MISTAKES WITH PENNEYS CAN COST PIPELINES BIG BUCKS

摘要

API Standard 1104 (API 1104), Welding of Pipelines and Related Facilities, requires use of one or more image quality indicators (IQIs) or penetrameters (penneys) on each radiograph of a butt weld. API 1104 permits use of IQIs manufactured to three different specifications, one specifications for wire type IQIs and two specifications for hole- type. Unfortunately, the two hole-type IQIs are quite similar and can easily be mistaken for the other, especially by persons who are not experienced radiographers. Incorrect substitution of one of these types of penneys for the other is difficult to detect during examination of the film. Despite the similarity in the two hole-types of penetrameters, incorrect substitution can allow a group of radiographs with less than specified radiographic sensitivity to be accepted for interpretation. Reduced sensitivity can allow unacceptable imperfections to escape detection during interpretation of radiographs. The authors observed a situation in which incorrect substitution of penneys allowed significant weld imperfections to go undetected and unrepaired. Subsequently a girth weld with undetected but significantly imperfections failed. Mistakes with penneys can have much greater impact on thinner wall pipe where large root pass imperfections can significantly reduce the strength and integrity of a weld. This article contains information useful to inspectors and other persons charged with evaluating acceptability of radiographs and welds. When properly applied this information can help inspectors avoid mistakes with penneys that could eventually cost big bucks.