Improvements in Furnaces of Internally Fired Boilers of the Lancashire, Cornish, and Galloway Types, and in the Furnaces of Externally Fired Boilers.
Year: 1896

page_text: Date of Application, 5th Feb 1808
Complete Specification Left, 4th Nov., 1896-Accepted, 5th Dec., 1896
Complete Specification Left, 4th Nov., 1896-Accepted, 5th Dec., 1896
PROVISIONAL SPECIFICATION.
Improvements in Furnaces of Internally Fired Boilers of the
Lancashire, Cornish, and Galloway Types, and in the Furnaces
of Externally Fired Boilers.
We, JOHN HARPER AND COMPANY, LIMITED, of Albion Works, Willenhall in the
County of Stafford, Ironfounders, and HENERY DEVONPORT, of the same address,
Engineer in the employment of the said company, do hereby declare the nature of
this invention to be as follows:-
This invention relates to furnaces of internally fired boilers of the Lancashire,
Cornish and Galloway types, and to the furnaces of externally fired boilers; and has
for its object to ensure a more perfect combustion of the fuel than takes place in
such furnaces as usually constructed, with consequently increased economy and
reduced emission of smoke.
A furnace constructed according to this invention, whether for an internally fired
boiler of either type above referred to, or for use with an externally fired boiler,
has the level of the fire bars or grate considerably below the level of the bottom of the
firing door, say from ten to fourteen inches below. This is effected in the case of an
internally fired boiler by placing the bars or grate low down in the flue, whereby
of course the grate is considerably narrower than those usually employed. A
number of perforations are formed through the firing door, through which streams
of air pass into the space between the top of the fuel and the crown of the flue
or underside of the boiler, as the case may be. In the case of an internally
fired boiler, the top of the bridge is a few inches higher than the bottom of the firing
door; and in the case of an externally fired boiler, the passage-way over the bridge
is formed by an opening on each side which extends from a point some distance from
the centre of the bottom of the boiler to the top of the flue on the same side. It is
preferred, in the case of an internally fired boiler, that the bridge shall have its
forward face inclined backwards at a considerable slant from the binder end of the
fire-bars or grate to the top of the bridge. In either case, the dead-plate may be
placed horizontally, and shallow cleaning door be provided immediately above the
level of the dead-plate through which a poker may be pushed to break up the fire,
and through which clinker may be raked out; or the dead-plate may be inclined
from the front end of the fire-bars or grate to the bottom of the firing door, to
admit of the fire being cleaned and the clinker raked out.
The fire-bars or grate being kept low down in relation to the firing door, a
considerable space is left between the top of the fire and the crown of the flue or
underside of the boiler, as the case may be, and the streams of air passing through the
perforations of the door pass horizontally right into the middle of the gases which
rise almost vertically until they reach nearly to the crown of the flue or the under-
side of the boiler, as the case may be. There is thus a thorough mingling of the air
and gases in the very hottest part where they can be mixed thoroughly, and a nearly
perfect combustion takes place, with the result of great economy in fuel and the
avoidance to a very great extent of the emission of smoke. Grates of much smaller area
than usual are employed. The small grate area which may be advantageously adopted

page_text: enables the grates of the internally fired boilers to be kept conveniently short, not-
withstanding that they are necessarily much narrower than usual owing to their low
position in the flues.
Dated this 4th day of February 1896
STEPHEN WATKINS,
Wolverhampton, Agent for the Applicants.
Improvements in Furnaces of Internally Fired Boilers of the
Lancashire, Cornish, and Galloway Types, and in the Furnaces
of Externally Fired Boilers.
We, JOHN HARPER AND COMPANY, LIMITED, of Albion Works, Willenhall in the
County of Stafford, Ironfounders, and HENERY DEVONPORT, of the same address,
Engineer in the employment of the said company, do hereby declare the nature of
this invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
This invention relates to furnaces of internally fired boilers of the Lancashire,
Cornish and Galloway types, and to the furnaces of externally fired boilers; and has
for its object to ensure a more perfect combustion of the fuel than takes place in such
furnaces as usually constructed, with consequently increased economy and reduced
emission of smoke.
