A pressure vessel is a container designed to hold fluids or gases at a pressure significantly different from the ambient environment. These vessels are found across industries and are indispensable, but also potentially hazardous. They store large amounts of energy, and failure can be catastrophic.

A report presented to the World Congress on Engineering in 2010 recorded over 23,000 pressure vessel-related accidents between 1992 and 2001, an average of 2,334 incidents annually. More recently, UK RIDDOR data (2014–2020) reported 387 "dangerous occurrences" linked to pressure systems, highlighting the continued need for robust design, inspection, and compliance.

To mitigate these risks, manufacturers of pressurized systems, such as storage vessels, heat exchangers, piping, boilers, and safety devices, rely on internationally recognized standards to meet essential safety requirements and navigate complex conformity assessments.

Critical for safety: The UK’s pressure vessel code

In the UK, the national standard for unfired pressure vessels is PD 5500, a code first published in 1976 to unify the sector-specific standards that had existed since the 1950s. Now nearing its 50th anniversary (to be marked in 2026), PD 5500 continues to serve as a comprehensive, trusted source of technical guidance across multiple sectors.

The latest version, PD 5500:2024+A3:2026, marks the third and final amendment to the 2024 edition, which kicked off a new three-year publishing cycle in January 2024:

• Amendment 1 (A1) – Published September 2024

• Amendment 2 (A2) – Published September 2025

• Amendment 3 (A3) – Published September 2026

PD 5500:2024+A3:2026 specifies requirements for the design, manufacture, inspection, testing, and verification of compliance of new unfired pressure vessels made from carbon, ferritic alloy and austenitic steels. It also includes material supplements for vessels manufactured from aluminium, copper, nickel, titanium and duplex materials.

Amendment 3 introduces updated technical guidance, clarifications and a new enquiry case covering pressure vessels used in hydrogen service, helping you apply the latest industry requirements across both established and emerging energy applications.

What’s new in amendment 3 (PD 5500:2024+A3:2026)?

Amendment 3 builds on the 2024 edition with technical and editorial updates designed to improve accuracy, usability, and alignment with industry needs. Key enhancements include:

Technical clarifications and corrections:

• Clarification of the definition of coupling point.

• Additional notation and updates to technical figures.

• Corrections and improvements to symbols and notation throughout the code.

• Additions to limitations within Annex G.

• Corrections to existing enquiry case content and updates to internal and external references.

New enquiry case for hydrogen service:

• EC 148: Introduces additional recommendations for pressure vessels in hydrogen service. The enquiry case provides guidance on material considerations and service conditions that should be considered when designing, manufacturing, and testing vessels used in hydrogen applications.

Together, these updates reinforce PD 5500's role as a forward-looking code that responds to industry feedback, improves usability, and supports emerging energy applications.

A standard with global reach and sector-wide impact

PD 5500 is used not only across the UK but also in Commonwealth countries, the Middle East, and parts of Asia. It is a vital tool for manufacturers and engineers working in:

• oil and gas;

• petrochemicals;

• power generation, including nuclear;

• process plants; and

• food and drink manufacturing.

Its scope makes it a preferred standard among pressure vessel design consultancies, fabricators, and inspection bodies, particularly where UK compliance is required.

Why should you adopt PD 5500:2024+A3:2026?

Adopting PD 5500 ensures that pressure vessel systems are built to meet the highest standards of safety, reliability, and performance. Here's why it's essential:

• Provides a comprehensive reference for design, manufacturing, and compliance.

• Consolidates the latest industry updates, including new guidance for pressure vessels used in hydrogen service and a range of technical clarifications and improvements.

• Offers clarity in interpretation, improving safety and engineering efficiency.

• Helps organizations manage risk, increase market trust, and streamline compliance.

• Supports both domestic regulation and international competitiveness. 

Ensure your organization is working to the latest requirements for pressure vessel design, manufacture, inspection and testing by adding PD 5500:2024+A3:2026 to your collection today.

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