HOLDBACK CONTROL FOR COATING INTERNAL SURFACES OF METAL TUBES

摘要

Apparatus for internally coating a pipe, comprising electric heating means heating a pipe as it is internally spray coated, a plurality of first rollers mounted on a first rotatable shaft having an inlet end proximate the heating means and an outlet end spaced from the heating means, and a plurality of second rollers mounted on a second rotatable shaft parallel to the first shaft and having an inlet end adjacent the heating means. Each second roller is spaced from and adjacent to a corresponding first roller in a paired relationship to thereby define a nesting groove located above the gap between each set of paired rollers. Motive means rotates the shafts and the mounted rollers to rotate the pipe within the nesting grooves of adjacent pairs of rollers. Axial advancing means longitudinally advances the pipe through the heating means and sequentially along the nesting grooves of adjacent pairs of rollers. A movable holdback means is located on the outlet side of the heating means for restraining the advancement of the pipe to a predetermined rate of speed sufficient to insure application of a uniform thin coating of coating material on the pipe internal surface, thereby overcoming thermal and magnetic effects of the heating means which would otherwise advance the pipe faster than the speed of the axial advancing means.