**What is PD 5500:2021+A3 - Specification for unfired pressure vessels about?**

PD 5500 is the UK’s national pressure vessels code, a new edition of which is published every three years. In 2021 the code started a new three-year publishing cycle during which an annual update is published in the form of an amendment every September. PD 5500:2021+A3:2023 is the third annual update to the 2021 edition of the code.

**Who is PD 5500:2021+A3 - Specification for unfired pressure vessels for?**

Mechanical engineers
Pressure vessel designers and design consultancies
Pressure vessel manufacturers
Pressure vessel inspection bodies in the oil and gas, petrochemicals, process plant and energy generation (including nuclear) industries

**What does PD 5500:2021+A3 - Specification for unfired pressure vessels cover?**

PD 5500 specifies requirements for the design, manufacture, inspection and testing of unfired pressure vessels made from carbon, ferritic alloy, and austenitic steels. It also includes material supplements containing requirements for vessels made from aluminium, copper, nickel, titanium and duplex.

This latest version of the code, PD 5500:2021+A3:2023 provides the most recent amendments generated by committee members and user enquiries, including the September 2021 and September 2022 updates.

**Why should you use PD 5500:2021+A3 - Specification for unfired pressure vessels?**

PD 5500 is an invaluable reference tool for the design, fabrication, inspection and testing of pressure vessels of a consistently high quality.
Safety critical. This specification enables the production and testing of pressure vessels so they comply with safety regulations and helps reduce the risk of accidents.
Risk mitigation. PD 5500 reduces the likelihood of failures that could lead to personal injury, property damage or environmental hazards.
Over many decades, PD 5500 has become well established and globally recognized. It can help users increase confidence in their products, enter new markets and trade more easily.
This version consolidates all the latest corrections, clarifications and changes that help clarify and improve the wording of the document, as well as introducing new technical requirements based on technological and other changes.

What’s new about PD 5500:2021+A3:2023?

The major technical and editorial changes in Amendment 3 to PD 5500:2021 (PD 5500:2021+A3:2023) are:

the addition of live loads on ladders
revisions to the calculation of the pressure loaded area Ap in Figures 3.5-32 a) to f)
clarification of the requirements for bolted circular flat ends
the addition of limitations on the hub slope for bolted flanges
clarification of the limits for stresses due to local loads on attachments, supports and nozzles
the inclusion of guidance regarding the calculation of allowable longitudinal compressive membrane stress at temperatures other than the design temperature
clarification of the definition of design pressure in Annex B
the addition of guidance on the loadings to be considered in the calculation of stresses in Annex B
clarification of the calculation of principal stresses in Annex B
revisions to the weld details for welding neck flanges in Annex E
the inclusion of a calculation for pressure stress for local loads on rigid attachments on spherical shells
the addition of requirements for approval testing of welders or operators in Annex T, based on the requirements of BS 4871-3
revisions to the requirements for heat treatment in the nickel supplement
updates to the guidance links in Annex Z.

Additionally various internal and external references have been updated.

BS 1502:1968

Specification for steels for fired and unfired pressure vessels: sections and bars

Published:

31 Jan 1975

Withdrawn:

Date not available