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BR-PI1106082-B1 - METHOD OF WINDING AND EXTENDING THE DUCT WITH AN ADDITIONAL DUCT SECTION

Abstract

ASSEMBLY, WINDING AND UNWINDING OF AN INTERNALLY CAPPED TUBE. The present invention relates to a method of winding and unwinding and extending duct with an additional duct section. The duct (6) has a corrosion-resistant metallic coating tightly fitted within a carbon steel duct tube. The method comprises the following: sealing the duct at the guide end and a trail end, and flooding the duct with liquid in the duct to a second pressure of up to 1500 kPa (15 bar); pressurizing the liquid in the duct to a second pressure greater than 2500 kPa (25 bar); winding the duct at least partially onto a spool from the guide end with pressurized fluid up to the second pressure; depressurizing the duct; and weld the additional section of duct to the drag end of the duct to form an extended duct with a new drag end, wherein the additional duct section is not flooded with liquid before being welded to the drag end of the duct.

Inventors

  • JOHN ARTHUR MAIR

Assignees

  • SUBSEA 7 LIMITED

Dates

Publication Date
20260310
Application Date
20110407
Priority Date
20100407

Claims (11)

  1. 1. Method of winding and extending the duct (6) with an additional duct section (6), wherein the duct (6) has a corrosion-resistant metallic coating firmly fitted to a carbon steel duct of the duct (6), the method comprising: sealing the duct (6) at a front end and at a rear end, and flooding the duct (6) with liquid at a first pressure of up to 1500 kPa (15 bar); characterized by pressurizing the liquid in the duct to a second pressure greater than 3000 kPa (30 bar) and less than 5000 kPa (50 bar); winding the duct at least partially onto the reel (300) from the guide end with the pressurized fluid at the second pressure; depressurizing the duct (6); weld the additional section of the duct to the rear end of the duct (6) to form an elongated duct (6) with a new rear end, wherein the additional section of the duct is not flooded with liquid before it is welded to the rear end of the duct (6).
  2. 2. Method according to claim 1, characterized in that the steps are repeated a plurality of times to lengthen the duct (6) with a plurality of additional duct sections, wherein for each repetition the duct (6) sealing step at the rear end comprises sealing the duct (6) to a new rear end resulting from the lengthening of the duct (6) with a preceding additional duct section.
  3. 3. Method according to claim 2, characterized in that it further comprises, after welding an additional end duct section to the duct (6), the steps of: sealing the duct (6) at the front end and at the rear end, and flooding the duct (6) with liquid at a first pressure of up to 1500 kPa (15 bar); pressurizing the liquid in the duct (6) to a second pressure greater than 3000 kPa (30 bar) and less than 5000 kPa (50 bar); winding the duct (6) completely onto the reel (300) with the pressurized fluid at the second pressure.
  4. 4. Method according to claim 2 or 3, characterized in that the sealing step of the duct (6) at the forward end comprises maintaining a seal at the forward end of the duct (6) from one sealing step to a subsequent sealing step.
  5. 5. Method, according to any of the preceding claims, characterized in that a first pump (6) is used for the stage of flooding the duct (6) and a second pump is used for the stage of pressurizing the duct (6), wherein the first pump is a high volumetric distribution pump and the second pump is a high pressure pump.
  6. 6. Method, according to any of the preceding claims, characterized in that the pressurizing step comprises increasing the pressure in the duct (6) in a plurality of steps, wherein in each step the pressure is increased by a pressure boost and the duct (6) is checked for leaks.
  7. 7. Method, according to any of the preceding claims, characterized in that it further comprises an initial step of inserting the pig (41) into the duct (6), and in which the flooding step comprises flooding the duct (6) between the front end and the pig (41), thereby inducing the pig (41) towards the rear end.
  8. 8. Method according to claim 7, characterized in that the depressurization step comprises retaining depressurized liquid between the pig (41) and the front end.
  9. 9. Method according to claim 7 or 8, characterized in that before the flooding step, a fluid spacer is inserted between the pig (41) and the sealed rear end to provide a buffer for the seal at the rear end.
  10. 10. A method, according to any of the preceding claims, characterized in that the liquid is water.
  11. 11. Method according to claim 10, characterized in that the water contains a corrosion inhibitor.

