Year: 1899

page_text: We, HENRY CHARLES PLATTS and THOMAS LOWTHER, both of 23, Lime Street,
London, E.C., Engineers, do hereby declare the nature of this invention to be
as follows:-
This invention has reference to steam boilers of the kind in which there are
located within the water-containing shell of the boiler a furnace tube or flue, or
more than one, containing the fire grate or grates, and other tubes or flues
through which the products of combustion and hot gases from the furnace or
furnaces return to or towards the front of the boiler, and our object is to so con-
struct and arrange such boilers as to improve the water circulation therein and to
utilize the gases flowing through the return tubes or flues, and whose temperature
is lower than that of the products of combustion and gases within the furnace
tubes or flues, for imparting heat to the cooler water within the boiler, instead
of allowing them to pass through parts of the boiler (and especially those parts
immediately above the furnace tubes or flues) containing more highly heated
water, whose temperature is liable to become thereby lowered rather than raised,
in consequence of the water surrounding the return tubes or flues having a higher
temperature than the products of combustion and hot gases passing therethrough.
In carrying out this invention, the furnace tube or flue (or each of them, if
there be more than one) and the return tubes or flues are so relatively arranged
within the shell of the boiler that the return tubes or flues shall not be as is
usual above or to a large extent above the furnace tubes or flues and consequently
in the hottest parts of the boiler, but wholly or mainly either at one or both
sides of or below or at one or both sides of and below the highest part or parts
of the furnace tube or flue or tubes or flues the arrangement being such that the
water in contact with the return tubes or flues shall be the less heated portions
of the water in the boiler and such as will usually on coming into contact with
the walls of the return tubes or flues be at a lower temperature than the products
of combustion and hot gases then passing through the return tubes or flues.
When return tubes or flues of large diameter or width are employed, we some-
times arrange within them other tubes, open at their ends to the water-space of
the boiler, so that water circulating through these tubes may have its temperature
raised by the products of combustion and hot gases impinging upon the exteriors
of the tubes during their passage through the return tubes or flues.
According to one construction, within a cylindrical outer shell there is concen-
trically placed a cylindrical furnace tube, corrugated or not, and having within
it a grate or grates, with the necessary bridge or bridges.
Within the annular space between the exterior of the furnace tube or flue
and the inner surface of the shell, there are provided at two opposite sides of the
boiler, a couple of flues whose upper and lower ends constitute tube plates in
planes radiating it may be from the axis of the furnace tube or flue, whilst the

page_text: outer and inner walls of the said return flues constitute arcs of circles whereof
the axis of the furnace tube or flue is or may be the centre. The upper tube plate
of each return flue is, at its highest part, not above the level of the highest part
of the furnace tube or flue.
Within the return flues there are water-circulating tubes whose ends are suit-
ably fixed in the respective tube plates of those flues, these water tubes having
their axes in circular ares struck it may be from the axis of the furnace tube
or flue. The return flues are or may be suitably stayed to the furnace tube or flue
and to the shell of the boiler, or otherwise as may be desired.
According to a modification, the furnace tube or flue is fixed within a cylin-
drical shell, the axis of the said tube or flue being below that of the shell, and at
the respective sides there are provided between the furnace tube or flue and the
shell, return flues whose upper and lower ends are in planes radiating or approxi-
mately so from the axis of the shell; the inner walls of these flues are circular
arcs, struck from the axis, or approximately so, of the furnace tube or flue, and
their outer walls are circular ares struck from the axis or approximately so of
the shell. Within these return flues, water-circulating tubes are sometimes fixed.
Instead of providing return flues, such as just referred to, at each side of the
furnace tube or flue, we sometimes arrange the latter with its axis in a horizontal
plane below that containing the axis of the shell and in a vertical plane to one
side of that passing through the shell's axis, and we provide, at one side of the
so arranged furnace tube or flue, a return flue in which there are or may be fixed
tubes for the circulation of water.
In one construction of boiler containing two cylindrical plain or corrugated
flues having their axes in a common horizontal plane, above that containing the
axis of the shell, we provide three return tubes or flues, vir: A cylindrical return
tube or flue having its axis in the vertical plane containing that of the shell, but
located below the furnace tubes or flues, and two side flues whose inner and outer
walls are in circular arcs struck from the axis or approximately so of the flue.
The return flue or flues may be made of plain metal or of metal corrugated
transversely to the length of the flue or flues. When of segmental shape but
without water circulating tubes, the top and bottom plates of such flue or flues
may be of curved section.
In other ways the details of construction may be more or less varied, without
departing from the characteristic features of the invention.
Dated this 31st day of May 1899.
We, HENRY CHARLES PLATTS and THOMAS LOWTHER, both of 23, Lime Street,
in the City of London, Engineers, 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 has reference to steam boilers of the kind in which there are
located within the water-containing shell of the boiler a furnace tube or flue, or
more than one, containing the fire grate or grates, and other tubes or flues
through which the products of combustion and hot gases from the furnace or
furnaces return to or towards the front of the boiler, and our object is to so con-

