Flexible Joint Bonding Structure for Steel Catenary Risers
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Solution Overview
Problem
Flexible joints for steel catenary risers with elastomeric components face degradation from fluid exposure, require expensive and large molding equipment, and have inefficient molding parameters due to long and circuitous sprues, leading to suboptimal construction and high costs.
Innovation Solution
A flexible joint design comprising a housing, extension tube, compression bearing with a transition shim and flexible elements, and inner bonding material with a frustoconical profile, along with a method of molding and bonding that reduces equipment size and cost, using a stack of elastomeric elements and shims, and placing the compression bearing in a state of compression to enhance durability and structural strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional transfer molding process is used with long circuitous sprues, then complete bonding of large diameter housing can be achieved, but pressure drop increases significantly leading to suboptimal molding parameters
Solution Approach 1:
The flexible joint assembly is divided into multiple segments that are molded separately and then bonded together. The housing is segmented into sections that can be molded with optimized, shorter sprue systems, eliminating the need for long circuitous sprues required in conventional single-piece molding of large diameter housings.
Solution Approach 2:
Components are pre-molded as separate sections with optimized gating systems, then assembled and bonded in a preliminary assembly step before final curing. This allows each section to be molded with optimal molding parameters without the constraints of long sprue systems.
2Strength
If large diameter housing is molded in single piece, then structural integrity is maintained, but expensive specially sized transfer molding equipment is required
Solution Approach 1:
The large diameter housing is segmented into multiple smaller sections that can be molded using standard, less expensive molding equipment. These sections are then bonded together to form the complete housing, achieving the required structural integrity without needing specially sized expensive equipment.
Solution Approach 2:
Multiple housing sections are nested or joined together to form the complete large diameter housing structure. This allows standard equipment to produce components that, when assembled, achieve the dimensions and structural requirements of a single large molded piece.
3Productivity
If elastomeric components are exposed to fluids through central fluid passage, then fluid flow function is achieved, but elastomeric components degrade over time
Solution Approach 1:
The elastomeric bearing components are extracted from the direct fluid path by providing a separate central fluid passage through the housing that bypasses the elastomeric elements. Fluids flow through the housing passage rather than through or against the elastomeric components, preventing degradation while maintaining fluid flow functionality.
Solution Approach 2:
A metal housing with a central fluid passage acts as an intermediary, separating the fluid flow path from the elastomeric bearing components. The housing directs fluid flow while the elastomeric elements remain protected from direct fluid exposure, extending their service life.
4Productivity
If total assembly weight is excessive for single molding process, then complete assembly can be manufactured in one step, but specially designed and expensive presses are required
Solution Approach 1:
The total assembly is segmented into multiple components of appropriate weight and size that can be molded using standard presses. These components are then assembled through bonding operations, achieving complete assembly manufacturing without requiring specially designed expensive presses for single-step molding of the entire assembly.
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 flexible joints with a long service life despite fluid exposure and reduces construction costs by using smaller, less expensive equipment, ensuring effective bonding and structural integrity while allowing for cocking motions and fluid passage.
Implementation Method 1
inner bonding material is bonded to each of the extension tube and the transition shim of the compression bearing
Implementation Method 2
at least one flexible element bonded to the transition shim; stack of alternating elastomeric elements and shims
Data Source
AI summary
A flexible joint is provided. The flexible joint is for use in a steel catenary riser that includes a compression bearing (106) having a transition shim (120) and a plurality of alternating flexible elements (116) and shims (118) collectively stacked and bonded to a lower portion of the transition shim (120). The flexible joint also includes an inner bonding material (126) having a profile that is complementary to a profile of an extension tube (104), the inner bonding material (126) being disposed between the extension tube (104) and compression bearing (106) and configured to serve as a bonding mechanism between extension tube and compression bearing.