n providing the efficiency of the
boiler and superheater is as high, as of a boiler alone, there is no
additional fuel required to generate steam containing a definite number
of heat units whether such units be due to superheat or saturation. That
is, if 6 per cent more fuel is required to generate and superheat to 100
degrees, a definite weight of steam, over what would be required to
produce the same weight of saturated steam, that steam when superheated,
will contain 6 per cent more heat units above the fuel water temperature
than if saturated. This holds true if the efficiency of the boiler and
superheater combined is the same as of the boiler alone. As a matter of
fact, the efficiency of a boiler and superheater, where the latter is
properly designed and located, will be slightly higher for the same set
of furnace conditions than would the efficiency of a boiler in which no
superheater were installed. A superheater, properly placed within the
boiler setting in such way that products of combustion for generating
saturated steam are utilized as well for superheating that steam, will
not in any way alter furnace conditions. With a given set of such
furnace conditions for a given amount of coal burned, the fact that
additional surface, whether as boiler heating or superheating surface,
is placed in such a manner that the gases must sweep over it, will tend
to lower the temperature of the exit gases. It is such a lowering of
exit gas temperatures that is the ultimate indication of added
efficiency. Though the amount of this added efficiency is difficult to
determine by test, that there is an increase is unquestionable.

Where a properly designed superheater is installed in a boiler the
heating surface of the boiler proper, in the generation of a definite
number of heat units, is relieved of a portion of the work which would
be required were these heat units delivered in saturated steam. Such a
superheater needs practically no attention, is not subject to a large
upkeep cost or depreciation, and performs its function without in any
way interfering with the operation of the boiler. Its use, therefore
from the standpoint of the boiler room, results in a saving in wear and
tear due to the lower ratings at which the boiler may be run, or its use
will lead to the possibility of obtaining the same number of boiler
horse power from a smaller number of boilers, with the boiler heating
surface doing exactly the same amount of work