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Introduction - An empty ship, riding
high out of water with its center of gravity well above the water line, is top-heavy,
unstable and liable to capsize in a storm. A vessel in such a condition is also subject to
a far greater influence from the wind and therefore difficult to steer and likely to be
driven off its course in rough weather. For these reasons, the practice has always been to
bring an unloaded ship farther down into the water by placing some heavy material, known
as “ballast,” in the bottom of its holds. |
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For centuries, ballast consisted of dirt, sand,
gravel or stones, taken from the shores of the harbor where the ship unloaded its cargo.
This caused serious delays at both ends of the route, because this type of ballast could
not be put aboard until after the cargo had been off-loaded and it then had to be removed
before a return cargo could be brought onboard. It was also undesirable from the
standpoint of expense, as wages had to be paid for handling ballast with no revenue earned
for carrying it.
Around 1885, the carriage of water ballast in iron and steel ships was made
possible through the introduction of the “McIntyre tank.” This tank was formed
in the bottom of the ship by a watertight plate cover built above the floors of a
single-bottom ship and supported by fore-and-aft girders riding on the tops of the floors.
Into the space created, water ballast could be pumped to give the vessel sufficient draft
when light . . . (continued)
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Image above, Transverse
sectionsThe Waterworks of a Giant Liner - An illustration from an early 1920s
book called The Book of Familiar Things. This image shows the domestic freshwater systems
of a ship approximately the size of one of the White Star Line’s “Big Four”
liners. Though a bit smaller in scope, the basic system depicted here was used on the Olympic-class
liners. William Daystrom collection. |
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Double-bottom
tanks - Titanic’s cellular double bottom was divided into 44
compartments; the addition of the Fore and After Peak Tanks resulted in a total of 46. Six
of these tank compartments (those within the margin plates beneath the two engine rooms)
were used exclusively for fresh water for boiler feed make-up purposes. The wing tanks
outboard of these and all of the tanks under the boiler spaces, as well as the Fore and
After Peak Tanks, were reserved for salt-water ballast only. The remainder of the tanks
within the double bottom could be filled with either salt or fresh water. Each of these
compartments had pipe suctions connected through a main pipe to the ballast pumps.
Specifically, 14 of these compartments had 8-inch suctions, 28 had 6-inch suctions and
three had 5-inch suctions connected to the 10-inch ballast main suction. The total amount
of water ballast that could be carried by Titanic (including feed-water stores)
was 5,754 tons, of which 190 tons were in the Fore Peak Tank. . . (continued) |
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Fresh-water system - Fresh-water
storage tanks were located throughout the lower structure of the hull. Their containing
walls were formed by the vessel’s bulkheads, decks, and side plating. Fresh water
intended for boiler feed water or for washing water was stored in tanks in the double
bottom. The storage tanks for drinking water were located above the double bottom and were
designated solely for that purpose. These tanks were emptied and refilled at the end of
each voyage.
Individual tanks were advantageous in that there was no chance of the entire
supply being spoiled by salt water leakage into a single tank. Six of the seven tanks for
drinking water on Titanic were positioned . . . (continued) |
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