Saving of Fuel | | | | | |
| (computed) | ... | 4.4 | 9.5 | 8.9 | 9.9 |
|_______________________________|_______|_______|_______|_______|_______|

The table shows that the saving in steam consumption with 105 degrees of
superheat was 15.3 per cent and in heat consumption about 10 per cent.
This may be safely stated to be a conservative representation of the
saving that may be accomplished by the use of superheated steam in a
plant as a whole, where superheated steam is furnished not only to the
main engine but also to the auxiliaries. The figures may be taken as
conservative for the reason that in addition to the saving as shown in
the table, there would be in an ordinary plant a saving much greater
than is generally realized in the drips, where the loss with saturated
steam is greatly in excess of that with superheated steam.

The most conclusive and most practical evidence that a saving is
possible through the use of superheated steam is in the fact that in the
largest and most economical plants it is used almost without exception.
Regardless of any such evidence, however, there is a deep rooted
conviction in the minds of certain engineers that the use of superheated
steam will involve operating difficulties which, with additional first
cost, will more than offset any fuel saving. There are, of course,
conditions under which the installation of superheaters would in no way
be advisable. With a poorly designed superheater, no gain would result.
In general, it may be stated that in a new plant, properly designed,
with a boiler and superheater which will have an efficiency at least as
high as a boiler without a superheater, a gain is certain.

Such a gain is dependent upon the class of engine and the power plant
equipment in general. In determining the advisability of making a
superheater installation, all of the factors entering into each
individual case should be considered and balanced, with a view to
determining the saving in relation to cost, maintenance, depreciation
etc.

In highly economical plants, where the water consumption for an
indicated horse power is low, the gain will be less than would result
from the use of superheated steam in less economical plants where the
water consumption is higher. It is impossible to make an accurate
statement as to the saving possible but, broadly, it may vary from 3 to
5 per cent for 100 degrees of superhe