IM- PROVEMENTS IN STEAM BOILERS
Year: 1879

page_text: LETTERS PATENT to Alfred Fernandez Yarrow, of the Firm of Yarrow and
Company, of the Isle of Dogs, Poplar, Shipbuilders, for the Invention of "IM-
PROVEMENTS IN STEAM BOILERS."
Sealed the 29th April 1879, and dated the 25th January 1879.
PROVISIONAL SPECIFICATION left by the said Alfred Fernandez Yarrow
at the Office of the Commissioners of Patents on the 25th January 1879.
ALFRED FERNANDEZ YARROW, of the Firm of Yarrow and Company, of the Isle
of Dogs, Poplar, Shipbuilders. "IMPROVEMENTS IN STEAM BOILERS."
My Invention ralates to water tube boilers with a forced circulation, that is to
say, a circulation maintained mainly by means of a pump or its equivalent, and it
consists in constructing such boilers of series of tubes independent the one of the
other, but having a common inlet for the water and a common outlet for the steam,
each tube or series of tubes being provided with a plug, valve, or its equivalent, so
arranged as to admit in the event of the failure of any portion of the boiler
occurring of the same being cut off from without interfering with the working of the
boiler. The tubes are contained in a fire box or chamber in a part of which is the
grate for the fire, the products of combustion from which will thus be distributed
over and brought into intimate contact with the exterior of the tubes during the
passage of such products to the chimney, and thus rapidly generate steam in the
interior of the tubes through which the water is continuously forced. The cir-
culating tubes may be made either straight or arranged so as to follow a serpentine,
zig zag, or circuitous course, and the common inlet and common outlet may be
either vertical, horizontal, or otherwise.
In addition to the feed pump or its equivalent usually employed for feeding I
prefer to adopt a separate and independent pumping apparatus for maintaining a
more active circulation, this latter apparatus taking its suction from the outlet
chamber and delivering into the inlet chamber.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
-the said Alfred-Fernandez-Yarrow-in-the Great Seal. Patent Office on the
-24th July 1879.
ALFRED FERNANDEZ YARROW, of the Firm of Yarrow and Company, of the Isle
of Dogs, Poplar, Shipbuilders. "IMPROVEMENTS IN STEAM BOILERS."
My said Invention relates to water tube boilers with a forced circulation, that is
to say, a circulation maintained mainly by means of a pump or its equivalent, and
it consists of improvements in boilers of this description whereby their efficiency is
increased, and they are rendered free from defects which attend the use of such
boilers as ordinarily constructed.
Heretofore boilers of this description have usually been constructed either with
a tube coiled spirally or with a series ef vertical tubes of a serpentine form placed
side by side.
Now according to my Invention I employ a series of tubes of a serpentine form,
but in lieu of placing the said serpentine tubes side by side I arrange them in
horizontal tiers, the one above the other, and by preference quincuncially, or so that
the different bends of each alternate tier shall be opposite the space between the
bends of the said tier above and below.
By this improved arrangement a much greater useful effect is obtained in a given
sized boiler with a given consumption of fuel, as by the use of horizontal tiers the
fire beneath and heated products of combustion have access uniformly to the whole
of the sections of length of which each tube is composed, whereas, according to the
arrangements heretofore proposed, the different portions of each serpentine tube
are acted upon to a varying extent by the fire and heated products of combustion,
the lower portions being highly heated and the upper portions subjected to a
relatively low temperature, so that the circulation in the whole of the tubes of the
series is impeded, whilst on the other hand, in my improved arrangement, although
the different tiers are acted upon to a varying extent according to their distance
from the fire, yet the different bends of any particular tier are subjected to the
same temperature, and as they are all situate in one horizontal plane, the circulation
is-maintained uninterruptedly throughout each and all of the tiers of the series.
The several tiers are connected at one extremity of the serpentine to a common
vertical inlet column for the water, and at their other extremity to a common
vertical outlet column for the steam and any heated water which may remain
unvaporized, the steam being thence conducted as and where required for duty, and
the heated water pumped back to the inlet column to be again forced through the
serpentine tubes and a portion of it there vaporized, and the surplus again returned
to the inlet for recirculation, and so on in succession during the operation of the
boiler.
And in order that my said Invention may be fully understood I shall now
proceed more particularly to describe the same, and for that purpose shall refer to
the several Figures on the annexed Sheets of Drawings, the same letters of reference
indicating corresponding parts in all the Figures.
Figure 1 (Sheet 1) of the accompanying Drawings represents a front elevation
of a steam boiler constructed according to my said Invention; Figure 2 is a longi-
tudinal section; and Figure 3 (on Sheet 2) is a horizontal section of the same;
Figure is a sectional detail of a portion of one of the tubes.
The improved boiler consists of an inlet column A. for water, an outlet column B
for steam and unvaporized water, and a series of horizontal tiers of serpentine
tubes C (shewn clearly in Figure 3), arranged by preference quincuncially as
indicated. The tubes C are connected at one extremity a of the serpentine to the inlet
column A and at the other extremity of the serpentine to the outlet column B,
and they are surrounded except at those portions which enter the inlet and outlet
columns with a casing D having at its lower part a grate E, the fire and combustible

page_text: gases from which envelope the whole series of tubes, the waste products thence
escaping by a chimney F at the top. Water is supplied to the inlet column A
through a pipe c by means of any suitable pump or its equivalent, and thence
passes under pressure into and through the whole of the tiers simultaneously.
During its passage through the tubes a large portion of the water becomes
vaporized under the action of the surrounding heat, and enters the outlet column
B in the form of steam, and remains at the upper part of such column, which con-
stitutes a steam dome, whence the steam is drawn off through a pipe D for duty as
and where required. The remaining portion of the water forced through the tubes,
which, although its temperature has been elevated, remains unvaporized, also enters
the outlet column B, but descends into the lower part thereof, whence it is drawn
off by another pump or its equivalent, and returned to the inlet column A through
the pipes e, el, for recirculation through the tubes C. The inlet column A is pro-
vided with non-return valves in connection with the pipes e, e¹, as will be well
understood; it is also fitted with plugs G (one opposite the inlet of each of the
tubes C) in order to gain access to the tube ends.
It has been found in practice that if the whole of the tubes of the series are
supplied with an equal quantity of water, the tiers which are in proximity to the
fire do not receive sufficient, whilst those which are far removed from the fire receive
a superabundance. I therefore prefer to provide the inlet end a of each tube with a
plug f, as shewn in the detail, Figure 4, having a hole g of a size proportionate to
the evaporative power of the respective tier. For example, in the case of the lower
tiers the hole is larger than in the plugs for the upper tiers, which are far removed.
from the fire, the holes for the several tiers gradually decreasing in size from the
maximum at the lowest tier or tiers, to the minimum at the uppermost tier or tiers;
or I may otherwise arrange the inlets so as to regulate the supply of water
according to the evaporative power of the respective tiers.
Having now described and particularly ascertained the nature of my said
Invention, and the manner in which the same is or may be used or carried into
effect, I would observe in conclusion that what I consider to be novel and original
and therefore claim as the Invention secured to me by the hereinbefore in part
recited Letters Patent is,-
In water tube boilers with a forced circulation the employment of serpentine
tubes arranged in horizontal tiers, substantially in the manner and for the purpose
hereinbefore described.
In witness whereof, I, the said Alfred Fernandez Yarrow, have to this my
Specification set my hand and seal, this Twenty second day of July, One
thousand eight hundred and seventy nine.
A. F. YARROW. (L.S.)