| 摘要 |
PURPOSE:To reduce a production time and to improve efficiency, by previously applying a dummy cover using a tubing die onto a portion where a cover is not required. CONSTITUTION:First, a full length of a steel pipe is covered with a dummy polyethylene cover having a thickness of 0.3mm. using a tubing die, and then the dummy polyethlene cover is stripped off with an intermediate portion of 1m where the cover is not required being left. The pipe is then subjected to extrusion covering using a double tubing die with an asphalt adhesive extruded inside and a polyethylene outside to cover the pipe with the two layers. Finally, the left dummy polyethylene cover on the portion where a cover is not required is stripped off together with the asphalt adhesive and outer polyethylene layers on the dummy cover to obtain a covered 600A steel pipe having a length of 15m with a 1m intermediate portion thereof uncovered. |
