Abstract: For deploying a pipe string, a traveling table is movably mounted to a mast and clamps an upper region of a pipe section. For weld alignment, at least two centralizer units are mounted to the mast between the traveling table and an upper end of the pipe string. One centralizer unit translates a lower region of the pipe section radially for alignment of the lower end of the pipe section with the upper end of the pipe string. Another centralizer unit at a middle region of the pipe section translates the middle region of the pipe section radially for correcting angular mismatch of the lower end of the pipe section with the upper end of the pipe string. Each centralizer, for example, includes four hydraulic cylinders, each operative for driving a respective pinned cam having a face carrying a roller for contacting the pipe section.