What Is the Difference Between API Level 1 & 2

When evaluating in-line inspection (ILI) tools, you will often hear references to API Level 1 vs. Level 2 validation.

But what do these levels actually mean?

𝗦𝗵𝗼𝗿𝘁 𝗮𝗻𝘀𝘄𝗲𝗿:

They describe how ILI results are validated and how much confidence operators can place in them.

• Level 1 = comparison to prior validated ILI results
• Level 2 = validation against independent reference data

𝗟𝗼𝗻𝗴𝗲𝗿 𝗮𝗻𝘀𝘄𝗲𝗿:

Under API 1163, validation is the process of confirming that ILI results are accurate and suitable for integrity decisions – after a specification has been derived through internal testing (see the left chart based on testing for the Ultrasonic Crack Detection (UT-CD) Hawk).

𝘓𝘦𝘷𝘦𝘭 1 𝘷𝘢𝘭𝘪𝘥𝘢𝘵𝘪𝘰𝘯 𝘪𝘴 𝘵𝘩𝘦 𝘮𝘰𝘴𝘵 𝘴𝘵𝘳𝘢𝘪𝘨𝘩𝘵𝘧𝘰𝘳𝘸𝘢𝘳𝘥 𝘢𝘱𝘱𝘳𝘰𝘢𝘤𝘩.

It involves comparing current ILI results to previously validated ILI data from the same pipeline. If the results fall within defined tolerances and no significant anomalies are identified, the inspection can be considered validated at Level 1.

Consider an example.

Dexon’s engineers claim that the UT-CD Hawk can size cracks to ±1.00 mm at 80% confidence.

An inspection is completed with no significant anomalies requiring verification digs. By comparing historical ILI records of known flaws, inspectors confirm that the Hawk operates within its stated specifications and achieves API Level 1.

However, this validation is inherently limited because it relies on hisotrical data.

𝘓𝘦𝘷𝘦𝘭 2 𝘷𝘢𝘭𝘪𝘥𝘢𝘵𝘪𝘰𝘯 𝘨𝘰𝘦𝘴 𝘧𝘶𝘳𝘵𝘩𝘦𝘳.

It requires comparison against independent reference data, typically obtained through verification digs, where anomalies are physically measured and compared to ILI results.

Continuing the example above:

A second inspection identifies 5 significant anomalies. The operator excavates and measures them in the field. The results confirm that crack sizing falls within ±1.00 mm, consistent with the stated performance, and achieves API Level 2.

A sample unity plot is included below of Dexon’s actual UT-CD Hawk’s performance based on 52 verified field defects.

Because this validation is based on direct measurement of real defects, it provides a more objective and reliable assessment of tool performance.

𝗪𝗵𝘆 𝘁𝗵𝗶𝘀 𝗺𝗮𝘁𝘁𝗲𝗿𝘀

ILI tools often perform well under controlled or repeatable conditions. The real challenge is demonstrating that performance in the field.

• Level 1 = efficient, but indirect and dependent on historical data    
• Level 2 = independent, field-based verification with higher confidence

For critical integrity decisions, understanding this progression is essential when selecting and trusting inspection technologies.