IMPROVEMENTS IN AND CONNECTED WITH THE FURNACES OF STEAM BOILERS
Year: 1882

page_text: LETTERS PATENT to John Alexander MacLellan of Glasgow in the county of
Lanark North Britain Engineer for an invention of IMPROVEMENTS IN AND
PROVISIONAL SPECIFICATION left by the said John Alexander Mac Lellan
at the Office of the Commissioners of Patents on the 30th May 1882.
JOHN ALEXANDER MACLELLAN of Glasgow in the County of Lanark, North
Britain Engineer,
IMPROVEMENTS IN AND CONNECTED WITH THE FURNACES OF
STEAM BOILERS
"
"6
This Invention relates to steam boilers of the class made with horizontal
cylindrical shells, flat vertical ends and longitudinal tubes, and it consists of
improved furnace and other arrangements hereinafter described.
In carrying out the Invention the furnace space or fire box is formed in a
firebrick casing at one end of the boiler, the fire bars being at a level somewhat
above the lowermost tubes and having at their inner end a bridge between which
and the tube plate there is a space to allow the fire gases to descend to the lower-
most tubes. At the other end of the boiler there is a smoke box in which there is
placed a blast pipe with a lower part or "petticoat" piece arranged so as to induce
a sufficiently strong draught through the lower tubes. The firebrick furnace
casing is enclosed in an iron shell with an intervening space and the top of this
shell has one or more induction ventilating funnels fitted to it; whilst in the space
inside the shell there are deflecting plates or partitions arranged to cause the air
entering by the ventilators to be distributed over the firebrick furnace casing, so
that heat that might be lost by radiation may be taken up by the air and utilized,
as it is the air entering in this way, which supplies the furnace. The fire bars
consist of tubes (capable of being turned in their sockets) and some of the air
passes through them into the space between the bridge at their inner ends and the
tube plate, such air insuring ignition of the fire gases passing down over the
bridge. The remaining air enters the furnace partly through a door or valve and
partly between the fire bars, there being an ashes pan or plate fixed by preference
a few inches only below the fire bars; whilst below this ashes pan there is a
passage giving access to the tubes but ordinarily closed by a door at the outer end.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Alexander MacLellan in the Great Seal Patent Office
on the 29th November 1882.
JOHN ALEXANDER MACLELLAN of Glasgow, in the County of Lanark, North
Britain, Engineer, "IMPROVEMENTS IN AND CONNECTED WITH THE FURNACES OF
STEAM BOILERS
"
My said Invention relates to steam boilers of the class made with horizontal
cylindrical shells, flat vertical ends and longitudinal tubes, and it conists of
improved furnace and other arrangements hereinafter described.
"
to
In carrying out my Invention according to one modification, the furnace space or
fire box is formed in a firebrick casing at one end of the boiler, the fire bars being
at a level somewhat above the lowermost tubes and having at their inner end a
bridge between which and the tube plate there is a space to allow the fire
gases
descend to the lowermost tubes. At the other end of the boiler there is placed a
blast pipe with a lower part or "petticoat piece arranged so as to induce a
sufficiently strong draught through the lower tubes. The firebrick furnace casing
is enclosed in an iron shell with an intervening space or spaces, and the top of this
shell has one or more induction ventilating funnels fitted to it; whilst in the
space inside the shell there may be deflecting plates or partitions arranged to cause
the air entering by the ventilators to be distributed over the firebrick furnace
casing, so that heat that might be lost by radiation may be taken up by the air
and utilized, as it is the air entering in this way which supplies the furnace. The
fire bars consist of tubes (capable of being turned in their sockets) and some air
passes through them into the space between the bridge at their inner ends and the
tube plate, such air insuring ignition of the fire gases passing down over the bridge.
In other modifications the furnace details hereinbefore described are combined with
other varieties of boiler details; and in one case in which the boiler is of compara-
tively large size there are two furnaces the fire gases from which pass in one direction
through a lower portion of the tubes and return through the upper portion of the
tubes to a smoke box which is at the front of the boiler and over the furnaces.
And in order that my said Invention and the manner of performing the same
may be properly understood I hereunto append two sheets of explanatory drawings
to be hereinafter referred to and representing two modifications of my improved
boiler arrangements.
Figures, 1, and 2, on sheet, 1, of the accompanying drawings are transverse and
longitudinal vertical sections of one modification of my improved steam boilers;
and figures, 3, and 4, on sheet 2, are similar sections of a second modification. In
these drawings the same reference numerals are used to mark the same or like parts
wherever they are repeated.
