Process for lining high pressure pipeline

Claim 1

A method of lining a section of a high pressure pipeline which utilizes the structural strength of the pipeline to enable the lined pipeline section to be operated at high pressure, said section including first and second pipe flanges disposed at opposite ends thereof, the method comprising: (a) providing a plastic liner having: (i) a wall thickness and composition such that the liner is firm and self-sustaining in tubular form; (ii) an outside diameter sufficiently less than the inside diameter of the pipeline to enable drawing the liner through the pipeline section, but sufficiently large so that the liner can be non-destructively radially expanded against the inside wall of the pipeline; (b) drawing the liner in non-collapsed condition into the pipeline section by pulling the liner from one end area thereof through the pipeline section until the liner is substantially longitudinally co-extensive with the pipeline section; (c) before concluding said drawing step, affixing a first liner flange to the end of said liner segment opposite said one end area; (d) completing the drawing step to position said first liner flange against said first pipe flange; (e) longitudinally stretching the liner within the pipeline section by elongating said liner without exceeding the elastic limit of the liner by pulling said one end area of the liner beyond the length of the pipeline section while said first liner flange prevents longitudinal movement of the opposite end of said liner along the pipeline section; (f) after said stretching step, affixing a second liner flange to said one end area of said liner segment opposite said first liner flange; (g) positioning said second liner flange against said second pipe flange by permitting the liner to elastically retract into the pipeline section; (h) opening at least one bleeding port in the pipeline section; (i) radially expanding the liner against the inside wall of the pipeline to an extent to permanently change the liner outside diameter from its original size to a size conforming to the inside diameter of the pipeline; (j) during step (i), bleeding the space between the liner and the pipeline through the bleeding port; and (k) closing the bleeding port.

Claim 2

A method of lining a section of a high pressure pipeline which utilizes the structural strength of the pipeline to enable the lined pipeline section to be operated at high pressure, said section including first and second pipe flanges disposed at opposite ends thereof, the method comprising: (a) providing a plastic liner having: (i) a wall thickness and composition such that the liner is firm and self-sustaining in tubular form; (ii) an outside diameter sufficiently less than the inside diameter of the pipeline to enable drawing the liner through the pipeline section, but sufficiently large so that the liner can be non-destructively radially expanded against the inside wall of the pipeline; (b) drawing the liner in non-collapsed condition into the pipeline section by pulling the liner from one end area thereof through the pipeline section until the liner is substantially longitudinally co-extensive with the pipeline section; (c) before concluding said drawing step, affixing a first liner flange to the end of said liner segment opposite said one end area; (d) completing the drawing step to position said first liner flange against said first pipe flange; (e) longitudinally stretching the liner within the pipeline section by elongating said liner without exceeding the elastic limit of the liner by pulling said one end area of the liner beyond the length of the pipeline section while said first liner flange prevents longitudinal movement of the opposite end of said liner along the pipeline section; (f) after said stretching step, affixing a second liner flange to said one end area of said liner segment opposite said first liner flange; (g) positioning said second liner flange against said second pipe flange by permitting the liner to elastically retract into the pipeline section; (h) opening at least one bleeding port in the pipeline section; (i) radially expanding the liner against the inside wall of the pipeline to an extent to permanently change the liner outside diameter from its original size to a size conforming to the inside diameter of the pipeline; (j) during step (i), bleeding the space between the liner and the pipeline through the bleeding port; and (k) closing the bleeding port.