page_text: struct and arrange such boilers as to improve the water circulation therein and to
utilize the gases flowing through the return tubes or flues, and whose temperature
is lower than that of the products of combustion and gases within the furnace
tubes or flues, for imparting heat to the cooler water within the boiler, instead
of allowing them to pass through parts of the boiler (and especially those parts
immediately above the furnace tubes or flues) containing more highly heated
water, whose temperature is liable to become thereby lowered rather than raised,
in consequence of the water surrounding the return tubes or flues having a higher
temperature than the products of combustion and hot gases passing therethrough.
In carrying out this invention, the furnace tube or Hue (hereinafter called the
furnace flue) or each of them, if there be more than one, and the return tube or
Hlue or tubes or flues (hereinafter called the return flue or flues), are constructed
and arranged as we shall now describe with reference to the accompanying illus-
trative drawings wherein Fig. 1 shews partly in front elevation and partly in
cross section on the line xx of Fig. 2, and Fig. 2 in horizontal section on the
line yy of Fig. 1, one construction of steam boiler according to this invention.
In this construction, within the cylindrical outer shell a of the boiler there is
concentrically placed a cylindrical furnace flue b, which may be corrugated or
not, and has within it a grate e with the necessary bridge d the said shell being,
as well understood, set in suitable brickwork e with appropriate flues f leading
to a chimney g.
Within the annular space between the exterior of the furnace flue and the
inner surface of the shell a, there are provided at two opposite sides of the boiler,
a couple of return flues i that are made of segmental shape in cross section and
whose upper and lower ends ; made as flat plates may, as in the example shown,
be in planes radiating from the axis of the furnace flue, (though this direction
is not in all cases essential) whilst the outer and inner walls of the said return
flues constitute arcs of circles whereof the axis of the furnace flue is or may
be the centre. The upper end plate ; of each return flue is, at its highest part,
not above the level of the highest part of the furnace flue b.
When return flues i of large cross section are employed, we sometimes arrange
within them other tubes, open at their ends to the water-space of the boiler, so
that water circulating through these tubes may have its temperature raised by
the products of combustion and hot gases impinging upon the exteriors of the
tubes during their passage through the return flues.
Within the return flues i shown in Figs. 1 and 2 there are water-circulating
tubes whose ends are suitably fixed in the respective end plates j of those
flues, these water tubes having their axes in circular ares which may be struck,
as in the example shown, from the axis of the furnace flue b. The distance apart
of the two top tube plates j is made greater than the length of the longest water
tube k, so that such tubes can be removed from the tube plates, when necessary,
and withdrawn through a manhole in the upper part of the boiler. The return
flues i may be suitably stayed to the furnace flue and to the shell of the boiler.
in the example illustrated they are simply stayed or stiffened by stays of tee-
section but other suitable stays may be substituted.
With the arrangement described the products of combustion and hot gases from
the fuel on the grate pass along the furnace flue to a space or chamber n at
the rear of the boiler and then divide and pass along in the reverse direction
through the return flues i in passing through which the products of combustion
and hot gases impinge upon the exterior of the water tubes k thereby imparting
heat to the water therein, which rises to the upper parts of the boiler, cooler
water from the lower parts rising within the tubes to replace that which has
been heated.
The water circulating tubes k instead of being curved and connecting the top
and bottom of each flue, may be straight and arranged to connect the sides of the
flue, as shown in dotted lines in Fig. 1, such tubes then serving also as stays to
the sides of the flue.

