Year: 1896

page_text: Date of Application, 7th Aug., 1896-Accepted, 16th Jan., 1897
I, JOAQUIM RIBEIRO DA COSTA of 97 Boulevard Longchamp, Marseilles,
France, Naval 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:-
This invention relates to a new or improved return tube steam boiler or generator
of the multi-tubular or tubulous type.
This new steam boiler consists essentially of a number of compound tubes
arranged with their longitudinal axes parallel or approximately parallel to one.
another and serving to connect a front water chamber or front header and a front
smoke box with a rear water chamber or rear header and a rear combustion.
chamber. These compound tubes are arranged at a suitable inclination to the
horizontal, that is to say with a certain amount of rise from the rear header to the
front header. Each compound tube is composed of three or four, preferably four,
concentric tubes arranged one within the other, leaving a suitable space of annular.
form between one tube and the next outer or inner tube to allow of the passage
therethrough of water or fire gases as the case may be. In the case where the
compound water tube is composed of four concentric tubes, the arrangement is as
follows: The fire gases rising from the furnace below pass between the outermost
tubes of the compound water tubes up to the topmost row of compound tubes where
the said gases are deflected by the upper portion of the boiler casing towards the
rear header over which they pass into the combustion chamber arranged at the.
rear of the boiler and are then deflected by the rear portion of the boiler casing
back towards the compound tubes which project through the rear header in such a
manner that the fire gases pass through the innermost or central tube, and also.
through the annular space existing between the outside surface of the next outer
concentric tube and the inside surface of the tube surrounding this last mentioned
tube. The fire gases are thus led through the rear header, along the compound
tubes and through the front header into the smoke box arranged at the forward
part of the boiler, whence they pass off to the uptake and thence to the chimney.
The circulation of the water is as follows:-The feed water entering the feed
chamber at the lower part of the rear header flows simultaneously through the'
annular space comprised between the inner surface of the outermost tube of the
compound water tube and the outside surface of the next inner concentric tube, and
also through the annular space comprised between the outside surface of the
innermost or central fire tube and the inside surface of the next outer concentric
tube. The arrangement is therefore such that the boiler water flows along in each
compound water tube in the form of two concentric and parallel annular sheets or
streams of water, heated on their inside and outside respectively by an intervening
annulus of fire gases, the inner annular stream of water heated on its inside by a core
of fire gas, whilst the outer annulus of water is heated on its outside by the
enveloping fire gases rising directly from the furnace fire. These two annular.
streams of water flow along in the same direction as the fire gases in the compound.
tube, and pass into the front header where the streams of water delivered by all the
compound water tubes rise and pass up into a steam and water drum, whence the
steam separating from the water is led to the engine, whilst the water flows along.
the drum through a down tube into the feed chamber and thence back again into.
the lower part of the rear header.

page_text: The flow of the water from the rear header into the compound water tubes, and
from these into the front header, and also the entrance of the fire gases from the
combustion chamber into the compound tubes, and from these into the smoke box,
is effected by means of special connecting and jointing devices or attachments,
hereinafter called "connectors." These connectors are preferably of the kind
forming the subject of an application for Letters Patent of even date herewith,
and numbered 17489.
The arrangement of the apparatus described above constitutes my new steam
boiler, or.steam generating element in its simplest form, and it is to be understood
that any number, preferably three, of such steam generating elements may be
combined together to form a self contained steam boiler.
In order to enable my invention to be more clearly understood, I shall now
proceed to describe a steam boiler constructed according to this invention con-
sisting of three or four of my new steam generating elements combined together
and delivering into a common steam and water drum; with reference to the
accompanying drawings:-
Figure 1 is a view in side elevation partly in vertical longitudinal section;
Figure 2 is an end elevation, and Figure 3 is a plan partly in section of my new
steam boiler.
Figure 4 is a central longitudinal section taken through à compound tube of four.
concentric tubes, together with the connectors and part of the headers at each end
of the said compound tube.
Figure 5. relates to the connector alone shewing a modification of my said
invention where three tubes are employed.
The same reference letters indicate the same parts in all the figures.
In these figures,-A' A' A' are the three front water headers, and A A A are
the three rear water headers. These headers may be made of wrought iron, cast.
iron, cast steel, or steel plate, or other suitable material; they are connected.
together as shown in Figure 1, by a number of parallel sets or series of compound
tubes, each compound tube consisting of four concentric tubes e, x, y, z; viz. an.
innermost tube v, and outermost tube z and two intermediate tubes x, y, one within
the other. The outermost or largest tubes z are screwed with their ends into the
corresponding walls of the respective headers, and are further secured by means of.
lock nuts 2 in the usual manner. For the purpose of facilitating the insertion and
removal of these tubes, they may at one end stop short of the hender wall and be
screwed into a short length of tube or sleeve which itself. is screwed on to a nipple
screwed into the header wall, as shown in Figures 1 and 4. In this case, the joint
is also secured by means of lock nuts 2.
The two intermediate tubes x and y are fixed and jointed at each of their ends
by means of a special connecting piece H common to both tubes, and herein before
referred to as the connector. forming the subject of an application by me for Letters
Patent of even date herewith. These connectors may be of cast iron, cast steel or
other suitable material. The ends of the tubes x, y, are formed as shown in
the figures viz. they are swelled out to a larger diameter and their end surfaces
are bevelled or cut at an angle, and in the centre of these bevelled or inclined
surfaces there are formed grooves a al (shown more clearly in Figure 4). These-
grooves may be of any desired form in cross section so long as the bevels or
inclinations of the sides of the grooves are always opposite to the direction of the
pressure acting upon the joint surface. Where the bevelled ends of the tubes x, y
meet the connector, there are cut in the respective meeting faces of the connector H
annular grooves bb (shown more clearly in. Figure 4) of approximately the same
diameters as the diameters of the respective tubes. These grooves b & may also be
of any desired form in cross section so long as the bevels or inclinations of the
sides of the grooves are always opposite the direction of the pressure acting upon
the joint surface.
The method of making a tight joint is as follows:-A ring of soft copper g g of
suitable dimensions and of square form in cross section having been placed in each

