PD 5500: Specification for unfired, fusion welded pressure vessels.
Provided by the British Standard Institute (BSI), PD 5500 is a code of practice that specifies requirements for the design, fabrication, and inspection of pressure vessels in the oil and gas, petrochemical and energy generation (including nuclear) industries.
PD 5500 was formerly a widely used British Standard known as BS 5500, but was withdrawn from the list of British Standards because it was not harmonized with the European Pressure Equipment Directive (97/23/EC). In the United Kingdom, it was replaced by EN 13445. It is currently published as a "Published Document" (PD) by the British Standards Institution.
The specification covers pressure vessels connected to piping by bolts, screws or welding, as well as supports, brackets and other direct attachments. It applies to vessels that are subject to electrical heating or heated process streams, but not vessels exposed to direct heat or flame.