Improvements in Apparatus for Supplying and Heating Air for Water-tube Steam-boiler Furnaces.
Year: 1898

page_text: Date of Application, 8th Oct., 1898
Complete Specification Left, 6th July, 1899-Accepted, 12th Aug., 1899
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Supplying and Heating Air for
Water-tube Steam-boiler Furnaces.
I, JAMES HOWDEN, of 195, Scotland Street, in the County of Glasgow, North
Britain, Engineer, do hereby declare the nature of this invention to be as follows,
that is to say:
My said invention has for its object to provide improved apparatus for
advantageously and satisfactorily applying my well known system of forced
draught" to the furnaces of water-tube steam boilers, my improvements being
also applicable to what is known as "induced draught" apparatus.
My improved apparatus may be adapted to various existing constructions of
water-tube steam boilers. In the case of a boiler comprising a longitudinal
water-and-steam drum or cylinder, with tubes extending down therefrom on each
side to water boxes placed one along each side of a furnace which is below the
drum, I construct air casings at the sides of the drum, such casings being
provided with tubes up through which the fire gases pass from enclosed spaces
at the outer sides of the water tubes. The air casings are divided at about the
middles of their lengths, and air forced by a blower, enters at the middles of
the sides and proceeds in separate streams to the front and back ends of the
drum or boiler. In passing through the casings the air crosses and is heated by
the fire gas tubes; and in some cases its distribution over the surfaces of the
tubes is rendered approximately uniform by horizontal diaphragms.
At each end of the drum the air casings communicate with the upper parts of
spaces formed between the furnace casing of the boiler and outer metal shells;
and from the lower parts of these spaces the air passes through adjustable valves
into the furnace above the grate, and into the ashpit.
The furnace of such a boiler is usually of considerable length and the flames
and firegases proceed upwards from all parts of the fire instead of flowing along
as in ordinary internal furnaces, and there is consequently a difficulty in applying
sufficient air at the inner end of the furnace when the fire doors are at one end
only. To meet this difficulty I arrange the air-heating casings as hereinbefore
described to supply air to cased spaces at both ends of the boiler; and in con-
nection with the space at the back end of the boiler I provide valves for admitting
air above and below the grate at the back end of the furnace. These valves at the
back are connected by rods to the adjusting mechanism of the valves arranged
at the front end of the boiler for admitting air to the ashpit, and the valves so
connected are opened and closed together. At the front end, however, the valves
for admitting air above the grate are adjustable by separate levers, as it is,
generally, not necessary to close them when the other valves are closed.
In a boiler such as is hereinbefore described I prefer to have two fire doors at
the ends, and to divide the internal furnace space by a brick partition so that
when one fire door is opened for coaling the internal actions due to the opening
of the door, are confined to one internal compartment. In other modifications of

page_text: water-tube boilers I arrange the air-inlet valves, and the enclosed air spaces to
suit the particular arrangement in each case. Thus when the water tubes extend
down at only one side of the furnace and the fire doors are at the other side, there
may be valved inlets at the fire doors and others at one or both ends of the
furnace space. Or, in some cases, there may be valved air inlets at one or both
sides of the fire space, instead of, or in addition to, inlets at one or both ends.
The improved arrangements hereinbefore described besides supplying heated
air for combustion of the fuel and thereby securing a large economy in fuel,
also prevent the great radiation of heat into the boiler rooms from the casing
of water-tube boilers and also the injuriously high temperature of the fire gases
in uptakes and funnels which necessarily occurs with the use of the closed stoke-
hold system of forced draught applied directly to the furnaces which has hitherto
been generally used in such boilers.
Dated this Seventh day of October 1898.
EDMUND HUNT,
Applicant's Agent.
Improvements in Apparatus for Supplying and Heating Air for
Water-tube Steam-boiler Furnaces.
I, JAMES HOWDEN, of 195, Scotland Street, in the County of Glasgow, North
Britain, Engineer, 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, that is to say:—
My said invention has for its object to provide improved apparatus for
advantageously and satisfactorily applying my well known system of "forced
draught to the furnaces of water-tube steam boilers, my improvements being
also applicable to what is known as "induced draught" apparatus.
My improved apparatus may be adapted to various existing constructions of
water-tube steam boilers, two different types of boilers being, by way of example,
shown on two accompanying sheets of explanatory drawings as fitted with my
improvements.
Figure, 1, Sheet. 1, is one half an end elevation the other half a partial
vertical section. Figure, 2, is a horizontal section of air-heating apparatus and
Figure, 3, is a vertical longitudinal section showing application of my improve-
ments to one type of water-tube boiler. Figures, 4, and 5, Sheet, 2, are a sectional
front elevation and a vertical section showing application of my improvements
to another, namely the Belleville type of water-tube boiler. In these drawings
the same reference letters are used to mark the same or like parts wherever
they are repeated.
In the case of the boiler shown in Figures, 1, 2, and 3, which comprises a
longitudinal water-and-steam drum or cylinder, A, with tubes, B, extending
down therefrom on each side to water boxes, C, placed one along each side of a
furnace, D), which is below the drum, A. I construct air casings, E, at the
sides of the drum, A, such casings being provided with tubes, F, up through
which the fire gases pass from enclosed spaces, G, at the outer sides of the water
tubes, B. The air casings, E, are divided at about the middles, H, of their
lengths, and air forced or drawn by a blower, (not shown) enters at the middles, H,
of the sides through a duct, J, and proceeds in separate streams to the front and
back end of the drum, A. In passing through the casings, E, the air crosses and
is heated by the fire gas tubes, F; and its distribution over the surfaces of the

