The New York Subway, Its Construction and EquipmentInterborough Rapid Transit Company
History
The New York Subway, Its Construction and Equipment
Interborough Rapid Transit Company
Local transit -- New York (State) -- New York; Subways -- New York (State) -- New York
Arrangements have been made for the erection of four turbo generators,
but only three have been ordered. They are of the multiple expansion
parallel flow type, consisting of two turbines arranged tandem
compound. When operating at full load each of the two turbines,
comprising one unit, will develop approximately equal power for direct
connection to an alternator giving 7,200 alternations per minute at
11,000 volts and at a speed of 1,200 revolutions per minute. Each unit
will have a normal output of 1,700 electrical horse power with a steam
pressure of 175 pounds at the throttle and a vacuum in the exhaust
pipe of 27 inches, measured by a mercury column and referred to a
barometric pressure of 30 inches. The turbine is guaranteed to operate
satisfactorily with steam superheated to 450 degrees Fahrenheit. The
economy guaranteed under the foregoing conditions as to initial and
terminal pressure and speed is as follows: Full load of 1,250
kilowatts, 15.7 pounds of steam per electrical horse-power hour;
three-quarter load, 937-1/2 kilowatts, 16.6 pounds per electrical
horse-power hour; one-half load, 625 kilowatts, 18.3 pounds; and
one-quarter load, 312-1/2 kilowatts, 23.2 pounds. When operating under
the conditions of speed and steam pressure mentioned, but with a
pressure in the exhaust pipe of 27 inches vacuum by mercury column
(referred to 30 inches barometer), and with steam at the throttle
superheated 75 degrees Fahrenheit above the temperature of saturated
steam at that pressure, the guaranteed steam consumption is as
follows: Full load, 1,250 kilowatts, 13.8 pounds per electrical
horse-power hour; three-quarter load, 937-1/2 kilowatts, 14.6 pounds;
one-half load, 625 kilowatts, 16.2 pounds; and one-quarter load,
312-1/2 kilowatts, 20.8 pounds.
[Sidenote: _Exciter
Engines_]
The two exciter engines are each direct connected to a 250 kilowatt
direct current generator. Each engine is a vertical quarter-crank
compound engine with a 17-inch high pressure cylinder and a 27-inch
low-pressure cylinder with a common 24-inch stroke. The engines will
be non-condensing, for the reason that extreme reliability is desired
at the expense of some economy. They will operate at best efficiency
when indicating 400 horse power at a speed of 150 revolutions per
minute with a steam pressure of 175 pounds at the throttle. Each
engine will have a maximum of 600 indicated horse power.
[Sidenote: _Condensing
Equipment_]
Each engine unit is supplied with its own condenser equipment,
consisting of two barometric condensing chambers, each attached as
closely as possible to its respective low-pressure cylinder. For each
engine also is provided a vertical circulating pump along with a
vacuum pump and, for the sake of flexibility, the pumps are cross
connected with those of other engines and can be used interchangeably.
Public-domain text, read in full here on John Shaqi.
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