Improvements in Furnace Tubes and Flue Tubes for Boilers.
Year: 1894

page_text: Date of Application, 31st Aug., 1894
Complete Specification Left, 24th May, 1895-Accepted, 6th July, 1895
PROVISIONAL SPECIFICATION.
Improvements in Furnace Tubes and Flue Tubes for Boilers.
I, EDGAR CONISTON MILLS of No. 40 Victoria Buildings, Manchester, in the
County of Lancaster do hereby declare the nature of this invention to be as
follows:-
My invention consists of forming furnace tubes and flue tubes of boilers with solid
internal and external fins or flanges of the same continuous substance as the tube, and
I am aware
so disposed as that each external fin is a continuation of an internal one.
that internal fins have been previously used both formed with the tube and
attached thereto and 1 do not claim any novelty for such fins in themselves, but
I claim novelty for the external fins in combination with the internal fins and for
their special disposition as hereinafter described and for forming both internal and
external fins solid with the tube by casting or forging processes. I prefer to
dispose the fins or flanges spirally or helically along each length of the tube, the
internal and external fins coinciding, the angle of spiral being not of great
importance though I prefer an angle of from thirty to forty-five degrees to the
axial plane. In one form of my invention I make the spiral or helical fins on each
length of tube throughout the length of a flue to run in the same direction.
another form I make them alternately in opposite directions.
In
As the pressure on such boiler flues as are in general use in Lancashire and
Cornish and vertical boilers is always an external pressure and the metal is
therefore in compression, such flue tubes with helical flanges or fins can be safely
and inexpensively made of steel cast in a mould, and part of my present invention
consists in so producing them and also in casting them in suitable alloys of copper,
tin and zinc or known and suitable compositions of bronze or of other metal or
metals. I believe that with the improved methods of welding by electricity and
otherwise now in operation and by improved methods of rolling, such flue tubes
having internal and external helical fins or flanges can be produced in wrought
metal, and part of my invention consists in so producing them and I claim the user
of such furnace and flue tubes as are formed substantially in accordance with this
Specification whether produced by casting or forging or welding processes.
object of my invention is to increase the power of heat transference of furnace and
flue tubes. The internal fins dipping into the hot gasses absorb the heat which
travels laterally along them and is given off by the corresponding external fin
immersed in the water in the boiler.
The
By disposing them spirally, a "whirling" action is set up in the flue gasses
causing agitation and so bringing the gasses from the centre of the flue into
contact with the plates. To increase this action I sometimes insert central discs
or conical ended drums at intervals along the flue. I make the external fins
correspond with the internal so as to afford a continuous and direct vehicle for the
heat. The external fins being helical pockets or hollows where steam bubbles
could lodge are avoided. The helical form of internal and external fins or flanges
serves greatly to strengthen the flue tube.
The fins or flanges are preferably made taper in section having the greater
amount of metal at the root.

