IMPROVEMENTS IN STEAM BOILERS."
Year: 1871

page_text: LETTERS PATENT to Edward Mirchin, of No. 27, Leadenhall Street,
in the City of London, for the Invention of "IMPROVEMENTS IN STEAM
BOILERS."
PROVISIONAL SPECIFICATION left by the said Edward Mirchin at the
Office of the Commissioners of Patents, with his Petition, on the
25th July 1871.
I, EDWARD MIRCHIN, of No. 27, Leadenhall Street, in the City of
London, do hereby declare the nature of the said Invention for
"IM-
PROVEMENTS IN STEAM BOILERS," to be as follows:
i
This Invention consists in constructing steam boilers of inclined water
tubes, which with their connections form a series of complete circuits in
such a manner that an ascending current of water and steam takes place
throughout the whole range of tubes exposed to the fire till it reaches a
receiver in which the steam is collected, and from which a descending
current of dense water completing the circuit takes place in other tubes
outside the furnace, and entirely removed from the direct influence of

page_text: the fire, the descending tubes being in direct communication with a
mud collector, which is also removed from the furnace, and in which no
circulation takes place.
The advantages obtained by this arrangement are à perfect natural
and uninterrupted circulation of water in the ascending and descending
tubes, ensuring great efficiency in raising steam with absence of priming
and absence of accumulation of scale in the tubes, which being made of
such moderate diameters as to withstand great pressure afford perfect
safety from risk of explosion of the boilers.
In the construction of boiler which I prefer to employ the said water
tubes are arranged to form an ascending zig-zag line inside the furnace,
the lower and upper end of such zig-zag line of tubes being made to
communicate respectively with the lower and upper ends of a vertical
tube outside the furnace. At the top of this tube is a steam chamber,
and at the lower end thereof (below the connection with the boiler
tubes) is a receptacle for collecting the deposit. The water together
with the steam circulates in a direction from the lower end of the zig-
zag tubes to the upper end, whence it passes into the upper end of the
vertical pipe, and thence into the steam chamber, where the steam
separates and is collected, while the dense water flows down the vertical
tube and again enters the lower end of the zig-zag tubes.
Any solid
matter contained in the water descends in the vertical tube past the
opening into the zig-zag tubes, and is deposited in the before-mentioned
receptacle at the bottom. A partition is formed in the upper end of the
vertical tube to separate the ascending and descending currents of water
therein; or the communication of the upper end of the zig-zag tubes
with the steam chamber may be entirely separate from the vertical
tube.
In another arrangement I provide a vertical outside tube with steam
chamber at the upper end, and mud chamber at the lower end, and on
each side of the furnace the inclined boiler tubes inside the furnace
being made to communicate at each end with the two vertical tubes, in
which both ascending and a descending current takes place on opposite
sides of a partition fixed therein. Or the water may be made to ascend
in the one vertical tube from the inclined tubes, and then be made to
pass
from the steam chamber through an external inclined tube across
to the other vertical tube in which the water descends into the inclined
tubes again.

page_text: In arranging the inclined descending tubes in the furnace of my
improved construction of boiler I leave their bends and connections
outside the furnace walls to enable me to disconnect them for the
purpose of examining the tubes internally without disturbing the setting
of the boiler, and also to protect them from the deteriorating action of
the fire, two points in which boilers as hitherto constructed are very
deficient. I also provide cleaning plugs at the backs of the tube con-
nections to avoid disconnecting them for the purpose of periodical
cleaning. The tube connections may either have flange joints, or they
may be screwed together or jointed in any other manner known to
mechanics. I insert soot doors in available parts of the furnace walls to
enable one to clean and examine the tubes externally, and to introduce
suitable baffle plates to divide the furnace into a number of tortuous
passages for the better distribution of the hot gases.
To enable my improved boilers as also the description of steam boilers
which are quick steam generators to get rid of their surplus steam
promptly when the engine is suddenly stopped or other cause, I provide
a safety valve of the following construction:-A hollow casing is con-
nected with the boiler, the pressure in which the valve is intended to
relieve. This casing has an aperture in one side of the size of the
intended valve, and on the inner edge of this hole the scat of the valve
is formed inside the casing. A cylinder is also formed in the casing by
boring out another hole preferably of a larger diameter than the first..
The valve itself is connected to a piston fitting water-tight or steam-
tight in the last-mentioned hole or cylinder in such a manner that when
the valve is in its scat the piston is at rest at the inner end of the
cylinder, but when the steam pressure acting upon both piston and valve
causes the piston to move the valve is thereby drawn from its seat and
opened inwards, leaving the steam to escape without impediment. The
piston and valve are kept in their normal position by means of a spring
desired pressure
or weights to such extent as to counterbalance any
the steam on the piston, but as soon as this pressure is exceeded the
piston will be moved against the load imposed on it, and the valve will.
be opened.
of

