The invention relates to a plant for rolling seamless tubes, typically with a large diameter. The plant comprises: a furnace for billets produced by means of continuous casting; a piercer for piercing the billets; a main continuous rolling mill of the retained-mandrel type with stands having three or more adjustable rolls; a fixed-roll extraction/reducing mill; means for measuring the wall thickness of the semi-finished tube; the main rolling mill being designed to adjust the rolls on the basis of the wall thickness of the tube leaving the extraction/reducing mill; a first intermediate furnace for tubes; an expander for expanding the diameter of the semi-finished tube to a value which is close to that of the finished tube; a reeler for ensuring a uniform surface finish inside the tube; a second intermediate furnace for tubes; a first sizing mill with stands having three or more adjustable rolls for defining the finished diameter; the first sizing mill comprising means for measuring the temperature of the incoming tube and means for measuring the diameter of the outgoing tube and being suitable for adjusting the rolls on the basis of the temperature and diameter; and a cooling bed. The plant also comprises, downstream of the extraction/reducing mill, a bifurcation generating a second line comprising a second sizing mill and a cooling bed. The second sizing mill is similar to the first sizing mill and is positioned off-line with respect to the extraction/reducing mill. The invention also relates to a method for rolling seamless tubes.
