Report issued on MOL Comfort Loss

Discussion in 'Class Societies' started by NavalSArtichoke, Sep 30, 2014.

  1. NavalSArtichoke
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    NavalSArtichoke Senior Member

    If anyone is interested, Class NK has just released its report investigating the loss of the container ship MOL Comfort, which broke in two in the Indian Ocean in June 2013, after which, both halves eventually sank.

    http://www.classnk.or.jp/hp/en/hp_news.aspx?id=1100&type=press_release&layout=1

    The website gCaptain had published some remarkable photos of the vessel before it sank, and these can be found here:

    http://gcaptain.com/mol-comfort-incident-photos/

    Here are some of the photos -

    The vessel still in one piece:

    [​IMG]

    The stern after the break up:

    [​IMG]

    The bow:

    [​IMG]

    These photos were taken from salvage tugs dispatched to tow the vessel to a safe harbor, but conditions apparently conspired against the salvage until the vessel sank.
     
  2. Ad Hoc
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    Ad Hoc Naval Architect

    Thanks, been waiting for this.
    It's a bit lame, suggesting "simple" buckling of the central panel caused by "simple" combination of loads. This is basic structural design and all scenarios should have been considered, and even requested for a Class approval.

    It'll be interesting what ICAS & ISSC say on the report too.
     
  3. powerabout
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    powerabout Senior Member

  4. NavalSArtichoke
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    NavalSArtichoke Senior Member

    Seems like a lot of Class Society trash talking going on between DNV-GL and Class NK. DNV is in effect saying to the box ship owners, "Don't believe what Class NK is telling you about your ships. We've got the better handle on what is happening." Yet, oddly, DNV apparently is keeping their analysis in-house, for the moment.

    All I have found on the web is a lot of PR talking points delivered to the shipping press by various DNV-GL executives. Have any of the DNV analyses been released to the public? I couldn't find any online... Any links to the actual DNV study would be appreciated.
     
  5. MikeJohns
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    MikeJohns Senior Member

    But they did point out that it's tricky designing ships (on page 33) a lot of people will be groaning reading this.....:)

    "it is difficult to assess the entire hull structure all at once because the hull structure is large and complicated, and also the hull is subjected to various types of loads such as wave and cargo loads"
     
  6. Ad Hoc
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    Ad Hoc Naval Architect

    That's because it is part of Japanese culture to misdirect and where possible place the responsibility/blame on others; they are never wrong (I'm not joking!!). Hence my comments above...lame and will be interesting to see what IACS, ISSC et al have to say on this too. Especially given the citation you note above :eek::p
     
  7. SukiSolo
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    SukiSolo Senior Member

    Is also part of Japanese culture to fall on sword?...;)

    Interesting that such a new ship built by a major name has suffered such a misfortune. Better still to fully understand what actually was the problem ie structural, build quality, previous damage ie grounding etc etc. The point is to avoid the same mistake if possible. This scale is way beyond my realm but one does have an appreciation of the size of the problem and the work required to resolve it.

    Yes I've looked through the report and the FEA etc but still seems to leave questions even for me. Maybe they'll blame the Loch Ness monster for scaping and resurfacing some miles from home....;)
     
  8. NavalSArtichoke
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    NavalSArtichoke Senior Member

    The Japanese are no different from other people, in that you want some other guy to fall on his sword first.

    The MOL Comfort was not the first box bote to suffer hull girder damage, but it is remarkable due to the fact that the hull girder failed completely at sea in relatively mild conditions (it's not like the vessel was sailing thru a typhoon or a cyclone when the casualty occurred). The loss of the ship was magnified because of the value of her cargo, which was insured for several times the value of the ship (reportedly, insurance claim totals are in the range of $400 million).

    Earlier, the MSC Napoli had suffered major cracking of the hull during a storm in the English Channel in 2007, which led to the vessel becoming a total loss after she was beached and eventually broke in two. The damage to the Napoli occurred approximately at the same location where the Comfort was damaged, i.e. in the region adjacent to where the cargo container holds meet the machinery spaces. It should be stressed that these two vessels, the Napoli and the Comfort, were built to different designs in different countries and were much different in size and container capacity.

    The UK MCA and DNV, the class society for the Napoli, eventually issued reports, based on forensic examination of the wreck, which detailed the specific structural failures which led to the cracking of the Napoli's hull. These reports were issued in 2008, well before the casualty which befell the Comfort. It's not clear why other operators of large container vessels did not read and heed the lessons of the Napoli, but needed another casualty in the MOL Comfort to emphasize the risk.
     
  9. SukiSolo
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    SukiSolo Senior Member

    Thanks NavalSArtichoke. However I would imagine the Confort was designed and was well into build, judging by that timescale. So it may have been difficult to re engineer or stress the hull model and stiffen/alter accordingly.

    There is a slightly different culture in Japanese society though, to us in the West. One example would be K******* motorcycles where the top engineers designed the engines and the juniors the frames. Result was very powerful machines which did not like corners. Eventually they figured all parts needed attention. Interestingly it was also based on their 'class' system as a heirachy. We have our own version, at least in the UK, but not the same. Whether such remnants of that remain in Japan I cannot say. My brother worked out in the far east for many years and certainly encountered very different scenarios to doing business in the West.

    There is also a great quote from the Formula 1 Renault boss from a few years back. 'We will not be satisfied until we have humiliated Honda on the track'. They did shortly afterwards.

