Improvements in Supplying Air to the Furnaces of Marine Boilers.
Year: 1891

page_text: Date of Application, 18th Mar., 1891
Complete Specification Left, 17th Dec., 1891-Accepted, 23rd Jan., 1892
PROVISIONAL SPECIFICATION.
Improvements in Supplying Air to the Furnaces of Marine Boilers.
I, PERCY LEWIS ISAAC, of Winchester House, 50 Old Broad Street, in the
City of London, Engineer, do hereby declare the nature of this invention to be as
follows:-
My improvements relate to the furnaces of marine boilers which are fitted with
hollow fire bars through which air is conducted to the back of the bridge.
According to my invention the air pipes or passages which are led through the
fire bars are continued to the front of the furnace through a specially made dead
plate and are made to open into a box or casing from which an air supply pipe
is led
up into the stokehold ventilator.
By this means a portion of the air that is ordinarily forced down the usual cowl-
headed ships ventilator would be forced into the box or casing and through the fire
bars to the back of the bridge thereby securing a forced draught in a simple way
with the benefit of better combustion and generally the advantages claimed for
forced draught without any risk of cold air impinging on the tube plates or other
parts of the boiler, which has hitherto been so disastrous.
Dated this 17th day of March 1801
COMPLETE
SPECIFICATION.
Improvements in Supplying Air to the Furnaces of Marine Boilers.
I, PERCY LEWIS ISAAC, of Winchester House, 50 Old Broad Street, in the
City of London, Engineer, do hereby declare the nature of this invention and in
what manner the same is to be performed to be particularly described and ascer-
tained in and by the following statement :-
This invention has for its object improvements in supplying air to the furnaces
of marine boilers.
I employ fire bars having an air tube through the centre of each fire bar, and I
extend these air tubes into the front dead plates to air chambers, so boxing in the
open ends of the air tubes and from the ends of such boxes, or chambers, I lead air
pipes up into the stoke-hold ventilators.
By these means the air that is ordinarily forced down the usual cowl-headed ship's
ventilators is further forced through pipes into the air chambers and thence through
the air tube fire bars. The air becomes heated and is with the furnace gases
carried into the combustion chambers. By these means an increased draught is
obtained with the benefit of better combustion and, generally, the advantages
claimed for forced draught, without any risk of cold air impinging on the tube
plates, or other parts of the boiler, which has hitherto been so disastrous.
Dampers may be fitted to the internal draught pipes in the stokeholds so that
when desired the draught from the ship's cowls can be utilised wholly for ventilating
the stokeholds by opening sliding doors on one side of the above dampers.
Air is thus carried close down to the stokehold floors or much lower than
heretofore thereby bringing about a better distribution of air and ventilation.
In order that my said invention may be fully understood and readily carried into
effect I will proceed to describe the drawings hereunto annexed.

page_text: DESCRIPTION OF THE DRAWINGS.
Figure 1 is a front elevation partly in section of a portion of a marine boiler to
which my invention is applied.
Figure 2 is a vertical section of the same.
a a are the furnaces and bb are the fire bars. The fire bars are such as are
made by Messrs. Caddy & Co. Limited of Nottingham; there is an air tube through
the centre of each fire bar.
In each furnace I extend these air tubes at 6 through the front dead plate c into
the air box or chamber d. At the other end of the furnace the tubes terminate
beneath the bridge e and they deliver air into the combustion chamber f. g is the
ordinary stokehold ventilator; it passes up to the open air where it is provided
with a collecting cowl. A part of the air delivered by the ventilator g is made to
enter pipes h h which are connected in the manner shown with the boxes or
chambers d.
At h¹ are dampers in the pipes and at are sliding traps which may be opened
to let out the air when it is not required to urge the fire.
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
1. Apparatus for supplying air to marine boiler furnaces consisting of fire bars
with air passages through them terminating at one end at the bridge and at the
other end in a box or chamber connected by pipes with the ordinary stokehold cowl
ventilator as herein set forth.
2. Apparatus such as is represented by the annexed drawings for supplying air to
the furnaces of marine boilers.