page_text: Thus it will be seen that by our invention we are enabled to utilize to the best
advantage products of combustion and hot gases that have already imparted some
of their heat to water in higher parts of the boiler during their passage through
the furnace flue b, because we apply these now comparatively less heated gases,
in parts of the boiler where, as is well known, the temperature of the water is
lower than it is in immediate proximity to those parts of the furnace flue against
which the products of combustion and hot gases in the first instance more
directly act.
According to the modification shown diagrammatically in Fig. 3, the furnace
flue is so fixed within the cylindrical boiler shell a that the axis of the said
flue is below that of the shell, and at the respective sides there are provided
between the furnace flue band the shell a, return flues whose upper and lower
ends are shewn in planes radiating or approximately so from the the axis of
the shell; the inner walls of these flues are circular arcs, struck from the axis, or
approximately so, of the furnace flue b, and their outer walls are circular arcs
struck from the axis or approximately so of the shell a.
Within these return
flues, water-circulating tubes are sometimes fixed, but none are shewn in Fig. 3.
Instead of providing return flues, such as just referred to, at each side of the
furnace flue 6, the said flue b is sometimes arranged as in Fig. 4 with its axis
in a horizontal plane below that containing the axis of the shell a and in a
vertical plane to one side of that passing through the axis of the boiler shell a,
and there is provided at one side of the so arranged furnace or flue b, a return
flue in which there are or may be fixed water tubes & for the circulation of water.
Fig. 5 shows digrammatically in cross section a further modified construction of
boiler according to this invention. In this example the boiler shell a contains
two cylindrical flues (plain or corrugated) having their axes in a common hori-
zontal plane above that containing the axis of the said shell and three return
flues viza cylindrical return flue having its axis in the vertical plane contain-
ing that of the shell a, but located below the furnace flues b, and two segmental
shaped side flues whose inner and outer walls are in circular arcs struck from
the axis or approximately so of the said shell.
From the foregoing examples it will be seen that in all cases the furnace flue
or flues b and segmental shaped return flue or flues i are so relatively arranged
within the boiler shell a that the return flue or flues are not, as is usual, above
or to a large extent, above the furnace flue or flues and consequently in the hottest
parts of the boiler but are wholly or mainly at one or both sides of and below
the highest part or parts of the furnace flue or flues, that the water in contact with
the return flue or flues shall be the less heated portions of the water in the boiler
and such as will usually on coming into contact with the wall or walls of the
return flue or flues be at a lower temperature than the products of combustion and
hot gases then passing through the return flue or flues.
The return flue or Hues i herein before described, may be made of plain metal
or of metal corrugated transversely to the length of the flue or flues or of plain
metal provided with stiffening rings or equivalent devices. When the return flue
or flues is or are not provided with circulating tubes, the top and bottom plates
of such flue or flues may be of curved section. In other ways the details of con-
struction may be more or less varied, without departing from the characteristic
features of the invention.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed we declare that what
we claim is: -
1. A steam boiler comprising a longitudinal shell, one or more furnace flues
extending longitudinally therethrough, and one or more longitudinal return flues
of segmental cross section located between the main flue or flues and the adjacent
side of the said shell, the said return flue or flues being arranged below the highest

page_text: part of the said main flue or flues, substantially as described for the purpose
specified.
2. A steam boiler comprising a longitudinal shell, one or more main furnace
flues extending longitudinally therethrough, one or more longitudinal return
flues of segmental cross section located between the main flue or flues and the
adjacent side of the said shell and water tubes extending across the said return
flue or flues, substantially as described for the purposes specified.
3. Steam boilers of the kind herein referred to constructed arranged and operat-
ing substantially as hereinbefore described with reference to and shewn in Figs. 1
and 2; in Fig. 3; in Fig. 4, and in Fig. 5 of the drawings annexed.
For the Applicants,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.