Ship Structure Committee Case Study - Prestige
Ship Structure Committee Case Study - Prestige
Ship Structure Committee Case Study - Prestige
This case study has been prepared by the Ship Structure Committee (SSC) as an educational tool to
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Date:
Summary:
Flooding in the ship’s starboard #2 aft and #3 wing tanks caused a 25 degree list, which was
counter-ballasted by flooding #2 aft port and #3 port ballast tanks. This resulted in an
overstressed hull girder which failed after 6 days of exposure to heavy seas, causing the ship to
break in two and sink.
Table of Contents:
• Vessel Particulars
• Background
• Detailed Description of Structural Failure
• End Result
• Acknowledgements
Vessel Particulars
LOA: 243.5 m
Breadth: 34.4 m
Depth: 18.7 m
Draft: 14.0 m
Gross Tonnage: 42,820
Deadweight: 81,589 tonnes
Design Speed: 15.4 knots
Builder: Hitachi Shipbuilding and Engineering Co. (Maizuru Works), Japan
Hull No.: 4437
Year Built: 1976
ABS ID No.: 7603948
IMO No.: 7372141
Flag: Bahamas
Port of Registry: Nassau
Registered Owner: Mare Shipping, Inc., a Liberia corporation
Manager: Universe Maritime Ltd, Greece
P&I Coverage: The London Steamship Owner’s Mutual Insurance Association
Vessel Type: Single-hull tanker; Category 1 vessel under MARPOL 13G requirements; at time
of incident, approved as CBT product tanker with 30 percent side protection
Hull Material: Mild steel, subject to IACS Enhanced survey program
Arrangement:
Background
With such significant list, the PRESTIGE lost propulsion and began to drift. Three hours after
the starboard tanks flooded, #2 and #3 port wing tanks were counter-flooded. This brought the
vessel to a list of three degrees to starboard.
After being subject to heavy wave pounding for several hours, a piece of the already-damaged
side plating broke loose, damaging the plating on a cargo tank as it did so. Cargo was spilled as
a result of this damage and, in fear of polluting their coast, Spanish authorities refused to allow
the PRESTIGE safe harbor, instead ordering that she be towed at least 120 miles off of the
Spanish coast. In hopes of finding calmer waters in order to salvage the cargo, the PRESTIGE
was towed south by her stern to minimize further damage from waves.
On the morning of November 19, 133 nautical miles off the coast of Spain in international
waters, the PRESTIGE broke in two and sank. Back to Table of Contents
Initial Damage
The cause of the initial damage to the PRESTIGE is not known, and as the wreck lies under
nearly two miles of water, it is not likely that it will be examined extensively, or that any
conclusion will be made with regard to the initial damage. ABS made extensive technical
analyses of the PRESTIGE after the incident, but the lack of physical evidence prohibited them
from reaching a definite conclusion. The vessel was properly loaded and the as-built hull
structure met the 1973 ABS Rule requirements as well as the 2003 ABS Rule and IACS Unified
Rule. Some as-built structural details failed the 2003 ABS requirements for fatigue, but ABS
maintains that this is not a probable cause of the hull failure, as the PRESTIGE operated in a
gentler environment than the criteria were developed for, and “most of the side longitudinals…
having insufficient fatigue life were renewed at the 4th and 5th Special Hull Surveys” (ABS 2003:
4).
In its intact state, the PRESTIGE was under the allowed values for still-water bending moment
and shear force. According to their technical analyses, ABS believes that “a weakened section in
the side shell or supporting framing in the vicinity of frame 71” caused the initial damage and
flooding (ABS 2003: i).
ABS considers lightering damage to be the most likely cause of the side shell weakening. For 17
months prior to the incident, the PRESTIGE was used in lightering service for vessels up to
280,000 DWT. According to the ABS analysis, with these lightering operations, “permanent
deformations of side longitudinal Nos. 32 to 34 and the transverse frames and transverse
bulkhead could have occurred in the vicinity of frame 71” (ABS 2003: 4). In fact, a sister ship of
the PRESTIGE sustained side shell damage from lightering in 1989.
