They’re water tight?
I could only take about a minute of that, in which he keeps repeating over and over and over again that containers collapsed.
Seemed like there wasn’t going to be a lot of meat on that bone.
The ships? yes.
The containers? sort of. They’re designed to spend weeks and weeks getting rained on and driven in the rain without the cargo getting wet. They’ll eventually sink, but the sides are 100% watertight, the doors have rubber seals which will give way if they’re bobbing in the sea for too long.
Is the max gross weight of a container large enough to offset the displacement buoyancy so it’ll sink immediately? Or are the heaviest possible containers still net buoyant, at least until they start shipping water.
Yes, containers can float. They can stay afloat for days. It can be a hazard to navigation. I’ve read than sailboats can be damaged running into them if the containers are mostly submerged and you can’t see them in time.
At about 18:50 in that video a stack of containers tips to one side releasing another container that falls onto the dock with a loud bang.
The question wasn’t whether they can float. Obviously an empty one can float just great; it’s merely a badly shaped boat. And as we see in the vid, they’re floating in the harbor just fine.
The question was whether they always can float, or whether it’s possible to legitimately load one heavy enough that it immediately sinks even before taking on any water.
A 40 x 8 x 10 foot container will displace about 100 tons of water according to my very rough estimate. According to Google, max load is about 30 tons. So it should float until water gets in. Then it’ll sink of course.
Damages estimated at $53.74
Unless some idiot overloads one by more than a factor of 3. Which shouldn’t happen… but then again, loading up a ship without securing it properly shouldn’t happen, either.
Thank you!
I own three forty foot containers and the roofs are practically tissue paper (about 1.5 mm). Falling from any height is enough to potentially rupture a container and allow it to fill with water.
I haven’t spent much time looking at the vids but it looks like the bottom containers collapsed under the weight of the ones above. Once the lashings were removed, the containers below weren’t aided by the integrity of the surrounding stacks. The fact that this happened in two separate areas suggests to me that the ship was loaded improperly (Heavy containers go under the lighter ones). The weights of the individual containers could have been tagged incorrectly or those loading just ignored them.
At least the front didn’t fall off.
I can’t see what you are describing but anyway I think this is doubtful. Dynamic forces imposed on stacks in a seaway greatly exceed static forces - it is consequently extremely unlikely that in port with the vessel largely stable the bottom containers would collapse due to static weight. The usual pattern is that once a stack starts to collapse sideways (for other reasons) the dynamic and uneven load on the lowest containers causes them to collapse. This particular cause/effect mistake is in my experience often made in these circumstances - even by those who should know better.
In addition to my comments above about it not likely being a static weight problem, I think this is too coincidental to be plausible.
Diagonal lashings are added by hand after the container movements in an area are complete. It’s too dangerous to add the lashings during loading. During this time, the stacks remain upright because (a) the vessel not moving and ideally is on a level keel and (b) twistlocks connect the corner castings. This means the stacks are a little vulnerable to athwartships forces during this time but this would not normally matter.
The aftermost row has collapsed first to starboard. If I had to guess I would say this has started with either a dynamic event such as a wayward crane movement knocking a stack sideways, or possibly a ballasting problem causing a heavy list to starboard (though such movements are usually too slow and controlled to do any such thing).
The collapse of the aftermost row to starboard may have caused a list to starboard that caused the bay forward of the accommodation to collapse.
It’s largely a myth that this matters. Support for upper containers is provided by the structure of (not the cargo in) containers below. Lighter cargo in lower containers does not magically detract from the support those containers provide to containers above.
If the overall stack strength is sufficient to support heavy containers above, that is true whether the containers below contain heavy or light cargo.
And nor is it true that lightest containers should always be lower. What matters is appropriate vessel stability - which can be either too tender (ie metacentric height too low) or too stiff (metacentric height too great). It can be beneficial to have heavier containers higher in the stacks if the vessel will otherwise be too stiff.
But what if it were a shipment of ping pong balls?
Stacking heavier containers higher will elevate the centre of mass of the whole system though; no magic required for that.
Individual stacks with heavy containers at the top will be more prone to tipping than stacks with light ones, because the higher the centre of mass, the easier it is for it to stray outside of the footprint of the stack.
The myth is that “heavier over light” is inherently a problem in itself.
Clearly, weight higher in the stacks creates a higher centre of mass. This either is or is not a problem, regardless of whether there is lighter cargo in lower containers.
As to whether it is good or bad for there to be mass higher in the stacks, see my final point.
It’s been a few decades since I worked loading and unloading containers, but my experience from back then is that they’re not necessarily watertight.
In some cases this was just because of minor flaws - for example from inside we’d sometimes see light entering through a hole (pinhole to pencil-hole) in one of the corners or elsewhere - either a gap in the weld or minor damage. Sometimes the door seals were imperfect, especially at the corners - there would just be a gap where the rubber didn’t mitre together.
And some containers had small vents covered with a fine metal mesh on the inside and sheltered by a metal plate on the outside - so they were rainproof, but not watertight. I don’t know if standards have changed in the intervening years, so maybe none of them have vents these days.
They are not watertight. In good condition they are weathertight.
The weatherseals will not withstand any significant head of pressure. If a hold floods to a depth of even say 20cm the containers at the bottom of the stacks in the hold will flood.
I don’t think that’s how centres of mass work. If you have a stack of containers of identical weight, the centre of mass will be in the geometric centre of the stack.
If you remove mass from the containers in the lower part of the stack, and do nothing else, the centre of mass of the whole stack will move higher and this stack will be more prone to tipping over than it was before you removed mass - just because if the CoM is higher up, it takes a smaller tipping angle to move it outside of the footprint of the stack.