Improvements in Low-water Alarm for Steam Boilers.
Year: 1890

page_text: Date of Application, 28th. Apr., 1890-Accepted, 31st May, 1890
COMPLETE SPECIFICATION.
[Communicated from abroad by ANDREW WILDMAN, of East Saginaw, in the
County of Saginaw, State of Michigan, United States of America, Boiler
Manufacturer.]
Improvements in Low-water Alarm for Steam Boilers.
I, OLIVER IMRAY of No. 28 Southampton Buildings in the County of Middlesex,
Fellow of the Institute of Patent Agents, do hereby declare the nature of the said
invention for IMPROVEMENTS IN LOW-WATER ALARM FOR STEAM-BOILERS, and in what
manner the same is to be performed, to be particularly described and ascertained by
the following statement:-
This invention relates to improvements in low-water alarms for steam-boilers of
the class in which a plug of metal fusible at the temperature of steam under pressure
is so arranged as to be exposed to a low temperature when there is a sufficiency of
water in the boiler, but to be exposed to a higher or melting temperature on the
water in the boiler being at a lower than an ordinary stage, or on the surface of the
water becoming lowered so as to approach a dangerous line.
The principal object of my invention is to arrange and construct a device for
carrying a fusible metallic plug, so that on a temporary displacement or lowering of
the water in the boiler the metallic plug will remain in a solid condition, but on a
permanent lowering of the water the plug will be removed and furnish a warning
to the operator that the water has reached a stage that requires immediate attention.
The invention consists in the construction, combination, and arrangement of the
device, as I shall hereinafter proceed to describe, and which will be particularly pointed
out in the claims of this specification.
. The invention consists, further, in the combination of the parts and in the arrange-
ment of the same, whereby the time within which the plug will be removed, after
the water in the boiler has reached a dangerous level may be regulated by the
operator.
The invention also consists in the combination and arrangements of the parts of the
device so that they may be locked in position, whereby the operator or engineer is
required to report cach time the alarm may have operated.
I illustrate my improvement in the accompanying drawing, in which the figure is
a vertical central section of my improved device as attached to a steam-boiler.
Referring to the drawing, a, represents the upper portion of the shell of a steam-
boiler, and b, are the flues.
c, is a pipe passed downward through the shell a, and is arranged with its lower
end d, reaching nearly to the flues b, or to a position below the ordinary water-level
in the boiler, while the upwardly-extending portion e, is passed through the lower
end f, of a casing 9, which incloses a chamber h, the end portion i, of the pipe,
extending nearly to the upper head j, of the casing.
k, is a pipe passed through the upper head j, and is arranged with its lower portion l,
extending downwardly beside the pipe e, and reaches nearly to the lower head f
while to the upper end of the pipe k, is connected a valve m, and to the upper part
of the valve is connected by a screw-thread a plug-holder n, baving a central tapering
opening. o, and into this opening o, is fitted a plug P, of a metal composition
which remains in the solid state when exposed to a low temperature, but which, how-
ever; will melt when exposed to the higher temperature of steam under ordinary
pressure. The pipe i, is provided near the lower head f, with an opening 9,
while the outer end of the plug is provided with a hand-wheel u, with which to turn
the plug.
v, is a pipe passed through the lower portion of the casing into the chamber and
is provided with the valve w, for blowing out the contents of the chamber whenever
required

