Improvements in Steam Generators.
Year: 1895

page_text: Date of Application, 1st Nov., 1895-Accepted, 14th Dec., 1895
Improvements in Steam Generators.
ROBERT BAIRD, Engineer, 12 Percy Street, Paisley Road, West, Glasgow, 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 the construction of a steam generator, in which I employ
a steam and water drum, in a borizontal position, having flame tubes running
through its water space from one end to the other, and two water drums which are
also placed in a horizontal position on each side, but at some distance below the
steam and water drum.
Between the steam and water drum, and each of the water drums, I connect
tubes preferably of a large diameter, so as to form a partially enclosed fire place
with flue passages on each side, by which the products of combustion may be
returned from one end of the boiler to the other, and which will retain, and more
completely use the hot gases, than is usual in this class of steam generators.
My invention also provides against trouble arising from the evils of 'unequal
expansion, by having bends in the water tubes which prevent damaging strains
being set up, and at the same time form a compact, accessible boiler, in which the
tubes are easily got at, either for removal, repairs, or cleaning.
The arrangement of flue passages which have for their surroundings mostly
water tubes, absorbs the violent and damaging heat before it enters the smoke
tubes in the steam and water drum, thus reducing the danger of the tube ends
leaking through overheating. A portion of the unconibustible carbon is also
trapped in the flue passages, before entering the smoke tubes, falling where it will
not impair the draught, or cover valuable heating surface.
In order to particularly describe my invention I will do so with reference to
accompanying drawings.
Fig. 1. is a cross vertical section of a modification of my improved steam generator
at markings B. B. on Fig. 2.
Fig. 2. is a longitudinal vertical section at markings A. A. on Fig. 1.
The same letters of reference indicate corresponding parts in Figs. 1. and 2.
f. is the fire space enclosed by the fire grate m. water drums b. b. water
tubes dd and the bottom of smoke tube drum a. The hot gases after passing
the fire bridge n. meet the brick wall 1. Fig. 2. where they split, and enter the flue
passages e. e. Fig. 1. by a space left at the back ends of the rows of tubes d¹ d' and
return to the front or firing end, where they pass into the casing u., and enter the
smoke tubes c. which is the final heating surface before the gases pass, by the
casing p. to the chimney r...
In the rows of tubes d' d' the tubes are kept sufficiently close to each other, so
as not to disturb the main body of the draught, but at the same time to allow a
slight admixture of the gases between the furnace and flues, thus promoting more
complete combustion..
The rows of tubes d and d² form the outer walls of the flue passages e. e. and
are kept quite close so as to exclude as much as possible. the surrounding atmo-
sphere. As shown.at d. Figs...1. and 2. tubes connect with drum a. alternately,
one in the steam space, and the other below the water level. By this arrangement
one tube delivers the water from, and the other returns the water to drums b. b.

