IMPROVEMENTS IN STEAM ENGINE BOILERS, AS APPLIED TO THE PROPULSION OF VESSELS
Year: 1855

page_text: LETTERS PATENT to George Rennie, of the firm of George Rennie, John
Keith Rennic, and George Banks Rennie, of Holland Street, Blackfriars,
Engineers, for the Invention of "IMPROVEMENTS IN STEAM ENGINE BOILERS,
AS APPLIED TO THE PROPULSION OF VESSELS."
Sealed the 1st April 1856, and dated the 2nd October 1855.
PROVISIONAL SPECIFICATION left by the said George Rennie at the
Office of the Commissioners of Patents, with his Petition, on the 2nd
October 1855.
I, GEORGE RENNIE, of the firm of George Rennie, John Keith Rennie, and
George Banks Rennie, of Holland Street, Blackfriars, Engineers, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN STEAM ENGINE
BOILERS, AS APPLIED TO THE PROPULSION OF VESSELS," to be as follows:-
That inasmuch as when marine boilers are required to be of the least
possible height, so as to be kept below a certain level in the vessel, as, for
example, below the load water line, they are frequently or commonly liable
"to prime," or discharge the water contained within them along with the
steam into the steam engine cylinders, and thereby cause damage to and
impede the perfect working of the engines; and as it is a desideratum in all
steam engine boilers, but in marine boilers more particularly, that steam be
delivered to an engine in as "dry" or free a state as possible, that is, not
surcharged with water; with these views 1 have designed an arrangement by
which I am enabled to construct boilers so low as to enable them to be fixed

page_text: in all ordinary cases below the water line of a vessel, at the same time
obviate the surcharging of the steam with water, and so ensure the steam
being delivered to the engine in a suitable state.
This I effect in the following manner :-I add to the boiler a chamber,
which may either be an extension thereof, or a distinct vessel, which may be
either on the outside or within the boiler, of suitable strength and size, having
an opening or passage to the boiler as high up in the steam space as con-
venient. and such opening or passage must not be of a less area than the bore
of the pipe for the supply of steam to the engine or engines. This steam
chamber need not be subjected to the direct action of the fire or heat there-
from, but must be maintained at a sufficient temperature, so as not to impair
the elastic force of the steam, or allow of its condensing within the vessel or
chamber.
I insert the steam pipe in the most convenient position in or near to the top
of this steam chamber. In the bottom of this chamber I insert a pipe with a
blow-off cock, so as at any time to free it from the presence of water which
might be carried over along with the steam.
For the better effecting my object, in certain cases I apply screen plates or
perforated divisions within the chamber a, and between the opening 6 and
steam pipe d, to check the steam, and cause the water, if any be contained
therein, to fall to the bottom of the chamber. I do not confine myself to the
precise position of these screen plates. I also introduce a plate or wash-board
across the end plate of the boiler on a level with the bottom of the opening b,
for the purpose of further checking the ebullition and washing of the water
at that point.
I hereunto annex a side view of our Invention as applied to a low boiler
for a vessel of shallow draught, in which the furnaces are placed athwart-ship
instead of fore and aft. A is the boiler; a is the chamber; b is the opening
or passage between the boiler A and the chamber a; c is the blow-off cock
and pipe; d is the steam pipe; c is the surface of water in the boiler; f is a
wash-board, which may be varied in form, or omitted; g is a screen plate, or
a perforated division, one or more of which may be applied, and either vertically
or otherwise.
In the Drawing I have shewn the chamber a as applied to the boiler A,
because the peculiarities of the construction and position of that boiler permits
of its being so applied most advantageously. But I can apply my Invention
to boilers in various ways, according to their general form, arrangement of
parts, and mode of fixing in the vessel.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said George Rennie in the Great Seal Patent Office on the
1st April 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
RENNIE, of the firm of George Rennie, John Keith Rennie, and George
Banks Rennie, of Holland Street, Blackfriars, Engineers, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Second day of October, in the year of our Lord One
thousand eight hundred and fifty-five, in the
year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
George Rennie, Her special licence that I, the said George Rennie, my
executors, administrators, and assigns, or such others as I, the said George
Rennie, my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter during the
term therein expressed, should and lawfully might, make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN STEAM ENGINE
BOILERS, AS APPLIED TO THE PROPULSION OF VESSELS," upon the condition (amongst
others) that I, the said George Rennie, by an instrument in writing under my,
or their, or one of their hand and seal, should particularly describe and ascer-
tain the nature of the said Invention, and in what manner the same was to
be performed, and cause the same to be filed in the Great Seal Patent Office
within six calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said George Rennie, do hereby declare the
nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement and accompanying Drawing:-
Inasmuch as when marine boilers are required to be of the least possible
height, so as to be kept below a certain level in the vessel, as, for example.
below the load water line, they are frequently or commonly liable to prime,
or discharge the water contained within them along with the steam into the
steam engine cylinders, and thereby cause damage to and impede the perfect
working of the engines; and as it is a desideratum in all steam engine
boilers, but in marine boilers more particularly, that steam be delivered to an
engine in as dry or free a state as possible, that is, not surcharged with water;
with these views the following arrangement has been designed, by which
boilers can be constructed so low as to enable them to be fixed in all ordinary

