Why Don't These Containers Fall Off?

no matter how big your ship in a heavy sea is going to move around this means that no matter what ship you're on you need to make sure your cargo is secure but what about on a container ship where the boxes are stacked high up into the sky especially as when they get into a port it seems like the cranes want to start work immediately just lifting the containers off with ease surely if they can be removed so easily they just fall off when the ship starts rolling around well this is one of the truly amazing parts of containerization and it all comes down to the design of the container itself specifically thanks to the corners of the containers which consist of a hollow block and oval holes on the three outer sides when you place two containers next to each other either side by side or one on top of the other the idea is that the holes in the corner pieces will line up just chuck a pin through the holes and the container can't move well it can't slide around but you could still lift it off the grain driver would be happy but the ship's captain not so much if the ship rolled the top container could just roll off that was at the bottom of the stack the entire stack would collapse so instead you need to be able to lock the pin in position and we do that with a device called twist lock because the hole in the container is oval you can fit a lug through the hole and twist it to secure it in position the simplest design involves a load bearing plate in the middle with two lugs one sticking up and one sticking down there's also a single lever which simply rotates the lugs once the container is in place all you need is a crew member to run around and turn all the levers to lock every container down to the ship it's called a manual twist lock as it relies on manual input to lock it into position those are great when you can get to all the levers to check them and you can get to every container to place the lock before the next one's lowered on top captain's happy crane driver's happy lorry driver's even are happy but crewman who has to climb up to the top of a stack of containers carrying 50 kilos of twist locks isn't so impressed no on ships you need a better solution and for that we have the more expensive semi-automatic twist locks there are loads of designs so let's just take a look at one of the easiest ones to understand i don't actually know if this is precisely a real design or whether i've just made it up so let me know in the comments if you've used one like this or whether we should start making casual twist locks or something basically it's a manual twist lock butt is spring loaded so the spring keeps it locked in place in the locked position the top lug sits at 90 degrees to the base plate and the bottom lug sits at 45 to release the lock we have a toggle which you pull against the spring and can lock in two different positions pull it up and into this catch and you've turned the lock 90 degrees releasing the top lug pull it down and into this catch and you've turned the lock only 45 degrees releasing the bottom lug both lugs are shaped a little like a helix so when the twist lock is in the locked position container placed onto it will twist the lug against the spring until it goes through the hole completely which point the spring will twist it back locking the container in place to fit the lock a crewman on the ground pulls the toggle up and fits it into the bottom corner of the container ready to be lifted by the crane then they just release the toggle so it's left in the locked position the crane then lifts the container onto the ship placing it in the correct location according to the stowage plan containers are usually given a six digit code for their position on the ship the first two digits tell you the bay with zero one at the bow and numbers increasing towards the stern each of those bays could be further broken down depending on the length of the container in the bay with odd numbers showing 20-foot containers and even numbers showing 40-foot containers for example in this first bay 0-1 would indicate a 20-foot container at the bow and 0-2 would be either a 20-foot container in the back half of the bay or a 40-foot container spanning the bay the next two numbers in the six-digit code tell us the row of the container these are numbered from the center of the ship outwards with odd numbers to starboard and even numbers to port so we'd have rows one two three four five six and so on final two numbers tell us the tier that the container sits in with tiers two four six etc below deck tier eight zero often indicates deck level and eight two four six etcetera stacking up into the sky anyway the crane uses the six digit code to place the container in the correct place and lowers it down remember we said that the lugs are helically shaped so the weight of the container pushing down will twist the lock through the 45 degrees required for the container to drop into place once down the spring fires it back around locking the container in the crane drive is happy the master is happy and the crewman is happy as he didn't need to climb up onto the stack to place the locks great how do we get the containers off again well remember we said that there were two locking positions for that toggle the crewman can use a long pole to get hold of the toggle and pull it down the downward locking position sets the lock at 45 degrees releasing the bottom lug while keeping the top one attached the crane can then lift the container off the ship keeping the twist lock attached to its bottom corners when it's safely down on the key side the crew can go around and release the locks completely getting all their nice fancy semi-automatic locks back the container is then free to continue its journey through the transit system probably onto a truck where the driver might prefer to use a cheaper manual lock as it's easy to reach all four corners on the bed of the truck you see this is the magic of those four standardized corners of a shipping container they can accept fancy locks that secure them onto a stack at the top of a ship they can equally accept manual locks that will secure them to the bed of a truck or even to a train and it can even accept automatic locks into the top corners which secure them onto the lifting boom of the crane or the booms of a reach stacker containerization and the twist lock in particular mean that we can have a massive ship with containers locked together ready to handle rough weather yet they can also be released so that in port cranes can get to work quickly and unload the correct cargo and get new cargo back on so next time you see a container ship you'll know that the containers are nice and secure yet quick to unload even if it looks like they're stacked really high up into the sky

Channel: Casual Navigation

Views: 782,437

Keywords: casual navigator, marine, shipping, casual navigation, maritime explaination, merchant navy, sailing, marine animation, twistlocks, twistlock, container ship, shipping container

Id: fhSCQTuXrJk

Length: 6min 14sec (374 seconds)

Published: Fri Aug 26 2022