Mill test certificates (MTCs) are among the most important documents in any metal procurement transaction. They prove that the material supplied meets the chemical and mechanical properties specified in your purchase order. EN 10204 is the European standard that defines how these documents must be structured, who can issue them, and what level of independent validation is required. Understanding the difference between a Type 3.1 and 3.2 certificate — and specifying the right one — can be the difference between a smooth project inspection and a costly material rejection.
What is EN 10204?
EN 10204:2004 (superseding EN 10204:1991) is the standard for "Metallic products — Types of inspection documents." It applies to a wide range of metallic products including stainless steel pipes, plates, flanges, fittings, and fasteners. The standard defines four document types, each with increasing levels of validation and traceability.
The Four Document Types
Type 2.1 — Declaration of Compliance
A simple written statement by the manufacturer that the products supplied meet the requirements of the order specification. No test data is included. This is the minimum level of documentation and is acceptable only for non-critical, non-safety applications — general structural steel, standard fasteners for non-hazardous service, etc.
Type 2.2 — Test Report
Issued by the manufacturer based on non-specific inspection. The document includes actual test results (chemical composition, tensile strength, hardness), but these results are from a general production lot — not necessarily from the specific heat or batch that was supplied to your order. Traceability is therefore limited. Acceptable for general commercial supply where strict lot traceability is not required.
Type 3.1 — Inspection Certificate
This is the most commonly specified document in industrial, oil & gas, and process plant procurement. A 3.1 certificate is issued by the manufacturer's own authorised inspection representative, who is independent of the production department. The certificate validates test results against the specific heat number or lot number supplied to your order — full traceability is established. The authorised representative countersigns the document on behalf of the manufacturer.
Type 3.2 — Inspection Certificate (Third-Party Validated)
A 3.2 certificate has all the attributes of a 3.1 but goes one step further: it must be countersigned by an independent third party. This third party may be an independent inspection body (such as Bureau Veritas, Lloyd's Register, SGS, or TÜV) or the purchaser's own representative. Both the manufacturer's authorised rep and the independent party must sign the certificate.
The Critical Difference: Who Validates the Document?
| Document Type | Issued By | Countersigned By | Heat/Lot Traceability |
|---|---|---|---|
| 2.1 | Manufacturer | — | None |
| 2.2 | Manufacturer | — | Partial |
| 3.1 | Manufacturer's authorised rep | — | Full (specific heat/lot) |
| 3.2 | Manufacturer's authorised rep | Independent body or purchaser's rep | Full (specific heat/lot) |
When is a 3.2 Certificate Mandatory?
A 3.2 certificate becomes mandatory when:
- The end-client or EPC contractor specifies it in the project material requisition (MR) or technical specification
- NACE MR0175 / ISO 15156 sour service projects — oil and gas environments containing H₂S require elevated scrutiny of material compliance
- ASME Section VIII Division 1 or 2 pressure vessels where the Authorised Inspector (AI) requires third-party validation
- Nuclear applications under ASME Section III or equivalent codes
- Safety-critical piping in offshore topside or subsea systems where operator specifications mandate it
- Any application where the purchaser's representative is physically present at the mill for inspection and countersigning
How to Specify Correctly in Your Purchase Order
The most effective way is to include the requirement explicitly in the material specification or PO line item. Common phrasings:
- "Material Test Reports in accordance with EN 10204 Type 3.1, traceable to heat/lot number."
- "EN 10204 Type 3.2 certificates required, countersigned by [Inspection Agency Name] or Buyer's Representative."
Include this requirement in your Requisition, RFQ, and final Purchase Order. Do not add it retrospectively — once material is manufactured and tested without a 3.2 inspection witness, obtaining a valid 3.2 document retroactively is not possible.
Common Mistakes to Avoid
- Accepting 2.2 when 3.1 was specified: A 2.2 document does not establish heat-specific traceability. Reject it and request the correct document.
- Confusing ASTM compliance statements with EN 10204 documents: An ASTM A276 or A312 certification is a product standard, not an EN 10204 inspection document type.
- Not checking that the heat number on the MTC matches the material markings: The 3.1 certificate is only valid if it refers to the same heat/lot marked on the material.
- Forgetting to name the inspection agency for 3.2: A 3.2 certificate countersigned by an unnamed or uncertified party may not be accepted by the end client's QC team.
What Ragnar Metals & Tubes Provides
We supply EN 10204 3.1 mill test certificates as standard documentation with all stainless steel, duplex, and nickel alloy products. For 3.2 requirements, we coordinate with approved third-party inspection agencies to arrange witness inspection and countersignature at the mill or our warehouse. Specify your requirement at the time of enquiry and we will confirm the documentation scope in our quotation.