What are the requirements for non-destructive testing (NDT) in AWS D1.1?

The requirement for non-destructive testing (NDT) outlined in AWS D1.1 emphasizes the necessity of defining NDT in project specifications. This means that any requirements for NDT must be clearly stated and agreed upon before the start of a project, ensuring that all stakeholders are aware of the inspection processes to be used. This practice is essential to maintain quality assurance and adherence to safety standards in welded structures.

Defining NDT in project specifications helps in establishing consistency and clarity in the evaluation process of welded joints. It ensures that all relevant parties understand what methods of inspection will be employed, allowing for proper planning and resources to be allocated to meet these requirements. Consequently, this contributes to the integrity and reliability of the welded structures being constructed.

The other options do not align with AWS D1.1's emphasis on structured project specifications. While visual inspection is critical, relying exclusively on it would be insufficient for many projects requiring more rigorous forms of testing. The optional nature of NDT based solely on contractor decisions would lead to variability in quality assurance standards, undermining the integrity of the construction. Lastly, stating that third-party testing is never required overlooks situations where independent assessments are crucial for verifying compliance with code standards and project specifications.