Improvements in Water Tube Steam Boilers.
Year: 1899

page_text: Date of Application, 28th Mar., 1899
Complete Specification Left, 20th Dec., 1899-Accepted, 28th Mar.,
1900
Improvements in Water Tube Steam Boilers.
I, JOHN EDWARD THORNYCROFT, of Homefield, Chiswick, in the County of
Middlesex, Engineer do hereby declare the nature of this invention to be as
follows:-
This invention has reference to a construction of steam boiler of the kind
wherein an upper cylindrical steam and water vessel (hereinafter called the
steam drum) is connected to a lower water pipe or vessel (hereinafter called the
lower water vessel) by a series of tubular steam generating elements each of
which comprises two vertical or approximately vertical and adjacent pipes or
headers (hereinafter called headers) that are connected together by a number of
pairs of straight water tubes which are located above the fire grate and are
arranged at an angle to one another, one of the two headers of each element
being connected to the lower water vessel and to the lower end of each of the
several pairs of water tubes belonging to the element, and the other header being
connected to the steam drum and to the upper end of each of the several pairs
of water tubes, the other ends of each pair of water tubes being connected together
in any suitable way, the arrangement being such that when the boiler is in use,
water will flow from the lower water vessel into the lower header of each element
and will then flow simultaneously through all the pairs of inclined water tubes
(which may be said to be in parallel to one another) of each element into the
upper header of the element and thence into the steam drum where the steam
generated by the passage of the water through the tubes will become separated
from the water.
The upper headers may deliver water and steam into the steam drum above
the water level therein, the water space of the steam drum being then con-
nected to the lower water vessel by one or more downtake tubes. By con-
structing steam generating elements in the manner herein before described, a
large heating surface is provided whilst at the same time the length of tube
through which water flows on its way from the lower water vessel to the steam
drum is comparatively short, thereby ensuring that all the tubes shall be filled
with water and thus obviating the liability that obtains in practice when a large
number of tubes are connected in series to form a long water tube, of the upper
tubes being unduly heated and fractured owing to their containing steam only,
and of steam being discharged through the lower end of the tube whereby
efficient circulation is prevented.
In one construction of such a boiler according to this invention, the steam
drum, which is made of comparatively large capacity, is arranged longitudinally
at the front of the boiler and above a longitudinally arranged lower water
vessel which is or may be made of comparatively small diameter and in the
form of a pipe that is connected at one or both ends to the water space of the
steam drum by one or two downtake tubes. The pair of lower and upper headers
of each element are arranged vertically side by side at the front of the boiler

page_text: and are respectively connected in any suitable manner to the lower and upper
forward ends of each pair of inclined tubes which are made straight and of
comparatively large diameter, the rear ends of each pair of tubes being con-
nected together by a junction box in which they are suitably fixed and which
is not fixed in position so that each pair of water tubes is free to expand and con-
tract. The outer sides of the headers and junction boxes are provided with
removable covers or closures so that access can be readily gained to each tube
for inspecting, cleaning or removing it. The lower header of each element is
or may be connected to the top of the lower water vessel by a detachable joint,
and the upper header of each element be similarly connected to the lower side
of the steam drum, so that the complete element can be readily removed or re-
placed when desired. The upper headers may be each provided with an upward
extension through which water and steam can be delivered above the water level
in the steam drum.
The connected elements are suitably supported above a fire box and grate and
within a casing of any known or suitable construction provided with suitable
doors for gaining access to the water tubes and fire box.
Two or more steam generators of the kind herein before described may be
arranged back to back in a common casing as in known constructions of boilers.
A feed water heater for use with the boiler herein before described may be
arranged above the steam generating elements as in existing types of boilers.
The feed water regulating apparatus may be arranged external to or within the
steam drum but preferably the latter.
Improvements in Water Tube Steam Boilers.
I, JOHN EDWARD THORNYCROFT, of Homefield, Chiswick, in the County of
Middlesex, Engineer, do hereby declare the nature of this invention and in whal
manner the same is to be performed to be particularly described and ascertained
in and by the following statement:―
This invention has reference to a construction of steam boiler of the kind
wherein an upper cylindrical steam and water vessel (hereinafter called the steam
drum) is connected to a lower water pipe or vessel (hereinafter called the lower
water vessel) by a series of tubular steam generating clements each of which
comprises two vertical or approximately vertical and adjacent pipes or headers
(hereinafter called headers) connected together by pairs of straight water tubes
which are located above the fire grate with the tubes of each pair arranged at
an angle to one another, one of the two headers of each element being connected
to the lower water vessel and to the lower end of each of the several pairs of
water tubes belonging to the element, and the other header being connected to the
steam drum and to the upper end of each of the several pairs of water tubes, the other
ends of each pair of water tubes being connected together in any suitable way,
the arrangement being such that when the boiler is in use, water will flow from
the lower water vessel into the lower header of each element and will then flow
simultaneously through all the pairs of inclined water tubes, (which may be said
to be in parallel to one another) of each element into the upper header of the