page_text: level indicator for the same in the following manner :-I connect a tube.
to any part of the water space of the boiler, carry it down to a con-
venient height for the attendant, and terminate it with an upward bend,
I also carry another tube from the steam space of the boiler to within a
short distance of the upward bend of the first tube, and fit an ordinary
gauge glass tube between the ends of the two tubes; I then put a
sufficient quantity of mercury into the bend of the first tube, which com-
municates with the water space to counterbalance the head of the water
in the boiler, the mercury being visible in the glass tube and indicating
by its rise or fall against a graduated scale the variations in the water
level.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Edward Mirchin in the Great Seal Patent Office
on the 23rd January 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, EDWARD
MIRCHIN, of No. 27, Leadenhall Street, in the City of London, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-fifth day of July, in the year of
our Lord One thousand eight hundred and seventy-one, in the thirty-
fifth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Edward Mirchin, Her special licence, that I,
the said Edward Mirchin, my executors, administrators, and assigns, or
such others as I, the said Edward Mirchin, 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 BOILERS,"
upon the condition (amongst others) that I, the said Edward Mirchin,
my executors or administrators, by an instrument in writing under my,
or their, or one of their hands and seals, should particularly describe and
ascertain 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

page_text: 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 Edward Mirchin, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and by
the following statement thereof, reference being had to the accompanying
Drawings, and to the figures and letters marked thereon, that is to
say:
This Invention consists in constructing steam boilers of inclined water
tubes, which with their connections form a series of complete circuits in
such a manner that an ascending current of water and steam takes
place throughout the whole range of tubes exposed to the fire till it
reaches a receiver in which the steam is collected, and from which a
descending current of dense water completing the circuit takes place in
other tubes outside the furnace and entirely removed from the direct
influence of the fire, the descending tubes being in direct communi-
cation with a mud collector, which is also removed from the furnace,
and in which no circulation takes place.
The advantages obtained by this arrangement are a perfect natural
and uninterrupted circulation of water in the ascending and descending
tubes, ensuring great efficiency in raising steam with absence of priming
and absence of accumulation of scale in the tubes, which being made of
such moderate diameters as to withstand great pressure afford perfect
safety from risk of explosion of the boilers.
In the construction of boiler which I prefer to employ the said water
tubes are arranged to form an ascending zig-zag line inside the furnace,
the lower and upper end of such zig-zag line of tubes being made to
communicate respectively with the lower and upper ends of a vertical
tube outside the furnace. At the top of this tube is a steam chamber,
and at the lower end thereof (below the connection with the boiler
tubes) is a receptacle for collecting the deposit. The water together
with the steam circulates in a direction from the lower end of the zig-
zag tubes to the upper end, whence it passes into the upper end of the
vertical pipe, and thence into the steam chamber, where the steam
separates and is collected, while the dense water flows down the vertical
tube and again enters the lower end of the zig-zag tubes. Any solid
matter contained in the water descends in the vertical tube past the

