Subsea Grab System with Separated Driver Device
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Solution Overview
Problem
Existing subsea grab systems face challenges in stability on the seabed, dynamic load management, and exposure to debris when operating at deeper depths with water currents, particularly due to the weight and top-heavy design of the driver arrangement mounted on the grab device.
Innovation Solution
A subsea grab system design where the driver device is a separate entity, independently suspended and positioned using a propeller system, allowing the grab device to operate below it, with buoyancy floaters and a heave compensator to manage dynamic loads and prevent entanglement, and positioning the driver device at a constant height above the seabed to reduce weight and exposure to debris.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the driver arrangement is mounted on the grab device near the excavation process, then the grab device can be positioned and controlled at the seabed, but the weight of the driver arrangement increases the dynamic load on the hoisting arrangement
Solution Approach 1:
The system is divided into two independently suspended components: the grab device and the driver device. The driver device is separated from the grab device and suspended independently via a second hoisting arrangement, allowing the weight and positioning functions to be decoupled. This segmentation reduces the dynamic load on the grab device while maintaining full positioning capability through the separately controlled driver device.
2Ease of operation
If the driver arrangement is mounted on the grab device, then the grab device can be controlled remotely, but the driver arrangement is exposed to rising dirt and debris which can be harmful to the system
Solution Approach 1:
The driver device is extracted from the grab device and positioned separately above it. This spatial separation removes the driver device from the harmful environment of rising dirt and debris generated during excavation, while the grab device continues to be controlled remotely through the separated driver device via the hoisting arrangement.
3Ease of operation
If the driver arrangement is positioned at the top part of the grab device, then the grab device can be controlled, but the grab device becomes top-heavy and susceptible of falling over when positioned on the seabed
Solution Approach 1:
The control function is segmented from the grab device and placed in a separate driver device. This eliminates the top-heavy configuration by removing the heavy driver arrangement from the top of the grab device. The grab device can now be positioned on the seabed with its center of gravity properly distributed, while the separately suspended driver device provides control capability without compromising stability.
4Ease of operation
If a driver arrangement is added to the grab device for deep water positioning, then positioning capability is improved, but the device complexity increases considerably
Solution Approach 1:
The driver device serves multiple functions: it acts as a remote control station, a positioning platform, and a suspension point for the grab device. By making the driver device multi-functional, the system achieves enhanced positioning capability without proportionally increasing complexity, as a single device performs multiple roles rather than requiring separate components for each function.
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 system achieves stability on the seabed, reduces dynamic loads on the grab system and marine vessel, and minimizes exposure to debris, ensuring efficient operation and reduced risk of damage from rising dirt and debris during excavation.
Implementation Method 1
a driver device comprising a propeller system configured for driving and positioning the driver device in a first horizontal plane below the water surface
Implementation Method 2
the at least one longitudinal suspension element of the first hoisting arrangement is guided by at least one central opening of the driver device by passing of the at least one longitudinal suspension element through the central opening for guiding the first hoisting arrangement
Data Source
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AI summary
A subsea grab system (100) comprises a grab device (110); a first hoisting arrangement (120) for the grab device; a driver device (130) comprising a propeller system (132) for positioning the driver device in a first horizontal plane, the grab system being configured such that the grab device (110) is positioned below the driver device (130), and the driver device being configured for positioning the grab device (110) in a second horizontal plane by guiding of the first hoisting arrangement; and a second hoisting arrangement (140) for the driver device. The first and second hoisting arrangements (120, 140) are configured and arranged such that the grab device (110) and the driver device (130), during operation, are independently suspended from the marine vessel (10), and may comprise cables, chains (121) or wires (141) for suspending and hoisting the grab device (110).