High wall thickness DLSAW pipes for sour service application by JCOE process

Increasing demand in oil and gas supply has increased the number of pipeline installations for offshore and sour service applications. Projects demand higher resistance to H2S corrosion because of the higher sulfur content observed in the geographical locations. Welspun took a challenging initiative in developing a thick wall forming process with optimized dimensional properties for offshore sour service pipeline application. This paper reports on the manufacturing of API5LX65MSO/L450MSO PSL2 (36”OD x 42.90 mm WT) pipe utilizing the JCOE process at Welspun Pipes Mill in Dahej-Gujarat-India. Special precautions were taken during manufacturing to improve the weld and HAZ properties with respect to toughness at low testing temperatures and control of the pipe manufacturing process without affecting the HIC performance. Selection of plates was considered with respect to alloy design, cleanliness and mechanical properties of both plate and pipe so as to meet the stringent requirements for HIC, hardness, CVN and DWTT as per the client specification. Plates were supplied by voestalpine Grobblech GmbH-Austria. The levels of S<0.0009% and P<0.008% with low values of (Nb+V+Ti)<0.065%, Pcm<0.15% and CE<0.35% were obtained in the TMCP plates. Ultra fine homogeneous ferrite microstructure throughout the thickness has been a great help in pipe forming resulting in improved mechanical properties and excellent HIC test results for plate and pipe. JCO forming and mechanical pipe expansion process parameters were controlled within a narrow range to optimize the pipe dimensional properties such as local and global out-of-roundness in the finished pipes having a low D/t ratio (~21). Hardness and CVN in weld metal and HAZ have been controlled by proper selection of welding consumables, uniform and effective heating of flux, good control of welding parameters and pre-heating of pipe edges before ID welding. (AU) © CBMM