page_text: groove band the tubes a y inserted in position inside the tube a, and so as to bear
slightly into the grooves b b¹ of the connectors H which are also placed in position
against the headers at both ends of the two tubes, an iron rod screw-threaded to
receive a nut at each end is passed through the inner tube x. By screwing up the
said nuts the connectors H'H' are caused to exert a powerful longitudinal com-
pressive force upon the tubes a y with the result that the soft copper rings g 9' are
deformed and forced to fill up the grooves a band a¹ b' in such a manner as to
produce a tight joint at those places. The arrangement is such that when the
copper rings have been sufficiently compressed the faces of the flanges i of the
connectors will be in steam and water tight contact with the corresponding surfacesj
of the headers A A. This last mentioned joint may be facilitated by the use of
soft copper wire or other suitable packing between the two contact surfaces.
When sufficient contact has been made at the three places at each end of the
compound tube the nuts h of the screw bolts 5 that serve to keep the connectors in
position, are screwed up tight, and then the iron rod which bas served to help make
the joints is removed. The said screw bolts 5 are preferably prolonged inwards
through the headers and screwed into the opposite header wall in such a manner as
to also act as stay bolts to the walls of the header.
The innermost tube t is then inserted in position, it is kept in place at its ends by
means of flanged rings ff which bear with their flanges against the outer en is of
the connectors H H respectively, and which have annular projections fitting inside
the ends of the tube v. A good joint is ensured at these places by means of two
grooves k k of similar cross section to the grooves a a' and cut respectively in the
swelled ends of the tube and in the joint face of the rings into which
grooves kk rings of soft copper are compressed by the pressure exerted by serewing
up nuts which bear against the rings and take into screw threads formed on
the outside of the outer, ends of the connectors HH'.
The steam and water drum K which is arranged transversely of the boiler elements
and communicates at its lower part by means of necks m m m directly with the
upper parts of the front headers A' A'A' is of T shape, or has a rear-ward central
extension t communicating at its rear end by means of a single down tube u with
the comnion feed water chamber u' of the boiler elements. Communication between
the upper parts of the rear headers A A A and the steam and water drum is
established by means of connecting pipes 6 preferably of copper opening into a
common ueck m' delivering into the lower part of the steam and water drum
extension. This connection has for object to prevent any accumulation of steam
in the upper parts of the rear headers A.
The circulation of the steam and water in this boiler is as follows:-The feed
water entering by the common feed pipe 7 which passes below the grate centrally
through the ashpit, passes by the branch feed pipes 8 into the common feed
chamber w, and from the latter through branch connecting pipes into the lower
part of each rear header A. The water rises into these headers and passes partly
direct into the several annular water spaces comprised between the tubes y and z
and partly through suitable openings O provided in the connectors H into the
annular water spaces comprised between the tubes v and x. The water becoming
highly heated in its passage through the said water spaces of the compound tubes,
flows out of the outer water space between the tubes y and z, directly into the front
headers A¹ A' A', and out of the inner water spaces between the tubes v and a,
through suitable openings O' in the connectors H' also into the front headers A' A'A
The compound tubes zy v have a certain amount of upward inclination from the
rear headers to the front headers. The water delivered into the front headers A
from all the compound tubes rises up in the front headers and through the
necks m m m into steam and water drum K and its extension t. The freeing of the
steam from its water is partly effected in the drum K by means of an inclined plate p
the lower portion of which is perforated, and in the extension by means of
perforated partitions 9, 10, 11. These latter partitions also serve to prevent
"washing" of the water contained in the extension t in the case of a marine boiler

