When qualifying welders or welding procedures you must remember that the applicable construction code may modify the requirements of Section IX. For example, welders test coupons can be evaluated by bend tests or radiography per Section IX, however, if the welding is per B31.3, high pressure, radiography isn't permitted. The qualification is by guided bend tests only.
Some projects require the welders to be qualified by testing on the job site by a third party. It is pricey, but it mitigates the opportunity for the erector to falsify welder qualification test records.
In the event there is doubt of the welder's ability to deposit sound welds, the inspector representing the owner usually has the authority to require the welder to be retested.
Best regards - Al