page_text: Improvements in Furnace Tubes and Flue Tubes for Boilers.
I, EDGAR CONISTON MILLS of No. 40 Victoria Buildings, Manchester, in the
County of Lancaster 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 consists of forming furnace tubes and flue tubes of boilers with
solid internal and external fins or flanges of the same continuous substance as the
tube and so disposed as that each external fin is a continuation of an internal one.
The object of my invention is to increase the power of heat transference of
furnace and flue tubes. The internal fins dipping into the hot gasses absorb the
heat which travels laterally along them and is given off by the corresponding
external fin immersed in the water in the boiler.
I am aware that internal fins have been previously used both formed with the
tube and attached thereto and I do not claim any novelty for such fins in themselves,
but I claim novelty for the external fins in combination with the internal fins and
for their special disposition as hereinafter described and for forming both internal
and external fins solid with the tube by casting or forging processes. I prefer to
dispose the fins or flanges spirally or helically along each length of the tube, the
internal and external fins coinciding, the angle of spiral being not of great
importance though I prefer an angle of from thirty to forty-five degrees to the
axial plane. In one form of my invention I make the spiral or helical fins on each
length of tube throughout the length of a flue to run in the same direction. In
another form I make them alternately in opposite directions.
As the pressure on such boiler flues as are in general use in Lancashire and
Cornish and vertical boilers is always an external pressure, and the metal is
therefore in compression, such Hue tubes with helical flanges or fins can be safely
and inexpensively made of steel cast in a mould, and part of my present invention
consists in so producing them and also in casting them in suitable alloys of copper,
tin and zinc or known and suitable compositions of bronze or of other metal or
metals. I believe that with the improved methods of welding by electricity and
otherwise now in operation and by improved methods of rolling, such flue tubes
having internal and external helical fins or flanges can be produced in wrought
metal, and part of my invention consists in so producing them and I claim the user
of such fuinace and flue tubes as are formed substantially in accordance with this
Specification whether produced by casting or forging or welding processes.
In the accompanying drawings
Fig. 1, Sheet 1, shews an external view of one length or ring of a boiler flue
suitable for an ordinary Lancashire boiler and constructed in accordance with my
invention.
Fig. 2, Sheet 2 shews a cross section of the same on the line y, Fig. 1.
Fig. 3 is a detached section through the line a¹y, Fig. 1.
A is the ordinary flue tube flanged at the ends for riveting as shewn at a.
B are the external spiral fins or flanges which are shewn in this case at an angle
of forty-five degrees to the axial plane. They are shewn reduced in depth towards
each end for the purpose of allowing access to the end flange for inserting and
closing the rivets. This reduction is also clearly shewn in Fig. 2 at b.
Care the internal fins or flanges which are not shewn in Fig. 1 but their ends c
appear in Fig. 2 and they are clearly shewn in section in Fig. 3. As drawn these
internal flanges are intended to be of equal depth throughout their length but are
rounded off at each end. I do not however bind myself to this form as they may
be tapered similarly to the external flanges. It will be observed that the external

page_text: flanges B do not extend to the flue end flanges a but stop short of the commencement
of the radius forming the commencement of the flange a. The object of this is to
allow the steam which forms in contact with the tube to escape freely at the upper
ends of the spiral flanges B. The spiral form assists such escape of steam and in
addition promotes circulation of the water. The internal flanges correspond in
length and angle with the external ones. The spiral disposition in their case sets
up a whirling action in the flue gasses causing agitation and so bringing the gasses
from the centre of the flue into contact with the plates. To increase this action
I sometimes insert central discs or conical ended drums at intervals along the flue.
I make the external fins correspond with the internal so as to afford a continuous
and direct vehicle for the heat. The helical form of internal and external fins or
flauges serves greatly to strengthen the flue tube. The fins or flanges are preferably
made taper in section having the greater amount of metal at the root.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed 1 declare that what I
claim is :-
1. The flue tube for steam boilers constructed with coinciding internal and external
spirally disposed flanges or webs formed as part of and solid with the flue tube
substantially as and for the purposes hereinbefore described and illustrated in the
accompanying drawings.
2. The flue tube with spirally disposed flanges reduced in depth at each end
substantially as and for the purposes herein-before described and illustrated in the
accompanying drawings.
3. The flue tube with spirally disposed flanges, such flanges stopping short. of
the ends of each ring substantially as and for the purposes hereinbefore described
and illustrated in the accompanying drawings.
4. Flue tubes for boilers with spirally disposed internal and external flanges and
in which the direction of the spiral is reversed in each alternate flue ring substan-
tially as and for the purposes hereinbefore described.
5. In combination with flue tubes with internal and external spirally disposed
flanges a central displacer or displacers formed as discs or drums substantially as
and for the purposes herein before described.
6. Flue tubes for steam boilers with internal and external coinciding spirally
disposed flanges constructed by casting processes.
7. Flue tubes for steam boilers with internal and external coinciding spirally
disposed flanges constructed by forging, welding or rolling processes or a com-
bination of these.
-Dated this 23rd day of May 1895
EDGAR CONISTON MILLS.