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Introduction -
Consistent with the White Star Line’s policy of eschewing speed in favor of size and
comfort, the efforts of Harland & Wolff’s marine engineering department were
focused on developing machinery plants of relatively moderate power in comparison to those
“Blue Ribband” contenders of White Star’s competition. The main criteria in
designing propelling machinery for White Star’s vessels was high economy and
reliability, with sufficient reserve power to guarantee that the required service speed
would be maintained in even the worst conditions. Additionally, the machinery had to be as
nearly vibration-free as practical. This was of utmost importance in the Line’s
premier ships, which were those on the transatlantic run to and from New York. By the late
1890s, Harland & Wolff had turned to triple-expansion reciprocating engines of the
four-crank design, employing low-pressure cylinders at each end. (continued below) |
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Image above, Engine Rooms - Transverse sections through the
Turbine and Reciprocating Engine Rooms. Author’s
collection
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This arrangement permitted much
larger engines and kept the dimensions of the components of the low-pressure stage to
reasonable size. Of equal importance, the four-crank arrangement allowed the application
of the new Yarrow, Schlick and Tweedy system of engine balancing. Engines of this type,
producing a gross 28,000 indicated horsepower (IHP), were fitted to the 17,274-GRT Oceanic
(II) of 1899, giving her a top speed of over 21 knots, though in service she was usually
run at the 19½-knot service speed of running mates Teutonic and Majestic.
(continued) |
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Reciprocating
engines - The two sets of reciprocating engines were of the four-cylinder,
triple-expansion, direct-acting inverted type, balanced on the Yarrow, Schlick and Tweedy
system. After a slight drop in pressure due to expansion within the various supply lines
and valves, steam from the boilers arrived at the high-pressure cylinder of each engine at
210 PSIG. Steam exhausted from the high-pressure cylinder was then directed to the
intermediate-pressure cylinder, where it was received at a pressure of 78 PSIG. After
doing its work in the intermediate-pressure cylinders, the steam was then exhausted to the
respective low-pressure cylinders, where it was received at 24 PSIG for further expansion.
After having been expanded as far as practical within the reciprocating engines’
low-pressure cylinders, the steam was exhausted at a pressure of about 9 pounds per square
inch absolute (PSIA) - below atmospheric pressure - and directed towards either the low
pressure turbine or directly to the condensers . . . (continued) |
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Propeller
shafts - At its forward end, each outboard shaft terminated at a large thrust
block assembly. When the engines were turning ahead or astern, the revolutions of the
propeller drove the ship forward or backward. This thrust occurred as a result of the
propeller exerting a force along the shaft in the respective direction. The crankshafts of
the reciprocating engines, however, revolving in simple bearings, were not designed to
absorb this thrust. To take up this thrust and convey it to the hull, thrust blocks were
introduced just abaft the reciprocating engines. These served to transmit the fore-and-aft
thrust generated by the propeller to the ship’s structure. The thrust blocks were
situated in the Turbine Engine Room, just aft of the watertight bulkhead dividing this
compartment from the Reciprocating Engine Room. . . . (continued) |
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Boilers
- Each double-ended boiler was 15'-9" in diameter, 20 feet long, and contained six
furnaces. The single-ended boilers were of the same diameter as the double-ended but only
11'-9" long; each contained three furnaces. This resulted in a total of 159 furnaces.
The furnaces were all of the Morrison type, having an inside diameter of 3'-9", and
were provided with furnace fronts of the Downie “boltless” pattern. The firebars
were of the Campbell type, supplied by the firm of Railton, Campbell & Crawford, of
Liverpool. Within each furnace was an interior partition called a furnace bridge, or
“bridge wall.” This was located at the back end of the fire bars which formed
the grate. In addition to supporting the back end of the grate, the lower portion of the
furnace bridge separated the lower portion of the furnace tube (the “ash pit”)
from the upper portion (the crown, or “firebox”). The heat and gases of
combustion were kept above the grate while all air drawn in through the ash pit by the
draft of the fire passed through the burning fuel resting on the grate. . . . (continued) |
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Return-feed plant
- The main air pumps discharged the condensate removed from the condensers into two feed
tanks, one placed on each side of the ship just abaft the bulkhead dividing the engine
rooms. Each feed tank had a capacity of 2,790 gallons. From the feed tanks, the water
drained into two Weir control tanks, one on each side of the Reciprocating Engine Room.
The control tanks measured 4' x 4', with a depth of 3 feet. The water was drawn from the
control tanks by four Weir single-cylinder, vertical direct-acting hotwell pumps. Each of
these had a pump barrel 14 inches in diameter, a steam cylinder of 14 inches diameter and
a stroke of 24 inches. The hotwell pumps were located in pairs on each side of the ship
immediately adjacent to the control tanks. Each pair was capable of dealing with the whole
of the feed water, i.e., 700,000 pounds per hour; but under ordinary conditions all four
pumps were operated together at slow speed.
From the hotwell pumps, the feed water was discharged through the main feed
filters. These filters, of which there were four, had a grid area of 17,000 square inches . . . (continued) |
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Titanic’s
Tank Top, showing general arrangements of boilers, engines and auxiliaries. Illustration by Bruce Beveridge |
Other topics in this chapter:
Background: the decision to employ combination machinery - Arrangement of
machinery - Uptakes and funnels - Bunker arrangements - Ash hoists and ejectors - Boiler
room fans and ventilation - Steam pipes and valves - Exhaust steam turbine - Maneuvering
gear - Condensers - Evaporating plant - Shaft bearings and propellers - Main engine seats
- Thrust seats - Propeller shaft stools - Boiler stools - Mobility through boiler and
machinery spaces (raised decks, access to the higher levels, gratings, ladders) |
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