A method for welding a plurality of pipes, including first, second and third pipes, to each other, the method comprising the steps of: (a) providing a clamping apparatus comprising a rigid frame, first and second clamping means for clamping the pipes, said first and second clamping means being supported on the frame; (b) engaging a side of the first pipe with the first clamping means and a side of the second pipe with the second clamping means and with a first end of the first pipe disposed at a welding distance from and in line with a first end of the second pipe; (c) operating a welding apparatus to make a welding seam to connect the respective first ends of the first and second pipes; and (d) moving the clamping apparatus along the second pipe to a second end of the second pipe and repeating steps (b)-(c) to weld the second end of the second pipe to a first end of the third pipe, wherein the method comprising the steps of determining a shape of the first pipe with help of the first clamping means, storing data pertaining to said shape in a memory as shape data, and bringing the second clamping means into engagement with the second pipe based on the shape data.