Improvements in Water-tube Steam Generators.
Year: 1897

page_text: Date of Application, 19th June, 1897
PROVISIONAL SPECIFICATION.
Improvements in Water-tube Steam Generators.
I, CHARLES FERRAND, of 213bie, Boulevard St. Germain, Paris, in the Republic
of France, Engineer, do hereby declare the nature of this invention to be as
follows:-
Multitubular steam generators of the "Du Temple" type as at present used in
torpedo-boats are not economical when used in large vessels owing to their
triangular shape and especially as owing to their limited height; they require
large floor space and do not utilize the vertical space. They are economical only
when worked at a rate not exceeding 200 kilogrammes per square meter of grate
surface and this of course, necessitates inconveniently large grates.
This invention has for its object to provide a multitubular boiler, the shape of
which is essentially that of a parallelipipedon, and is highly suitable for use in
large vessels and for the utilization of extensive and effectual heating chambers,
and moreover effects great economy when worked with forced draught. It consists
of two multitubular boilers one over the other. These two boilers are independent
of each other as regards feed and emission of steam; they have one grate in
common.
By means of fire-screens formed by the tubes themselves the flames and hot pro-
ducts from the fire are so directed as to pass directly to the chimney or to first
return toward the front side, as required.
I will describe the application of the invention to a generator wherein the
flames and hot products from the fire return towards the front side.
The heating surface is formed by the boiler tubes which connect the upper
collectors with the lower collectors.
These tubes are arranged as cylinders for the lower boiler, and for the upper
boiler.
In the forward portion of the boiler, a cylinder of tubes is formed by tubes.
placed into contact, whereby a fire-screen is formed which compels the flames to
pass from the front toward the back.
On the second portion of the cylinder the tubes are spaced; the flames return
to the front by passing across the tubes. For this purpose the cylinder of tubes
forms a perfect screen at the rear; whereas at the front, and only at that portion
which communicates with the tubes of the second boiler, the said tubes are spaced.
The same is the case with those of the cylinder of tubes of the second boiler. The
flames in this case pass between the tubes of the second boiler by travelling toward
the rear.
The tubes of the cylinder which form a screen at the base, are separated
at the rear, above, whereby the flames are enabled to travel toward the chimney.
With these arrangements, it may be calculated that, when the lower boiler is being
worked at high pressure, (300 kilogrammes of fuel per square meter of grate),
the upper boiler will be heated by the partly cooled gases, under the same condi-
tions as if the same were heated by a grate burning 100 kilogrammes per square
meter. In the same manner, if 500 kilogrammes of fuel per square meter of grate
be burnt, the second boiler will have to utilise a quantity of heat which may be
compared with that produced by the combustion of from 200 to 300 kilogrammes

page_text: per square meter of grate surface. From this it results that if the lower boiler
be worked at a low economical pressure, the whole heating apparatus will neverthe-
less work economically, since the saving will be realized by the upper boiler,
worked at a reduced pressure.
It is evident that this improved apparatus realizes in boilers, what the double
and triple expansion does with regard to engines, or to heaters, since the upper
boiler absorbs the whole heat which would be lost if the lower boiler were heated
excessively, as a single boiler.
In constructing the lower boiler, the tubes are made to terminate in the steam
space whereby the circulation is more reliable, especially when worked at high
pressure. In the upper boiler, on the contrary, which is never worked excessively,
the tubes terminate at the lower part.
The distribution of tubes generally employed in multitubular boilers fitted with
small tubes of all types, presents from the point of view of an efficient utilization
of heat, the following serious defects.
The hot gases, on leaving the furnace, are cooled by meeting the closely arranged
sets of tubes; they burn defectively, as the frequent re-ignitions occurring in the
chimney clearly prove.
The tubes forming the sides of the combustion chamber, are simultaneously
heated by direct radiation and by contact, they on their part alone evaporate from
50 to 60 per cent. of the total production of the boiler, there is every reason to
suppose that in many cases their maximum evaporating limit has been nearly
reached.
It therefore is advantageous to so arrange the tubes which are to come in direct
contact with the fire, as to expose to the intense heat of the fire only as small a
portion as possible of their longitudinal extent, and to reduce the number of
tubes so as to avoid any rapid cooling of the gases when leaving the furnace.
The use of two super-posed boilers permits of realizing these two desiderata:
The system of tubes of this lower boiler may according to this invention be
divided into four groups, which cross each other, leaving between them secondary
combustion chambers. The first group comes into direct contact with the fire only
at its base, the second group only at its top, the third group, owing to the distances
maintained between the tubes is still exposed to the direct radiation from the
furnace; and finally the fourth group occupies a position which may be compared
with the systems of tubes, used in boilers at the present time.
The upper boiler should be placed as high as possible above the lower boiler so
as to increase the intermediate combustion chamber. This height is fixed accord-
ing to local convenience.
According to circumstances, screens formed by the horizontally placed tubes
may be employed for directing the flames, and heated products into the upper
body. The feeding is effected within the steam space and the feed is conveyed by
separate apparatus.
The steam outlets are likewise separate and supply either a single collector, or
preferably two different collectors. The main engine may for example be supplied
from the lower boiler and the secondary apparatus from the upper boiler.
In the case of large vessels, the installation of generators according to this
invention may be double ended."
"
The apparatus is intended for forced draught and for use when employed at a
combustion rate of at least 300 kilogrammes per square meter of grate.
In cases where, for instance in a roadstead, only a small quantity of steam corre-
sponding to the production of the lower boiler, is required, the upper boiler will be
converted into the economizer by connecting both by suitable piping provided
with cocks.
Dated this 10th dev of Luno 1907
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.

