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Daniel Ago
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Daniel Ago   My Press Releases

Largest Moving Objects Made by Man

Published on 3/19/2019
For additional information  Click Here


IN 1577 Sir Francis Drake set out on his famous voyage around the world, sailing in the Golden Hind, a ship that was only 75 feet long. Compared with today’s goliaths of the sea-lanes, that is like a minnow beside a whale. Ships still hold the distinction of being the largest moving objects made by man, barring none of his prodigious achievements.
The world’s largest vessels are fast becoming a common sight entering Lisbon’s Tagus River. But not until a person sees one close up is he really overwhelmed by the size of a modern-day oil tanker. With a carrying capacity of 312,000 tons deadweight, the sheer massiveness of these behemoths is staggering. Over a fifth of a mile long, they seem, at times, to choke even the river itself. On a single trip from the Middle East to Northern Europe, their cavernous holds store 65 million gallons of crude oil.
As we stand watching one of these giants gently move up the river, we wonder how they are maintained. What is involved in repairing a ship this size? Can it be taken out of the water after being launched? If so, how?


Since Europe’s largest repair dry dock is situated at Lisbon’s harbor, we decided that a visit to the shipyard would be most interesting. Crossing the river, high on the Salazar Bridge, we have an impressive view of the harbor. It has a spacious maneuvering area, which is so essential for large ships. Here also the year-round average temperature of 60° F. permits good working conditions during all seasons. The bay never freezes.


A geographical factor makes the Iberian peninsula a choice location for a repair shipyard. At the present time it is estimated that 70 percent of the world traffic of oil tankers and ore carriers passes this zone, heading to northern Europe either from the eastern Mediterranean or around the African continent.
Did you notice that the oil tankers we saw all ride high on the water, with sections of the rudder and propeller visible? This is because they are entirely empty. Only after unloading their cargoes in Northern Europe and on the return voyage to the Middle East are they in suitable condition for repair work. Now we understand why the Port of Lisbon is favored with the role of host to an ever-increasing number of vessels.


The Lisnave shipyard is located on the south side of the harbor in a convenient bay that offers shelter against strong winds and rough seas. It is interesting that the quayside and dry docks have been constructed in the direction of the predominant winds, a factor of no small importance when handling vessels so big.

 


Visiting a Dry Dock
As soon as we enter the shipyard our eyes behold two large dry docks, side by side. What tremendously large basins they are! The largest dock is over 1,148 feet long, 180 feet wide and 42 feet deep. At the time of our visit the Esso Northumbria, Britain’s latest and largest ship, is in the dry dock for final inspection before entering service. What a length she is, 1,143 feet—the equivalent to the combined length of three football fields, with room left over for the cheering sections!


The designation dry dock seems so appropriate. Repair and repainting of ships below the waterline can be done only by taking them clear out of the water. When the dry dock is flooded and the gate opened, water fills the dock to normal sea level. The vessel is carefully guided into the dry dock and centered. The dock gate is closed and then the water is pumped out. Interesting is the fact that the larger the vessel, the less water to remove. As the water is removed, the ship’s keel rests on a row of central blocks and two lines of movable bilge blocks that support the outer edges of the ship’s bottom. At times the weight on the keel blocks can be as much as 300 tons per linear meter.


A routine job is to repaint the ship below the waterline about once a year. The hull is first given a high-pressure water washing. If the vessel has accumulated barnacles or considerable fouling organisms, it is cleaned by a shotblasting process. This shipyard uses granulated copper blasted under pressure to remove corrosive elements. Once the hull is cleaned, it is painted.
But how quickly the job is done! Only a dozen men are required to paint the ship in less than twelve hours’ time. They move about on mobile metal towers of adjustable height and can paint about 500 square yards an hour. The paint is completely dry in an hour. Can you imagine how much paint is used to do the job on a big tanker? Over seven tons!


We did not realize the importance of a good paint job. Actual experience shows that on a vessel of 115,000 tons deadweight, there has been a loss of 1,000 horsepower due to a poor paint job. On some ships ten tons of barnacles or corrosive particles have been removed. With general fouling or skin friction reduced to a minimum, imagine the saving this represents in financial terms.


Work in the dry dock can involve the removal of the rudder or propeller. This is no small task when you see the size of these parts on a supertanker. Why, on the Esso Northumbria the rudder alone weighs 115 tons and is the height of a four-story apartment building. The single six-bladed propeller weighs 56 tons and is secured to the tail shaft by an enormous nut. Sometimes ships are even cut in half and a completely new prefabricated section is added. This kind of repair work can involve hundreds of tons of steel.
Only in the shipbuilding yard or a dry dock is it possible to see the bow of a ship. What a surprise to see such a huge protruding nose. This type of “bulbous bow” is now being fitted on many older vessels since it can increase the speed of some ships by one knot. That may seem negligible, but for a ship with a service speed of nine knots, that means more than a 10-percent gain.
Although the jobs undertaken appear time-consuming, we noted how comparatively little time is spent in a dry dock. On the average this shipyard has a vessel in the dry dock for only four days. A mere five hours is required between the completion of work on one ship and the start of work on the next ship in the same dry dock. Our guide told us that shipowners sustain a loss of at least $25,000 each day a large tanker is out of operation. So there is great concern for efficient and fast work.


On a tour around the shipyard we see cranes of 50- and 100-ton capacity. Never before have we seen such large pistons! Three of them over a yard in diameter with shafts 10 feet long. In the machine shop shafts up to 82 feet in length can be machined by operating a 12-ton lathe together with a 40-ton lathe. The electrical shop has electrodynamic balancing machines for diesel repair service and a division for rewinding stators. The pipe shop is equipped with smelting and heating furnaces used in remetaling giant bearings. The plate shops and prefabrication areas are busy with all types of structural-steel work.
All tanks on an oil tanker must be periodically cleaned. The practice of discharging into the sea oily water resulting from tank washing is most reprehensible.

The National Commission Against Sea Pollution is working to eliminate this detrimental and deliberate pollution of the seas. It was encouraging to learn that this shipyard has fitted two old vessels as tank-cleaning stations. The latest technological processes are being employed to clean tankers entering the Tagus estuary. All oily residues are completely burned and destroyed on board these tank-cleaning stations, and only clean water is put back into the sea. This method is helping to safeguard local beaches, plus offering the needed protection to fish and the fishing industry.
Tomorrow’s Ships


Can ships be built any bigger than they are today? Japanese shipyards are in the final negotiating stages to start construction of tankers up to 500,000 tons deadweight. A chief engineer of Britain’s largest shipbuilders told us: “We’re looking ahead. I wouldn’t be surprised if in a few years we see ships being ordered for 750,000 or even a million tons.”
The Lisnave shipyard is preparing for the adve

nt of the million-ton tanker. Actual construction is under way for a third dry dock that will handle ships up to 500,000 tons, with a second phase of enlargement to take 750,000 and, in its final stage, the million-ton vessels. Final dimensions of this dry dock are 1,800 feet in length. Its first phase is planned to be operational by 1972 with a width of 276 feet.


To grasp how big a dry dock that is, let us illustrate. The capacity of the five pumps that will be used to take out the water is sufficient to supply the entire daily consumption of sweet water in the Netherlands, the country where they are being built!


There is a lot more to keeping a vessel shipshape than we had imagined. It is no understatement to say that everything about today’s ships is colossal. The ships planned for tomorrow seem to stagger the imagination. But really, no matter how colossal the ships of tomorrow become, are they not as specks compared to the immensity of the oceans in which they operate? The largest moving objects made by man are eclipsed by the Creator’s work, the sea around them.

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