Standards guide · Inspection documents
Inspection documents to EN 10204 explained
Anyone buying pipes, flanges or fittings for pressure applications is always buying two things: the component and the proof of what is in it. This page explains the inspection documents to EN 10204 – types 2.1, 2.2, 3.1 and 3.2, the old designation "3.1B", the plausibility check at goods receipt and the most important inspection bodies.
- Standard
- EN 10204
- Certificate types
- 2.1 / 2.2 / 3.1 / 3.2
- Standard in plant engineering
- 3.1
- Old designation
- 3.1B (until 2004)
Why a piece of paper matters so much
The proof of what is inside a component is the inspection document to EN 10204 – colloquially often called a "mill certificate". Internationally you will meet the umbrella terms Mill Test Certificate (MTC) and Mill Test Report (MTR). Caution: these English terms do not guarantee any particular certificate type – whether a document really corresponds to an inspection certificate 3.1 or 3.2 to EN 10204 is shown only by the standard and certificate type stated on the document. The certificate documents, among other things, the chemical composition and the mechanical properties of the delivered material and thus links component, material standard and purchase order.
Without this document a component is simply unusable for many applications: operators, inspection organisations and codes require complete traceability from the installed part back to the melt.
The four certificate types at a glance
EN 10204 defines four types of document. The core difference: who confirms what – and how independent of production are they?
| Type | Name | Test results | Validated by |
|---|---|---|---|
| 2.1 | Declaration of compliance 2.1 | none | manufacturer (no test data) |
| 2.2 | Test report 2.2 | yes, but from non-specific inspection | manufacturer |
| 3.1 | Inspection certificate 3.1 | yes, for the defined inspection unit (usually heat/batch, product-dependent) | manufacturer's inspection department, independent of production |
| 3.2 | Inspection certificate 3.2 | yes, for the defined inspection unit (usually heat/batch) | manufacturer's inspection plus independent external inspection representative |
Type 2.1 is a pure declaration of compliance: the manufacturer confirms that the delivery conforms to the order – without a single measured value. For pressure-bearing parts this is generally not sufficient.
Type 2.2 contains test results, but from non-specific inspection – not necessarily from the exact batch delivered, e.g. from ongoing production monitoring of comparable products.
Type 3.1 is the de-facto standard in plant and piping engineering: the results come from specific inspection and relate to the inspection unit of the delivery defined in the product standard – usually a heat or batch. They are validated by the manufacturer's inspection representative, who is organisationally independent of the production department – but still part of the manufacturer's organisation.
Type 3.2 adds one more level: in addition to the manufacturer's inspection, the purchaser's inspection representative or an inspection body named in official regulations (frequently a classification or inspection society) validates the tests. A 3.2 certificate therefore carries two validations. Important: the external inspector usually does not test himself, but witnesses and verifies the mill laboratory's tests – procedures, calibration, sample allocation.
Which certificate is required when?
- 2.1/2.2: non-critical applications, general steel construction, trading goods without pressure relevance.
- 3.1: the normal case for pressure-bearing components in plant engineering, process industry, power engineering and oil & gas. The fitting standards (e.g. EN 10253-2) also typically call for 2.2 or 3.1/3.2 as documentation.
- 3.2: particularly critical applications where the order or the code requires independent witnessing – highly hazardous media, subsea and nuclear applications, or projects with contractually required third-party inspection. A 3.2 certificate is more expensive and extends delivery time.
In the European pressure-equipment context (PED 2014/68/EU and the AD 2000 code): for the main pressure-bearing parts of pressure equipment in categories II, III and IV, the directive requires a certificate based on specific inspection of the products. Which document type is specifically required follows from product standard, harmonised standard and specification – in practice this usually means an inspection certificate 3.1 for main pressure-bearing parts.
Decisive for purchasers: the certificate type belongs in the purchase order. A 3.1 certificate cannot be "upgraded" afterwards, and requesting one years later is far more effort than one line in the order text.
"3.1B" – the old designation
Old orders, specifications and certificates still show the designation 3.1B. This is the old designation from EN 10204:1991; since the 2004 edition this certificate type is simply called 3.1. Anyone ordering "3.1B" today therefore means a current 3.1 certificate. The former standard also had 3.1A and 3.1C (inspection by an official third party or by the purchaser's representative) and its own old 3.2; all three are absorbed in today's 3.2.
What does a 3.1 certificate contain?
- Header with manufacturer, certificate type, date, certificate number
- Purchaser, order reference, item reference
- Product description: standard, material, dimension, manufacturing process (seamless/welded), delivery condition/heat treatment
- Quantities and weights
- Heat number (batch number) – the key to traceability
- Chemical composition (cast analysis, plus product analysis where the standard requires it) against the standard limits
- Mechanical properties: tensile strength, yield strength, elongation, plus hardness and impact energy where required
- Results of additional tests (e.g. pressure test, NDT, corrosion tests)
- Validation of the inspection department; for 3.2 additionally the stamp and validation of the external inspection representative
For further-processed products – such as fittings made from pipe – the documentation includes the reference to the starting material in addition to the proof for the finished product.
Checking a certificate: six-step plausibility check
- Match material and standard exactly against the order – beware of silently "equivalent" grades.
- Check the heat number on the certificate against the stamping on the component. If the number does not match, the certificate is worthless for this part.
- Spot-check chemistry and mechanical values against the limits of the material standard.
- Check delivery condition/heat treatment against the standard requirement.
- Check certificate type and validations: does the paper say 3.1 if 3.1 was ordered? For 3.2, are both validations present?