page_text: opening into the zig-zag tubes, and is deposited in the before-mentioned
receptacle at the bottom. A partition is formed in the upper end of the
vertical tube. to separate the ascending and descending currents of water
therein, or the communication of the upper end of the zig-zag tubes
with the steam chamber may be entirely separate from the vertical
tube.
In another arrangement I provide a vertical outside tube with steam
chamber at the upper end and mud chamber at the lower end and on
each side of the furnace, the inclined boiler tubes inside the furnace
being made to communicate at each end with the two vertical tubes
in which both ascending and a descending current takes place on
opposite sides of a partition fixed therein. Or the water may be made
to ascend in the one vertical tube from the inclined tubes, and then be
made to pass from the steam chamber through an external inclined tube
across to the other vertical tube in which the water descends into the
inclined tube again.
In arranging the inclined descending tube in the furnace of my
improved construction of boiler, I leave their bends and connections
outside the furnace walls, to enable me to disconnect them for the
purpose of examining the tubes internally without disturbing the setting
of the boiler, and also to protect them from the deteriorating action of
the fire, two points in which boilers as hitherto constructed are very
deficient. I also provide cleaning plugs at the backs of the tube con-
nections to avoid disconnecting them for the purpose of periodical
cleaning. The tube connections may cither have flange joints, or they
may be screwed together or jointed in any other manner known to
mechanics. I insert soot doors in available parts of the furnace walls
to enable one to clean and examine the tubes externally and to introduce
suitable baffle plates to divide the furnace into a number of tortuous
passages for the better distribution of the hot gases.
To enable my improved boilers, as also the description of steam boilers
which are quick steam generators, to get rid of their surplus steam
promptly when the engine is suddenly stopped, or for other cause, I
provide a safety valve of the following construction -A hollow casing
is connected with the boiler, the pressure in which the valve is intended
to relieve. This casing has an aperture in one side of the size of the
intended valve, and on the inner edge of this hole the seat of the valve

page_text: is formed inside the casing. A cylinder is also formed in the casing by
boring out another hole, preferably of a larger diameter than the first.
The valve itself is connected to a piston fitting water-tight or steam-
tight in the last-mentioned hole or cylinder, in such a manner that
when the valve is in its seat the piston is at rest at the inner end of the
cylinder; but when the steam pressure acting upon both piston and
valve causes the piston to move, the valve is thereby drawn from its
scat and opened inwards, leaving the steam to escape without impedi-
ment. The piston and valve are kept in their normal position by means
of a spring or weights to such extent as to counterbalance any desired
pressure of the steam on the piston; but as soon as this pressure is
exceeded the piston will be moved against the load imposed on it, and
the valve will be opened.
The water level in my improved construction of boiler being situated
at an inconvenient height above the stoker's eye, I construct the water
level indicator for the same in the following manner :-I connect a tube
to any part of the water space of the boiler, carry it down to a con-
venient height for the attendant, and terminate it with an upward bend.
1 also carry another tube from the steam space of the boiler to within a
short distance of the upward bend of the first tube, and fit an ordinary
gauge glass tube between the ends of the two tubes. I then put a
sufficient quantity of mercury into the bend of the first tube which
communicates with the water space to counterbalance the head of the
water in the boiler, the mercury being visible in the glass tube, and
indicating by its rise or fall against a graduated scale the variation in
the water level.
DESCRIPTION OF. THE DRAWINGS.
1
Figures 1, 2, and 3, Sheet I., represent respectively a front elevation,
à longitudinal section, and a back clevation, of one form of boiler

