| 摘要 |
PURPOSE:To definitely control the thickness of polyethylene film formed on a welded steel pipe by a method in which beads on the surface of the welded steel pipe are detected while turning the steel pipe, and by its detection signal, the amount of polyethylene sheet to be extruded is controlled. CONSTITUTION:A welded steel pipe 8 is sent axially (in the direction of arrow A) while being held and turned by skew rollers 7, and polyethylene sheet 6 in a strip state is extruded from the tip of a T die 4, pressed on the outer surface of the steel pipe 8 by a push roller 5, and then rolled spirally around the steel pipe 8. A weld bead detector 1 is provided at a place where the polyethylene sheet 6 is not yet wound, and its output end is connected to a polyethylene extruder controller 2. And, when the weld bead is high, the amount of the polyethylene sheet to be extruded is increased, but when it is low, the amount of the sheet is reduced in order to obtain a fixed thickness of polyethylene coat. |
