Abstract

The invention relates to a screen pipe to be used in dry forming of web material in order to distribute fiber material blown into the screen pipe through a jacket (2) of the pipe onto a wire arranged to move under the pipe. The fiber material provided inside the screen pipe is made to move for example by means of a spiked roll placed inside the pipe, so that the movement of the fiber material has both a radial and a tangential component with respect to the jacket (2) of the screen pipe. The jacket comprises on its inner surface profiled grooves (8) in the pipe's axial direction. The edge (8a) of the profiled groove is situated downstream with respect to the tangential component of the fiber flow. The upstream edge (8b) of the groove is positioned downstream with respect to the tangential component of the fiber flow. The bottoms of the profiled grooves comprise holes or slots (9) through which the fibers are discharged from the screen pipe. In the invention, the downstream edge (8a) of the profiled groove is at a more acute angle to the tangential component of the fiber material flow than the upstream edge (8b).