Improvements in Steam Generators.
Year: 1894

page_text: Date of Application, 19th Apr., 1894-Accepted, 9th June, 1894
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COMPLETE SPECIFICATION.
Improvements in Steam Generators.
I, PIETER SMIT, of Haringrliet No. 98, Rotterdam, in the Kingdom of Holland,
Shipbuilder and Engineer, 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 an improved construction of steam generator of water
tube type designed to afford a large heating surface and steam space and which
shall be economical in fuel, shall be easily accessible for repairs, and shall be light
and occupy a comparatively small space relatively to its power.
And in order that my invention may be readily understood I will now proceed to
describe the same by the aid of the accompanying drawings in which,
Fig. 1 shows partly in front elevation and partly in cross section,
Fig. 2 in longitudinal section,
Fig. 3 in plan with part of the casing removed, and
Fig. 4 in rear end elevation with the whole of the rear casing removed, a steam
generator constructed according to my invention.
Figs. 5, 6 and 7 are detail views hereinafter referred to.
Fig. 8 is a part cross section illustrating a modified construction.
1 is a horizontal cylindrical vessel traversed by a number of horizontal tubes 2
that are secured to the tube plates forming the ends of the said vessel, as in a
multi-tubular marine or locomotive boiler. The vessel 1 is supported at a
convenient height above the fire grate 3 by two pairs of inclined tubes 4 that are
connected to two longitudinal water vessels 5 arranged at opposite sides of the fire-
grate. These water vessels may advantageously be connected near their front and
rear ends by transverse water tubes 5*, 5. 6 is a horizontal cylindrical steam
vessel, hereinafter called the steam drum. It is arranged above the multi-tubular
vessel with which it is connected by short tubular connections 7. 8 is a smoke
box with uptake secured to the front end of the vessel 1 and provided with a door 9
as usual.
10 10 are bent tubes that connect the water vessels 5 with the lower side of the
steam drum 6, these tubes being arranged side by side in two rows so as to form
two tubulous walls that constitute the two sides or shell of the furnace chamber 11
and rear combustion chamber 12.
The rear end wall of the combustion chamber 12 is or may advantageously be
formed by a flat sided suitably stayed chamber 13, provided with an inlet 14 and
arianged to serve as a feed water heater which may be connected with the water
vessels 5 in any suitable manner. In the example shown, its lower side is formed
as a saddle seated upon the transverse water tube 5" whilst its upper end is secured
to the lower side of the steam drum, communication being effected between it and
the water vessels by oppositely arranged holes formed in both of them as shown
at 13. The rear end wall of the combustion chamber 12 may however be other-
wise formed if desired, and in the case of a double ended boiler constructed
according to my invention, may be even dispensed with, there being in this case one
combustion chamber common to two furnaces. In either of these alternative
constructions, the feed water, previously heated in an independent feed water
heater, or not, may be forced direct into one or other, or both, of the water
vessels 5.
The ends of the tubes 10 and 10" may advantageously be secured to the
water vessels 5 and steam drum 6 by hollow screw studs 15, one of which is shown
in the sectional detail view Fig. 5, the said stud being screwed through the metal
wall of the vessel or drum as the case may be, from the inside thereof, and into

