Improvements in the Smoke Tubes of Tubular Steam Bouers.
Year: 1885

page_text: Improvements in the Smoke Tubes of Tubular Steam Bouers.
"
I, JOHN HENRY JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex
Gentleman do hereby declare the nature of said Invention for "IMPROVEMENTS IN
SMOKE TUBES OF TUBULAR STEAM BOILERS which Invention has been communi
cated to me from abroad by Augustin Normand et Cie of 67 rue de Perry, Havre,
Seine Inférieure in the Republic of France Engineer to be as follows:-
"
It is known that in the smoke tubes of tubular steam boilers the rate of
production of steam per unity of length increases in proportion to the nearness
of the part under consideration to the fire box tube plate. This fact is clearly
demonstrated by the experiments of Petiet and others.
The steam thus produced at the extremities of the tubes where they are inserted
into the tube plate or sheet acting together with the steam supplied by the said
tube sheet itself diminishes the density of the water in contact with these surfaces
and the refrigerating power is reduced in proportion as the combustion is more
active, the volume of water smaller and the escape of steam more difficult. The
consequence is that these surfaces become over heated and weakened and expand
excessively. Possibly the water may even sometimes pass into the spheroidal
condition. Leakages consequently often occur at the point of junction of the tubes
with the tube sheet.
It would therefore be evidently an advantage to increase the volume of water at
this part of the boiler and to facilitate the escape of steam which is produced
therein provided that the section of the passage for the products of combustion or
beating gases be not contracted in consequence This may be done.
In fact boiler tubes are usually provided with iron or steel rings or ferrules in
the tube sheet of the fire box. The internal diameter of the tubes may conse-
quently be reduced to that of the inside of the rings without contracting the section
of the passage for the gases.-This reduction of the diameter may be extended for
a certain distance say from about four to twenty inches for example or even to
three feet and upwards without perceptibly diminishing the evaporation as the
production of steam by a given heating surface or in other words the quantity of
31

page_text: heat transmitted is proportional not only to the extent of this surface but also to
the refrigerating power of the liquid in contact therewith. In the present instance
the heating surface is slightly diminished, at the contracted part of the tubes, but
as the density of the mixture of steam and water surrounding it is at the same
time increased; there are good reasons for assuming that the quantity of heat
transferred is not reduced. On the contrary if the diameter of the tubes were
uniform throughout their length and enlarged at the tube plates only, an arrange-
ment frequently employed, the heating surface would be much reduced and the
speed of the heating gases increased thereby producing a serious diminution in the
production of steam.
This Invention consists in reducing the diameter of the smoke tubes in the
vicinity of the tube plate or sheet of the fire box for a fraction of their length
the contraction commencing as near as possible to the internal surface of the tube
plate. The diameter may be so reduced as to render the section of the passage in
the contracted part either greater or less than that of the inside of the rings or
ferules although it appears preferable that the two sections should be equal.
The said Invention is applicable to all tubular steam boilers in which the hot
gases pass in the interior of the tubes and is especially suited for high pressure
boilers having horizontal or nearly horizontal tubes such as boilers for locomotives,
torpedo boats and steamers worked with forced draught.
The invention may be applied to tubes made in one piece or otherwise, to
cylindrical or corrugated tubes arranged horizontally or vertically and irrespective
of their dimensions and the nature of the metal of which they are composed.
The transaction from the large to the small diameter of the tubes may be
gradual as in the tube N or sudden as in the tube M.
Both arrangements are shown in the drawing annexed. The contracted part of
the tube may be either a true cylinder or slightly conical or curved.
The Invention is independent of the mode of connecting the tubes to the tube
plate even when the employment of rings or ferules is dispensed with.
The annexed drawing shews one of the arrangements which may be employed
In order to show more clearly the advantages presented by the Invention par-
ticularly with respect to the generation of steam especially when the tubes are
horizontal or nearly so, the left hand part of the drawing shows the ordinary
arrangement at AA and the right hand part the improved arrangement at M N.
It will be observed that the width of the passage provided for the steam at the
contracted part of the tubes is increased by the difference between the internal
diameters of the tubes and of the rings or ferules. Assuming that the internal
diameter of the rings is less by a quarter of an inch than the normal inside
diameter of the tubes and that the normal thickness of the body of water between
the tubes is three quarters of an inch the width of the longitudinal passages for
the escape of steam is increased by the improved arrangement by one quarter of an
inch or about thirty three per cent in the vicinity of the tube sheet or tube plate
of the fire box where the evaporation is most active and without diminishing the
section of the passage for the heating gases.
With regard to the means whereby the local reduction of the diameter of the
tubes may be obtained it will suffice to mention two, namely dies and draw plates.
The employment of smoke tubes of varying section has been patented several
times but these arrangements are entirely distinct from the one forming the object
of the present invention.
Having thus described the invention as communicated to me by my foreign
correspondents and reserving the right to vary the materials, proportions, dimen-
sions and accessary arrangements according to circumstances, what I desire to
protect is :-
First. The novel application, to all descriptions of tubular boilers, in which the
hot gases pass in the interior of tubes, of the new system or arrangement of tubes
having their diameter reduced in the vicinity of the tube plate or tube sheet of the

