[Johann Mahne]

Latest news:

The stricken vessel Rena is being closely monitored overnight while oil spill response teams and salvors remain ready to respond if the ship deteriorates in forecast bad weather over the next 24 hours.

Maritime New Zealand (MNZ) Salvage Unit Manager Bruce Anderson said a maximum sea state of about 5 metres was predicted overnight, which would cause further stress on the already damaged hull.

He said the conditions were similar to those experienced around 11 October when the hull sustained significant damage and a release of around 350 tonnes of oil.

Salvage operations were suspended yesterday due to the bad weather, and salvors had sealed the tanks to minimise the potential for further oil leaking from the ship. Additional sensors had been placed on the hull to monitor the vessel's movement.

[CliffordK]

There is a discussion that if the ship breaks up, they want to attempt to tow the aft section into shallower water.

Could one get a semi-submersible low enough  to snag the part?
Floating drydock?




It appears as if there is a limit of the depth most of these machines are designed to operate at, so it might prove difficult.  Perhaps one needs to design a fully submersible salvage drydock system.

[CliffordK]

I'm seeing notes that they still have 300 - 400 tons of oil onboard the Rena.  It seems like they've been stuck at that level for nearly a week now.  Access to the last tank is apparently difficult.  They are trying to float the oil out of the tank now.

The decision was to wait on offloading the containers until the oil is emptied, presumably due to concerns about the stability of the ship if it is made lighter.  I wonder what the "shippers" are thinking about?  I'd hate to have a classic car or something out there at the whim of the tides.

I saw an article titled: Rena forces rethink about fossil fuel.  Apparently in light of the earlier BP disaster, the discussion is back about offshore drilling near New Zealand.

However, I would wonder about a discussion earlier on TNS about nuclear powered container ships.  I would hate to think what the response would have been had this been a nuclear powered ship.  What if the reactor core is breached?  What if a nuclear powered ship breaks up and sinks?

[SeanB]

There have been a few cases of nuclear submarines sinking. In all cases the reactors went safe and did not release radiation. A nuclear reactor is rather extremely overengineered for safety in almost all conditions. The Kursk had a massive onboard explosion that almost tore it in half, but the reactors did as designed and safed themselves. A lot better than the daily fires in ship engine rooms. There was a trawler this last week that caught fire and sank. The only thing that saved the crew was that at the last port of call they were forced to buy safety equipment that they did not have - a liferaft and life jackets. Thanks to SAMSA they are alive.

[johan_M]

A nuclear reactor is rather extremely overengineered for safety in almost all conditions.

There's always a first time when the assumed safe engineering fails. Like in Japan.

[SeanB]

Perhaps. The reactors are still intact even though they lost all cooling and did melt down uncontrolled. Took weeks to determine that that did happen, and they did do this before the hydrogen explosion in the outer buildings. Now there are random radioactive patches in the surrounding areas, but there are areas around the harbours affected by the tsunami that are badly polluted by industrial wastes that were washed out of refineries and process plants into the areas. Of the two I would take the low level radiation over the toxic sludge.

[johan_M]

The next step in the Rena operation can now get underway.

Salvors have finished pumping all the oil off the ship and can now start on getting the containers off as well.

By this afternoon, 1350 tonnes of oil will have been removed.

Transport Minister Steven Joyce says removing the containers will be long and arduous and it could take up to a year to finish.
He says some oil may still be released, but the amount is not known.

[CliffordK]

Good to hear that essentially all of the oil is off the ship now.  Are they trying to get any remaining drops?  Or assuming it isn't enough to worry about. 

Now for the shore cleanup.  I'm glad to hear that it was only about 300 tons total that was lost.

Whew...  A year to empty the ship?

Summer is here...  at least down South. 

They need to plan on getting the ship empty in the next 3 or 4 months...  That would mean by February, or early March it should be empty...  I doubt that the ship will last a year.  If it is still on the reef in April, it will break up.