page_text: on board ship in heavy weather. The combined steam of the drum K and of the
extension is still further freed from water by passing in succession through a
curved perforated partition 9 and straight perforated plate rinto the steam space S
whence the steam passes-direct to the engine.
The water now flows from the drum K through the extension t and down the
down tube u into the common feed chamber u' where it meets the incoming feed
water and with it passes into the rear headers A as above described.
Any impurities that may be contained in the water are deposited in the feed
chamber and in the lower part of the rear headers A, whence the deposits can
be easily removed when desired. The circulation of the steam and water which is
very powerful is indicated in the drawings by feathered arrows.
The course of the fire gases, indicated in the drawings by featherless arrows, is
as follows:-The fire gases rising from the burning fuel on the grate 12 pass up
between the whole of the tubes to the top of the rear headers A where the gases
are deflected by the boiler casing down into the combustion chamber, P, at the
rear of the headers A whence the gases pass in part directly into the innermost or
central tubes and in part through suitable passages B D provided in the
connectors H into the annular spaces comprised between the tubes a and y. The
upper passages B are the main passages the lower passages D being provided
merely to obviate the deposit of soot and ashes at those points in the connectors.
The fire gases then sweep along in the fire spaces through the rear headers A
along the whole length of the compound tubes and through the front headers A',
and finally out through suitable upper passages B' formed in the connectors H¹
into the smoke box Pi and thence into the uptake and chimney,
The boiler elements are enclosed in a suitable boiler casing P. The lowermost
row or rows of compound tubes which are exposed to the greatest heat of the
furnace, may if necessary consist merely of the three tubes ay thus leaving out
the central fire tubes ; or they may even consist of plain water tubes only such
as the outer water tubes without any inner tubes. Figure 5 shows a form
of connector suitable for use with compound tubes according to my invention.
consisting of three tubes only vis. :-, y, 2.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. A multitubular steam boiler of the return tube type, comprising a front and rear
water chamber connected together by compound tubes each compound tube
consisting of four concentric tubes two of which are used as fire tubes and two as
water tubes, substantially as and for the purposes described.
2. A multitubular steam boiler of the return tube type comprising a front and
rear water chamber connected together by compound tubes each tube consisting of
three concentric tubes, the intermediate tube being preferably used for the heated
gas whilst the outer and central tubes are used as water tubes substantially as and
for the purposes described.
3. A multitubular steam boiler of the return tube type comprising a front and
rear water chamber connected together by compound tubes the upper compound
tubes consisting of four concentric tubes as described the lower compound tubes
consisting of three concentric tubes, substantially as and for the purposes described.
4. In a multitubular steam boiler of the return tube type the means of connecting,
fixing and jointing the three inner concentric tubes to the water headers so as to
afford passage to the fire gases substantially as described and shown in the
accompanying drawings.
5. In a multitubular steam boiler of the return tube type the use of special
connecting pieces or connectors such as HH' for the purpose of fixing and jointing
the three inner concentric tubes of the compound tubes to the water headers, and
of affording passage to the fire gases from the combustion chamber to the smoke
box, substantially as described and illustrated by the accompanying drawings.

page_text: 6. In a multitubular steam boiler of the return tube type the use of screw bolts
for attaching the connectors to the beaders, said bolts serving at the same time as
stay bolts to stay and connect together the walls or sides of the headers, sub-
stantially as described and illustrated by the accompanying drawings.
7. In a multitubular steam boiler of the return tube type the combination of
front and rear water headers connected together by compound tubes of the kind
specified with a steam and water drum, the front portion of which is in direct
communication by a neck or necks of comparatively large diameter with the upper
part of the front water header, whilst the rear portion or extension of the said
drum is connected by a pipe or pipes of relatively small diameter with the upper
part of the rear water header, substantially as and for the purpose described and
as illustrated by the accompanying drawings.
8. In a multitubular steam boiler of the return tube type the combination of
front and rear water headers connected together by compound tubes as described,
a T shaped steam and water drum communicating at its front end by a neck of
large diameter with the upper part of the front water header and by a relatively
narrow pipe with the upper end of the rear water header and a down tube con-
necting the rear end or limb of the aforesaid drum with the feed chamber of the
boiler, substantially as described and illustrated by the accompanying drawings.
9. A multitubular steam boiler consisting of two, three or more steam generators
of the kind specified in the preceding claims in which the several front headers
deliver through their several wide necks into a common transversely arranged
steam and water drum having a central rear and extension whence the water flows
through a common down tube through branch tubes into a common feed chamber
substantially as described and illustrated by the accompanying drawings.
10. The general arrangement, construction and combination of parts forming a
multitubular steam generator or boiler, substantially as described and illustrated
by the accompanying drawings.
J. C. MEWBURN & ELLIS,
55 and 56 Chancery Lane, London, Chartered Patent Agents.