Description

Field of invention [0001] The present invention relates to methods of winding a duct in preparation of the reel for duct launching, and also to the method of launching the duct. Background of the Invention [0002] US Patent A-3,934,647 describes a pipeline launching system including the technique of testing the pipeline hydrostatically as it is loaded onto the reel. When the pipeline is initially launched onto the reel, one end of the section is passed through the reel hub or flange plate. The section end is attached to a full-opening gate valve, and a bleed valve is connected to an open nozzle. To fill the line with test water, a so-called "pig" is used; this is a device that is mobile along the pipeline and can be temporarily fixed at any desired location inside the pipeline. A pig is generally used to separate different fluids or gases, but it can also serve for cleaning and inspecting the inside of the pipeline bore. The pig is inserted into the open nozzle at the end of the pipeline reel. A pig providing a water seal on the inner surfaces of the pipeline, such as a spherical pig, should be used to minimize water leakage passing through the pig. A line from a low-pressure water source is then attached to the nozzle. The pig is pushed forward in the water as the line is filled. At the other end of the line, a test head assembly has been welded on. This head assembly includes bleed valves to remove any collected air and to allow the pig to be driven, a full gate valve opening to allow the pig to exit the section to be tested, and the connecting valve to pressurize the line and monitor the line pressure. The pig is pumped through the line with all valves open except the bleed valve at the end of the reel until it reaches the front end. The end of the valve is then closed and all air is expelled from the other valves. When all air is expelled, the gate valves are closed. The line is then pressurized through one of the small valves. [0003] When the test is completed, the pig and water are pushed back towards the reel by air pressure applied to the end of the bleed valve with the gate valve on the test assembly fully open. The gate valve or bleed valve at the end of the reel is used to control the flow of test water from the pipe and to seal the pipe after the pig has moved back far enough so that the test assembly can be removed. [0004] A method for laying pipeline on the seabed as described in patent WO 2008/072970 A1. As described in that document, with an increasing need to transport unprocessed well streams from submerged installations and a more frequent occurrence of the need to transport aggressive fluids, there is a growing demand for corrosion-proof pipelines. However, the cost of manufacturing a pipeline from fully corrosion-proof material has increased dramatically, and therefore less expensive alternatives are needed. [0005] Among these less expensive alternatives, there is carbon steel duct with a corrosion-resistant inner lining or coating. These ducts, referred to as lined or coated ducts, combine the strength of low-cost carbon steel with the corrosion resistance of the coating. The coating is usually produced from a corrosion-resistant material, for example, stainless steel, austenitic chromium-nickel based stainless steel superalloys, for example, Inconel (RTM) or another alloy, and typically has a thickness of 1-7 mm, most commonly around 3 mm. [0006] There are several ways available to attach the liner to the inner surface of a carbon steel pipeline. The liner may be installed by mechanical contact, such as plastic expansion of a loose inner liner inside, so as to elastically deform the carbon steel exterior of the pipeline, thus firmly fitting the inner liner inside the pipe when the expanding internal pressure is removed, or by a metallurgical bonding by means of hot rolling, welding, brazing or cap welding. The least expensive alternative is to firmly fit the inner liner to the carbon steel pipeline with so-called metal contact, generally without any adequate space in it. However, when winding such a pipeline onto a pipeline launching drum or during the winding of such a pipeline onto a pipe launching drum, the inner liner may deform by buckling or wrinkling. Such deformation may locally restrict the inner diameter or otherwise affect performance, which is undesirable. [0007] As described in Patent WO 2008/072970 A1, this wrinkling effect can be avoided if the pipeline is pressurized during winding and/or unwinding. The application of pressure ensures that the inner coating retains direct metallic contact with the exterior of the pipeline as the two are wound or unwound from the storage reel of a pipeline laying vessel and thus subjected to bending or performance. [0008] This pipeline is typically assembled from individual extensions, usually about 12 meters long, which are welded into sections that are typically 750 meters to 2000 meters long and are known as "stalks". These stalks are