IMPROVEMENTS IN STEAM GENERATORS
Year: 1882

page_text: LETTERS PATENT to John Isaac Thornycroft of the firm of John I. Thornycroft
and Co., of Church Wharf, Chiswick, in the County of Middlesex, for an
invention of "IMPROVEMENTS IN STEAM GENERATORS."
PROVISIONAL SPECIFICATION left by the said John Isaac Thornycroft at
the Office of the Commissioners of Patents on the 4th May 1882.
JOHN ISAAC THORNYCROFT, of the firm of John I. Thornycroft and Co. of
Church Wharf, Chiswick, in the County of Middlesex. "IMPROVEMENTS IN STEAM
GENERATORS."
My invention relates to improvements in tubulous steam generators of the kind
wherein the water from which steam is generated is contained in the tubes. These
are arranged in coils forming approximately concentric hemispheres so arranged
about the fire that the heating surface of each hemisphere may be throughout as
nearly as possible equidistant from the centre of heat. In conjunction with these
coils I in some cases provide a conical dish for the fire with a view to dispense
with the use of fire brick. Each hemisphere of coil is formed not entirely of one
continuous tube but of several lengths each constituting a separate coil the upper
end of which is connected with the upper part of a vessel constituting a combined
water reservoir and steam chamber or drum; the lower end of each length of coil
is connected to an annular water chainber which is itself connected to the lower
end of the before mentioned vessel. To effect efficiently separation of the steam
from the water the above mentioned vessel (which may conveniently be of a
cylindrical form) is arranged as follows:-It is placed vertically, its bottom is in
connection with the annular water chamber; the top of the vessel is closed by
means of a cover which in some cases can conveniently be adapted to form a safety
valve, for the boiler. The upper ends of the several steam coils are each in con-
nection with the upper end or steam chamber portion of the vertical vessel just
below the cover; all the steam generated, and the water it carries with it pass into
an annular space formed in the steam chamber by means of an annular curtain or
partition of smaller diameter than the interior of the steam chamber, and closed at

page_text: the top just above the steam and water inlets but open below so that when the
mixed steam and water rush into the annular space from the coils they strike
against the said curtain or partition and are driven downwards, the water falling
into the lower part of the vertical vessel and the steam rising within the curtain
or partition, between its inner surface and the exterior of a stand pipe that rises
froin the bottom end or closure of the vertical vessel (which it penetrates) nearly
to the top of the same, this stand pipe being open at the top receives and conducts
the steam away as required for use. To arrest any water that may be held in
suspension by the steam as it enters between the curtain, or partition and stand pipe,
spiral deflecting plates are provided. The stand pipe may be used as a stay between
the cover and bottom end or closure of the vessel that constitutes the combined
steam chamber and water reservoir where great strength and lightness are required.
A water guage is provided to indicate the height at which the water stands in the
said vessel.
The fire grate is placed immediately under the coiled tubes at or about the
diameter of the several hemispheres and a suitable casing envelopes the coils the
upper part forming the uptake or chimney.
The action is as follows:-
The vertical vessel is, say, half filled with water and the coils and tube leading
to them below the water surface in the separator or vessel being completely filled
with water, the fire is lighted under the coils and when sufficient steam is formed
in any of the coils to reduce the weight of the column to the point of discharge
into the chamber to less than the corresponding column in the supply pipe and
vessel circulation commences and the tendency to circulate increases as a greater
proportion of steam to water is contained in the tubes, thus a tube exposed to
more heat than the rest has the advantage of more circulation while a tube if not
exposed to the fire will have no circulation and does not require any.
The steam and water entering the vessel is deflected by the curtain and its spiral
plates into a spiral motion downwards which throws the water contained by reason
of its greater density against the convex side of the curved path or against the
surface of the vessel allowing the steam in a pure state to rise about the centre of
the vessel.
The power of circulation is increased by the height of the water line above the
heated part of the coil where steam is formed, and the separator placed in the
uptake adds to the effective heating surface, the supply pipe leading to the bottom
of the coils should not be heated so much as to generate steam therein or the
circulation will be impeded.
An outer coil or coils is or are used to heat the feed water before entering the
central vessel and the water passing over with the steam falling into the lower
part of the vertical vessel is returned to the coils together with the feed water.
As soon as steam is formed steam and water rise and flow through the pipe
already mentioned into the annular space to the upper part of the vertical vessel,
water that has accompanied such steam falls to the lower part of the vessel; the
steam rises within the annular curtain or partition between it and the stand pipe
coming in contact with the deflecting plates and thence entering, at the upper end,
the stand pipe and descending it for use.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Isaac Thornycroft in the Great Seal Patent Office on the
4th November 1882.
JOHN ISAAC THORNYCROFT, of the firm of John I. Thornycroft and Co, of
Church Wharf, Chiswick, in the County of Middlesex. "IMPROVEMENTS IN STEAM
GENERATORS."
My invention relates to improvements in tubulous steam generators of the kind
wherein the water from which steam is generated is contained in the tubes.
These are arranged in coils forming approximately concentric hemispheres so
arranged about the fire that the heating surface of each hemisphere may be
throughout as nearly as possible equidistant from the centre of heat.
In conjunction with these coils I in some cases provide a conical dish for the fire
with a view to dispense with the use of fire brick.
Each hemisphere of coil is formed not entirely by one continuous
number or series of lengths each constituting a separate coil the upper.
is connected with the upper part of a vessel constituting a combined way
and steam chamber or drum, and hereafter called the separator; the lo
each length of coil is connected to a water chamber which is itself connec
lower end of the separator.
e but of a
of which
reservoir
The water chamber will usually be in the form of an annulus with a
removed to form the entrance to the furnace and therefore is hereinafter cal
annular water chamber.
end of
the
To effect efficiently separation of the steam from the water the above ment.
separator (which may conveniently be of a cylindrical form) is arranged as foll
-It is placed vertically, its bottom is in connection with the annular wa
chamber; the top of the vessel is closed by means of a cover which in some cas
can conveniently be adapted to form a safety valve for the boiler.
1
9
The upper ends of the several steam coils are each in connection with the upper
end or steam chamber portion of the vertical separator just below the cover, all the
steam generated and the water it carries with it pass into an annular space formed
in the steam chamber of the separator by means of an annular curtain or partition
of smaller diameter than the interior of the steam chamber and closed at the top
just above the steam and water inlet but open below so that when the mixed steam
and water rush into the annular space from the coils they strike against the said
curtain or partition and are driven downwards the water falling into the lower
part of the separator and the steam rising within the curtain or partition, between
its inner surface and the exterior of a stand pipe that rises from the bottom end
or closure of the separator (which it penetrates) nearly to the top of the same, this
stand pipe being open or perforated at the top receives and conducts the steam
away as required for use.
To arrest any water that may be held in suspension by the steam before
it enters between the curtain or partition and stand pipe spiral deflecting plates
are provided.
The stand pipe may be used as a stay between the cover and bottom end or
closure of the vessel that constitutes the combined steam chamber and water
reservoir or separator where great strength and lightness are required.
A water gauge is provided to indicate the height at which the water stands in
the said vessel.
The fire grate is usually placed immediately under the coiled tubes at or about
the diameter of the several hemispheres and a suitable casing envelopes the coils
the upper part forming the uptake or chimney.

