Third Party Inspection Certificate

A third party inspection certificate is an inspection document issued or co-signed by an independent inspection body that verifies the material properties, dimensions, and test results of piping components at the point of manufacture. In the EN 10204 framework, this corresponds to a Type 3.2 inspection certificate, where both the manufacturer’s authorized representative and an independent inspector (or the purchaser’s designated representative) validate the test results. Third party inspection (TPI) is a cornerstone of quality assurance in oil and gas piping procurement.

Third Party Inspection Certificate Overview

Aspect	Details
EN 10204 classification	Type 3.2
Issuing parties	Manufacturer + independent third-party inspector
Inspection scope	Chemical analysis, mechanical testing, dimensional checks, NDE, visual
Independence requirement	Inspector must be independent of both buyer and manufacturer
Common TPI agencies	TUV, Bureau Veritas, Lloyd’s, SGS, DNV, Intertek
Typical piping applications	Sour service, high-pressure, lethal service, critical subsea components
Cost vs Type 3.1	10-30% higher due to third-party mobilization and witness fees
Lead time impact	+1 to 3 weeks for inspection scheduling and report issuance
Code reference	ASME B31.3 (Category M, High Pressure); client project specifications
Key deliverables	Inspection certificate 3.2, inspection release note (IRN), punch list

Key Points About Third Party Inspection

When TPI is required: Third party inspection is mandated for piping components in critical services: sour (H2S) environments per NACE MR0175/ISO 15156, lethal fluid service (Category M per ASME B31.3), high-pressure applications, and subsea or offshore installations. Many oil and gas operators require TPI for all pressure-containing components regardless of service classification.

Inspection activities: The third-party inspector witnesses key manufacturing stages, including heat treatment verification, chemical analysis review, mechanical testing (tensile, impact, hardness), dimensional inspection, non-destructive testing (UT, RT, MT, PT), hydrostatic testing, and final visual inspection. The inspector signs off on each activity on an Inspection and Test Plan (ITP).

Difference from Type 3.1: A Type 3.1 certificate is issued solely by the manufacturer’s authorized inspection representative. The test data is identical in scope, but without independent verification. The added value of Type 3.2 is the assurance that an unbiased party has witnessed and confirmed the reported results.

Inspection release: Materials are not shipped until the third-party inspector issues an Inspection Release Note (IRN) confirming that all ITP hold and witness points have been cleared. This prevents non-conforming materials from reaching the project site.

Common Mistake

Assuming that a third-party inspection certificate guarantees material quality on its own. TPI is a verification tool, not a substitute for proper pipe inspection planning. The Inspection and Test Plan must be reviewed and agreed upon before manufacturing begins, with all hold and witness points clearly defined.

Read the full guide to mill test certificates