9.1. NDE Methods

9.1.1. What are the commonly used methods of non-destructive examination (NDE)?

The most commonly used NDE method in structural steel fabrication is visual (VT). Other examination methods are also used: dye penetrant (DT), magnetic particle (MT), radiographic (RT), and ultrasonic (UT). The method to be used is established after consideration of the importance of the weld as well as the defect identification capability and relative cost of each method. When NDE is required, the process, extent, techniques and standards of acceptance must be clearly defined in the contract documents.

last modified 18 September 2002

9.1.2. What non-destructive examination (NDE) inspection beyond visual should be specified? What acceptance criteria should apply?

The Structural Engineer of Record [SER] should identify members and connections that must be inspected and specify how they should be inspected. Inspection requirements can be specified, if desired, by the SER as some percentage, with subsequent testing requirements identified if a significant defect rate is discovered. For example, 15 percent initial inspection might be deemed acceptable for an AISC Quality Certified fabricator, with no further testing required if all inspected joints are found to be compliant; if a significant defect rate were found, the inspection of an additional 15 percent might be required.

last modified 18 September 2002

9.1.3. What level of quality assurance is implied by each non-destructive examination [NDE] method?

When specified by the Structural Engineer of Record [SER], visual [VT], magnetic particle [MT] and dye penetrant [DT] inspection imply that internal soundness adequate for the service conditions will be provided by adherence to the requirements of AWS D1.1. Rework required to correct profile, size, undercut or overlap, and/or excessive pin holes or cracks is considered to be part of the contract requirements. However, because these are essentially surface or near-surface inspection methods that do not describe the internal condition, rework required by the owner to correct internal discontinuities, if found by other means, is considered to be a change in contract requirements.

When specified by the SER, radiographic [RT] and ultrasonic [UT] inspection imply that the total internal soundness of the weld is important to the structural integrity and must meet the established standard of acceptance. Any rework required to meet this standard of acceptance is considered to be part of the contract requirement. It should be understood that there are practical limitations to the effectiveness of RT and UT, such as geometry and thickness of the joined pieces.

last modified 18 September 2002

9.1.4. non-destructive inspection is specified for base metal, what acceptance criteria are appropriate?

Occasionally, severe service conditions may necessitate non-destructive examination [NDE] to verify a high degree of soundness of the parent material. While ultrasonic [UT] techniques are suitable for such investigation, standard acceptance criteria do not exist. From the 2005 AISC Specification Section M5.3, both a clear set of acceptance criteria and a definition of the areas to be tested should be specified in the contract. The acceptance criteria in ASTM A435/A435M Straight Beam UT Exam for plates or ASTM A898/A898M Straight Beam UT Exam for shapes may be appropriate.

last modified 1 January 2006

9.1.5. How are parent-metal discontinuities that prohibit ultrasonic [UT] examination of the weld zone handled?

Parent metal sometimes contains discontinuities that are within the acceptance criteria, but prevent a full examination of a weld under UT inspection. In such cases, the alternate scanning procedures of AWS D1.1:2004 Section should be used. When such procedures still do not allow full examination of the weld, the condition should be reported to the Structural Engineer of Record [SER] for resolution. last modified 1 January 2006