The certificate you didn’t specify is the one you’ll get.
EN 10204 3.1 and 3.2 look one digit apart. They are not the same document, they do not cost the same, and they do not carry the same liability. If your purchase order is silent about which one you need, your supplier has already decided — and the cheaper answer is 3.1.
A pressure vessel, as the first article in this series put it, is delivered twice — once in steel, once on paper. The paper half has its own version of the same problem: some of it is signed once, some of it is signed twice, and the difference decides whether a Notified Body accepts the dossier or sends it back.
The purchase order said “3.1 certificates for all pressure parts.” The plates arrived with 3.1 certification, correctly filled out, correctly issued. Nothing was wrong with the paperwork — except that the vessel was Category III, and the design file called for 3.2 on the shell plates. The gap surfaced during final assessment, with the plates already welded into a closed vessel. Re-certifying material after it has been formed and welded into a pressure part is not a paperwork fix. In this case, it wasn’t possible at all.
The difference is not the paper. It’s who signs it.
EN 10204 defines four types of inspection documents: 2.1, 2.2, 3.1 and 3.2. The 3.1 and 3.2 are the two that generate disputes, because both are “specific inspection” documents — both certify test results tied to the actual material delivered, not a generic statement of conformity. The only difference between them is who validates those results.
3.1 — one signatureValidated by the manufacturer’s own inspection department, independent of production. Certifies the actual test results on the actual parts supplied.
3.2 — two signaturesValidated jointly by the manufacturer’s representative and a second, independent party — the purchaser’s own inspector, or one designated by the applicable regulation.
That second signature is the entire cost difference. A 3.1 certificate is validated internally, by a department independent of production but still inside the manufacturer’s organization. A 3.2 certificate needs someone outside that organization — the buyer’s own inspector, or an inspector designated by the applicable regulation — to review and countersign the same results. Scheduling that person, and building their sign-off into the production timeline, is why 3.2 costs more and takes longer. It is not a heavier stamp. It is a second person who has to be in the loop before the material can be released.
EN 10204 doesn’t decide this for you
The standard defines the four certificate types. It does not say which one a given part needs — that decision sits in the applicable product standard, the design code, the PED conformity assessment module, or the purchase contract that references EN 10204. Read on its own, EN 10204 is neutral. Read against a silent purchase order, it defaults to whatever the supplier finds easiest to produce, which is almost always 3.1.
Where 3.2 is normally the right call
Situations that typically require the second signature
- Category III and IV pressure equipment, where the conformity assessment module calls for verification of materials by a Notified Body or the purchaser’s inspector
- Design codes or client technical specifications that name 3.2 explicitly for specific parts — commonly pressure-retaining shell and head material
- End-users with a standing internal policy of third-party material verification, independent of category — common in oil & gas, high-hazard chemical processes, and some utility-scale energy projects
- Safety-critical components: primary containment, pressure-relief parts, anything where the buyer wants a certificate that isn’t only the manufacturer vouching for itself
None of this means 3.2 is always the safer choice to specify. Requiring it for every item on a bill of materials adds cost and lead time to parts where nobody — not the code, not the client’s own quality department — actually needs the second signature. The fix isn’t a blanket default in either direction. It’s specifying the certificate type per item, against what the design register and the applicable code actually require.
It is not a heavier stamp. It is a second person who has to be in the loop before the material can be released.
This is the sixth question from the first article, in full
The checklist in “A pressure vessel is delivered twice” asked: 3.1 or 3.2 — and for which items specifically? That’s not a rhetorical question. It belongs on the purchase order, item by item, before material is ordered — inside the Inspection and Test Plan, not decided after the fact by whoever happens to be filling out the mill’s paperwork.
How we handle it
The certificate type is specified per item in the ITP, not once for the whole project — tied to the same weld map and traceability record described in the first article, so a 3.2 requirement on the shell plates doesn’t quietly become a 3.1 substitution on a nozzle reinforcement pad.
Mismatched assumptions get flagged early. When a client’s default expectation doesn’t match what the category or code actually requires, we raise it before the purchase order goes out — not during document review, when the material is already welded in.
Subcontractor orders carry it as a line item. The certificate requirement travels with the order as a specific, checkable obligation, not a general expectation of quality.
Three questions for your next purchase order
- Does the applicable code, category or client specification actually require 3.2 — or is 3.1 sufficient?
- Does the requirement apply to the whole order, or only to specific items?
- If 3.2 applies, who is the second validating party — your own inspector, or one designated by regulation?
Specifying a pressure equipment order?
Send us the bill of materials and the applicable category. You’ll get back which items need 3.1, which need 3.2, and why — before the purchase order goes out.
