IMPROVE- · MENTS IN THE CONSTRUCTION OF TUBULAR BOILERS AND FURNACES
Year: 1881

page_text: LETTERS PATENT to Richard Garrett and Frank Garrett, both of Leiston
Works, Leiston, in the County of Suffolk, for an Invention of "IMPROVE- ·
MENTS IN THE CONSTRUCTION OF TUBULAR BOILERS AND FURNACES."
PROVISIONAL SPECIFICATION left by the said Richard Garrett and Frank
Garrett at the Office of the Commissioners of Patents on the 11th March
1881.
RICHARD GARRETT and FRANK GARRETT, both of Leiston Works, Leiston, in
the County of Suffolk. "IMPROVEMENTS IN THE CONSTRUCTION OF TUBULAR
BOILERS AND FURNACES."
The chief object of this Invention is to effect an economy in the consumption of
the fuel burned in the furnaces of tubular steam boilers, whether that fuel be coal,
coke, or straw.
The Invention applies chiefly to traction and
of which lie horizontally and lead directly from
smoke box.
portable engines, the fire tubes
the combustion chamber to the
furnace which lies beyond the
The combustion chamber, or that part of the
bridge, it is now proposed to cut off from the front part of the furnace more
completely than heretofore by extending the bridge, or a screen which serves the
purpose of a bridge, to a height approaching near the crown of the furnace.
The steam and water space above the crown of the furnace we connect by a
pipe in the vertical plane of the bridge with the water space or jacket below the
ash pit.
This is for the purpose of keeping up a good circulation in the front part of the
boiler, but the tube also serves as a stay for the crown of the furnace, and as an
abutting piece for lumps of fireclay which form the raised bridge, and thus con-
stitute a combustion chamber between the fire place and the boiler.
Extending through the boiler at a slightly lower level than the crown of the
furnace is a horizontal row of air tubes, which reach from the tube plate of the
combustion chamber through the smoke box to the outer framing which carries

page_text: the doors of the smoke box, and below this horizontal row is a central vertical
row of air pipes reaching also from the tube plate to the smoke box door frame.
The outer ends of all these tubes are open to the atmosphere, and they serve to
draw in air and convey it in a heated state to the combustion chamber, by which
means the gases of combustion as they pass over the bridge will become mingled
with a supply of oxygen sufficient to ensure their complete conversion into flame.
In order the better to ensure this mingling of the air and gases the inner ends
of the air pipes may be fitted with conical nozzles, which will cause the air to be
deflected in the form of a funnel shaped jet from each pipe.
In some cases in place of this arrangement of air pipes we may pass air pipes
of smaller diameter concentrically through a given number of the ordinary fire
tubes, and thereby deliver the air in a heated state into the combustion
chamber.
This arrangement will apply chiefly to boilers and furnaces already constructed.
Another improvement which we propose to introduce into the furnaces of steam
boilers is to construct the boiler at or below the level of the fuel on the grate bars
with hollow in place of solid stays. These stays we may apply at the sides and
at the front and back of the furnace for the purpose of admitting air directly to
the mass of the fuel.
Our improvements we also propose to adapt in part to vertical tubular boilers
and furnaces which have or can be provided with a smoke box for heating the
air, pipes, and thereby raising the temperature of the air passing through those
pipes to the furnace.
By supplying air to the furnace through pipes heated in the smoke box, a
material economy of heat is ensured, the incoming air absorbing heat from the
smoke box and carrying it back to the furnace to be utilized.
In some cases we propose to modify the manner of delivering the air in vertical
tubular boilers. The air tubes we insert concentrically in the fire tubes, closing
their lower ends and piercing them laterally to allow of the air being delivered
within the fire tubes. By this means the heated gases passing upward through
the fire tubes will be caused to play upon the inner periphery of those tubes,
and thereby act "more efficiently in raising the temperaturo of the water in the
boiler.
-