page_text: element and thence into the steam drum where the steam generated by the pass-
age of the water through the tubes will become separated from the water.
My improved construction is illustrated in the accompanying drawings,
whereof Fig. 1 shows my improved boiler partly in cross section on the line xx
of Fig. 2 and partly in end elevation, and Fig. 2 shows it partly in longitudinal
section on the line yy of Fig. 1 and partly in front elevation.
The steam drum 1, which is made of comparatively large capacity, is arranged
longitudinally at the front of the boiler and above a longitudinally arranged
lower water vessel 2 which is of comparatively small diameter and is connected
to the water space of the steam drum by external downtake tubes 3 of which
there are three in the example shown. 4 and 5 are respectively the lower and
upper headers of each steam generating element, these headers being arranged
vertically side by side at the front of the boiler. 6 and 7 are inclined water
tubes arranged in pairs, the tubes 6 and 7 in each pair being respectively con-
nected, in any suitable way, at their front ends to the corresponding pair of
headers 4 and 5 so that each tube 6 inclines backward and upward and each
tube 7 inclines forward and upward. Each pair of tubes 6 and 7, which are made
straight and of comparatively large diameter, are connected together at their
rear ends by a junction box 8 in which they are suitably fixed but which is not
fixed in position, so that each vee-shaped pair of water tubes thus obtained is
free to expand and contract. By the arrangement described, water will flow
freely from each header 4 in an upward and backward direction through each
of the pipes 6 connected thereto and upward and forward through each of the
corresponding pipes 7 to the corresponding header 5.
The headers 4 and 5 of each steam generating element are rigidly connected
together by bolts 4" passing through lugs or projecting parts 4b on the headers
so that the combined headers and water tubes form practically one piece that
can be readily fixed in place and removed without throwing any strain on the
water tube joints. The outer i.e. front sides of the headers 4 and 5 are provided
with removable covers or closures 9 so that access can be readily gained to each
tube for inspecting, cleaning or removing it. The outer, i.c. rear side of each
junction box 8 may also be provided with a removable cover or closure for a
like purpose. The lower header 4 of each element is connected to the top of the
lower water vessel 2 in a readily detachable manner, and the upper header 5
of each element is similarly connected to the lower side of the steam drum 1,
so that the complete element comprising the connected headers 4, 5, tubes 6
and 7 and junction box 8, can be readily removed or replaced when desired.
In the example shown, the adjacent lower ends of the lower headers 4 are
clamped to the water vessel 2 by clamping plates 11 and bolts and nuts 12,
the adjacent upper ends of the upper headers 5 being similarly connected to
the lower side of the steam drum 1.
The upper headers 5 may be each provided with an upward extension 5*
through which water and steam can be delivered above the water level in the
steam drum 1. 13 is a baffle plate below which the upward extensions 5*
terminate, and 14 is the steam main.
The connected elements are supported at the front by the lower water vessel 2,
and at the back by a rear wall 15 above a fire box 16 and grate 17 and within
a casing 18 that may be of any known or suitable construction and is provided
with suitable doors 19 and 20, for gaining access respectively to the water
tubes 7 and fire box 16. In the example shown, there are two fire-grates 17
extending from front to rear of the boiler below the water tubes 6-7.
In order to obtain in a boiler constructed as hereinbefore described, efficient
combustion and good evaporative results with inferior fuel, and also to obtain
as nearly uniform distribution of the flame and hot gases among the water tubes
as possible, each fire grate 17 is covered, as shown in Figs. 3 and 4, with a fire
box of refractory brickwork having its roof made in two parts 16ª, 16b arranged

page_text: at different levels with a narrow exit opening 16° between their adjacent ends.
The two parts may be variously arranged. In the example shown, the rear
part 16 is the lowest and the front part 16b is inclined upward and backward,
but this arrangement may be varied. With the arrangement described, when
the boiler is in action, the fire brick walls and roof of cach fire box are raised
to a high temperature and assist in mixing the gases and vapours resulting
from the more or less complete combustion of the fuel with tue air admitted to
the fire box and in heating the mixture, with the result that practically complete
combustion of the gaseous products is obtained and formation of soot avoided.
Also the flame and hot gases on escaping from each fire box through the exit
opening 16 are directed backward in consequence of their inertia, and are,
to a large extent, caused to flow upward amongst and between the rear portions
of the water tubes which are nearer together and offer greater resistance to the
flow of the hot gases than the front portions of the tubes which, as will be seen
from Fig. 4; will offer much less resistance to the flow of the hot gases amongst
them owing to many of the lower tubes 6 and upper tubes 7 not being crossed
by adjacent tubes. To ensure that the front portions of the lower water tubes
shall be effectually heated and perform their share of the work to be done, the
front portion 16 of the roof is formed with a few exit holes 16d through which
flame and hot gases can escape and come in contact with such portions of tube.
To assist in the effective distribution of the flame and hot gases amongst the
water tubes, the chimney or uptake 16 may, as shown in Fig. 4, be arranged
above the rear portions of the water iubes 6. 7. Holes, which are normally
closed, are or may be provided in the side walls of the boiler casing to facilitate
the removal of dust that may accumulate above the front portion 10 of the
fire box roof.
Two or more steam generators of the kind herein before described may be
arranged back to back in a common casing, as in known constructions of boilers.
A feed water heater for use with the boiler hereinbefore described, may, as
shown at 22 (Fig. 2), be arranged above the steam generating elements, as in
existing types of boilers. This feed water heater may be of any suitable con-
struction and in the example shown consists of a number of sets of inclined
tubes 22 that are connected at their ends to junction boxes 23 and are provided
with an inlet 24 at the top and an outlet 25 at the bottom. The feed water
regulating apparatus may be arranged external to or within the steam drum
but preferably the latter.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is
Water tube steam boilers of the kind referred to constructed as illustrated and
described with reference respectively to Figs. 1 and 2, and Figs. 3 and 4 of
the accompanying drawings.