MENTS IN STEAM BOILERS
Year: 1884

page_text: I, THOMAS CRADDOCK of 20 Cedar Road Walham Green, S.W. in the County of
Middlesex Engineer do hereby declare the nature of my Invention for IMPROVE-
MENTS IN STEAM BOILERS to be as follows:-
All these Boilers, are each one made of a continuous tube, as is illustrated by the
example the three thousand horse power boiler hereafter explains.
This boiler of three thousand horse power, is made of one continuous tube, which
may be (say) from 1 inch to 6 inches in diameter; the water is in this tube, the
generated pressure of the steam being from 100 lbs to 7000 lbs per square inch; and
this without boiler explosions-In steam of 700 lbs pressure per square inch there
is more utilisable power in one Ton of it than in a Ton and half as steam is
commonly generated and used, whilst this Boiler will generate it as less cost per
Ton than the present boilers. By the tube this boiler is made of any form required,
and like all my boilers the fire is within it, and it is self contained as my boilers
have been, as is seen from the reference here given to my specifications found
1840 N° 8432. 1846 N° 11473. 1852 N° 51. 1854 N° 1922. 1857 N° 931. 1857
N° 1162. As this is a supplementary improvement added to those referred to
above, it is right to refer to the Mining Journal 1853 Page 372. Engineer
Dec 1857 Page 342. and Mining Journal Pages 545, 608, and 657 from whence it
it is seen, that by this improvement I substitute one tube for a multiplicity. To
make this a property invention I had to make it in such way as to be safe, workable,
simple in structure, of little cost in construction, yet durable in practice, and
economically effective in every day work. To convey a clear general conception
of how this is done, I present a concise description of a working drawing
illustrative of it, in one of its modifications, as made before March 1880; it will
I think make as much steam per hour, as by my engine will produce three thousand
indicator horse power.
This boiler is 12 feet in diameter and 12 feet high, the
grate and fire-box are 10 feet diameter, and enclosed by water in the tube; above
the fire-box, the water is as it were mingled with the products of combustion with
nothing but the thin metal of the tube to obstruct an equalization of temperature.
Thus an instant circulation ensues; the inlet at the cold water pump end is closed
by the valves of that pump; the other end of this two inch tube is connected with
what I call the separator; in and connected with it is a means whereby the hot
water is separated from the steam, and the hot water as fast as it is driven through

page_text: the generative tube to to the separator, is driven back again through the pipe going
direct to the bottom of the generative tube; to again run its course to the
separator; but the steam passes to the superheater which is made of 1080 feet
of 5 inch tube as a continual pipe. The generator is always full of solid water, or
a mixture of water and steam, so that no injurious burning of the tube can take
place; whilst the circulation having but one tube to pass through, is the safest and
most desirable possible. In this boiler, there is in the 2 inch tube about 5862
square feet of surface exposed to the direct action of the fire, add to this
1350 square feet of heating surface in the superheating, or steam reserve tube
of 5 inches diameter, and the total heating surface is about 7212 square feet. As
I have a well founded belief that 7 lbs of water per hour, as steam, will with my
engine produce for that time the indicator horse power, therefore there is provided
about 20 square feet of heating surface for each cubic foot of water evaporated per
hour. It cannot be required that I explain here the other working drawings which
present this invention in Locomotive and several other modifications all of which
were made before March 1880. The means which in conjuction with the
separator I employ to render this boiler a practical one. The first which I consider
the best, is all in the separator, and is self acting, so that as soon as a current is
produced in the generative tube, which ejects any of its water into the separator
this mode by the aid of steam and pump pistons, or othe equivalent appliance, forces
the water back again to the bottom of this generative tube. With this water the
cold water boiler pump has nothing to do. The motive force is that which forces
it into the separator which is there made to force it back to the bottom of the tube
again. The steam piston may act externally, with the pump or equivalent
appliance still acting intenally. The reader may be reminded that in my former
boilers, I there over balanced the up current by a heavier down current.
suitable situations. this may be done in this case But I have here more powerful
and certain means.
Dated this 18th day of March 1884
In

