Tubular Boiler Combined with Superheater.
Year: 1893

page_text: Date of Application, 2nd Dec., 1893-Accepted, 6th Jan., 1894
COMPLETE SPECIFICATION.
Tubular Boiler Combined with Superheater.
1, WILHELM SCHMIDT of Villa Henkel, Wilhelmshöhe near Cassel, in the
Province of Hesse-Nassau, Kingdom of Prussia, German Empire, 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 refers to combinations of steam-boilers and superheaters, and my
improvements in such combinations relate, first, to the arrangeinent of a tubular
boiler with coiled pipes, and, second, to the arrangement of a reservoir connected
with both ends of the boiler-coil, but with only one end of the superheater-coil, as
will be more fully described hereinafter.
Before entering into the details of the mode of construction of my improved
combination shown in the accompanying drawing, I think it necessary to give some
preliminary statements and explanations, in order to render the idea of the
invention perfectly clear and intelligible.
If steam is to be superheated to a temperature of about 300 degrees, the heating-
gases should have, as is well known, a temperature of at least from 500 to 600
degrees; the said former temperature will be reached best by arranging the super-
heater above the steam-generator, and exposing it to the furnace-gases of the same,
or, in other words, by arranging the superheater behind the steam-generator with
regard to the direction of the furnace-gases of the latter, and exposing it to a
zone of said gases, in which the temperature amounts to about 600 degrees. The
fire-gases need, thus, be cooled down by the boiler proper but to about 600 degrees,
whilst generally, in a steam-generator without superheater, an exhaust of the heat
down to 250 degrees is required.
As is well known, however, the greatest part of steam is generated in the fore-
part of a boiler, the remaining part, that is generated by exhausting the heat from
600° down to 250°, being of but small quantity, and necessitating comparatively
large heating-surfaces. Extended trials made with locomotive-engines have
proved, that about 50% of the whole of the steam in generated in the small part
surrounding the fire-box.
It results from this, that, when arranging a superheater for temperatures of about
300° above or behind a steam-generator, the latter not only may have a comparatively
small heating-surface, but should have such a one; and it will be seen, further,
that such boiler with superheater will yield at least the same effect, as a larger
boiler, that consumes a like quantity of fuel, since the furnace gases of both boilers
are exhausted in like degree, i.e. are escaping into the smoke-stack with the like
low temperature.
With regard to these facts, the boiler or. generator employed in my improved
combination is composed of coils or coiled pipes; these latter offer, in themselves,
certain advantages for every boiler-plant; they could, however, not be employed in
a more extensive degree, especially for large plants, as there arises in the practical
use of them serious drawbacks difficult to be overcome, as will be shown in the
following:
The main point to be considered in the use of coiled pipes as steam-generators
consist in the rapid circulation of the water or of the mixture of water and steam
within the coils. Such circulation is indispensably requisite; the same is con-
siderably hindered or delayed, however, by the great friction arising between the
water and the inner walls of the pipes, especially if the latter are of a somewhat

page_text: great length and of but small inner section. This disadvantage could be overcome,
seemingly, by using pipes with larger section; this section, however, necessitates
dimensions of such size, that it is nearly impossible to bend such pipes.
A perfect change, however, in all these circumstances occurs, if the tubular
boiler with coiled pipes is combined with a superheater. Therefore there is no
necessity for providing so large a heating surface for properly exhausting the heat
of the fire- or furnace-gases, but a boiler of but the fifth or sixth size with coils of
but small section will be sufficient for delivering the desired effect, even if a larger
horse-power is required. The heat of the fire need not be cooled by the heating-
surfaces of the boiler proper down to 250°, as this is performed by the superheater;
and the generation of steam will be a regular one, and free of shocks, as the
circulation of the water, or of the mixture of water and steam respectively, within
the short coil with its small section is a very active one.
The best effect, however, of the combination of a tubular boiler (with coiled pipes)
with a superheater, is attained by arranging a reservoir between the boiler-coil
and the superheating coil, for the purpose of separating water and steam. I have
shown this arrangement in the accompanying drawing, in which similar letters
denote similar parts throughout the different views, and in which;
Fig. 1 is a vertical section through the tubular boiler, the superheater, and the
said reservoir, and
Fig. 2 is a modified form of construction, the modifications referring to each of
the three parts.
