Procedure to assist the inspection of steel tubes in production, comprising the following steps: a. Acquire measurement data on the geometry of a steel tube, which is representative of physical measurements made from the outside; b. Based on this measurement data, generate converted measurement data, forming a three-dimensional pixel representation of the inner wall of the said tube, over a longitudinal area of the tube, with the said three-dimensional representation referring to a selected system of coordinates, with a point of origin and an axis identified with respect to the tube; c. Prepare the template data, which is representative of the overall geometry of a calibration body; this template data is applicable in the said system of coordinates selected; d. Consider an initial section of the tube, for which converted measurement data is available, and based on this converted measurement data and the template data, determine a critical size that is representative of the margin of passage of the calibration body within this section of the tube; e. Selectively repeat operation d/ for other tube sections, offset from one another with overlap, and f. Establish a diagnosis of the traversability of the said longitudinal area of the tube by the calibration body, based on the critical sizes obtained in steps d/ and e/ and the relative positions of the successive tube sections; Characterised in that: - In step c/, the template data includes an overall outer diameter of the calibration body; - Step d/ includes the following sub-steps: d1. Determine a cylinder inscribed inside the tube section, and d2. Determine the difference between the diameter of the inscribed cylinder and the overall diameter of the calibration body, as a critical size; and - For each pair of adjacent tube sections, step e/ includes the establishment of the possibility of passing from one section to the next based on the said critical size, the angular deviation between the axes of the two tube sections and at least one longitudinal dimension of the calibration body. a. Acquire measurement data on the geometry of a steel tube, which is representative of physical measurements made from the outside; b. Based on this measurement data, generate converted measurement data, forming a three-dimensional pixel representation of the inner wall of the said tube, over a longitudinal area of the tube, with the said three-dimensional representation referring to a selected system of coordinates, with a point of origin and an axis identified with respect to the tube; c. Prepare the template data, which is representative of the overall geometry of a calibration body; this template data is applicable in the said system of coordinates selected; d. Consider an initial section of the tube, for which converted measurement data is available, and based on this converted measurement data and the template data, determine a critical size that is representative of the margin of passage of the calibration body within this section of the tube; e. Selectively repeat operation d/ for other tube sections, offset from one another with overlap, and f. Establish a diagnosis of the traversability of the said longitudinal area of the tube by the calibration body, based on the critical sizes obtained in steps d/ and e/ and the relative positions of the successive tube sections; - In step c/, the template data includes an overall outer diameter of the calibration body; - Step d/ includes the following sub-steps: d1. Determine a cylinder inscribed inside the tube section, and d2. Determine the difference between the diameter of the inscribed cylinder and the overall diameter of the calibration body, as a critical size; and d1. Determine a cylinder inscribed inside the tube section, and d2. Determine the difference between the diameter of the inscribed cylinder and the overall diameter of the calibration body, as a critical size; - For each pair of adjacent tube sections, step e/ includes the establishment of the possibility of passing from one section to the next based on the said critical size, the angular deviation between the axes of the two tube sections and at least one longitudinal dimension of the calibration body.