Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,... – Submerging – raising – or manipulating line of pipe or cable...
Patent
1998-08-20
2000-08-29
Taylor, Dennis L.
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
Submerging, raising, or manipulating line of pipe or cable...
405158, 405171, F16L 112
Patent
active
061098299
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to improved methods and apparatus for transporting a pig along the interior of a pipeline or the like, particularly but not exclusively a subsea pipeline. In its preferred form, the invention is particularly applicable to the use of a pig for the purpose of installing a liner, typically of polymer material, in an existing pipeline.
In accordance with a first aspect of the invention, there is provided a method for installing a liner in a pipeline, comprising the steps of flooding the interior of the pipeline and pulling the liner along the length of the interior of the pipeline from an upstream end thereof to a downstream end.
Preferably, said liner is pulled by means of a pig which forms a substantially fluid-tight seal with the interior walls of the pipeline and in which a hydrostatic head is applied on either side of the pig, the method comprising reducing the hydrostatic head on a downstream side of the pig such that the hydrostatic head on said downstream side is less than the hydrostatic head on an upstream side of the pig, whereby said liner is transported along at least part of said pipeline by the resultant pressure differential between said upstream and downstream sides of said pig.
Preferably also, said pipeline is an existing subsea pipeline, an inlet riser is connected to the upstream end of the pipeline in which the liner is to be installed, and an outlet riser is connected to the downstream end of the pipeline, said risers each extending to the water surface and said risers and the pipeline being open to hydrostatic pressure, the pig is introduced into the inlet riser, and said pressure differential is created by pumping water out of said outlet riser.
In accordance with a second aspect of the invention, there is provided apparatus for installing a liner in a pipeline, comprising means flooding the interior of the pipeline and pulling means for pulling the liner along the length of the interior of the pipeline from an upstream end thereof to a downstream end.
Preferably, said pulling means comprises a pig having fluid seal means adapted to form a substantially fluid-tight seal with the interior walls of the pipeline, means for applying a hydrostatic head on either side of the pig, and means for reducing the hydrostatic head on a downstream side of the pig such that the hydrostatic head on said downstream side is less than the hydrostatic head on an upstream side of the pig, whereby the liner may be pulled along at least part of said pipeline by the resultant pressure differential between said upstream and downstream sides of said pig.
Preferably also, said pipeline is an existing subsea pipeline, and said means for applying a hydrostatic head on either side of the pig includes an inlet riser adapted to be connected to the upstream end of the pipeline in which the liner is to be installed, and an outlet riser adapted to be connected to the downstream end of the pipeline, said risers each extending to the water surface and said risers and the pipeline being open to hydrostatic pressure, in use, the pig being adapted to be introduced into the inlet riser, and further including pump means for creating said pressure differential by pumping water out of said outlet riser.
In accordance with a third aspect of the invention, there is provided a method for transporting a pig along the interior of a pipeline, in which the pig forms a substantially fluid-tight seal with the interior walls of the pipeline and in which a hydrostatic head is applied on either side of the pig, the method comprising reducing the hydrostatic head on a downstream side of the pig such that the hydrostatic head on said downstream side is less than the hydrostatic head on an upstream side of the pig, whereby said pig is transported along at least part of said pipeline by the resultant pressure differential between said upstream and downstream sides thereof.
In accordance with a fourth aspect of the invention, there is provided apparatus for transporting a pig along the interior of a pipeline, compris
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Database WPI, Section PQ, Week 8350, Derwent Publications Ltd., London, Great Britain, Class Q67, AN 83-842868, SU 994856.
"Underwater Gamble Pays Off", The Oil & Gas Journal, vol. 57, No. 4, Jan. 26, 1959, p. 105.
Coflexip Stena Offshore Ltd.
Taylor Dennis L.
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