Reeled Pipeline Accessory Joining Under Internal Pressurization
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Solution Overview
Problem
Mechanically-lined pipes (MLP) experience deformation issues such as wrinkling and buckling during spooling and unspooling due to the difference in yield strength between the outer and inner materials, which can lead to fluid flow hindrance, reduced fatigue life, and complications in installing pipeline accessories in reel-lay operations.
Innovation Solution
A method involving suspending a pipeline on a reel-lay tower, draining and repressurizing the liquid, and using a pig to expel air while joining structures to the pipeline, ensuring fluid communication and minimizing deformation by maintaining pressurization and fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mechanically-lined pipes are spooled and unspooled during reel-lay operations, then pipeline installation efficiency is improved, but the inner liner sleeve experiences deformation such as wrinkling and buckling due to bending stresses
Solution Approach 1:
The pipeline is preliminarily filled with a pressurising liquid before spooling operations. This pre-pressurization creates internal pressure that counteracts external bending stresses during spooling and unspooling, preventing liner sleeve deformation before it occurs
Solution Approach 2:
The internal pressure parameter of the pipeline is changed and maintained at elevated levels during spooling and unspooling operations. This parameter change transforms the mechanical state of the pipe, allowing it to withstand bending stresses without liner deformation
2Adaptability or versatility
If pipeline accessories are installed by cutting and welding during reel-lay operations, then pipeline configuration flexibility is improved, but operational delays occur due to pressure reduction and repressurization cycles
Solution Approach 1:
Pipeline accessories are preliminarily joined to the pipeline while it remains in the reel-lay vessel, before the pipeline is deployed to the seabed. This preliminary action allows configuration changes to be made while the pipeline is still accessible and pressurized, avoiding time-consuming pressure cycles
Solution Approach 2:
The joining operation is merged with the reel-lay process itself, allowing accessories to be installed as part of the continuous pipeline deployment rather than as a separate post-deployment operation. This integration eliminates idle time between laying and accessorization
3Manufacturing precision
If the pipeline is filled with pressurising liquid during spooling, then liner sleeve deformation is reduced, but air pockets are trapped in the pipeline affecting fluid flow
Solution Approach 1:
Instead of trying to eliminate air pockets after they form, the system inverts the approach by using the pressurising liquid to actively push trapped air pockets out through high points in the pipeline during the filling and pressurization process
Solution Approach 2:
The trapped air pockets, which are normally harmful, are converted into a beneficial element by using the pressure differential created during filling to propel the air pockets through the pipeline and expel them at high points, thereby clearing the line of harmful air accumulations
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively reduces deformation and air pockets in the pipeline, allowing for smoother installation of accessories and reducing operational delays in reel-lay operations, thereby enhancing the efficiency and reliability of subsea pipeline installation.
Implementation Method 1
A method involves suspending a pipeline on a reel-lay tower, draining and repressurizing the liquid, and using a pig to expel air while joining structures to the pipeline, ensuring fluid communication and minimizing deformation by maintaining pressurization and fluid flow
Implementation Method 2
pumping additional pressurising liquid into a leading end of the pipeline on the reel to flood the trailing end portion and to propel the pig from the trailing end portion into the conduit of the structure, thereby expelling through a port of the structure air that was trapped in the trailing end portion between the pig and the structure
Implementation Method 3
Nominally rigid pipes have enough flexibility to be bent if a minimum bend radius is observed. When spooling, bending extends beyond elastic limits into plastic deformation of the pipe that must be recovered by subsequent straightening processes during laying
Data Source
Figure 1
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Figure 3~5
AI summary
In a method of joining a structure (48) to a water-filled pipeline (16) aboard a reel-lay vessel (12), a trailing end portion (16A) of the pipeline is suspended upright on a reel-lay tower (10). Water is drained from the trailing end portion while being retained in an inclined portion (16C) of the pipeline extending from the tower to a reel (22) of the vessel, and in a spooled portion of the pipeline coiled on the reel. The structure is joined to a trailing end of the pipeline after inserting a pig (38) into the trailing end portion through the trailing end. Pumping additional water into a leading end of the pipeline on the reel propels the pig from the trailing end portion into a conduit (50) of the structure while flooding the trailing end portion. This expels air through a port of the structure that was trapped in the trailing end portion between the pig and the structure.