A furnace constructed according to this invention, whether for an internally fired
boiler of either type above referred to, or for use with an externally fired boiler, has
the level of the fire bars or grate considerably below the level of the bottom of the firing
door, or (according to one form of the invention) a door is placed in position above
the firing door while the bottom of the firing door is level, as usual, with the bars or
grate. The former arrangement is the more convenient when, in the case of an internally
fired boiler, the floor plates cannot conveniently be set at a level to suit the latter
arrangement. In the case of an internally fired boiler, the grate is placed low down
in the flue, whereby of course it is considerably narrower than those usually
employed. A number of perforations are formed through the firing door when the
same is in position considerably above the grate, or through the other door above
referred to when the arrangement in which such door is used is employed, through
which streams of air pass into the space between the top of the fuel and the crown of
the flue or underside of the boiler, as the case may be. In the case of an internally
fired boiler, the top of the bridge is a few inches higher than the bottom of the
perforated door; and in the case of an externally fired boiler the passage-way over
the bridge is formed by an opening on each side which extends from a point some
distance from the centre of the bottom of the boiler to the top of the flue on the
It is preferred, in the case of an internally fired boiler, that the bridge
shall have its forward face inclined backwards, as is frequently the case, at a
considerable slant, from the hinder end of the fire bars or grate to the top of the
bridge. When, in the case either of an internally or externally fired boiler, the level
of the bottom of the firing door is considerably above the level of the fire bars or
grate, the dead-plate may be placed horizontally and a shallow cleaning door be
provided immediately above the level of the dead-plate through which a poker may
be pushed to break up the fire, and through which clinkers may be raked out; or the
dead-plate may be inclined from the front end of the fire bars or grate to the bottom
of the firing door to admit of the fire being cleaned and the clinker raked out.
same side.
The grate being low down in relation to the perforated door, a considerable
space is left between the top of the fire and the crown of the flue of an internally

page_text: fired boiler, and the streams of air passing through such door pass horizontally
into the middle of the space and thoroughly intermingle with the hot gases rising
from the fuel; and such intermingling taking place in the very hottest part of the
furnace where there is abundant room, and before the gases have attained any
considerable rate of flow along the flue, a nearly perfect combustion takes place,
with the result of great economy in fuel and the avoidance to a very great extent
of the emission of smoke. The air passing through the perforated door at a high
velocity right into the middle of the ascending gases from the grate does not come
in contact with the flue plates, but its movement breaks up the volume of the
ascending gases, and its own velocity is checked thereby, and ample time is thus
ensured for proper combustion. The gases do not rush horizontally towards the
bridge as they rise from the fuel, as is the case when a perforated firing door is
placed in the usual position in relation to the grate owing to the rush of air from
the perforations of the door along the top of the fire; but, rising at first in a
space along which there is no rush of air, attain a vertical velocity which carries
them to a considerable height, the gases rising from the sides of the grate curling
over under the crown of the furnace. As the fire burns through after stoking,
the gases commence to ascend from the grate at a much higher velocity, and
thereby check the flow of air through the perforated door, so that the control of
air is to a considerable extent automatic.
In the case of an externally fired boiler, the combined arrangement of the
perforations for the air and openings through the bridge for the passage of the
products of combustion causes a back flow from the bridge towards the front of
the furnace along the lower part of the boiler, with the effect that the gases rising
from the fuel pass up to the underside of the boiler, flow forwards therealong towards
the front of the furnace, divide at the front of the boiler, and are then carried along
with the draft towards and through the openings through the bridge. These move-
ments of the gases give ample time for thorough combustion with the streams of air
which flow in through the perforations at the front of the furnace. In this case, also,
the position of the perforations, by keeping the streams of air high up above the fuel
upon the grate, allows the gases to rise from such fuel a sufficient distance, before
meeting the streams of air, to enable them to attain a velocity in an upward direction
which will carry them up to the underside of the boiler.
