Improvements in Steam Boilers.
Year: 1891

page_text: Date of Application, 2nd Dec., 1891
Complete Specification Left, 2nd Sept., 1892-Accepted, 8th Oct., 1892
PROVISIONAL SPECIFICATION.
Improvements in Steam Boilers.
I, RICHARD HEBER RADFORD, of 15, Saint James' Row, Sheffield, in the
County of York, Mechanical Engineer, do hereby declare the nature of my inven-
tion, for IMPROVEMENTS IN STEAM BOILERS," to be as follows:-
The object of my invention is to improve the circulation of water in tubular steam
boilers more particularly in multitubular boilers of the locomotive or marine type.
During the forced draught trials which have recently been conducted on board
certain ships in Her Majesty's Navy, it was found that the steam boilers, although
of the most improved design and construction and apparently answering all require-
ments under ordinary conditions, developed when steaming under forced draught,
such signs of weakness as rendered them unsafe and incapable of continuing their
trials.
As these defects shewed themselves in the same locality, viz. in the back tube
plates and tubes, in all the boilers under trial, there has not been much difficulty in
arriving at the conclusion that the cause arose, primarily, from defective circulation.
Boilers of the type herein referred to are constructed with a combustion chamber,
or combustion chambers, which receive the accumulated heat of the furnace or
furnaces, as the case may be, from which chamber or chambers the heated gases &
flame on their passage through the tubes, must necessarily impinge upon the tube
plate and ends of the tubes, thereby causing a very rapid evaporation of the water
in contact with the heating surfaces in their locality and although under ordinary
conditions it is possible for sufficient circulation to be maintained; when under the
conditions of forced draught, the heat is so intensified and the rate of evaporation
is so increased, that the downward & return currents of water are unable to
approach the tube plate, through the contracted spaces between the tubes, in
sufficient quantity to prevent the tube plates and tube ends from becoming over-
heated and as a consequence distortion and leakage quickly follow.
Defects as herein described have in some cases been overcome by increasing
the water spaces between the tubes but this has only been effected by reducing
the number of tubes.
The object of my invention as already stated is to improve the circulation of
water. It is applicable to multitubular boilers whether for use under natural or
artificial draught. It can be carried into effect without sacrifice of heating surface
and can be applied to existing boilers without any material alteration in their
design or construction and as the principle of my invention is the same in all boilers
to which it can be applied, a description of it as applied to a cylindrical multitubular
marine boiler, with two furnaces and one combustion chamber common to both
furnaces will suffice.
In such a boiler I provide what may be called a dummy tube plate, this plate I
make of comparatively thin material and approximately of the same superficial
dimensions as the back or front tube plate, in it I provide holes corresponding to
those formed for the tubes and stays in the tube plates proper. This dummy plate
I place in position in front of the back tube plates so as to leave a sufficient space
for the ascending currents of steam & water but not sufficiently wide to allow of
the descending currents of water.
In some cases I carry the top edge of this dummy plate above the level of the
water line so as to prevent the reflux of water and in some cases I extend the lower
edge or edges of this plate below the level of the fire bars on each side & between
the furnaces, but the superficial form and dimensions may be varied according to
circumstances.

page_text: When the top edge of the dummy tube plate is carried up to or above the water
line I also provide a corresponding extension of the back tube plate or an equiva-
lent in the form of a parallel strip along the front or not of the combustion
chamber.
When the dummy tube plate herein described is in position and the boiler is
under steam, the heat from the crown of the furnaces, tube plate and tubes will
cause a continual upward current of steam & water between the dummy & back
tube plates and the supply will be drawn from the lower and cooler strata of
water near the bottom of the boiler which will be made good by descending
currents nearer the front and other parts of the boiler, in this way a constant
. circulation of water may be secured along the front of the back tube plate,
thereby remedying the primary cause of the defects herein first described and
increasing the evaporative efficiency of the boiler.
In new boilers my improvements may be introduced during the building of the
boiler, the dummy tube plate being placed in position when the boiler is stayed &
tubed, and in existing boilers the dummy tube plate may be introduced in
sections or strips, previously prepared, to fit to the sides of the stays & tubes,
such strips and separate sections forming together, a dummy tube plate having
the same effect as a plate built up with the boiler.
Dated this 26th day of November 1891.
R. HEBER RADFORD,
Applicant.
COMPLETE SPECIFICATION.
Improvements in Steam Boilers.
I, RICHARD HEBER RADFORD, of 15, Saint James' Row, Sheffield in the
County of York, Mechanical Engineer, do hereby declare the nature of my inven-
tion, for "IMPROVEMENTS IN STEAM BOILERS," and in what manner the same
is to be performed, to be particularly described and ascertained in and by the
following statement:-
The object of my invention is to improve the circulation of water in tubular
steam boilers more particularly in multitubular boilers of the locomotive or marine
type. During the forced draught trials which have recently been conducted on
board certain ships in Her Majesty's Navy, it was found that the steam boilers
although of the most improved design and construction and apparently answering
all requirements under ordinary conditions, developed when. steaming under
forced draught, such signs of weakness as rendered them unsafe and incapable of
continuing their trials.
As these defects shewed themselves in the same locality, viz. :-in the back tube
- plates and tubes, in all the boilers under trial, there has not been much difficulty in
arriving at the conclusion that the cause arose, primarily, from defective circulation.
Boilers of the type herein referred to are constructed with a combustion chamber,
or combustion chambers, which receive the accumulated heat of the furnace or
furnaces, as the case may be, from which chamber or chambers the heated gases and
flame on their passage through the tubes, niust necessarily impinge upon the tube
plate and ends of the tubes, thereby causing a very rapid evaporation of the water
in contact with the heating surfaces in their locality and although under ordinary
conditions it is possible for sufficient circulation to be maintained when under the
conditions of forced draught, the heat is so intensified and the rate of evaporation is so
increased, that the downward and return currents of water are unable to approach
the tube plate, through the contracted spaces between the tubes, in sufficient
quantity to prevent the tube plates and tube ends from becoming overheated and as
a consequence distortion and leakage quickly follow.
Defects as herein described have in some cases been overcome by increasing the

