A box of stainless fittings arrives with a neat PDF headed “Inspection Certificate EN 10204 3.1”. The grade is right, the chemistry is inside the limits, and there is a stamp. Then the site inspector asks a simple question: which of these numbers is on the fittings? Nobody can point to one.
In piping, the certificate is worth only what it can be tied to. Material passes from a mill to a forging or fitting maker, often to a stockist, sometimes to a trader, and then to you; each step is a point where the paper and the steel can part company. This article sets out what to require on the order, how to read a mill test certificate for pipe, fittings and valves, how certificates travel through intermediaries, and the checks that catch one that does not belong to your goods.
The general difference between the EN 10204 document types, and when to ask for each on any metal part, is covered in quality documents from a Vietnamese supplier. Here we deal with what a piping buyer does with the certificate once it arrives.
💬 Received a certificate you are not sure about? Send it to us with the order line and we will check whether it can be tied to your goods.
What EN 10204 does and does not do
EN 10204 names the type of inspection document the purchaser asked for; it does not define which test results the document must contain — the product specification does.
EN 10204:2004 (Metallic products — Types of inspection documents) specifies the different types of inspection documents supplied to the purchaser in accordance with the requirements of the order. It applies to metallic products whatever their production method and is used together with the product specification that sets the technical delivery conditions. It replaced the 1991 edition, reduced the number of document types and added definitions for “manufacturer”, “intermediary” and “product specification”.
That last point matters. “EN 10204 3.1” on a fitting tells you who validated the document and that the results are from specific inspection; it does not tell you which tests were done. The tests come from the product specification — for example, ASTM A961 sets common requirements for steel flanges, forged fittings, valves and parts for piping applications, and the individual grade specifications such as ASTM A105, A182, A234 and A403 add their own. If your order says only “certificate 3.1”, you have asked for a form, not for content.
| Document type | Validated by | Results relate to | Use in piping |
|---|---|---|---|
| 2.1 | Manufacturer | No results | Rarely enough for pressure parts |
| 2.2 | Manufacturer | Non-specific inspection | Low-risk utility items, if your spec allows |
| 3.1 | Manufacturer’s inspection representative, independent of manufacturing | Specific inspection of the delivered product | The usual requirement for pressure-retaining parts |
| 3.2 | As 3.1, plus the purchaser’s inspector or an inspector designated by regulation | Specific inspection | When the end user or a regulation requires a third party |
What to write on the order
Name the document type, the product specification whose tests it must report, the traceability you need, and the language and format, on the purchase order itself.
| Order line | Example wording | Why |
|---|---|---|
| Document type | ”Inspection certificate 3.1 to EN 10204:2004” | Fixes who validates it |
| Content | ”Reporting all tests required by [product specification and grade]“ | Fixes what is tested |
| Supplementary tests | ”Including [impact test / intergranular corrosion test / PMI] where specified” | These are optional unless ordered |
| Traceability | ”Heat number marked on each piece and shown on the certificate” | Links paper to part |
| Intermediary | ”Original manufacturer’s certificate to be supplied; stockist’s own certificate not accepted in its place” | Prevents re-typed documents |
| Format | ”PDF from the issuer, in English” | Usable by your inspector |
For valves, ask for certificates for the pressure-retaining parts (body and bonnet) and a pressure test record per valve. How valve test records work is in sourcing industrial valves.
Reading a certificate field by field
Read a certificate in the order an inspector does — issuer, product, identification, results, statement — and stop at the first field that does not match your order.
Issuer. The company that made the product or the material, with an address, and the person who validated the document. For a 3.1 certificate, the validating person is the manufacturer’s authorised inspection representative, independent of the manufacturing department.
Product description. Product form (pipe, forging, fitting, casting), product specification and grade, size and wall or rating. If your order said ASME B16.9 elbows in ASTM A403 WP316L, both should appear.
Identification. Heat (cast) number, and where relevant lot or batch number and piece or serial numbers. This is the field that ties paper to steel.
Results. Chemical analysis, mechanical tests, heat treatment, and any supplementary tests ordered. Results should be stated per heat or per test lot, with the units and the limits from the specification.
Statement and validation. A statement that the product complies with the order, the document type, the date, and the signature or stamp of the validating person.
| Field | What to check | Red flag |
|---|---|---|
| Issuer | Real manufacturer with a traceable address | Only a trading company name; no address |
| Product specification and grade | Matches the order exactly | Generic “SS316” with no specification |
| Heat number | Present, and marked on the goods | Missing, or not found on any piece |
| Chemistry | Each element within the specification’s limits | Values identical across different heats |
| Mechanical results | Present when the specification requires them | Blank, or “OK” in place of values |
| Heat treatment | Stated where the grade requires it | Omitted for a grade that needs it |
| Validation | Name and function of signatory, date | Stamp only; date after the shipment date |
Dual-certified grades (for example a stainless grade certified to two grades at once) are common and legitimate when the chemistry and properties satisfy both. Check each value against both grades’ limits rather than assuming.
How certificates travel through stockists and traders
When material passes through an intermediary, the original manufacturer’s certificate should travel with it unchanged, and the intermediary should be able to show how its stock links to that certificate.
