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Precis File
SHIP NAME: Prestige KEY: NUM. ENTRIES: 9
source LMIU
type D
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Listed in bad weather in 42 03 N 09 46 W 13 Nov 2002 Tugs on scene with lines connected Serious oil pollution Crew taken off Towed offshore 14-15 Nov Leaking oil again 18 Nov Broke in two in 42 15 N 12 08 W 19 Nov, both parts sank. Reported 27 Mar 2003 oil leak believed stopped


source CONSTANTINOU
type A
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At approximately 1510, local time, 13 November 2002, a substantial starboard list developed on the Bahamian registered ABS classed oil tanker Prestige. The list occurred in the region of Cape Finisterre, between 25 to 30 nautical miles off the coast of Galicia in northwest Spain, on a voyage that originated at St. Petersburg, Russia to the probable discharge port of Singapore. At the time of the incident, the oil tanker, with 27 crew members on board, was underway in heavy seas and high winds. The list, reported to be about 24 degrees, caused the cargo of fuel oil to force open some main-deck cleaning openings, enabling fuel oil to spill into the sea. Moreover, as a result of the list, the vessel lost main propulsion and began to drift.

Between 1600 and 1745, local time, a Spanish helicopter arrived to evacuate 24 members of the crew. The master, chief engineer, and chief mate stayed on board.

On 14 November, two tugs, the Rio De Vigo and the Sertosa 32 secured towlines to the Prestige. Spanish authorities refused to offer a Place of Refuge for Prestige. With the Prestige in a damaged condition, the tugs towed it out to sea into heavy weather. Over the next five days, the Prestige suffered additional structural damage while being towed in an undeclared location.

Finally, on 19 November about 0800, the Prestige broke in two and subsequently sank about 133 miles off the coast of Spain, six days after the initial listing incident.


source Bahamas Marine Authority
type D
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The initial problem started with a failure of of the ship's side plating in one of the starboard ballast tanks which was empty at the time. The tank rapidly filled with seawater causing the ship to list to about 25 degrees. The main engine stopped at about this time. The master took immediate action to reduce the list, but it was several hours before the list was reduced to 5 degrees. The large list combined with heavy rolling caused small amounts of cargo oil to be forced thru screw-down plates in the deck There was no damage to any of the cargo tanks at this stage. This state continued for several hours after the initial incident. However, the ship lay in such a position relative to the weather that the heavy waves continued pound [sic] the damaged area. Eventually, a further piece of side plating was torn away and as it broke loose it appears to have damaged the plating of one of the cargo tanks, which began to spill its cargo causing serious pollution.


source ABS Press release
type D
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link http://www.eagle.org/news/press/nov202002.html

[2009-05-20 this link is broken.] On the 13th November 2002, at approx 1500 local, motor tanker Prestige suffered a major structural failure and rapidly developed a list to starboard of about 25 degrees. At the time of the incident, the weather was very severe. The wind was estimated to be westerly Fource 10 with a very heavy swell. It is almost certain that the ship was struck by a very heavy sea in way of the number three starboard ballast tank, causing a section of ship side plating to break adrift and allowing water to enter a previously empty tank. The vessel transmitted a Mayday signal, which the local Marine Rescue Coordination Centre answered. At about this time, the ship's main engine stopped due to the list.

The vessel was a Category 1 vessel under MARPOL 13 G approved for either HBL as a crude oil tanker, or CBT with 30% side or bottom protection as a product tanker. Information provided by the operators shows the vessel was loaded in conformance with the CBT requirements at the time of the casualty. Last SS (SS #5) was in Guangzhou, China, May 2001. Two ABS surveyors with appropriate qualifications attended. The gauging firm used was Dimitros Thomas Marine Ltd. Major repairs were undertaken in the side ballast/cargo tanks, No 3 (PandS), and concentrated mostly on the transverse bhds and the frames at the upper levels within the tank. Accordingly the abm tanks were fully staged at Frames 61 and 71 and between FR65-70 respectively. Staging was also extended to various areas for the repair of shell and longitudinal bhd longitudinals. In particular, iwo of the side ballast/cargo tanks No2(aft) and 3, the shell plates were close up surveyed internally and externally examined, There was no area of concern noted on the shell plate. Thickness measurement results showed that the average wastage on the shell plate was less than 10 percent. No repair was considered necessary on the shell plate at the time. The starboard shell longitudinals were found below 10% wastage in side ballast.cargo tank No2 aft and the stbd shell longitudinals were found mostly between 10-15 pct in side ballast/cargo tanks No3(S) at time of survey. Total steel replaced is estimated at 362 tons. The repairs that were required were in accordance with those that could reasonably be expected on a vessel of this type at Fifth Special Survey. [This shows how low our expectations have become.] The cargo was 76,972 mt of heavy fuel oil (SG 0.99), typically used as bunker fuel. The cargo was distributed as per loading plan by which the No 2 aft (PandS) and no 3 (PandS) tanks were left empty. [gave 42% of max allowable moment] stability analysis indicated both No2S aft and No3S had to flood to give 25 degree list. BM was now at 125% allowable. after counterflooding, NO2P aft and No3P, BM was now at 163%.

