Good day everyone! I work in the Dry Docks in Cape Town harbour and I thought I would share with you all the wonder and engineering feats of moving, maintaining and lifting this 12,000 tonne vessel!
Yes that is 12,000,000kgs of weight. How to move it? Well... it floats! We all know that man's early ships were made of wood as wood is buoyant - It floats. Later on we discovered that it was not just the material used, but the shape and displacement of water that would keep a huge hung of steel as is pictured above afloat!
If you fill the sink with water and place your largest pot into it, it will float, unless there is water inside the pot, in which case, the pot would sink.
A vessel this size uses that and another great design feature: Ballast tanks.
Ballast tanks take on and expel air in order to create pockets of buoyancy in the vessel as is needed. A vessel this size has different distributions of weight and ballast tanks allow the crew to keep the vessel up straight and under control.
So now... you want to work on the hull of this massive vessel. You need to take the water away and keep the vessel upright... this is how its done.
So first things first... You need a dock... a dry dock. This is what it looks like when it is full of water:
But before the vessel arrives, engineers take a drawing of the ships keel. Basically its footprint area and lay out chocks on the bottom of the dock when the dry dock is empty like so:
You can see the rows of blocks down there. Each one of those needs a forklift to move. They are massive blocks of concrete and are topped with wooden sleepers.
Right on the other side of the Dry Dock you will see there is a massive gate.
Here is another picture of it in the day:
When this gate is in position, you can walk over it... but this gate ALSO floats! They float it into position, using its own ballasts and it is towed into position. When it is where it needs to be, it starts to take on water until it has sunk down and it slots into grooves on the side of the Dry Dock. It will not separate the ocean from the Dry Dock.
Now the Port Authority can begin pumping the water out of the dry dock.
As they bring the vessel down towards the chocks there are special divers that go into the dry dock to ensure that the vessel is lining up with the chocks. if anything goes wrong the whole vessel could fall over so it has to be done just right!
Here you can see a space of the Dry Dock that is fully dry and people can now walk around in the dock and build scaffolding and work on the hull and the propulsion.
Below you can see more pictures of that floating wall that is used to divide the ocean from the dry dock. You can also see a whole bunch of space chocks.
The scaffold below was built so the wall can be maintained.
And there you have it! A basic overview of how the Dry Dock functions and many pictures of the dry dock taken by myself personally!
Thank you for reading!
Cheers!
