AN IMPROVEMENT IN STEAM BOILERS, WHICH IS APPLICABLE TO OTHER VESSELS FOR CONTAINING COMPRESSED AIR. VAPOUR OR GAS
Year: 1853

page_text: LETTERS PATENT to Robert Roughton, of Woolwich, in the County
of Kent, Engineer in the Royal Navy, for the Invention of "AN
IMPROVEMENT IN STEAM BOILERS, WHICH IS APPLICABLE TO OTHER
VESSELS FOR CONTAINING COMPRESSED AIR. VAPOUR OR GAS
"
Sealed the 5th May 1854; and dated the 7th November 1858.
PROVISIONAL SPECIFICATION left by the said Robert Roughton
at the Office of the Commissioners of Patents, with his Petition,
on the 7th November 1853.
I, ROBERT ROUGHTON, of Woolwich, in the County of Kent, Engi-
neer in the Royal Navy, do hereby declare the nature of the said
Invention for "AN IMPROVEMENT IN STEAM BOILERS, WHICH IS APPLICABLE.
TO OTHER VESSELS FOR CONTAINING COMPRESSED AIR VAPOUR, OR GAS," to
be as follows-
The object of my said Invention; which is applicable to any descrip- -
tion of boiler, is to prevent the internal pressure from exceeding -any:
determined limit, whereby the fearful consequences of boiler explosions
may be avoided...

page_text: The Invention consists in the addition of a dome of any suitable
form, the diameter and thickness of metal of, which are such as will
give it a strength very little exceeding that at which the boiler is
usually worked, but at the same time much less than the extreme
strength of the boiler, so that this dome will burst and relieve the boiler
whenever an undue pressure occurs. It is affixed on or connected to
the boiler in such a position as will allow the steam or other fluid, or
gas or vapour, as the case may be, to escape in such a direction that it
will not be liable to scald or otherwise injure persons who may happen
to be near.
This Invention is not intended to supersede the use of safety valves,
but to prevent the boilers from being burst whenever the safety valve
becomes inoperative by accident, or by the ignorance, neglect, or design
of those who have the care of it.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Robert Roughton in the Great Seal Patent
Office on the 6th May 1854.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
ROBERT ROUGHTON, of Woolwich, in the County of Kent, Engineer in.
the Royal Navy, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Seventh day of November, in the
year of our Lord One thousand eight hundred and fifty-three, in the
seventeenth year of Her reign, did, 'for Herself, Her heirs and succes-
sors, give and grant unto me, the said Robert Roughton, Her special
licence that I, the said Robert Roughton, my executors, adminis-
trators, and assigns, or such others as I, the said Robert Roughton,
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 might make, use, exercise,
and vend, within the United Kingdom of Great Britain and Ireland, the

page_text: Channel Islands, and Isle of Man, an Invention for "AN IMPROVEMENT
IN STEAM BOILERS, WHICH IS APPLICABLE TO OTHER VESSELS FOR CONTAINING
COMPRESSED AIR, VAPOUR, OR GAS," upon the condition (amongst others)
that I, the said Robert Roughton, by an instrument in writing under
my hand and seal, should particularly describe and ascertain the nature
of the said Invention, and in what manner the same was to be per-
formed, 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 Robert Roughton, 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 thereof, reference being had to the Drawing
hereunto annexed, that is to say:
My Invention consists in fixing upon or in connection with a steam
boiler or other vessel for containing compressed air, vapour, or gas a
circularly-forined dome or chamber of any suitable material, the
dimensions of which dome are such that it will burst and relieve the
said boiler or other vessel when any undue pressure of the steam,
vapour, or gas is produced within it either by accident or otherwise.
The accompanying Drawing represents one method of carrying my
Invention into effect. A, B, is a section of the upper part of a steam
boiler. C, is a cylinder of brass having two flanges a, b, the lower of
which a is firmly screwed down to the boiler A, B, and the upper
part of which 6 is screwed to the lower flange c of another cylinder D,
which is formed of zinc of such thickness that it will burst when the
internal pressure exceeds a definite amount. The former of these
cylinders C is 2 inches in diameter, and the latter D 4 inches. E, is
a cover or bonnet screwed down upon the upper flange d of the cylin-
der D, in such manner that when the latter bursts it may be readily
removed, and the said cover or bonnet E be immediately screwed down
upon the flange 6 of the cylinder C, in order to make the boiler
effective again until a new zinc cylinder can be conveniently applied.
The dome is to be fixed to the boiler in such position that the steam
shall be permitted to escape only in the most convenient direction, a

