Improvements in Steam Boilers.
Year: 1896

page_text: Date of Application, 4th Apr., 1896-Accepted, 9th May, 1896
Improvements in Steam Boilers.
I, JOSEPH JOHN BUTCHER, of Thompsonville, in the State of Connecticut, in
the United States of America, Mechanical 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 :-
My invention relates to a boiler consisting of a cylindrical drum, front and back
headers, and ef a number of curved water tubes uniting the said headers together,
and of other details, as is described below in reference to the accompanying
drawings.
Fig. 1 is a longitudinal section of my boiler.
Fig. 2 is a half transverse section through the brickwork setting, showing a front
view of the boiler within it.
Fig. 3 is a half view of the boiler from the back with the brickwork in section.
Fig. 4 is a plan of the boiler with an outline of the setting.
A is a horizontal drum, communicating by means of the downtake tube B, with
the back header C, and the numerous curved water tubes E. These tubes E
communicate at their front ends with the front header F, which opens into the
front of the drum A.
I usually bend all these tubes to the same radius, and in the drawing they are
thus shown and are not concentric. The object of this arrangement is so that they
may be all cleaned with an ordinary tube scraper, the rod of which is bent to the
same curve as the tubes are bent to. Where there is not head room to get this
scraper and rod entered from the front it may be formed of short pieces and bolted
or otherwise suitably fastened together as each piece is successively forced into the
tube. The centre lines of the tubes alone are shown in Fig. 1, together with the
top line of the top tube and the bottom line of the bottom tube, and these tubes are
expanded into the tube plates G and H in the usual way.
On the outside plates of the headers I and J are hand holes, closed by the tube
caps (not shown) in the usual manner, through which the tubes may be entered
before expanding or withdrawn for renewal, and which also enable them to be
cleaned internally by scraper as described.
Each of the headers C & F is built on a curve, so that the tube plate is approxi-
mately at right angles to each tube as it enters the plate. If the centre line of the
top and bottom tubes be bisected between the two tube plates, and these points of
bisection be joined by a straight line Q, and this line extended upwards, then the
centre from which the curve of each tube is described will be upon this line, and
the radius from any tube will be of the same length as those from each of the other
tubes. Thus the tubes converge as they enter the tube plates. To find the centres
of curvature of the headers I continue these curves (that is the curves of the centre
lines of the tubes) to the centre lines of the headers, and then produce them from
these points as straight lines, tangential to the curves of the tubes as produced,
beyond the headers until the tangents meet. The said tangents will not all meet
at the same point, but for practical purposes I find that if the tangents from the
centre lines of tubes about one fourth from the top and one fourth from the
bottom (K and L) be produced, and the points where they meet be used as centres
from which the curves of the header plates are struck, all purposes required are
served. Then the centre lines passing through the hand holes and the tube holes
will be made radial to these centres, and the stays between the holes will also be

page_text: set radial to these centres, and they will then be at right angles to both the inside
and outside plates of the headers.
As the front and back plates of the headers have to be flanged on a former, this
former may be shaped to the required curve as shown in Fig. 1, so that the plates
may be both flanged and curved in a single operation without additional expense
being incurred.
M is the furnace, and the hot products of combustion pass upwards among the
tubes and over the top of the baffle N, and then downwards among the tubes and
under the baffle O, and then again upwards among the tubes and round each side of
the downtake B over the baffles P, to the damper opening R.
As most of the steam is developed over the furnace in the first run of the gas it
is much more essential to have the tubes steeply inclined upwards in this region
than it is in the vacinity of the back header. Very little steam is formed behind
the baffle O, and therefore, as the difference between the specific gravity of the
steam and water within the tubes at this part of the boiler and that of the water in
the back header is but slight, there is but little value in any rise of tube in this
region. I therefore prefer to so arrange that the centres of curvature of my tubes
are somewhat forward of the back header, so that the bottom tubes may incline
downwards as they leave the back header and rise to about the original level again
when they reach the baffle O. Thus in effect the bottom tubes are level from the
back header to the baffle O, while the top tubes have only a slight upcast in this
region.
