IMPROVEMENTS IN STEAM BOILER AND OTHER FURNACES
Year: 1877

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, for the Invention of "IMPROVEMENTS IN
STEAM BOILER AND OTHER FURNACES," A communication from abroad by
Robert Kermit McMurray, of the City, County, and State of New York,
United States of America.
Sealed the 14th May 1878, and dated the 18th December 1877.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark
at the Office of the Commissioners of Patents on the 18th December 1877.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Mid-
dlesex, Patent Agent. "IMPROVEMENTS IN STEAM BOILER AND OTHER FURNACES."
[A communication from abroad by Robert Kermit MoMurray, of the City, County,
and State of New York, United States of America.]
The object of this Invention is to provide effective means for economizing the
consumption of fuel in the furnaces of steam boilers, and of reheating or blast
furnaces, and for the prevention of smoke by the admission of a proper supply of
heated air to the gases evolved by combustion; and further, to effect a reduction
in the time and expense heretofore required for the renewal and repair of bridge
walls employed in boiler settings.
According to this Invention a hollow metallic fire-bridge is provided, preferably
composed of cast-iron sections, the width of which fire-bridge is about equal to the
thickness of the bridge wall upon which it is set, and its length slightly greater
than the inside width of the furnace and combustion chamber, so as to project into
each of the side walls thereof for a distance of, say, one inch.
The fire-bridge consists of three principal members, to wit, a fire-plate, a back or
base plate, and a dispersing plate, which are constructed and connected sub-

page_text: stantially as follows:-The plate which I designate the fire-plate, by reason of the
fact that it is designed to receive the direct heat of the fire, is corrugated through-
out its entire length, so as to increase its strength and allow for expansion and
contraction under changes of temperature, and its thickness is sufficiently great, say,
about three-fourths of an inch, to adequately resist blows from a slice bar, to which,
from its position, it is necessarily exposed. It is provided with a light bottom
flange, which rests upon the bridge wall, and thence rises vertically for about two-
thirds of its height, at which point it is inclined at an angle of forty-five degrees,
or thereabout, extending to a horizontal top surface, being longitudinally corru-
gated, as before stated, at all points except upon its bottom flange.
The bottom flange might be made separate if preferred, and fitted between the
fire-plate and back plate, or cast upon the back plate; but I deem the arrangement
shown more desirable, as affording a more uniform distribution of metal in the
several portions of the bridge.
The back or base plate is a light angular plate, substantially conforming in the
relative position of three of its sides to the fire-plate, and in addition projecting
downwardly from its upper surface in reverse direction to but at a similar angle
with its rising incline, and terminating in a horizontal flange or foot.
The plates are connected by bolts passing through thimbles or distance pieces
so as to form a hollow case or trough; and a dispersing or diffusing plate, perforated
throughout its entire length with numerous small orifices, is inserted in lips or
grooves formed in the edges of the top surface of the fire-plate and the bottom
flange of the back plate respectively.
The connecting bolts are arranged in two series, one vertical, passing through
the
upper surfaces of the plates, and the other horizontal, and as near as convenient
to their lower edges.
A series of air-supply openings are formed in the back plate as near as practicable
to its base, above which a horizontal deflecting flange extends along the side of
said plate adjacent to the fire-plate, the width of said flange being about one half
inch less than the distance between the two plates, and the edge of the flange being
curved correspondingly with the corrugations of the fire-plate, so as to maintain a
uniform width of opening between the flange and plate for the entire length of the
bridge.
In practice the dispersing plate may be formed in separate sections instead of in
a single piece, both for greater convenience in casting, and to reduce the expense of
renewal in the event of breakage.
In the application of the improved fire-bridge to a boiler setting it is placed upon
an ordinary brick-bridge wall without being embedded therein, the lower edge of
the fire-plate being slightly below the level of the grate-bars; and its ends are
closed by the side walls of the setting, or by metal plates fitted therein, the latter
plan being preferable, as in such case by the removal of the plate at either end the
fire-bridge may be removed whenever desired by drawing it out longitudinally
through the opening in the side wall without disturbing any of the brickwork of
the setting, and it can be replaced in a similar manner. If however its ends be
closed by the side walls, it is only necessary, for the purpose of removal, to take
out a sufficient number of bricks at one end to form an opening large enough for
its withdrawal, and this can be done in a very short time, and without the necessity
of awaiting the cooling down of the furnace and combustion chamber. This
capability of ready removal and replacement for renewal or repair constitutes an
important feature of the Invention as compared with the ordinary brick bridge
walls, or with devices embedded therein or in the setting.
A register or valve of any suitable construction is to be inserted in the wall or
plate at one or both ends of the bridge to enable the supply of air to be accurately
regulated thereto as circumstances may require. And in some instances I propose
to supply the air by a pipe or pipes passing through the furnace or combustion
chamber, so that it may be admitted to the fire-bridge in a heated state.