In the modification shown in figures 1, and 2, the boiler comprises a horizontal
cylindrical shell, 5, with flat vertical end plates, 6, 7, and with tubes, 8, fixed in
the end plates. The furnace space or fire box, 9, is formed in a firebrick
structure, 10, which is external to the boiler and which is enclosed in a thin metal
shell, 11. The fire bars, 12, which in this modification are plain round tubes, and
can be turned in their end sockets, are at a level a little higher than that of the
lowest tubes, 8, and at their inner end there is a fire bridge, 13, between which
and the tube plate, 6, there is a space, 14, to allow a portion of the fire gases to have
access to the lowermost tubes. At the other end of the boiler there is a smoke
box, 15, surmounted by a funnel, 16, and to insure a sufficiently equal distribution
of the fire gases through all the tubes, 8, there is fitted at the bottom of the smoke
box, 15, a blast pipe, 17, the steam jet from which first enters the open conical
mouth at the bottom of a vertical pipe or petticoat piece, 18. The steam of the
jet, with the fire gases which it causes to pass from the lower tubes, 8, into the
bottom of the petticoat pipe, 18, issues from the top of this pipe as a second jet
which entering an upper conical mouth piece, 19, causes a draught thereinto from

page_text: the upper part of the smoke box, 15. The air for supplying the furnace is
principally drawn in down a pair of ventilating funnels, 20, and it enters through
them into the interior of the casing, 11, which encloses the firebrick furnace, 10.
Inside the casing, 11, the air picks up and utilises heat which would otherwise be
lost by radiation and it is made to pass through a tortuous route in the casing by
suitably arranged projecting parts of the brickwork, 10. The air thus heated finds
its way to the ash pit or space beneath the fire bars, 12, whilst a further supply of
air may be admitted through the fire door, 22. Under the fire bars there is a
movable ashes pan, 23, and if required this may be partly drawn out to admit a
further supply of air. At the inner end of the space under the firebars there is a
door or valve, 24, giving access to the tubes.
In the modification shown in figures 3 and 4, the boiler is of a larger class than
that shown in figures 1 and 2, but its main part is similar and consists of a
horizontal cylindrical shell, 5, with vertical end plates, 6, 7, and tubes, 8. There
are two furnaces, 9, which communicate directly with the lower portion only of the
tubes, 8, there being at the other end of the boiler a fire gas chamber, 25, through
which the fire gases pass from the lower to the upper tubes returning through the
latter to a smoke box, 26, which is above the furnaces, and which communicates
with a funnel, 16, directly above it or partly so. With the two furnaces, 9, the
well known advantage of alternate firing is available, whilst there is also the
advantage of the air being supplied to them in a heated state by utilising what
would otherwise be waste heat. The furnaces, 9, are constructed and arranged
substantially as herein before described with reference to the first modification, but
the casing, 11, enclosing them instead of being supplied with air directly through
ventilating funnels (20) receives the air through a duct, 27, communicating with a
casing, 28, which encircles the smoke funnel, 16, the air being primarily led into
the casing, 28, by ventilating funnels or otherwise. With this arrangement the
air will take up heat from the smoke funnel, 16, as well as preventing loss by
radiation from the furnaces.
Having thus particularly described my said Invention and the manner of
performing the same I have to state that I do not restrict myself to the precise
details herein described or delineated but that what I believe to be novel and
original and claim as the Invention secured to me by and in terms of the herein-
before in part recited Letters Patent is:
1. The combining or arranging of the parts of steam boilers and their furnace
accessories substantially in the improved manner hereinbefore described with
reference to figures 1 and 2, on sheet, 1, of the accompanying drawings.
2. The combining or arranging of the parts of steam boilers and their furnace
accessories substantially in the improved manner hereinbefore described with
reference to figures 3 and 4, on sheet 2, of the accompanying drawings.
3. The forming of a steam boiler furnace as an external firebrick structure
encased in a metal shell with spaces or passages for the air supplying the furnace
to take up and utilise otherwise waste heat, the parts being constructed arranged
and operating substantially as hereinbefore described.
In Witness whereof I, the said John Alexander MacLellan have hereunto set
my hand and seal this ninth day of October in the year of our Lord One
thousand sight hundred and sighty two
Witness.
EDMUND HUNT.
Patent Agent.
Glasgow.
J. A. MACLELLAN. (L.S.)