page_text: Improvements in Water-tube Steam Generators.
I, CHARLES FERRAND, of 213bis, Boulevard St. Germain, Paris, in the Republic
of France, 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:-'
Multitubular steam generators of the "Du Temple" type as at present used in
torpedo-boats are not economical when used in large vessels owing to their
triangular shape and especially as owing to their limited height, they require
large floor space and do not utilize the vertical space. They are economical only
when worked at a rate not exceeding 200 kilogrammes per square meter of grate
surface and this of course, necessitates inconveniently large grates.
This invention has for its object to provide a multitubular boiler, the shape of
which is essentially that of a parallelopiped, and is highly suitable for use in large
vessels and for the utilization of extensive and effectual heating chambers, and
moreover effects great economy when worked with forced draught. It consists of two
multitubular boilers one over the other. These two boilers are independent of each
other as regards feed and emission of steam; they have one grate in common.
By means of fire-screens formed by the tubes themselves the flames and hot
products from the fire are so directed as to pass directly to the chimney or to first
return toward the front side as required.
In order that my invention may be well understood, I will describe the same
with reference to the accompanying drawings, in which an arrangement is illus-
trated wherein the flames and hot products from the fire return toward the front
side.
Figure 1 represents a steam generator half in front elevation and the other half
in vertical section, the latter shewing the arrangement of the tubular system.
Figure 2 represents the generator in side elevation.
Figures 3, 4 and 5 are sections taken on the lines A. B, C D and E F, respectively,
of Figure 1 to illustrate the tubular system.
Figure 6 is a half elevation and half vertical section shewing a modification of
the generator represented in Figure 1.
Figure 7 is a side elevation of the generator thus modified.
Figure 8 is a diagrammatic view of this modification.
Figures 9, 10 and 11 illustrate the distribution of the tubes and their combina-
tion with the three collectors of the lower portion or boiler, Figure 9 representing
the surfacial development of the lower left hand collector; Figure 10 the surfacial
development of the upper collector and Figure 11 that of the lower right hand
collector.
1 and 4 in Figure 1 shew the upper collectors of the two boilers, 3 and 6 the
lower collectors; and 2 and 5 the respective water return pipes or passages.
The heating surface is formed by the boiler tubes which connect the upper
collectors with the lower collectors.
These tubes are arranged in sets which I term cylinders 7, 8, 9, 10, 11, 12, 13,
14, 15, 16 for the lower boiler, and 17, 18, 19, 20, 21, 22, 23, 24, 25, 26 for the
upper boiler.
In the forward portion of the boiler, sets or cylinders of tubes 7, 8 are formed by
tubes placed in contact, Figure 3, whereby a fire screen is formed which compels
the flames to pass from the front toward the back.
On the second portion of the cylinder the tubes are spaced, Figure 3, and
the flames return to the front by passing across the tubes. For this purpose also the
sets or cylinders of tubes 15, 16 form a perfect screen from front to rear at the

