Improvements in Water-tube Steam Generators.
Year: 1895

page_text: Date of Application, 8th Mar., 1895-Accepted, 8th June, 1895
COMPLETE SPECIFICATION.
Improvements in Water-tube Steam Generators.
We, JACQUES AUGUSTIN NORMAND, and PIERRE SIGAUDY, of Havre, in the
Republic of France, Engineers, 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 :-
The lightness of multitubular steam generators in which water circulates through
the tubes is chiefly due to the small volume of water which the said generators
contain. In multitubular steam generators so constructed however, more particu-
larly in the marine type, variations in pressure are very considerable, so that when
several generators are coupled together for supplying steam to one engine the
regular distribution of the feed water to the different boilers gives place to serious
difficulties since the water has a tendency to enter the boilers where the pressure is
lowest and where the discharge is consequently the smallest.
It would therefore
seem useful to diminish as much as possible the number of generators thus coupled
together since the work and supervision which a regular distribution demands
would be diminished in like proportion.
There are moreover advantages gained by the use of coupled generators more
especially in respect of the pipes, the cocks and valves, the reduction of temperature
of the compartments and the space occupied by the generators which in the case
where several generators are in use outweigh the disadvantages such as that two
generators instead of one become unavailable in the case of damage and that there
is a greater variation of the level of the water at the ends of the upper reservoir
which is caused in the case of marine boilers by the motion of the sea and the
variations in the trim of the boat.
Steam generators of the Normand type present the following characteristics;
lightness in construction, high efficiency and capability of supporting without
langer a very intense firing.
This invention has for its object to facilitate the application of steam generators
of the class we have described to the most powerful engines by duplicating the
heating and grate surfaces in the two well known types of these generators, the first
type being that in which the chimney is situated at the end of the generator
opposite to the front part thereof, and the second in which the gases are caused to
return to the chimney which is situated near the front of the generator.
Under
these new conditions steam generators of the Normand type may be used with great
advantage on very high speed large steamers and cruisers.
The accompanying drawings illustrate by way of example tubular steam
generators constructed according to this invention, Figures 1, 2 and 3 relating to
the first type of a Normand steam generator.
Figure 1 is a vertical longitudinal section of the steam generator taken along the
axis thereof,
and
Figure 2 shows the said generator half in front elevation half in cross section,
Figure 3 is a section (taken on the line X Y Figure 2) of the water tubes.
A A' are the front ends of two steam generators C which are coupled together so
as to form a single steam generator. B B' are two side cylindrical vessels or
receivers into which the lower ends of the water tubes a open, while the upper ends
of the said tubes from each receiver B B terminate in the generator C.
DD' are
bridges situated at the ends of the furnaces b. E E E E indicate the return
D
07

page_text: water tubes situated outside the furnaces. Hollow tie rods F F F F containing
water connect the receivers B B' to the generator C near the central part thereof.
GG are inverted bridges under which the heated gases or products of combustion
from the furnaces pass, as shown by the arrows, before entering the smoke box.
A plate H divides the said smoke box into two parts and extending upwardly into
the chimney I separates the currents of gas and products of combustion from the two
furnaces so that whatever may be the difference of the pressures of the air or of the
draught in the two furnaces, the chimney I is made common to the two united
generators C.
The two generators C communicate with each other by one or more tubes or
pipes c so as to offer as little resistance as possible to the passage of the products
of combustion from the furnaces to the chimney and to reduce the motion of the
water in a longitudinal direction in the said generator C. The motion of the water.
can be further diminished both in the generator C and in the receivers B B¹ by.
means of baffle plates suitably arranged.
The steam may be taken off from either or both of the two generators C which
constitute when connected the one main generator.
The junction pipes c which form the communication between two generators
should be of sufficient size to prevent any appreciable difference in pressure and
level of the water in the said two generators.
The feed water is preferably supplied to each of the generators so as to secure &
uniform production of steam. The apparatus is preferably constructed so as to be
capable of being readily separated when desired into two parts so as to facilitate its
transport and erection.
When there are two steam generators of the new type arranged side by side in
the width of the boat and with receivers arranged parallel to the longitudinal axis
of the boat the chimneys of the two generators may be united according to this
invention so as to form one.
Figures 4, 5 and 6 shew two generators so arranged, Figure 4 being a longitudinal
elevation of generators of the first type herein before described, Figure 5 a longi-
tudinal elevation of generators of the second type that is to say generators in which
the products of combustion are caused to return to the chimneys situated at the
front ends of the said generators, and Figure 6 is a transverse view common to
both types of generators.
The various parts of the said generators are similar to those which we have
already described with reference to Figures 1, 2 and 3 and by reference to these
figures their operation will be readily understood.
When the vessel is sufficiently broad in its beam generators constructed according
to this invention may be arranged therein so that their longitudinal axis is at right
angles to the axis of the vessel. The stoke holds being situated longitudinally on
both sides of the vessel. To facilitate such an installation which presents several
advantages chiefly in connection with the service of the coal bunkers and the
arrangement of the chimneys the length of the said generators may be reduced by
dispensing with the sinoke boxes separated by the plate H as shown in Figure 1
and causing the heated products of combustion to leave by lateral passages near
the bridges D D¹. A passage for the said gases being provided by opening the
screen formed by the two longitudinal rows or series of the outer heating tubes the
said passage starting from the said bridges and extending through a certain length
towards the frouts of the generators.
This arrangement is illustrated in Figures 7 and 8 of the accompanying drawings,
Figure 7 showing in end view three generators arranged across the axis of the
vessel and Figure 8 showing a side view of such generators.
Figures 9, 10 and 11 illustrate on a larger scale one of these generators.
Figure 9 is a vertical longitudinal section of the said generator, taken along the
axis thereof. Figure 10 shows the said generator half in front elevation and half
in cross section, and Figure 11 is a section, taken on the line X Y Figure 10 of
the water tubes.

page_text: The various parts of the said generators are similar to those already described
with reference to Figures 1, 2 and 3, and are indicated by corresponding letters of
reference.
This invention is not limited to the precise details described and illustrated in
the drawings the various parts being capable of modifications to suit the require-
ments of particular installations.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. The combination of water tube generators of the types described in such a
manner that the said combined generator contains two distinct furnaces the water
and the steam contained in the two parts being in direct communication with each
other by means of pipes or junctions of a size or section sufficient to prevent a
difference of pressure or water level in the said parts whatever be the intensity of
firing substantially as hereinbefore described.
2. The several arrangements of the combined generators substantially as
described and illustrated by the examples shewn in the accompanying drawings.
Dated this 8th day of March 1895.
JOHNSONS & WILLCOX,
Agents.