Improvements in FUSIDIC rings тот Heaters, and other Appliances Connected with Steam Boilers.
Year: 1887

page_text: Improvements in FUSIDIC rings
тот
Heaters, and other Appliances Connected with Steam Boilers.
I, WILLIAM WILLIAMS, of 26 McKerrell Road, Peckham, in the County of Surrey,
Engineer and boiler inspector do hereby declare the nature of this invention to be as
follows:-
1
This invention relates to improvements in fusible plugs for preventing damage to
steam boilers to the furnace tubes or flues thereof, or to feed water heaters by over
heating of the plates or other material of which they are composed from shortness of
water, excessive deposit of scale or grease, or from other similar cause; or for putting
in action low water alarm apparatus or other appliances in connection with steam
boilers, and the said improvements consist as follows :-
I construct the body of the plug of a truncated, conical, dome or other suitable
shape, preferably of gun metal, and adapted to screw into a hole in the plate or other
material to which is desired to prevent damage, and I form a hole of suitable size
in the upper part of the said body with a hollow groove or seat round the edge of the
said hole. In this hollow groove or seat I place a loose ring of the usual fusible
alloy of lead, tin and bismuth of circular or other suitable section, and over the said
fusible ring I place a central plug or disc of gun metal or other suitable material the
edge of which is turned conical or to a hollow curved section to fit the upper side of
the fusible ring more or less accurately. The diameter of the said plug or disc is by
preference made somewhat less than that of the hole in the body of the plug. The
aforesaid central plug or disc is pressed against the fusible ring and the latter against
the seat in the edge of the hole in the body so as to make steam tight joints by means
of a pressure screw carried in a clamp piece or bow screwed or otherwise secured to
the body of the plug

page_text: It will now be understood that in the event of the level of the water falling below
that of the fusible ring, or in the event of an excessive deposit of scale or grease
forming on the plate or body to which the plug is attached the consequent overheating
of the fusible ring will cause the same to melt and to liberate the central plug or disc.
The pressure of the steam will then force the said plug or disc through the hole in the
body, and the steam will be free to escape into the furnace or elsewhere as the case
may be before material damage is done to the plates to which the plug is attached.
By the above described arrangements the fusible metal is brought more fully and
certainly into contact with the water in the boiler than in the arrangements at present
in use so that the premature melting of the fusible metal by the hot gases from the
fire is prevented. The form of the body and central disc is such as is least likely to
accumulate scale on the water side, or tarry deposits on the fire side-but in the
improbable event of any such scale or deposit forming thereon the area of the central
disc is sufficiently large to enable the steam (in case of overheating of the plate to
which the plug is attached-and consequent melting of the fusible ring) to break
through even a comparatively thick deposit with certainty. The fusible ring being
separate from the body and from the central plug or disc, duplicates can be kept in
stock, and a fresh one applied when necessary by simply placing it in the hollow
groove or seat of the body, then placing the recoverable central plug or disc over it
and tightening up the pressure screw in the cramp.
It is obvious that similar arrangements may be employed for low water alarm
apparatus or to any appliances in connection with a steam boiler where a certain
effect is produced, or allowed to be produced by the fusion of a metallic alloy by the
increase of its temperature beyond a certain point.
Dated this Fourth day of March 1887.
W. WILLIAMS.
Per W. H. Beck,
115, Cannon Street, London,
Agent.

page_text: Heaters, and other Appliances Connected with Steam Boilers.
I, WILLIAM WILLIAMS, of 26 McKerrell Road, Peckham, in the County of Surrey,
Engineer and Boiler inspector do hereby declare the nature of this 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 accompanying two
sheets of Drawings and to the letters and figures marked thereon, that is to say :-
This invention relates to improvements in fusible plugs for preventing damage to
steam boilers, to the furnace tubes or flues thereof, or to feed water heaters, by
overheating of the plates or other material of which they are composed, from shortness
of water, excessive deposit of scale or grease, or from other similar cause; or for
putting in action low water alarm apparatus or other appliances in connection with
steam boilers, and in order that my said improvements may be fully understood
I will now proceed to describe the same by the help of the accompanying Drawings,
in which Figure 1 is an elevation of a plug constructed in accordance with my
invention in a form suitable for use in the furnace or flue tube of an ordinary Cornish
or Lancashire boiler for example, Figure 2 is a sectional elevation of same taken on
line X-X of Figure 1, and Figure 3 a plan of same.
I construct the body or casing A of the plug, of the usual truncated conical dome,
or other suitable shape, preferably of gun metal, and adapted to screw by the screw
thread B, into a hole in the plate or other material to which it is desired to prevent
damage, and I form a hole C of suitable size in the upper part of the said body A
with a hollow groove or other suitably shaped seat D round the edge or margin of
the said hole. In this hollow groove or seat I place a loose or independent ring E of
the usual or any suitable fusible metallic alloy of circular or other suitable section,
and over the said loose fusible ring EI place a loose or independent central con-
ducting plug or disc F of copper, gunmetal, or other suitable material the edge of
which is turned conical or to a hollow curved section to fit the upper side of the
fusible ring E more or less accurately. The diameter of the said conducting plug or
disc F is made by preference somewhat less than that of the hole C in the body A of
the plug. The aforesaid central conducting plug or disc F is pressed against the
fusible ring E, and the latter against the seat D in, or on the edge of the hole C in
the body A, so as to make steam tight joints, by means of a pressure screw G, carried
in a clamp piece or bow H screwed or otherwise secured to the body A of the plug.
It will now be understood that in the event of the level of the water falling below
that of the fusible ring E, or in the event of an excessive deposit of scale or grease
forming on the plate or body to which the plug is attached, the consequent over-
heating of the fusible ring E will cause the same to melt and to liberate the central

