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Use of cryogenic buoyancy systems for controlled removal of heavy objects from the seabed

Nicholls-Lee, R.F., Boyd, S.W. and Turnock, S.R. (2009) Use of cryogenic buoyancy systems for controlled removal of heavy objects from the seabed At ASME 28th International Conference on Ocean, Offshore and Arctic Engineering, OMAE 2009. 10 pp.

Record type: Conference or Workshop Item (Paper)

Abstract

The concept design of a lightweight cryogenic marine heavy lift buoyancy system has been investigated. The approach makes use of a novel cryogenic system for provision of buoyancy within the ocean environment. The objective is to be able to lift or lower large displacement objects under full remote control. The nature of subsea lifting and lowering operations requires a high degree of precise control for operational safety, reasons and to preserve the structural integrity of the load. The lift operation occurs in two phases: Development of lift to overcome seabed suction, and then rapid reduction of buoyancy to maintain a controlled ascent. Descent involves controlled release of the buoyancy. The proposed buoyancy system consists of a buoyancy chamber and an integral cryogenic gas generation unit. The application of an on-board gas generation unit allows the removal of the engineering challenges associated with use of compressors and the concomitant complex manifold of connecting umbilical pipe work. It provides for a fully remote system completely eliminating all risk associated with extensive physical surface to subsea connection throughout the entire lift operation. The opening stages of the project work include the development of a system that will operate efficiently and effectively to a depth of 350m. An initial general arrangement for the buoyancy system has been developed. A number of these systems involve considerable design and development, these include: structural design of the buoyancy chamber, mechanical systems to control and connection to the lift device, the cryogenic system itself and overall process control systems. As part of the design process for such an arrangement, numerical simulation of the complete system has been undertaken in order to develop mechanical, cryogenic and process control systems efficiently and effectively. This system simulation has been developed using Matlab Simulink. This paper considers the overall design concept and associated system development issues. These are illustrated through use of the time accurate simulation of alternative design configurations that confirm the viability of the concept. A main conclusion is that minimisation of the dry weight of the system is critical to cost-effective operation of the project.

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More information

Published date: 31 May 2009
Venue - Dates: ASME 28th International Conference on Ocean, Offshore and Arctic Engineering, OMAE 2009, 2009-05-31
Keywords: cryogenic, salvage, deep sea recovery, controlled
Organisations: Fluid Structure Interactions Group

Identifiers

Local EPrints ID: 67324
URI: http://eprints.soton.ac.uk/id/eprint/67324
PURE UUID: 17c5fd7e-3da2-49d3-bdf8-61271dfa705c
ORCID for S.R. Turnock: ORCID iD orcid.org/0000-0001-6288-0400

Catalogue record

Date deposited: 17 Aug 2009
Last modified: 19 Jul 2017 00:19

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Contributors

Author: R.F. Nicholls-Lee
Author: S.W. Boyd
Author: S.R. Turnock ORCID iD

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