12 replies to this topic

[mariner]

Nothing to do with cars at all but the preliminary NTSB report on how the containership hit the bridge in Baltimore

 

https://www.ntsb.gov...aryReport 3.pdf

 

Basically the electrical power failed and that shut down the main engine which takes time to restart or reverse the propulsion engine.

 

 

[Canuck]

And the missing moments of the ships data recorder are additional failure. Talk about giving tinfoil hats something to talk about.

[Lee Nicolle]

A little off topic BUT we have everyone raving about dangerous ships etc and it probably was. But how about dangerous bridges? 

Lets build a meccano set bridge over a busy shipping channel. What could go wrong? A ship hits a pier and the whole bridge falls down!! Wrong bridge for the location and that is end of story. Probably fine over a gorge or even over buildings etc where nothing will hit the piers.

The Tasman bridge in Hobart Tasmania was hit by an ore ship, not on the navigation arch but 2 to the right. And 2 sections of bridge fell down. Reputedly the navigation arch would probably have taken the hit,, there is a LOT more concrete about it. And this was a concrete and steel bridge. The ship was carrying 10000 tonnes of ore so probably heavier than the ship in Baltimore. 

My interest in this in part is my mother missed the bridge going down by a few minutes. Her mother lived on the eastern shore and she lived then on the western side. So she crossed the bridge 2-3 times a week. I knew of through my cousin both the people left hanging over the edge. Hobart is a small town!

[Greg Locock]

It isn't practical to design the bridge itself to resist an impact from a 100000 ton ship moving at several knots. You have to surround it with dolphins and starlings and other weirdly named lumps of concrete to fend the ship away from the structure.

https://www.engineer...ainst-big-ships

[gruntguru]

You can design it so that ships are unable to impact it.

[mariner]

If you read the whole report it does say that "dolphins" i.e big posts in the ground were installed to stop ships hitting it. Unfortunately they were not in the right place for that ship

[GreenMachine]

Tunnel FTW.  Job done.

[gruntguru]

The Tasman bridge in Hobart Tasmania was hit by an ore ship, not on the navigation arch but 2 to the right. And 2 sections of bridge fell down. Reputedly the navigation arch would probably have taken the hit,, there is a LOT more concrete about it. And this was a concrete and steel bridge. The ship was carrying 10,000 tonnes of ore so probably heavier than the ship in Baltimore.

 

The "ship in Baltimore" was carrying 56,000 tons of cargo for a total weight of 112,000 tons.

[gruntguru]

Although there seem to be lots of redundancy in the ship's power system, there are a number of things I find surprising.

1. There is only one driveline for ship propulsion and no auxiliary thrust available - apart from the bow thruster which presumably can only provide lateral thrust.
2. The main engine is not self-sustaining, even after starting. It requires external power from a 4,000 kW genset to run its oil pumps and cooling pumps.
3. The ship data recorder lost data feeds from the vessel (although voice data from the bridge was uninterrupted).

[Canuck]

4 million watt genset for oil and cooling.

[Catalina Park]

The Tasman bridge in Hobart Tasmania was hit by an ore ship, not on the navigation arch but 2 to the right. And 2 sections of bridge fell down. Reputedly the navigation arch would probably have taken the hit,, there is a LOT more concrete about it. And this was a concrete and steel bridge. The ship was carrying 10000 tonnes of ore so probably heavier than the ship in Baltimore. 

 

 

 

The "ship in Baltimore" was carrying 56,000 tons of cargo for a total weight of 112,000 tons.

The SS Lake Illawarra weighed between 17,000 and 18,000 tonnes when it bought down the Tasman Bridge. 

[just me again]

Although there seem to be lots of redundancy in the ship's power system, there are a number of things I find surprising.

• There is only one driveline for ship propulsion and no auxiliary thrust available - apart from the bow thruster which presumably can only provide lateral thrust.
• The main engine is not self-sustaining, even after starting. It requires external power from a 4,000 kW genset to run its oil pumps and cooling pumps.
• The ship data recorder lost data feeds from the vessel (although voice data from the bridge was uninterrupted).

I remember being told in the nineties of a guy working in the engine on Mærsk ships that some of them had a generator behind the main engine. So at sea, they only run the main engine.
If the main engine stops. It can be reversed, so by turning on all auxiliary generator the big generator/electric motor can propel the ship with a few knot's!!

[gruntguru]

It is not uncommon these days for ship drives to be diesel-electric. Electric motor in a steerable pod turns the propeller (prop in front of pod - clean flow increases efficiency) and the electricity is produced by any combination of several diesel and GT gensets operating near peak efficiency.