    Key thing is not to be secretive about things and ensure life is safe, along with the vessel giving decent service life. The Societies are at the forefront of this good work.
     
  10. NavalSArtichoke
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    NavalSArtichoke Senior Member

    After the casualty to the MOL Comfort was publicized, MOL briefly removed her sisters from trade until their hull structures could be examined and strengthened accordingly. At least one vessel was in the final stages of construction when the Comfort went down, and her modifications were completed before delivery.

    http://gcaptain.com/hull-reinforcements-completed-on-mol-comfort-sister-vessels/

    MOL is also reportedly suing Mitsubishi Heavy Industries, the builders, for compensation of the cost of repairs to the surviving vessels. There may be other suits waiting in the wings as claims are made on the loss of cargo from the Comfort.

    http://gcaptain.com/mitsui-osk-lines-sues-shipbuilder-mol-comfort/

    The Comfort was rated to carry about 8000 TEUs. Maersk Lines is in the midst of a building program which will add 20 new vessels to its fleet by 2015, each of which is rated to carry more than 18,000 TEU. Other operators are planning to build or have completed vessels whose capacity falls somewhere between that of the Comfort and the new Maersk vessels. This is why it is urgent that the structural behavior of these newer, larger vessels be understood thoroughly, lest we do our shopping by going down to the shore and seeing what containers have washed up overnight. (This actually occurred on the south coast of England after the Napoli broke up. Containers filled with brand new motorcycles, appliances, etc. washed ashore, which the locals picked thru until the authorities put a stop to it.)
     
  11. SukiSolo
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    SukiSolo Senior Member

    Completely agree on trying to fully understand the newer (and in some cases, existing?) vessels. Be interesting to see if 'spring' periodicity from wave patterns etc affects some types of hull structure. Maybe combinations with engine frequency/revs, speed etc. My earlier point was the build date 07/08? of the Comfort overlaps with the Napoli report. The sister ships can hardly have inspired confidence unless of modified type.

    The TV and still images of people raiding the containers from the Napoli, brought to mind the old Cornish wreckers of yore. Some people drove literally hundreds of miles to the site....:)
     
  12. powerabout
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    powerabout Senior Member

    wonderful, the more computers involved in the building the less reliable guessagineering has become, how did we get here?
     
  13. NavalSArtichoke
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    NavalSArtichoke Senior Member

    I don't think you can put all the blame on the use of computers. Certainly, ships designed and built in the days before computers were used cracked, broke apart, and sank, sometimes with frightening regularity, especially after welding was introduced to ship construction.

    However, instead of hiding their eyes and hoping it was some random misfortune or a combination of improbable events, naval architects at that time aggressively investigated the problem, developed fixes for existing ships, and changed the designs of future ships to eliminate the most common sources of fractures. It helped in no small part that there was a war on at the time, so everyone was on-board the program to make sure that supply ships would not start disappearing at sea.

    I think the problem with the MOL Comfort, the MSC Napoli, and other vessels of this type lies with the complex structure of the hull and the rapid introduction of newer, high-strength steels into their construction.

    The two casualties seem similar in that both vessels experienced significant structural failure in the region adjacent to the machinery space and the container holds, a region where there is an abrupt structural transition. Such regions are well known for harboring areas of high stress concentration and other factors which can lead to the formation of cracks in the structure. If the hulls of the vessels are not closely inspected to ensure that the structure remains intact, then once a crack has started, there is little to arrest its growth, especially if the vessel is mal-loaded or enters heavy seas.

    The growing use of high-strength steel in container ship structures is driven primarily by the rapid growth in size and cargo capacity of these vessels. Being constructed without much in the way of a main deck, the hull girder must be strengthened in other areas to compensate for the large openings required to load containers. It is well known that very thick steel plating is more susceptible to cracking as vessels are periodically stressed by flexing at sea. In order to lighten the structure and to strengthen it, high strength steels are used in building these ships.

    Based on the damage which was reportedly observed in the Comfort's sisters after her loss, it appears that perhaps some structure in these vessels was too light to sustain the load imposed on it, and additional steel had to be added to reduce the stress. Whether this situation should have been recognized during the design of the vessels and corrected before construction began is something which can only be determined by a full investigation.

    Obviously, the Comfort and her sisters were reviewed and received class documents after completion. Are the class rules inadequate somehow when applied to these designs? This and other questions can only be answered after gathering the facts and analyzing what's going on.

    Still, the fact remains that it was known that at least one not-so-large container vessel had suffered a significant crack in a storm. It would seem that a prudent vessel owner, class society, or hull underwriter would have taken the initiative and set up monitoring of these vessels to ensure that no future damage of similar type and cause would occur, or, at least, could be caught before a vessel and cargo were lost.
     
  14. powerabout
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    powerabout Senior Member

    I would have thought that complex design only comes from using FEA as a tool and load the correct steel and you get an analysis.
    The next bit is the scary bit as someone then decides that that design passes or keeps working to remove as much steel as possible to meet some criteria?
     

  15. Ad Hoc
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    Ad Hoc Naval Architect

    Care to explain that one?...or are you referring to transitions of fracture?

    The main issue with using HTS is the fatigue values used. It seems Class in the past have used standardised fatigue based upon mild steel which has shown to be incorrect and Class rules are now making adjustments to account for HTS when used. Since HTS steels have a difference in their FAT curves.
     
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