page_text: Referring to the accompanying drawings Figure 1 is an elevation of a steam
generator according to my invention.
Figure 2 is a section taken at right angles to Figure 1.
In this view the external casing is supposed to be partly removed to disclose
the internal arrangements, and the approximately hemispherical coils are shewn
in section
Figure 3 is a plan, Figure
is a plan shewing the form of the annular water
chamber and the positions of the glands therein for attachment thereto of the
respective steam generating coils.
Figure 5 is a vertical central section (to a larger scale than Figures 1 to 4) of
the separator with its fittings and connexions.
Figure 6 is an elevation and Figure 7 a plan of the annular curtain or partition
that promotes separation of water from the steam.
Figure 8 is a side elevation of the upper part of the separator detached shewing
the positions of junction therewith of the coils.
a a are coils of tubes, each coil being arranged so that it forms approximately
a portion of a hollow sphere, and all the coils being concentric or nearly so.
Each spherical coil is formed of a series of lengths of tube, each constituting a
separate coil, the upper end of which is connected with the upper part of a vessel b
(Figures 2 and 5) which constitutes the separator. In the generator illustrated the
coils enter the separator b in three rows (Figure 2).
The lower end of each length of coil is connected to the annular water chamber c,
which is on the level of the firebars or thereabouts (Figure 1).
The connexions are not spaced evenly all round the chamber, as it is necessary
to leave a space or gap at one place for the fire door e and at that point a portion
of the annulus the chamber would otherwise form is removed as shewn
Each set of coils is supported and retained by bars d d which clasp them in such
a way as not to impede the expansion and contraction
The fire grate f is placed immediately under the coiled tubes at or about the
diameter of the hemisphere of coils, and is provided with an ash pit g to which
access is gained by the door g¹.
The separator b is a cylindrical vessel situated in the uptake but defended from
the direct impingement of the flame by a guard or covering b' of asbestos or other
refractory substance (Figure 2).
It is formed with a thickened portion at the upper part, where it is pierced for
the entry of the upper ends of the coils.
Its lower part is provided with a connexion at h for the attachment of the
circulating pipe which leads to the lower annular water chamber.
The upper part of the vessel b is closed by a lid i having a gun metal ring or
face . let into it, which fits a corresponding gun metal ring or face in the top of
the vessel b.
When the lid is removed the interior of the vessel is immediately open to
inspection.
The lid and the closure of the lower part are connected by a hollow stay j that
can be tightened by the nut k and lock-nut k¹.
This stay also acts as a stand pipe for the emission of steam but it is evident
that a separate steam pipe might be used, or the stay might be dispensed with if
other means were adopted for securing the ends of the vessel.
The steam generated in the coils a is emitted therefrom mixed with water and
enters the vessel b through the holes being discharged behind the annular curtain
or partition m (Figs. 5, 6 and 7).
As there is no passage through this partition the mixed fluids are obliged to
pass downwards, and in so doing acquire a whirling motion from the spiral
deflecting plates m¹ m³ (Figs. 6 and 7) which aids in the disengagement of the
steam from the mixture.
The water falls to the bottom of the vessel, while the steam rises to the upper