Grates of much smaller area than usual are employed, and the small grate area
which may be advantageously adopted enables the grates of internally fired boilers to
be kept conveniently short, notwithstanding that they are narrower than usual owing
to their low position in the flues.
In order that the invention may be clearly understood, I will proceed to
describe convenient practical applications thereof by the aid of the accompanying
drawings.
Figure 1 shews, in longitudinal section, an application of the invention to the
furnace of an internally fired boiler.
Figure 2 is a transverse section taken on line x x of Figure 1; and
Figure 3 is a front end view of the furnace.
A is the furnace door plate, B the firing door, and C a shallow door through
which a poker may be pushed to break up the fire, and through which clinkers
may be raked out. D is the dead plate, E the grate, which is conveniently formed
of perforated slabs which reach from side to side of the grate and rest on the
curved sides of the boiler flue F. The fire-bridge G has its face which is towards
the grate slanted, as is frequently the case. Assuming that the flue tube F is
two feet nine inches diameter inside, the top of the grate E is about seven or eight
inches above the bottom of the inside of the tube, the bottom of the firing door
opening is about ten or eleven inches above the top of the grate, and the grate
itself, apart from the dead plate, is about three feet two inches long. The firing
door B is perforated with holes three-eighths of an inch diameter, the total area
of perforation being about six square inches per superficial foot of grate surface,
exclusive of deadplate, for ordinary quality of fuel and rate of combustion. The

page_text: highest of the perforations through the door are about six inches below the top of
the inside of the tube. An outside baffle plate is carried by the door, as shewn,
as a protection to the stoker against the heat. The door C consists conveniently
of a plain flat plate, and is held in place by passing ontward projections c at its
ends behind lugs d which are fixed to the plate A. Any ashes which fall into the
ashpit H are raked out through an opening a formed in the plate A. To give the
best economical results, common slack should be used, the grate being covered to
a thickness of three to four inches. The door C may be dispensed with, if desired,
and the dead-plate be inclined from the bottom of the firing door opening to the
level of the top of the grate, as indicated by broken lines, Figure 1, so that the
fire may be readily cleaned and the clinker raked out through such opening.
Figure 4 is the front end of a longitudinal sectional view of a modified form
of the invention as applied to the furnace of an internally fired boiler; and Figure 5
is a front end view of the furnace. In this modification, the grate is placed low down
in the tube, as in the modification described with reference to Figures 1, 2 and 3, but
an unperforated firing door J is arranged in the usual position in relation thereto,
and a perforated door B' is arranged thereabove, such latter door corresponding in
position and otherwise (except that it is not for use in firing, though it may be used
for such purpose, and is therefore conveniently smaller than the firing door) to the
door B previously described. In other respects the modification corresponds to the
application of the invention previously described with reference to Figures 1, 2 and 3.
While it is very much preferred, in using this modification, to employ the perforated
door B', perforations corresponding to those formed through such door may be formed
simply through the furnace front plate A', and the door B' be dispensed with. The
modification described with reference to Figures 4 and 5 is the one which is preferred,
when the floor plates can be arranged at a convenient height therefor.
Figure 6 shews, in longitudinal section, an application of the invention to the
furnace of an externally fired boiler, and Figure 7 is a transverse section taken on
line y y of Figure 6. The bottom of the firing door opening K is about nine inches
above the level of the grate L, and the dead-plate M is inclined from the bottom of
such opening to the level of the top of the grate, so that the fire may be readily
cleaned and the clinker raked out through the firing door. The firing door is
perforated in the manner of the firing door B previously described, and carries an
outside baffle-plate k'. The products of combustion pass away from the furnace
through openings N N each in position a considerable distance from the middle of
the bottom of the boiler around the circumference of the boiler.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
Furnaces of internally fired boilers of the Lancashire, Cornish and Galloway types,
and of externally fired boilers, constructed substantially as described.
Dated this 3rd day of November 1896
STEPHEN WATKINS,
Wolverhampton, Agent for the Applicants.
STEPHEN WATKINS,
Wolverhampton, Agent for the Applicants.