EN 10225 explained: product parts, grades and offshore scope

EN 10225 is the European standard family for weldable structural steels used in fixed offshore structures.

It is commonly encountered for:

• offshore oil-and-gas jackets and topsides;
• offshore wind foundations and other fixed offshore structures;
• heavy plate, rolled sections and structural tubular members where the project specification invokes EN 10225.

The most important first step is to understand that EN 10225 is no longer one single product document. The modern family is split by product form.

The four current product parts

As of September 2026, NEN lists Parts 1, 2 and 4 in their 2019 editions as current, while Part 3 is current as EN 10225-3:2019+A1:2023.

This is a structural offshore standard, not a pipeline standard

The hollow-section parts explicitly exclude steels supplied for subsea pipelines, risers, process equipment, process piping and other utilities.

That distinction is critical because offshore projects may contain both:

• structural tubulars; and
• line/process pipe.

The same project can therefore use EN 10225 for structural members and API/ISO/EN pipeline or pressure-pipe standards elsewhere.

See API 5L vs EN 10225 for offshore structural tubulars.

Why offshore structural steel needs a dedicated standard

Fixed offshore structures combine demanding fabrication and service conditions:

• large welded nodes and highly restrained joints;
• thick material;
• low design temperatures;
• cyclic/fatigue loading;
• high consequence of brittle fracture;
• extensive NDT and traceability expectations;
• project-specific supplementary requirements.

EN 10225 therefore places strong emphasis on toughness, weldability, delivery condition, testing and purchaser-specified options in addition to basic yield strength.

Understanding the newer grade names

Modern EN 10225 grades follow a systematic naming logic rather than the older S355Gx-style names that many buyers still remember.

For plate, examples include designations such as:

• S355NLO;
• S355MLO;
• higher-strength MLO or QLO grades depending on the applicable part.

The letters describe more than strength:

• S = structural steel;
• number = minimum specified yield-strength class for the reference thickness range;
• N = normalized/normalizing rolled route;
• M = thermomechanically rolled route where applicable;
• Q = quenched and tempered route where applicable;
• L = low-temperature impact requirement within the grade designation;
• O = offshore.

For the general N/M distinction, see N, NL, M and ML.

Hollow-section names add product-form letters

Part 3 uses additional letters for hollow-section/product condition.

The standard’s own designation example includes:

S355NLHHO

where the name identifies:

• S355 strength class;
• normalized/normalized-rolled low-temperature grade;
• hollow section;
• hot-finished condition;
• offshore application.

This is why an offshore tubular grade can look much longer than an ordinary S355 structural-steel designation.

Part 3 includes both seamless and welded material

This is a frequent source of confusion.

EN 10225-3 is not “the seamless part.”

The current Part 3 scope covers hot-finished seamless and high-frequency-welded (HFW) hollow sections.

Part 4 covers cold-formed welded hollow sections, including SAW and HFW routes within its defined limits.

Manufacturing route therefore has to be checked against the correct product part rather than inferred from the grade name alone.

The older S355G grades still appear in documents and stock

Projects, MTCs and older stock may use previous-generation EN 10225 designations such as S355G7, S355G8, S355G10, S355G13 or S355G14 with delivery-condition suffixes.

The 2019 restructuring changed the naming system and divided the standard into four parts. DIN notes that the third edition substantially changed the concept and aligned the steel short names with EN 10027-1.

Therefore an old and new designation should not be matched from memory alone. Check the applicable standard edition and the documented predecessor/successor relationship.

Impact toughness is central

NEN’s public scope descriptions for the EN 10225 parts include impact properties at temperatures down to -40 °C for applicable grades.

But the exact Charpy requirement depends on:

• product part;
• grade;
• thickness;
• specimen orientation;
• option/project requirement;
• test frequency and sampling.

See Impact testing of structural plate.

NDT and through-thickness requirements are separate order decisions

An EN 10225 grade name does not by itself tell you every UT or through-thickness requirement that the project may impose.

Plate projects commonly add specific UT classes or Z-quality requirements depending on the joint design and specification.

See EN 10160 ultrasonic testing of steel plate.

Certificate type does not replace the technical specification

Offshore projects commonly request EN 10204 3.1 or 3.2 documentation, but the certificate type only tells you how inspection results are validated/documented. It does not define the material grade, toughness, NDT or supplementary tests.

See EN 10204 3.1 vs 3.2.

What should be stated in an EN 10225 RFQ?

At minimum, state:

1. the exact EN 10225 part and edition required by the project;
2. product form;
3. exact grade designation;
4. dimensions, tolerances and lengths;
5. delivery condition/manufacturing route;
6. impact-test requirements and any options;
7. UT/NDT requirements;
8. through-thickness/Z-quality requirements if applicable;
9. inspection document type;
10. marking and traceability;
11. any project/company specification added above EN 10225.

A line saying only “S355 offshore steel” is not enough.

MetalMate takeaway

EN 10225 is a four-part structural-offshore steel family, not one generic offshore grade. Start with the product form and correct part, then the grade/delivery route, then project options for toughness, NDT, through-thickness properties, certification and traceability. For tubulars, remember that Part 3 includes both seamless and HFW hot-finished hollow sections, while Part 4 covers cold-formed welded routes.

Related Knowledge

• API 5L vs EN 10225 for offshore structural tubulars
• N, NL, M and ML
• Impact testing of structural plate
• EN 10160 plate UT
• EN 10204 3.1 vs 3.2

References

• NEN, EN 10225-1:2019 — Plates: https://www.nen.nl/en/nen-en-10225-1-2019-en-259391
• NEN, EN 10225-2:2019 — Sections: https://www.nen.nl/en/nen-en-10225-2-2019-en-259392
• NEN, EN 10225-3:2019+A1:2023 — Hot finished hollow sections: https://www.nen.nl/en/nen-en-10225-3-2019-a1-2023-en-311495
• NEN, EN 10225-4:2019 — Cold formed welded hollow sections: https://www.nen.nl/en/nen-en-10225-4-2019-en-259394
• DIN Media, EN 10225-3 background on the four-part restructuring and legacy designations: https://www.dinmedia.de/en/standard/din-en-10225-3/361426976