page_text: conducting plug or disc F. The pressure of the steam will then force the said plug
or disc through the hole in the body A, and the steam will be free to escape into the
furnace, or elsewhere as the case may be, before material damage is done to the plate
to which the plug is attached.
The
arrangement shown in Figures 1, 2 and 3 is suitable for use in cases where
ready access can be had for screwing the body A into position from the water side of
the plate it is desired to protect, but there are cases where such ready access cannot
be had or where for other reasons it may be desired to screw the plug into position
from the side of the plate opposite to that at which the water is situated as for instance
in the crowns of Locomotive or Portable Engine Boilers where it often happens that
there is no manhole or handhole in a position suitable for enabling the plug to be
inserted and screwed into its place from the water side of the plate. In such cases
I employ modified forms and arrangements adapted to be screwed into position from
the side of the plate to be protected opposite to that where the water is situated.
Figure 4 is a sectional elevation of a plug so adapted. In this case the upper part of
the body or casing A and the clamp piece or bow H screwed on it are made sufficiently
small to admit of their being passed up from the under side through the tapped hole
in the plate I, the body A being screwed by the thread B into such hole by means of
a key applied to the lower end A¹ of the body A which is made square or hexagonal
for that purpose. The loose conducting plug F, the fusible loose ring E, and the
seat D are shown conical in this Figure, but it is obvious that they may be made if
preferred in the manner shown in Figure 2.
Figure 5 shows a plug similar to that shown in Figure 4 but without the clamp
piece or bow H and intended, like that shown in Figure 4, to be inserted from the
side of the plate opposite to that where the water or the pressure of steam exists. In
this case the fusible ring E is first placed on the seating D and the conducting plug F
is merely driven more or less tightly into the fusible ring E by a mallet or otherwise
before the body A is screwed into the plate I. Figure 6 is a plan of the arrangement
shown in Figure 5 and Figure 7 is an underside view of same when screwed into the
plate I.
Similar letters of reference relate to like parts in all the Figures of the Drawings.
By the above described arrangements the fusible metal is brought more fully and
certainly into contact with the water in the boiler than in the arrangements at present
in use, so that the premature melting of the fusible metal by the hot gases from the
fire is prevented. The form of the body and central disc is such as is least likely to
lead to the accumulation of scale on the water side, or of tarry deposits on the fire
side, but in the improbable event of any such scale or deposit forming over the plug F
and fusible ring E the area of the central disc is sufficiently large to enable the steam
(in case of overheating of the plate to which the plug is attached, and consequent
melting of the fusible ring) to break through even a comparatively thick deposit with
certainty. The fusible ring E and the copper or gun metal conducting plug or
disc F being separate from each other and from the body A duplicates of such
rings E and plugs or discs F can be kept in stock, and fresh ones applied, when
necessary by simply placing the loose ring E in the hollow groove or conical seat as
the case may be of the body, then placing over it the loose central plug or disc F
(which may be either a fresh one or one recovered from the furnace or other place to
which it may have been forced by the escaping steam on the melting of the fusible
ring previously used) and finally tightening up the pressure screw G in the clamp
piece or bow H. Instead of the clamp piece or bow and pressure screw for holding
the plug F in place a cottar passing through slots in suitable standards formed on or
secured to the body A may be employed but I prefer the pressure screw and clamp
as shown in Figures 1, 2 and 3 as its pressure acts more nearly perpendicular to the
surface of the plug or disc F than a cottar because the latter being driven in sidewise
has a tendency to tilt the plug or disc to one side and thereby to cause it to bear
harder on one side of the ring E than on the other.
It is obvious that similar arrangements may be employed for low water alarm

page_text: apparatus or to any appliances in connection with a steam boiler where a certain
effect is produced, or is allowed to be produced by the fusion of a metallic alloy
consequent upon the increase of its temperature beyond a certain point.
Having now particularly described and ascertained the nature of my said invention,
and in what manner the same is to be performed I would have it understood that I am
aware that in one of the known arrangements of fusible plug the fusible metal has
been applied as a loose ferrule or thimble placed in a conical seating in the metallic
body or casing of the plug and held in place by a copper or gunmetal conducting
plug which is screwed into the top part of the said body, and that in other of the
known arrangements the fusible metal is distinct from the metallic body or casing but
is cast on to the copper or gunmetal conducting plug, and these two, thus combined
together, are held in, or on, a seating formed in, or on, the metallic body or casing by
means of a perforated cap screwed on to the top of the said body or casing and
I make no claim to such arrangements, but I declaro that what I do claim is :-
First. The improved construction of fusible plug, consisting of the body A having
a hole C through the upper part thereof with a suitably shaped seating formed round
the edge or margin of such hole, the loose or independent metallic conducting plug or
disc E, and the loose or independent ring E of fusible metal, the whole combined,
arranged, and acting as hereinbefore described, and illustrated in the Drawings hereto
annexed.
Second. In fusible plugs, the use of a loose or independent ring of fusible metallic
alloy interposed and held between the edge of a loose or independent metallic con-
ducting plug or disc, and the edge or seating of the metallic plug body, as hereinbefore
described, and illustrated in the Drawings liereto annexed.
Dated this 21st day of May A.D. 1887.
W. WILLIAMS.
Per W. H. Beck,
115, Cannon Street, London, E.C.,
Agent.