Improvements in Water-tube Steam Boilers.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
Improvements in Water-tube Steam Boilers.
I, GUILLAUME ARNAUD NUSSBAUM, of 29, Ludgate Hill, in the City of London,
Engineer, do hereby declare the nature of this invention to be as follows:-
This invention has reference to a construction of steam boiler in. which one
or each side of the combustion chamber, or each combustion chamber if there
is more than one, is formed by an element comprising an upper horizontal steam
and water vessel (hereinafter called a steam drum), a lower horizontal water
vessel, and one or more upwardly extending rows of pairs of concentric straight
tubes the outer of which are water tubes and connect the top of the lower water
vessel to the bottom of the steam drum, and the inner of which are flue tubes
and connect the bottom of the lower water vessel to the top of the steam drum,
the arrangement being such that the hollow column of water between the two
tubes of each pair of concentric tubes is heated both externally and internally
by flame and hot gases that pass around and between the outer tubes and are
caused to pass upward through the inner tubes, and that the steam drum and
water vessel are braced together and strengthened in such a manner that they
can be made lighter than usual and yet capable of withstanding high pressure.
The steam drum and water vessel may be of circular section, or of plano-circular
section, that is to say with circular sides and flattened top and bottom. The
water and flue tubes, which are of comparatively large diameter, may be of
cylindrical or conical shape, or one tube of each pair may be cylindrical and the
other conical so that the water space between them is of gradually increasing
cross sectional area from bottom to top where it is in free communication with
the water vessel and steam drum respectively.
Steam boilers having elements of the kind described can be constructed in
various forms. In one arrangement, two elements of the kind described are
arranged vertically at opposite sides of a fire-grate and within a casing, the top
of the combustion chamber between the two elements being closed by a cover or
roof of refractory material. The two lower water vessels are each supported upon
suitable bearings between fire-brick walls the space between which forms a
passage through which flame and hot gases after passing between the water
tubes can pass downward to the space below the water vessel and enter the flue
tubes up which they will then ascend. The steam drum and water vessel are
connected by an external downtake tube arranged at the front or rear, or at
both the front and rear of the boiler casing.
5 In a modified arrangement, two elements of the kind described are inclined
towards one another so that the two steam drums are near together.
Steam or compressed air may be injected into the bottom of the flue tubes

page_text: for cleaning purposes and also for producing a strong draught through such
tubes.
Water and flue tubes arranged as described act as stays to the several steam
drums and water vessels thereby giving great strength and elasticity to the boiler
and allowing the use of comparatively thin plates for high pressure.
Furthermore by reason of the flame and hot gases passing in a downward
direction after passing between the water tubes, unequal heating and stress of
the various parts of the boiler are to a large extent prevented, and the opening
of the fire doors will not cause injury to the boilers as the inrush of cold air will
be checked by the return down flame.
The furnaces of boilers according to this invention may be lined with fire
bricks which may be provided with air passages in order that heated air may be
admitted above or below or both and below the grate.
The improved boiler elements may be enclosed in a casing of brickwork, or
in a jacketed casing made of thin sheet metal with a filling of non-conducting
material such as asbestos, ashes or the like, or with an air passage for the double
purpose of preventing radiation of heat into the surrounding air and of heating
the air required for combustion.
By arranging the concentric water and flue tubes vertically or nearly so and
connecting them to upper and lower vessels connected by downtakes as described,
I obtain a more effective and accelerated water circulation than has heretofore
been usual in other constructions of boilers in which concentric water and flue
tubes have been employed.
The water and flue tubes may be secured in place by screwing or expanding
in the ordinary way. In order however to provide between each tube end and the
plate in which it is fixed a joint that shall be more elastic and fluid tight at all
temperatures than is possible with an ordinary screwed or expanded joint, each
tube end may advantageously be formed with a short surrounding sleeve or flange
that is expanded or screwed into the plate to which the tube end is to be fixed
and between which and the tube is an annular space. Into this space fluid under
pressure can in the case of the flue tubes enter and assist in holding the sleeve or
flange against the wall of the hole in which it is placed and also prevent over-
heating of the tube end. The sleeve or flange may be formed by turning over
the end of the tube, or by thickening the tube end and forming a deep circular
recess therein. A filling piece may be temporarily inserted in the annular space
between the tube end and its surrounding sleeve or flange to prevent closing of
the said space during the expanding of the outer end of such tube.
Tubes having flanged ends as described may advantageously be used in boilers
of various constructions both as water and flue tubes.

