Improvements in Steam Superheating Apparatus and Appliances in connection therewith.
Year: 1892

page_text: Date of Application, 25th Aug., 1892-Accepted, 1st Oct., 1892
COMPLETE SPECIFICATION.
Improvements in Steam Superheating Apparatus and Appliances in
connection therewith.
We, Louis UHLER, Engineer, and HENRI CADISCHE, Engineer, both of
2 Birsigstrasse, Bâle, Switzerland, 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 :-
In constructing vertical steam superheaters with independent furnaces of the
kind described in the Specification to Patent No. 12372 of 1890, various incon-
veniences have shown themselves, and the present invention has for its object an
improved construction of such superheaters whereby the said inconveniences are
obviated.
Experience has shown that the vertical superheater requires the tubes to be
placed at least 2.40 metres away from the fire, in order to prevent their too rapid
deterioration.
As the tubes themselves are 2.40 metres high, it follows that the upper part of
the tubes is 4.80 metres from the fire; at this distance the temperature of the
combustion gases is hardly as high as that of the superheated steam, and in addition,
the transmission of heat takes place very imperfectly between gases when they
ascend vertically in contact with vertical tube surfaces.
In consequence hereof it has been necessary to construct such superheaters with
a relatively very great extent of heating surface, thereby greatly increasing the
cost thereof. In addition, the great total height of such superheaters (being about
6 metres) frequently causes great inconvenience and difficulty in properly locating
them, and furthermore, the lower ends of the vertical tubes, where they are formed
with joints, are the parts subject to the greatest heat and are consequently most
liable to deterioration, as the joints being brazed, are liable to give way under
excessive heating.
According to the present invention, these disadvantages are obviated by arranging
the tubes of the superheater horizontally; also, by the introduction of tubes not
connected with the superheater between the superheater tubes and the fire, we are
enabled to bring the said tubes nearer to the furnace, so that as the bottom tubes
are considerably lower than in the case of vertical tubes, they are subjected to a
much higher temperature, thus effecting a better utilisation of the furnace heat, and
consequently enabling the heating surface to be considerably reduced. By this
means the height of the superheater, its cost of installation, and the quantity of
fuel required for heating it, are all reduced to a corresponding extent.
On the accompanying drawings is shown a superheater constructed according to
our said invention.
Fig. 1 shews a longitudinal section, Figure 2 is a front view, and Fig. 3 is a cross
section.
Fig. 4 is a horizontal section on line X X Fig. 1.
Fig. 5 is a horizontal section through the front part of the superheater.
Fig. 6 is a horizontal section on line Y Y Fig. 3.
Fig. 7 is an enlarged detail view.
Figs. 8 and 9 are sections on lines Z Z and W W of Fig. 7, and
הד
16 is another charged detail view.
In the arrangement here shown, the tubes of the superheater are constructed in
a similar manner to "Field" boiler tubes placed horizontally, the concentric
tubes a b, being adapted, as in the Patent 1237200, to one or more boxes K, (two in
the present case) each being divided by a partition O into two compartments, of
which one, P communicates with the internal tubes b, while the other R commu-
nicates with..the outer tubes a, the steam-to-be superheated being introduced into
Another charged detail view.
In the arrangement here shown, the tubes of the superheater are constructed in
a similar manner to "Field" boiler tubes placed horizontally, the concentric
tubes a b, being adapted, as in the Patent 1237290, to one or more boxes K, (two in
the present case) each being divided by a partition O into two compartments, of
which one, P communicates with the internal tubes b, while the other R commu-
nicates with..the outer tubes a, the steam-to-be superheated being introduced into