page_text: I, THOMAS CRADDOCK of 26 Cedar Road Walham Green S.W. in the County of
Middlessex, Engineer, do hereby declare the nature of my invention for IMPROVE-
MENTS IN STEAM BOILERS and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following statement:-
This Invention has for its object Improvements in Steam Boilers.
In the provisional Specification of this Invention all is so plainly indicated as to
require only the explanation of details in conjunction with the reference letters
thus A is the end of the tube that goes to the cold water or feed pump and as this
boiler is made of one continuous tube A this A tube after it has made the generative
part of the boiler reappears as A at the top of the boiler and goes to the separator J
From the separator J the steam that enters it through the pipe A passes out of the
separator through the pipe F to the bottom of the superheating 5 inch tube, which
also coils round the boiler as a continuous tube and from K at the top of the boiler
the steam pipe S going to the Engine is seen The hot gaseous products of
combustion after passing up from the fire box B through its tube part over the fire
box to D pass down the circular flue made by the generative tube A and the
superheating and steam reserve or Steam Chest 5 inch tube K on arriving at the
bottom they pass into the flue, inade by the 5 inch tubes and the hollow brick, and
sheet iron casing; both of these flues go all round the boiler. These gases by the
top flue E enter the chimney as G It will be seen that the generative tube makes
the fire box by winding round it from the bottom on arriving at the top of the fire
box the tube is then wound inward to the centre pipe C and then wound back to
the circumference; thus making the walls of the generative part of the boiler, and
filling the interior with tube, as seen in section in Fig 1. as it proceeds upward.
But it is first made in parts which couple together at the circumference by means
hereafter explained for this purpose I have provided a special joint; but with the
pipes and sockets made with right and left hand threads there is no difficulty even
with such means on this point. These divisions are determined by the in and out
circles of tubes; so that in the boiler under notice there would be 18 divisions;
these being first made they build up the boiler as seen; and admit of one such
division being removed for repair or otherwise without disturbing the other 17.
Of course the large centre pipe is readily removed or it may not be used, As it is
there only to show how fuel can be thrown on the grate through it, if desired; as
well as through the ordinary fire door, which is seen also at I.
The separator at J is an important appendage to the practical success of this
boiler. It is a vessel small in diameter of any height -desired the gases may be
carried round it but otherwise it is not acted on by the fire, and therefore can with
perfect safety be made to have almost any pressure in it. But the pressure will
be the same as that in the generative part of the boiler described. The mechanism
within it is two steam cylinders each 6 inches in diameter and 2 small pumps
each 4 inches in diameter these are of the most simple kind, the Cylinders having
their cranks at right angles start with the slightest increase of pressure on the
impelling side of the pistons, as compared with their exhaust side, the pumps act
direct from the respective piston of the Steam Cylinders. To understand its source
and mode of action suppose the Vessel to have 4 divisions the upper one to be a
plain Cylinder portion, into which the steam and water from A enter at the top of
it so as to throw the water to the bottom of this division whilst the steam will rise
to the top of it, as at the bottom of it is the lower end of a water pipe, suppose

page_text: this pipe 2 feet up to which the pressure of the steam on its surface drives the
water up it before it turns to the well in which the pumps are placed to ensure
their action. We return now to the steam, this flows to the Cylinder valves
which we will call the third division forming as it were the steam valve chest alike
common to both steam Cylinders, and the exhaust of these steam Cylinders goes
into the next division or the division which has communication with the 5 inch
superheating pipes and they with the main engine which may drive the ship across
the Atlantic On referring to tube A and A and the first division explained,
suppose the pressure to be say 200 lbs on the inch, we should have nearly that on
the impelling side of the two stream-pistons but between that and the exhaust side
of them we can have 20 as easily as one; but no such differential pressure is
required as the steam pistons have only the friction of the water through the pipe
acting against the pump pistons to impede their action. It should be borne in
mind that here all is in equilibrium except the friction as before said, the pumps
have merely that resistence opposed to them in forcing the water as fast back as it
is driven into their well through the pipe H and thus keep up a perpetual
circulation through the whole length of tube, be that what it may. In boilers_of
this kind the higher the generative pressure the better will it act because the
weight of equal volumes of water and steam thus approach nearer to each other.
The Engine power can be conveyed from a crank outside, the pumps being still
inside But I am disposed to think it is best with the Engine inside-they then
are self acting altogether and a small differential pressure will put the whole in
motion and it may be work the cold water pump from a crank outside, as my
experience with my steam chest demonstrated that power may be so produced-In
all except form the Locomotive Fig 3 does not differ from this marine boiler except
in the way the hot gases go out of the interior or barrel of it into the flue D to
pass back between the outside of the generative tubes A and the superheating
tubes K-Here the outside casing is sheet iron with asbestos millboard and felt.
The joint for connecting the 18 divisions of tubes, at the circumference to which
reference has been made here; presents its formation so clearly in the drawing
Figs 6 and 7. as not to require further notice than to say the objection to the way
before given is the difficulty of unscrewing those joints when they have been long
in use with high pressure steam; my joint removes this objection as it is made
steam tight by bolts as seen and is therefore easily undone.
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 :-
Steam boilers made of one continuous tube with separator and the other means
before described to ensure a proper circulation through such tube and produce
steam in quantity and quality suitable for the requirements of steam engines.
Dated this 30th day of September 1884.