Improvements in Multitubular Steam Generators We
Year: 1894

page_text: Date of Application, 22nd Dec., 1894-Accepted, 18th May, 1895
COMPLETE SPECIFICATION.
Improvements in Multitubular Steam Generators
We JACQUES AUGUSTIN NORMAND, MARIE EMILIE NORMAND and FRANÇOISE
ELISABETH NORMAND trading as La Societe Augustin Normand & Company of
67 Rue de Peirey Havie in the Republic of France, do hereby declaro 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.-
This invention relates to improvements in the construction of steam generators of
tho class described in the French Patent No. 203,008 dated the 7th January 1890
granted to us.
Boilers of this class comprise heating tubes the greater part of which open or
discharge below the level of the water contained in an upper reservon, and the hot
gases in the boilers, after having circulated round the tubes, pass off through the
chimney situated at the end opposite to the front of the boiler.
Steam generators constructed in this manner should yield more steam, and at a
less cost than the boilers in which the water is made to circulate within the tubes
and where the chimney is situated unmediately above the giate inasmuch as the
combustion chamber is of greater capacity, the position of the tubes more closely
approaches the vertical line and the sectional area available for the passage of the
gases is less and the course of such gases is further extended. These cucumstances
nie calculated to promote thorough combustion, an active cu culation of water, as
uniform as possible a utilization of the heating surface, and a rapid energetic
displacement of useful gases capable of assisting the transmission of heat
It has however been found that the yield of steam generators of the construction
referred to, though slightly greater than that of the older boilers, docs not offer
over the latter the superiority expected.
In order that this may be more clearly understood reference will be made to the
accompanying drawings in which,
Figures 1 and 2 are respectively a longitudinal and a transverse section of a
boiler of the type referred to as at present constructed, c. one of which the yield is
considered insufficient.
Figure 3 is a section of one of the series of tubes, taken on line X Y Figure 1.
A is the front of the boiler, immediately connected with the heating chamber.
B B' are side reservoirs or chambers receiving the lower parts of the heating tubes.
C is the central reservou or chamber receiving the upper ends of the said tubes.
Dis the main bridge situated at the end of the grates. EE', E" are water return
tubes situated outside the funnce. F 15 an inverted end-bridge under which the
hot gases are caused to pass before entering the smoke-box and chimney. GH I are
J is tho smoke-
apertures provided in the upper portion of the inverted bridge F
box. K is the chimney.
In boilers of the present construction the hot gases pass among the lateral series
of pipes though apertures provided throughout the length of the grates. As a rule
these apertures or passages occupy the lower part of the series of tubes only, as
from a to Figure 2. In some cases, however, they have extended further
upwards, say from a to cand in any case, as before stated, the said apertures extend
throughout the length of the gates.
Suitable brickwork d prevents the flame from entering the upper part of the
series of tubes.

page_text: It will readily be seen from the arrows in Figure 1 which indicate the most
probable course of the hot gases that—
(1) The gases which enter the series of tubes in the vicinity of the bridge D
have but a short distance to travel before they each the chimney, they therefore
escape at a very high temperature and may even carry flames into the chimney.
(2) The upper part of the Ecies of tubes next to the front, is necessarily more or
less avoided by the said gases; aud-
(3) The gases drawn into the chimney which they enter upon passing under the
inverted bridge F must needs take the shortest way leading in that direction, and
therefore but imperfectly heat the upper portion of the series of tubes
Such 16, of necessity, the effect produced, in spite of the tendency of the gases to
se, and notwithstanding the provision of the small apertures G H I, the object of
which is to cause the gases to follow the upper part of the series of tubes situated
next to the chimney.
It will thus be seen that in Normand's boiler of the type first introduced and
such as has been constructed since the heating surface is taken advantage of in a
manner which is far from perfect and proves to be the less satisfactory, the greater
the height of the apparatus. This is the more unfortunate as an extension of the
steam generator of this class in the upward direction constitutes a very considerable
increase of the heating surface, while the increase of weight and expenditure
mvolved is very slight. This is a valuable property of the boiler which under the
present encumstances, it has been impossible to turn to account
The object of the arrangements herein desoribed is to enable the series or bundles
of heating tubes to be utilised more fully than has been done hitherto, both in height
(or depth) and length, and thereby to provide for a better combustion of the gases
by compelling them to remain for a longer space of time in the combustion chamber
before passing among the series of heating tubes.
For this purpose the gases are admitted to the series of tubes in the vicinity of
the front poition of the boiler only, or in other words at the end which is farthest
removed from the chimney, the flow of such gases being at the same time spread
out over as extensive an area as possible in the upward direction.
In this manner the total length and height (or depth) of the series of tubes are
traversed by the gases before they escape into the chimney.
Figures 4, 5, 6 and 7 of the accompanying drawings represent one form in which
this invention may be carried out. In order to enable the invention to be better
understood the boiler is supposed to be identical with that already described with
the exception of the series of heating tubes, the arrangement of which is modified
In accordance with the improvements which constitute the present invention.
Like letters refer to like parts in all the drawings.
Figure 4 is a longitudinal section and Figure 5 a transverse section taken in that
portion of the length of the tubes which is desiguated by the letter L in Figure 4.
Figure 6 is a cross section of the portion or length of the tubes designated by the
letter M in Figure 4 and Figure 7 is a longitudinal oblique section on line X Y
Figures 5 and 6.
The length or portion of the tubes marked L (Figures 4 and 7) which is nearest
to the heating chamber, is open throughout the maximum area available in the
direction of the height of the boiler; that is to say, the curve of the tubes, as
indicated in Figure 5 is such that the gases may pass among the side tubes
between a and b. Throughout the length of tubes marked M Figures 4 and 7
which length occupies the remaining part of the furnace the hot gases are incapable
of entering the series of tubes which are so arranged as to form as tight au arch as
possible.
For this purpose as shewn in Figures 6 and 7 the two inner rows of tubes on each
side are brought into the same place so as to form an arch or wall, they will then
be contiguous if the distance of the two traverse rows be equal, or nearly so to
the external diameter of the tubes, the interstices, if any, are preferably caulked
with asbestos or other fireproof material, while widor spaces at dande which may

