| 摘要 |
PURPOSE:To obtain a duct wherein a heat insulation work is unnecessary after piping, by winding and rotating spirally a heat insulation layer with a wider width than a spiral pitch width on an outside periphery surface of a metallic tube, and winding and rotating a thin covered layer on an outside surface of the heat insulation layer. CONSTITUTION:A spiral metallic tube 1 is formed by bending one edge of a metallic plate 1A with a thin and strip state in a U shape and the other edge in an L shape and by engaging both edges during execution of winding with rotation and spirally. Then, a heat insulation layer 2 is formed by feeding diagonally a strip state body 2A of a heat insulation material continuously on an outside periphery face of a spiral metallic tube 1 and winding and rotating it spirally with a wider width W than a spiral pitch width W of a spiral state spiral metallic tube. Then, a heat insulation layer 3 is formed by feeding diagonally a strip state body 3A on an outside periphery face of the heat insulation layer 2 and strongly winding and rotating it spirally. By this, a heat insulation work is finished as it is, if a tube fed with a predetermined length is distributed to a construction site. |
