Improvements in Tubular Steam Boilers.
Year: 1890

page_text: Date of Application, 22nd Aug., 1890
Complete Specification Left, 16th June, 1891-Accepted, 22nd Aug., 1891
PROVISIONAL SPECIFICATION.
Improvements in Tubular Steam Boilers.
1, ERNEST PETERSEN, of Kertch, Crimea, Russia, Engineer, do hereby declare
the nature of this invention to be as follows:-
My invention relates to tubular steam boilers, more particularly marine boilers,
wherein horizontal or inclined fire tubes are fixed in tube plates, and it has for its
object to greatly increase the heating surfaces offered by the tubes and consequently
to effect a considerable economy in fuel by more effectually taking up the heat from
the flames and combustion gases.
In tubular boilers of present construction, the tubes require to be made of
comparatively large diameter (generally about 34 in. diameter) in order to enable
them to be conveniently fixed in the tube plates by expanding them. Tubes of such
a large size offer only a small heating surface in proportion to the large volume of
combustion gases passing through them, and, as a consequence, a large proportion of
such gases passes through without giving off their heat. Furthermore, in order to
obtain a sufficient heating surface with such tubes it is necessary to employ such a
number of them that the sectional area offered by them for the passage of the gases
exceeds many times the inlet area for air of the fire grate.
The result hereof is that the combustion gases mostly pass through the upper
rows of tubes, leaving the lower-most ones either entirely or partially inoperative.
According to my present invention I obviate these disadvantages by employing
fire tubes of small diameter applied in such a manner that while the fixing by
expansion can still be employed, both the heating surface is largely increased and
the passage
for the gases is considerably decreased.
For this purpose the said tubes of small diameter are not fixed directly into the
tube plates, but have their ends fixed into corresponding holes formed in the closed
inner ends of short tubes or cylindrical cups of large diameter, the outer ends of
which are fitted by expanding them in the ordinary way into corresponding hole in
the tube plates.
Thus for example, I may fit a group of say, seven tubes of 1 in. diameter into
the inner closed ends of cups of 5 ins. diameter, six thereof being arranged at
equal distances apart round the circumference and the seventh in the centre.
As tubes of such small diameter cannot be fixed in the cups by expanding them
into the holes, I form the holes in the latter of such a diameter that the cup
requires to be expanded by heating for the tubes to be introduced into the holes, so
that, on cooling, the cup will be shrunk on to the ends of the tubes, thus forming a
rigid combination of the group of small tubes with the two cups. In order to
enable the compound tube thus formed to be readily removed, I prefer to make the
holes at the circumference of the cup in such a position that the projecting ends of
the tubes are made to abutt against a recessed shoulder in the sides of the cup, so
that on driving the cup at the one end inwards for removing the tubes, these and
the other cup will be forced backward therewith as though they were all of one
piece.
The above described construction has the further advantage over the fire tubes
now employed that whereas these are rendered quite useless on being removed, only
the cups have to be renewed with my construction, the tubes themselves being quite
free from injury.
Although I have given the above mentioned sizes of the tubes and cups as being
suitable, they may be made larger or smaller.
Dated this 22nd day of August 1890.
ABEL & IMKAY,
Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in Tubular Steam Boilers.
I, ERNEST PETERSEN, of Kertch, Crimea, Russia, 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 tubular steam boilers, more particularly marine boilers,
wherein horizontal or inclined fire tubes are fixed in tube plates, and it has for its
object to greatly increase the heating surfaces offered by the tubes and consequently
to effect a considerable economy in fuel by more effectually taking up the heat from
the flames and combustion gases.
In tubular boilers of present construction, the tubes require to be made of
comparatively large diameter (generally about 3 in. diameter) in order to enable
them to be conveniently fixed in the tube plates by expanding them. Tubes of
such a large size offer only a small heating surface in proportion to the large
volume of combustion gases passing through them, and, as a consequence, a large
proportion of such gases pass through without giving off their heat. Furthermore,
in order to obtain a sufficient heating surface with such tubes it is necessary to
employ such a number of them that the sectional area offered by them for the
passage of the gases exceeds many times the inlet area for air of the fire grate.
The result hereof is that the combustion gases mostly pass through the upper
rows of tubes, leaving the lowermost ones either entirely or partially inoperative.
