IMPROVEMENTS IN MULTITUBULAR STEAM BOILERS
Year: 1884

page_text: We, ALEXANDER SMITH, of Westbourne, Ibrox, and ALEXANDER SMITH of
85 Maxwell Road Pollokshields both of the firm of A. and W. Smith and'
Company of the Eglinton Engine Works, Glasgow, in the County of Lanark,
North Britain, Engineers, do hereby declare the nature of our said Invention
for "IMPROVEMENTS IN MULTITUBULAR STEAM BOILERS and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement :-
Our said Invention relates to steam boilers of the various kinds constructed with
numerous small horizontal tubes through which the fire gases pass; and our
principal object is to obtain a thorough and efficient circulation of the water in
the boiler, the improvements also securing other important practical advantages.
Our improvements may be adopted in the construction of new boilers and they
may also be applied with great facility and at small expense to existing boilers.
In a common type of externally fired multitubular land boiler the main body of
the boiler consists of a horizontal cylinder made with the tubes passing through it
longitudinally the furnace or furnaces being beneath the front end of the boiler
and the fire gases passing under the boiler to the back end and returning through
the tubes. Or in some cases the fire gases which pass through the tubes may be
from a furnace or furnaces not placed directly under the boiler; or they may be
ignited combustible gases from a gas producer or other source. In boilers of the
kind referred to as ordinarily constructed there are some times too many of the
tubes, and in carrying out the Invention in such cases some of the uppermost tubes
and an equal number of the lowermost tubes are removed and the holes at the
front end are plugged, whilst in the holes at the back end curved or bent tubes are
fixed so as to be external to the boiler and so as to connect the upper holes with-
the lower ones. These bent tubes have the water inside of them, and being in the
current of the fire gases where the heat is very intense they present very sensitive
and efficient heating surface, and the action of the heat on them causes the water
to pass upwards through them in strong currents which entering and leaving the
boiler produce vigorous circulation throughout the water in the boiler. It is found
in practice that with the improved circulating tubes the production of steam is
increased a more uniform temperature is maintained throughout the water in the
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boiler, there is less wear and tear of the metal of the boiler such as ordinarily
occurs from strains due to unequal and irregular temperature, whilst there is also
a diminished production of smoke. In cases in which it is considered undesirable
to remove or diminish the number of the ordinary tubes the bent circulating tubes
may be fixed in additional holes specially made for them; or each bent circulating
tube may have one end fixed in a special hole whilst the other is fixed in a hole
which would otherwise be occupied by an ordinary tube.
In a common type of marine boiler with internal furnaces communicating with a
combustion chamber at the back, and fitted with horizontal tubes through which
the fire gases return from the combustion chamber to a smoke box at the front, the
bent circulating tubes may be fitted in the same manner as hereinbefore described
to the tube plate at the back or inner ends of the tubes. Some of the bent
circulating tubes may, however, with great advantage, have their lower ends made
to communicate with the lowest part of the boiler which extends beneath the
furnaces, at which part in ordinary boilers the water is often through want of
circulation much below the average temperature a condition of things giving rise
to severe and unequal strains on the metal of the boiler.
In the case of boilers of the locomotive type the bent circulating tubes may be
fixed in the smoke box in holes in the tube plate which holes would otherwise be
occupied by the ordinary tubes; or the lower ends of the bent circulating tubes
may be fixed below the barrel of the boiler. in a small casing or pocket fixed to the
bottom of the barrel.
And in order that our said Invention and the manner of performing the same
may be properly understood we hereunto append two sheets of explanatory drawings
to be hereinafter referred to and representing examples of the application of our
improvements.
On sheet. 1, of the accompanying drawings, figures, 1, and 2, are transverse and
longitudinal vertical sections of a land boiler as fitted with our bent circulating
tubes. Figures, 3, and 4, on sheet, 2, are transverse and longitudinal' vertical
sections of a marine boiler. Figure, 5, is a transverse vertical section showing one
arrangement of the bent circulating tubes in the smoke box of a locomotive boiler.
Figures, 6, and 7, are transverse and longitudinal vertical sections showing a modified
arrangement for a locomotive boiler; and figures, 8, and 9, are enlarged views
showing a device for fixing a bent circulating tube when a tube expander cannot
conveniently be used for fixing it. In these drawings the same reference numerals
are used to mark the same or like parts wherever they are repeated.
In the example shown in figures, 1, and 2, the main body of the boiler is a
horizontal cylinder, 11, having a steam casing, 12, above and connected to it. The
boiler is set in brick work and has a pair of furnaces, 13, beneath its front end,
whence the fire gases proceed by a flue, 14, to a combustion chamber, 15, at the
back end. The boiler is fitted with a number of horizontal tubes, 16, through which
the fire gases return from the combustion chamber, 15, to a smoke box, 17, at the
front end, and the gases proceed thence by side flues, 18, and a back flue, 19, to
the chimney. The bent circulating tubes, 20, are fixed in the tube plate, 21, at the
back end of the boiler; and in this example all the tubes, 20, are represented as
having their upper ends fixed in holes which might otherwise be occupied by
ordinary tubes (16) whilst as regards their lower ends some are fixed in holes
which might otherwise be occupied by ordinary tubes (16) and some are fixed in
additional holes, 22, below the lowest line of ordinary tubes. The bent circulating
tubes, 20, arranged as shown in figures, 1, and 2, are fixed by means of a tube
expander applied inside of the boiler.
In the marine boiler shown in figures, 3, and 4, the manner of applying the bent
circulating tubes, 20, is substantially the same as that described with reference to
figures, 1, and 2. Some, 23, however, of the bent circulating tubes have their
lower ends fixed to a part below the furnaces, 13, in order that the circulating
action due to the tubes may take effect on the water at the lowest part of the
boiler.

page_text: In the locomotive boiler shown in figure, 5, the bent circulating tubes, 20, bave
both their upper and lower ends fixed in holes in the tube plate, 21, which would
otherwise be occupied by ordinary tubes. In the locomotive boiler shown in
figures, 6, and 7, the upper ends of the bent circulating tubes, 20, are fixed like
those shown in figure, 5, but their lower ends are extended beneath the barrel of
the boiler into a casing or pocket, 24, which is fixed to the barrel. The ends of,
the tubes, 20, may be fixed in the casing, 24, by means of a tube expander
introduced through a hole formed for the purpose at the front of the casing and
afterwards closed by a screw plug. Or the connection of a bent circulating tube, 20,
or, 23, with the casing, 24, or with any part where there is no great heat to act on
it, may be made by means of the device shown in figures, 8, and 9. As shown in
these figures the bent circulating tube, 20, is connected by a screw coupling, 25, to
a nipple, 26, which is fixed by screwing into the casing, 24, or it might be a tube
plate or other part of the boiler.
Having thus particularly described the nature of our said Invention and in what
manner the same is to be performed we have to state that we do not restrict
ourselves to the precise details herein described or delineated; and we proceed to
ascertain what we believe to be the distinctive features of novelty of our said
Invention by declaring that what we claim is :-
In tubular steam boilers, the application of the bent circulating tubes with water
inside of them and communicating with upper and lower parts of the boiler, such
tubes having their upper ends fixed in the tube plate and their lower ends fixed in
a lower part of the tube plate or in some other lower part of the boiler, substantially
as and for the purposes hereinbefore described.
Deted this thirt first day of January 1884