[ The ABS site appears accurate as far as it goes. It has section and profile plans of the ship and a diagram of the three loading patterns: before damage, after damage, and after counterflooding. But if carefully ducks the issue of what really caused this hull failure. And the use of bending moment as a measure of stress is seriously misleading, given the change in list. See CTX entry below.]


source CEDRE
type L
volume 77000T
material
dead 0
link http://www.le-cedre.fr/en/spill/prestige/prestige.php


source ITOPF
type L
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link http://www.itopf.com/casehistories.html#prestige


source LINK
type L
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link http://www.xente.mundo-r.com/troncosco/prestige/p1.html

Excellent picture showing ship failing in sag. When the hull finally broke in two, sea conditions were not that bad. Other pictures at this site capture the outrage of the Galicians.


source ACOPS2003
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Traces oil coming shore on the Isle of Wight in late July 2003, and Ramsgate in August inter alia to the Prestige, apparently on the basis that lab analysis showed that the origin of this oil was the same. [Wording is a little ambiguous. Talks about lab samples, but not clear anybody had a sample of the Prestige cargo.]


source CTX
type D
volume 77000T
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dead 0
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Ship was carrying 77033 tons of HFO loaded in Ventspils enroute to Singapore via Gibraltar.

This is a near-repeat of the Erika, badly corroded, ballast tank, side plating failing in a heavy beam sea.

CTX has been told privately that it was the Master that made the decision to counterflood the port ballast tanks in order to reduce the list. Apparently, one reason he did this was that there was so much list that the cargo tanks were leaking out the tank lids. Presumably he thought that it he could stop this leakage, he might be allowed a port of refuge. Also, the main engine would not operate at this list.

However, this decision probably increased the stress on an already damaged hull; but not nearly as much as ABS implies. ABS correctly claims the bending moment went from 125% of allowable to 163%, implying the max stress increased by a similar amount. However, the reduction in list also reduced the the maximum distance to the neutral axis, effectively increasing the section modulus. As a rule of thumb, for a given bending moment, a 15 degree list will increase the maximum stress by about 15% (Principles of Naval Architecture, 2nd Ed, p 191). In other words, in the listed condition, the max stress was at least 20% higher than ABS implies. The counter-flooding increased the bending moment by about 30%; but also increased the effective section modulus by over 20%. The actual increase in max stress was of the order of 10%.

In short, it is not at all clear, as ABS implies, that the ship would not have sunk if the counter-flooding had not been done. The ship was already about 50% over design stress in the listed position for a non-corroded, intact hull. And this hull was badly corroded (in part because of lousy Class practice) and far from intact. Moreover, if he could get his engine back, the Captain could maneuver the ship to reduce wave stress.

This, like the Erika, was a MARPOL 13G(4) induced spill. Under the modified IMO rules introduced in 1992, when a pre-Marpol (non-segregated ballast) tanker turned 25, she had to either go hydrostatically balanced loading (HBL) or segregated ballast. Most owners opted to go segregated ballast. For one thing many charterers, such as BP, would not accept HBL ships. Usually this meant using cargo tanks that were not designed for seawater (uncoated) as ballast tanks. Unless these tanks were coated when the ship converted to segregated ballast, and few were (the 13G(4) regulation did not require it), rapid corrosion was inevitable.

The Prestige as built had only three segregated ballast tanks: the forepeak tank and 2A, port and starboard. Presumably [need confirmation] these three tanks were coated at build and fitted with anodes, which was the normal practice on pre-Marpol tankers. When [we need date] the ship converted to segregated ballast per IMO 13G(4), 3P and 3S were designated the new segregated ballast tanks. This gave the ship the required 30% side coverage. However, the new segregated ballast tanks were not coated, and thus rapid wastage was inevitable. (See also Castor.) It was this wastage that required 360 tons of new steel in 2001, despite class's very flexible rules regarding renewals. And it was this wastage that caused the 3P side plating and/or the 2A/3P corrugated bulkhead to fail as soon the weather got bad enough.

The post 13G(4) loading pattern with the 3P and S empty cut the loaded cargo capacity and put more buoyancy amidships than the ship originally required. It generated a rather mild overall stress pattern. But when the 3P flooded, the ship took a big list. Either this list or the or the fact that the original steel failure extended forward into 2A caused the original segregated ballast tank 2A also to flood. Now the ship, with a 25 degree list, was in trouble, even if the master had not counterflooded. For one thing the computed bending moment was above design levels, but more importantly ABS's use of overall bending moment with a totally assymetric loading pattern is specious, and ABS knows it. As argued above, the max stress in the listed condtion was not 25% above allowable but close to 50%. The standard procedure for computing stress levels from overall bending moment is only approximately accurate and then only if the ship is at near zero list. ABS should have used a finite element model to compute the damaged stress patterns.

Either way the ship needed refuge as quickly as possible. When that was denied, the loss of the ship becames inevitable.

But the primary cause of this loss was the conversion of the 3 wings to segregated ballast without proper steel protection, strongly abetted by the Classification Societies understanding surveying practices.