The plant for producing a corrugated board includes one or more single facers and a double facer, as well as respective unwinders for unwinding reels of paper webs. Arranged along the production line, in suitable positions, are thermographic cameras which acquire images through which it is possible to trace the various characteristics of the cardboard, for example the moisture content thereof, detect manufacturing defects, after which it is possible to intervene on one or more process parameters so as to eliminate the causes of the defects.

In a device for detecting a paper splice part of a cardboard sheet and a device for producing a cardboard sheet, the device for detecting a paper splice part of a cardboard sheet, which detects a sheet paper splice part of a cardboard sheet that has a first sheet, a corrugated second sheet, and a third sheet bonded together, comprises: a sheet paper splice detection unit that detects the sheet paper splice part on the basis of the shape of the sheet and that is placed between a position at which sheets are spliced and a position at which the sheets are bonded in a sheet carrying direction; a marking device that marks the sheet paper splice part on the downstream side of the sheet paper splice detection unit in the sheet carrying direction; and a mark detection device that detects the mark on the downstream side of the marking device in the sheet carrying direction.