Between the baffles O and N the upward incline of the tubes increases con-
siderably. As steam is throughout this region accumulating within the tubes, and
the specific gravity of the combined steam and water decreasing, "an upward
inclination is becoming of more and more value for circulating purposes.
Between
the baffle N and the front header the greater proportion of the steam is made, and
this is especially the case with the two bottom rows of tubes which are exposed to
the radiant energy of the furnace, as well as to the very hottest of the flame.
Here therefore make the tubes very steeply inclined, because the difference
between the specific gravity of the water and the entrained steam within the tubes
and of the solid water in the back header has reached its maximum. It will be
observed from Fig. 1 that the actual hydrostatic head within the lowermost tubes,
measured from the level at which they leave the baffle N to that at which they
discharge themselves into the front header F, is greater than in the upper tubes
between corresponding points. This feature is very desirable, because, as more
steam is formed in the lower tubes, they should have the quicker circulation.
Within the tubes the steam bubbles are entrained with the water-that is, they
have little tendency to circulate through it, but are entangled with it, and both
move together very much as one mass. When this mixed product of steam and
water emerges into the front header however the steam bubbles rise through the
water immediately to the surface. This happens because the front header being
large compared with the size of each bubble of steam the latter is surrounded by
water and the water flowing underneath it displaces it upwards at a much greater
velocity than that of the general flow of the water. Thus the amount of steam
contained in the water of the front header at any moment is proportionally much
less than that contained in the tubes over the furnace. For this reason the front
header is of but little value for circulating purposes, as the water and steam within
it are together not very much lighter than is the solid water in the back header.
Thus Iso arrange that the lower tubes rise almost to the level of the drum before
they enter the front header, while the upper tubes enter the header at a level not
far from that of the water line. With this object, as is shown in Fig. 1, my front
header is built outwards from the centre of the drum and inclined downward at a
suitable angle, while the back header is built considerably below the drum and is
inclined backward at a slight angle behind the vertical.
A convenient method of uniting the front header to the drum is shown in Figs. 1,
2 and 4. The outer and inner plates of the header are built to a curve as shown,

page_text: and are flanged to meet the side plates, which latter are formed to the same curve.
all being rivetted together. Thus a bend is formed sufficient to bring the upper
portion of the header into a horizontal position, and this horizontal portion is so
formed and flanged as to fit like an open mouth upon the conical drum head S.
This drum head may be bent in two separate portions on a former, one forming the
upper and the other the lower section of the cone, and these two separate pieces
welded together where they meet at the sides of the header, so as to form the
complete conical head with the required mouth opening of suitable shape to receive
the header. This method avoids the necessity for cutting away so much plate in
forming the required mouth as would have to be removed if a complete cone were
in the first instance made. I prefer to make all these plates of steel or good
wrought iron, and flange and rivet them together. The staying between the tube
plates and hand bole plates is of a similar character to that usual for flat surfaces,
and the same may be said of the horizontal portions of these plates. The mouth
where the header is flanged onto the conical drum head is held together by some-
what stronger stays in proportion to the pressure which has to be resisted.
The cylindrical downtake B is flanged onto the bottom of the drum, the opening
in which is strengthened by the reinforcement ring T. This cylinder is flanged in
at the bottom to meet the conical portion of the back header as shown. This
conical portion may be conveniently formed upon the back and front plates of the
header, and strongly stayed together where it arises from the header tube and hand
hole plates, which latter are stayed together in a similar manner to that previously
described in regard to the front header.