page_text: secured to a descending pipe J. F. is a partition for separating the
ascending from the descending current respectively indicated by the
arrows. The lowest of the tubes A is joined to a T piece H, which has
its upper flange secured to the descending pipe J and its lower flange
secured to a branch on the mud collector G; R is a feed pipe, and S is a
blow-off pipe; K, K², K², K³, K*, are respectively the end and side walls
and roof of the furnace; L is a bank or bridge separating the furnace
chamber from the descending flue N; M is the furnace grate; M', the
furnace door and dead plate; and M2 is the ash-pit; N¹ is a horizontal
fluc leading to the chimney; 0, 0, are baffle plates or deflectors, which
may be fire-tiles laid upon the tubes A, A, in such a manner as to cause
the hot products of combustion to circulate among the tubes before
reaching the descending flue N; P, P, are soot doors giving access for
cleansing the exterior of the tubes, and admitting and placing the
deflectors O, O; Q, Q, are plugs screwed into holes in the bends C in
line with the tubes A, A, these holes giving access for cleansing the
insides of the tubes A, A. A superheater U may be placed in the roof of
the furnace chamber. This may be a tube closed at the ends connected
by a pipe T with the steam receiver E, and by a pipe V with the engine
or other apparatus to which the steam is supplied. The arrows in Fig. 2
indicate the circulation of the water throughout the successive parts of
the boiler. I prefer to make the upper tubes A larger than the lower
tubes, so as to allow greater space for the flow of the more highly heated
water mingled with steam bubbles. W represents a connecting pipe,
which may be applied to allow the passage of steam from some of the
bends C to the steam receiver without its having to circulate through
the upper pipes A. The highest and lowest of the tubes A may be
joined singly to the T pieces D and H, or they may be joined in pairs,
as represented in Figs. 1 and 3, and shewn on plan in Fig. 4.
And although in Figs. 1 and 3 only three pairs of circulating tubes
are shewn, it is to be understood that the construction therein repre-
sented may be repeated for any convenient number, the length of the
steam receiver E and mud collector G being extended so as to receive
the additional connections.
Figure 5, Sheet I., represents a transverse section of another form of
boiler constructed according to my Invention: In this case there is
a steam receiver E and mud collector G at each side of the furnace

page_text: chamber; the pipe J connecting them is provided with a diaphragm to
separate the ascending from the descending currents, and the inclined
circulating tubes. A are joined to both the connecting pipes J.
. Figure 6, Sheet I., represents a longitudinal sectional elevation of
another form of boiler constructed according to my Invention. In this
case the circulating pipes A all slope upwards from the descending
pipe X at the one end to the ascending pipe X' at the other end, and
the steam receiver E is connected with the descending pipe X by an
inclined pipe J. In this construction the tubes A may be joined to X
and X' singly, or they may be joined in pairs, as represented in plan in
Fig. 7. Instead of arranging the pipes X and X¹ at opposite ends of the
furnace chamber, as represented in Fig. 6, they may both be placed at
one end. Fig. 8 represents a plan of the circulating pipes A, and their
connection to the descending and ascending pipes Z and Z' when they
are so arranged, the two pipes A, A, being in this case connected by a
bend C, which may lie either horizontally or somewhat askew, so as to
maintain the gradual ascent of the current throughout.
Fig. 1, Sheet II., represents a vertical section, and Fig. 2 a sectional
plan of a safety valve constructed according to my Invention, to
be applied to boilers such as I have described above, and boilers of
similar character, by which steam is rapidly generated. A is a. branch
pipe connected to the steam space in the boiler having a valve seating
at a; B is a hollow piston or plunger, the upper part of which forms
the valve which seats on a. This plunger B may be packed so as to
slide without leakage in the lower limb of the pipe A, or it may be
formed with grooves, as indicated at b, to arrest leakage of steam past it.
C is a tube supported by arms D, D, on the flange of a casing tube M,
which is secured by screws N, to the branch pipe A. The tube C has a
pin E passed through it near its top, and to this pin is hooked one end
of a helical spring F, the other end is hooked to a screwed rod K.
The plunger B is fitted to a tube G, openings through the sides of which
are left at H for the passage of the arms D. A feather L is fixed in the
lower end of the tube G, and a slot or flat is formed in the screwed
rod K, the feather L acting in this slot or on this flat to prevent the
rod K from turning. J is a nut which may be conveniently formed as a
hand wheel, by turning which in the one direction or the other the
spring F can be drawn out or allowed to close; P is a nut which can be
set on any desired part of the rod K, and which, when the rod is drawn

