Welding and Rejection Control

You have to select a code from which you can easily find the criteria of acceptance. I recommend ASME B31.3 (Chapter VI. Inspection, Examination, and Testing) in addition to ASME PBVC, Section IX (QUALIFICATION STANDARD FOR WELDING AND BRAZING PROCEDURES, WELDERS, BRAZERS, AND WELDING AND BRAZING OPERATORS).

In addition to ASME B31.3, you may wish to look at AWWA and API for your answers.

Regardless of specification, some discontinuities (defects) like lack of fusion are instant failures. Length, number of occurrences or percentage of weld length will not matter.

Other discontinuities such as lack of penetration, inclusions, and undercut may or may not be rejectable in certain amounts in certain lineal distances of weldment. I have seen very complicated formulae applied to address so much of this and / or that in X distance to determine if the weld was acceptable or not. This as was previously posted by Mr Galala, will depend on the specification and application; is it an inlet flange weld on a high pressure steam chest, or is it a seam on a trash dumpster?

Again, depending on application, some welds will be done 100%, though not necessarily by radiography, as the product or construction is built. Some will be spot radiographed to ensure the veracity of testing by other means and to have a permanent record of the event.

In service inspections (due-diligence maintenance monitoring) is usually aimed at areas more susceptible to failure over time. This is where defect rates as a number of films showing defects would be used. Just one film with a thin spot in the pipe? Fix it and move on. Two or three? Better take a closer look at other potentially thin areas.

Gentlemen,thank you in your time, but I believe that I do not formulate well my question. I will try to expose it with an example:

10 welds, Diameter 6 inches, same welder, Three films per weld.

Two rejections in two different welds (Lack fusion 10mm)

Rejection by weld: 2 of 10 20% rejection

Rejection by films: 2 of 30 6% rejection

Rejection by length: 20mm of 4785,36 mm 0.4% rejection

Very different results at the moment of interpreting the status of the project, the quality of the welder and the welds. In his your opinion, which one is the most appropriate ?. Checking the mentioned codes I get not to much results.
Thank you for your help. Regards

Most specifications that I have dealt with would rate this as a 20% reject rate and the welder's qualifications would be called into question. Further, all welds deposited by this welder would now require inspection by either radiography or ultrasound, magnetic particle testing will not suffice.

Sorry, but if I am paying for or insuring this pipe system, then I have a reasonable expectation of a certain level of quality. Lack of fusion is one of the easiest of defects to avoid, so this leaves everything else about this person's welds suspect.