Improvements in Steam Superheaters.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
Improvements in Steam Superheaters.
I, CARL JACOBI. of 14, König Strasse, Wannsee, near Berlin, in the Empire of
Germany, Engineer, do hereby declare the nature of this invention to be as
follows:
In order to obtain dry steam in tubular boilers many propositions have been
hitherto made. For instance the furnace gases have been allowed to pass through
the heating tubes of superheating vessels, said heating tubes being surrounded by
steam. Tubular boilers have also been produced in which the steam has to pass
through groups of tubes or worms, which are arranged in special wide heating
tubes, as it was found that the former arrangements had an unsatisfactory result.
In the last named kind of superheater however, practical drawbacks were
found, consisting in that, in spite of the protective rings arranged in the wide
heating tubes in proximity to the admission or inlet place of the furnace gases,
there took place at the high temperature of such furnace gases (1000 to 1200° ('.)
a rapid destruction of the groups of tubes or worms at those places which were
directly exposed to the action of the thin flames, and which even the best material
can not permanently withstand.
By the present invention in order to avoid these drawbacks the furnace gases
are conveyed through a water surrounded connecting pipe to the superheater
pipes in the small quantities in which they are employed for the superheating,
and the superheater tubes are made with the largest admissible diameter and
arranged in the steam space or water space of the boiler.
In this arrangement, furnace gases (and in this consists the essential point of
the invention) are conveyed to the superheater tubes only in such quantity and
under the withdrawal of a large part of their heat, that when they spread them-
selves over the separate parts, any overheating or rendering incandescent of the
latter in the steam space of the boiler is prevented as only a relatively small
part of the furnace gases so far as the size of the fire tube admits, comes into
action.
For introducing a suitably small part of the furnace gases into the body of the
superheater, which for example may lie in the steam space of the boiler, a fire
tube attached to the tube plate of the fire box, is employed, which fire tube dis-
charges into a chamber in the rear tubular head or cap of the superheater.
Smoke tubes lead from this chamber through a front tube head into the smoke
box.
For the attachment of the regulating cap, the rear tube cap is provided with
a central tubular nozzle which opens into the front chamber of the rear tube cap
and from this chamber superheater pipes which enclose the smoke tubes lead to
a chamber in the front tube cap from which a nozzle or short tube conveys the
superheated steam to the pipes conveying steam to the cylinders.
The body of the superheater when arranged in a locomotive boiler. for instance.
in the steam space, is surrounded by a thin protective casing, in the interior of

page_text: which, steam may enter through lateral slits so that the superheater tubes are
surrounded by boiler steam.
The object of this protective casing is to prevent water encountering the tubes
in order not to withdraw too much warmth therefrom. The whole body of the
superheater is inserted in the steam space of the boiler through an opening in
the tube plate of the smoke box, and it takes the place in this way of the ordinary
connecting tube between the regulator cap and the steam conveying pipes.
In order to increase the withdrawal of heat during the course of the fire gases
to the superheater, the fire tube serving for conveying the necessary quantity of
fire gases, may be formed as a ribbed body. Or in place of one tube several tubes
may be employed.
For that matter, in this arrangement is it possible by the selection of a
suitable width of the fire tube to convey to the body of the superheater the exact
quantity of heat which is necessary for heating the steam up to about 200
to 300° C. without destroying the parts affected owing to a too high temperature
of the furnace gases.
Of course the arrangement may also be utilised in boilers arranged on other
systems. A separate regulation is unnecessary, as the limit of temperature of
the steam to be superheated may be determined in the above way by the size of
the heating surfaces of the fire tube encountered by the water. The regulation
of this limit of temperature lies thus in the system itself.
In order to interrupt the passage of the furnace gases, a shut off slide is
arranged at the end of the superheater in the smoke chamber.
Dated this 18th day of December 1899.
W. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.
I, CARL JACOBI, Engineer, of 14, Königstrasse, Wannsee, near Berlin, in the
Empire of Germany, 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:-
-
To obtain dry steam in tubular boilers or boilers of the locomotive or marine
type many varied proposals have already been made; for example the furnace
gases have been passed through tubes surrounded by steam in the superheating
chambers. Tubular boilers have also been constructed in which the steam is
passed through a battery of tubes or coils which are arranged in specially wide
heating tubes from which it appears that the former arrangement did not give
satisfactory results.
In the latter method of construction also practical defects became apparent,
which arose from the fact that in spite of the protecting rings placed near to the
point of entrance of the furnace gases into the wide heating tubes in consequence
of the high temperature of these gases (1000-1200° C.) a rapid deterioration of
the battery of tubes, or of the coils, occurred at those places which were exposed
to the direct action of the flames, which even the best material cannot long
resist.
In the present invention, to avoid these defects a portion of the furnace gases
is conducted through a connecting tube surrounded by water, to the superheater
tubes in a quantity sufficient to superheat the steam yet the superheater tubes
are made of the greatest possible diameter and placed within the steam space of