page_text: In the operation of the bridge the fresh air, which is admitted thereto at one or
both ends beneath the back plate, enters the space between the back plate and fire-
plate through the supply openings, and is deflected by the flange against the heated
surface of the fire-plate and passes upward along the space between the two plates.
In its traverse therein it is heated by its impingement upon the entire inner surface
of the hot fire-plate, and is introduced in a minutely divided condition into the
combustion chamber at a temperature closely approximating that of the gases
escaping from the furnace, with which it mingles immediately upon their passage
over the top of the bridge, thoroughly oxidizing the inflowing carbonic oxide,
and effecting a complete combustion, with a corresponding economy of fuel and
prevention of smoke. Its advantage moreover in durability over the ordinary fire-
brick bridge will be apparent to the practical steam engineer, inasmuch as the fire-
plate only is exposed to the direct action of the fire, and from its material and form
of construction is possessed of greater power of resistance to the destructive
influences brought upon it.
In the event of repair the entire bridge can be removed, a new plate be inserted,
and the bridge replaced in position with much less labor and expense, and with far
greater expedition than is practicable in the case of a brick bridge wall.
Although the Invention has been described as connected with steam boiler
settings it is not intended to limit the improvements to this particular use, as it is
applicable to any furnace employing a bridge wall.

page_text: :
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alexander Melville Clark in the Great Seal Patent Office on the
18th June 1878.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent.
"IMPROVEMENTS IN STEAM BOILER AND OTHER FURNACES."
A communication from abroad by Robert Kermit MoMurray, of the City, County,
and State of New York, United States of America.
The object of this Invention is to provide effective means for economising the
consumption of fuel in the furnaces of steam boilers and of reheating or blast
furnaces, and for the prevention of smoke by the admission of a proper supply of
heated air to the gases evolved by combustion; and further, to effect a reduction in
the time and expense heretofore required for the renewal and repair of bridge walls
employed in boiler settings.
To these ends the improvements consist in combining with the furnace and
combustion chamber of a steam boiler a hollow metallic fire-bridge formed of a 1
series of plates united together and resting upon the top of a bridge wall of the
ordinary construction without being embedded therein; into which hollow bridge
fresh air in properly graduated proportions is introduced, and within which it is
heated to a temperature approximating to that of the gases escaping from the
furnace, and is thence delivered in a minutely divided condition to said gases as 2
they enter the combustion chamber.
The improvements further consist in such construction of said fire-bridge as to
provide ample resistance against blows or shocks and the effects of expansion and
contraction, as well as to render it capable of being readily and quickly removed
from its position in the setting, renewed or repaired at a comparatively slight 2
expense, and replaced in position for further operation.
The improvements claimed are herein-after fully set forth.
In the accompanying Drawings,-
Figure 1 is a vertical longitudinal central section through the setting of a return
tubular stationary boiler with the improvements applied.
3
Figure 2 is a transverse section through the fire-bridge at the line 1-1 of
Figure 3.
Figure 3, a longitudinal section at the line 2-2 of Figure 2.
Figure 4, a plan or top view of the fire-bridge.
And Figure 5, a plan view of one of the dispersing plates detached.
According to this Invention a hollow metallic fire-bridge is provided, preferably
composed of cast-iron sections, the width of which fire-bridge is about equal to the
thickness of the bridge wall upon which it is set, and its length slightly greater than
the inside width of the furnace and combustion chamber, so as to project into each
of the side walls thereof for a distance of, say, one inch.
The fire-bridge consists of three principal members, to wit, a fire-plate A, a back
or base plate B, and a dispersing plate C, which are constructed and connected
substantially as follows:-The plate A, which I designate the fire-plate, by reason
of the fact that it is designed to receive the direct heat of the fire, is corrugated
throughout its entire length, so as to increase its strength and allow for expansion
and contraction under changes of temperature; and its thickness is sufficiently
great, say, about three-fourths of an inch, to adequately resist blows from a slice
bar, to which, from its position, it is necessarily exposed. It is provided with a
light bottom flange a, which rests upon the bridge wall, and thence rises vertically
for about two-thirds of its height, at which point it is inclined at an angle of forty-
five degrees, or thereabout, extending to a horizontal top surface, being longi-
tudinally corrugated, as before stated, at all points except on its bottom flange.
The bottom flange might be made separate if preferred, and fitted between the
fire-plate and back plate, or cast upon the back plate; but I deem the arrangement

