Pennant Line Pulling for Shallow-Water Structure Launch
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In shallow water, tugs face reduced bollard pull capacity due to limited under-keel clearance, leading to increased operational costs and time-consuming anchoring or pile installation methods for launching structures into the sea.
Innovation Solution
A method involving a pennant line with clump weights that frictionally engages the seabed between two tugs, allowing a near-shore tug to apply a tensile pulling force through a winch, with the far-shore tug providing additional resistance and thrust to enhance pulling capacity without the need for multiple tugs or anchors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a tug operates in shallow water to pull a structure into the sea, then the structure can be launched from a coastal yard, but the tug's bollard pull capacity is reduced due to limited under-keel clearance
Solution Approach 1:
A pennant line is introduced as an intermediary element between the tug and the structure. The pennant line extends from the tug's bow to the structure and engages with the seabed through friction, allowing the tug to pull the structure without requiring full bollard pull capacity in shallow water. This mediator transfers the pulling force through a different mechanism that is less constrained by water depth.
Solution Approach 2:
The pulling force is segmented into two components: a portion provided by the tug's propeller thrust and another portion provided by the frictional engagement of the pennant line with the seabed. This segmentation allows the system to overcome the limitation of reduced bollard pull by distributing the force requirement across multiple sources, one of which (seabed friction) is not constrained by under-keel clearance.
2Force
If multiple tugs are combined to increase bollard pull capacity in shallow water, then the pulling force is sufficient, but operational costs and capital asset tie-up increase significantly
Solution Approach 1:
The pennant line acts as a force-multiplying intermediary that allows a single tug to generate effective pulling forces comparable to multiple tugs. By utilizing the seabed as an anchor point through friction engagement, the system achieves force multiplication without requiring additional tug vessels, thereby maintaining operational efficiency while achieving sufficient pulling capacity.
3Force
If conventional anchoring methods are used to pull the structure, then the tug can generate sufficient pulling force, but the process becomes time-consuming due to anchor installation and removal
Solution Approach 1:
The invention extracts the anchoring function from the tug itself and transfers it to the seabed through the pennant line. Instead of the tug carrying and deploying anchors, the pennant line utilizes the seabed's natural friction to provide the anchoring effect. This eliminates the time-consuming anchor installation and removal operations while maintaining the necessary pulling force capability.
Solution Approach 2:
The seabed serves as a self-service anchoring system through the frictional engagement of the pennant line. The seabed automatically provides the necessary resistance without requiring active installation or removal operations. The system leverages the environmental feature (seabed friction) to perform the anchoring function, eliminating manual intervention and reducing time loss.
4Ease of operation
If the structure is pulled a long distance from the shore, then it can float clear of the seabed, but the pulling distance and time increase
Solution Approach 1:
The pennant line enables the tug to operate effectively closer to the shore by providing augmented pulling capacity through seabed friction. This allows the structure to be pulled a shorter distance before achieving sufficient speed and distance to float clear, reducing the overall launching distance and time while maintaining the necessary floating capability.
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 increases pulling capacity in shallow water efficiently, reducing operational costs and time by allowing quick repositioning of clump weights and minimizing the need for extensive anchoring or pile installation, while maintaining control over resistance forces.
Implementation Method 1
reacting that pulling force through a pennant line that extends from the first vessel to a second vessel and that frictionally engages seabed soil between the first and second vessels
Data Source
AI summary
A structure such as a pipeline bundle is pulled into or through shallow water, for example when launching the structure, by applying a tensile pulling force to the structure through rigging that extends to the structure from a winch of a first vessel. The pulling force is at least partially reacted through a pennant line that extends from the first vessel to a second vessel and that hangs between the first and second vessels to engage the seabed soil frictionally. The vessels may also self-propel to contribute their thrust to the pulling force. The pennant line includes a clump weight such as a bundle of chains that can be repositioned easily for additional pulls by being lifted between the vessels before being lowered to the seabed at a new location.