**What is PD 5500 - 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+A3:2022 is the third annual update to the 2021 edition of the code.

**Who is PD 5500 - 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 - 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.

PD 5500:2021+A3:2022 brings together all the content released as amendments to the 2018 edition of the code, repackaged to start the new three-year publishing cycle, plus the latest amendments generated by committee members and user enquiries regarding the 2021 edition.

**Why should you use PD 5500 - Unfired pressure vessels?**

It’s an invaluable reference tool for the design and assessment of pressure vessels
Its use produces safer, more cost-effective pressure vessels
Subscribers receive an annual update each September
It can help users enter new markets, trade, increase trust and improve risk management
This version consolidates all the latest corrections, clarifications and technical changes that keep the code up-to-date, accurate and user-friendly

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.

PD 5500:2021+A3:2023 - SET

Specification for unfired pressure vessels

Published:

30 Sep 2021

Withdrawn:

31 Jan 2024