page_text: he same is to be performed to be particularly described and ascertamicu
y the following statement:-
-
This invention consists of improvements in and relating to water tube steam
oilers as I shall now describe with reference to the accompanying drawings.
Figs. 1 and 2 are respectively a partial cross sectional view and a partial end
levation showing one construction of water tube steam boiler according to this
nvention.
In this example one, side only of the combustion chamber of the boiler is
ormed by a steam generating element comprising an upper horizontal steam
and water vessel a (hereinafter called a steam drum), a lower horizontal water
vessel b, and upwardly extending rows of pairs of concentric straight tubes of
which the outer ones care water tubes and connect the top of the lower water
vessel to the bottom of the steam drum a, whilst the inner ones are flue
lubes and connect the bottom of the lower water vessel b to the top of the steam
drum a, the arrangement being such that the hollow column of water in the
space e between the two tubes c and d of each pair of concentric tubes is heated
both externally and internally by flame and hot gases that pass around and between
the outer tubes c and are caused to pass afterwards upward through the inner
tubes d, and that the steam drum a and the water vessel bare braced together
and strengthened in such a manner that they can be made lighter than usual and
yet capable of withstanding high pressure. Some of the water tubes at the ends
of the element and located outside the boiler casing may be without flue tubes
and serve as downtake tubes. Or a large downtake tube such as c¹ (Fig. 2), located
at one or at each end of the boiler, may connect the lower part of the steam
drum a to the water vessel b.
The steam drum a and the water vessel b may be of circular section as indicated
by dotted lines in Fig. 3, or, as shown in full lines, of plano-circular section-
that is to say, with circular sides and flattened top and bottom. The water tubes c
and the flue tubes d.which are of comparatively large diameter are preferably
cylindrical but they may be of another shape or other shapes provided they be
straight.
The steam generating element thus constructed is supported in an inclined
position upon a suitable bearing f within a casing g and over a firegrate h
so as to form one side and the roof of the combustion chamber h¹ the other side
of which is formed by the front side of the said casing which is formed with
openings that are provided with doors m and n respectively and serve for
the introduction of fuel and for gaining access to the space o above the steam
drum a and at the base of the chimney or uptake p. The steam drum a is
arranged to practically close the lower end of the chimney p so that flame and
hot gases after passing between the water tubes c must descend and enter the
The rear
space whence they flow through the flue tubes d to the chimney 2.
lower portion of the casing y may be provided with a door q to allow of ready
access to the space q. r is a partition to aid in cutting off direct communication
between the interior of the casing g and the base of the chimney p except through
5 the flue tubes. s is a wall of refractory material to protect the lower water vessel b
from direct contact with the solid fuel on the fire-grate h. t is the feed water
inlet and u the steam outlet.
By the construction described it will be seen that ready access can be gained
to the upper end of the flue tubes c for examination or repair, and that the said
Also that ready
50 tubes can be conveniently withdrawn through the opening 1.
access can be gained to the lower ends of the flue tubes.
Fig. 3 shows partly in cross section and partly in end elevation another con-
struction of boiler according to this invention. In this example two separate
steam generating elements of the kind described are inclined towards one another
55 so that the two steam drums a are near together and that the two elements form
between them the two sides and roof of the combustion chamber h³.

page_text: .
Each of the two lower water vessels 6 is supported at its ends by suitable
bearings between firebrick walls or between a firebrick walls and the casing g,
The flame and hot gases, after passing between the water tubes c, can pass down-
ward to the space below the water vessel and enter the flue tubes & up
which they will ascend on their way to the chimney or uptake the lower end
of which is closed by the two steam drums a. The steam drum and the water
vessel of each element are connected by one or more external downtake tubes w
which may be arranged at the front or at the rear of the boiler casing. or both
at the front and at the rear thereof as may be desired. t is the feed water inlet
and the steam outlet as before.
Steam or compressed air may be injected into the lower ends of the flue tubes
for cleaning purposes and also for producing a strong draught through such tubes.
Nozzles 6 are for this purpose shown arranged below some of the flue tubes d
in Figs. 1 and 3.
The casing g enclosing the steam generating element or elements may be of
brickwork, or, as shown, a jacketed casing made of thin sheet metal with a
filling of non-conducting material such as asbestos, ashes, or the like, or with
an air passage for the double purpose of preventing radiation of heat into the
surrounding air and of heating the air required for combustion.
To facilitate the escape of steam from the upper ends of the water tubes and
prevent or reduce liability to priming, the upper end of each water tube may
have fitted to it a sheet metal guide tube (Fig. 3) that extends upwards to or
a little above the normal water level in the corresponding steam drum a.. Also
in order that the generation of steam in the several water tubes c may be rendered
more or less uniform notwithstanding their different distances from the combustion
chamber, the cross sectional area of the annular water spaces e may be gradually
decreased from the combustion chamber outwards; this may conveniently be
done by making the flue tubes in the successive rows, of different diameters (see
Fig. 1), the tubes of largest diameter being used in the outmost row and the
tubes of smallest diameter in the inmost row, the tubes in intermediate rows.
being of intermediate diameters. In order to facilitate complete combustion
of the mixture of hot gases and air within the combustion chamber before such
mixture can come into contact with the comparatively cool water tubes and be
reduced to a temperature at which complete combustion thereof cannot be effected,
there may be arranged above the fire grate and below the tubes as shown in
Fig. 3, a hood (which forms no part of the present, invention) consisting of
inclined side slabs y of refractory material formed with perforations there-
through, and a non-perforated. top slab 1, the perforations being preferably at
right angles to the water tubes. When the boiler is in action, the hood will
be raised to and maintained at a high temperature such as will facilitate complete
combustion of the mixture of hot gas and air whilst within the combustion
chamber and the highly heated gases will escape therefrom in directions approxi-
mately at right angles to the water tubes.
By arranging the concentric water and flue tubes at a considerable angle to
the horizontal as shown and connecting them to upper and lower vessels con-
nected by downtakes as described, I obtain a very effective and rapid water
circulation whilst by making each element complete in itself, each can expand
and contract independently of the other.
The water and flue tubes c and d respectively may be secured in place by
screwing or expanding in the ordinary way. In order, however, to provide between
each tube end and the plate in which it is fixed a joint that will be more elastic
and fluid tight at all temperatures than is possible with an ordinary screwed
or expanded joint, each tube end may be formed with a short surrounding sleeve
or flange 2 that is expanded, as shown in Fig. 4, or screwed, as shown in Fig. 5,
into the plate 3 to which the tube end is to be fixed and between which flange
and the tube body is an annular space 4. Into this space fluid under pressure