page_text: water spaces between the tubes but this has only been effected by reducing the
number of tubes.
The object of my invention as already stated is to improve the circulation of
water. It is applicable to multitubular boilers whether for use under natural or
artificial draught. It can be carried into effect without sacrifice of heating surface
and can be applied to existing boilers without any material alteration in their design
or construction, and as the principle of my invention is the same in all boilers to
which it can be applied a description of it as applied to a cylindrical multitubular
marine boiler, with three furnaces and one combustion chamber to each furnace,
will suffice.
In such a boiler I provide what may be called a dummy tube plate or dummy
tube plates, this plate or these plates,, (hereinafter referred to in the singular) I
make of comparatively thin material and approximately of the same superficial
dimensions as the back or front tube plates in it I provide holes corresponding to
those formed for the tubes and stays in the tube plates proper. This dummy plate
I place in position in front of the back tube plate or back tube plates so as to leave
a sufficient space for the ascending currents of steam and water but not sufficiently
wide to allow of the descending currents of water.
In some cases I carry the top edge of this duminy plate above the level of the
water line so as to prevent the reflux of water and in some cases I extend the lower
edge or edges of this plate below the level of the fire-bars on each side and between
the furnaces, but the superficial form and dimensions may be varied according to
circumstances.
When the top edge of the dummy tube plate is carried up to or above the water
line I also provide a corresponding extension of the back tube plate or back tube
plates, or an equivalent in the form of a parallel strip along the front or roof of the
combustion chamber or chambers.
When the dummy tube plate herein described is in position and the boiler is
under steam, the heat from the crown of the furnaces, tube plate and tubes, will
cause a continual upward current of steam and water between the dummy and back
tube plates, and the supply will be drawn from the lower and cooler strata of water
near the bottom of the boiler which will be made good by descending currents
nearer the front and other parts of the boiler, in this way a constant circulation of
water may be secured along the front of the back tube plate or plates thereby
remedying the primary cause of the defects herein first described and increasing the
evaporative efficiency of the boiler.
In new boilers my improvements may be introduced during the building of the
boiler, the dummy tube plate being placed in position when the boiler is stayed and
tubed and in existing boilers the dummy tube plate or plates may be introduced in
sections or strips previously prepared, to fit to the sides of the stays and tubes, such
strips and separate sections forming together, a dummy tube plate or dummy tube
plates having the same effect as a plate or plates built up with the boiler.
The nature of my invention will be better understood on reference to the accom-
panying sheet of drawings in which
Fig. 1, is the front elevation of a three furnace marine boiler one half being shewn
in section on the line C., D.
Fig. 2, is the side elevation of the same boiler, being shewn in section through the
centre of the middle furnace on the line A. B.
The same letters refer to similar parts throughout the several views.
a, a, is the dummy tube plate, the superficial area of one half of which is indicated
by the shade lines in some cases I provide a separate tube plate to cach nest of
tubes.
b, is an extension of the back tube plate or plates in the form of a parallel strip
or strips along the front or roof of the combustion chamber or chambers.
c, is the back tube plate.
d, is the front tube plate.

page_text: 9, 9, are the furnaces.
The arrows indicate approximately the direction of the upward and downward
currents of water in circulation.
Having now particularly described and ascertained the nature of my inven-
tion and in what manner the same is to be performed I declare that what I
.claim is
1. In tubular steam boilers more particularly in multitubular steam boilers of the
locomotive or marine type, placing, fitting and arranging in front of the back tube
plate or back tube plates a dummy tube plate or dummy tube plates, in the manner
and for the purposes substantially as herein described and illustrated.
2. In combination with the dummy tube plate or dummy tube plates described in
Claim 1, placing, fitting and arranging a parallel strip or parallel strips as an
extension of the back tube plate or back tube plates along the front or roof of the
combustion chamber or combustion chambers in the manner and for the purposes
substantially as herein described and illustrated.
Dated this 31st day of August 1892.
R. HEBER RADFORD,
Applicant.