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Chapter 11
Standard Pressure Parts, Valves, and Valve Ratings

Excerpt

The rules dealing with standard pressure parts and how they may be provided are found in PG-11, Miscellaneous Pressure Parts. Ordinarily, Section I requires all pressure parts to meet applicable requirements for material, design, fabrication, welding, inspection, testing, and certification by stamping and data reports. These comprehensive Code construction requirements are considered necessary to ensure safe construction. Considerable relief from this burden is granted in the case of what are called standard pressure parts, provided these parts are designed and manufactured in such a way as to provide an equivalent assurance of quality and safety. Under these circumstances, mill test reports, inspection by an Authorized Inspector, and Partial Data Reports are not required.

Among the parts included in the category of standard pressure parts are such components as: pipe fittings, valves, flanges, welding necks, welding caps, manhole frames and covers, and the casings of certain pumps. Most of these parts are readily available as stock items in a variety of sizes. They do not have to be designed for each specific application because the manufacturer has already established pressure and temperature ratings for them.

Section I establishes several categories of these parts. One category covers pressure parts which are cast, forged, rolled, or die-formed (i.e., not welded). Within this category, Section I designates two types: parts that comply with an ASME (formerly ANSI and later ASME/ANSI) Standard accepted by reference in PG-42 and parts that comply with a parts manufacturer's standard. There are some differences between the two in material and design requirements. Parts complying with a parts manufacturer's standard must be made of material explicitly permitted by Section I, but parts complying with an ASME standard may, in addition, be made of materials listed in that standard, provided Section I does not prohibit or otherwise limit the use of such materials. The ASME standard also establishes the basis for their pressure and temperature rating and specifies the marking on them; these ratings and markings are accepted by Section I. Some difficulties have arisen in recent years if the standard pressure part is not made of a material explicitly approved for Section I construction in Section II, Part D. This situation is explained in Chapter 3, Materials.

  • Standard Pressure Parts
  • Valve and Valve Ratings

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