Reading a Mill Test Certificate: EN 10204 Types 2.2, 3.1 and 3.2 for Buyers

A mill test certificate is the only evidence a buyer has that the pipe, flange or bolt in the yard is the material named on the purchase order. Yet most certificates are filed unread, and when one is read it is often the wrong type for the job. This article explains what each EN 10204 inspection document proves and who stands behind it, how to check a certificate against your order in a few minutes, and when the extra cost of third-party witnessing is justified. It is written for procurement engineers and QA staff receiving piping materials for projects in Saudi Arabia.

What EN 10204 is and where it applies

EN 10204 defines the types of inspection documents a manufacturer can supply with metallic products. The standard was first published in 1991 with seven document types adopted from the German DIN 50049 practice; the October 2004 revision reduced these to four, numbered 2.1, 2.2, 3.1 and 3.2, and retired the old 2.3 and 3.1A, 3.1B and 3.1C designations that still appear on old specifications (Wermac). The international equivalent is ISO 10474, Steel and steel products, Inspection documents, whose second edition was published in 2013 (BSI; Australian Steel Institute). The GCC Standardization Organization adopted it as GSO ISO 10474:2013 at the end of December 2013, so a specification in the Kingdom may cite either number for the same document types (GSO).

Two phrases carry the whole standard. Non-specific inspection means the manufacturer tests according to its own procedures on products made by the same process, and the results may not come from the material you receive. Specific inspection means tests are performed on the products actually supplied, or on test units from the same batch, against the requirements of the order and the product standard (HardHat Engineer). Everything else follows from that distinction.

The four document types compared

Sources: Wermac; HardHat Engineer.

A type 2.1 document says nothing about test values and a type 2.2 gives values that may belong to a different heat. Neither traces your product to a specific melt. Type 3.1 is the first document that reports results from the material you have bought, signed by someone inside the mill but outside the production department. Type 3.2 adds a second signature from a party the mill does not control, either the buyer's inspector or a third-party agency acting under regulation or contract, who has witnessed or verified the tests (Wermac; Projectmaterials).

What a 3.1 certificate should contain

A complete certificate for pipe or fittings normally carries the following blocks, and a missing block is a reason to query before accepting the material (Projectmaterials):

• Header: manufacturer, certificate type and number, the purchase order reference, the product standard and grade ordered.
• Product description: product form and process (for pipe, seamless or welded), dimensions, heat treatment condition and quantity.
• Heat number: the identifier that ties the product to a specific melt, which must match the marking on the product.
• Chemical composition: the percentage of each element for the heat, which you compare against the limits of the grade.
• Mechanical properties: tensile and yield strength, elongation and, where the standard or order requires them, hardness and impact values at the specified temperature.
• Additional tests: hydrostatic, ultrasonic or radiographic examination, flattening or flaring for pipe, and any sour service testing ordered.
• Marking and validation: the product marking details and the authorised signatures or stamps.

The requirements vary by product standard: some grades require both heat analysis and product analysis, and impact testing applies only where the grade or the order calls for it. The certificate should show what the standard requires for that grade, not a generic template.

How to check a certificate against your order

A structured check takes a few minutes per certificate and catches most problems (Projectmaterials, adapted):

1. Confirm the specification, grade and any supplementary requirement match the purchase order exactly, including the edition where it matters.
2. Check that the document type matches what the order asked for; a 3.1 does not satisfy a 3.2 requirement.
3. Compare each chemical element with the limits of the grade. Pay attention to carbon equivalent where welding is involved and to elements limited for corrosion reasons in stainless grades.
4. Compare the mechanical values with the minimums and, where they exist, the maximums of the grade. A value that just passes is still a pass, but a pattern of values at the limit deserves attention.
5. Confirm the heat number on the certificate appears on the product marking or on a traceable tag for small items such as bolting.
6. Confirm the heat treatment condition is the one the standard requires for the grade.
7. Confirm the signatures and stamps are present and that any supplementary tests ordered are reported.

