Improvements in Bosh Plates for Blast Furnaces.
Year: 1890

page_text: Date of Application, 22nd Jan., 1890-Accepted, 22nd Feb., 1890
COMPLETE SPECIFICATION.
[Communicated from abroad by JULIAN KENNEDY, of Latrole, in the County of
Westmoreland, and State of Pennsylvania, United States of America, Metallurgical
Engineer.]
Improvements in Bosh Plates for Blast Furnaces.
I, JOHN THOMSON KING of 4 Clayton Square, Liverpool, in the county of Lancaster,
Patent Agent do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in and by
the following statement :-
In the operation of blast furnaces, one of the difficulties which engineers have been
obliged to meet is the corrosive action of the intense heat and smelting reactions upon
the masonry of the stack. The inside of the walls unless protected soon burn out and
present large cavities around the boshes where the heat is very intense. The formation
of these cavities destroys the symmetry of the stack and produces an uneven or faulty
distribution of the currents of reducing gases and also causes an irregular descent of
the solid materials, which necessitates the use of a greater amount of fuel and more
time to smelt the iron.
To prevent this and to preserve the integrity of the furnace walls it has been usual
to build circles of water cooled plates in the masonry of the bosh these are technically
known as
"bosh plates" and bave consisted of simple cast iron plates which are cast
about a coil of wrought iron pipe circular in cross section. A series of these plates
which are of the form of a segment of a circle are built into the stack around the bosh
in the same horizontal plane with their sides abutting against each other so as to
encircle the stack and a stream of water is caused to circulate through the coil in each
segment. A number of these horizontal series of water plates is built in the furnace
walls separated vertically from each other usually about three feet. The inner edges
of these plates are distant from the inside of the furnace about six inches when the
latter is in its normal condition and the outer edges project to the outside of the stack
where it has been customary to unite the adjacent plates to each other by bolts and
flanges for the purpose of bracing the furnace walls. The circulation of water through
these plates has the effect of retarding the corrosion of the walls very greatly but they
are subject to the following disadvantages:-When in time the working of the furnace
burns away the inner lining of the walls and exposes the edges of the plates the cast
iron sheli of the latter will eventually burn and will lay bare the inner part of the coil.
Immediately upon the destruction of the latter the water will escape into the furnace
and the usefulness of the plates as a cooling device will be spoiled.
This necessitates the removal of the old plate and the substitution of a new one but
this change is apt to distort the furnace wall the symmetry of which cannot easily be
restored. In the iron pipes which have customarily been cast inside of the bosh
plates there is an especial reason for their destruction because the flowing water unless
exceptionally pure soon corrodes their inner surfaces and this causes a sediment or
deposit from the water to settle in and adhere to the pipes and to choke or partially
choke them thereby lessening the cooling influence of the water, and causing the
exposed plate to burn away rapidly. Another bad feature of the bosh-plate which
have been commonly used, results from the mode of their manufacture. In casting
the metal around the wrought iron or copper coil there is apt to be an imperfect union
between the two, caused either by the formation of blow-holes in the surrounding
metal, or from other causes. In consequence the coil has a defective cooling
influence on the plate, and upon the stack, and when the plate itself is exposed, it
soon burns.
My invention has for its object to so improve the construction of these bosh
plates and their auxilliary appliances as to obviate the evils above adverted to, and to

page_text: strengthen the structure of the stack. In order that others skilled in the art may fully
understand and apply the invention, I will describe it with reference to the accompany-
ing drawings in which
Figure 1 is a plan view of one of my improved bosh plates a part of the upper shell
thereof being broken away for purpose of illustration.
Figure 2. is a vertical cross section of the plate on the line - of figure 1.
Figure 3 is an end view of the pipe and of the plate.
Figure 4 is a horizontal cross section through the boshes of a blast furnace,
showing the arrangement of the bosh plates in the furnace walls, on the line - of
figure 5.
Figure 5 is a vertical axial section on the line
Figures 6 and 7 are views of modifications.
of figure 1.
Like figures and letters of reference indicate like paris.
As shown in figure 1, the general outline of the bosh plate a is that of a segment
of a circle, having at the ends projecting arms b which extend outward in the direction
of radii of the circle. The plate consists of two adjacent parallel pipes 2 and 3, whose
bases are connected by an integral web 4 preferably coextensive with the pipes. At
intermediate points along the sides of the pipes, they may be further united and
strengthened by connecting ribs 5, which extend across the intervening space a¹. The
pipes 2 and 3 are thus entirely distinct in their structure, and are connected only by
the web 4 and ribs 5. In cross section, the shape of the pipes is preferably oblong
as shewn in figure 2 and at their ends they are screw threaded as at b and c for the
attachment of pipe connections. For the latter purpose, the ends of the pipes are
somewhat reduced in diameter and are of cylindrical form, but instead of being reduced
abruptly at the discharge end, they taper gradually. This is a material feature of
advantage, since when thus made there is no lodging place for the collection of leaves
or other impurities which may be in the water and which would otherwise be apt to
choke the pipe.
The plates are built into the furnace walls as shown in figure 4 being laid hori-
zontally on the same course of bricks, with their radial ends in contact or
nearly so.
The inner concave sides of the plates lie at a short distance from the inside of the
stack and the ends of the radial arms of the pipes are made flush with the outside
of the wall. There is therefore a row, or several rows of brick & separating the
inside of the stack from the plates and there is also masonry e on the outer or
convex side of the pipe 2, and between the radial arms of the plate. The space a¹
between the pipes is filled in with brick or mortar or both, and this by uniting with
the layer of brick immediately above the plate, holds the latter still more firmly in
position and increases the coherency of the structure. The masonry e between the
arms forms solid and unbroken vertical columns extending from the base of the
stack to the level of the mantle. The existence of these columns has a very
material effect in strengthening the furnace stack, the external brickwork being
unbroken except where the arms 6 project from it. The bosh plates heretofore in
common use, which extend to the outer face of the wall, break the integrity of the
masonry and by interposing a rigid sheet of metal on which the mortar has no firm
grasp, very much weakens the structure, the more so on account of the unequal
limits of expansion and contraction of brick and metal. This disadvantage thus
stated is not apparent when the plates are applied as shown in figure 4, because the
brick columns e bind the stack together, and hold in its proper shape.
The advantage of this construction of furnace will be strikingly apparent to the
skilled blast furnace engineer.
It very greatly increases the solidity of the stack, as compared with furnaces
built with the old style plates described above; so much so in fact that even if both
water pipes of my improved bosh plate, should be burned out, the columns e would
impart the stability to the furnace necessary to successful operation, while the
presence of the few projecting arms of the plates, would be no material detriment
to the structure.

