Frusto-Conical Elastomeric Bend Stiffener for Underwater Riser
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Solution Overview
Problem
Existing bend stiffeners for underwater elongate members, such as risers and cables, face challenges in controlling excessive bending and flexing, particularly at intermediate locations where lengths of these members are joined, due to their design complexity and the need for welding or complex steelwork.
Innovation Solution
A bend stiffener with a tubular rigid interface mount and a split ring clamp system that securely locks onto a rigid structure without the need for bolting or welding, using a compliant sleeve material like elastomers and a frusto-conical shape with thicker walls at the root, allowing for effective load transfer and reduced complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional flange and bolt systems are used to secure bend stiffeners to rigid structures, then strong mechanical locking is achieved, but device complexity and welding requirements increase
Solution Approach 1:
The patent employs a frusto-conical elastomeric sleeve as a flexible shell structure that provides both structural support and sealing functionality. The sleeve's varying wall thickness (thicker at the small end, thinner at the large end) creates inherent stiffness gradients that provide mechanical locking through friction and geometric interlocking, eliminating the need for complex flange and bolt assemblies while maintaining strong attachment to rigid structures
Solution Approach 2:
The invention extracts and eliminates the complex steelwork flange and bolt components from the traditional bend stiffener design. By using a monolithic elastomeric sleeve with integrated rigid interface mount, the patent removes the separate bolting system entirely, simplifying the device while maintaining attachment strength through the sleeve's geometric design and material properties
2Strength
If complex steelwork and welding are used in bend stiffener construction, then structural strength is ensured, but manufacturing complexity and production time increase
Solution Approach 1:
The patent utilizes composite construction by combining an elastomeric sleeve material with a rigid interface mount, creating a hybrid structure that leverages the advantages of both materials. The elastomeric portion provides flexibility, damping, and corrosion resistance, while the rigid interface mount provides structural strength for attachment. This composite approach eliminates welding requirements and simplifies manufacturing compared to traditional all-steel constructions
Solution Approach 2:
The invention changes the material parameters from traditional steel and bolt assemblies to elastomeric materials with specific durometer ratings and mechanical properties. The frusto-conical geometry with varying wall thickness creates parameter gradients that provide both flexibility and structural integrity, enabling manufacturing through molding processes rather than complex welding and assembly operations
3Strength
If thick-walled elastomeric sleeves are used at the root end to increase stiffness, then bend resistance is improved, but flexibility and weight increase
Solution Approach 1:
The patent applies local quality variation through the frusto-conical geometry of the elastomeric sleeve, where the wall thickness transitions from thick at the small end (root end) to thin at the large end (tip). This localized thickness variation provides high bend stiffness exactly where needed at the attachment point while maintaining flexibility and reducing weight in the portions of the sleeve that require movement and flexure
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 enhances the stiffness of elongate members at intermediate locations, reduces material costs, and simplifies the construction process by eliminating the need for complex steelwork and welding, while maintaining strong interlocking capabilities.
Implementation Method 1
The sleeve is made from a compliant yet resilient e.g. moulded material such as an elastomer, and is capable of some degree of flexure
Implementation Method 2
Due to its shape, i.e. its variation in wall thickness, it becomes less stiff from the route towards the tip. Thus, at the root end, i.e. the point of attachment to the supporting structure, the walls of the elastomeric sleeve are thickest and therefore the product is stiffest
Data Source
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AI summary
A bend stiffener for resisting excessive- bending of an elongate underwater member in a region where it meets a rigid structure, comprises: a sleeve (1) for receiving said elongate underwater member, said sleeve being capable of some degree of flexure; and a rigid interface mount (3) secured to said sleeve, said rigid interface mount being suitable for attachment to said rigid structure; wherein said rigid interface mount comprises one or more slots (4) or holes which are alignable with corresponding slots, holes or recesses on said rigid structure such that the rigid interface mount may be locked to the rigid structure by locking means (2), said locking means comprising projection(s) through the slots or holes of the rigid interface mount into the slots, holes or recesses of the rigid structure. The bend stiffener is particular suited to mid-line applications, amongst other applications.