This Published Document specifies requirements for the design, construction, inspection, testing and verification of compliance of new unfired pressure vessels. The materials of construction are specified in Section 2. The term "pressure vessel" as used in this specification includes branches up to the point of connection to the connecting piping by bolting, screwing or welding, and supports, brackets or other attachments directly welded to the pressure containing shell. The term "unfired" excludes vessels that are subject to direct generated heat or flame impingement from a fired process. It does not exclude vessels subject to electrical heating or heated process streams.Incorporates the following:PD 5500:2021 PDF