Forced Draft System for Steam Generators.
Year: 1899

page_text: Date of Application, 21st Oct., 1899-Accepted, 25th Nov., 1899
[Communicated from abroad by THE BABCOCK AND WILCOX COMPANY, of New York,
United States of America, Steam Boiler Manufacturers.]
Forced Draft System for Steam Generators.
I, WALLACE FAIRWEATHER, C.E., of 62, Saint Vincent Street, in the City of
Glasgow, Chartered Patent Agent, do hereby declare the nature of this invention
and in what manner the same is to be performed, as communicated to me, to bo
particularly described and ascertained in and by the following statement:-
The invention consists in a forced-draft system for steam generators, in which
air is forced into an air-tight compartment containing a steam generator; the
air surrounding the generator being maintained under a pressure slightly above
the atmosphere.
The supply for combustion is directed and circulated from the closed compart-
ment to the furnace through ducts or tubes arranged within the boiler casing
adjacent to the course of the escaping products of combustion.
In the accompanying drawings an embodiment of the invention is shown in
connection with a water-tube generator, Figure 1 representing a plan view partly
in section.
Figure 2 a similar front view, and
Figure 3 a sectional side view of the generator and closed compartment.
A is the air-tight compartment in which the generator is placed. B a fan-
blower for forcing air therein, and C a siphon-gage communicating with the
interior of the compartment and the outside atmosphere for indicating the differ-
ence in air pressure without and within the compartment.
The generator shown is of the inclined water-tube type, enclosed within a
casing in the usual way.
In the present embodiment of the invention an open air duct D is arranged
within the casing of the top of the generator, into which the air-supply for com-
bustion enters. This duct D communicates with a series of vertical pipes a,
arranged within a combustion chamber E, located at the side of the generator,
which forms a passage for the heated products of combustion from the combustion
chamber of the furnace K to the uptake H.
The vertical pipes a are fixed within this chamber E, to partition plates or
sheets b, as shown in Figures 1 and 2, and communicate with a chamber d that
extends to the base of the generator and opens into the ash pit h of the furnace.
The direction of the air. taken from the compartment A and conveyed to the ash
pit h through the duct D, pipes a and chamber d, is indicated by the arrows, as
shown in Figures 1 and 2, and in the direction of the waste products of com-
bustion from the furnace to the uptake indicated by the arrows, as shown in
Figure 3.
In this system, the air from combustion is wholly derived from the compressed
air in the closed compartment and can therefore be easily and efficiently regulated
by suitable dampers in the air ducts, and by the degree of compression in the
compartment.
The temperature of the air may be reduced when heated above a desired degree,

page_text: by slightly opening or jarring the ash pit doors at the base of the generator, or
by admitting air from the compartment by a suitable device at any other point in
its transit through the ducts.
Heretofore in forced draft systems, arrangements have been proposed for supply-
ing boiler furnaces with air driven directly by a fan along the heated surfaces
presented by the boiler, and into especially designed chambers adjacent to the fire-
room, into which a portion of the boiler is projected, and into chambers affixed
to the boilers adjacent to the furnaces and air admitted to the latter, both above
and below the fire, by means of valves alternately operated, and I therefore make
no claim to the same; but I am not aware that a generator has heretofore been
placed wholly within an air-tight compartment, in which air under pressure is
maintained and heated in a distinct chamber, and from which the supply for
combustion is taken and by which the defects of former systems, met with in
practice, have been remedied.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, as communicated to
me, I declare that what I claim is;.
-
In a forced draft system for steam generators, the combination of an air-tight
compartment, into which air is forced and maintained under compression, with a
steam generator and an independent air-heating device, wholly enclosed in said
compartment, the air supply for combustion being transferred by means of suit-
able ducts or passages leading from the compartiment to the air heating device
and from the latter to the furnace, substantially as described.
Dated this 20th day of October 1899.
WALLACE FAIRWEATHER.