Subsea Installation Using Pendulum Motion Damping
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Solution Overview
Problem
Subsea installation of large objects, such as templates and manifolds, is challenging due to the high costs of large vessels and the difficulty in controlling heavy objects in air, which translates to increased load capacity and risk of cable snapping during hoisting and lowering.
Innovation Solution
A method involving a vessel transporting an object to a submersible frame below the water surface, where the object is released to perform a pendulum motion until suspended, allowing for reduced load and motion damping, with the submersible frame's buoyancy and propulsion system facilitating precise positioning on the seabed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large vessels with cranes are used to hoist heavy objects from the deck into the water, then the objects can be transported and installed subsea, but the cost of vessels increases and the load capacity requirements increase
Solution Approach 1:
The object is connected to the submersible frame before release, with the frame pre-positioned at the target location. This preliminary positioning eliminates the need for heavy-lift vessels to precisely place the object, reducing vessel cost and load capacity requirements while ensuring reliable installation
Solution Approach 2:
A submersible frame acts as an intermediary between the object and the seabed installation location. The frame is towed to the target position and then used to suspend and position the object, replacing the need for expensive heavy-lift vessels with a simpler, cheaper towing operation
2Ease of operation
If heavy objects are controlled in air during hoisting, then the objects can be transported to the installation location, but the load capacity requirements increase and the risk of cable snapping increases
Solution Approach 1:
The patent converts the harmful effect of air resistance and cable tension during hoisting into a beneficial controlled pendulum motion in water. By releasing the object into water rather than lifting it through air, the system exploits water's natural damping properties to safely dissipate energy and reduce cable stress, eliminating the risk of cable snapping
Solution Approach 2:
The patent uses hydraulic principles by transitioning the object from air to water environment. Water provides natural buoyancy and drag forces that control the object's motion during deployment, replacing the need for high-strength hoisting cables with a lower-strength connection that operates safely in the aquatic environment
3Productivity
If the submersible frame is positioned near the vessel, then the object can be quickly transferred, but wave-induced stress on the frame increases
Solution Approach 1:
The patent separates the vessel and submersible frame in the vertical dimension (depth), with the frame positioned at a safe depth below wave action while the vessel remains at the surface. This vertical separation allows quick object transfer through water while protecting the frame from wave-induced stress
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 reduces dynamic loads and risks associated with air-based hoisting, avoids wave-induced stress on the submersed frame, and enables precise placement of heavy objects on the seabed with reduced operational costs and increased safety.
Implementation Method 1
releasing the object from the vessel such that the object becomes submerged and carries out a pendulum motion until the object is suspended from the submersible frame
Implementation Method 2
The buoyancy of the submersible frame may be adjusted to compensate for the weight of the object suspended below the frame
Implementation Method 3
The buoyancy of the submersible frame may be adjusted to compensate for the weight of the object suspended below the frame
Implementation Method 4
The vessel or the further vessel may be used for towing the submersible frame for positioning the object. The object may be moved by a winch provided on the submersible frame. The method may further comprise adjusting the position of the submersible frame with a propulsion system provided on the submersible frame
Implementation Method 5
The method may further comprise controlling the drag of the connection between the object and the submersible frame by attaching one or more drag objects to the connection
Data Source
AI summary
An assembly for installing an object under water at a desired location, including a vessel arranged to carry the object; a submersible frame; and a connection between the object and the submersible frame. In use the vessel is spatially separated from the submersible frame along the direction of the water surface. The object, the connection and the submersible frame are arranged such that, when releasing the object from the vessel, the object becomes submerged and carries out a pendulum motion until the object is suspended from the submersible frame.