IMPROVEMENTS. IN STEAM ENGINES AND BOILERS, AND THEIR APPURTENANCES
Year: 1860

page_text: PROVISIONAL SPECIFICATION left by Lavington Evans Fletcher at the
Office of the Commissioners of Patents, with his Petition, on the.
31st May 1860.
I, LAVINGTON EVANS FLETCHER, of Upper Norwood, in the County of
Surrey, do hereby declare the nature of the said Invention for "IMPROVEMENTS.
IN STEAM ENGINES AND BOILERS, AND THEIR APPURTENANCES," to be as follows:-.
On the 18th March 1858, I obtained Letters Patent, No. 550, for an.
Invention consisting of improvements in marine engines and boilers and,
their appurtenances, the principal object of which improvements was the:
economy of fuel. Having pointed out in the said Specification at some length: .
the principles by which I propose to effect an economy in the consumption of:
fuel, I need only in the present instance explain the detail arrangements of.
my present improvements, which are, however, not only applicable to marine.
engines, but to steam engines in general, the object still being the same, viz.,;
the economy of fuel.
My boiler, to which I propose to apply the artificial blast, the advantage:öf.
which was pointed out in the aforesaid Specification, is a vertical 'tubular
boiler, with a set of return tubes. The flame from the furnace first ascends
through the direct tubes, and then descends through the return, tubes. Tho."
feed water is pumped into the boiler at the bottom of the return (tubes, and
rises in an opposite direction to the current of. hot air descending: through
these return tubes. I place a partition plate of non-conducting: matériab
between the hot and cold water, and when desirable keep the level of: the

page_text: water round the return tubes higher than that of the water round the direct
tubes. I increase the durability as well as the evaporative power of the boiler
by promoting an artificial circulation of the water by means of one or more
centrifugal pumps.
In cases where the artificial draft is used, and where it is found desirable to
regulate the current through the tubes, I place straight rods, solid or hollow,
inside the tubes, and thus leave only an annular space through which the
flame or hot air passes. These rods are applicable to any tubular boiler
having an artificial draft. To secure the superheating of the steam, I place
a diaphragm across the boiler, and allow the vertical flame or flue tubes to pass
through it. To this diaphragm I fasten on its upper side other short tubes
which encircle the flame or flue tubes, forming an annular space around them,
and through which the steam is compelled to pass and become superheated, the
diaphragm preventing its resaturation. This system of superheating is appli-
cable to all vertical tubular boilers, whether with or without return tubes.
It has long been acknowledged that the most economical form of boiler must
permit the cold water to rise and meet the descending hot air, since that
would admit of the fullest abstraction of the heat; this, the arrangement of the
return tubes accomplishes. Still two difficulties have prevented its general
adoption, and more especially in marine work. One difficulty is the insufficiency
of the natural draft with the descending current caused by the return tubes;
and the second difficulty the injury that the lower tube plate at the furnace
crown has 'been found to sustain, caused by insufficient circulation of the water
consequent on the form of boiler. By the application of the artificial draft
and centrifugal pumps I remove both those difficulties, and thus render
available the economic advantages of this boiler. In superheating steam it is
very usual to employ straight tubes fixed at each end into tube plates, which I
object to on two grounds, firstly, because any irregularity in the expansion or
contraction of these tubes injures the joints at the fastenings; and secondly,
because the fastenings of straight tubes being at two faces at the opposite end
of each tube, it is consequently necessary, in order to repair these tubes in case
of accident, to have access to the superheater at two sides, say at the back and
front, which in many positions, especially on board ship, is very inconvenient.
1 obviate these difficulties by constructing my superheater of horse-shoe
shaped pipes, which may be fixed singly, or grouped together into a series,
and formed into sliding trays; or, I form continuous zig-zig, or any other con-
venient shaped pipes into sliding trays. When I construct the superheater
of distinct horse-shoe shaped pipes, I attach both ends of the horse-shoe to
the same tube plate, and thus each of these pipes can freely expand or contract