According to my present invention I obviate these disadvantages by employing
fire tubes of small diameter applied in such a manner that while the fixing by
expansion can still be employed, both the heating surface is largely increased and
the passage for the gases is considerably decreased.
For this purpose the said tubes of small diameter are not fixed directly into the
tube plates, but have their ends fixed into corresponding holes formed in the closed
inner ends of short tubes or cylindrical cups of large diameter, the outer ends of
which are fitted by expanding them in the ordinary way into corresponding holes
in the tube plates.
Thus for example 1 may fit a group of, say, seven tubes of 14 in. diameter into
the inner closed ends of cups of 5 ins. diameter, six thereof being arranged at
equal distances apart round the circumference, and the seventh in the centre.
As tubes of such small diameter cannot well be fixed in the cups by expanding
them into the holes by an expanding tool, I, according to one arrangement, form
the holes in the latter of such a diameter that the cup requires to be expanded by
heating for the tubes to be introduced into the holes thereof, so that, on cooling,
the cup will be shrunk on to the ends of the tubes, thus forming a rigid com-
bination of the group of small tubes with the two cups. In order to enable the
compound tube thus formed to be readily removed, I prefer to make the holes at
the circumference of the cup in such a position that the projecting ends of the
tubes are made to abutt against a recessed shoulder in the sides of the cup, so that
on driving the cup at the one end inwards for removing the tubes, these and the
other cup will be forced backward therewith as though they were all of one
piece.
The above described construction has the further advantage over the fire tubes
now employed that whereas these are rendered quite useless on being removed, only
the cups have to be renewed with my construction, the tubes themselves being quite
free from injury.
Although I have given the above mentioned sizes of the tubes and cups as being
suitable, they may be made larger or smaller.
The accompanying drawings shew my above described invention applied by way
of example to a marine boiler. Fig. 1 shews a part longitudinal section of a
boiler, Fig. 2 shews a part cross section through the smoke box on line x x and

page_text: Figs. 3, 4 and 5 shew respectively an enlarged part longitudinal section, a cross
section, and an end view of the compound tubes.
A A A are ordinary fire tubes but of considerably smaller diameter than those
usually employed, say from in. to 1 in. diameter; the two ends of these tubes
are let into steel cups B, of say from 5 in. to 7 in. diameter, a group of seven
tubes A being conveniently combined with one pair of cups, so that there is one
central one and six arranged symetrically round it, as shewn. The cups B are
accurately turned on their outer surface and fit into correspondingly accurately
bored holes in the tube plates C, in which they are secured by being expanded in
the usual manner, the projecting ends being by preference rivetted over as shewn.
When the tubes A are of a small diameter, they may be secured to the cups B
by merely shrinking the latter on to them as before described, but if they are of
sufficient size to allow of their being expanded by an expanding tool, then I prefer
to make the holes in the cup for receiving them with shallow grooves so that by
expanding the ends of the tubes into such grooves as shewn, the two parts are
effectually secured together, so that when it is desired to remove one of the com-
pound tubes, this may be readily effected by removing the external bulge of the
cup B at one end, and then driving back the entire compound tube through the
hole at the other end. In addition to or instead of shrinking the cups B on to
the ends of the tubes A, or expanding these into the cups as described, they may
also be secured by brazing, or the tubes and cups may be welded together, or the
cups may be cast on to the ends of the tubes, or the tubes and cups may even be
formed of one casting of cast steel.
The tubes being effectually secured in the cups as described, it will be seen that
no leakage can occur such as frequently takes place in the joints of the ordinary
tubes with the tube plates, and the outer surfaces of the cups being turned and the
holes in the tube plates accurately bored as described, any leakage of these joints
will also be practically prevented.
For facility of fixing and removal, the cups may be slightly coned on their outer
surface in such manner that the front cup has its outer end largest while the back
cup has its inner end largest.
Thus, the holes in the tube plates being coned in a corresponding manner, it will
be seen that the fixing and withdrawal of the compound tubes from the front end
will be greatly facilitated, as in driving them in, the cups will at once be wedged
tight in their holes.
The holes in the tube plates for receiving the compound tubes are arranged in
parallel rows, and between each group of four is provided a tubular stay D, screwed
into the tube plates and rivetted over on the outside.