The coil a of the tubular boiler, which is heated from the furnace b, is connected
by its two ends a a² with the under part of the vertical reservoir c, coil-end a
terminating directly into reservoir c, and coil-end a² by means of a bent tube a³
extending upwards within the reservoir, and terminating shortly below the surface
of the water contained in the same. The upper part of said reservoir forms a
steam-dome, and the saturated steam is led from the top of the dome by means of
pipe into the superheating-coil d, from which the superheated steam is led away
by pipe d².
The feed-water for the boiler, or for coil a respectively, enters the latter through
pipe a', and leaves the coil, after being heated and partly turned into steam within
the same, by the pipes a² and a³. The mixture of water and steam.now separates
within the reservoir c, the steam collecting within the dome, the boiling water
mixing with the feed-water, and heating the same.
The superheating coil d is arranged in the annular space between the outer walle
and the inner wall e, the furnace gases coming from the fire-place bare led through
the said space, and leave the whole apparatus at f. The steam to be superheated
is led through the superheating coil in a direction opposite to that of the furnace
gases.
It will be seen now, that the circulation of the water, or of the mixture of water
and steam respectively, within the boiler-coil, will be a very intense one, as, first,
the said coil is but short and has but a small section, and as, second, the contents
of coil a are constantly under the pressure of that part of the water-column within
reservoir e which is above pipe a¹; the generation of steam is, therefore, a very
intense and rapid one, as well as free of shocks, and the steam then enters the
superheating coils without the least addition of water, as the latter is perfectly
kept back by the reservoir. The water now circulates again and again through
the boiler-coil, so that the whole of the water within reservoir c is heated to a high
degree of temperature. This circulation will, as a matter of course, be the more
active the greater the difference in pressure between the water-column within the
reservoir and the water- and steam-column within the boiler-coil, and, further, the
less the resistance offered by the friction between the said water- and steam-column
and the inner walls of the boiler-coil. It results, herefrom, that the whole of the
water contained within, or entering, the said boiler-coil cannot be turned into steam
at so rapid a circulation, and it becomes thus, necessary to provide the reservoir c
for separating both parts of the water- and steam-mixture leaving the boiler-coil,

page_text: as our one Stemm can be permitted to enter the superneating-coll, whilst the hot
water must remain.
Concerning now the other mode of construction represented in Fig. 2, I have
shown in the same, first, that the uppermost part of the vertical boiler-coil a, or
that part situated between the coil a proper and the pipe a², may be formed into a
horizontal coil a', the purpose of which is to break the intense heat discharged by
the fire, so that the superheater is prevented thereby from becoming pervious.
The superheater itself has been composed in this mode of construction of a
number of horizontal coils, which are connected with each other to a continuons
passage. This connection of the coils, however, is made in such a way, that two
divisions are formed out of them; the first division, next to the boiler-coil, being
passed by the steam in a direction like that of the furnace-gases, the other
division being passed by the steam in the opposite direction, that is to say, opposite
to the direction of the furnace-gases; both divisions are connected by the bent
tube d³.
The reservoir, finally, is divided into two superposed parts by a horizontal plate c¹
having secured to it a vertical tube g extending downwards to the neighbourhood
of the bottom e². Another vertical tube, as, communicating with tube a', is arranged
in the same department of the reservoir, and extends upwards to the neighbourhood
of plate c' before mentioned.
The purpose of this arrangement is to separate and precipitate sediments and
the like contained in the feed-water, for preventing the boiler-coil from becoming
incrustated. The feed-water enters the upper part of the reservoir through the
funnel h, and the sediments separated by the heating of the water flow, together
with the latter, down into the under compartment of the reservoir through tube .9.
The water, then, in order to enter the opening of tube a, flows upwards again,
whilst the sediments remain back, and precipitate on the bottom c².
Having now particularly described and ascertained the nature of this inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. The combination, with a superheater, of a tubular boiler having coiled pipes,
for the purposes as described.
2. The combination, with a superheater, of a tubular boiler consisting of coiled
pipes, for the purposes as described.
3. The combination, with a superheater, consisting of coiled pipes, of a tubular
boiler, also consisting of coiled pipes, for the purposes as described.