Hull Break-up
The break-up of the hull can be attributed to the continuous wave impact and internal sloshing
the vessel incurred as it was towed out to sea. According to the calculations made by ABS, after
the vessel was counter-flooded, the still-water bending moment was 154 percent of the allowable
value and the shear force was 93 percent of the allowable value. The hull structure, even in its
counter-flooded condition, was capable of remaining intact, and did so for six days as it was
under tow. The additional dynamic wave loads, however, augmented the bending stress, and
once the deck plate reached its buckling strength, the structure broke in two.
End Result
While the cause of the initial damage to the PRESTIGE remains unknown, the event underscores
the need for meticulous inspections so that any damage, regardless the cause, may be repaired
before it becomes a serious threat to the vessel.
Spain, France and Portugal all denied PRESTIGE access to their harbors and shelter from heavy
seas, which would have greatly limited the amount of cargo spilled. As a result of their technical
analyses of the incident, ABS concludes that “the sustained dynamic wave loading for the period
while the PRESTIGE was under tow subsequent to the initial casualty was the direct cause of the
ultimate disintegration of the hull structure and subsequent sinking of the vessel” (ABS 2003: 6).
The PRESTIGE casualty brought to light the need for comprehensive regulations on providing
safe harbor to vessels in need.
Figure 7. Satellite image of PRESTIGE oil spill from November 17, 2002.
Figure 8. Satellite image of PRESTIGE oil slick on coast, November 18, 2002.
The ecological result of the PRESTIGE casualty was a massive 70,000 ton oil spill that
devastated the local fishing and tourism industries. Due to the toxic nature of the oil, it was
predicted to cause pollution in the area for ten years subsequent to the initial spill, and was
reported to be leaking twenty liters of oil per day from its location at the sea floor. Coating over
one hundred miles of Spanish and French coastline with toxic oil, the spill had an estimated
Acknowledgements
References:
[1] American Bureau of Shipping, PRESTIGE Casualty – Information Update No. 3. Electronic
document, http://www.eagle.org/news/press/nov202002.html.
[2] American Bureau of Shipping, Technical Analyses Related to the PRESTIGE Casualty on 13
November 2002. Electronic document,
http://www.eagle.org/news/press/prestige/Tech%20Analysis%20final.pdf.
[3] The Bahamas Maritime Authority, The Bahamas Maritime Authority moves ahead with its
PRESTIGE investigation. Press statement, January 29:
http://www.eagle.org/news/press/prestige/bma%20press%20statement.pdf,
[4] SMIT Salvage, Prestige News Updates 1 through 9. Electronic documents,
http://www.smit.com/sitefactor/page.asp?pageid=295.
[5] Vince, Gaia, Prestige oil spill far worse than thought. NewScientist.com news service,
August 27: http://www.newscientist.com/article/dn4100-prestige-oil-spill-far-worse-than-thought.html.
Image Credits:
[Intro] SMIT: http://www.smit.com/sitefactor/public/images/news/prestige7large.jpg.
[1] ABS: http://www.eagle.org/news/press/nov202002.html.
[2] ABS: http://www.eagle.org/news/press/nov202002.html.
[3] Environment News Service: http://www.ens-newswire.com/ens/mar2003/2003-03-27-02.asp.
Galician Regional Environmental Authority
[4] SMIT: http://www.smit.com/sitefactor/page.asp?pageid=295
[5] SMIT: http://www.smit.com/sitefactor/public/images/news/prestige9large.jpg
[6] SMIT: http://www.smit.com/sitefactor/public/images/news/prestige7large.jpg.
[7] CERSAT:
http://cersat.ifremer.fr/news/highlights/the_oil_spills_of_prestige_tanker_observed_from_spa
ce. ESA ESANHD7708D
[8] CERSAT: http://cersat.ifremer.fr/news/highlights/the_oil_spills_of_prestige_tanker_
observed_from_space. RADARSAT