Machine for manufacturing welded steel pipes and method for handling the machine

A machine for manufacturing welded steel pipes, in which a strip is continuously roll-formed to shape a pipe and its butted seam is welded, having an edge bending roll for constraining under pressure a strip from its pipe edge portions to the boundaries between the pipe edge portions and said pipe side portions to bend the strip, a first center bending roll for constraining under pressure the pipe side portions to bend the pipe side portions, second to fourth center bending rolls for constraining under pressure the strip from the boundaries between the pipe side portions and its pipe bottom portion to the pipe bottom portion and applying lateral pressure to the pipe from both sides to bend the boundaries and the pipe bottom portion and a plurality of cage rolls arranged on both the sides of these center bending rolls, first and second fin pass rolls for further forming under pressure the pipe, are arranged in order from the upstream side to the downstream side of a roll forming process, wherein at least the edge bending roll, the first center bending roll, the first and second fin pass rolls each has a driving means provided thereon, and all the upper rolls of the first to fourth center bending rolls are set in one housing, and all the bottom roll stands of the first to fourth center bending rolls or all the bottom roll stands of the second to fourth center bending rolls are set on one common sub-base plate.