page_text: the compartment P and consequently forced to pass first through the inner tubes b,
and then back again through the annular space between a and b, becoming super-
heated on its way, and then passing away through the chamber R.
The furnace A'is of ordinary construction, either with intermittent or continuous
firing, and the boxes or chambers K with their tubes a, b, are suitably supported
above it. The waste combustion gases escape through a descending pipe B Fig. 1,
communicating with the flue of the steam boilers, or they may be led into a sheet
iron chimney Cindicated in dotted lines in Figs. 1 and 2.
The furnace D and casing of the superheater is built of ordinary brickwork
strengthened by iron stays E, Figs. 2 and 5.
The furnace chamber is lined with fire bricks, which can be readily renewed.
The superheating tubes are supported at their closed ends, which are not fixed to
boxes K, by means of two tiers of moveable cast iron supports H' H¹ placed
closely side by side, which supports are of a width equal to the distance from centre
to centre of the tubes, and can be removed at will for the passage of instruments
for the withdrawal and replacing of tubes when required. The tubes are supported
at the middle of their length by means of a tubular metal bearer I Figs. 1 and 3,
and by moveable struts K K Figs. 1 and 10, which are pushed into their place
from the front, before placing the supports H¹ in position. It will be seen that the
arrangement is such that one or more defective tubes can be removed without
requiring the operator to enter the furnace, as was requisite with the vertical
arrangement of the tubes, necessitating the stoppage for a long time of the super-
heater's action, in order to allow the furnace to cool down. The front side of the
furnace is partly closed by a sheet iron door L' and partly by brickwork O'. The
tubular bearer l'has air admitted to it at P Fig. 3 and it cummunicates at the other
end with a passage R' formed in the brickwork, opening underneath the furnace
grate. This arrangement has for its object both to keep the bearer cool and to
supply hot air to the furnace.
In the roof of the tube chamber are formed openings S¹ S¹ Figs. 1 and 4, the
number and area of which are calculated to give a suitable direction of the hot
combustion gases, in order that the tubes may be more or less uniformly heated
thereby.
An important feature of the improved superheater consists in the employment of
tubes TT that are not connected to the superheater, and the object of which is to
preserve the lower rows of superheating tubes from excessive heating.
. Experiments have shown that, in a group of superposed horizontal tubes, only the
three lower rows can become red hot by excessive licating.
Consequently by the application of three rows of protective tubes T' all excessive
heating and oxidation of the superheating tubes will be avoided, and these will
therefore be much more durable. The tubes T can be of any description; they
are supported on the one hand by the casting H, which, together with the brick-
work m also supports the boxes K of the superheater tubes, and on the other hand
they are supported by moveable supports H³ of cast iron, the construction of which
is shewn at Figs. 7, 8 and 9.
These moveable supports are secured in such manner as not to allow the entrance:
of air between them.
The moveable supports H³ are held at bottom by a bearer s³ secured so as to be
removeable.
The two upper sets of moveable supports H'H' are held in the same manner by
a bearer s¹.
The tubes T¹ can be rapidly removed and replaced from the outside without
stopping the working of the superheater. Cold air enters them from one end so
as to cool them to a certain extent and also to provide a further supply of hot air
which passes from the other end of the tubes into flues N¹ N* and enters the
furnace, above the fire through nozzles U U' for the purpose of consuming the
smoke.
1.
The fire-brick arch V₁ which is built below the tubular bearer I can be readily.

page_text: reconstructed when worn out; it serves to protect the bearer I' against excessive
heat from the fire.
When a superheater with independent fire is used in combination with boilers
worked at a high pressure, there will frequently be carried, along with the steam,
water charged with solid impurities, owing to priming.
These solid impurities would be precipitated to the lower sides of the super-
heating tubes and would accumulate therein so as to eventually prevent the
circulation of the steam through the tubes, so that these, being no longer in contact
with steam, would rapidly burn away.
For the purpose of preventing such solid impurities from passing into these
tubes, there is placed at any convenient point between the steam boilers and the
superheater, a water and mud separator, or purifier, cousisting of a recipient K²
provided with two branch pipes ¹² separated by a partition k³ provided with
pendent tubes k, so that the steam entering through the branch will first pass
downwards with considerable velocity through the tubes k on its way to the
branch 2, and the solid impurities will consequently be precipitated from the steam
to the bottom of the receptacle K². This is provided with a mud cock G¹at
bottom, through which the accumulated impuritics can be discharged from time to
time.
The tubes T might of course be replaced by solid iron bars, of about the same
diameter as the tubes. These tubes T', or the bars replacing the same, may also
be applied with advantage to steam superheaters placed in the furnaces or flues of
steam boilers.
Steam superheaters constructed according to the Patent No. 1237200 can be
readily altered into superheaters of the above described construction.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. A steam superheater with independent furnace and with superheating tubes
similar to Field" boiler tubes, connected to one or more boxes K with two
compartments, the superheating tubes being arranged horizontally so as to enable
them to be readily removed and replaced from the outside, while a series of
protective tubes T¹ or metal bars are provided between the bottom superheating
tubes and the fire, for protecting these tubes against excessive heating, and enabling
them to be brought nearer the fire, whereby a better utilisation of the heat is
effected and the heating surface and height of the superheater is diminished,
substantially as described.
2. The herein described construction of apparatus for drying and purifying the
steam before it enters the superheater.
3. The herein described arrangement of fire brick arch V', tubular metal
bearer l' and moveable supports for supporting the tubes at their middles.
4. The moveable supports H and H for the superheating tubes, whereby the
removal of these is facilitated substantially as described.
5. The described arrangement for cooling the tubes T¹ and the bearer I' by
supplying them with cold air which, on becoming heated, is conducted to the
furnace.
6. The use of the protective tubes T'or of bars in lieu thereof, to any description
of superheater whether with independent furnace, or used in combination with the
furnace or flues of a steam boiler, substantially as described.
Dated this 25th day of August 1892.
ABEL & IMRAY,
Agents for the Applicants.