Bourbon Dolphin capsizes

I found some more articles:

Olympic Hercules faced similar problems as Bourbon Dolphin, hearing told

A slacker wire could have saved Bourbon Dolphin / Bourbon Dolphin wrong vessel for the job (scroll down)

Regards
Johannpeter

 

Sean Dickson's photograph of the Bourbon
Dolphin just 35 minutes before she capsized.

 

Interesting photo smartbight. Sea doesn't seem to have been a big deal.

Johanpeter:
Let me quote here the text of the most interesting article at Shetland Today you link to, for easier reading and longer lasting here, as links may become inoperative with time.


THE BOURBON DOLPHIN could have been saved if the towmaster on the Transocean Rather had helped by paying out a few hundred meters of cable.

That was the opinion of Grim Are Bergtun of the Olympic Hercules when the hearing resumed in Ålesund on Tuesday.

Olympic Hercules had the task of setting the diagonally opposite anchor to that of the Bourbon Dolphin's job when it overturned.
This is the opinion of Mr Bergtun who was in a situation which was similar to that in which his colleague on the Bourbon Dolphin strove with shortly before the ship went over. Wind and tide forced the ship off course, and although he used maximum thrust he could not get the ship into the correct position for dropping the anchor.

The anchor which the Olympic Hercules worked with when the problem arose lay in exactly the opposite direction of the anchor which the Bourbon Dolphin was to lay when it capsized. Wind and tide were coming from just about 90 (degrees) from the side.

These were the problems Mr Bergtun was confronted with when considering the situation of the Bourbon Dolphin some hours later. While the Bourbon Dolphin could see to port at its anchor chain, the port list and drift to starboard, the Olympic Hercules turned suddenly to starboard at the same time as it drove helplessly to port.
At one time the ship was 750 metres from the position where the anchor should be laid.

Mr Bergtun agrees with the towmaster that the problem would have been solved if the rig had paid out 200-300m. cable so that the ship got some slack to work with. As soon as the ship moved Mr Bergtun turned turned the wheel slightly to starboard and used the speed forward through the sea to get into the correct position to lay the anchor. When the problem arose on the Bourbon Dolphin some hours later, the same solution was suggested, but the answer from the rig had been “No”.

At the same time the towmaster stressed how important it was that the Bourbon Dolphin did not drift over anchor number three. He advised the captain to lower the inner starboard rope pin to make it easier to manoeuvre. Seconds later the ship turned over.

To a direct question from the commission if he believed the Bourbon Dolphin could have solved its problems by making the same manoeuvre which he himself had made, Mr Bergtun answered “Yes, my impression was that the rig only wished that the Bourbon Dolphin would get to a safe distance from anchor number three and postpone the whole operation.

"What the skipper of the Olympic Hercules (said) made sense. It solved the problems. It is, to put it mildly, a pity that the Bourbon Dolphin did not get the same chance."

After hearing Bergtun`s explanation Administration Director of Bourbon Offshore, Trond Myklebust said: “I do not understand why the rig said no”.

The captain of the Olympic Hercules could also throw some light on another mystery – the reason why the status of the Bourbon Dolphin was changed from a secondary to a main position.

When the work of the Transocean Rather began, it was intended that five anchorholding ships should do the work, however two of these did not arrive at the stated time.

After the Bourbon Dolphin had assisted the Olympic Hercules to take up the first two anchors these two ships arrived, and because the chain boxes of the Olympic Hercules were full, these two had to do the job between them. This had happened at the first of the month which meant that the Bourbon Dolphin had been used as a main ship for almost two weeks before the accident, or at least part of this time.

“The picture is now a little clearer of how the Bourbon Dolphin came to be in the position of a main ship, but I shall not comment on this side now because I do not know the background reasons and judgements which led to it all” said Mr Myklebust. He said: "To put it mildly, it is such a pity that the Bourbon Dolphin did not have the same chance.”

Further public hearings into the capsizing of the Bourbon Dolphin are not expected until the end of August.

 

What struck me about this report was that I recalled Olympic Hercules as being a larger, more powerful vessel than Bourbon Dolphin. I checked, and it is: http://www.olympic.no/default.asp?menu=11

Olympic Hercules is longer, with a greater beam, 65% more power, 25% greater winch pull, 42% greater bollard pull, and she ran into similar problems earlier in the day.

Ultimately, I am certain the board will find many contributing factors. Regardless of the other decisions made that day, however, one element of the disaster is a fact: Bourbon Dolphin was attempting the same job a larger, far more powerful vessel had serious problems with a few hours earlier.

