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Question

What ultrasonic testing (UT) methods would be considered an acceptable alternative to ASME Section V, Article 5 as referenced in ASME Section III NB-2542.1?

This question often arises as advanced ultrasonic techniques—particularly Phased Array Ultrasonic Testing (PAUT)—become more common in manufacturing and inspection environments.

Answer

ASME Section III NB-2542.1 requires ultrasonic examination of forgings and bars to be performed in accordance with ASME Section V, Article 5. Article 5 establishes the traditional straight-beam and angle-beam ultrasonic examination techniques used for volumetric inspection of these product forms. The examination methods typically reference SA-388/SA388M, which includes techniques such as calibration using reference reflectors and evaluation methods like Distance Gain Size (DGS).

However, Section III does allow for alternative ultrasonic examination methods. Under NB-2542.2, an alternative method may be used if it can be demonstrated to provide examination capability equivalent to that required by Article 5.

This is where confusion often occurs. Simply writing a procedure to ASME Section V, Article 4, including Mandatory Appendix IV for PAUT, does not automatically establish equivalency to an Article 5 examination. Article 4 provides the general requirements for ultrasonic examination methods and includes provisions for phased array techniques, but it does not inherently replicate the specific examination and evaluation basis required by Article 5.

To use an alternative ultrasonic technique in lieu of an Article 5 examination, the procedure qualification or technical justification must demonstrate that the method provides equivalent detection capability and evaluation criteria. In other words, the alternative method must be capable of detecting and characterizing discontinuities at least as effectively as the examination method required by Article 5.

Demonstrating equivalency typically involves evaluating several technical elements, including:

• Calibration and reference reflector response comparable to Article 5 requirements
• Sensitivity levels and amplitude response, including alignment with DAC or DGS reference levels used in Article 5 examinations
• Back-wall detection capability at comparable sensitivity settings
• Scanning coverage and beam angles that provide inspection coverage equivalent to the required straight-beam or angle-beam examinations
• Spatial resolution and reflector characterization, particularly for planar discontinuities
• Amplitude threshold comparisons, often demonstrated through sensitivity equivalence such as a 5% full-screen-height (FSH) basis

For certain geometries, such as ring forgings, the evaluation may also need to demonstrate the ability to apply techniques such as the circle rule, where applicable to the Article 5 examination.

In practice, demonstrating equivalency may involve comparing the response of the alternative technique, such as PAUT, to known calibration notches or reflectors used in Article 5 examinations. The objective is to confirm that the alternative method provides equivalent or improved capability to detect and evaluate discontinuities relevant to the NB-2542.2 acceptance criteria.