Improvements in Steam-boiler Flues and Fire-boxes.
Year: 1890

page_text: Date of Application, 27th Mar., 1890
Complete Specification Left, 21st Jan., 1891-Accepted, 21st Feb., 1891
PROVISIONAL SPECIFICATION.
Improvements in Steam-boiler Flues and Fire-boxes.
I, DONALD BARNS MORISON, of 8, Albion Terrace, Hartlepool, in the County
of Durham, Engineer, do hereby declare the nature of this invention to be as
follows:-
Corrugated boiler flues or fire-boxes of circular cross section have been proposed to
be made of various forms of longitudinal section, two forms being usually adopted in
practice, riz., that in which the corrugations are of uniform kind, that is to say in
which the external ridges and the internal ridges have practically the same depth,
width and curvature; and that in which the strengthening ridges project outward
and the intervening portion of the flue is cylindrical or as seen in longitudinal
section straight.
In practice I have found both these forms of corrugations open to objection. In
the form first mentioned, the channels between the outwardly projecting corrugations
being comparatively narrow have the effect of causing concentration of deposit so
that within a given time these parts become incrusted or coated with scale of
greater thickness than is the case with other forms of flue and the development of.
small cracks often results.
The secondly mentioned form of corrugated flue or fire-box is objectionable
because as I have found, the strength given by the outwardly projecting or
strengthening corrugations is not uniformly distributed and when scale accumulates
upon the flue the cylindrical portion between the aforesaid corrugations is found
practically to have a tendency to sag or form indentations or pockets thus causing
a diminution of the resistance of the flue or fire box to collapse.
Now the purpose of my invention is to obviate the foregoing objections to which
end construct a flue or fire-box with corrugations as follows. In cross section
the flue or fire-box is cylindrical. In longitudinal section the inwardly projecting
corrugations are curved to much greater radii than the outwardly projecting corru-
gations or ridges. These outwardly projecting corrugations or ridges thus form the
supporting corrugations from which the inwardly projecting corrugations receive
additional strength, the curved form of the inwardly projecting corrugations
assisting to distribute this additional strength in a uniform manner.
The inwardly projecting corrugations a flue or fire-box constructed in accordance
with this invention are less angular than those of the first named form and are
therefore less liable to the objections enumerated with regard to that form, at the
same time the hollows can be more easily scaled and when necessary repaired.
As compared with the second form of flue or fire-box mentioned there is in mine
no flat part between the strengthening corrugations and the strength of the flue or
fire-box is more uniformly distributed.
The thickness of the material of which the flue or fire-box is made may be
uniform or it may vary.
When the thickness varies I deem it advantageous to
make it greatest at the outwardly projecting corrugations and least at those
projecting inwardly the variation in thickness being symmetrical on each side of
each corrugation.
1000

