21. Section VIII–Division I: Rules for Construction of Pressure Vessels
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Section VIII, Division 1 is written for the construction of new pressure vessels, and it covers a wide range of industrial and commercial pressure vessel applications. It applies to small compressed air receivers as well as to very large pressure vessels needed by the petrochemical and refining industry. This chapter provides an overview to each of the parts of Section VIII, Division 1. It discusses the historical background of this Section in relation to the construction and safe operation of boilers and pressure vessels. Subsection A of Division 1 deals with the general requirements for all methods of construction and materials, covering design, inspection, and tests. Here, the requirements specific to the use of forgings, permitted material specifications for pipes and tubes, and requirements of prefabricated or preformed pressure parts are covered. Subsection B contains rules that apply to specific methods used for the fabrication of pressure vessels. The specific methods covered by Subsection B include welded construction, forging, and brazing. Subsection C deals with the requirements for pressure vessels: constructed of carbon and low alloy steels, nonferrous materials, high alloy steels, cast iron, and impregnated graphite; constructed of material with corrosion-resistant integral cladding, weld metal overlay, or with applied linings; and constructed of ferritic steels with tensile properties enhanced by heat treatment. Requirements are also provided for pressure vessels fabricated by layered construction and constructed of materials having higher allowable stresses at low temperature. Mandatory appendices include supplementary design formulas, rules for the design of bolted flanged connections that use gaskets that are entirely within the bolt circle, and rounded indications that are discovered by radiographic examination of welds. The basis for establishing allowable loads for tube-to-tubesheet joints and suggested methods for obtaining the operating temperature of vessel walls in service are covered under nonmandatory appendices.