The main difference is that the welder qualified to ASME has to follow a WPS that is qualified by testing, i.e., it is supported by one or more PQRs, or the employer can also elect to purchase SWPSs from AWS. In general, the employer must qualify the welder when qualifying to the requirements of ASME Section IX.

When qualifying to AWS D1.1, the welder can use a prequalified WPS, a WPS supported by one or more PQRs, or a SWPS purchased from AWS. The employer can delegate the responsibility for qualification to a third party, qualify the welder in-house, or accept qualification performed by a previous employer.

The acceptance criteria for AWS D1.1 are more stringent than ASME Section IX with regards to the visual examination of the completed test coupon and the test results of the guided bend test. When qualifying the welder per Section IX there is no criteria provided for typical surface breaking discontinuities such as undercut, porosity, face reinforcement, or other surface conditions relating to weld profile. As such, undercut, overlap, underfilled craters, etc. are not attributes that can serve as a basis for rejecting the test coupon per ASME Section IX.

As silly as it all seems, a welder qualified to AWS D1.1 is not qualified to weld pressure boundary joints per ASME Section IX unless the individual testing the welder is savvy enough to know his way around both AWS D1.1 and ASME Section IX to cover all the appropriate requirements and completes the performance test record to indicate the welder has met the requirements of both AWS D1.1 and ASME Section IX.

Best regards - Al