High Pressure Pipe Coupling Using Capstan Effect
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Solution Overview
Problem
High pressure pipes used for transporting aggressive fluids like crude oil and gas face corrosion and mechanical challenges due to internal pressures, with existing coupling constructions not adequately addressing the need for enhanced resistance and force transfer.
Innovation Solution
A high pressure pipe coupling construction utilizing a non-metallic inner sleeve for sealing and a metallic outer sleeve with a force transfer fitting, where the capstan effect provides a high holding force through the outer sleeve, while the inner sleeve primarily serves as a seal, minimizing its role in axial force transfer and allowing the outer sleeve to handle tensile forces with its higher modulus of elasticity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metal outer sleeve is used for mechanical connection and force transfer, then the holding force and mechanical strength are improved through the capstan effect, but the resistance to aggressive fluids deteriorates due to metal corrosion
Solution Approach 1:
The coupling is divided into two distinct functional parts: a non-metallic inner sleeve that provides corrosion resistance and seals the pipe end, and a metallic outer sleeve that provides mechanical strength and force transfer through the capstan effect. This segmentation allows each component to optimize its specific function without compromise.
Solution Approach 2:
The non-metallic inner sleeve acts as an intermediary between the aggressive fluid environment and the metal outer sleeve, protecting the metal from corrosion while allowing the metal to perform its mechanical function. The inner sleeve mediates the interaction between the fluid and the coupling system.
2Strength
If the inner sleeve is made metallic to provide structural support, then the mechanical strength is improved, but the sealing performance deteriorates due to potential corrosion and leakage
Solution Approach 1:
The coupling is divided into two distinct functional parts: a non-metallic inner sleeve that provides corrosion resistance and seals the pipe end, and a metallic outer sleeve that provides mechanical strength and force transfer through the capstan effect. This segmentation allows each component to optimize its specific function without compromise.
3Object-affected harmful factors
If both inner and outer sleeves are made non-metallic to resist corrosion, then the corrosion resistance is improved, but the holding force deteriorates due to insufficient mechanical strength
Solution Approach 1:
The coupling is divided into two distinct functional parts: a non-metallic inner sleeve that provides corrosion resistance and seals the pipe end, and a metallic outer sleeve that provides mechanical strength and force transfer through the capstan effect. This segmentation allows each component to optimize its specific function without compromise.
Solution Approach 2:
The coupling system uses a composite structure combining non-metallic and metallic materials, each selected for their specific properties. The non-metallic inner sleeve resists corrosion while the metallic outer sleeve provides the necessary mechanical strength for high-pressure applications.
4Reliability
If the inner sleeve is extended to provide sealing along the pipe end, then the sealing performance is improved, but the axial force transfer deteriorates as the inner sleeve interferes with the capstan effect
Solution Approach 1:
The inner sleeve is designed with localized sealing features (such as sealing rings or grooves) at specific positions where sealing is needed, rather than requiring the entire inner sleeve to be extended. This allows sealing performance to be improved without the inner sleeve interfering with the capstan effect in the outer sleeve.
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 design significantly enhances resistance to aggressive fluids and internal pressures by leveraging the capstan effect for high holding forces, with the inner sleeve ensuring sealing without contributing to axial force transfer, thus maintaining pipe integrity and preventing damage from pressure changes.
Implementation Method 1
The capstan effect results from the helical path of the fibers or threads within the outer sleeve. This provides a so-called encirclement of the fibers or threads within the outer sleeve. The ends of the fibers are held against sliding or slipping displacements within the pipe wall material.
Implementation Method 2
the fibers or threads develop increasing friction forces with respect to the inner surface of the outer sleeve, comparable to the friction forces which develop in a cable which is slung around a capstan
Data Source
AI summary
A high pressure pipe coupling construction includes at least one high pressure pipe (2) as well as a coupling (22) connected to the pipe (2). The pipe consists a reinforcement layer (4) of helically arranged fibers (6, 7) and the coupling (22) consists an inner sleeve (23) sealed with respect to the inner surface of the pipe and at least one metal outer sleeve (9). The metal outer sleeve (9) has an overlapping outer sleeve part (29) overlapping the inner sleeve (23) in axial direction and a protruding outer sleeve part (25) protruding in axial direction with respect to the inner sleeve (23), which overlapping outer sleeve part (29) and protruding outer sleeve part (25) are connected to the outer surface of the pipe (2). The inner sleeve (23) consists of a plastic material; at the location of overlap between the inner sleeve (23) and the pipe (2), the maximum outer diameter of the inner sleeve (23) is smaller than or equal to the minimum inner diameter of the pipe (2).