page_text: the end of the tube, which is thickened, as shown, to receive it. To enable the
studs to be readily screwed into place, each of them may be formed with a notch 16
to receive a suitable key. The ends of the said tubes can however be secured in
place by any other suitable means if desired, as for example by contracting
them, fitting them in holes in the vessel or drum, and then expanding them in
place.
The holes in the water vessels and drum in which the hollow screw studs, or the
ends of the pipes 10 10° as the case may be, are secured, may advantageously be
pitched or arranged in a zig-zag manner as shown in Fig. 6 in order that each tube,
excepting the end ones, will partly fit into the space between the next adjacent
tubes on each side of it, so that the inner surface of the side walls will, in effect,
be of a corrugated form and present a large heating surface.
The furnace chamber 11 may extend around the top of the vessel I and below
the bottom of the steam drum 6 as shown in full lines in Fig. 1 or the upper part
of the said chamber may be cut off from the lower part by two longitudinal walls
or divisions 11* of refractory material arranged at a height corresponding to about
that of the water level in the vessel 1 as shown in dotted lines in Fig. 1.
The front end of the said furnace chamber may be closed with brickwork 11 as
shown, or by a plate metal front protected on the inner side from the action of the
fire by a lining of refractory material such as fire-clay. Or the metal front may
be made with double walls so as to form an air heating chamber the outer wall
being perforated to admit air to the upper part of such chamber and the inner wall,
which may be protected on the fire side by refractory material, being cut away
below the fire grate or formed at this part with an opening or openings to place
the chamber in communication with the ash pit. By this means air passing through
the said chamber to the grate by way of the ash pit will become heated. The
lower part of the outer plate would of course be provided with a door for gaining
access to the ash pit.
The rear end of the said furnace chamber is separated from the combustion
chamber 12 by a wall 17 of refractory material such as fire brick, formed with an
opening 17" through which flame, hot gases and products of combustion can enter
the combustion chamber on their way to the tubes 2 and smoke box 8, the lower
portion 17 of the said wall, which is made thicker than the upper portion, serving
as a fire bridge. The bottom of the combustion chamber is closed by any suitable
means; conveniently it may be closed by a plate 10° carried by angle irons as
shown. The space below the fire grate and combustion chamber are preferably
'closed all round except at the front 11 where it is in communication with the
external atmosphere, either directly as through opening 11° as shown at the right
hand side of Fig. 1, or through an air heating chamber such as described.
The side and rear end walls of the generator are enclosed in a casing which
may advantageously consist of two or more layers 18 of sheet metal with alternate
layer or layers 19 of asbestos as shown more clearly in the enlarged sectional
detail view Fig. 7.
The under side portion of the steam drum at the top of the combustion
chamber 12 may, if desired, be protected against the direct action of flame and hot
gases by refractory material such as asbestos; or it may be by alternate layers of
asbestos and sheet metal similar to that forming the casing of the generator.
The working of the steam generator thus constructed is as follows:-
Assuming the generator to be charged with water to a level of say about six
inches above the tubes 2 in the vessel 1, and that a fire is then lighted on the grate 3,
the temperature of the water in the vessel 1 will be gradually raised to the boiling
point by the action of the flame and hot gases upon the exterior of the vessel 1 and
the interior of the tubes 2 and the steam thereby generated will pass through the
connections 7 into the steam drum 6 when it can be led away for use through any
suitably arranged steam pipe. The water in the tubes 10 10 will at the same
time be gradually raised to the boiling point and owing to its comparatively small
volume, and being strongly heated in a confined space the mixture of water and

page_text: steam in the said pipes will be of such a density that it will tend to occupy a
higher level than in the vessel 1, the result being that the mixture of water and
steam will be caused to ascend the tubes and be projected into the steam drum
whence the water will flow back through the connections 7 into the vessel 1 where
it will be further subjected to heat, its place in the tubes 10, 10 being taken by
other water from the vessels 5. In this way an effective circulation of water will
be set up in the pipes 10 10. Furthermore as the back pair of pipes 4 will be
more strongly heated than the front pair, a circulation of water may also take place
between the vessel 1 and the water vessels 5, water descending the front pair of
pipes and ascending the rear pair though this is not of primary importance as the
water converted into steam in the vessel 1 and connected tubes will be replaced by
fresh feed water admitted to the water vessels 5. To prevent the water and steam
issuing from the upper ends of the pipes 10, 10 being projected into the centre of
the steam drum and thereby cause priming, a longitudinal baffle plate 10° may
advantageously be fixed over the upper open ends of each row of pipes 10, 10" as
shown.
The water vessels 5 and drum 6 are preferably of comparatively large size, say
of about 2 and 2 feet in diameter respectively, so as to admit of their being
readily entered when desired for which purpose they are each provided at one end
with a manhole 20 normally closed by a door 21. Their ends may be constructed
and strengthened in any suitable way.
As will be obvious a water tube boiler according to my invention can be
variously modified without departing from its main characteristics. Thus instead
of connecting the upper ends of the rows of tubes 10 10 to the lower side of the
steam drum they may be connected to the upper side of the vessel 1 as shown in
Fig. 8 but I consider the first construction the more advantageous of the two.
Also the generator can be made double ended with a central combustion chamber
common to the two furnaces as hereinbefore mentioned.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. In a steam generator the combination and arrangement substantially as
described, of a multi-tubular vessel such as 1-2, longitudinal water vessels arranged
at opposite sides of the furnace grate, tubes connecting the water vessels with the
said multi-tubular vessel and serving to support the latter above the furnace grate,
and water tubes such as 10, 10 connecting the said water vessels with the lower
side of a steam drum supported above and in communication with the said multi-
tubular vessel, or with the upper side of the said multi-tubular vessel, and arranged
to form the side walls of the furnace chamber as set forth.
2. A steam generator of the kind referred to in the preceding claim constructed
with a wall such as 17 arranged to divide the furnace chamber from a combustion
chamber located at the rear of the multi-tubular vessel 1 and the sides of which
are formed by water tubes the said wall being formed with an opening 17" for the
passage of flame and hot gases from one chamber to the other substantially as
herein described.
3. My improved steam generator constructed and arranged substantially as
hereinbefore described with reference to and shown in Figs. 1 to 4 inclusive of the
drawings annexed, or modified according to Fig. 8, whether or not the rear end
wall of the combustion chamber be formed as a feed water heater as set forth.
Dated this 19th day of April 1894.
Dated this 19th day of April 1894.
For the Applicant,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.