Subsea Riser Installation Using Double-Catenary Clump Weight Control
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Solution Overview
Problem
The conventional installation method for wave-configuration subsea risers requires an additional support vessel to handle clump weights, leading to increased operational costs, safety risks, and prolonged installation times due to the need for complex vessel maneuvers and limited sea state compatibility.
Innovation Solution
A method involving a clump weight device suspended in a double catenary shape, connected to a winch or crane on the installation vessel, allowing continuous control and adjustment of the weight load applied to the riser, eliminating the need for a support vessel and enabling installation in higher sea states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional installation method using an additional support vessel is used to handle clump weights, then the riser can be installed with proper hogbend configuration, but the operational costs increase, safety risks increase, and installation time is prolonged
Solution Approach 1:
The patent combines the functions of the installation vessel and support vessel into a single installation vessel. The installation vessel is equipped with both a crane for handling the clump weight and a winch for controlling the riser, eliminating the need for a separate support vessel. This merging of functions reduces operational costs, simplifies the installation system, and maintains installation reliability.
Solution Approach 2:
The installation vessel is designed with multi-functionality to perform both the original installation tasks and the additional clump weight handling operations. The vessel's crane and winch system can simultaneously or sequentially manage the riser deployment and clump weight installation, making the single vessel universally capable of performing multiple critical functions previously requiring two separate vessels.
2Manufacturing precision
If a conventional installation method with support vessel maneuvers is used, then the clump weight can be properly positioned, but the installation time is prolonged due to complex vessel maneuvers and limited sea state compatibility
Solution Approach 1:
The patent replaces the complex mechanical coordination between two vessels with a simplified single-vessel system using controlled winch and crane operations. The winch system provides precise mechanical control over the riser and clump weight positioning, substituting the need for coordinated maneuvers between multiple vessels and improving installation speed while maintaining positioning precision.
Solution Approach 2:
The installation system employs dynamic control through the winch and crane operations, allowing real-time adjustment of the clump weight positioning during installation. The system can adapt to changing sea conditions by dynamically adjusting the positioning operations, maintaining precision while improving productivity compared to static multi-vessel coordination.
3Ease of manufacture
If an additional support vessel is deployed for clump weight handling, then the installation can be completed, but the operational costs and safety risks increase
Solution Approach 1:
The patent extracts the support vessel function from the installation system, consolidating all necessary functions into the installation vessel itself. The installation vessel's existing crane and winch capabilities are utilized to perform the clump weight handling operations that previously required a separate support vessel, thereby reducing the number of vessels required while maintaining installation feasibility.
4Productivity
If conventional installation procedures are followed, then the riser installation can be completed, but the compressive loads on the riser increase and sea state limitations apply
Solution Approach 1:
The patent applies preliminary action by installing the clump weight at the appropriate location on the riser before final deployment. This pre-positioning of the clump weight creates the intended hogbend configuration that reduces compressive loads on the riser during installation and operation, allowing the installation to proceed while maintaining lower stress levels on the riser structure.
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 approach reduces installation time and costs, minimizes compressive loads on the riser, and allows for safer operations by eliminating the need for additional vessels and temporary anchorage, while enabling installation in a wider range of sea conditions.
Implementation Method 1
suspending an elongate clump weight in a catenary shape comprising first and second limbs extending upwardly from a conjoining bottom portion
Implementation Method 2
Buoyancy is added by attaching a series of buoyancy modules along a substantial length of the riser to modify the curvature of the riser and hence to define the shape, size and position of the hogbend
Data Source
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AI summary
A method of installing a wave-configuration subsea riser of unbonded flexible pipe comprises lowering the riser progressively into the sea from an installation vessel while suspending an elongate clump weight in a catenary shape that comprises first and 5 second limbs extending upwardly from a conjoining bottom portion. An upper end of the first limb, at a distal end of the clump weight, is attached to the riser and an upper end of the second limb, at a proximal end of the clump weight, is suspended from a winch or crane of the vessel. While lowering the riser from the vessel, the weight load applied to the riser by the clump weight is controlled by adjusting the relative lengths of the first 0 and second limbs of the clump weight.