(Saturday, March 12th, 2016)
Today I spent a lot of time on the pilot deck watching some interesting loading operations. I probably caught a cold – it was cold and windy – but it was worth it. At dinner Captain said he saw me taking photos of his men working. I told him that it was extremely interesting. We talked (well, I listened and asked questions) ’till well after dinner. I remembered some tidbits that I hope are interesting to others – they were to me.
Heavy
Our ship is special because we are a heavy-lift cargo ship. The floor (that is not the correct term) in each of our holds is much thicker than usual. Our 2 middle cranes can lift 320 tons each, and our puny little end cranes can lift 100 tons. Our larger middle cranes have 2 hooks each – one of them is the 320 ton hook, and the other is a 65 ton hook (something like that), perhaps suitable for much of the common work. The maximum weight a crane can lift is relative to vertical – when a crane needs to span, its capacity goes down. Our cranes won’t attempt an overweight lift. They give an overload signal.
By the way, those cranes that you see dockside might look massive but in general can only handle 100-125 tons. Containers are limited by law to 40 tons gross weight, so many dockside cranes get by with 100 ton capacity or less. We are carrying a few containers on this voyage, but they aren’t the interesting cargo.
The Captain told a story in which some containers being loaded onto a container ship were mis-advertised as to weight – they were heavier than they should have been. He said that, at sea, it caused the container ship to tip over. I have a feeling that the story is more complicated than that, but it did make me think that the weight of everything being shipped is not exact – it is an estimate, and there’s a sense of “trust, but verify for the really important stuff”.
Our supercargo people (those directing loading), our officers, and our able-bodied seamen are all trained with heavy loads. Under 100 tons? Not heavy.
So, our ship might not look so different from some others, but it is built differently, and some loads demand a ship like ours. Even in an economy downturn that has lowered overall shipping, there are still jobs for these vessels.
Our captain is really into the heavy lifting. He likes taking on the challenges of loading really heavy cargo. The largest he lifted was 720 tons (not with this ship). A surprise for me: You can’t lift that from the dock as it is too heavy, breaks the dock. Oh my. You have to lift from a barge. So the barge and the ship can take the shocks because they are dampened by the fact that they are floating (pun intended). Then, you have to watch because as you lift, your object is still connected, still touching, as you unweight the barge, and the barge will move. Plus you are using two cranes in unison. Those are the lifts that get planned in advance.
Overlight is also tough. Some items are harder to lift because they require two cranes due to their size but are light and so move differently than expected, and the cranes are built to handle heavier weight. Some crane structures are that way (when we ship a long crane built of triangulated tubular steel), and the large wind generator blades are that way.
Included on our ship today: Many pieces of what looks to me like process control equipment, complete subsections enclosed in cages for the journey. 2 boats, catamarans. 4 mobile cranes – you know, those trucks with huge tires, and the tiny little driver’s cockpit, and a pretty hefty crane above. 4 of them. The 4 crane trucks were put in the middle, deep, and are already covered over with a mid-deck. That’s one of those eye-openers as to how big the ship is – it swallows some stuff that you already thought was big.
Thinking about weight… Today, taking some pictures was tricky because there was a lot of wind, maybe 30 knots, blowing me around a bit, making a steady camera difficult. I asked Captain if wind like that was a problem for the lifts. His answer: “No.” Ha.
Loading
The basic rules of loading should be easy, eh?
Rule #1: Whatever has to come off first, should go in last.
Too bad! Often, almost usual, is that the source location and the target location aren’t aligned so well.
Rule #2: Move the least amount of stuff the least amount of times.
Great idea. But. Quite often you have to wait on transport for just that item you wanted to put in one spot. And you have other transport, with their items, on time, waiting on you. You have to be flexible.
Rule #0: Safety tip: The ship must be balanced or it will rip itself apart when we start to sail.
Aha! Rule #0, above all others. Shoulda’ put it first.
Balancing
Even that is not so simple. Think of the ship as a 200 meter long half-tube. It is flexible, given its length and the amount of weight we put in it. There are at least these balance factors that must be considered:
— Moment
This is what the Captain called it, I might have used a different term but it’s fine. If you put too much weight in the middle of the ship, the long tube will bend like a sleeping parenthesis that can hold water. If you put too much weight in the ends of the ship, the long tube will bend like a parenthesis on its side that thinks it is a bridge over a stream. Either one will cause excessive flex when facing the dynamics of being at sea.
