During radiographic testing (RT) of a pipeline weld, what radiographic indications would warrant rejection based on API 1104?

According to API 1104, several radiographic indications observed during radiographic testing (RT) of a pipeline weld would warrant rejection. Cracks, regardless of their size or orientation, are unacceptable and cause for rejection because they represent a significant loss of structural integrity and can propagate under stress. Lack of fusion, which occurs when the weld metal does not properly fuse with the base metal, is also cause for rejection. This indication appears as a dark line on the radiograph and indicates a weak bond. Incomplete penetration, where the weld does not extend through the full thickness of the pipe wall, is another rejectable indication. Porosity, which are small gas pockets trapped in the weld metal, is generally acceptable within certain limits based on size and distribution. However, excessive porosity, clustered porosity, or linear porosity (aligned pores) would be cause for rejection. Slag inclusions, which are non-metallic solid materials trapped in the weld, are also assessed based on their size and distribution. Large or numerous slag inclusions are rejectable. Undercutting, a groove melted into the base metal adjacent to the weld toe and left unfilled by weld metal, weakens the weld and is rejectable if it exceeds the allowable limits for depth and length specified in API 1104. Finally, any indication of burn-through, which is excessive penetration that melts through the pipe wall, is a rejectable defect. The acceptance criteria for these indications are detailed in API 1104 and depend on factors such as pipe diameter, wall thickness, and service conditions. A qualified radiographer must interpret the radiographs and determine whether any indications exceed the allowable limits, leading to weld rejection.