MTC Requirements for Piping Materials

MTC requirements for piping materials depend on the applicable product standard (ASTM, API, EN), the piping design code (ASME B31.3, B31.1), and the project specification. A mill test certificate (MTC) must document the chemical composition, mechanical properties, heat treatment condition, and dimensional conformity of each piping component. The EN 10204 standard classifies inspection documents into types that define who performs the testing and who validates the results.

What an MTC Must Include

Every MTC for piping materials should contain the following mandatory data fields to satisfy code and project requirements:

• Manufacturer name and address
• Product description (pipe, fitting, flange, etc.)
• Material specification and grade (e.g., ASTM A106 Gr. B)
• Heat number and lot/batch number
• Dimensions (OD, wall thickness, length)
• Heat treatment condition (normalized, quenched and tempered, etc.)
• Chemical composition (heat and/or product analysis)
• Mechanical test results (tensile, yield, elongation, hardness)
• Non-destructive test results (hydrostatic test, UT, RT as required)
• EN 10204 certificate type and authorized signatory

MTC Requirements by EN 10204 Type

EN 10204 Type	Document Name	Issued By	Testing Basis	Typical Use
2.1	Declaration of compliance	Manufacturer	No specific test results	Low-criticality items
2.2	Test report	Manufacturer	Non-specific testing	Gaskets, bolts (non-critical)
3.1	Inspection certificate 3.1	Manufacturer’s authorized inspector	Specific testing on delivered product	Standard piping (pipes, fittings, flanges)
3.2	Inspection certificate 3.2	Manufacturer + third-party inspector	Specific testing on delivered product	Critical/sour service, high-pressure piping

Code-Specific MTC Requirements

ASME B31.3 (Process Piping): Requires MTCs for all pressure-containing components. Fluid service category determines the certificate type: Normal fluid service typically requires Type 3.1; Category M (lethal) and High-Pressure service may require Type 3.2 with third-party witness.

ASME B31.1 (Power Piping): Mandates material certification for all piping components operating above specified pressure and temperature thresholds. Supplementary requirements (e.g., impact testing) must appear on the MTC when specified.

Client/project specifications: Oil and gas operators often impose requirements beyond the code minimum, such as NACE MR0175 compliance for sour service, maximum hardness limits (typically 22 HRC for carbon steel), and PMI verification for alloy materials.

Common Mistake

Accepting an MTC without verifying that the reported chemical composition and mechanical properties fall within the limits of the specified ASTM or EN standard. Always cross-check actual values against the standard’s mandatory ranges, not just confirm that a certificate exists. Out-of-range values on an otherwise official-looking MTC are a red flag for pipe inspection teams.

Proper review of MTCs is a fundamental quality control step in any piping project. Incomplete or non-compliant certificates must be flagged before materials are released for fabrication.

Read the full guide to mill test certificates