EN 10204 3.1 MTC Explained: What Offshore and Pressure Vessel Buyers Must Check Before Accepting Steel
Short answer
An EN 10204 3.1 inspection certificate is a test certificate issued by the steel manufacturer’s inspection function, which is independent of the production department, and it is tied to the specific heat number of the material delivered. Its practical value is not that “a certificate exists” — it is that the certificate can be cross-checked against the mill’s own record for that heat.
That distinction is what separates a 3.1 certificate from a 2.2 test report, and it is the single most useful thing a buyer can verify before accepting steel for offshore, oil and gas, or pressure vessel applications.
2.2 vs 3.1 vs 3.2: the difference that matters
| Document | Issued by | Tied to specific heat? | Independence | Where it is accepted |
|---|---|---|---|---|
| 2.1 | Manufacturer | No | Declaration of compliance only | Non-safety, general fabrication |
| 2.2 | Manufacturer | No — based on non-specific inspection | Manufacturer only | Low-risk structural work, buyer discretion |
| 3.1 | Manufacturer’s inspection function, independent of production | Yes | Manufacturer, independent of production | Pressure equipment, offshore, most engineering specs |
| 3.2 | Manufacturer’s inspection function plus an independent third party | Yes | Manufacturer + independent inspector | Highest-integrity applications, where the spec names a third-party endorser |
The core distinction in one line: a 2.2 report tells you the manufacturer tested material of this type; a 3.1 certificate tells you what was tested, from which heat, and by whom — and it can be verified.
Most project specifications in offshore and pressure vessel work will not accept 2.2. If your supplier offers it as equivalent, that is a signal to check the specification language before signing.
The seven checks to run before you accept the goods
Print this list. It is written to be used at goods-in, not at the desk.
| # | Check | What you are looking for | Red flag |
|---|---|---|---|
| 1 | Heat number | Certificate heat number = marking on the plate / bundle = heat number on the packing list | Any mismatch, or a certificate that lists a range of heats |
| 2 | Chemical composition | Full ladle analysis, with the elements your spec controls (C, Mn, Si, P, S + any alloying additions) | Missing elements, or values only in “typical” form |
| 3 | Mechanical properties | Yield, tensile, elongation on the actual heat | Values quoted as ranges rather than measured results |
| 4 | Impact test temperature | Test temperature matches the design minimum, not room temperature | Impact test at +20 °C on a cold-service specification |
| 5 | UT level | Ultrasonic acceptance level stated explicitly | “UT passed” with no level or standard cited |
| 6 | Dimensional check | Measured thickness and profile against the order | Thickness at the negative tolerance limit with no discussion |
| 7 | Standard referenced | The product standard is named (EN, ASTM, GB, GOST as applicable) | Certificate references an internal standard only |
Point 5 is where a lot of documentation quietly fails. An ultrasonic test is only meaningful when the acceptance level is stated, because the level defines the size and type of discontinuity that is permitted. On the offshore and pressure-retaining applications we serve, ultrasonic testing at S2 E2 level is applied as a mandatory requirement rather than an option, and the report is issued against the same heat number as the material certificate.
Why UT S2 E2 is mandatory, not optional
On offshore and pressure-retaining components, the failure that matters most is not surface wear. It is internal discontinuity — a lamination or inclusion that stays invisible until the part is loaded in service.
Ultrasonic testing at S2 E2 level is mandatory on our shipments for these applications. In practice this means:
- Internal soundness is verified against a defined acceptance level, not by visual inspection.
- The result is documented and travels with the heat number.
- Non-destructive testing is complemented by on-site hardness testing and metallographic analysis, so the surface claim and the internal structure are both evidenced.
The reason the level matters commercially is that it defines what a buyer is entitled to reject. Without a stated level, a supplier can always argue that the indication found at goods-in was acceptable; with a stated level, acceptance becomes a measurable question rather than a negotiation.
The Russian and CIS dimension: technical passports and GOST 2.601
For projects in Russia and the CIS, material acceptance takes an additional step that many international suppliers do not plan for: technical documentation in Russian.
We issue technical passports in Russian, compliant with GOST 2.601. Practically, this means your engineering team receives documentation it can file and audit without commissioning a translation — which shortens the acceptance cycle and removes a common cause of goods sitting in the yard.
Payment settlement for Russian projects
We settle through the VTB Shanghai Branch, keeping the transaction in a channel established for this trade corridor and reducing sanction-related exposure. The route that applies to a specific contract is confirmed individually with our commercial team, because what is workable depends on the project structure and the parties involved.
A note on what a certificate cannot do
A 3.1 certificate is evidence of what the mill tested and reported. It is not evidence of:
- How the plate was stored after it left the mill
- Whether the heat number marking survived handling and transshipment
- Whether cutting introduced a heat-affected zone that changed local properties
Those three items are controlled by the supplier and the fabricator, which is why buying from a supplier who also fabricates — and who therefore owns the whole chain — removes an entire class of dispute.
Frequently asked questions
Is EN 10204 3.1 the same as a “mill certificate”? Broadly, a mill certificate is a generic term. EN 10204 3.1 is a specific document type with a defined issuer and heat-level traceability. Ask for the type, not the generic term.
Can you issue 3.2 certificates? We issue 3.1 certificates against the original heat. Where a project specification calls for 3.2, the third-party endorsement is arranged through the inspection body named by the project, with scope, cost and schedule agreed before the order is placed.
Do you supply seamless pipe as well as plate? Send us the grades, sizes and the project standard. We will confirm what can be supplied from the mill sources we work with, and in which product form, before any quotation is issued.
What thickness and grade range is available for pressure vessel work? It is confirmed per project rather than quoted as a generic catalogue range, because availability follows the specification and the mill source. Send the design standard, the grade designation and the thickness list, and we will return a confirmed availability statement.
How do you handle UT and third-party inspection? UT S2 E2 is mandatory on our offshore and pressure applications, with reports issued against the heat number. Where a project requires third-party witnessing, it can be arranged through the inspection body named in the specification.
Do you have experience with Russian documentation requirements? Yes — technical passports in Russian, compliant with GOST 2.601, issued as part of the documentation set for Russian and CIS projects.
Request a compliance cross-check for your project
Tell us the project standard, the destination country, and the required documentation set. We will return a material and documentation compliance cross-check — what we can supply, what the certificate set will contain, and where any gap remains.
Nanjing Tiange Metal Trading Co., Ltd. Email: postmaster@tigosteel.com Phone / WhatsApp / Telegram: +86 138 1389 7227 Web: www.tigosteel.com Nanjing, Jiangsu, China