- Completeness: missing impact values, missing heat treatment condition or missing additional tests are a non-conformity – in case of doubt, block the material and clarify.
Recognising forged certificates
- Inconsistencies in the document: deviating fonts, blurred logos, arithmetically implausible values (e.g. chemistry and mechanical values that do not fit together), values exactly on the standard limit across many positions.
- Broken traceability: heat number on the part and on the certificate do not match, or the chain from starting material to finished product is not closed.
- Verification with the mill: in case of doubt contact the issuing mill directly – using contact details you research yourself, not those given in the suspicious document.
- PMI at goods receipt: spark spectrometry or XRF (OES/XRF) reveals material mix-ups invisible on paper. Note: handheld XRF devices do not measure carbon – for carbon-dependent distinctions (e.g. L grades or low-alloy steels) an OES or suitable LIBS method is required.
- Supplier qualification: buying through qualified, audited suppliers with a documented supply chain is the most effective prevention.
Inspection bodies at a glance
Independent organisations act for 3.2 inspections and project-specific third-party surveillance. The most relevant from our perspective:
| Organisation | Short profile |
|---|---|
| TÜV organisations / notified bodies | The classic inspectors in the German and European pressure-equipment context – as notified bodies under the Pressure Equipment Directive and as independent inspection representatives for 3.2 certificates. |
| Lloyd's Register (LR) | Long-established British classification and inspection society; as established in shipbuilding as in industrial and energy engineering. |
| DNV | Classification and certification society with Scandinavian roots; particularly present in maritime, offshore and energy projects. |
| RINA | Italian classification and inspection society – relevant above all in export business and projects with an Italian code or customer background. |
| ABS (American Bureau of Shipping) | US classification society, in demand for projects in the US-influenced offshore and marine environment. |
Other inspection organisations also act as third-party inspectors (e.g. Bureau Veritas, SGS).
From a stockholder's perspective: what matters in practice
- Always order the certificate with the goods. The certificate type (usually 3.1) belongs in the order text – a specific certificate cannot simply be procured later.
- Keep certificate and part together. The heat or batch number is the central bridge between certificate and component; order, item or piece markings may be required in addition. We recommend filing certificates by order and heat number.
- Processing at the stockholder: if a part is cut or machined in trade, the marking must be transferred before cutting so traceability is not broken. Zickwolff offers TÜV-Süd-certified re-stamping in accordance with the Pressure Equipment Directive.
- Certificates from our database: for goods demonstrably purchased from us, we retrieve inspection certificates via order and heat number and provide them again – by e-mail or on a USB drive.
Frequently asked questions
What is the difference between a 2.2 test report and a 3.1 inspection certificate?
A test report 2.2 contains test results from non-specific inspection – not necessarily from the exact batch delivered. In an inspection certificate 3.1 the values come from specific inspection and relate to the inspection unit of the delivery defined by the product standard – usually a heat or batch; they are validated by the manufacturer's inspection department that is independent of production. For pressure-bearing components in plant engineering, 3.1 is the de-facto standard.
What does 3.1B mean?
3.1B is the old designation from EN 10204:1991. Since the 2004 edition this certificate type is simply called 3.1 – so anyone ordering "3.1B" today means a current 3.1 inspection certificate.
When do I need a 3.2 instead of a 3.1 certificate?
When the applicable code, the customer or the project requires independent witnessing of the tests – for example with highly hazardous media, subsea or nuclear applications, or contractually required third-party inspection. A 3.2 certificate costs more and extends the delivery time, because the external inspector has to be scheduled.
Is an inspection certificate the same as an MTC/MTR?
Usually, but not automatically: MTC (mill test certificate) and MTR (mill test report) are international umbrella terms for material test documents. Whether a document actually corresponds to a certificate type to EN 10204 (e.g. 3.1 or 3.2) can only be verified from the standard and certificate type stated on the document itself.
Who validates a 3.2 certificate?
For 3.2, both the manufacturer's authorised inspection representative and the purchaser's inspection representative – or an inspection body named in official regulations, such as TÜV, Lloyd's Register, DNV, RINA or ABS – validate the document. The form of validation (signature, stamp, electronic release) may vary.
Can I request a certificate retrospectively?
From the original supplier via the order or heat number, yes – for goods demonstrably purchased from Zickwolff we retrieve inspection certificates from our database and provide them again, by e-mail or on a USB drive.
How do I recognise a forged certificate?
By a plausibility check of the document (typography, arithmetically implausible values or values exactly on the standard limit across many positions), by comparing the heat number on the certificate with the stamping on the component, and in case of doubt by verifying directly with the issuing mill – using contact details you research yourself. A PMI check (OES/XRF) at goods receipt additionally reveals material mix-ups that remain invisible on paper.
Is a 2.1 declaration sufficient for pressure equipment?
For the main pressure-bearing parts of pressure equipment in PED categories II to IV, a plain 2.1 declaration of compliance is not sufficient – a certificate based on specific inspection is required there. For other components and categories, the product standard and the specific conformity assessment govern; type 2.1 remains a declaration without any measured values.
Request an inspection certificate
You need an EN 10204 certificate for goods purchased from Zickwolff – or want the 3.1 certificate supplied with your next order? We are happy to help, in English.
Send us your inquiryTechnical basis: EN 10204, PED 2014/68/EU, AD 2000 code and the product standards referenced in the text. All information without guarantee – the current standard texts always prevail. Editorially reviewed: July 2026.