PD 5500, the UK’s national pressure vessels code, has played a pivotal role in ensuring the safe and efficient design, manufacture, inspection, and testing of unfired pressure vessels for nearly five decades.

As it approaches its 50th anniversary in 2026, the launch of the PD 5500:2024 edition and its latest update - Amendment 2 (A2:2025) - marks a significant milestone in the ongoing evolution of this critical industry standard.

This article explores the scope, relevance, and technical advancements of PD 5500, and outlines why it remains essential for engineers, designers, manufacturers, and inspectors working with pressure equipment across diverse industries.

Understanding the evolution and scope of PD 5500

Originally published as BS 5500 in 1976, the standard unified sector-specific UK pressure vessel requirements under one comprehensive code. Renamed PD 5500, the standard continues to guide the industry with robust and updated technical provisions.

The scope of PD 5500 covers:

• Design, construction, inspection, testing, and verification of unfired pressure vessels.

• A wide range of materials including carbon, ferritic alloy, and austenitic steels.

• Supplementary requirements for vessels made from aluminium, copper, nickel, titanium, and duplex materials.

Though developed as a UK national standard, PD 5500 is widely used globally, particularly in:

• Commonwealth/former Commonwealth countries.

• The Middle East.

• Asia (including China and Malaysia).

It is regularly used alongside other global codes such as ASME BPVC (US) and BS EN 13445 (Europe), depending on contractual or regulatory requirements.

Who uses PD 5500 and why?

PD 5500 is designed for professionals and organizations involved in pressure vessel lifecycle management, including:

• Mechanical engineers and designers.

• Manufacturers and fabricators.

• Inspection and testing bodies.

Its users span multiple industries, notably:

• Oil and gas.

• Petrochemical and chemical processing.

• Power generation, including nuclear.

• Process plants.

• Food and drink manufacturing.

The code provides trusted guidance for safety-critical equipment, helping users meet both technical requirements and regulatory obligations such as the UK’s Pressure Equipment (Safety) Regulations (PE(S)R).

What’s new in PD 5500:2024+A2:2025?

The 2024 edition introduced a new three-year publishing cycle:

• The base document (PD 5500:2024).

• Amendment 1 (A1:2024) – Published September 2024.

• Amendment 2 (A2:2025) – Published September 2025.

• Amendment 3 (A3:2026) – Scheduled for September 2026.

The recently published PD 5500:2024+A2:2025 introduces key updates and innovations, including:

Technical and material updates:

• Revisions to BS EN materials in Table 2.1-2.

• New duplex materials for castings and fittings (Tables Du.2.1-2, Du.2.1-3).

• Addition of nickel alloys for forgings, castings, and fittings (Table Ni.2.3-6).

• Updated modulus of elasticity values for nickel alloys (Table Ni.3.6-3).

Design clarifications and drawing improvements:

• Updated nozzle reinforcement procedures.

• Clarification of effective lengths and associated figures and tables.

• Corrections to floating head exchanger drawings (Figures 3.9-1, 3.9-9).

• Clarification and correction of footnotes and stress limits.

New enquiry cases:

• EC 145: Introduces guidance for additive manufacturing using wire-based DED Arc techniques, enabling compliance with UK PE(S)R and supporting UKCA/CE marking.

• EC 147: Provides design rules for nozzle reinforcement in the knuckle region of dished ends, supporting more flexible vessel configurations.

These updates reflect the industry’s push toward innovation, while maintaining a strong focus on compliance, clarity, and usability.

Why choose PD 5500?

PD 5500 continues to serve as a comprehensive reference for the design and assessment of pressure vessels. Key benefits include:

• Consolidated and regularly updated technical content.

• Detailed guidance aligned with UK and global regulations.

• Coverage of emerging technologies, including additive manufacturing.

• Applicability across sectors and international markets.

Its wide acceptance, sector versatility, and clear design framework make it a go-to resource for those seeking to design safe, efficient, and legally compliant pressure equipment.

A living standard: Built by industry for industry

PD 5500 is maintained through ongoing collaboration with experts across manufacturing, design, inspection, and academia. Contributions from users and committee members shape its amendments, ensuring it evolves in response to real-world needs and advances in engineering.

This makes PD 5500 not only a safety code, but a reflection of best practice across the pressure vessel lifecycle.

Add PD 5500:2024+A2:2025 to your collection today.

Discover BSI Knowledge

Over 100,000 internationally recognized standards are available for simple and flexible access with a BSI Knowledge subscription. Our tailored subscription service allows you to build your own custom collection of standards or opt for access to one of our pre-built modules, keeping you up to date with any changes. With support from a dedicated BSI account manager, our subscription service helps you achieve a more coherent and effective approach to best practice. Request to learn more.