page_text: shown more desirable, as affording a more uniform distribution of metal in the
several portions of the bridge.
The bottom plate B is a light angular plate, substantially conforming in the
relative position of three of its sides to the plate A, and in addition projecting
downwardly from its upper surface in reverse direction to but at a similar angle
with its rising incline, and terminating in a horizontal flange or foot b.
The plates A and B are connected by bolts a¹ passing through thimbles or
distance pieces a³, so as to form a hollow case or trough; and a dispensing or
diffusing plate C, perforated throughout its entire length with numerous small
orifices, is inserted in lips or grooves formed in the edges of the top surface of the
fire-plate A and the bottom flange 6 of the plate B respectively.
The connecting bolts a' are arranged in two series, one vertical, passing through
the upper surfaces of the plates A and B, and the other horizontal, and as near as
convenient to their lower edges.
A series of air-supply openings 61 are formed in the plate B as near as practicable
to its base, above which a horizontal deflecting flange b* extends along the side of
the plate B adjacent to the plate A; the width of said flange being about one-half
inch less than the distance between the two plates, and the edge of the flange being
curved correspondingly with the corrugations of the plate A, so as to maintain a
uniform width of opening between the flange and fire-plate for the entire length
of the bridge.
In practice the dispersing plate may be formed in separate sections, as shown,
instead of in a single piece, both for greater convenience in casting and to reduce
the expense of renewal in the event of breakage.
In the application of the improved fire-bridge to a boiler setting it is placed upon
an ordinary brick-bridge wall without being embedded therein, the lower edge of
the fire-plate A being slightly below the level of the grate bars; and its ends are
closed by the side walls of the setting, or by metal plates fitted therein, the latter
plan being preferable, as in such case by the removal of the plate at either end
the fire-bridge may be removed whenever desired by drawing it out longitudinally
through the opening in the side wall without disturbing any of the brickwork of
the setting, and it can be replaced in a similar manner. If however its ends be
closed by the side walls, it is only necessary, for the purpose of removal, to take out
a sufficient number of bricks at one end to form an opening large enough for its
withdrawal, and this can be done in a very short time, and without the necessity
of awaiting the cooling down of the furnace and combustion chamber. This
capability of ready removal and replacement for renewal or repair constitutes an
important feature of the Invention as compared with the ordinary brick bridge
walls, or with devices embedded therein, or in the setting.
A register or valve of any suitable construction is to be inserted in the wall or
plate at one or both ends of the bridge to enable the supply of air to be accurately
regulated thereto as circumstances may require. And in some instances I propose
to supply the air by a pipe or pipes passing through the furnace or combustion
chamber, so that it may be admitted to the fire-bridge in a heated state.
In the operation of the bridge the fresh air, which is admitted thereto at one or
both ends beneath the back plate, enters the space between the back plate and fire-
plate through the supply openings b', and is deflected by the flange b* against the
heated surface of the fire-plate, and passes upward along the space between the two
plates. In its traverse therein it is heated by its impingement upon the entire inner
surface of the hot fire-plate, and is introduced in a minutely divided condition into
the combustion chamber at a temperature closely approximating that of the gases
escaping from the furnace, with which it mingles immediately upon their passage
over the top of the bridge, thoroughly oxidising the inflowing carbonic oxide, and
effecting a complete combustion, with a corresponding economy of fuel and
prevention of smoke. Its advantage moreover in durability over the ordinary fire-
brick bridge will be apparent to the practical steam engineer, inasmuch as the fire-
plate only is exposed to the direct action of the fire, and from its material and

page_text: form of construction is possessed of greater power of resistance to the destructive
influences brought upon it.
In the event of repair the entire bridge can be removed, a new plate be inserted,
and the bridge replaced in position with much less labor and expense, and with far
greater expedition than is practicable in the case of a brick bridge wall.
Although the Invention has been described as connected with steam boiler
settings it is not limited to this particular use, as it is applicable to any furnace
employing a bridge wall.
Having described the nature of the said Invention, and the manner of performing
the same, I declare that what I claim as the Invention to be protected by the
herein-before in part recited Letters Patent is,-
1st. The combination in a steam boiler, reheating and blast furnace, setting of a
furnace, a combustion chamber communicating therewith, an intermediate bridge
wall, and a series of plates connected together to form a hollow metallic fire-bridge,
which rests on without being embedded in the bridge wall, and is removable
therefrom through an opening in the side wall of the setting, substantially as set
forth.
2nd. The combination in a fire-bridge for furnaces of a corrugated fire-plate, a
back plate connected thereto, and provided with a series of air-supply openings,
and a perforated diffusing plate, substantially as set forth.
3rd. The combination in a fire-bridge for steam boiler furnaces of a fire-plate,
a back plate, interposed distance pieces, and connecting bolts, substantially as set
forth.
4th. The combination with a fire-plato of a back plate having a series of air-
supply openings near its bottom, and a longitudinal deflecting flange projecting
into the space between the fire-plate and back plate above the air-supply openings,
and of less width at all points than the distance between said plates, substantially
as set forth.
5th. The combination, substantially as set forth, of a fire-plate, a back plate, and
a diffusing plate, connected together and forming a hollow metallic fire-bridge,
which is bevelled or inclined in opposite directions towards its top, and is provided
with a lower series of air-supply openings, and an upper series of air discharge
openings.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set
my hand and seal, this Eighteenth day of June, in the year of our Lord
One thousand eight hundred and seventy-eight.