US 4,950,446 AGranted

Method of lining pipes

AssigneesOsaka Gas Co., Ltd., Osaka Bosui Construction Co., Ltd.

InventorsNamio Kinumoto, Toshihiko Kikuchi, Akeshi Kegasa

Life of this patent

Estimating the term…

Loading patent…

Abstract

A method of lining a pipe with a rigid plastic tube inserted in the pipe by enlarging the tube from inside with application of heat and pressure. The method includes enlarging the tube by an electrically heatable enlarging pig moved through the tube, retaining the enlarged portion of the plastic tube with compressed air supplied to the interior of the tube, and preheating the unenlarged portion of the plastic tube with a portion of the compressed air heated by being passed through air heating channels of the pig. The use of the pig eliminates the material limitations to be otherwise imposed on the tube, and therefore the softening point, of the plastic tube. The preheating of the unenlarged portion of the plastic tube renders the pig movable through the tube at an increased speed to achieve an improved work efficiency.

Claims10

Dependent claims

A method of lining a pipe with a plastic tube, comprising the steps of:

placing the plastic tube within the pipe to be lined, the plastic tube having a diameter smaller than that of the pipe;
placing a substantially conical pig within the plastic tube at one end thereof, the conical pig having a heater and a through-hole air channel therein;
heating the conical pig by the heater;
supplying an air flow into the inside of an unexpanded portion of the tube ahead of the conical pig has been inserted through the through-hole air channel of the conical pig such that the air flow is heated by heat of the heated conical pig and the resulting heated air flow preheats the unexpanded portion of the tube;
and
moving the conical pig along an axial direction of the plastic tube such that the conical pig heats the tube and physically expands the heated tube to line the tube against an inside of the pipe.

3 more elements

Dependencies are inferred from the claim text.