When purchasing steel materials, mill certificates (also known as inspection certificates) play a crucial role in ensuring product quality, traceability, and compliance with international standards. Under EN 10204, there are several types of inspection documents — and the most commonly used are Type 3.1 and Type 3.2 certificates.
This article explains what they are, their key differences, and why they matter in the steel and engineering industry.
EN 10204 is a European standard that defines the different types of inspection documents supplied with metallic products such as steel plates, bars, and pipes.
It specifies the level of inspection, testing, and certification authority involved before a product is delivered to the customer.
A Type 3.1 certificate (formerly known as “3.1B”) is issued by the manufacturer’s authorized inspection representative, usually the mill’s quality control department.
It confirms that the material supplied meets the order specification and includes the results of specific tests and inspections carried out on the product.
✅ Key points for Type 3.1:
Issued by the manufacturer (mill).
Confirms compliance with order requirements.
Includes test results such as chemical composition, mechanical properties, and heat number.
No involvement from an independent third party.
Example: When you buy a steel plate from a certified mill, the 3.1 cert confirms that all tests were done according to standard, but only the mill verified them internally.
A Type 3.2 certificate provides a higher level of assurance. It includes all information from a 3.1 certificate, plus validation by an independent inspection authority or the buyer’s official representative.
This means both the manufacturer and a third-party inspector (such as Lloyd’s Register, Bureau Veritas, DNV, or TUV) sign off on the test results before delivery.
✅ Key points for Type 3.2:
Issued by the manufacturer and independent inspector.
Offers double verification of test results.
Typically required for critical applications such as shipbuilding, offshore structures, pressure vessels, or oil & gas projects.
Example: For ABS EH36 shipbuilding plates, customers often request EN10204 Type 3.2 certificates, verified by a classification society like DNV or BV.
| Feature | Type 3.1 | Type 3.2 |
|---|---|---|
| Issued by | Manufacturer’s authorized representative | Manufacturer + independent inspector or buyer’s representative |
| Verification | Internal (mill’s own QA) | External (third-party or client verification) |
| Level of Assurance | Standard | High / Critical |
| Cost | Lower | Higher (includes inspection cost) |
| Common Usage | General engineering, construction | Shipbuilding, pressure vessels, oil & gas, offshore projects |
The choice between 3.1 and 3.2 depends on your project requirements and risk level:
3.1 is sufficient for general use where internal quality control is trusted.
3.2 is essential where safety, compliance, or customer specifications require independent validation.
Using the correct certificate ensures traceability, compliance, and customer confidence, protecting your project from costly rejections or failures.
EN 10204 Type 3.1: Verified by the manufacturer.
EN 10204 Type 3.2: Verified by the manufacturer and an independent body.
Both ensure quality, but 3.2 provides the highest assurance for safety-critical applications.
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