4. The combination, with a superheater, of a tubular boiler, having coiled pipes,
said superheater being adapted to be heated by the gases of the boiler-furnace, for
the purposes as described.
5. The combination, with a superheater, of a tubular boiler, having coiled pipes,
said superheater being arranged above the boiler, and being adapted to be heated
by the gases of the furnace of the latter, for the purposes as described.
6. The combination, with a superheater, of a tubular boiler having coiled pipes,
the ends of the coil being connected with a reservoir adapted to close the circuit,
for the purposes as described.
7. The combination, with a superheater, of a tubular boiler, having coiled pipes,
the ends of the coil being connected with a reservoir adapted to close the circuit,
and to separate water and steam, for the purposes as described.
8. The combination, with a superheater, of a tubular boiler having coiled pipes,
the ends of the coil being connected with a reservoir adapted to separate the water
and steam coming from the boiler-coil, said reservoir having a steam-dome connected
with the superheater, for the purposes as described.
9. The combination, with a superheater consisting of coiled pipes forming a
vertical column, of a tubular boiler, also consisting of coiled pipes, the ends of the
boiler coil being connected with a vertical reservoir, adapted to close the circuit,
and to separate the water and steam coming from said boiler-coil, the upper part of

page_text: said reservoir forming a steam-dome, the latter being connected with one end of the
superheating-coil, for the purposes as described.
10. The combination, with a superheater consisting of coiled pipes forming two
superposed divisions, of a tubular boiler, also consisting of coiled pipes, the ends
of the boiler-coil being connected with a reservoir, adapted to close the circuit, and
to separate the water and steam coming from said boiler-coil, said reservoir having
a steam-dome connected with the under end of the under division of the super-
heating-coils, the upper end of said division being connected with the upper end
of the upper division of the superheating-coils, for the purposes as described.
11. The combination, with a superheater consisting of coiled horizontal pipes
forming two superposed vertical columns, of a tubular boiler consisting of an under
vertical coil and an upper horizontal coil connected with each other, the ends of
the boiler-coils being connected with a vertical reservoir forming a steam-dome in
its upper part, said reservoir being adapted to close the circuit of the boiler-coils,
and to separate the water and steam issuing therefrom, said steam-dome being
connected with the under end of the under column of the superheating-coils, the
upper end of said column being connected with the upper end of the upper
column of the superheating coils, the whole of the latter being arranged above the
boiler, and being adapted to be heated by the furnace-gases of the latter, for the
purposes as described.
12. The combination, with a superheater, of a tubular boiler having coiled
pipes a, the ends a' a² of the boiler-coil being connected with a vertical reservoir c
divided in two superposed compartments by a cross-plate c', the latter having a
pipe g extending into the under compartment, the upper compartment being adapted
to receive the fresh feed-water, for the purposes as described.
13. The combination, with a superheater, of a tubular boiler having coiled
pipes a, the under end a¹ of the boiler-coil being connected with the under part of
a vertical-reservoir e divided into two superposed compartments by a cross-plate c',
the upper compartment being connected with the upper end of said boiler-coil, and
being adapted to receive the fresh water, said plate c¹ having a pipe g extending.
downwards into the under part of the under compartment, the latter containing
also a pipe a communicating with pipe a', and extending upwards into the upper
part of the under compartment, for the purposes as described.
14. The combination, with a superheater consisting of coiled pipes (d) forming
a vertical column, of a tubular boiler also consisting of coiled pipes (a), the under
end (a) of the boiler-coil being connected with the under part of a vertical
reservoir (c) divided into two superposed compartments by a cross-plate (c), the
upper compartment of said reservoir being connected with the upper end (a²) of
the boiler-coil, and being adapted to receive the fresh feed-water, said upper com-
partment having a steam-dome, connected with one end (d) of the superheating-
coil, the bottom (c) of the upper compartment carrying a pipe (9) extending
downwards into the under part of the under compartment, the latter containing a
second pipe (a) communicating with the under end (a) of the boiler-coil, and
extending upwards into the upper part of the under compartment, for the purposes
as described.
Dated this 2nd day of Daramban 1902
WILHELM SCHMIDT,
By Geo. Thos. Hyde,
Agent for the Applicant.