page_text: without straining the joint of the tube plate, or interfering with the action of
any of the other pipes. In case of any one of these pipes becoming defective,
I can plug up both ends of the horse-shoe by merely having access to one tube
plate. When I group together a series of these horse-shoe shaped pipes, and
form them into sliding trays, or form continuous zig-zag pipes, or any other
convenient shaped pipes iuto sliding trays, I connect the inlet and outlet pipes
of these trays to tube plates or faces accessible from one side of the super-
heater; thus, in case of any pipe in the group failing, the sliding tray can
easily be disconnected and withdrawn for repair, and in the meantime the
steam openings blanked up, or another tray substituted for the defective one.
It will be seen that the construction of these trays allows as perfect freedom
for expansion or contraction as the arrangement of horse-shoe shaped pipes.
My superheating apparatus is applicable not only to marine boilers, but to
every description of boiler; neither is its use confined to the purpose of
superheating steam alone, but may be applied as a steam boiler, in which case
artificial circulation of the water would be necessary. In some cases I prefer
to heat the superheating apparatus from the main boiler fire or fires, and in
others I employ a superheating stove, in which I have a supplementary fire.
Again, in other cases, I superheat the steam by means of a separate boiler of
the vertical tubular class, fitted with a diaphragm and short tubes, for super-
heating, as previously described. In this case the steam to
led to the supplementary boiler, and all passes through it. In superheating
steam in stationary boilers, the pipes have been placed, in some cases, in the
side flues between the boiler and brickwork, and in others at the base of the
chimney; in many cases this is impracticable, and always attended with
the inconvenience of opening the flues.
be superheated is
My Invention overcomes this difficulty by placing the superheating pipes in
the furnace flue behind the fire-bridge, and so arranging the apparatus that it
can be passed in through the furnace.
In using superheated steam it has been frequently found necessary to temper
it down after heating it lest it should injure the cylinder. The superheated.
steam may be tempered down in many ways, either by injecting into it a jet of..
water or plain saturated steam, or by surface condensation caused by a shower
of water on the outside of the steam pipe, or by a current of cold water passing. :
through a pipe surrounded with the superheated steam.. Neither of these
plans are my Invention, but I have invented a self-acting apparatus for
adjusting the intensity of either of the above, or other convenient methods of
tempering the superheated steam, so as to keep the steam as nearly as possible
at the same temperature.

page_text: My apparatus consists of a cylinder, which is immersed in the superheated
steam, and takes the same temperature. This cylinder is fitted with a piston
or plunger, capable of easy motion, and the cylinder is filled or partly filled
with water. The heat of the surrounding superheated steam expands the
water within the cylinder, or raises steam from it, and thus generates a
pressure corresponding to the temperature of the superheated steam; this
pressure communicates motion to the piston or plunger, and the piston or
plunger regulates the flow of the plain steam, or of injection or shower water,
When it is not
or of the current aforesaid, by an ordinary valve or cock.
convenient to attach to the engine a special pump for the purpose of supplying
the jet or shower as described above, I propose to take the supply from the
feed pipe; and in order to raise the pressure of the water when required to do
so slightly above that in the boiler, I place a check valve slightly loaded
between the pump and the boiler. In my surface condenser the cooling
surface is flat, and is formed into what I call condensing pockets, and which
may be made of any suitable metal. Surface condensers have already been
made with flat cooling surfaces, but these have been in the generality of cases
virtually large flat tubes, open at both ends. My cooling chambers are only
open at one end, and thus I call them pockets. I place within these pockets
diaphragm strips rivetted to. the sides, which prevent them from collapsing or
bulging, and at the same time give the steam or water a horse-shoe course in
passing through these pockets, so that the steam or water enters and leaves
the pockets at the same face. The cooling pockets being only attached to one
face are free to expand or contract without injury, and can easily be discon-
nected and removed. I propose to make the joint at mouth of cooling pockets
with a sheet of vulcanized india-rubber, but do not confine myself to that
method. The flat sides afford great facility in cleaning both inside and outside.
.It will be seen that the superheater and surface condenser are constructed on
the same principle. The horse-shoe shape of the superheating pipes, and the
pocket system of cooling surface, in which the steam or water traverse a horse-
shoe course, renders in each case a joint face at only one end necessary, and
thus both, superheating pipes and condensing pockets have ample freedom for
expansion or contraction, and can also be easily removed for examination or
repair. Where not convenient to apply the screws or other attachments at
the joint face, the pockets may be pressed up to the face by screws applied at
the back with elastic washers or other means for allowing for expansion.
These pockets are equally applicable whether they are surrounded by the cold
water bath while the exhaust steam to be condensed circulates within them,
or whether the exhaust steam to be condensed surrounds them while the cold