Treat an incomplete or mismatched certificate as a non-conformance and place the material on hold until it is resolved. Where a certificate looks doubtful, the reference advice is to verify it directly with the mill using contact details obtained independently, not from the document, and to consider positive material identification on arrival for critical alloy items (Projectmaterials). For bolting, the nut and bolt markings themselves carry the manufacturer symbol, grade and heat or lot traceability, which makes the marking check on receipt straightforward (Projectmaterials, A194).

When to specify 3.1 and when to pay for 3.2

For most industrial piping, process plant and building services work, a 3.1 certificate is the standard requirement and is what reputable mills issue as a matter of course. It gives traceable, batch-specific results and an independent signature within the mill at no extra cost beyond the product price.

A 3.2 certificate adds the cost and lead time of a third-party inspector, and is justified where the consequence of a wrong material is severe or where a regulation or client specification demands it. Typical cases are pressure equipment within a regulatory regime, sour or lethal service, subsea and high-pressure high-temperature duties, and client specifications that call for third-party inspection of main pressure-retaining materials. In Europe, the Pressure Equipment Directive 2014/68/EU applies to stationary pressure equipment with a maximum allowable pressure greater than 0.5 bar and has been in force since 20 July 2016; the directive sets material documentation requirements for pressure-bearing parts, and the exact certificate type required depends on the category of equipment and the conformity assessment route, so refer to the directive and the notified body (European Commission).

Whatever you specify, write the EN 10204 or ISO 10474 type explicitly on the purchase order, together with any supplementary tests, so the mill issues the correct document from the start. A 3.2 cannot be created after the fact for material that has already shipped.

Common problems with certificates in the Gulf supply chain

The problems that reach a receiving yard are rarely forgeries of whole certificates. More often they are a genuine certificate attached to the wrong material, a heat number that cannot be found on the pipe, a stockist's own declaration standing in for the mill document, or a photocopy trimmed so that the product dimensions or quantities no longer appear. Insist on the full mill certificate, with the stockist's traceability record linking it to your delivery if the material has passed through stock, and reject certificates on which the heat number, dimensions or quantity do not match the delivery.

Where dual-certified material is offered, for example austenitic stainless certified to two grades, check that both sets of chemical and mechanical limits are met on the document rather than assuming it. And keep the certificates with the project quality records, indexed by heat number, because the next time anyone asks for them will be during an incident investigation or a handover audit.

Key takeaways

• EN 10204 types 2.1 and 2.2 are manufacturer declarations; 3.1 and 3.2 report specific tests on the delivered batch.
• 3.1 is validated by an inspector inside the mill but independent of production; 3.2 adds an external signature.
• ISO 10474:2013 is the international equivalent and is adopted as a GCC standard.
• Check specification, grade, document type, chemistry, mechanicals, heat number, heat treatment and signatures against the order every time.
• Specify 3.1 for pressure piping and bolting; specify 3.2 only where regulation or the client requires independent witnessing.
• A certificate that does not match the marking on the material proves nothing; put the material on hold.

Frequently asked questions

Is a 3.1 certificate the same as a mill test certificate?

In everyday use the terms overlap. A mill test certificate is the mill's report of test results; EN 10204 defines how that report is classified. Most mill test certificates for piping materials are issued as type 3.1, but a document headed MTC could in principle be a 2.2, so check the type printed on it.

Can a stockist or trader issue a 3.1 certificate?

Only the manufacturer can issue the inspection certificate, because its content comes from tests the manufacturer performed. A stockist can and should supply the original mill certificate together with its own traceability declaration linking the heat to your delivery.

What is positive material identification and when is it needed?

PMI is a non-destructive check of alloy chemistry on the product itself, usually by handheld X-ray fluorescence. It verifies that the material matches the certificate and is commonly specified for alloy and stainless components in critical service, or whenever the certificate or marking is in doubt.

How Al Safsaaf can help

Al Safsaaf Trading & Contracting Company supplies carbon steel pipe and stainless steel pipe and fittings from Riyadh to projects across Saudi Arabia, and can advise on the inspection document type to specify for your order. See our compliance and certificates page for how we handle documentation, or contact us with the material specification you need to meet.