page_text: base. At the front, and only at that portion opposite the tubes of the second
boiler, the said tubes 15, 16 are spaced, as shewn in Fig. 4. The same is the case
with those of the set or cylinder of tubes 17, 18 of the second boiler. The flames
in this case pass between the tubes of the second boiler by travelling toward the
rear. The tubes of the cylinder 25, 26, which form a screen at the base, are
separated at the rear, above, Figure 5, whereby the flames are enabled to travel
toward the chimney 27, Figure 1, the tubes of the several sets or cylinders com-
prised between 7 and 16, 17 and 26 are arranged quincuncially so as to better
divide and distribute the flames and hot products of combustion. With these
arrangements, it may
be calculated that, when the lower boiler is being worked at
high pressure, (300 kilogrammes of fuel per square meter of grate), the upper boiler
will be heated by the partly cooled gases, under the same conditions as if the same
were heated by a grate burning 100 kilogrammes per square meter. In the same
manner, if 500 kilogrammes of fuel per square meter of grate be burnt, the second
boiler will have to utilize a quantity of heat which may be compared with that
produced by the combustion of from 200 to 300 kilogrammes per square meter of
grate surface. From this it results that if the lower boiler be worked at a low
economical pressure, the whole heating apparatus will nevertheless work economi-
cally, since the saving will be realized by the upper boiler, worked at a reduced
pressure.
It is evident that this improved apparatus realizes in boilers, what the double
and triple-expansion does with regard to engines, or to heaters, since the upper
boiler absorbs the whole heat which would be lost if the lower boiler were heated
excessively, as a single boiler.
In constructing the lower boiler the tubes are made to terminate in the steam
space whereby the circulation is more reliable, especially when worked at high
pressure. In the upper boiler, on the contrary, which is never worked excessively,
the tubes terminate at the lower part.
The distribution of tubes generally employed in multitubular boilers fitted with
small tubes of all types, presents, from the point of view of an efficient utilization
of heat, the following serious defects:
The hot gases, on leaving the furnace, are cooled by meeting the closely arranged
sets of tubes; they burn defectively, as the frequent re-ignitions occurring in
the chimneys clearly prove.
The tubes forming the sides of the combustion chamber, are simultaneously
heated by direct radiation and by contact. They, on their part alone, evaporate
from 50 to 60 per cent. of the total production of the boiler: there is every reason
to suppose that, in many cases, their maximum evaporating limit has been nearly
reached.
It, therefore, is advantageous to so arrange the tubes which are to come in direct
contact with the fire, as to expose to the intense heat of the fire only as small a
portion as possible of their longitudinal extent, and to reduce the number of
tubes so as to avoid any rapid cooling of the gases when leaving the furnace.
The use of two superposed boilers permits of realizing these two desiderata:
Figure 6 illustrates the arrangements to be applied to the lower boiler.
The system of tubes of this lower boiler may according to this invention be
divided into four groups which cross each other, leaving between them secondary
combustion chambers. The first group (tubes 1 and 2) comes into direct contact
with the fire only at its base; the second group (tubes 7, 8, 9, 10, 11, 12) only at
its top; the third group (tubes 3, 4, 5, 6) owing to the distances maintained
between the tubes is still exposed to the direct radiation from the furnace; and
finally the fourth group (tubes 13, 14, 15 and 16) occupies a position which may
be compared with the systems of tubes, used in boilers at the present time.
The upper boiler should be placed as high as possible above the lower boiler,
so as to increase the intermediate combustion chamber. This height is fixed
according to local convenience.
According to circumstances, screens, formed by the horizontally placed tubes,

page_text: may be employed for directing the flames and heated products into the upper body.
The feeding is effected within the steam space and the feed is conveyed by
separate apparatus.
The steam outlets are likewise separate and supply either a single collector, or,
preferably, two different collectors. The main engine may, for example, be
supplied from the lower boiler and the secondary apparatus from the upper
boiler..
In the case of large vessels the installation of generators according to this inven-
tion may be double ended."
66
The apparatus is intended for forced draught and for use when employed at a
combustion rate of at least 300 kilogrammes per square meter of grate.
In cases where, for instance in a roadstead, only a small quantity of steam,
corresponding to the production of the lower boiler, is required, the upper boiler
will be converted into the economizer, by connecting both by suitable piping
provided with cocks.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I declare that what I
claim is:
1. A steam generator composed of two multitubular boilers one above the other
and independent of each other as regards feeding and discharge of steam, but
being heated by one furnace common to both; the upper boiler being convertible
into an economizer, when there is no need for working with high pressure; sub-
stantially as herein described with reference to the accompanying drawings.
2. A steam generator composed of two multitubular boilers, the system of tubes
of the lower boiler being formed by four groups of tubes crossing each other and
constituting the sides of the combustion chamber; this arrangement being
especially suitable for distributing the heating effect resulting from the direct
contact with the fire, and less apt to rapidly cool the hot gases from the furnace;
substantially as herein described with reference to the accompanying drawings.
Dated this 24th day of February 1898.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.