TORREY CANYON, BOHLEN, AMOCO CADIZ, TANIO. ERIKA, PRESTIGE,… and many other names which resound in all memories. Humorists even spoke about vintages…

       The oil tankers shipwrecks close to our Brittany coasts, really moved the populations that were inevitably very much concerned : that occured close to them. Often - in a splendid surge of generosity - they gave their time free, might have put their health at risk, to erase in an immense ant work the wounds which “fuel oil” did to their beach or their area. Moreover, this public realized that no professional organization, no political official, no civil security structure had envisaged such catastrophes.

       Worse, from one time to the other, it seems that no lesson was learnt as one remained impotent, as for the first time, because it is still the bucket and shovel which remain the efficient solutions. Sometimes in fact, smartness solutions make prowesses: the 1978 “Brittany Canadairs flying boats” (you know, these farmers with their liquid manure tons who, at the time of the moors or forests fires, replace at a moment's notice the Canadairs when they are recalled in the south) and the 2002 Vendean trawls are the fact of two plain geographical entities more united in the effort than the legends would tell it!

       Such catastrophes cannot leave indifferent the media… or the reporters : even without really knowledge of what they talk about, they have to “spit paper”. Very seldom are those who have knowledge on the subject (even sometimes professional reporters!). “It is not serious” because the vast majority of their readers is very unaware of these questions. Unfortunately, standard “Homo Politicus”, who after all is no more than a man like all the others, repeat again the same antienne and encense the only technical solution which one can evoke: THE DOUBLE HULL.

       Here, it is won: within 20 years, all ships will be double hull built; you will see that I was right! They avoid to add : “and there will be no more oil slick”, because in their deep down, they must admit that they know nothing about it… And for those who know, they say very little… and their opinion is very seldom asked. This is why I want to thank Jean Pierre PAGE and Maritime Technical Association for asking me to bring the lights of the “mechanic for ships” which I am.

       I will start with my personal opinion in saying, like Mr. De La PALLICE :

“PRESTIGE” was a strong vessel because she reached the 26 years honourable age.        The fact of having sailed all over the seas of the globe for such a period without notable pip being known from her shows that she was built and probably well maintained … for some time. “PRESTIGE” broke because she was not any more strong enough (in the absence of collision style accident assumption, which is not completely impossible).        I did say “was”, because in this 2002 year end, one could doubt that between her mainden voyage and her wreckage all had been done to preserve the integrity of the noble ship she was. Before that, let us consider one moment my n°2 proposal : “PRESTIGE” broke because she was not any more rather strong enough. That very week, she was not the only one ship completely unsuitable for oceanic navigation. The same storm overcame other ships (being also fragile) but which have the characteristic to be quite as stable up as down, you understood that I want to talk about Road of Rum multihulls.

       I will stop my comparison there, because neither the choices nor the stakes are comparable!

       Let us leave my personal opinion there to look at the only one technical measure generated by the “politician”: the DOUBLE HULL, born from the U.S. decision (Oil Pollution Act) taken in 1990 following the EXXON VALDEZ disaster. Reading the newspapers, we could believe that it is the universal panacea! One wonders even why it was not invented earlier !

       I make a specifying point that my approach wants to be an “ingenuous” approach so as to possibly open the debate. Because I have competence neither in naval architecture, nor in ship building, or even in ship classification. I bring here my engineer competences related to a generally rather good knowledge about trading ships in general, because I have seen closely some several hundreds of them in some years of Naval Repair career.

       First of all, let us examine the problem which arises for the Naval Architect who is required to design an oil tanker. He has :

to define a ship able to contain and carry at a given speed a quantity of defined liquid cargo, to check that the “beam-ship” is able to resist the stresses which she will meet during her career: navigation (either loaded with her cargo, or light of cargo and thus ballasted), all loading and discharge situations, etc…

       The Naval Architect has computers and modern means of calculation for that. Let us note also that he will have to check that this beam resists to some number of other particular conditions (of which I do not know all the details). One of the limits of the system is the definition of these assumptions and I will tell you a personal anecdote on this subject :

I had been invited by one of my customers to come and meet him for a technical discussion in connection with what we had quoted for the installation of approximately 1500 brackets. These brackets (“soft brackets”) were intended to face the creation of very numerous cracks which developed at the smooth plating connection with the frames on several of their ships. They were recent ships (less than three years), “North Sea Shuttle Tankers” 135000 TDW double-hull built. Cracks analysis showed that it was fatigue cracks.        The Classification Society thus carried out fatigue behavior calculations of the concerned connections and the first results arrived during my visit. The addition of the envisaged 1500 brackets would not extend fatigue resistance more than 10 years, it was then necessary to assemble approximately 5000 brackets to reach about 50 years life expectancy. The loading assumption elsewhere than in a port calm water did not seem to have been under consideration for these ships loading in North sea, in dynamic positioning at about thirty meters from another structure (FPSO, platform, buoy,…) and sometimes under extreme conditions, had not been taken into account at all !

