Reassessment of the Marine Salvage Posture of the United States (1994) / Chapter Skim
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Appendix I: Salvage Tug Requirements
Appendix I: Salvage Tug Requirements
Pages 121-131
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From page 121... ...
While one might prefer to think that any size vessel could be towed in any weather with a large enough tug, this is simply not the case. The limiting factor is a function of the relative motions between the two vessels and the ability of the towline and towing winch to allow for that relative motion without breaking, while still providing sufficient towing force to keep the vessel moving or at least to maintain its position.
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From page 122... ...
Based on a range of typical sea states, the mean wave drift forces were estimated using OCMOTA,5 ship motion and wave force prediction program developed by the Maritime Research Institute of the Netherlands (MARIN) for the Oil Companies International Marine Forum (OCIMF)
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From page 123... ...
waves in conjunction with onshore winds is: East Coast Gulf Coast California Pacific NVV Alaska 0.30~o 0.05% 0.20~o 0.80% 1.40~o These numbers represent the percentage of time in certain coastal waters when one would anticipate that a rescue tow or holding operation of a loaded VECC would be beyond the capability of a single 7,000-BHP tug. In 197S, DNV published Towing Operations Guidelines and Recommendations for Barge Transportation.
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From page 124... ...
Even the largest oceangoing tugs cannot continue to tow in major storm conditions.
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From page 125... ...
Wave heights refer only to wind waves, and swells from distant or old storms ar nearly always superimposed on the wind-wave pattern. Practical Methods of Observing and Forecasting Ocean Waves, Pierson, Newuman, James, H.O.
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From page 126... ...
FIGURE T-3 U.S. Gulf Coast onshore wave height probability distribution.
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From page 127... ...
O 5 ~ ~ O _ 0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 WAVE HEIGHT (m) FIGURE T-5 Pacific Northwest onshore wave height probability distribution.
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From page 128... ...
O 10 ~ ~ _ -= _,~ 0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 WAVE HEIGHT (m) FIGURE T-6 Gulf of Alaska onshore wave height probability distribution.
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From page 129... ...
FIGURE I-S 80- to 280-MDWT tanker wind force.
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From page 130... ...
Estimated Tug BHP HP 31 45 64 100 109 3000 4500 6400 10100 1 1 300 Note: Loss of emdency is estimate to show effect of motions on effective tug power. FIGURE I-9 Tug power estimate required to hold SO-MDWT fully loaded tanker.
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From page 131... ...
FIGURE I-~l Tug power estimate required to hold 280-MDWT fully loaded VECC.
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