I'm surprised to not see a lot of effort to try to reinforce the crack in the hull.  There probably isn't a lot that can be done to repair it in the field, but I'd at least try to add some steel plate, angle iron, or channel iron to the accessible part of the gash to try to keep the ship together during the recovery process.  I think one could get a reasonably good weld with pieces of angle iron.

Of course, $12 Million into the recovery process, they might decide that it is cheaper to just let the thing sink, and scatter the shipping containers.

[Bored chemist]

Unless it was carefully designed and implemented a "patch" would act as a stress concentrator and do more harm than good.

[johan_M]

Calm conditions allowed 15 more containers to be lifted from the rear of the cargo ship Rena on Thursday, Maritime New Zealand (MNZ) says.

That means 18 containers have so far been removed of the 1280 left on the ship after it ran aground off the Tauranga coast last month.

However, MNZ warns the operation is at the mercy of the weather, as winds greater than around 24 knots - or about 45km/h - can halt the operation.

Salvors have now fitted 220 transponders to containers aboard the Rena in case they fall overboard.

Recovered containers will be checked out and if possible, will be put back into use after being cleaned out.

[ProjectSailor]

Got a few comments for clifford to assist building his massive wealth of knowledge. (apart form the spray freeze pipes for live works)


The Rena
All fuel tanks for major ships and tankers should be equipped with an emergency drainage system including high capacity pumps that can be remotely powered (and/or powered with a low-grade, wet version of the fuel they are pumping).  Can you deal with angles, as well as the limitations of a pump vacuum?

Not true these pumps are moderate capacity and there has never been a means of external discharge except via intervention and flexi hoses.
Remote power to a moving object is incredibly high risk doubly so with open fuel tanks near by as well..

Better off floating a fuel barge next to it and pumping from that (they are very high capacity pumps)

BUT fuel for large ships is HFO (heavy fuel oil) and rarely can this be pumped with the traditional pumps (centrif for the capacity) below 30 degC
Tanks are usually tall and thin so angles arent a problem (think it is rolling about all the time anyway)


I still believe the cargo containers should be removed from Rena, but realize that it is treacherous work with the ship listing so much.  Perhaps they could build some sort of a bookend to stabilize the stacks of containers, then get a crane onboard to start emptying the ship.
Don't these container ships have some sort of onboard crane?  Why not?

Onboard cranes cost money to install, use and carry around, economics is why there isnt a crane onboard Blame Capitalism


Any chance of salvage means keeping the ship from breaking apart.  I'd start patching the gash in the side the best way possible. I.E. adding lots of heavy sheet-steel and angle iron.

No chance, super structure is split, ship is now too flexible to actually move anywhere without breaking up, and patches would just present weak points, could be done with gargantuan beams and construct a 'ring' around it, but that may make it too rigid around that point and break up anyway


Bilge Pump Capacity?  Or a way to get a really big bilge pump onboard.  Does the bilge water need to be treated?  They need to be prepared to refloat during the super/king tides.

Lets face it there isnt anyone going to set foot on that ship, I would do it for a few grand and get power and pumps going in about 3 hours of setting foot on there.. (Might need a drop of diesel or two) and be perfectly fine to escape if necessary.. but health and safety they would be doing everything they can from other vessels.. (the problems they are facing is proof of such caution)

For all other Vessel and ship thoughts.. REMEMBER DISPLACEMENT the more weight the more water need displacing (this could be a method of getting the oil out, keep flushing with water, theres plenty of it in the HFO anyway (at least 5-6 % to start with)) So these floating drydocks need huge draughts (depth of hull) to displace enough water for the drydock AND the ship in drydock it would never in a million years be able to get under a vessel grounded on a reef!

[alancalverd]

There's safe and safe. In the case of the Fukushima reactors, they were subjected to an unforeseen stress - total loss of the cooling plant - but ships run aground from time to time and the stresses are entirely calculable. It's possible to design a reactor that shuts down if the coolant fails, not by any engineering mechanism but because the reaction can't continue at high temperature. 

Nuclear-powered icebreakers have been in operation for many years with few problems.