IMPROVE- MENTS IN STEAM BOILERS
Year: 1874

page_text: LETTERS PATENT to William Macnab, of Greenock, in the County of
Renfrew, North Britain, Engineer, for the Invention of "IMPROVE-
MENTS IN STEAM BOILERS."
Sealed the 30th June 1874, and dated the 9th January 1874.
PROVISIONAL SPECIFICATION left by the said William Macnab at
the Office of the Commissioners of Patents, with his Petition, on
the 9th January 1874.
I, WILLIAM MACNAB, of Greenock, in the County of Renfrew, North
Britain, Engineer, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN STEAM BOILERS," to be as follows, that is to say:
This Invention has for its object to secure efficiency in steam boilers
with simplicity of construction, durability, safety, and facility for
cleaning and repairs, the improved boilers being more especially,
although not exclusively designed for marine purposes.
In one modification the improved boiler comprises six horizontal
cylindrical shells arranged in two horizontal rows of three each, whilst

page_text: each cylinder of the upper row is connected to the cylinder beneath it
by three or more short vertical tubes of a large enough size to admit a
man through them, access being got to the interiors by man-holes in the
upper cylinders. The lower cylinders have also connected to them at
their under sides tubular legs, those of the several cylinders being con-
nected by transverse tubes at the bottom. The lower cylinders are fitted
with flue tubes, which are arranged so as to leave a space along the
middle of each cylinder for admitting a man to easily examine and clean
any part. The water level is arranged a little below the centre line of
the upper cylinders, the steam being taken from the middle cylinder, to
which the other two are connected by several pipes. The furnaces are
arranged at one end of the lower cylinders, and the fire gases pass thence
along under the lower cylinders to their back ends, whence they return.
through the tubes in the lower cylinders to the front ends, next travelling
toward the back end between the lower and upper cylinders.
Where a comparatively small boiler is required the arrangement may
be modified by combining two of the lower cylinders, having flue tubes
through them with two upper cylinders or with a single upper cylinder.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Macnab in the Great Seal Patent
Office on the 8th July 1874.
.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
MACNAB, of Greenock, in the County of Renfrew, North Britain,
Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Ninth day of January, in the year
of our Lord One thousand eight hundred and seventy-four, in the
thirty-seventh year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said William Macnab, Her
special licence, that I, the said William Macnab, my executors,"
administrators, and assigns, or such others as I, the said William
Macnab, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time, and at all times
thereafter during the term therein expressed, should and lawfully

page_text: might make, use, exercise, and vend, within the United Kingdom of
Great Britain and Ireland, the Channel Islands, and Isle of Man, an
Invention for "IMPROVEMENTS IN STEAM BOILERS," upon the condition
(amongst others) that I, the said William Macnab, my executors or
administrators, by an instrument in writing under my, or their, or one
of their hands and seals, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be
performed, and cause the same to be filed in the Great Seal Patent
Office within six calendar months next, and immediately after the date
of the said Letters Patent.
NOW KNOW YE, that I, the said William Macnab, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement in writing, reference being had to the accompanying
Drawings, that is to say :-.
My said Invention has for its object to secure efficiency in steam
boilers with simplicity of construction, durability, safety, and facility
for cleaning and repairs, the improved boilers being more especially,
although not exclusively designed for marine purposes.
And in order that my said Invention and the manner of performing
the same may be properly understood I hereunto append two Sheets of
explanatory Drawings, to be herein-after referred to, and representing
two modifications of marine boilers as made with my improvements.
In these Drawings the same reference numerals are used to mark the
5 same or like parts wherever they are repeated.
One modification of my improved boiler is shown on Sheet 1 of the
Drawings, Figure 1 being a sectional end elevation and Figure 2 a longi-
tudinal vertical section. In this modification there are six horizontal
cylindrical shells, 1, 2, 3, 4, 5, 6, arranged in two horizontal rows of three
) each, whilst each cylinder 1, 2, 3, of the upper row is connected to the
cylinder 4, 5, 6, beneath it by two short vertical tubes 7, 8, allowing of
the circulation of the water, and made of a large enough size to admit
a man through them, access being got to the interiors by man-holes in
the upper cylinders 1, 2, 3. When the cylinders are of the compara..
5tively moderate length shown the two vertical connections 7, 8, between
each pair are sufficient, but with longer cylinders there may be three or
even more of such connections. The lower cylinders 4, 5, 6, have also.