page_text: an, in the case of the flue tubes, enter and assist in holding the sleeve
gainst the wall of the hole in which it is placed and also prevent overheating
f the tube end. The sleeve or flange may be formed by turning over the end
f the tube, as shown in Figs. 4 and 5, or by thickening the tube end and
A filling piece may be temporarily
crming a deep annular recess therein.
nserted in the annular space between the tube end and its surrounding sleeve
r flange to prevent closing of the said space during the expanding of the outer
end of such tube.
Tubes having flanged ends as described may advantageously be used in boilers
of various constructions both as water and flue tubes."
Fig. 1 illustrates means, forming no part of the present invention, for enabling
each water tube c and flue tube to be withdrawn and replaced, or a new one
substituted for it, from the top of the boiler without removing adjacent tubes.
The upper end of each flue tube is made flaring and fits in a carefully turned
Hanged metal cap 5 that has a conical periphery fitting a hole in the upper
tube plate 7 of the steam drum, the hole 6 being sufficiently large to allow of
the withdrawal therethrough of the corresponding water tube, which preferably,
as shown, is expanded at its upper end to fit the hole in the lower tube plate 8
of the steam drum. The cap 5 is provided on its lower side with an annular
groove whose walls can be pressed by the steam against the flue tube and the
periphery of the hole respectively and thereby ensure a steam tight joint with
these parts.
Onto the lower end of each flue tube d is screwed a cap or
closure 5 that is similar to 5 and fits in a corresponding conical hole in the
lower tube plate 9 of the water vessel b, the said cap 5ª being shaped so that it
can be turned by a key or spanner. Both ends of each water tube are provided
with shoulders to fit against the corresponding tube plates and are expanded to
fit the holes thereof.
Fig. 3 shows another way but which likewise forms no part of the present
invention, of securing the ends of the water and flue tubes in the corresponding
tube plates. In this case the upper end of each water tube c is fixed in the
corresponding tube plate 8, as in Fig. 1, but the lower end of the tube is coned
to fit a correspondingly coned hole in the upper tube plate 10 of the water
vessel b. The lower end of each flue tube is screwed into the corresponding
lower tube plate 9, whilst on its upper end there is screwed a flanged metal
cap 5 which fits into the hole 6 in the upper tube plate of the steam drum and
is constructed like the caps 5, 5ª shown in Fig. 1.
I am aware that it has heretofore been proposed to connect a single upper
steam and water vessel to two lower water vessels by two groups of concentrically
arranged water and flue tubes arranged at opposite sides of the combustion
O chamber, but such construction, which I do not claim, differs from mine inasmuch
as the upper steam and water vessel being common to the two groups of tubes,
is liable to be subjected to severe and injurious strains as the result of unequal
expansion and contraction of the various tubes, whereas by making the steam and
water vessel connected to each group of tubes separate from that connected
5 to the other group of tubes, so that each steam generating element is complete in
itself, as hereinbefore described, such strains are to a large extent, if not wholly,
prevented.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
50 I claim is:-
65
1. A water tube steam boiler comprising a single steam generating element
and a casing with chimney or uptake, these parts being constructed and arranged
substantially as hereinbefore described with reference to Figs. 1 and 2 of
the drawings annexed.
2. A water tube steam boiler comprising two separate steam generating elements
and casing with chimney or uptake, these parts being constructed and arranged

page_text: substantially as hereinbefore described with reference to Fig. 3 of the drawings
annexed.
3. A steam boiler according to the preceding claims in which means are pro-
vided for injecting steam or compressed air into the lower ends of the flue tubes
for cleaning purposes or for producing a strong draught through the said tubes,
substantially as described.
4. The improved water tube steam boilers hereinbefore described with reference
to and shown in Figs. 1 and 2, and in Fig. 3 of the drawings annexed.
For the Applicant,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C.,
Chartered Patent Agent.