8.6.1. What elements are essential for proper workmanship in welding?
Proper selection of the weld type and profile by the designer are essential. In addition, proper filler metal selection and workmanship in joint preparation, fit-up, cleaning, preheat, technique, position, process, and procedure should be properly described in a written WPS. The essential elements of quality are adequately described in AWS D1.1. While each is important when considered individually, they are more important when considered collectively, because deviations from good practice in any one element, when combined with deviations in other elements, can reduce the probability that suitable welds will be attained. All requirements should be consistent with the end use of the member.
8.6.2. Why is adherence to an approved WPS important?
Strict adherence to an approved WPS, when combined with monitoring of the essential elements described in 8.6.1 during the welding operation provides a greater degree of quality assurance than mere cosmetic inspection after welding. The end use of the product (static or dynamic loading, seismic loading, tensile or compressive loading, relative level of stress) should be considered in evaluating any deviations.
8.6.3. What constitutes sufficient evidence of qualification of welding procedures and personnel?
AWS D1.1:2004 Section 4 covers two types of welding procedures, prequalified and qualified; as well as the qualification of welders, welding operators, and tackers. With prequalified procedures, as described in AWS D1.1:2004 Section 3, project-specific qualification by weld procedure testing is not required. However, procedures that deviate from tolerances described therein must be qualified by weld procedure testing as indicated in AWS D1.1:2004 Section 4.1.1. Such testing is time-consuming and costly, and may be repetitious if similar joints have already been tested for previous projects. Likewise, arbitrary re-qualification of personnel, as sometimes specified in contract documents, may unjustifiably increase the cost of welded construction.
As stated in AWS D1.1:2004 Section 4.1.1, properly documented evidence of previous qualification of joint welding procedures should be accepted without re-qualification. Additionally, properly documented evidence of previous qualification of welders, welding operators, and tackers should be accepted without re-qualification, provided that the period of effectiveness has been maintained as described in AWS D1.1:2004, Section 4.1.3.1.