Unbonded Flexible Pipe Support Layer for Deep-Water Installation
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Solution Overview
Problem
Unbonded flexible pipes used for offshore fluid transportation face challenges during installation, particularly in deep waters, where high tensile forces and low friction coefficients between layers can lead to pipe damage and ovalization, increasing the risk of crushing and loss of deep-water crushing capacity.
Innovation Solution
Incorporating a thermoplastic vulcanizate (TPV) support layer with a winding angle of at least 80 degrees between the tensile armor layers to enhance frictional force transfer and distribute compression forces, reducing the need for high caterpillar squeezing pressure and minimizing the risk of pipe damage during installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If high caterpillar squeezing pressure is applied to counter tensile forces during installation, then the pipe can be controlled during laying, but the risk of pipe damage and ovalization increases
Solution Approach 1:
The patent introduces an intermediary friction mechanism between pipe layers to transfer tensile forces from the external sheath to the tensile armor without requiring high caterpillar squeezing pressure. The friction between layers acts as a mediator that distributes forces internally, reducing the need for external compression and thereby lowering the risk of pipe damage and ovalization during installation.
2Device complexity
If the friction coefficient between pipe layers is low, then the pipe structure remains simple, but the tensile force transfer from the external sheath to the tensile armor is insufficient
Solution Approach 1:
The patent changes the friction parameter between pipe layers by specifying minimum friction coefficients (e.g., μ ≥ 0.3 between external sheath and tensile armor, μ ≥ 0.2 between intermediate layers). This parameter change ensures sufficient tensile force transfer capability while maintaining the unbonded flexible pipe structure without adding complex bonding mechanisms or additional structural elements.
3Productivity
If the pipe is subjected to high tensile forces during installation, then the pipe can be laid in deep waters, but the risk of crushing and loss of deep-water crushing capacity increases
Solution Approach 1:
The patent applies preliminary action by ensuring sufficient friction between layers is established before the pipe is subjected to high tensile forces during installation. The friction coefficients are designed to be adequate from the outset, creating a pre-established force transfer mechanism that protects the pipe structure during the critical installation phase in deep waters, preventing crushing and maintaining deep-water crushing capacity.
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
The TPV support layer increases the pipe's resistance to damage and ovalization, ensuring reliable internal friction and reducing the risk of slip between layers, thereby lowering the risk of pipe damage during installation and maintaining flexibility.
Implementation Method 1
the friction has to be above a certain threshold, both between the shoes of the caterpillar and the pipe surface and between all internal pipe layers separating the tensile armor of the pipe from the pipe surface
Implementation Method 2
distribute compression forces, reducing the need for high caterpillar squeezing pressure
Data Source
AI summary
An unbonded flexible pipe for offshore fluid transportation is disclosed. The pipe includes from inside and outwards a sealing sheath, a pressure armor layer, at least one tensile armor layer, at least one support layer and an extruded external protective polymer sheath. The at least one support layer includes at least one support strip which is helically wound with a winding angle α of at least about 80 degrees to the longitudinal center axis to provide strip windings along the length of the pipe and the at least one support strip includes a thermoplastic vulcanizate (TPV).