IMPROVEMENTS IN STEAM BOILERS, AND IN APPARATUS FOR FEEDING THE SAME, AND FOR EFFECTING CIRCULATION THEREIN
Year: 1862

page_text: LETTERS PATENT to William Macnab, of Greenock, in the County
Renfrew, North Britain, Engineer, for the Invention of "IMPROVEMENTS
IN STEAM BOILERS, AND IN APPARATUS FOR FEEDING THE SAME, AND FOR
EFFECTING CIRCULATION THEREIN.
Sealed the 3rd February 1863, and dated the 12th August 1862.
PROVISIONAL SPECIFICATION left by the said William Macnab at the
Office of the Commissioners of Patents, with his Petition on the 12th
August 1862.
I, WILLIAM MACNAB, of Greenock, in the County of Renfrew, North
Britain, Engineer, do hereby declare the nature of the said Invention of
"IMPROVEMENTS IN STEAM BOILERS, AND IN APPARATUS FOR FEEDING THE SAME,
AND FOR EFFECTING CIRCULATION THEREIN," to be as follows, that is to say :-
This Invention of improvements in 'steam boilers, relates partly to internally-
flued cylindrical boilers for steam of moderate pressure, and partly to boilers
of bigh pressure, the heating, surface of which consists principally of tubes,
with the water inside them.

page_text: In the improved cylindrical boiler, there may be one or two large furnace
tubes, the back ends of which open into a combustion chamber, communicating
with a number of small tubes, by which the gases return to a smoke box at the
front. The furnace mouth or mouths are made to project forward from the
main body of the boiler, as far as the front of the smoke box, being surrounded
by a kind of annular water space. The gases return from the smoke box to
the back by two or more comparatively large fluo tubes, traversing the steam
space of the boiler. Two or more such boilers may be conveniently arranged
side by side, or one, two, or more. pairs may be arranged back to back, and
communicating with a single central funnel, but having separate combustion
chambers, into which provision may be made for introducing air. To give
sufficient steam space, a cylindrical steam receiver may be laid along the top
cavity between the two boilers of each pair, and an additional flue tube may be
passed through each receiver.
In the improved tube boiler, the tubes are placed horizontally in tiers, the
tubes of one tier being connected with those above, by bent joints, alternately
at each end, so as to form a serpentine arrangement. Water is pumped into
these tubes, so as to circulate continuously through them, being delivered from
them, along with the steam generated into a receiver, wherein it is separated.
from the steam, and whence it finds its way back again to the pump or
pumps.
:
One of the present improvements consists in dividing the tiers of tubes into
three or more distinct sets, each set acting so far as a separate generating
apparatus. The circulation of water through the lowest set may be caused by
one pump, whilst that through the two upper sets may be effected by a second
pump, or by two other separate pumps. Each set of tubes is provided with a
distinct discharge, communicating with the receiver for the steam and water..
either by separate or combined passages. One or more of the uppermost tiers
of the tubes may be arranged for the reception and passage through of the feed
water, prior to its introduction into circulation in the boiler.
Another improvement consists in disposing hollow iron cylinders or pipes
across the top of the sido walls, to which are bolted the hanging tube plates,
and on which also rests the brickwork forming the covering flue or chimney
over the tubo chamber. They may also serve as additional steam chambers,
wherein the steam may receive the available heat remaining in the fire gases,
as they pass upwards from the tube chamber.
By another improvement the waste fire gases are turned into a flue formed
down the side wall, in which flue tubes or pipes may be arranged for the pas-

page_text: sage through of the feed water, doors being also arranged. therein for cleaning
the tubes.
The improved apparatus for feeding boilers, and for effecting circulation
therein, consists according to one modification of a steam cylinder, directly
connected to the piston or bucket of the pump; the parts being proportioned
so as not to work at an excessive speed. The motion of the piston is reversed
by means of a tumbler movement, acting on the valves and reversing them
suddenly as each end of the stroke is reached.