page_text: fire box, the reduction of the diameter being extended along a fraction of their
length always less than half the said length.
Second. Tubular boilers wherein the hot gases pass in the interior of tubes to
which the improved arrangement of tubes is applied.
•
Third. The arrangements represented merely as an example in the annexed
drawing reserving the right to determine according to the application the most
suitable length and the best profile for that part of the tubes where the diameter
is contracted.
I JOHN HENRY JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex
Gentleman do hereby declare the nature of my Invention for "IMPROVEMENTS
IN THE SMOKE TUBES OF TUBULAR STEAM BOILERS," which Invention has been
communicated to me from abroad by Augustin Normand et Cie of 67 rue de Perry,
Havre Seine Inférieure in the Republic of France Engineers and in what manner
the same is to be performed to be particularly described and ascertained in and by
the following statement :-
It is known that in the smoke tubes of tubular steam boilers the rate of
production of steam per unity of length increases in proportion to the nearness
of the part under consideration to the fire box tube plate. This fact is clearly
demonstrated by the experiments of Petiet and others.
The steam thus produced at the extremities of the tubes where they are inserted
into the tube plate or sheet acting together with the steam supplied by the said
tube sheet itself diminishes the density of the water in contact with these surfaces
and the refrigerating power is reduced in proportion as the combustion is more
active, the volume of water smaller and the escape of steam more difficult. The
consequence is that these surfaces become over heated and weakened and expand
excessively-Possibly the water may even sometimes pass into the spheroidal
condition Leakages consequently often occur at the point of junction of the tubes
with the tube sheet.
It would therefore be evidently an advantage to increase the volume of water
at this part of the boiler and to facilitate the escape of steam which is produced

page_text: therein provided that the section of the passage for the products of combustion or
heating gases be not greatly contracted in consequence. This may be done.
In fact Boiler tubes are usually provided with iron or steel rings or ferrules in
the tube sheet of the firebox. The internal diameter of the tubes may conse-
quently be reduced to that of the inside of the rings without contracting the
section of the passage for the gases. This reduction of the diameter may be
extended for a certain distance say from about four to twenty inches for example
or even to three feet and upwards without perceptibly diminishing the evaporation
as the production of steam by a given heating surface or in other words 'the
quantity of heat transmitted is proportional not only to the extent of this surface
but also to the refrigerating power of the liquid in contact therewith.
In the
present instance the heating surface is slightly diminished at the contracted part of
the tubes but as the density of the mixture of steam and water surrounding it is at
the same time increased, there are good reasons for assuming that the quality of
heat transferred is not reduced. On the contrary if the diameter of the tubes were
uniform throughout their length and enlarged at the tube plates only an arrange-
ment frequently employed, the heating surface would be much reduced and the
speed of the heating gases increased thereby producing a serious diminution in
the production of steam.
This Invention consists in reducing the diameter of the smoke tubes in the
vicinity of the tube plate or sheet of the fire box for a fraction only of their length
the contraction' commencing as near as possible to the internal surface of the tube
plate. The diameter may be so reduced as to render the section of the passage in
the contracted part either greater or less than that of the inside of the rings or
ferrules although it appears preferable that the two sections should be equal.
The said Invention is applicable to all tubular steam boilers in which the hot
gases pass in the interior of the tubes and is especially suited for high pressure
boilers having horizontal or nearly horizontal tubes such as boilers for locomotives,
torpedo boats and steamers worked with forced draught.
The Invention may be applied to tubes made in one piece or otherwise to
cylindrical or corrugated tubes arranged horizontally or vertically and irrespective
of their dimensions and the nature of the metal of which they are composed.
The transition from the large to the small diameter of the tubes may be gradual
us in the tube N or sudden as in the tube M.
Both arrangements are shown in the drawing annexed to my provisional
Specification. The contracted part of the tube may be either a true cylinder
or slightly conical or curved.
The Invention is independent of the mode of connecting the tubes to the tube
plate even when the employment of rings or ferrules is dispensed with.
The drawing filed with my provisional Specification shews one of the arrange-
ments which may be employed. In order to shew more clearly the advantages
presented by the Invention particularly with respect to the generation of steam
especially when the tubes are horizontal or nearly so, the left hand part of the
drawing shows the ordinary arrangement at A. A and the right hand part the
improved arrangement at M. N. It will be observed that the width of the passage
provided for the steam at the contracted part of the tubes is increased by the
difference between the internal diameters of the tubes and of the rings or ferules-
Assuming that the internal diameter of the rings is less by a quarter of an inch
that the normal inside diameter of the tubes ând that the normal thickness of the
body of water between the tubes is three quarters of an inch the width of the
longitudinal passages for the escape of steam is increased by the improved arrange-
ment by one quarter of an inch or about thirty three per cent in the vicinity of
the tube sheet or tube plate of the fire box where the evaporation is most active
and without diminishing the section of the passage for the heating gases.
With regard to the means whereby the local reduction of the diameter of the
tubes may be obtained it will suffice to mention two, namely dies and draw plates.

page_text: The employment of smoke tubes of varying section has been patented several
times but these arrangements are entirely distinct from the one forming the object
of the present Invention.
The materials, proportions dimensions and accessory arrangements employed in
carrying out this Invention may evidently be varied according to circumstances.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what
I claim is
First. The novel application to all descriptions of tubular boilers in which the
hot gases pass in the interior of tubes of the new system or arrangement of tubes
having their diameter reduced in the vicinity of the tube plate or tube sheet of the
fire box the reduction of the diameter being extended along a fraction of their
length always less than half the said length.
Second. Tubular boilers wherein the hot gases pass in the interior of tubes to
which the improved arrangement of tubes is applied.
Third. The arrangements represented merely as an example in the annexed
drawing, reserving the right to determine according to the application the most
suitable length and the best profile for that part of the tubes where the diameter
is contracted.
בד