Improvements in Tubes for Steam Boilers.
Year: 1892

page_text: Date of Application, 9th Feb., 1892
Complete Specification Left, 4th Mar., 1892-Accepted. 9th Apr. 1892
PROVISIONAL SPECIFICATION.
Improvements in Tubes for Steam Boilers.
ROBERT BAIRD, 134 St. Vincent Street, Glasgow, Engineer, do hereby declare
the nature of this invention to be as follows:-
In order to more effectually extract the heat passing through boiler tubes, instead
of a smooth internal surface, I have a series of projections running longitudinally in
a spiral form, which have the effect of giving a slight circular motion to the hot
gases, and in a manner skimming off the portions of the gases from which the heat
has been extracted, thus bringing the hotter gases in more immediate and uniform.
contact with the tube.
In cross section the projections show a number of concave pyramids on the inner
circumference of the tube, the points of those pyramids or projections extending
into the tube about one sixth of its diameter.
The sides of the projections are so rounded from point to base that where the
the tubes are used in a horizontal position a quantity of soot would not find a resting
place, as would be the case if they were not so rounded.
Those projections,. looking across the horizontal section of the tube, if flat
(instead of being rounded as described) would become shelves for the accumulation
of soot.
Either before or after the tube strip is bent into a tubular form and welded, a.
twist is given to the tube or, strip which causes the projections to take a spiral form
while the outside, of the tube remains perfectly straight.
My invention has this additional advantage that the channels formed between
the projections present a greater heating surface than the plain tube.
Dated this Eighth of 1000
To
COMPLETE SPECIFICATION.
Improvements in Tubes for Steam Boilers.
ROBERT BAIRD, 134 St. Vincent Street, Glasgow, 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 improvements in heat conducting tubes for steam boilers
and is as follows.
In order to more effectually extract the heat passing through steam boiler tubes,
instead of a smooth internal surface, I have a series of projections running longi-
tudinally round the inner circumference of the tube in a spiral form, as shown Fig. 1.,
which have the effect of giving a slight circular motion to the outside of the hot
gases, and in a manner skimming off the portions of the gases from which the heat
has been extracted, thus bringing the hotter gases in the centre in more iminediate
and uniform contact with the tube.
In cross section the shape of the projections in as shown in end view Fig. 2. the
points of those projections extending into the tube about one sixth of its diameter.
The sides of the projections are so rounded from point to base that where the
tubes are used in a horizontal position a quantity of soot would not find such a good
resting place, as would be the case if they were not so rounded.
Those projections, looking across the horizontal section of the tube, if flat (instead
of being rounded as described and illustrated) would become shelves for the
accumulation of scot.

page_text: Fig. 3. shows tube with one projection-less..
This is to leave more space for lap, welding, and when such tubes are used
horizontally, the part where the projection is out should be kept to the bottom, as
the heating surface there is least available; on account of the soot more readily
accumulating there and acting as a non-conductor...
Either before or after the 'tube strip is bent into a tubular form and welded, a
twist is given to the tube or strip, which causes the projections to take a spiral form
while the outside of the tube remains perfectly straight.
**
In the case of solid drawn tubes the twist may be given through the dies or if
the metal retains its ductility at a red heat they may be solid drawn straight and
twisted afterwards..
My invention has the additional advantages that the channels formed between
the projections present a greater heating surface than the plain tube," and the
gradual thickening of the projections towards the base, make them better heat
conductors:
3
J. ↓
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.....
996
1.
'
W
1. Internal projections, in heat and smoke conducting tubes for steam boilers,
which do not run parallel to the centre or axis of the tube but in a spiral form, so
that they may skim off the gases, from which the heat has been extracted and thus
bring_the_hotter_gases_in_more_immediate_contact with, the heating surface sub-
stantially as described and illustrated.
+
.
2. The conformation of internal projections substantially as described and
illustrated.
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