EN 10204 3.1 vs 3.2

In a Manufacturing Data Book, the materials chapter is often the largest single category — and its entire value rests on one thing: traceability from the heat number stamped on the steel back to a certificate that proves what that steel is. The type of certificate decides how much independent assurance sits behind the numbers on that page.

Get the type wrong and the consequences are concrete. A reviewer or third-party inspector who finds a 2.2 where the specification demanded a 3.1 will reject the chapter — and a rejected materials chapter holds up the whole dossier, which in turn holds up the final payment milestone. Understanding EN 10204 is therefore not a paperwork detail; it is the difference between a clean handover and weeks of rework.

EN 10204 is the European standard titled "Metallic products — Types of inspection documents". It does not specify what a material must contain or how it must perform — that is the job of the product standard (for example EN 10025 for structural steel or EN 10216 for seamless tubes). EN 10204 specifies only the form of the document that accompanies the material, and how strongly its results are validated.

EN 10204:2004 defines four document types in everyday use. The first two are based on non-specific inspection; the last two on specific inspection. The table below summarises what each one means and who stands behind it.

Two independent ideas explain the whole table, and people routinely confuse them: (a) whether the testing is specific or non-specific, and (b) who validates the result. The next two sections take each in turn.

The single most important distinction in EN 10204 is not the number of signatures. It is whether the test results actually describe the material you received.

• Non-specific inspection (2.1, 2.2). The manufacturer carries out — or reports — testing on material produced to the same specification, but not necessarily the exact products delivered to you. It demonstrates that the production process generally meets the requirements. A 2.1 has no test results at all (just a declaration); a 2.2 includes results, but from non-specific testing.
• Specific inspection (3.1, 3.2). The testing is carried out on the actual products delivered, or on the test unit of which they form part, before delivery. The results on the certificate describe your steel, traceable by heat or batch number.

So the jump from 2.2 to 3.1 is not "one more signature" — it is the jump from "this is what our material is usually like" to "this is what your material actually is." That is why product standards and pressure codes draw the line there for anything load- or pressure-bearing.

A 3.1 certificate is the workhorse of pressure-equipment and fabrication documentation. It reports the results of specific inspection on the delivered material and is validated by the manufacturer's authorised inspection representative — a person who, under the standard, must be independent of the manufacturing department. That independence is what gives a 3.1 its weight: the people who made the steel are not the people who sign off that it conforms.

A typical 3.1 certificate (issued as a mill test certificate) records:

• Heat / cast analysis — the chemical composition (C, Si, Mn, P, S, Cr, Ni, Mo, and so on)
• Mechanical properties — yield strength, tensile strength, elongation, and where required Charpy V-notch impact values
• Heat-treatment condition — e.g. normalised, quenched and tempered
• Heat / batch number — the traceability key that links the certificate to the physical material
• Dimensions, product form and the governing product standard (e.g. EN 10025-2 S355J2+N)

For the majority of European pressure-equipment and structural work, a 3.1 is the default requirement for the main load- and pressure-bearing components. In offshore and oil & gas scope, though, client specifications frequently escalate critical items to 3.2 — see our guide to MRB software for oil & gas.

A 3.2 certificate contains exactly the same specific test results as a 3.1 — same chemistry, same mechanical properties, same traceability. What is added is a second, external layer of validation. Beyond the manufacturer's independent inspection representative, a 3.2 must be countersigned by one of:

• the purchaser's authorised inspection representative, or
• an inspector designated by official regulations — in practice a notified body or a third-party inspection (TPI) agency.

A 3.2 is typically required when:

• the material is safety- or fracture-critical, and the client wants independent eyes on every figure;
• the client specification or project quality plan explicitly calls for 3.2;
• a notified body or TPI is already embedded in the conformity route and witnesses or reviews the material testing;
• under PED, the material manufacturer does not operate an appropriate quality-management system (see the next section).

Because a 3.2 requires an outside party to witness or review and sign, it costs more and takes longer to obtain. Specifying 3.2 where the code and contract only need 3.1 is a common — and expensive — over-specification.

The Pressure Equipment Directive (PED) 2014/68/EU is where the 3.1 vs 3.2 question gets most practical for European fabricators. As a general rule, Annex I, section 4.3 requires that the materials used for the main pressure-bearing parts be accompanied by an inspection certificate to EN 10204 3.1 — provided the material manufacturer has an appropriate quality-assurance system, certified by a competent body established within the European Union.

Where the material manufacturer does not have such a certified system, the directive requires the higher assurance of a 3.2 certificate instead — bringing in the independent third-party validation described above.

There is also the case of materials that are not covered by a harmonised standard or a European approval: these may require a Particular Material Appraisal (PMA) as part of the conformity assessment, on top of the inspection-document requirement.

A Mill Test Certificate (MTC) — also called a Mill Test Report (MTR) or simply a material certificate — is the document a steel mill or material manufacturer issues to certify a batch of material. It is the single most common document in the materials chapter of any data book.

Here is the distinction that trips up most people: "EN 10204 3.1" is not a different document from an MTC. The MTC is the document; "3.1" is the type and validation level it is issued to. A mill test certificate is normally certified to EN 10204 3.1, and sometimes to 3.2. So when a purchase order asks for "material with 3.1 certificates", it is asking for mill test certificates validated to the 3.1 level.

A handful of errors account for most rejected materials chapters. Knowing them upfront saves a review cycle.

• Accepting a 2.2 where a 3.1 was required. A 2.2 reports non-specific testing — it does not describe your actual material — and is not acceptable for pressure-bearing parts under most codes.
• Heat-number mismatch. If the heat number on the certificate does not match the marking on the physical material (or the traceability record), the document is worthless — and a TPI will flag it instantly.
• Over-specifying 3.2. Demanding 3.2 on non-critical items when the code only needs 3.1 adds cost and lead time for no compliance benefit.
• Quoting the old 1991 sub-types. Purchase specifications still occasionally ask for "3.1.B" — a designation that no longer exists (see below).

The 1991 → 2004 change

The current standard is EN 10204:2004. The earlier EN 10204:1991 defined more sub-types — including 3.1.A, 3.1.B and 3.1.C alongside 3.2. The 2004 revision simplified the landscape:

• the former 3.1.B became today's 3.1;
• the former 3.1.A and 3.1.C (which involved an independent organisation) were folded into 3.2;
• the old 3.2 was retained as 3.2.

So when a legacy drawing or framework contract references "3.1.B", in modern terms it simply means a 3.1. The practical risk is collecting documents against an obsolete requirement — exactly the kind of mismatch that surfaces late, when you are chasing suppliers for material certificates at the end of a project rather than at the start.