as follows:

1. Project Location: Yale University; Project Director: Prof. E.O. Waters; Scope: Application of shell theory and photoelastic test of flat plate models.
2. Project Location: University of Illinois; Project Director: Prof. C.E. Taylor; Scope: Photoelastic test of cylindrical and spherical models with cylindrical outlets (internal pressure only).
3. Project Location: Penn State University; Project Director: Prof. D.E. Hardenbergh; Scope: Strain-gage tests on steel ("hard") cylindrical models with cylindrical outlets, loaded by internal pressure and (in some cases) by external piping loads.

Co-sponsors of this work, along with PVRC, were the Bureau of Ships (Department of the Navy) and the Atomic Energy Commission. The results of the first 2.5 to 3 years work under this program were published in Welding Research Council Bulletin No. 51.

During 1959-60, as the work progressed, it became clear that any "complete" solution of the problem would require several years' effort. The importance of the problem, as re-emphasized during this period by the ASME Boiler and Pressure Code Committee, led to an expansion of the experimental program by engaging the services of Westinghouse Research Laboratories, with M. M. Leven as project director and the American Gas Association as financial co-sponsor. This work consists of photoelastic tests to be carried out in parallel with those at the Univ. of Illinois.

The theoretical solution of the sphere-cylinder intersection is well known (at least for thin-walled vessels having nozzles with radial entry) and can be used as a basis for a solution of the "spherical shell problem." However, no corresponding theory seems readily applicable to the "cylindrical shell problem." The Subcommittee has engaged the services of Prof, A. C. Eringen of General Technology Corp. to explore the solution of this problem, which promises to involve much mathematical development and involved computation.

Also during the 1959-60 period, the Subcommittee established liaison for exchange of test data and interim reports with other research groups working under the American Gas Association, the British Welding Research Association and Babcock and Wilcox Ltd. (Great Britain). As a result of these contacts and the program planning required incident to the above program expansion, it became increasingly apparent to the Subcommittee that it should endeavor to develop a "total program plan" for work to be sponsored by PVRC on reinforced openings. Such a long-range program will promote more effective detail planning of individual projects and tend to minimize duplication of effort by various groups working on this problem.

In the following paragraphs, an outline of this program (past, present and future) is presented in some detail; this is followed by appendices wherein the available data are analyzed for the benefit of other workers in this field. Readers are cautioned that, in analyzing the data, certain extrapolations and conclusions have been drawn which are highly conjectural. It is believed that such conclusions may be valuable as guides for other investigators, but they are often based on limited data and are not necessarily correct; therefore, they should not be used quantitatively for design purposes. Whenever; possible, such questionable areas are pointed out in this report. It should also be restated that the primary purpose of this program is to establish a rational theory of reinforcement. The test vessels used represent idealized configurations, from which the problems of out-of-roundness, improper contour, poor fit-up, surface and weld defects have been eliminated insofar as possible. In addition, the work is aimed at a high quality of vessel construction for which integral reinforcement and full penetration welding are required. Therefore, all of the models tested will be of "integral" construction, except for one or two pad type reinforcements tested for comparison purposes. As a matter of information, both the American Gas Association and the British Welding Research Association have included extensive testing of other types of reinforcements in their programs.

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Published: 1962 Number of Pages: 60 File Size: 1 file , 2 MB