Getting to the Bottom of the Groove: NDE of SSWC

Abstract Selective seam weld corrosion presents a set of unique circumstances that results in difficulty in accurately determining the groove depth. Classification and measurement of in-the-ditch selective seam weld corrosion (SSWC) has proved difficult due to many factors. On the classification side, lack of fusion (LOF) and SSWC often look similar and distinguishing between the two can prove challenging. Visual difficulties can then result in an incorrect classification which may affect the determined remaining life or repair criteria. On the sizing side, narrow SSWC may prevent sizing by pit gauges and surrounding corrosion may prevent phased array UT from measuring the depth. Surrounding external corrosion creates a difficult surface to land the NDE equipment and tight features prevent the use of hand tools, such as pit gages from reaching the bottom of the groove. Lack of a defined procedure can lead to a varying level of success when inspecting these features. Accurate depth measurements are critical when determining a fitness for service, remaining life, or even the appropriate repair method. This paper focuses on the main task of a recent Pipeline Research Council International project, PRCI NDE 2-15, whereby the goal was to develop in-the-ditch evaluation methods and necessary tools to address difficulties associated with determining SSWC depth. Through a series of targeted NDE, a specialized NDE procedure was developed to identify external SSWC verses other defects such as lack of fusion or seam trim and measure external SSWC depth and length. In some cases, this NDE procedure combines multiple NDE techniques, each building on each other to determine the grooving depth. Finally, this protocol was validated through metallurgical examination. This paper provides a first of its kind to provide the pipeline industry with guidance when attempting to inspect and properly classify SSWC. This paper provides the first step to gaining a better understanding of SSWC inspection.