Subsea Equipment Package Installation via Multi-Vessel Buoyancy Control
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Solution Overview
Problem
Large surface area and significant mass objects experience significant drag forces and resonance issues when submerged, leading to amplified static loads on supporting cables, which can exceed their strength, and existing technologies struggle to manage these forces effectively during lowering and recovery to the seafloor.
Innovation Solution
A multi-vessel method involving the attachment of cables to individual landing points on subsea equipment packages, adjusting buoyancy, and controlling cable tension and length to minimize resonance effects and dynamic load amplification, using a combination of active and passive motion compensation to ensure safe installation and recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single large vessel is used to lower and recover subsea equipment packages, then the equipment can be managed, but the drag forces and resonance effects cause amplified static loads on cables that can exceed their strength
Solution Approach 1:
The patent divides the equipment package into multiple smaller modules, each with its own buoyancy control. This segmentation reduces the drag force on each individual module and allows for distributed buoyancy management, preventing excessive cable loads during deployment and recovery operations.
Solution Approach 2:
The patent employs buoyancy modules that can be inflated or deflated to counterbalance the weight of equipment modules. By adjusting the buoyancy force dynamically, the system offsets gravitational and drag forces, reducing the static load on supporting cables during both deployment and recovery phases.
2Reliability
If the cable length is increased to accommodate vessel motion, then the system can handle surface vessel motion, but the cable length tunes the system's natural frequency to that of the supporting vessel motion, creating resonance
Solution Approach 1:
The patent uses dynamically adjustable buoyancy modules that can change their volume in real-time. This dynamic adjustment allows the system to modify its natural frequency response and avoid resonance conditions that would occur with fixed cable lengths, while still accommodating surface vessel motion.
Solution Approach 2:
The system changes physical parameters (buoyancy volume, cable tension) dynamically during deployment and recovery. By adjusting these parameters, the system can tune its natural frequency away from vessel motion frequencies, preventing resonance while maintaining stability.
3Reliability
If larger and stronger vessels are used to handle the equipment packages, then the equipment can be deployed and recovered safely, but the cost and complexity of the operation increases
Solution Approach 1:
By segmenting the equipment into modular units with individual buoyancy control, the system enables deployment from smaller, less expensive vessels. Each module can be independently managed, reducing the requirement for extremely large heavy-lift vessels while maintaining safe deployment and recovery operations.
Solution Approach 2:
The buoyancy modules are self-regulating, automatically adjusting their buoyancy force in response to depth and pressure changes. This self-service capability reduces the need for complex active control systems on the vessels, allowing smaller vessels to perform deployments that would otherwise require much larger, more complex ship systems.
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 method allows for the safe and efficient lowering and recovery of large surface area and significant mass objects to the seafloor by minimizing resonance effects and reducing cable tension requirements, thereby decreasing the strength and size of vessels needed, and enabling precise positioning and reusability of equipment.
Implementation Method 1
The buoyancy of the subsea equipment package is adjusted to sink the subsea equipment package
Implementation Method 2
the vessel(s), cable and submerged object forms a 'spring-mass-damper' system having a natural period that may be excited by the sea forcing motion of the surface vessels at the system's natural frequency. This creates a zone of resonance
Implementation Method 3
When large surface area objects are submerged to any depth, they experience large drag forces acting much like a massive sea anchor
Data Source
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AI summary
According to one or more embodiments disclosed herein is a method of transporting equipment between sea- surface and seafloor by providing a structure with a subsea equipment package mounted thereon. The structure is used for installation and recovery in a subsea environment by changing the buoyancy of the structure or ballasting the structure to effect a controlled sinking motion.