EN 10204 includes provisions on transmitting inspection documents through an intermediary. In practice, the clean chain is: the mill or manufacturer issues the certificate; the stockist passes on a copy of that certificate, and identifies which of its stock — by heat number — the certificate covers; the trader passes the same documents on. An intermediary may add its own document (for example a cutting record or a dimensional check), but that does not replace the manufacturer’s certificate. Read the standard’s clause on intermediaries before you write it into a contract, and agree the wording with your supplier.
Two cases deserve care:
- Cut lengths and part bars. A stockist cuts a pipe or bar into shorter pieces. Each piece needs the heat number transferred; ask how the stockist does it.
- Processed products. A fitting maker buys pipe or plate and forms fittings. The fitting maker is now the manufacturer of the fitting and issues its own certificate, which should reference the heat number of the starting material and the heat treatment of the fitting.
As a trading company, we pass on the manufacturer’s documents and ask our suppliers to do the same; we do not re-type or re-issue a mill’s certificate.
💬 We source pipe, fittings, flanges and valves across Asia and check that the certificates arriving with them belong to the goods. See pipe fittings, valves and couplings.
Spotting a certificate that does not belong to your goods
Look beyond forgery: a genuine certificate for different material, a re-typed document, or a certificate with no link to the marking is just as unusable.
Signs that a certificate needs a closer look:
- The heat number on the certificate cannot be found on any piece, or the marking has been ground off and re-stamped.
- The certificate is an editable document rather than an issued PDF, or its layout differs from other certificates from the same manufacturer.
- Several heats show exactly the same chemistry to the last decimal.
- The issuer is a stockist or trader, and no manufacturer’s certificate is supplied.
- The certificate date is after the shipment date, or before the stated production date of the product.
- The quantity or size range covered is far wider than the delivery, so the same document could cover anything.
Verification steps, from cheapest to strongest
Verify in order: match marking to certificate, confirm with the issuer, then test the material.
- Match the marking. Read the heat number on a sample of pieces and find it on the certificate. This costs nothing and catches a certificate with no link to the goods before any other check.
- Confirm with the issuer. Contact the manufacturer through contact details you found independently, not those printed on the certificate, and ask whether it issued a certificate with that number for that heat. Not every manufacturer answers, but a confirmation is strong evidence.
- Positive material identification. A handheld analysis confirms the alloy family and key elements on the actual piece. API RP 578 (Material Verification Program for New and Existing Assets, 4th edition, February 2023 in API’s catalogue) describes how owners use PMI to confirm that components match the specified material.
- Laboratory testing. Chemical and mechanical tests at a laboratory accredited to ISO/IEC 17025 for the method concerned. This proves what the sample is, not where it came from.
| Step | What it proves | What it does not prove |
|---|---|---|
| Marking match | The certificate refers to these pieces | That the certificate is genuine |
| Issuer confirmation | The certificate is genuine | That these pieces are from that heat, unless the marking matches |
| PMI | The alloy is what it should be | Mechanical properties, heat treatment, origin |
| Laboratory test | Chemistry and properties of the sample | Traceability to the mill |
Use them together. A certificate confirmed by the issuer, a marking that matches it, and a PMI result consistent with it are hard to fake as a set. Sampling plans for these checks fit inside pre-shipment inspection and AQL.
When 3.2 is the right request
Ask for 3.2 only when your end user, your customer’s specification or a regulation requires a named third party, because it adds an inspector to the manufacturer’s schedule.
A 3.2 certificate is validated by the manufacturer’s inspection representative and also by the purchaser’s authorised inspector or an inspector designated by the official regulations. That means someone must attend testing at the manufacturer. Agree who the inspector is and when they attend before production starts; a 3.2 cannot be produced after the fact. Whether a regulation in the country of use requires 3.2 for your equipment is a question for that country’s current rules and the end user’s inspector — confirm it before you order.
💬 Need documents specified correctly on a mixed order of pipe, fittings and valves from several Asian suppliers? Tell us what the inspector expects.
Frequently asked questions
1. Is a mill test certificate the same as an EN 10204 3.1 certificate?
”Mill test certificate” is a trade name. It is often a 3.1 inspection certificate, but check the document type stated on it.
2. Can a stockist issue its own 3.1 certificate for material it bought?
The stockist is an intermediary, not the manufacturer, for material it only stores and sells. Ask for the manufacturer’s certificate and the stockist’s link from its stock to that certificate.
3. Does “3.1” guarantee the impact or corrosion tests I need?
No. The document type does not decide the tests. Name the product specification and any supplementary tests on the order.
4. What if the heat number is not marked on the pieces?
Without a marking, the certificate cannot be tied to the goods. Agree marking in the order, and for small fittings ask how the maker marks them.
5. Can a laboratory test replace a missing certificate?
It shows what the sample is, but not where it came from. Where traceability is required, it is not a full substitute.
Sources: EN 10204:2004 (Metallic products — Types of inspection documents), scope and contents as listed by CEN national members; ASTM titles for A961, A105, A182, A234 and A403; API 2025 Publications Catalog (RP 578); ISO/IEC 17025. Checked on 27 October 2026.