page_text: exist between them in the viciuity of the upper and lower reservoirs, are filled up
with cement, bricks of a particular shape, asbestos or any other suitable material
capable of preventing the flame and hot gases from entering in appreciable
quantities.
The arrows in Figures 4 and 5 indicate the course which the hot gases are likely
to take.
It will be understood that as the sectional area of the currents of gases through
the series of tubes is proportional to the length L and to the height ab of the
admission sections, the said length L may be so much the smaller as the height of
the boiler is greater, and furthermore that owing to the arrangement of the tubes,
such height may be increased without fear lest the upper portion of the tubes be
not fully taken advantage of, in the process of steam-production.
The portion of the tubes occupying the length N situated between the main
bridge D and the inverted bidge F (Figure 4) has for its object to increase the
heating surface. It is not absolutely necessary however and may be dispensed with
of preferred this portion however was indispensable in the old type of steam
generators where it served for extinguishing the flames which entered the tubes
ncar the main bridge D.
The following modifications may be made in the generator hereinbefore described
without departing from this invention.
In order to ensure that the gases be admitted to the series of tubes at the
greatest possible distance from their point of issue therefrom, and in order to avoid
the flames from being extinguished immediately upon entering, a portion of the
tubes may be dispensed with in the length L nearest to the front. There might be
arranged in that portion a species of fire-box or flue, in which case there need only
be retained, along the front, one or two transverse series of tubes for the purpose of
preventing that part of the envelope or casing from being unduly heated.
The inner screen or arch of the series of tubes in the length M is formed by
bringing together the two innermost longitudinal 10ws of tubes upon the same plane.
In that case it may happen that the heating surface exposed to the direct action of
the flame is insufficient. It may however be materially increased by combining
upon the same surface the third and fourth rows of tubes instead of the first and
second. In this case the first and second longitudinal rows would be subjected to
the direct action of the fire throughout and assist under certain circumstances the
full combustion of the hot gases before they enter the tubes in which they are
speedily extinguished.
The chimney is supposed to be situated entirely outside the series or bundles of
tubes. Or the chimney may be arranged especially for the purpose of reducing the
length of the apparatus above the sciies or bundles of tubes, which are farthest
from the frout, the external longitudinal rows of tubes being in that case open at
the top so as to afford a passage for the gases; this being the arrangement described
in the prior French Patent herein before referred to, or the chimney may be
arranged partly above the tubes farthest from the front and partly above a smoke-
box forming an extension of the series of tubes.
The improved generators as described consist of an upper reservoir and two lower
reservoirs connected by two equal and symmetrical series of tubes. Other
arrangements however may be adopted if required.
The number of main return tubes of which there are three in the present
instance, may be more or less as may be required, the single tube for example
which is shewn situated in the rear in the vicinity of the chimney being dispensed
with.
Having now particularly described and ascertained the nature of our inveu-
tion and in what manner the same is to be performed we declare that what we
claim is―
1. In multitubular steam generators of the type hereinbefore described in which
the hot gases pass off into the chimney situated at the end opposite to the boiler

page_text: front, the improved anlangement of heating tubes so that the said hot gases can
only pass among them in the vicinity of the said boiler front and throughout the
length occupied by the gates substantially as herein before described
2 The improved multitubular steam generator constructed substantially as and
for the purposes herembefore described and illustrated in the accompanying 5
drawings.
Dated this 22nd day of December 1894.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, Agents.