page_text: cases below the water line of a vessel, at the same time obviate the surcharging
of the steam with water or primeing over," and so ensure the steam being
delivered to the engine in a suitable state.
This is effected in the following manner:-To the boiler is added a chamber,
which
I may either be an extension thereof, or may be a distinct vessel, of suit-
able strength and size, having an opening or passage to the boiler as high up
in the steam space as convenient, but such opening or passage must not be of
a less area than the bore of the pipe for the supply of steam to the engine or
engines. This steam chamber need not be subject to the direct action of the
fire, but it must be maintained at a sufficient high temperature, so as to impair
the elastic force of the steam, or allow of its condensing within the vessel or
chamber. The steam pipe must be inserted in the most convenient position
in or near to the top of the steam chamber. In the bottom of this chamber
there should be inserted a pipe with a blow-off cock, so as at any time to free
it from the presence of water, which might be carried over along with the
steam; and in the accompanying Drawing guage cocks are shown, by which
the height of condensed water can be readily ascertained.
In the accompanying Drawing, Fig. 1 is a longitudinal section of this
Invention as applied to a low boiler for a vessel of shallow draft, in which the
furnaces are placed athwart-ship, instead of fore and aft.
In Fig. 1, A, A, is the shell of the boiler; B, B, the furnaces; C, C, the
tubes; D is the chamber.
Instead of permitting the steam to be drawn direct from off the surface of
the water into the steam pipe in such a boiler, a screen plate E is interposed
between the opening from the boiler, or more than one of such plates may
be inserted, as shown in Fig. 2, for more effectually drying the steam as
it passes from the boiler A through the steam chamber D, and through
the opening C into the steam pipe F, as the steam in passing over would
impinge against the screen plate, and cause it to part with the water, which
will fall and collect at the bottom of the chamber D, which is provided
with a blow-off pipe and cock H. I, I, are two guage cocks for ascertaining
the quantity of water within the chamber. A wash-board or dash plate may
be fixed within the boiler, across and before the opening made between the
boiler and the steam chamber, for the passage of the steam, for the purpose of
checking the ebullition of the water.
In the Drawing hereunto annexed, the chamber D is shown as a continua-
tion of the boiler A, because the peculiarities of the construction and position
of that boiler permits of its being so applied most advantageously; but I do
not confine myself to the precise arrangement shown in the accompanying

page_text: Drawing, as similar drying chambers may be added to marine boilers either at
the side or end. But I claim the addition of a chamber in which the steani
is freed from the water which would otherwise be carried over with it; and
by the use of which chamber lower boilers may be used on board of vessels
of small draft, and whether such chamber be of the form described herein,
or when such chamber is formed at, or within, or attached to, the side or
end of a marine boiler.
In witness whereof, J, the said George Rennie, have hereunto set my
hand and seal, this Thirty-first day of March, in the year of our Lord
One thousand eight hundred and fifty-six.
Witness,
WILLIAM SMITH, C.E.,
10, Salisbury St., Adelphi.
GEORGE RENNIE. (L.S.)