page_text: Water supply pipes are coupled to the ends of the pipes 2 and 3 in the ordinary
manner, and a constant current of water is maintained through the latter, the effect
of which is to cool the masonry and to retard the burning of the stack. When in
turn the boshes burn out so much as to expose the inner pipes 3 to the stock in the
furnace, and finally burn this pipe out, the construction of the bosh plate is such
that the outer pipe 2 is left intact, and by turning off the water from the inner
pipe and using the outer pipe only, the cooling influence of the water circulation is
still obtained. For this purpose the pipe 2 is preferably made of greater diameter
than the inner pipe as shown in the drawing, so that when the supply of water
through the latter is checked, the cooling of the other pipe may be sufficient to
conserve the stack.
I prefer to cast the bosh plates as a homogeneous casting in a single piece, using
as the material of their structure, phosphor-bronze, or other material not liable to be
corroded by impure water or heat. Pipes made of this material are therefore much
more durable than either cast or wrought iron pipes. It is difficult to cast these
hollow pipes unless their bore be of considerable diameter, but if they be of circular
section the proper diameter for this purpose would unduly increase their bulk and
thickness for use in bosh-plates. The desired result is however attained by making
the pipes of oblong cross section.
They are then easily cast and present a maximum area of cooling surface, without
being subject to the disadvantage of improper thickness. The principal object to be
gained by making the pipes separate from each other by the space a is for the purpose
of enabling any defect in casting the shells of the pipes to be readily discovered.
If cast with one side in common the formation of a blow-hole or other defect not
easily detected in testing might open a communicating channel between them which
in case of the burning of the inner pipe would destroy the whole plate because the
outer pipe would then leak directly into the furnace.
I do not desire to limit the scope of all of the following claims by the casting of
the pipes 2 and 3 in a single piece. They may be cast separately as shewn in figure 6
and be built into the furnace by seating one of them upon the laterally projecting
flange or web of the other. Nor do I desire to limit myself to the bosh plate having
radially projecting arms at both ends. If desired, only one of these arms may be
employed and the pipes 2 and 3 instead of being made distinct may together constitute
a single and continuous pipe which entering the plate through the single projecting
arm is reflexed at the other end of the plate and returns in the reverse direction
through the body of the plate, and through the arm at the end of which it has its
discharge. This construction is shewn in figure 7 and while on some accounts it may
be convenient it is subject to the objection that it affords but a single water-pipe, so
that the destruction of one of its arms would ruin the whole plate.
By the words "unbroken exterior" as used by me in this specification I mean an
exterior shell of masonry practically unbroken by the iron bosh plates that are built
into the interior part of the wall said exterior shell being continuous solid and
unbroken except where the water pipes or connections B. C. extend through it to the
outside, said connections however not being of sufficient size to affect injuriously the
strength and durability of the stack.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed I declare that what I
claim is :-
First. Bosh plates for blast furnaces consisting of adjacent connected waterways
substantially as set forth.
Second. Bosh plates for blast furnaces consisting of adjacent connected waterways
combined so as to be of segmental shape with a projecting arm or arms substantially in
the manner and for the purpose set forth.
Third. Bosh plates for blast furnaces having connected water ways with tapering
discharge openings substantially in the manner and for the purpose set forth.

page_text: Fourth. Bosh plates for blast furnaces having two independent waterways one of
which is of smaller area in cross section than the other substantially in the manner
and for the purpose set forth.
Dnied this at
Ր L
Per pro J. T. KING,
J. Johnson.