Computer Based Process Piping Stress Analysis: ASME B31.3 Appendix S — Example S1

Abstract

The American Standards Association (ASA) B31.3-1959 Petroleum Refinery Piping Code [1] grew out of an ASA document that addressed all manner of fluid conveying piping systems. ASA B31.3 was created long before widespread engineering use of computer “mainframes” or even before the inception of piping stress analysis software. Also as B31.3 continued to pass thru standards organizations from ASA, ANSI, to ASME, the B31.3 Process Piping Code [2] (hereafter referred to as the “Code”) has remained ambiguous over the past few decades in several areas. Ambiguities such as what temperatures and pressures are to be used during the pipe stress analysis process is addressed but apparently not clearly enough to make the point; the prevailing practice in the industry is to use the design pressure and temperature; but this is an incorrect inference from the Code. The misunderstandings as to the few, albeit very important, purposed uses for the design pressure and design temperature also appear to be prevalent in the industry. This paper describes some of these subtle yet possibly radical concepts that were included in the ASME B31.3-2004 Appendix S Example Sl. This paper discusses: • the design and analysis procedures in defining when the design conditions are actually to be used; • when and in what manner the most severe set of operating temperature and pressure is to be used; • and the debates that lasted over a decade to finally include into the Code such “seemingly simple” examples that address computer based stress analysis.