Patent ID: 6089276
Filing Date: 2000-07-18
Classification: F16L

Abstract:
In renovating an existing underground pipe with a new metal pipe installed inside the underground pipe, a method of repairing the existing underground pipe characterized by transporting a metal tubular material as wound up in the form of a roll to a repair site, the tubular material being folded flat by plastic deformation so as to be diminished in effective outside diameter and being capable of forming a new metal pipe of an outside diameter corresponding to the inside diameter of the underground pipe when inflated by application of pressure from inside, installing the roll of tubular material on the ground, subsequently unwinding the tubular material from the roll, inserting the tubular material into the underground pipe through an underground work pit while passing the tubular material between curl removing correction rolls immediately after unwinding for correction to a straight form, closing opposite ends of the inserted portion of the tubular material, and thereafter inflating the closed portion of the tubular material, by applying pressure thereto from inside with a pressure fluid to form a new metal pipe of circular cross section from the tubular material.