page_text: COMPLETE SPECIFICATION.
Improvements in Steam-boiler Flues and Fire-boxes.
I, DONALD BARNS MORISON, of 8 Albion Terrace, Hartlepool, in the County
of Durham, 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 :—-
Corrugated boiler flues or fireboxes of circular cross section have been proposed
to be made of various forms of longitudinal section, two forms being usually adopted
in practice viz. that in which the corrugations are of uniform kind, for example as
represented in Fig. 1 of the annexed drawings, in which the external corrugations a
and the internal corrugations bhave practically the same depth, width and curvature;
and that represented by way of example in Fig. 2 in which the strengthening ribs a
project outward and the intervening portion of the flue is cylindrical, or, as seen
in longitudinal section, straight.
In practice I have found both these forms of flues or fireboxes open to objection.
In the form first mentioned (Fig. 1) the channels c between the outwardly projecting
corrugations a being comparatively narrow have the effect of causing concentration
of deposit on the water side of the internal corrugations b, and as these
corrugations 6 are from their position subjected to a greater intensity of temperature
than any other part of the furnace the material becomes so distressed that cracks
often develop.
The secondly mentioned form of flue or firebox (Fig. 2) is objectionable because,
as I have found the strength given by the outwardly projecting ribs a is not
uniformly distributed throughout the material between the said ribs and when scale
or solid matter accumulates upon the flue, the cylindrical portions 6 between the
aforesaid ribs a especially midway between the ribs are found practically to have a
tendency to " sag" or form indentations or pockets.
It has also been proposed to construct a boiler flue or firebox of a series of
annular or partially annular flutings connecting a corresponding series of sharp
ridges and to make the metal thicker at the ridges than elsewhere but in such forms
as have been proposed the sharp ridges are difficult to obtain in process of
.manufacture.
Now the purpose of my invention is to obviate the foregoing objections to which
end I construct a flue or firebox with corrugations as follows. In cross section the
flue or firebox is cylindrical. In longitudinal section the outwardly projecting
corrugations are curved and form the supporting corrugations to the inwardly
projecting or suspended corrugations which are curved to much greater radii than
the supporting corrugations.
Fig. 3 of the drawings is a longitudinal vertical section of part of a flue or fire-
box, which as already described is in cross section circular whilst in longitudinal
section the inwardly projecting corrugations B are curved to much greater radii so
as to have much less curvature than the outwardly projecting curved corrugations A
which as shewn have a curvature similar to that of all the corrugations of the
ordinary corrugated flue or firebox shewn in Fig. 1. The outwardly projecting
corrugations A form the supporting corrugations from which the inwardly projecting
corrugations B receive additional strength to resist collapse, the curved form of the
inwardly projecting corrugations assisting to distribute this additional strength in
a uniform manner.
As will be obvious the radii or curvature of the inwardly projecting corrugations B
can be varied for example as shewn in Figs. 4 and 5 which are longitudinal vertical
sections of parts of flues or fireboxes." The depth of the corrugations may also be
varied as shewn.
The inwardly projecting corrugations B in a flue or firebox constructed in
accordance with this invention are much less angular than those of the first named
form (Fig. 1) and are therefore less liable to form receptacles for the concentration

page_text: of deposit and avoid to a great extent the dangers arising therefrom whilst the
hollows on the water side are more easy and less costly to scale and when necessary
to patch and repair.
As compared with the second form of flue or firebox mentioned (Fig. 2) there is
in mine no flat part between the ribs A, A. and the strength of the flue or firebox is
more uniformly distributed especially under ordinary working conditions. As
compared with the third form of flue or firebox hereinbefore mentioned there
are in mine no sharp ridges, and no difficulty is experienced in process of
manufacture.
The thickness of the material of which the flue or firebox is made may be
uniform or it may vary.
In Figs. 3 4 and 5 the material is shewn as of uniform
thickness.
Figs. 6, 7, 8 and 9 are longitudinal sections each shewing part of a flue or fire-
box according to this invention in which the thickness is greatest at the outwardly
projecting and supporting corrugations A the variation in thickness -being
symmetrical about the central portion of each corrugation.
The corrugations can be formed in any suitable manner as for example by rolling
as well understood.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that I do not
claim broadly the constructing of a corrugated boiler flue or firebox with inwardly
projecting corrugations having a greater radius or less curvature than the outwardly
projecting ridges, but what I do claim is :-
The manufacture of corrugated steam boiler flues or fireboxes in which (a) both
the outwardly projecting corrugations and the inwardly projecting corrugations
are of curved form as seen in a longitudinal section of the flue and (b) the material
between the outwardly projecting and supporting corrugations on the water side
of the flue or firebox is disposed in the form of inwardly projecting and suspended
corrugations of less curvature than that of the said curved outwardly projecting
and supporting corrugations whether the metal be of uniform thickness as represented
in Figs. 3, 4 and 5 of the drawings hereunto annexed, or of greatest thickness at
the outwardly projecting and supporting corrugations A the variation in thickness
being symmetrical about the central portion of each corrugation as represented in
Figs. 6, 7, 8 and 9 of the drawings hereunto annexed.
Dated this 91st day of January 1801
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.