US 4,985,196 AGranted

Pipe liner process

AssigneePipe Liners, Inc.

InventorsPatrick LeDoux, Lue Fourgaut

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Abstract

Method is provided for lining a pipe wherein a thermoplastic liner is initially formed in a cylindrical shape with a diameter slightly larger than the internal diameter of the pipe. The liner is temporarily deformed at an elevated temperature to a different cross-section, preferably U-shaped, to reduce it overall cross-sectional dimension to facilitate insertion into the pipe to be lined. Once inserted, the pipe liner is re-heated and pressurized so that the shape memory characteristics of the thermoplastic material causes the liner to return to its original cylindrical shape. Pressure within the liner is increased in two stages to cause the liner to conform to the interior surface of the pipe. An expansion pig may also be employed to ensure even more exact conformance. After expansion, ends of the liner which extend beyond the pipe are flared into engagement with the pipe flanges.

Claims20

Dependent claims

A process for installing in situ a thermoplastic liner in a generally horizontally extending pipe, comprising the steps of:

(a) providing a hollow generally cylindrical liner formed of thermoplastic material having an original outer diameter larger than the inside diameter of the pipe to be lined and a predetermined wall thickness;
(b) altering the cross-sectional shape of the liner to reduce the cross-sectional dimension thereof at a shape memory activation temperature, so as to permit the liner to be pulled into the pipe;
(c) pulling said altered liner into said pipe such that end portions of said liner extend beyond opposite ends of said pipe;
(d) partially expanding the liner end portions which extend beyond the opposite ends other pipe by mechanical means inserted into said liner end portions such that said expanded lining end portions approximate the original cylindrical shape of said liner;
(e) sealing the expanded lining end portions beyond the opposite ends of said pipes to seal the interior of said liner at its opposite ends;
(f) subsequent to the step of sealing the liner and while maintaining the liner sealed, generally conforming said liner to the interior wall of the pipe while maintaining substantially the original predetermined wall thickness by (1) injecting a heated fluid into and through said sealed liner, (2) pressurizing the interior of said liner to a first predetermined pressure above atmospheric pressure by means of said heated fluid and (3) reheating said liner to a predetermined temperature by heat transfer from said heated fluid to said liner, whereby, the liner returns substantially to its remembered cylindrical shape;
(g) then increasing the pressure in said liner to a second predetermined pressure above said first predetermined pressure to conform the liner substantially precisely to the interior wall surface contours of the pipe;
and
(h) while the liner is still hot, introducing a cooling fluid into the liner for flow therethrough to fix the liner in final form in conformance to the interior wall of the pipe.

6 more elements

A process for installing in situ a thermoplastic liner in a generally horizontally extending, generally cylindrical pipe, comprising the steps of:

(a) providing an elongate hollow liner formed of thermoplastic material having a cross-section altered at a shape memory activation temperature from a generally cylindrical cross-section having an original outer diameter substantially comparable to the inside diameter of the pipe to be lined to a reduced cross-section having reduced cross-sectional dimensions to enable the liner to be pulled into the pipe, said liner in said altered cross-section having a predetermined wall thickness;
(b) inserting said altered liner into said pipe such that end portions of said liner extend beyond opposite ends of said pipe;
(c) partially expanding the liner ends portions which extend beyond the opposite ends of the pipe by mechanical means inserted into said liner end portions such that said expanded liner end portions approximate the original cylindrical shape of said liner;
(d) sealing the expanded liner end portions beyond the opposite ends of said pipes to seal the interior of said liner at its opposite ends;
(e) subsequent to the step of sealing the liner and while maintaining the liner sealed, generally conforming said liner to the interior wall of the pipe while maintaining substantially the original predetermined wall thickness by (1) injecting a heated fluid into and through said sealed liner, (2) pressurizing the interior of said liner to a first predetermined pressure above atmospheric pressure by means of said heated fluid and (3) reheating said liner to a predetermined temperature by heat transfer from said heated fluid to said liner, whereby, the liner returns substantially to its remembered cylindrical cross-section;
and
(f) then increasing the pressure in said liner to a second predetermined pressure above said first predetermined pressure to conform the liner substantially precisely to the interior wall surface contours of the pipe;
and
(h) while the liner is still hot, introducing a cooling fluid into the liner for flow therethrough to fix the liner in final form in conformance to the interior wall of the pipe.

6 more elements

Dependencies are inferred from the claim text.