Flexible Pipe Nested Sheaths Annular Test Space
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Solution Overview
Problem
Flexible fluid transport pipes used in deep water applications face issues with loss of tightness due to high pressure, leading to water penetration and gas permeation, which can cause mechanical strength degradation and pipe failure, and existing solutions like using resistant steels or increasing armor wire dimensions increase cost and weight.
Innovation Solution
Incorporating a second sealed intermediate sheath between the internal and outer sheaths to create an annular test space for verifying the integrity of the pipe, along with a pressure test to ensure tightness and a method for dynamic fatigue testing to simulate deep-sea conditions without requiring a hyperbaric chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If armor layers are made with very strong steels or increased dimensions of armor wires to prevent water penetration and gas permeation, then the mechanical strength and integrity of the pipe are improved, but the cost and weight of the pipeline increase
Solution Approach 1:
The patent implements a nested structure with an inner sealed intermediate sheath (22) containing the reinforcement layer, and an outer sealed intermediate sheath (26) containing the test space. These nested sheaths create multiple barriers against water penetration and gas permeation, providing enhanced protection without requiring increased armor wire dimensions or stronger steels.
Solution Approach 2:
The pipe structure is segmented into distinct functional layers: the pressure sheath (20), the inner sealed intermediate sheath (22) with reinforcement layer, the outer sealed intermediate sheath (26) with test space, and the outer sheath (24). This segmentation allows each layer to perform its specific function independently, providing reliable protection through distributed barriers rather than relying on a single heavy armor layer.
2Reliability
If armor layers are made with very strong steels or increased dimensions of armor wires to prevent water penetration and gas permeation, then the mechanical strength and integrity of the pipe are improved, but the cost of the pipeline increases
Solution Approach 1:
The nested sheath structure provides multiple sealing barriers using standard materials and construction techniques, eliminating the need for expensive high-strength steels or oversized armor wires. The reinforcement layer within the inner sheath and the test space in the outer sheath provide reliable protection at lower cost.
Solution Approach 2:
The sealed intermediate sheaths (22 and 26) act as intermediary protective layers between the internal and external environments. These intermediate barriers prevent direct exposure of the reinforcement layer to water and prevent gas diffusion, providing reliable protection through multiple intermediate seals rather than requiring expensive single-layer solutions.
3Reliability
If an intermediate liner is placed between the inner and outer liners to provide additional sealing, then the protection against water penetration is improved, but the device complexity increases
Solution Approach 1:
The patent employs a nested configuration where the inner sealed intermediate sheath (22) is contained within the outer sealed intermediate sheath (26). This nested arrangement provides dual sealing barriers in a compact, integrated structure that is easier to manufacture and install than alternative multi-layer configurations.
Solution Approach 2:
The invention adds the dimensional aspect of radial nesting, with sheaths arranged concentrically around the central passage. This radial dimensionality allows multiple sealing barriers to be implemented in a compact package, providing enhanced protection without significantly increasing the overall pipe diameter or structural complexity.
4Reliability
If dynamic fatigue testing is performed under high pressure to simulate deep-sea conditions, then the reliability assessment is improved, but the requirement for hyperbaric chambers increases cost and complexity
Solution Approach 1:
The outer sealed intermediate sheath (26) creates an annular test space (30) that can be pressurized independently to simulate deep-sea external pressure conditions. This self-contained test space allows the pipe to be tested for dynamic fatigue under high pressure using standard testing equipment, eliminating the need for expensive and complex hyperbaric chambers.
Solution Approach 2:
The testing function is segmented from the transport function by creating a separate annular test space (30) within the outer sealed intermediate sheath (26). This segmentation allows independent pressurization of the test space to simulate deep-sea conditions without requiring the entire pipe assembly to be placed in a hyperbaric chamber, simplifying the testing equipment requirements.
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 solution provides a cost-effective and weight-efficient way to ensure the long-term mechanical strength and integrity of flexible pipes under high pressure, allowing for dynamic testing without hyperbaric chambers, thus preventing pipe failure and ensuring reliable fluid transport.
Implementation Method 1
The annular test space can be pressurized with an internal fluid in order to verify the integrity of the first intermediate sheath
Implementation Method 2
Sometimes, leaks in the annular space outside the inner sheath can occur due to the very high pressure applied to the outer sheath
Implementation Method 3
Water penetration into the annular space between the outer and inner sheaths, combined with the permeation of diffused gases through the inner sheath
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a flexible pipe for transporting fluid, which includes: an inner polymer sheath (20) defining an inner passage (16) for flowing a fluid transported by the pipe; a first intermediate polymer sheath, arranged outside the inner sheath (20), the first intermediate sheath (22) and the inner sheath (20) defining therebetween a first annular space (28); at least one layer of inner reinforcements (34, 35), arranged inside the first annular space (28); at least one outer layer arranged outside the first intermediate sheath (22). The flexible pipe comprises a second intermediate polymer sheath (26), inserted between the first intermediate sheath (22) and the outer layer, the first intermediate sheath (22) and the second intermediate sheath (26) defining therebetween an annular test space (30) for testing the integrity of the first intermediate sheath (22).