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Richard Garrett and Frank Garrett in the Great Seal Patent
Office on the 10th September 1881.
RICHARD GARRETT and FRANK GARRETT, both of Leiston Works, Leiston,
in the County of Suffolk, England. "IMPROVEMENTS IN THE CONSTRUCTION OF
TUBULAR BOILERS AND FURNACES."
The chief object of this Invention is to effect an economy in the consumption of
the fuel burned in the furnaces of portable and locomotive engine boilers, and also
the prevention of smoke and the arrest of sparks and solids arising from the
burning fuel, as, for instance, the silicious deposit emanating from burning straw,
by means of a thorough intermixture of a plentiful but regulated supply of heated
air with the gases of combustion on their passage from the furnace to the flue
tubes. The Invention further applies in part to tubular boilers of the marine and
the vertical type.
In applying our Invention to portable or locomotive boilers we cut off from the
furnace the combustion chamber by extending the bridge, or a screen which serves
the purpose of a bridge, to a height approaching near to the crown of the furnace,
and into this chamber at or about the level with this bridge we admit heated air
which meets the gases of combustion as they pass over the bridge, and mingles
with them to impart the requisite amount of oxygen thereto for ensuring their
conversion into flame.
Extending through the boiler at a slightly lower level than the crown of the
furnace is a horizontal row of air tubes which reach from the tube plate of the
combustion chamber to and through the smoke box.
The outer ends of these tubes are open to the atmosphere, and they serve to
draw in air and convey it in a heated state to the combustion chamber for the
purpose just explained.
The manner of carrying out the Invention will vary slightly according to the
construction of the boiler and furnace to which it will be applied.
We will first explain the manner of adapting our improvements to a portable
boiler of a somewhat novel construction.
In Sheet I. of the accompanying Drawings Fig. 1 is a longitudinal section of
this boiler and furnace with the improvements for which we have obtained Letters
Patent adapted thereto; Fig. 2 is a cross section taken in the line 1, 2, of Fig. 1,
or through the furnace; Fig. 3 is a partial sectional plan of the furnace; and Fig. 4
is an elevation of the smoke box end of the boiler.
In these Figures A is the furnace, B is the bridge, and C the combustion
chamber; D, D, are the flue tubes leading from the combustion chamber through
the barrel of the boiler, and ending in the tube plate of the smoke box E.
The bridge B is composed of two hinged doors which are made of frames,
of iron faced with fire brick. These doors are capable of being swung back, as
indicated by dots in Fig. 3, to expose the ends of the flue tubes for cleaning and
repair.
The bridge B it will be seen rises nearly to the crown of the furnace, and near
the level of the top row of flue tubes, and it thus serves to contract the space
through which the flame and gases of combustion pass from the furnace to the
combustion chamber.
These tubes marked D¹ wo now propose to convert into air tubes by inserting
into their forward onds short tubes F, F, which extend to the front of the smoke
box and are made fast to the end plate thereof.

page_text: These tubes F are open to the atmosphere, and their inner ends are drawn down
Bo as to enable them to fit tightly in the tubes D'. Air passages are thus established
between the smoke box end of the boiler and the combustion chamber, and when
the fire is burning and a sufficient draught is established in the furnace, air will be
drawn in through these tubes, heated by the gases in the smoke box, and supplied
to the combustion chamber near the level of the raised bridge.
In front of the outer ends of these tubes are hung small swing regulating doors f
which when dropped into place (as best shewn in the enlarged views, Figs. 5) will
close the tubes and prevent smoke escaping therefrom when the furnace fire is first
ignited.
So soon however as the furnace becomes hot, these doors fare to be raised
sufficiently to admit an adequate supply of air which will pass into and through
the tubes F to the combustion chamber. We prefer to connect the steam and water
space above the crown of the furnace pipe H, in the vertical plane of the bridge
with the water space or jacket below the ash pit.
This is for the purpose of keeping up a good circulation of water in the front
part of the boiler, and of supporting the corrugated crown of the fire box, which is
extended beyond the usual length of the fire grate to afford the necessary space
for the fire bridge B and the combustion chamber C, and we avail ourselves of
the central position of this pipe to use it as an abutting piece for the hinged doors
constituting the bridge.
The smoke box is surrounded by a water jacket I, I, through the upper part of
which the chimney is sunk to meet the crown of the smoke box to which it is
rivetted. Thus a large increase of heating surface is provided and the gases.
of combustion being robbed of much of their heat by the surrounding water
and by the air tube F are caused to leave the boiler at a comparatively low
temperature.
The water jacket I, I, instead of being connected with the boiler proper may be
separated therefrom, as illustrated in Figs. 1, Sheet III., in which case it is utilized
as a water heating chamber through which the feed water must be forced on its
passage to the boiler proper. Fitted in the smoke box E, is a baffler G, which is
capable of being moved to and from the flue tubes by means of handles with which
it is provided. This baffler is supported by angle pieces which bear against the two
sides of the chamber, leaving a sufficient space all round between its circumference
and the walls of the chamber for the passage of the gases to the chimney, and
causing these gases to impinge more effectually on the air pipes F and upon the
heating surfaces of the boiler.
This arrangement of boiler and furnace is intended especially for burning light
fuel, such as straw and vegetable refuse, which require for their efficient
consumption not merely the use of a combustion chamber (the transverse wall or
partition forming which serves to deflect the flame and particles of unconsumed
fuel and prevent their direct entrance into the fuel tubes), but also require
the supply of heated air to impinge upon the flame as it rises over the bridge.
In Sheet II., Fig. 6 is a longitudinal section of the boiler and furnace of an
ordinary portable engine with our improvements adapted thereto; Fig. 7 is a cross
section taken on the line 1, 2, of Fig. 6 or through the furnace; and Fig. 8 is a
sectional plan of the furnace.
As the same letters of reference are used in these Figures and in those of Sheet I.
for the like parts, the same description will apply to both Sheets of Drawing. In
this arrangement it will be seen that the hinged doors forming the bridge B have
no pipe to abut against, they therefore lap the one over the other at the
middle of the furnace, and are capable of being swung to the dotted position when
required.
When however it is desired to heat boilers of the ordinary locomotive type by
a fuel which is not so liable as straw to form while burning a deposit in the
combustion chamber, and which is slower of combustion and requires a more
extensive grate area, the fire bridge may be removed and the air tubes D' may be