page_text: down by the turning of the nut J, acts as a stop against G to prevent
the rod from being drawn farther, and thereby to prevent the spring F
from being farther extended. The screws N, N, are made with holes
through them. A bent wire passed through all these holes prevents
the screws from being turned, and the ends of the wire may be brought
to meet and be padlocked or sealed, thus preventing access to the interior
of the apparatus.
The action of the safety valve is as follows:-The spring F being
extended by turning the nut J to the desired degree of tension presses
the tubular plunger G, B, upwards, and keeps the valve closed at a.
When the pressure of steam acting on the annular area of 6 exceeds the
tension of the spring the plunger B descends and opens the valve at a;
when by the escape of steam the pressure is sufficiently reduced the
spring again closes the valve.
Fig. 3, Sheet II., represents a vertical section of a safety valve some-
what modified in form, but acting substantially as described above. In
this case the valve, which may be of spherical form B, is mounted at
one end of a lever O, the other end of which is connected to the hollow
plunger B¹, G. The flat on the screwed rod K may be graduated to
indicate the pressure corresponding to the tension of the spring F.
Figs. 4 and 5, Sheet II., represent respectively a front and a side
elevation of a mercurial water gauge constructed according to my
Invention, so as to shew at a convenient height for the eye (which may
be about 5 feet above the floor of the boiler room) the level of the water
in the steam receiver of a boiler such as I have described above, which
may be so high above the floor that an ordinary water gauge could not
be conveniently seen. In these Figures the casing of the gauge is shewn
in section. The gauge consists of two tubular limbs A and A¹ connected
together by a bend, and respectively connected by pipes to the water
and steam spaces in the steam receiver. These pipes are provided with
stop-cocks F and G, the levers of which may be connected so that they
can be opened or closed simultaneously. The limb A¹ has a glass tube B
fitted by stuffing boxes C, C, in the ordinary way, and by the side of the
glass tube is a scale M graduated as will hereafter be described. . A
glass E¹ is inserted in the casing D facing the glass tube B and scale M,
which may be seen through it. H and J are two stop-cocks, the plugs
of which are connected so that they can be opened or closed simul-
taneously. Each of these cocks has a syphon tube connected to it

page_text: extending within the limbs of the gauge to points a little above the
highest and the lowest levels of the mercury respectively. The office of
those cocks and syphon tubes is to blow out dirt that may collect over
the mercury. L is an iron, stone, or earthenware ball which floats on
the mercury, and which when the mercury descends in the limb A
follows it down till it seat itself on a coned seating in the position L",
and thereby shuts off the pressure from acting on the mercury, and so
prevents it from being blown out in case of accident causing leakage in
the limb A. The same ball L, when the mercury rises in the limb A,
rises with it and closes the end of the syphon tube so as to prevent
mercury passing out by it. The bend is charged with mercury to the
level a, a, in the one limb corresponding with the bottom of the glass
in the other limb. The cocks F and G being then opened the mercury
in the limb A will be pressed on by a column of water equivalent to the
height of the water level in the boiler above the mercury. By this
pressure the mercury will be depressed in the limb A to some line such
as b', 6', and raised in the glass B to a line b, b, the height of b above b¹
being that of a column of mercury sufficient to balance the column of
water, or about 11th of the height of the water column. The line b, b,
being taken as the mean water line the scale M is graduated upwards
and downwards, allowing about 12th of a foot in the graduation for every
foot of water column.
14
:
Having thus described the nature of my Invention, and in what
manner it is to be performed, I would have it understood that I do not
claim generally the construction of boilers wherein the water circulates
through tubes from a general receiver at the bottom to a general steam
receiver at the top, the said receivers being connected by a descending
tube or passage; but what I do claim is,―
First. The construction and use of circulating boilers wherein the
circulating pipes and passages permit the free and uninterrupted flow of
the water. The mud and sediment deposited from the water are collected
in a cavity and left undisturbed by the circulating fluid, and the con-
necting joints of the circulating pipes are removed from the action of
the fire, substantially as hercin described and illustrated by the Figures
on Sheet I. of the Drawings hereunto annexed.
Second. The use of a safety valve substantially as herein described in
connection with boilers such as are herein described, or boilers of similar
character by which steam is rapidly generated.

page_text: Third. The use of a mercurial gauge substantially as herein described
to indicate the water level in boilers where that level is at a height
inconvenient for indication by a gauge of ordinary construction.
In witness whereof, I, the said Edward Mirchin, have hereunto set
my hand. and seal, this Twenty-third day of January, in the year
of our Lord One thousand eight hundred and seventy-two.