— Torsion
Let’s say you put half of the weight port-side forward (left front), and the other half of the weight starboard-side aft (right rear). You have set up the long tube to twist when at sea. Not a good idea.
— Shear
This one surprised me. The Captain said that the walls between holds are very strong but they can’t do everything. Let’s imagine that in one hold you put a lot of weight. In the hold just behind it you put nothing. Maybe you are saving that hold for the next port, who knows. Tons and tons of gravity are working to move the floor (sorry, I will find the right term sometime) of the heavy hold downward, and carry the connected wall with it. Tons and tons of buoyancy are working to move the floor of the empty hold upward. That poor adjoining wall is stressed. The thick floor helps but can’t do everything.
Given all that, it is a wonder they get started loading at all! Anyway, I was very happy to learn about it. There are some computer simulations and assists that they use, but so often other factors move them away from the “ideal” assumptions with which the simulations start. The mathematician in me wonders if there’s a solvable optimization problem in there, but I decided not to bring that up to Captain just yet. I plan on taking a peek at the simulation some time, but I need to find the right mark, um, er, helper, to get it in front of me.
Deck Arrangement
I think I’ve written about this before, but now I have the terms closer to correct, and I have some sizings.
They don’t use the term “floor” or “shelf”. Pontoons (I will caption some photos) are put into place to form mid-decks. There. We have the terms correct. But the bottom of the hold is not a deck and not a floor. I don’t know that one yet.
The pontoons are 3 meters by 10 meters, and each pontoon weighs about 8 tons by itself. When placed to form a mid-deck, the pontoon can support 40 tons per square meter.
Ballast
To help smooth out the balance, there are at least a couple types of ballast.
Usually there are pontoons left over. Planners tune the balance by arranging the pontoons as ballast, putting them where their weight will do the most good. Once the pontoons are put in place, though, that’s it for the voyage – just like the cargo.
In addition, there are 32 water tanks that are used for ballast. Sea water is pumped into and out of these tanks to change weighting. This can be done while underway.
And even that arrangement, complicated as it sounds, has additional factors to consider. All sea water is not created equal. Some places, US for example, require that the sea water in our ballast tanks must have come either from seas close to the US, or from mid-ocean areas that are at least 400 meters deep. I guess that they don’t want the chance that US waters might become contaminated with organisms that we might have picked up in shallow foreign waters. So, along the way, we must keep track of what we need to do with the ballast tanks in order to comply.
Crane Drivers
That’s what he called them, I think it is appropriate. We had a conversation about crane driver ability. This is my take: Like for programmers (I didn’t tell him that), there’s a huge difference between an excellent crane driver (give him a 10), a crane driver you can trust for the ordinary work but not so much for the special stuff (give him a 2), and the crane driver that seems to make ordinary stuff take longer than necessary, and who can’t help but damage things every so often (give him a -1). An excellent crane driver is also involved in the discussions about the tough lifts. That conversation we had could so have been about programmers. I wonder if there are more professions like that. I bet there are.
The dockside drivers are union, and go through certification. The supercargo people and our agents at each port know them, and know when we’ve got good ones. I did not understand from the Captain if we could request a specific crane driver to support us. I don’t think I asked the question correctly.
We have crane drivers on the ship. A seaman cannot move from O (I think “ordinary”?) to AB (“able bodied”) until they show proficiency in two major areas: driving the ship (helm work, able to take a shift) and driving cranes. Captain said that we have some good crane drivers on board. Almost always, because our on board cranes can lift more weight than the dockside cranes, the special lifting involves our on board cranes, so we get to use our crane drivers.
The Captain said that it is not just special heavy lifting that brings out differences. Often they need to “make a new mid-deck”, which involves moving several pontoons from either their storage location on board or from dockside where they’ve been moved. A routine task, even though there are many steps. Nothing tough. But an inexperienced or inept driver can take up too much time. Like changing a half hour job into a two and a half hour job.
Container vessels, no cranes on board, are so standardized that they align carefully at the dock, and the cranes are “gantry cranes”, with the hooks hanging from wires from a straight runner. All orderly. Boring to Captain.
A Little More on Bunkering
We bunkered yesterday while docked. Tanker on the other side. Multitasking! No smoking anywhere!
We carry 2600 tons of fuel oil and 400 tons of diesel. Diesel is cleaner burning. We use diesel inside of environmental zones, i.e. in ports in US and Europe, and, next trips to China next year, China. At 30-35 tons a day, we have 85-100 days of travel in us right now. I think that we are bunkering next in Houston.