       The broad outlines of the ship’s beam organization definition have been often defined either coming from ships already built by the shipyard, or coming from new ideas of the shipyard or its Customer, intended for better answering to existing needs or to face new requirements. For example the transport of aggressive chemicals required either to paint the tanks or to make them with stainless steel (duplex): it was necessary to design tanks whose walls would be smooth, all the structure being off-set outside the tank. These ships were probably the first double hull tankers.

       Partial double hulls existed already on other ships types, for example the typical “OO” ships (ore-oil) or “OBO” (ore-bulk-oil) whose design answered a profitability preoccupation of the ship by conferring her a versatility implying some structure complexity. These ships are characterized by their solidity necessary for the transport of ore, and by the complexity of their cargo oil systems: pumps and cargo lines, inert gas system …

       The double hull ships (sometimes partial) are varied :

Bulk Carriers, Ore Carriers, OBO et OO Gas tankers LPG and LNG Product Tankers

       In the following comments, I will limit to the tankers case.

Traditional tanker evolution: the tank arrangement of a traditional tanker is organized in sections: symmetrical port and starboard side and central section. The longitudinal arrangement is often different between the central section and the side sections. the ballasts segregation required to specialize tanks (side) which will not any more contain oil, others containing ballasting water only in exceptional conditions. And at last, small sized tanks aft of the last section called “slops”. They are intended for the collection and decantation of tank washing water for tank cleaning and degasification before work. Just a word to stigmatize the bad use by reporters, then now by the public, of the word “to degas” allotted to any ship when dumping dirty water to the sea! Double hull disadvantages: Increase of weight. Increase of the ship’s size for the same quantity carried. Increase of “hydrocarbon” risk.        Indeed I do not know a ship's structure free from cracks. The more complex the structure, the more certain is the cracks development. Because of these cracks, the ballasts contamination by hydrocarbons is probable. In the closed structure of these ballasts we know by experience that the atmosphere cannot be uniform. The “gas free” condition of the ship (on her arrival in the shipyard or during work) is obtained only by sampling, and even effective ventilation cannot guarantee that there will not exist gas pockets. It is a major risk in naval repair. Increase of surface to be protected from corrosion, thus requiring a better application quality, as well as more extended inspections, Increase of surface to be inspected. Increase of access difficulties. Only the cargo section is planned to be double hull protected. No the engine room. Why?

On these drawings, 3 brackets are represented which I will call : traditional bracket “Soft Bracket” such as I know it since the middle of Nineties, and finally “Soft Nose Bracket”. I know it only since the beginning of last July. This evolution represents a only traditional phenomenon of the technological developments: any evolution reveals new problems. The double-hulls are new structures introducing new problems. The traditional connections have stress concentrations from which arose cracks. The “soft bracket” is a completely intelligent… but insufficient answer. We are currently modifying a great number of “soft brackets” by lengthening them and prolonging them by welding… and grinding this entire new end.

       If my memory is good, the main cause of the OLYMPIC BRAVERY shipwreck is a bad temporization adjustment of boiler water level. However the ship had two boilers…

       The AMOCO CADIZ shipwreck is due to the loss of ship’s steerage. Did one seek to generalize the two rudders principle on sensitive ships?

       About two years ago, a tanker in North Sea was victim of a contershaft rupture. The propeller shaft immediately moved back until pressing on the rudder, involving an important flooding. The crew made an exploit in plugging the leak by improvising a fortune stuffing box with a hawser, whereas they had water up to the waste. In case it was unsuccessful, the Captain was ready to order engine room evacuation. It is necessary to specify that the ship was a very recent “Shuttle tanker”, fitted with two propeller shafts, two rudders and two engine room compartments independent and isolable by watertight doors. Did someone thought one day about generalizing this principle of two independent engine rooms for every ship …

       The double hull is at the same time a technical and media answer :

Technical because it answers some requirements but leaves some other points aside Media because it is a very public concern.

       But it is completely clear that the shipwrecks are only the extreme examples of situations where one “passed not so far”. Before all the ships are “double hull”, all “simple hull” ones will continue to sail for many years under the same conditions as yesterday.

       It would appear more important to me :

to reinforce the application of existing rules to find a means of “Classification internationalizing”. It is clear that some Classification Societies are more laxists than others, that a same Classification Society does not observe everywhere its own regulations with the same rigor (or same flexibility?), that the States had a monitoring role which is not limited to the red tape but really technical. I think about the comparison between the Irish DOWRY and the French Maritime Affairs for example!

“PRESTIGE” was a strong vessel because she reached the 26 years honourable age.
“PRESTIGE” broke because she was not any more strong enough . Everything had not been done accordingly !
In which condition would be a “double hull” ship 26 years old?

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