page_text: the boiler in order not to reduce the temperature too much by allowing too much
heat to be conducted away.
In the present invention,-and herein consists its essential importance-the
furnace gases are conducted to the superheater tubes in such quantity only and
after the abstraction of the greater part of their heat, that when they are dis-
tributed over the separate parts it is impossible for these to become red hot in
the steam space of the boiler for only a proportionately small quantity of the
furnace gases limited by the section of the connecting tube is thus made use of.
By way of example the apparatus is illustrated as applied to an ordinary
locomotive boiler.
Fig. 1. Longitudinal section through boiler showing the superheater in position.
Fig. 2. Longitudinal section through superheater (enlarged scale).
Fig. 3. End view of the same.
Fig. 4. Is a modification.
Fig. 5. Detail view of special damper.
To conduct a suitably small quantity of the furnace gases to the body of the
superheater which is situated in the steam-space of the boiler, a tube a is provided
connected at one end with the tube plate of the fire-box and at the other with a
chamber formed with the back tube-chest b of the superheater. From this
chamber flue tubes e lead through the front tube chest d into the smoke box.
For attaching the regulator pipe e the back tube chest is provided with a
central pipe which opens into the steam chamber of the back tube chest b from
this chamber there pass superheating tubes f which surround the flue tubes
into a chamber in the front tube chest box d from which a branch pipe conducts
the superheated steam to the supply pipes g of the cylinders.
The body of the superheater is surrounded by a thin protecting cover h to the
inside of which steam can enter through slits formed in its sides so that the
superheater tubes are surrounded with boiler steam. The object of this pro-
tecting cover is to prevent water splashing against the tube f and so drawing
away heat from the superheater.
The whole of the body of the superheater is introduced into the steam space of
the boiler through an opening formed in the tube plate of the smoke box and in
this way replaces the usual pipe connecting the regulator and the steam supply
pipes g.
In order to increase the quantity of heat abstracted during the passage of the
furnace gases to the body of the superheater, the tube a through which they pass
may be made with external ribs as shown. Instead of a single tube a being
employed a number of tubes may be used as shown in Fig. 4.
By this arrangement it is possible by choosing the right size of tube a to
supply to the superheater the exact quantity of heat required to superheat the
steam to about 200° or 300° C., and this without any fear of injuring any of the
parts employed by employing the furnace gases at too high a temperature.
The invention can be applied to other descriptions of boilers.
Special adjustment is not necessary as the limit of the temperature of the
superheated steam can be regulated by the area of the heating surface of the
fire tubes in contact with the water. The regulating of this limit of temperature
is inherent in the arrangement itself.
In order to regulate or stop the passage of the furnace gases a sliding damper i
is provided at the front end of the superheater in the smoke box as shown in
Figs. 2 and 5.
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
I claim is:
1. A steam superheater heated by the products of combustion from the furnace
of the boiler characterised by leading such a quantity of the furnace gases as is

page_text: the water space of the boiler and of which the heating surface in contact with
the water is determined by the limit of temperature to which the steam is to be
superheated, and the superheater placed in either the steam space or the water
space of the boiler or in both substantially as described.
2. A superheater for steam constructed and arranged substantially as described
and shown.
1
1-11
1... C "
1000
WM. P. THOMPSON & Co.,
Manchester, Liverpool, London, & Birmingham,
Patent Agents.