Mass Production and Installation of X100 Linepipe for Strain-Based Design Application Available to Purchase

Continuous efforts have been made for the realization of strain-based design pipeline using high grade linepipe materials. Two demonstrative constructions of the pipelines using X100 linepipe proved sufficient materials properties for strain-based design and high quality field welding with good productivity. In order to verify further applicability of high strain X100 linepipe for long distance transmission, large scale installation of X100 pipeline was accomplished. Mass production of X100 linepipe of about 2,000 metric tons with the size of 42^″OD and 14.3mm wall thick was successfully conducted by applying recent developed TMCP process including accelerated cooling and online heat treatment process and UOE pipe forming. Field girth welding was safely completed by the dual tandem pulsed GMAW, and sufficient girth weld properties were demonstrated. This paper will describe material development and mass production results of X100 linepipe for strain-based design which specifying longitudinal tensile properties such as Y/T ratio and uniform elongation. In order to securely specify the shape of stress-strain curve without Luders elongation, material parameter “stress ratio” was introduced for the material specification for compressive strain capacity. Stringent base metal requirements were imposed for base metal material properties in this project. One of the most challenging aspects in developing high strain linepipe is to balance uniform elongation and Charpy absorbed energy. Dual phase microstructure is essential to improve strain capacity, but this may lead to lower Charpy absorbed energy. Therefore, precise control of microstructure by controlling plate manufacturing parameter was required. In addition, on-line heating process subsequently after accelerated cooling enabled increase of Charpy energy without deteriorating uniform elongation. Girth weld properties were closely evaluated using the X100 pipe in as UOE condition and after external coating. All the material properties of base metal and girth weldment of the X100 linepipes used for this project fulfill the stringent requirement for strain-based design consideration to prevent buckling and weld fracture.