As there is a tendency in curved tubes to straighten when subjected to internal
pressure, and as the structure of drum and headers in my boiler is very rigid and
will not yield to this tendency without injury, I prefer to bind the two headers
together at their bottom ends by means of a pair of thick straight stay tubes U
and V. These tubes are made sufficiently strong to resist any tendency that may
occur to force the headers apart at their lower ends. The tubes are screwed at
each end and passed through the cast steel (or other suitable) eyes W and X,
which latter have suitable flanges, as shown, formed upon them and so shaped as to
fit upon the lower parts of the back and front headers, to which they are rivetted
or otherwise rigidly attached. The nuts Y and Z resist the thrust of the eyes.
Beyond these nuts the pipes AA and A B are coupled onto the ends of the stay
tubes. The hand hole caps A C and A D have suitably formed nozzles projecting
from them through the hand holes, and these nozzles are screwed so as to receive
both the nuts which draw the hand hole covers firmly down upon their seats so as
be steam tight and also to receive the unions or couplings at the inner ends of the
circulating pipes AA and A B. These pipes make the circulating water ways
complete from the back header through the stay tubes to the front header.
object of circulating water through these tubes is simply to keep them from getting
overheated, I protect them from the greater part of the heat by building offsets A E
of brickwork underneath them from header to header, leaving space enough between
each offset and the boiler tubes for inserting the steam jet for blowing the dust
off them.
As the
The baffles N and O are so sloped with regard to one another, and to the tube
plates H and G, as to form passages for the hot products of combustion, of such
character that the sectional openings among the tubes for the gases at each of the
six positions at which they enter and leave the tubes, A G, AH, AI, AJ, AK
and A L, are roughly proportional to the absolute temperatures of the gases in
these positions. The object of this arrangement is to ensure that the entire length
of each tube is, as far as is practicable, immersed in the actual stream of hot gases,
and that there are no portions about which eddies of comparatively stagnant gas
may form.
With this object in view the baffle N slopes rapidly towards the tube
plate F, so that the passage for the gases is very rapidly contracted throughout its
first upward run where the fall of gas temperature is greatest. In boilers where

page_text: this baffle is parallel with the tube plate a large portion of the tubes, especially
among the upper tubes in the vacinity of the header, is left untouched by the main
stream of the products of combustion, which clings to the baffle preparatory to
turning over its top edge. This portion of the tubes is only covered by almost
stagnant gas, which has very little heating effect, and thus the tube heating surface,
as a whole, is reduced in efficiency. In the second and downward run of the gases
in my boiler the baffles N and O also slope towards each other in the direction of
the flow of the gases, but the contraction of passage resulting is not so great as
that described for the first upward run of the gases, as in the second and downward
run the loss of heat is not so great as in the former case. As there is a slight loss
of heat to the drum between A H and AI I make the entry at A. I slightly
smaller than the exit at AH, about in proportion to the average difference of
absolute temperatures found to occur between these two positions. As between A J
and AK scarcely any loss of heat occurs after the brickwork and floor have been
once heated to the normal I usually make the entry at A K about the same size
as the exit at A J. The baffle O and the tube plate G also converge in the
direction of the flow, and about in proportion to the loss of heat consequent upon
the natural contraction of the gases in this region, and the aggregate apertures
between the tubes at A L is but little more than the full way damper opening at R,
plus an addition required for increased friction due to the sub-division of the gases
among the tubes. Thus there is a continual convergence of passage from A G
to AL which is most rapid at first where the fall of gas temperature is greatest,
but is continued with decreased rapidity until all the tubes have been passed.
At D the rod of a tube cleaner is shown projecting from a tube. It is bent to
the same curve as are all the tubes, and may consequently be used with equal
facility in any of them. A M is a joint in the rod to enable it to be taken to
pieces and inserted piece by piece in a case in which the head room is insufficient
to allow of a solid rod being introduced into the tube. To the inner end of this
rod any kind of suitable tube scraper may be attached and worked through the
tube in a similar manner to that in which a straight rod tube scraper is worked
through a straight tube.
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. In a water tube boiler, the combination of headers with a number of tubes,
placed both in horizontal and vertical rows, and all bent to a circular curve of the
same radius and secured into headers at each end of the tubes, the said headers
having hand holes one opposite each tube, substantially as herein described and
illustrated in the accompanying drawings.
