IMPROVEMENTS IN STEAM BOILERS
Year: 1875

page_text: PROVISIONAL SPECIFICATION left by John Shaw at the Office of the
Commissioners of Patents, with his Petition, on the 1st February
1875..
I, JOHN SHAW, of The Neptune Engine Works, Low-Walker-on-
Tyne, in the County of Northumberland, do hereby declare the nature
of the said Invention for "IMPROVEMENTS IN STEAM BOILERS," to be as
follows:-.
My Invention relates to the construction and arrangement of steam
boilers so as to secure strength, to avoid the strains arising from unequal
expansion, to give facility of access for cleansing or repair, to improve
the combustion, and thereby to économise fuel, and when my Invention
is applied to marine boilers, to render the parts to be moved compara-
tively light and manageable, to provide against the lashing of the water
resulting from the motion of the vessel, and to afford means of working
with a portion of the power when the boiler may be partially disabled.
For this purpose I divide the boiler into two separate lengths, so that
cach boiler constructed according to my Invention consists of a pair
of equal and similar parts or sections, several of which pairs may be
employed when great power is required.

page_text: I will describe one such pair of sections:-Each section consists of a
casing, which may be cylindrical or may have flat sides with a round
top and bottom. In the lower part of the section is the fire-box,.or
there may be two or more fire-boxes, each being a large tube preferably
cylindrical, extending through the section from front to back. Above
the fire-box or boxes are arranged tubes also extending through the
section. The two sections are set back to back with a space between
them. The bottom of this space is preferably made in fire-brick or
refractory lumps built on a plate extending from the one section 'to the
other, and this refractory material is shaped to deflect the flame and
gases as may be found convenient. The top of the space is formed by
a fire-brick arch extending across from the one section to the other; or
instead of such arch, each of the two sections may be made to project at
its upper part, so that when the sections are placed back to back, their
upper parts meet together, while a space is left between them below.
The sides of the space are also lined with fire-brick. In this middle
space are received the products of combustion from the fires of the two
sections, which are stoked in cach case from the front. From the same
middle space the tubes convey the products of combustion in opposite
directions through the two sections to up-takes, one of which is provided
on the front of each section. Each of these up-takes may lead to a
chimney, or, by preference, one middle chimney is made to serve for
both by leading flues to it over the sections from both up-takes..
A steam receptacle, which is preferably of long cylindrical form, is
placed horizontally over the sections which communicate therewith by
pipes, and these pipes may be provided with shut-off valves, so that if
one section should be disabled it might be cut off, the other being still
worked.
It is preferred to enclose the steam receptacle wholly or partially
within the flues leading from the up-takes to the chimney so as more
freely to utilize the heat of the escaping products for drying the steam.
A convenient arrangement of such boilers as I have described for
marine purposes, is to employ two pairs of sections set side by side, with
one middle chimney to which the four up-takes are connected, and one
steam receptacle with which the four sections communicate, the receptacle
being placed in the middle over the space between the two pairs of
sections, and within the flues leading from the up-takes to the chimney.

page_text: By thus dividing the boilers into comparatively short lengths or sections,
the strains due to inequalities of expansion and contraction are in great
measure avoided and the strength is increased; also the fire-boxes and
the middle space into which they open being readily accessible from both
ends, the latter space giving access to the inner ends of the tubes,
cleansing or repair can be readily effected. Moreover, in the said middle
space, with its refractory bottom and sides heated during the working of
the boiler, the combustion of the gases from the fuel is more completely
effected before the products thereof enter the tubes, and thus there is a
diminution of smoke and of sooty deposit and a proportionate economy
of fuel.
For marine purposes each section such as I have described can be
readily moved into or out of its place without necessitating large openings
through the deck of the vessel or great lifting power, and the water
being subdivided in the sections there is a reduction of the lashing or
changes of level that result from the motion of the vessel.