EN 10204 3.1 vs 3.2

Quick Answer

EN 10204 Type 3.1 is a mill test certificate (MTC) issued by the manufacturer’s authorized inspection representative, confirming that products meet order requirements. Type 3.2 adds a mandatory validation by an independent inspection body or the purchaser’s designated representative. Both certificates are based on specific inspection of the delivered products, not general quality data.

EN 10204 defines four types of inspection documents for metallic products. In the oil and gas industry, Types 3.1 and 3.2 are by far the most commonly specified for piping materials, flanges, fittings, and valves. The key distinction lies in who validates the test results.

Certificate Types Compared

Feature	Type 3.1	Type 3.2
Document name	Inspection certificate 3.1	Inspection certificate 3.2
Issued by	Manufacturer’s authorized inspector	Manufacturer’s authorized inspector
Validated by	Manufacturer only	Manufacturer + independent inspection body
Third-party witness	Not required	Required (independent body or purchaser’s rep)
Test data	Specific to delivered product (heat/lot)	Specific to delivered product (heat/lot)
Traceability	Heat number, lot, order reference	Heat number, lot, order reference
Cost	Standard	Higher (third-party inspection fees)
Lead time impact	None	May add 1-3 days for TPI scheduling
Typical application	Standard piping, utility services	Critical services, sour service (NACE), high-pressure

What Each Certificate Contains

Both Type 3.1 and 3.2 certificates include the same technical content:

• Chemical composition (heat analysis and, if required, product analysis)
• Mechanical properties (tensile strength, yield strength, elongation, hardness)
• Non-destructive examination results (UT, hydrostatic test, visual)
• Dimensional verification
• Heat number traceability
• Reference to material standard (e.g., ASTM A106 Gr. B, ASTM A182 F316)

The difference is solely in the validation process. A 3.2 certificate must bear the stamp or signature of the authorized independent inspection representative who witnessed the tests or verified the results at the manufacturer’s facility.

When to Specify Each Type

Type 3.1 is sufficient for:

• Standard process piping in non-critical services
• Utility piping (water, air, nitrogen)
• Structural steel and general-purpose flanges and fittings
• Projects where the mill test certificate from the manufacturer provides adequate assurance

Type 3.2 is required when:

• Client specifications mandate third-party inspection (TPI) at the mill
• Sour service applications per NACE MR0175/ISO 15156
• High-pressure or high-temperature critical piping (Class 600 and above)
• PED (Pressure Equipment Directive) Category III and IV equipment
• National regulations or classification societies (DNV, Lloyd’s, Bureau Veritas) require it

Common Mistake

Specifying Type 3.2 for all materials on a project regardless of criticality. This significantly increases procurement cost and lead time without adding value for non-critical items. Use a risk-based approach: specify 3.2 for critical and sour service piping, and 3.1 for standard utility and low-pressure services.

EN 10204 Types 2.1 and 2.2 (declaration of compliance and test report based on non-specific inspection) are rarely accepted in oil and gas projects and should not be confused with 3.1 and 3.2 inspection certificates.

Read the full guide to piping engineering