2. In a water tube boiler, the combination of a number of tubes all bent to the
same radius and placed one above the other in the plane of their curvature with
curved headers, the tube plates of which are approximately at right angles to each
tube at the point where it enters the header, substantially as described and,
illustrated in the accompanying drawings.
3. In a water tube boiler, the combination of a number of tubes of the same
radius of curvature and placed one above the other in the plane of their curvature,
with headers forming the terminals of the said tubes and formed of stayed surfaces,
the stays occupying intermediate positions in the tube plates and hand hole plates
between the tubes, and also converging at angles intermediate to the angles of
convergence of centre lines passing through the corresponding tube holes and hand
holes next above and below them, substantially as described and illustrated in the
accompanying drawings.
4. In a water tube boiler, the combination of a number of tubes all bent to the
same radius ard placed one above the other in the plane of their curvature, with
front and back headers and baffles, the tubes being approximately horizontal in the

page_text: vacinity of the back header, while they increase in upward inclination as they come
forward to the front header, substantially as described herein and illustrated in the
accompanying drawings.
5. In a water tube boiler, the combination of a drum with a front header set to
slope downwards and forwards at an oblique angle with regard to the axis of the
drum, and built of stayed boiler plate with a knee bend formed in the said header
uniting it to a horizontal portion, also of stayed boiler plate, and formed to fit upon
the drum head and attached thereto substantially as hereinbefore described and
illustrated in the accompanying drawings.
6. In a water tube boiler the combination of a horizontal drum having a conical
head with front and back headers, the front headers projecting outward and down-
wards from the centre of the conical head, and with curved water tubes sloping
downwards and backwards from the front header, substantially as and for the
purpose described herein and as illustrated in the accompanying drawings.
7. In a water tube boiler the combination of a horizontal drum having a
cylindrical downtake with a back header of stayed boiler plate, having its upper
tube and hand hole plates in a conical form, and the side plates meeting them and
united with a downtake substantially as hereinbefore described and illustrated in
the accompanying drawings.
8. In a water tube boiler, the combination of a set of curved water tubes with a
back header either approximately vertical or sloping downwards and backwards at
a slight angle behind the vertical with a front header sloping downwards and
forwards at an angle of 50 degrees or thereabouts in front of the vertical the said
holders forming the terminals of the said water tubes substantially as herein before
described and illustrated in the accompanying drawings.
9. In a water tube boiler the combination of a set of curved water tubes with front
and back headers united by a drum at their upper ends and forming the terminals of
the said water tubes, with a pair of straight stay tubes holding the said headers firmly
together, and through which the water of the boiler may be allowed to circulate,
substantially as herein before described and illustrated in the accompanying
drawings.
10. In a water tube boiler the combination of a number of curved water tubes,
with front and back headers and baffles, the tubes being approximately horizontal
in the vacinity of the back header while they increase in upward inclination as they
come forward to the front header, substantially as hereinbefore described and
illustrated in the accompanying drawings.
11. In a water tube boiler, the combination of a front header with a baffle above
the bridge wall, the said header and baffle converging towards each other in the
direction of the flow of the gases, substantially as and for the purpose described
and as illustrated in the accompanying drawings.
12. In a water tube boiler, the combination of a baffle with a back header, the
said baffle and header converging towards each other in the direction of the flow
of the gases, substantially as and for the purpose hereinbefore described and as
illustrated in the accompanying drawings.
13. In a water tube boiler, the combination of baffles and walls, or of baffles,
walls and boiler plates, forming the boundaries between which the furnace gases
pass across and among the tubes, in such a manner that the cross sections of the
passages between the tubes diminish approximately as the absolute temperatures of
the furnace gases diminish, substantially as herein before described and illustrated
in the accompanying drawings.
n
11000
JOSEPH J. BUTCHER.