Motion suppression and heave compensator stroke reduction for floating production systems

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:449705

Brown, D T; Patel, M H; Witz, J A ^[1]

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1. University College London (United Kingdom). Dept. of Mechanical Engineering

This paper presents the design of a motion suppression and heave compensator stroke reduction system for floating production schemes. The system consists of tank spaces that are open to the sea at their base and enclose a column of air above the water surface. Butterfly valves above the tanks are used to either trap or release the air contained in the spaces. For a monohull the tanks are positioned along the vessel beams whilst for a semisubmersible, tension leg platform or deep draught floater the tanks are placed around the vessel columns. Results of comprehensive model tests performed on monohull floating production systems at the Ocean Wave Facility at HR Wallingford in West of Shetland wave conditions are presented and indicate significant motion reductions in waves, particularly in roll when using the system, because of additional damping provided by the tanks and detuning to minimize the effects of resonance. The system is also applied to vessels targeted for more moderate weather locations where rigid riser connections are being considered. This requires that relative motion between vessel and sea bed caused by waves, tides and product off-loading must be reduced to negligible levels. At the same time the influence of mean and slowly varying vessel horizontal motions on the risers together with riser pull-in effects must be minimized. By using the motion suppression system in conjunction with low pressure high volume compressors allows the vessel to be physically raised and lowered in the water to compensate partially for a number of the above effects. Consequently, heave compensators for the risers can primarily be used to cancel wave induced vertical motion, their required stroke being reduced by use of the air tank system. Similar technology is already in use allowing alterations in draught of a 44,000 tonne displacement crane vessel.

• OSTI ID: 449705
• Report Number(s): CONF-9606279--; ISBN 0-7918-1490-4
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
42 ENGINEERING
DAMPING
DESIGN
FLUID-STRUCTURE INTERACTIONS
MARINE RISERS
OFFSHORE DRILLING
OFFSHORE PLATFORMS
PRODUCTION
SHIPS
SHOCK ABSORBERS
TANKS