page_text: portion and passing through the holes j' of the steam pipe j is conducted
downwards and out through the elbow to the external branch j³.
The feed pipe is provided with three branches n¹ n² n³.
n' is connected to the outer hemispherical coil of tubes which is farthest removed
from the fire and acts as a water heater.
The upper end of this coil is connected to one of the holes in the separator.
The branch n goes directly to the annular water chamber c while the branch n³
goes directly to the pipe p which connects it with the separator.
n is a cock which normally is kept open.
n is a valve that opens upwards. By this arrangement 'normally the feed must
go either by n' or n³."
When it goes by n¹ it passes through the outer or feed water heating coil.
Should the supply to that coil from n' fail from any cause the valve n³ will
rise and admit water to the said coil from the annular water chamber.
It is convenient in many cases to utilize this same pipe p as a passage or way
for the scum and mud pipe o (Figure 5).
The lower end of this pipe o dips nearly to the bottom of the mud pocket or
collector o¹, and its outlet is led concentrically through the feed inlet pipe p.
The pipe p ends outside the annular curtain m while the pipe o passes through
this curtain to the central part of the vessel b.
When the valve o is opened the steam pressure forces the contents of the mud
collector o up the pipe o and away down the blow off pipe.
q (Figure 2) is a water gauge to shew the height of the water in the separator.
is a safety valve fixed on the steam pipe.
vis an external cover or casing surrounding the coils and vessel b; its
portion forms the uptake.
The action is as follows;-
upper
The separator b is, say, half filled with water and the coils a a and the annular
chamber c and tube h2 leading to them from below the water surface in the
separator being completely filled with water, the fire is lighted under the coils
and when sufficient steam is formed in any of the coils to reduce the weight of the
column to the point of discharge into the chamber to less than the corresponding
column in the supply pipe h² and separator b circulation commences and the
tendency to circulate augments as the proportion of steam to water in the tubes
increases, thus a tube exposed to more heat than the rest has the advantage of
more circulation, while a tube if not exposed to the fire will have little or no
circulation and does not require any.
The steam and water entering the separator are deflected by the curtain m and
its plates m' m' into a whirling or gyrating motion downwards which throws the
water by reason of its greater density towards the convex side of the curved path
or against the concave surface of the separator allowing the steam to rise about
the centre of the separator, The circulating power is increased by the height of
the water line above the heated part of the coil where steam is formed, and the
separator, placed in the uptake, adds to the effective heating surface, the supply
pipe leading to the bottom of the coils should not be heated so much as to generate
steam therein or the circulation will be impeded.
When feed water is being supplied to the generator through this feed water
heating coil its temperature is raised in that coil and the water thus heated passes
on to the separator wherein any steam that may have been generated in the feed
water heating coil is separated and the water descends to the lower part of the
separator whence it proceeds to the steam generating coils a,-together with water
that has been separated from steam generated in coils a.
It will be observed that in the drawings to prevent confusion many of the fire
bars have been omitted.
Figure 9 is an elevation partly in section and Figure 10 is a half plan illustrating
a modification of the above described generator.
In this arrangement the outer coils are arranged in a lining to more completely

page_text: protect the outer casing of the generator and the products of combustion are
caused to pass through spaces provided between the coiled pipes at a near the
lower part of the fire box, and thence to ascend in contact with the tubes of the
inner, outer and intermediate coils. A is a baffle plate.
The arrangement in other respects will be readily understood from the drawing.
Having thus described the nature of the said invention and the manner in
which it is to be performed I would have it understood that what I consider to be
novel and original and therefore claim as secured to me under the Letters Patent
herein before in part recited is ;-
1. In a tubulous steam generator the use of coils of hemispherical form (or
approximately so) each comprising a series of pipes, each of which is connected at
its upper extremity to the upper part of a vessel constituting a combined water
reservoir and steam chamber or drum, and at its lower extremity to an annular
water chamber that is itself connected to the lower end of the before mentioned
vessel substantially as described.
2. In a tubulous steam generator such as referred to in the preceding claim the
use of a combined water reservoir and steam chamber or drum wherein the water
is separated from the steam by means of an annular curtain or partition and spiral
deflecting plates, and in which the steam and water are discharged downwards
substantially as described.
3. The improved tubulous steam generator constructed arranged and operating
substantially as shewn in and described with reference to Figures 1 to 8 of the
drawings.
In Witness whereof I the said John Isaac Thornycroft have hereunto set my
hand and seal this third day of November in the year of our Lord, one
thousand eight hundred and eighty two.
JOHN I. THORNYCROFT.
(L.S.)