By means of the above described construction of compound tubes, I ain enabled
as before stated, to greatly increase the heating surface of the tubes while at the
same time reducing their collective area for the passage of the furnace gases, so
that these are made to pass more or less uniformly through the whole of the tubes
instead of passing in great measure through the upper tubes only.
Furthermore, as the tubes in each group are considerably nearer to each other
than to the tubes of the contiguous groups, it follows that the body of water
between the tubes of each group will become more highly heated than the body of
water between the contiguous groups, which will have the effect of producing a
circulation of water round the individual tubes whereby the steam will be effectually
liberated therefrom, and incrustation and burning of the tubes prevented.
The advantages of my above described compound tubes may be summarised as
follows
--
1. By their use a very great increase of effective heating surface is attained,
resulting in a corresponding economy of fuel.
2. Greatly increased durability of the boilers, inasmuch as the cause of the rapid
wearing out of tubular boilers of present construction is due to the fact that the
intense heat of the furnace is imparted to the water directly behind the back tube
plate in great measure through the back ends of the tubes, so that owing to the

page_text: energetic steam production at that point, the water is in great measure prevented
from maintaining the effective contact with the tube plate required for keeping it at
a comparatively low temperature, and in consequence the tube plate soon becomes
burnt. With my compound tubes however, the flames have first to pass through
the cups of comparatively large diameter offering comparatively small surface for
the transmission of heat, before they enter the small tubes, and thus the energetic
production of steam will only take place at a certain distance from the tube plate,
so that this will always have more or less solid water in contact with it.
3. The total internal sectional area of the tubes being reduced to that actually
required for the draught, instead of being greatly in excess in order to obtain the
necessary heating surface, as in ordinary boilers, they will all act efficiently for the
transmission of heat, instead of the lower ones being comparatively inoperative as
at present, and as a consequence, boilers affording a certain amount of steam power
can be made of smaller dimensions than at present.
4. In those cases where the tubes are effectually secured to the cups either by
expanding into grooved holes in the latter, or by brazing or welding or casting the
two together, they will also act as stay tubes, and consequently the separate stay
tubes, not requiring to be as strong as in ordinary boilers, can be made of uniform
thickness with the fire tubes. As a consequence, the whole of the tubes will
expand uniformly, instead of the thicker stay tubes expanding more than the fire
tubes and thus producing unequal strains on the tube plates which cause the joints
to leak.
5. As a considerable proportion of the total steam pressure to which the tube
plates of ordinary boilers are subjected is in the present case transferred to the
inner flat face of the cups B, it follows that the tube plates are subjected to a
considerably reduced total strain, so that either they can be made considerably
thinner for bearing the ordinary steam pressure, or if they are kept of the usual
thickness the steam pressure in the boiler can be considerably increased beyond that
ordinarily used.
6. As the fire tubes can be made comparatively thin on account of their small
size, the heat will be much more effectually transmitted through them.
7. For the reason hereinbefore stated, there will be an effectual circulation of
water round the separate tubes, liberating the steam, and preventing incrustation.
When incrustation does occur, the tubes can be removed even though it may be
considerable, as the outside measurement of each group of tubes is considerably
less than the diameter of the holes in the tube plate into which the cups are fixed.
8. The labour and time expended in taking out and replacing the whole of the
ubes of a boiler for cleaning purposes will be very considerably less than with an
ordinary boiler, as instead of having to remove each tube separately, a group of
seven or other number forming a compound tube is removed at one time.
Having now particularly described and ascertained the nature of this inven
tion and in what manner the same is to be performed, I declare that what 1
claim is :-
1. The construction and use for tubular boilers of compound fire tubes consisting
of the combination of several tubes of small diameter having their ends secured in
cylindrical cups of comparatively large diameter which are adapted to fit into holes
of corresponding diameter in the tube plates of a boiler, substantially as described.
2. A tubular steam boiler having compound fire tubes consisting of groups of
tubes of small diameter the ends of which are secured in cylindrical cups which in
their turn are secured in holes of corresponding diameter in the tube plates,
substantially as described.
Dat we do of In 1901
ABEL & IMRAY,
Agents for the Applicant.