page_text: To prevent priming baffle plate j." covers the discharge from tubes do.
Tubes d and d Figs. 1. and 2. are shown with a round bend where they connect
with steam and water drum a. This is for the purpose of giving sufficient spring
to compensate for any unequal expansion, and prevent damaging strains between
one tube and another. Tubes shown at di Fig. 5. are also bent for the purpose of
preventing undue strains. The bending of tubes d and d' gives additional room
in the flue spaces e. e. and sufficient to admit a man, for either cleaning or
repairing.
Figs. 5. and 6. are cross and longitudinal sections showing a greater water tube
heating surface, than is shown at sections Figs. 1. and 2.
In this I employ four rows of water tubes d' d' d' d' on each side, and running
parallel with the furnace. At the back of the furnace or combustion chamber, are
legs d d which form a junction between the steam and water drum a. and water
drums b. b. between which are fixed tubes di forming a back wall. By this means
additional important heating surface is obtained, with a reduction of the material
weight of the boiler. The (row of) bent tubes d', d' on each side of the furnace
- are spaced apart, to freely allow the flame to go round them, and come in contact
with the row of tubes d³.
The straight tubes in the row do, are kept sufficiently close to form a wall round
which the main body of the products of combustion must pass, before entering flue
passage e.
At the back end of the wall formed by tubes d³, some tubes are left out or
: spaced wider apart, to allow the flame to split, and enter the flue passages.
The row of tubes 2 Figs. 5. and 6. are connected to the smoke tube boiler a.
: below the water level, that they may return the water to the water drums b. b.
The outer or casing tubes de deliver in the steam space, and are kept quite close to
each other.
Referring to Figs. 5. and 6. I keep the legs d' d' which connect smoke tube
boiler a. and water drums b. b. large enough in diameter to give access to cross
tubes either for repairing, or cleaning, manhole doors being provided in smoke
tube boiler and water drums, for this purpose.
To completely avert damaging strains being set up by the unequal expansion of
the water tubes in my improved steam generator, I employ only oue row of straight
tubes, which are shown at d¹ Figs. 2. and 3., and d Figs. 5. and 6., all the others
being bent to give the spring necessary to counteract any unequal movement.
To prevent too rapid circulation, or sudden priming from the tubes, the ends are
reduced as shown at Fig. 4. This insures a steady delivery of steam producing
water from the heating surfaces, and prevents the fitful gusts which would conie
from tubes fully open at the ends. The reduced ends have also. the advantage of
allowing the tubes to be arranged in rows, close up along side each other, thus
admitting of their being used as division walls, and retaining sixty per cent. of
strength between the holes in the drums.
To facilitate the fixing or removal of any of the water tubes, I preferably
· connect them to the drums, with a ferrule as shown at Fig. 4. 'When the end of
tube d. is reduced in diameter, the. metal is. thickened, this, besides leaving ample
margin for tapping in the screw threads, leaves a considerable. surface at the end,
which is turned up with a true face, a corresponding true face is cut on the plate,
round the hole through which the ferrule d³ passes. The head of the ferrule is
fitted in a countersunk seat in the plate, so that when inserted into the end of the
tube, and screwed up tight, it makes a close metal to metal joint, between the tube
and the plate. The tightness of this joint is further insured by taking a thin fillet
out of the inner edge of the tube, and a similar fillet out of the faced hole in the
plate. When the joints are together this will leave a small annular cavity, as
shown at x. Fig. 4. into which a soft metal ring may be placed, of a section
- somewhat larger than required to fill the space; which when subjected to pressure,
will be forced into a corner where it can not get away, and seal up the joint, against
any possibility of a leak.
·

page_text: The ferrule &³ is turned in its place by inserting a square mandril, in the square
hole as shown at Fig. 3.
This improvement in fastening tubes is shown and described, with the exception
of the soft metal fillet packing ring, in the Patent granted to me for Improvements.
in steam generators No. 1576, 1895.
In order that the ends of the tubes may not be overheated, so as to disturb their
connections with the drums, and that their outward diameter may be uniformly
carried out, I place a shield, formed of a short piece of tube, loosely over the
reduced ends as shown at z. Fig. 4.
The space between the reduced end and the shield, may be filled with any
fire-resisting, non-conducting substance.
To promote and regulate the water circulation in the steam and water drum,.
I employ baffle plates j¹¹ which also shield and protect the bottom row of smoke
tubes c. The rush of water from water tubes d' do is received on baffle plates j
and diverted round the sides of the water space. This will have the effect of
bringing a return of water down amongst the central smoke tubes c. to the opening
at the bottom of the lower flange of baffle plates 11 thus having a tendency to
keep the bottom of the steam and water drum, which is exposed to the greatest
heat, free from sediment.
Referring to letters on accompanying drawings, which have not been mentioned
in the foregoing particular description; k. on Figs. 1. and 5. is casing and lagging
round the outside of the boiler. h. h. h. water level test cocks. w. steam supply
stop-valve. v. spring safety-valve. o. firing door. t. on Figs. 1. and 2. is cleaning
door at bottom of steam and water drum.
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;
1st. The construction of tubulous boilers having water tubes, connecting with a
steam and water drum, and water drums, bent, and so arranged to prevent straining
from unequal expansion, substantially as described and illustrated at Figs. 1.
and 5.
2. The construction of tubulous boilers having tubes, connecting with a steam.
and water drum, and water drums, placed so as to form flue passages, by which the
hot gases may be returned from one end of the boiler to the other, and which will
be of easy access for repairs, or cleaning, substantially as described and illustrated.
3. The construction of tubulous boilers having tubes connected to drums by
ferrules. The seat of the connection having annular cavity, as described and
illustrated at . Fig. 4.
4. The construction of tubulous boilers having water legs forming junctions,
between steam and water drum, and water drums, between which are tubes as
illustrated at d7 Figs. 5. and 6.
5. The construction of tubulous boilers having the reduced ends of the tubes,
where they connect with the drums, protected from the excessive heat by ferrules,
which enclose heat-resisting, non-conducting substance, as described and illustrated
at . Fig. 4.
6. The construction of tubulous boilers having baffle plates in steam and water
drum, substantially as described and illustrated at j. and Figs. 1. 2. 5. and 6.
7. The construction of tubulous boilers, according to the modifications, as.
described and illustrated in the accompanying drawings.
Dated this 31st day of October 1895.