The ASME B31.3 Code has certain organizational features that, when understood, make it easier to follow. The Code consists of nine chapters. The first six chapters are what is called the base Code. It provides the basic piping Code requirements for Normal and Category D fluid service metallic piping. Chapter VII contains rules for nonmetallic piping and additional requirements for metallic piping lined with nonmetals. Chapter VIII contains rules for piping in Category M Fluid Service.
Chapter IX contains rules for high-pressure piping. This Chapter is never a required selection. It is always the option of the owner to select the use of Chapter IX. Although the Code provides a guideline stating that high pressure can be considered to refer to over Class 2500 flanges, this is not a requirement, and the base Code may be satisfactorily used to pressures higher than this.
The paragraphs in the Code follow a specific numbering scheme: Paragraphs are designated in the 300 range. The 300 series paragraphs are exclusive to the ASME B31.3 Code Section of the ASME B31 Code for Pressure Piping. The paragraph numbers in the base Code are repeated in Chapters VII through IX. Those paragraphs are differentiated by a letter placed in front of the paragraph numbers in each case. Chapter VII uses the letter A, Chapter VIII uses the letter M for metallic piping and MA for nonmetallic piping, and Chapter IX uses the letter K.
Using the same paragraph numbers permits easy cross-referencing between each of the last three chapters and the base Code requirements. The last three chapters refer back to base Code requirements whenever they are applicable. In this arrangement, the same requirements need not be repeated multiple times. Also, these three chapters tell users whenever they need to refer back to base Code requirements. #Little _PEng
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