 

Yes indeed, Charmc. It looks as if new procedures, ideas and tackle will have to be developed to negate the risk elements that are obviously present with the high loads and tensions involved.
When you think of it, The Highland Valor was expected to hold at least half the weight of this chain on a hook while the Dolphin attached the anchor to the end. There was still the problem of getting to the anchor position.

 

Here is another question that I am hoping some of you who are more knowledgeable in vessel design could answer:
I have been pondering the many things that went wrong, when it occurred to me that there is a potentially serious stability factor that has not been really considered in anchor vessel designs. It is so commonplace that I really didn't even think about it until just a few days ago. My question is this:
What, if any, tests have been done on anchor vessels to see how they will react if they are at maximum bollard pull with a maximum load at the winch and loose power? For example, If I am on my anchor handler and we are getting ready to put an anchor on bottom it is quite common to pay out the anchor until it is 1.2 X water depth - this usually has to take place with the vessel at reduced power to prevent overloading the winch capacity. When the wire is all paid out we will then apply maximum bollard pull ("put them in the corners") and then go until the vessel stops making forward progress. At this point my question is what happens if a vessel goes to zero power. I know that on my vessel it shoots astern and doesn't ship much water on deck (if calm). The 'sister ship' (actually 16' less of a LOA) will submerge the stern and put a tremendous amount of water on deck and into the winch room.
How many anchor handlers would be able to survive a sudden drop from 100 percent bollard pull to 0? I know of no tests regarding this, but I am not in the design community. I do know that the vessel I am on has been pulled backwards at 10.2 knots while setting an anchor - so this is a major concern if the vessel starts to submerge the stern. I can imagine what would happen if a vessel submerged the entire cargo deck - especially if there are open hatches, etc.
What are the feelings that this may have been a major factor in the BD? Do you think it would be possible to bury the port quarter and trip the vessel in this manner?

It would be interesting to do a tank test with a model of the BD to see how it would react to a sudden loss of propulsion. I am also curious how this could affect other AHTS designs.

I should also mention that during the typical anchor handling operations we can feel the vessel roll markedly slower when we are skating astern after reducing power - that would seem to be a reduction of stability there.

--Capt. Chuck

 

I don't have the expertise to give a qualified answer. I do have the operating experience to know that that is one hell of a perceptive question.

 

Chuck,
Something here about water on deck.
There is something about going backwards but I still have to find where I put it. I'll search for it later.
Cheers.

 

Charlie, Chuck, as a 'mere' ex mate I back you completely on this one! One Hell of a good question! We've all experienced it but has it been passed on (probably!) and the reaction was?? I'd hazard a guess but won't - probably the same conclusion you people have come to! But now something maybe has now happened that could relate to this! MMMMmmmmmmm! not holding my breath as to the outcome tho'

 

Thank you for the information Guillermo! I have to admit that the mathematics are somewhat over hy head - I can pick up on the basic concept. With the water on deck I can easily understand why there is a reduction of stability.
The going backwards is the stability question that baffles me. I can feel the vessel rolling slower, but I cannot see how or why there would be a reduction of stability just by going backwards. I was wondering if it was due to the sudden reduction of force being applied downward off the stern of the vessel on the anchor system.
Once again, I wish I would have paid a little more attention during advanced mathematics.

Thanks for the words of encouragement walrus! It is amazing how many people I work with don't see this as even a valid question -something along the lines of "if this were important they would have already addressed it."

I've got to get back to flogging the crew. I'll try and check in later.
-Chuck

 

Chuck,

The paper Guillermo found demonstrates just how perceptive your question is.

Your comment about the attitude that some things don't need to be researched because "If it was important someone would have addressed it already ..." is downright scary. Yet, thinking back on my own experiences, not so rare.

 

I have found nothing yet on this most interesting subject. I thought I had something, but it was a different thing. I have to do more searching around.
An explanation to the slower rolling you mention could be the effect of some dynamyc lift at the flat stern sections when going backwards, not a decrease in stability. But I'm not sure. Have to study it.
Cheers.

 

If the deck is submerged you lose waterplane, hence you lose stability.

However you are being influenced by a force directly astern, so the controlling factor is now the KM [l], not KM [t].

 

Is there a way to post an excel workbook on this forum? I have the (somewhat primitive) stability program that I made for this vessel and thought that it might be something that others might find interesting to play with. I just entered all of the data from the stability booklet (each tank is a separate worksheet) and used excel formulas to work out the necessary calculations. Feel like a caveman trying to light a fire in many respects.

 

Chuck,
just upload the excel file like an attachement, as it if were a photo.