Assessment of Circumferential SCC on an Ethane Pipeline

This paper describes the analysis conducted on circumferential SCC found on a high vapour pressure ethane pipeline. The damaged section of pipe was located near a road crossing and was cut out before failure. A total of 146 cracks were identified with lengths ranging from a 1 mm to 50 mm. Three different techniques were evaluated for crack depth measurement: balanced field electromagnetic technique (BFET), sequential grinding, and microscopic cross-section examination. Crack depths of up to 2.6 mm (52% wall thickness) were identified. The failure pressure was determined by a burst test. The pipe began leaking at a pressure of 16 865 kPa, well in excess of the maximum operating pressure of 9930 kPa. The results of the burst test are compared to failure pressure calculations for an undamaged pipe and a pipe containing an axial crack with dimensions similar to the actual failed crack.