page_text: converted at pleasure into flue tubes by simply removing the short tubes F and
closing the openings made for them in the end of the smoke box by the means-
above described.
As a modification of the means employed for the conversion into flame of the
gases of combustion, we propose in some cases to adopt the arrangement shewn in
the sectional view Fig. 9, Sheet II., where the row of fluo tubes D' have inserted in
them air tubes F, which extend from the tube plate of the combustion chamber
through the flue tubes and through the smoke box. These tubes will be open at
both ends, and will be held centrally or otherwise in their containing tubes by
feathers or their equivalent, as will be hereafter explained.
As a modification of the air tubes,, Figs. 1 and 6, we propose in some cases to
replace the uppermost horizontal row of flue tubes by a row of small air tubes
extending from the combustion chamber to the end plate of the smoke box, as
shown at Figs. Go and 6b, Sheet III. These air tubes should be equal in their total
area to the tubes which they replace.
This modification can however only be adopted when constructing new boilers.
Fig. 10, Sheet III., shews in longitudinal section a marine boiler fitted with our
improved arrangement of air supply tubes. The flame and heated gases from
the furnace A pass over bridges B, into the combustion chamber C, and by the
return tubes D to the smoke box E.
Through any selected number of these tubes D, air tubes F pass, extending as
before through the smoke box and torminating at or near the tube plate of the
combustion chamber.
For the purpose of securing a central position for the air tubes F in the flue
tubes D, they may be furnished with feathers, as before mentioned and clearly
illustrated by the enlarged views Fig. 11, Sheet II., or they may be furnished with
helical scrapers at their free ends, as shewn at Fig 12, which arrangement has this
advantage that by drawing out the air tubes, the flue tubes will be cleared of any
deposit they may contain:
Figures 13 shew an arrangement for ensuring the better mingling of the air and
gases in the combustion chamber. To the inner or free end of the air tube is fitted
a conical plug f' furnished with feathers, which will leave passages for the
outcoming air. This cone will cause the air to be deflected in the form of a
funnel shaped jet from each tube. The tube may also be pierced laterally to
deliver streams of air into the surrounding flue tube, this also is illustrated in the
Figures.
Fig. 14, Sheet III., shews in section a vertical tubular boiler fitted with air
supply tubes according to our Invention. These air tubes are shewn as inserted in
the outer ring of fire tubes only, but they may if thought desirable be applied to
other of the fire tubes.
These air tubes F pass down through the smoke box to the tube plate of the
furnace and supply, as in the previously described arrangements, streams of heated
air to the furnace.
It will be understood that the vertical boiler may be fitted with the short air
tubes, as described with reference to Figures 1 and 6, the supply of air being
controlled by regulating covers f.
Having now set forth the nature of our Invention of "Improvements in the
Construction of Tubular Boilers and Furnaces," and explained the manner of
carrying the same into effect, we wish it to be understood that we do not claim as
of our Invention the admission of streams of heated air to the combustion chamber
rrespective of the means employed for heating such air and conducting it to the
combustion chamber, but what we claim under the above in part recited Letters
Patent is,
First. The application to the furnaces of portable and locomotive engine boilers
of the raised bridge, constructed as and for the purpose above described.
Secondly. In combination with the raised bridge of portable and locomotive
ngine boilers, the means above described for causing streams of heated' air to meet

page_text: and mingle with the flame and gases of combustion as they rise over the bridge to
reach the combustion chamber.
Thirdly. The means above described with reference to the accompanying
Drawings for supplying heated air to the combustion chambers of tubular
boilers.
In witness whereof, we, the said Richard Garrett and Frank Garrett, have·
hereunto set our hands and seals, the Eighth day of September, in the year
of our Lord One thousand eight hundred and eighty one.
RICHARD GARRETT
(L.)