page_text: tubes is rendered approximately uniform by horizontal diaphragms, K. The
diaphragms are, however, not always required.
At each end of the drum, A, the air casings, E, communicate with the upper
parts of spaces, L, formed between the furnace casings, M, of the boiler and outer
metal shells or casings, N; and from the lower parts of these spaces the air
passes, as hereinafter described, into the furnace, D, above the grate and into the
ashpit, P. The air casings, L, prevent radiation and loss of heat from the parts
of the boiler shell which they cover, the air taking up and thus utilising such
heat.
The furnace, D, of such a boiler is usually of considerable length and the flames
and fire gases proceed upwards from all parts of the fire instead of flowing along
as in ordinary internal furnaces, and there is consequently an insufficient
supply of air at the inner end of the furnace when the fire doors, Z, are at one
end only. To meet this difficulty I arrange the air-heating casings, E, and the
spaces, L, as herein before described to supply air to cased spaces or distributing
boxes, R, r, S, at both ends of the boiler and in connection with the space, S,
at the back of the boiler I provide valves, T, for admitting air above and below
the grate at the back end of the furnace. These valves, T, at the back are con-
nected by rods, U, to levers V, for adjusting valves, W, arranged at the front
end of the boiler for admitting air to the ashpit, P, and the valves so connected
are opened and closed together. At the front end, additional valves, X, are
arranged for admitting air to the part of the distributing boxes, R, above the
grate, the valves being adjustable by separate levers, Y, as it is, generally, not
necessary to close them when the other valves,T, W, are closed."
In a boiler such as is herein before described I prefer to have two fire doors, Z,
at the end; and the internal furnace space may be divided by a brick partition
so that when one fire door is opened for coaling the internal actions due to the
opening of the door, are confined to one internal compartment.
In other modifications of water tube boilers I arrange the air-inlet valves and
the enclosed air spaces to suit the particular arrangement in each case. In the
modification shown in Figures, 4, and 5, the air-heating casings, E, occupy
space directly above the water tubes, B, and the heated air descends through
spaces, L, at the sides of the main furnace casing of the boiler instead of at
the ends as in the first modification, the air proceeding from the lower ends
of such spaces to the front and back ends of the furnace and also to the side of the
fire space beneath the fire grate, D, the air inlet valves being arranged and
adjusted as shown.
When the water tubes (B) extend down at only one side of the furnace and the
fire doors are at the other side there may be valved inlets at the fire doors and
others at one or both ends of the furnace space. Or, in some cases, there may be
valved air inlets at one or both sides of the fire space, instead of or in addition
to inlets at one or both ends.
The improved arrangements hereinbefore described besides supplying heated
air for the combustion of the fuel and thereby securing a large economy in fuel,
also prevent the great radiation of heat into the boiler rooms from the casings
of water tube boilers and also the injuriously high temperature of the fire gases
in uptakes and furnaces which necessarily occurs with the use of the closed
stokehold system of forced draught applied directly to the furnaces which has
hitherto been generally used in such boilers.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:.
1. Apparatus for supplying and heating air for water-tube steam-boiler
furnaces, comprising in combination means for forcing or drawing air through
the apparatus and furnace casings in which the air is heated by means of tubes
through which the outgoing fire gases pass, enclosed spaces or passages through

page_text: which the heated air descends to distributing boxes at the front and back ends
and sides of the furnace, and valves for controlling and regulating the distribution
substantially as and for the purposes hereinbefore described.
2. In apparatus for supplying and heating air for water-tube steam-boiler
furnaces, spaces formed between the front and back ends of the boiler and outer
casings or between the sides of the boiler and outer casings, which spaces com-
municate at the upper end with air heating casings and at the lower end with
air distributing boxes substantially as and for the purposes hereinbefore described
and as shown in Figures, 1 to 5, of the accompanying drawings.
3. In apparatus for supplying and heating air for water-tube steam-boiler
furnaces air admission-valves at the back end of the furnace these valves being
connected by rods to levers used for adjusting air admission valves arranged at
the front end of the furnace substantially as and for the purposes hereinbefore
described.
1 11 111 1 T..1...1000

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