page_text: means.
bath water circulates within them, and also whether the cold bath water be
drawn or forced through by means of a pump or pumps or other convenient
It is very important to be able, in case of derangement of any of the
metallic cooling surface, to be able to have recourse to the ordinary mode of
condensation by injection; and I am able to do this by following arrange:
ments I make the external case of my surface condenser air-tight and steam-
tight, and strong enough to stand atmospheric pressure. I pass the water
through the condenser with an exhausting pump in preference to a forcing
pump, but I do not propose when in regular work to maintain a vacuum in
the cold bath chamber, since I object to that plan on account of its entailing
a considerable addition to the size of the air pump, as well as an additional
load to the engine. I connect an ordinary injection pipe to the steam space;
whether the steam space, as stated above, be in connection with the inside or
the outside of the pockets. With this arrangement all that is requisite to
convert the surface condenser into an ordinary injection condenser is to shut
off the supply of cold bath water, and let on a supply of injection water through
the injection pipe. But since the air pump would then have an extra amount
of duty thrown upon it, and which would be too much for its size, I bring to
its help the cold bath water pump; and I do this by opening a valve, or by
any other simple means of establishing a communication between the two
pumps. Thus the condenser can at any time be converted into an ordinary
injection condenser, with two air pumps; or in case of an accident to either
air pump, can work on with the other.
Another arrangement for converting the surface condenser into an injection
condenser is to connect an injection pipe to the cold bath water chamber,
whether that chamber is in connection with the outside or the inside of the
_condensing pockets, and to establish means of communication between the
steam chamber and cold bath chamber for the passage of the steam, the pumps
having the means of communication as before. By this arrangement, in order
to convert the surface condenser into an injection condenser, it is only neces-
sary to shut off the cold bath water and let on the injection water through the
injection pipe, as in the previous arrangement, and open the communication
between the steam chamber and cold bath chamber, as well as between the
two pumps.
The injection pipes mentioned above are not absolutely necessary, since
throttling the supply of cold bath water, and allowing it to issue through its
ordinary pipe, might be made to answer the purpose. The above arrange-
ments are equally applicable whether the condensing surface consists of tubes
or pockets, or whatever the character of the cooling surface may be. In

page_text: applying surface condensers to marine engines it is important to have such an
arrangement of engine that the condenser may be easily accessible, and that
there may be room to withdraw the pockets or tubes. My arrangement of
pockets is favourable to a compact form of engine, since I only require
access to the top and to one side of the condenser, say the front; I therefore
adopt the following arrangement of engine for driving screw propellers :-
I place the surface condenser above the crank shaft, and fix an annular cylinder
on each side of the condenser; I set these cylinders at an angle with one
another of 90° or thereabouts, the connecting rods from each of these cylinders
being coupled to and driving one and the same crank. In some cases I carry
one or both of the piston rods through the bottom as well as the top cylinder
cover, and thereby drive the air pump or any other pump or pumps that may
be convenient.
In applying a surface condenser to screw engines already built of the
inverted cylinder or over-head engine class, I place the surface condenser
above the hot well, and fix the air pump on one side of the condenser, and the
cold bath water pump on the other side of the condenser. I drive the air
pump and cold bath water pump by the same levers that are at present
commonly used in this class of engine for driving the ordinary air pumps.
I leave the ordinary air pumps, hot well, and injection condenser intact.