page_text: connected to them at their under sides tubular legs 9 situated at the
inner ends of the cylinders, and those of the several cylinders being
connected by a transverse horizontal tube 10 at the bottom. These
tubes 9, 10, are made sufficiently large to admit a man for inspecting
and cleaning purposes. At the bottom of the front end of each lower
cylinder 4, 5, 6, there is formed a short tubular extension 23, which
projecting forward serves for supporting the cylinder, and the front end
of which is intended to be fitted with a small door for inspection or for
introducing a cleaning instrument. Longitudinal flue tubes 11 are fixed
in the lower cylinders 4, 5, 6, and are by preference arranged so as to
leave a space 12 along the middle of each cylinder for admitting a man
to casily examine and clean any part. The tubes 11 may be either
larger and fewer or smaller and more numerous than those shown in
Figures 1 and 2.
The water level is arranged a little below the centre
line of the outer upper cylinders 1, 3, the steam being taken from the
middle cylinder 2, the diameter of which is greater and which also is
placed higher to give a larger steam space, the other two 1, 3, being
connected to it by pipes 13. The furnace 14 is arranged at one end of
the lower cylinders 4, 5, 6, and the fire gases pass thence under the
lower cylinders to their back ends by flue spaces 15, 16, represented in
the Drawing as enclosed by fire-brick 17, cased and strengthened by
iron. From the back end flue space 16 the fire gases return through
the tubes 11 in the lower cylinders 4, 5, 6, to a smoke box or flue space
18 at the front ends, and then travel towards the back ends again
between the lower cylinders 4, 5, 6, and the upper ones 1, 2, 3, finally 1
reaching the uptake 19.
Where more power is required than that for which the boiler shown
on Sheet 1 of the Drawings is suited two sets of the six-cylinder combi-
nation may be arranged either side by side or back to back in connection
with one up-take; and for still larger powers four, and in some cases 3
even six such sets may be combined. On the other hand when a
comparatively small boiler is required the arrangement may be modified
by combining two (5, 6,) of the lower cylinders having flue tubes (11)
through them with two upper cylinders (2, 3,) or with a single upper
cylinder. Intermediate sizes may be formed by doubling or quadrupling 3
the modification comprising two lower and two upper cylinders, and as
these sizes will probably be required as often as any other I show an
example on Sheet 2 of the Drawings.

page_text: Figure 3 is a sectional end elevation, and Figure 4 is a longitudinal
vertical section. In this modification the entire boiler comprises two
double divisions placed back to back, each division consisting of two
pairs of lower cylinders 5, 6, with tubes 11 through them, and connected
individually by short vertical tubes 7, 8, to two upper pairs of cylinders
2, 3, the water line being a little below the centre line of the upper
cylinders, the outer ones 2 of which are made larger than the inner ones
3, and receive the steam from the latter by pipes 13. The furnaces and
flues are arranged as herein-before described with reference to Sheet 1 of
the Drawings. Some additional heating surface is however obtained by
placing water tubes 20 transversely along the upper parts of the inner
flue spaces 16, such tubes being connected at one end by pipes 21 with
the bottom horizontal connecting tubes 10, and by other pipes 22 at the
other end with the upper cylinders 2, an arrangement which will promote
1.

page_text: together of the parts of steam boilers, substantially in the improved
manner herein described and delineated.
In witness whereof, I, the said William Macnab, have hereunto
set my hand and seal, this Sixth day of July, in the year of
our Lord One thousand eight hundred and seventy-four.
Witness,
EDMUND HUNT,
Patent Agent,
Glasgow.
WILLIAM MACNAB. (L.s.)