page_text: The valve m, is provided with a valve-stem æ, which on being turned in one
direction by means of a screw-thread moves outwardly in the direction of its length
for opening the valve, but must be turned in the opposite direction and move
inwardly to close the valve; and y, is an opening through the stem, while z, is a
padlock with its U-shaped-loop passed through the opening and locked in position,
being so located in, the stem that when the lock is secured in position in the
opening it prevents the stem from moving inwardly for closing the valve.
When the device is in position for operation, the valve m, is open and the water
within the boiler under steam-pressure is forced up the pipe c, and fills the chamber
and pipe k, and comes in contact with the fusible plug, and on account of there being
comparatively little circulation through the pipe and the chamber being located away
from the boiler the water in the chamber and pipe k, remains at a sufficiently low
temperature to allow the plug to remain in a solid state; but on the water within
the boiler becoming lowered, so that the lower open end of the pipe c, is exposed to
the steam, the water within the pipe at once passes by gravity into the boiler.and
steam rushes into the pipe and equalizes the pressure therein and in the chamber;
and the water in the chamber then passes into the pipe c, through the opening 9,
and this opening being of a limited dimension, some time must clapse before tho
chamber and also the pipe k, are relieved of the water; but on the water having
passed out the steam of a high temperature rushes at once in from the pipe c, and
coming in contact with the plug and plug-holder quickly raises the temperature
thereof until the plug is fused, and the opening o, being then freed from the plug
the steam goes rushing through the opening, giving warning to the engineer, that
the water in the boiler has reached a state that requires immediate attention to prevent
accident of burning of the flues, &c.
On the fusible plug being removed, as stated, the operator must produce the key
and unlock the padlock, and turn the valve m, to close the pipe k, and the holder n,
may then be removed and a new plug placed in position and the holder then
replaced in position, and on the water in the boiler being replenished the valve m,
is opened and locked in position.
It will be observed that a considerable interval of time must elapse after the
steam has passed into the pipe c, before the pipe k, will be freed from the water to
admit steam to direct contact with the plug, and herein lies the gist of my invention,
as should the water in the boiler be temporarily displaced by foaming or otherwise,
to admit steam to the pipe c, and again return before the water in the chamber
has had time to pass out through the opening 9, the pipe will again fill with
water and the fusible plug will remain solid, so that only a permanent lowering of
the water-surface in the boiler can remove the plug. It will also be noticed that
by means of the screw-plug p, the area of the opening q, may be regulated to allow
more or less time, as may be desired, for the water in the chamber to pass out, the
plug being turned so as to place the end t, in position to partly close the full
opening, so that a considerable interval of time will elapse between the filling of the
pipe c, with steam and the exposure of the fusible-metal plug to the temperature
of the steam, so that the operator is sure that when the fusible plug has been
melted out the water in the boiler is in a condition that requires immediate attention,
and the valve m, being locked the operator must obtain a proper key to unlock the
valve before the issue of steam through the opening o, can be stopped, and this
key may be placed in the office of a manufactory, so that the workman in charge
of the boiler must report at the office that he has allowed the water in the boiler to
reach a stage lower than was entirely safe or proper.
The pipe v, is used to blow out the contents of the chamber from time to time to
remove any sediment therefrom and to keep the pipes free and open.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is-
1. In a low-water alarm, the combination of a casing a. inclosing a chamber

page_text: above the boiler, and a pipe c, with its upper end portion i, passed through the
said casing and extending to the upper portion of the chamber and provided with
an opening, as q, and having its lower portion d, passed through the boiler-shell and
reaching into the water, and a pipe k, having its lower end portion 1, passed through
the upper head of the said casing and extending to the bottom portion of the
chamber, and having, as described, its upper end opening closed with a plug of
metal fusible at the temperature of the steam in the boiler, substantially as
set forth.
2. The combination, in a low-water alarm, of the casing inclosing a chamber,
with the upper and lower vertical pipes having their adjacent end portions passed
through the opposite heads of the said casing and over-lapping each other, and with
the lower portion of the lower pipes passed through the boiler-shell and reaching
into the water, a valve secured to the upper end of the said upper pipe and provided
with devices, as described, for locking the valve in an open position, and a plug of
metal, fusible at the temperature of steam in the boiler, for closing the end opening
of said upper pipe, substantially as set forth.
3. The combination, in a low-water alarm, of a casing inclosing a chamber, a pipe
passed through the lower head of the casing and with its upper end portion
extending into the said chamber and provided with a side opening, as q, and with its
lower end passed through the boiler-shell and into the water, a pipe connected to the
upper head of the casing and with its lower end portion extending into the chamber
and having the opening in its upper end closed by a fusible plug, as described, and
the screw-threaded pluger, passed through the said casing, and with its inner end f,
fitted to pass into and partially close the said opening q, substantially as and for the
purpose set forth.
Dated this 28th day of Anril 1800
ABEL & IMRAY,
Agents for the Applicant.