Improvements in Multitubular Steam Boilers.
Year: 1889

page_text: Date of Application, 21st Sept., 1889-Accepted, 9th Nov., 1889
COMPLETE SPECIFICATION.
Improvements in Multitubular Steam Boilers.
I, TBÉOPHILE PRESSARD of 42 Boulevard Bonne Nouvelle, 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 :-
The invention has for its object improvements in multitubular steam boilers with
removable tools.
In the accompanying drawings, I have represented a specimen of a boiler con-
structed according to my invention, and of which the following is a description.
Figure is a vertical section of the tubular part of the boiler.
Figure 2 represents the same boiler partly in plan and partly in horizontal section
drawn on the line III. IV of figure 1.
Figure 3 is a front view with half a section drawn on the line I. II of figure 1.
Figure 4 is a back elevation.
Figure 5 is a vertical section of the boiler drawn to an enlarged scale.
Figure 6 represents in horizontal section a part of the same tubular portion.
Figures 7 and 8 represent a modification of the union of the bolts with the tubes.
This generator is composed, 1st, of inclined evaporating tubes, 2nd, of boxes, 3rd, of
a collector and, 4th, of a reservoir.
Two tubes connected to the same box, form an evaporating element. A larger or
smaller number of boxes and tubes superposed vertically, form a series.
The evaporating tubes are of two different sizes.
The tubes placed at the lower part of the boiler within the furnace, producing steam
in much greater quantity than the tubes placed immediately above, have a con-
siderably larger diameter than the upper tubes, in order to facilitate the liberation of
steam and the entrance of the water to replace that which has been transformed into
steam.
The large evaporating tubes C are arranged in couples, the one exactly below
the other, so that the lower tube may receive all the action of the furnace and
produce much more steam than that placed immediately above, to which it serves
as a screen; there results from this arrangement, and from the inclination of the
tubes, that the globules of steam formed in the lower tube pass directly into the
collector B by the said lower tube, and are immediately replaced by the feed
water, which descends from the reservoir by the collector and the upper tube of
the element. It may be said that the lower tube of the element is the evaporator,
and that the upper tube of this same element is the heater, for, in recapitulation,
the water is heated in the upper tube, but is evaporated above all in the lower
tube. The arrows indicate the flow of the water, the arrows 6 the course of
the steam, and the arrows c the course of globules of steam produced in the upper.
tube of each element.
As has been above mentioned, the two large lower tubes are placed one above
the other to obtain the circulation of the water. To attain the same result in the
upper tubes F, these latter are arranged quincunxially, that is to say, in zigzag
lines, as represented at figure 3, in order that this arrangement may distribute
more equally the heat on each of the tubes; that which is placed at the lower
part of each element will always be more heated than the upper tube. This quin-
cunxial arrangement has further the result of better cooling the gases by compelling
them to circulate in zigzag lines, and consequently to lick all the evaporating
surfaces. Nevertheless the upper tubes of each element may be placed in the
manner as the two large lower tubes, that is to say, the one above the
same

page_text: other in vertical line, and then arranging or not, as, may be desired, the elements
quincunxially.
The element composed of large tubes, being that which produces the most steam,
is also that in which the greatest deposit will be produced. In order to maintain
the tubes of the said element constantly in a perfectly clean condition, the con-
necting boxes D of these tubes, are. arranged so as to have a mud or deposit.
box. These deposits are removed under pressure by the aid of blow off cocks E,
arranged for this purpose in the front, see figure 5.
The inclination of the tubes and the difference of density of the two fluids, cause
a very rapid circulation of water, sufficient to cause the current to carry with, it.
the deposits which become separated from the water by the evaporation of the
latter.
The water, and the, steam, arriving in the collector B, undergo a change of
direction particularly favorable to the mechanical separation of the deposits, which
will fall to the bottom of the said collector, whence they are withdrawn by means
of blow off cocks, or by manholes V.
The feed water injected into the steam at the back of the reservoir A is deprived,
under the influence of the high temperature, of the greater part of the calcareous
salts which it contains in solution. It arrives thus hot and nearly pure into the
evaporating, tubes, in which the small amount of deposit which it yet contains in
solution, is separated by the evaporation and is drawn into the collector B by the
violence of the current.
•
The steam dome. is placed as far as possible from the upper orifice of the col-
lector, that is to say, from the point of arrival of the steain, in order that the
latter may free itself from the water that it might have taken up with it. To
secure again the dryness of the steam, a superheater H, which receives the steam
from the reservoir A by a pipe 1, is placed above the generator, between the pipe I
and the generator A, in such a manner that the gases are compelled. to pass through
it on their way to the chimney, from the superheater the steam passes to the valve J
of the steam pipe...
To obtain the greatest possible utilization of the fuel, the cluster of tubes has
been arranged in two separate parts by a suitable partition K. The first part,
considerably more than the second, has been placed within the furnace, in order
to take advantage of all the heat; a screan L, placed over the upper tubes, compels
the gases to pass to the front, in order to traverse the superheater H and Leat
the lower part of the reservoir A; the gases then descend into the second part
of the cluster of tubes, where, they are deprived of the heat unnecessary for the
draught.
1.7
The arrows (figure 1) show the movement of the gases. In order that all the
tubes may be capable of being, rapidly dismounted, they have been provided at
the back, from the side of the collector, with a forked bolt rivetted on the tube
and traversing, the collector B from one side to the other, the back of the said
collector serving as support to the nut of the forked bolt n. In front the tubes
have web-bolts m, likewise rivetted to the tubes and traversing, from cue side to
the other, the union boxes D and G. To facilitate the rivetting of the bolts on
the tubes, I may employ, instead of the forked bolts, simple. bolis traversed by the
fivets and flat to prevent any resistance to the water in its passage into the section
thus contracted, (see figures 7 and 8 ;) be it as it may, these bolts are thus arranged
so that one, may easily examine the tubes, and in order that the union box "G" may
be provided with a man-hole cover U offering every security.
The accidents possible with the bolts ordinarily employed in other generators
are thus avoided, as also the annoyances, necessarily accompanying the rupture, of
the joints of the stoppers, so delicate that they are influenced by the dilatation of
the tubes.
5
The tubes, conical at their ends, are forcibly pressed into their places without cement;
the dry metallic ioint thus obtained is absolutely water tight.

page_text: To remove a tube from the collector or from the boxes, it is only necessary to give
a biow of hammer upon the bolt, the nut having been previously removed.
Beyond the special arrangements of my new generator which have above
described, ny boiler is completed by the ordinary appliances of similar apparatus,
that is to say:
A metallic envelope M, supporting the masonry which serves as support to the
boiler.
Doors N permit the examination of the union of the tubes and the cleaning of the
cluster of tubes.
The furnace O and its ash box l' are provided with doors, and the masonry which
constitutes them is either of fire clay bricks Q, or of ordinary bricks R; S is the
smoke flue.
Having now particularly described and ascertained the nature of my said inven-
Lion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The arrangement of the tubes in couples, thus forming a complete evaporating
element of U form, these tubes having the same inclination and connected by a single
box, and both communicating with the collector B, the one for feeding the element,
the other for producing the steam and conducting it to the said collector.
2. The mode of attaching the tubes by web and forked bolts, rendering the tubes
removable and absolutely independent of the man-hole.
3. The boxes of communication or of uniou of the two tubes arranged with a
manbole absolutely independent of the joint of the tubes.
THEOPHILE PRESSARD.
By Harris & Mills,
23, Southampton Buildings, London, Agents.