_Description._--The propelling machinery was of the combination type,
having two sets of reciprocating engines driving the wing propellers and
a low-pressure turbine working the center propeller. Steam was supplied
by 24 double-ended boilers and 5 single-ended boilers, arranged for a
working pressure of 215 pounds per square inch. The turbine was placed
in a separate compartment aft of the reciprocating-engine room and
divided from it by a water-tight bulkhead. The main condensers, with
their circulating pumps and air pumps, were placed in the turbine room.
The boilers were arranged in six water-tight compartments, the
single-ended boilers being placed in the one nearest the main engines,
the whole being built under board of trade survey for passenger
certificate.
_Reciprocating engines._--The reciprocating engines were of the
four-crank triple-expansion type. Each set had four inverted,
direct-acting cylinders, the high-pressure having a diameter of 54
inches, the intermediate pressure of 84 inches, and each of the two
low-pressure cylinders of 97 inches, all with a stroke of 6 feet 3
inches. The valves of the high-pressure and intermediate cylinders were
of the piston type, and the low-pressure cylinder had double-ported
slide valves, fitted with Stephenson link motion. Each engine was
reversed by a Brown type of direct-acting steam and hydraulic engine.
There was also a separate steam-driven high-pressure pump fitted for
operating either or both of the reversing engines. This alternative
arrangement was a stand-by in case of breakdown of the steam pipes to
these engines.
_Turbine._--The low-pressure turbine was of the Parsons reaction type,
direct coupled to the center line of shafting and arranged for driving
in the ahead direction only. It exhausted to the two condensers, placed
one on each side of it. A shut-off valve was fitted in each of the
eduction pipes leading to the condensers. An emergency governor was
fitted and arranged to shut off steam to the turbine and simultaneously
change over the exhaust from the reciprocating engines to the
condensers, should the speed of the turbine become excessive through the
breaking of a shaft or other accident.
_Boilers._--All the boilers were 15 feet 9 inches in diameter, the 24
double-ended boilers being 20 feet long, and the single-ended 11 feet 9
inches long. Each double-ended boiler had six and each single-ended
boiler three furnaces, with a total heating surface of 144,142 square
feet and a grate surface of 3,466 square feet. The boilers were
constructed in accordance with the rules of the board of trade for a
working pressure of 215 pounds per square inch. They were arranged for
working under natural draft, assisted by fans, which blew air into the
open stokehold.
_Auxiliary steam pipes._--The five single-ended boilers and those in
boiler rooms Nos. 2 and 4 had separate steam connections to the pipe
supplying steam for working the auxiliary machinery, and the five
single-ended boilers and the two port boilers in boiler room No. 2 had
separate steam connections to the pipe supplying steam for working the
electric-light engines. A cross connection was also made between the
main and auxiliary pipes in the reciprocating-engine room, so that the
auxiliaries could be worked from any boiler in the ship. Steam pipes
also were led separately from three of the boiler rooms (Nos. 2, 3, 5)
above the water-tight bulkheads and along the working passage to the
emergency electric-light engines placed above the load line in the
turbine room. Pipes were also led from this steam supply to the pumps in
the engine room, which were connected to the bilges throughout the ship.
_Main steam pipes._--There were two main lines of steam pipes led to the
engine room, with shut-off valves at three of the bulkheads. Besides the
shut-off valves at the engine-room bulkhead, a quick-acting emergency
valve was fitted on each main steam pipe, so that the steam could at
once be shut off in case of rupture of the main pipe.
_Condensing plant and pumps._--There were two main condensers, having a
combined cooling surface of 50,550 square feet, designed to work under a
vacuum of 28 inches with cooling water at 60° F. The condensers were
pear shaped in section, and built of mild steel plates.
Four gun-metal centrifugal pumps were fitted for circulating water
through the condensers. Each pump had suction and discharge pipes of
29-inch bore, and was driven by a compound engine. Besides the main sea
suctions, two of the pumps had direct bilge suctions from the turbine
room and the other two from the reciprocating-engine room. The bilge
suctions were 18 inches diameter. Four of Weir's "Dual" air pumps were
fitted, two to each condenser, and discharged to two feed tanks placed
in the turbine engine room.
_Bilge and ballast pumps._--The ship was also fitted with the following
pumps: Five ballast and bilge pumps, each capable of discharging 250
tons of water per hour; three bilge pumps, each of 150 tons per hour
capacity.
One ash ejector was placed in each of the large boiler compartments to
work the ash ejectors, and to circulate or feed the boilers as required.
This pump was also connected to the bilges, except in the case of three
of the boiler rooms, where three of the ballast and bilge pumps were
placed. The pumps in each case had direct bilge suctions as well as a
connection to the main bilge pipe, so that each boiler room might be
independent. The remainder of the auxiliary pumps were placed in the
reciprocating and turbine engine rooms. Two ballast pumps were placed in
the reciprocating-engine room, with large suctions from the bilges
direct and from the bilge main. Two bilge pumps were also arranged to
draw from bilges. One bilge pump was placed in the turbine room and one
of the hot salt-water pumps had a connection from the bilge main pipe
for use in emergency. A 10-inch main ballast pipe was carried fore and
aft through the ship with separate connections to each tank, and with
filling pipes from the sea connected at intervals for trimming purposes.
The five ballast pumps were arranged to draw from this pipe. A double
line of bilge main pipe was fitted forward of No. 5 boiler room and aft
of No. 1.