IMPROVEMENTS IN THE FUSIBLE PLUGS AND FURNACES OF STEAM BOILERS
Year: 1856

page_text: LETTERS PATENT to James Mash, of the City of Manchester, in the
County of Lancashire, Engineer, for the Invention of "IMPROVEMENTS IN
THE FUSIBLE PLUGS AND FURNACES OF STEAM BOILERS."
Sealed the 10th October 1856, and dated the 12th April 1856.
PROVISIONAL SPECIFICATION left by the said James Mash at the
Office of the Commissioners of Patents, with his Petition, on the
12th April 1856.
I, JAMES MASH, of the City of Manchester, in the County of Lancaster,
Engineer, do hereby declare the nature of the said Invention for IMPROVE-
MENTS. IN THE FUSIBLE PLUGS AND FURNACES OF STEAM BOILERS, to be as
follows:-
Upon any convenient part of each steam boiler where it or they may be
opposed to the action of the flame or heat from the furnace or furnaces I
attach a cap or caps of any description of metal or material, and perforated
with holes or apertures conical towards the interior of the boiler, these per-
forations being filled with metal or alloy of metals fusible at a degree of
temperature equal to or a little above that due to the extreme pressure of the
steam to which it is intended the boiler, may at at any time be subjected, and
so arranged, that during the ordinary working of the boiler the cap or caps
shall be covered by the water; but upon the quantity of water in the boiler

page_text: diminishing so as to uncover the cap or caps, or the pressure of the steam
increasing to the limit assigned, then the more fusible metal or alloy of metals
in the holes of the cap or caps will become softened or fused, and be driven
out, and permit the escape of steam and water. I also fix sometimes a cap or
caps on the top of the boiler, and subject to the action of the steam, for the
same result, from the increased pressure of the steam to the limit assigned.
In the fire-places of steam boilers I employ slabs formed of fire clay or other
suitable material in place of the ordinary fire bars; these are arranged in short
lengths, and are mounted so that the fronts of them are capable of being
elevated, or depressed by being attached by levers to a rod passing along
the ash-pit. In front of each slab is a vertical grating or bars, so as to allow
air to their upper surface when the slabs are depressed, and effect the com-
bustion of the fuel upon them; the amount of air admitted is regulated by the
amount of depression of the slabs. The fire is fed from the door in the usual
manner.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said James Mash in the Great Seal Patent Office on the
11th October 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JAMES
MASH, of the City of Manchester, in the County of Lancaster, Engineer,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twelvth day of April, in the year of our Lord
One thousand eight hundred and fifty-six, in the nineteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said James Mash, Her special license that I, the said James Mash, my
executors, administrators, and assigns, or such others as I, the said James
Mash, 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 Channel
Islands, and Isle of Man, an Invention for IMPROVEMENTS IN THE FUSIBLE
PLUGS AND FURNACES OF STEAM BOLLERS, upon the condition (amongst others)
that I, the said James Mash, 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 performed, and cause the

page_text: .
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 James Mash, 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,
reference being had to the Drawings hereunto annexed, that is to say:-
The first of my improvements relate to the application to steam boilers of
what are termed fusible plugs or plates, that is, of simple metals or of alloys
of metals which are more readily fusible than the materials of which the
boilers themselves are composed, and are applied for the preventing explosion,
or ruptures of or injury to such boilers.
Simple metals or alloys of metals have hitherto been applied to steam
boilers in various ways, intended to act or operate by melting or fusing when
the water in the boilers shall have been, from whatever cause, diminished in
quantities, so as to leave them uncovered by it.
.
Now, lead and tin, which are the metals usually employed for this purpose,
do not fuse or melt untill high temperatures are attained; lead, under
ordinary circumstances, requiring above 600°, and tin about 440° tempe-
ratures, corresponding to pressures of steam very considerably above tho
maximan strength of boilers generally.
It has been found, that with regard to the fusing or melting of alloys of
metals, when subjected to the pressure of steam in the ordinary manner, that
compressive action takes place, the effect of which is, that as the temperature
increases, fusing of some portions of the component parts of the alloys takes
place, which fused portions are squeezed or forced out in a fluid state, leaving
as residues alloys differing in proportions of the component parts from the
original alloys, and fusible only at higher temperatures than were the original
alloys. If, however, the temperatures continue to increase, then 'continued
fusing of portions and continued squeezing and forcing actions follow, untill
at length the least fusible metals of the alloys alone or slightly alloyed remain,
and which are fusible only at high degrees of temperatures.
.
Also, with regard to plugs or plates of simple metals, the compressive action
before spoken of takes place, and a portion only of each is forced out, forming
a small aperture, through which the steam and water blows, the other portions
remaining in a solid state.
My present improvements, with a view to remedy these imperfections,
consists in applying the more fusible simple metals and alloys of metals in such
manners as to be subjected to little or no compressive action, so that upon'
their assuming softened or imperfectly fused states they shall be wholly forced