page_text: case or cover with an aperture in one side of it being, when necessary,
placed over it for this purpose. In locomotives the aperture of this
case or cover may be placed towards the funnel, and in steamers it may
lead into the air casing that surrounds the funnel. It would also be
advisable that the whistle in constant use in locomotives or a pipe con-
•nected to the steam gauge or water glass in steamers should communi-
cate with the apparatus described, in order to guard against the danger
of designing persons choking the passage from the boiler to the zinc
cylinder from within the boiler.
€
These safety domes may be made spherical, spheroidal, cylindrical, or
of any other circular form, but the cylindrical form previously described
will probably be found the most convenient; they may also be formed
of any suitable substance the strength of which has been ascertained.
The area of the orifice covered by a dome of the foregoing descrip-
tion must not be less than will afford sufficient escape for the steam as
may be determined by a rule to be described hereafter, but it will
generally be convenient to make the area much larger than the mini-
mum size indicated by the said rule.
.
The dimensions of the zinc or of any other corresponding cylinder
necessary to sustain a given pressure may be very readily determined.
Let the following be taken as an example:-Required the dimensions
of a safety dome for a locomotive boiler which can convert 200 cubic
feet of water per hour into steam of a pressure of 100 pounds per square
inch. Let the material be zinc, whose ultimate strength is onė ton;
or 2240 pounds per square inch of section, and let the dome be of a
cylindrical form, and one eighth of an inch in thickness. Then the
pressure that will burst this dome, supposing it to be one inch deep, will
lbs.
be 2240 × × 2 = 560 lbs.; and if we wish the dome to burst when
.the internal pressure of the steam is 140 pounds per square inch, and
not at any less pressure, (lest a small and uninjurious increase of pres-
sure above the 100 pounds should burst the dome, and thereby give
unnecessary trouble,) then = 4 inches, the required. diameter of
the cylindrical dome. This dome might be proved by actual experi-
ment to be capable of sustaining 120 pounds pressure per square inch

page_text: to ensure that it would not burst with much less than the desired
pressure.
The following is the rule herein before referred to for determining
e area of the orifice that will suffice for the escape of the steam:
area of orifice in square inches.
Let a
23
"
w
f
the number of cubic feet of water evaporated per hour.
the logarithm of the sum of the steam and atmospheric
pressures minus the logarithm of the atmospheric
pressure.
98, a number that has been determined by experiment.
is the formula required.
พ
Then a =
fc
In the example previously investigated w=200, and f = log.
(100+15) log. 1589. Therefore
W
fc
=
200
98 x 89
= 2.29 square
inches. Therefore 2 inches will fully suffice for the diameter of the
escape orifice.
And having now described the nature of my said Invention, and in
what manner the same is to be performed, I declare that I claim,-
The adaptation to steam boilers and vessels for containing com-
pressed air, vapour, or gas of a dome or chamber of any suitable
circular form and material that will guarantee a finite strength, and of
such dimensions that it will burst with a less internal pressure than the
vessel itself, and thus relieve the said vessel whenever an undue pres-
sure occurs, either from the derangement of the safety valve or from
any other cause.
In witness whereof, 1, the said Robert Roughton, have hereunto
set my hand and seal, this Sixth day of May, One thousand
eight hundred and fifty-four.
ROBERT. ROUGHTON. (L.S.)