page_text: .
away by the pressure of steam; and with regard to alloys, retaining always
wholly, or nearly so, the original proportions of component parts of such
alloys; and this I effect by applying the more fusible simple metals and alloys
of metals of conical, or of taper, or of pyrimidal, or of other unequal forms,
so arranged that the pressure of the steam, or of the water to which they may
be subjected, acts against or upon the smaller ends or areas thereof.
I will now illustrate by the accompanying Drawing the adaptation of this
part of my improvements to a steam boiler having an internal flue.
First, as applied to the internal flue, and below the ordinary working level
of the water, as shown at A, and operating principally as a preventive of
danger, arising from deficiency of water; and when alloys are employed as a
preventive of danger, arising from undue increase of temperature of the water,
as upon deficiency of water taking place, and their becoming uncovered by it,
the temperature will be raised, and softening or imperfectly fusing them suffi-
ciently to be wholly forced or driven out by the pressure of steam; and the
same action would take place upon increase of temperature of the water
(without its being deficient & below its ordinary level) beyond that cor-
responding to the maximum pressure of steam, to which the boiler is intended
to be limitted.
Second, as applied to the top of the boiler or other part where exposed to
the action of the steam, as shown at B, and employing alloys of metals only,
and here operating as a preventive of danger from increase of temperature,
corresponding to the maximam pressure of steam to which the boiler is
intended to be subjected.
The manners of application, as here shown, are by means of caps into conical
perforations or holes in which the metal or alloy is inserted; but though I
prefer this mode generally, any other convenient means may be adopted, as
shown at C, where the alloy is contained within perforations or holes in the lid
of an ordinary safety valve, thereby rendering harmless any derangenent of
or any overloading or tampering with it. Or, each plug or mass of metal, or
alloy of metals, may be contained within any ordinary plug or piece to be
screwed or otherwise secured to any part of a steam boiler, or to any append-
ages of a steam boiler, as shown at D, where the plug or piece containing
the metal or alloy is shown screwed into a plate of a steam boiler, or merely
driven in.
I prefer generally that the metals or the alloys of metals employed be
caused to adhere to the surface of the perforations or holes into which they
are inserted; but other means of securing them may be employed, as, for
example, in some case, simply driving them in may be adopted.

page_text: In the application of my improvements, I prefer so to proportion the
component parts of the alloys that the temperatures at which they will be
effectively acted upon be at or about that corresponding to the maximan
pressure of steam which it may be intended shall be the limit in their respec-
tive boilers.
The second part of my Invention relates to the construction or arrangement
of the furnace or fire-places of steam boilers, and their mode of action or
operation. The accompanying Drawing also illustrates this part of my Inven-
tion, as shown at E. The bed of the furnace or fire-place I form of slabs or
pieces a, a, in place of the ordinary fire bars; upon these the fuel is placed,
and the combustion is effected; they are mounted in frames of iron or other-
wise, so that pivots or bearings upon their ends move in bushes or holes in
bars, or frames, or other fixtures b at the sides of the furnace or fire-places,
and they are capable of being moved so that they (the slabs) may be varied in
the positions to any desired degree of inclination. They are connected by
levers c, c, to the rods d, which is attached to the bell-crank e; this is weighted
by a counterweight to the slabs; there is an arc f in connection, by which the
slabs may be fixed in any desired position, as they may be raised to form one
continuous right line surface, as shown by the dotted lines, or depressed, to
assume nearly vertical positions. In front of each slab a grating or bars or
openings are arranged for the admission of air to the fuel. The fuel may be
charged in the usual manner or otherwise, when the slabs are elevated, as
most convenient, or when in any other positions. The quantities of air
admitted through the gratings or other openings may be regulated according
to circumstances, simply by elevating or depressing the slabs; they also act as
dampers in the same manner by partially or wholly raising them. When it
is requisite to clear the slabs from dust or other matters, then the slabs may
be wholly depressed, so that every thing on them will be passed into the ash-
pit. By connection with any self-acting apparatus the admission of air to
the furnace or fire-place may be self-regulating.
In witness whereof, I, the said James Mash, have hereunto set my
hand and seal, this Eighth day of October, in the year of our Lord
JAMES MASH, (L.S.)