IMPROVED SAFETY ALARM APPARATUS FOR STEAM BOILERS OR GENERATORS
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by Ernest de Pass at the Office of the
Commissioners of Patents on the 16th October 1880. A communication from
abroad by Louis Alexandre Guibert, of 1, Boulevart Saint-Denis, Paris, France,
Engineer.
ERNEST DE PASS, of the Office for British and Foreign Patents, 68, Fleet Street,
in the City of London, Patent Agent. "IMPROVED SAFETY ALARM APPARATUS
FOR STEAM BOILERS OR GENERATORS."
A communication from abroad by Louis
Alexandre Guibert, of 1, Boulevart Saint-Denis, Paris, France, Engineer.
This Invention has for its object to provide apparatus which will give an
audible signal when the water level in a steam boiler or generator falls below a
predetermined point, and a modification thereof will also serve for providing an
exit for any surplus of feed-water introduced into such boiler or generator.
The Invention is based upon the law of physics, that in a vessel containing a
liquid the pressure upon its walls at any point is in inverse ratio to the height
of the liquid therein.
This law is utilized for the purposes of this Invention by the apparatus
hereinafter described.
Upon a steam boiler or generator and fixed vertically is a box or chamber closed
by a lid, and divided inwardly into two separate compartments by means of a flexible
diaphragm made of india-rubber, copper, or other suitable material. One com-
partiment is provided with a passage for the steam, and from the other compartment
a tube or pipe leads to the water in the boiler. This latter compartment being
filled with water there is less pressure upon the diaphragm in it than in the
compartment first herein mentioned, which is filled with steam. To the centre of
the diaphragm is attached the stem of a valve, which serves to operate a whistle
mounted in the lid or at any suitable part of the box. In this arrangement the
action is as follows:-Whilst the tube of the water compartment is immersed in
the water contained in the boiler or generator, the pressure in this compartment
is less than that in the steam compartment, and the diaphragm presses the valve
against its seat, but as soon as the water level falls below the end of the tube,
herein before referred to, the water in the water-chamber flows into the boiler and
is replaced by steam, and equilibrium of pressure on the two sides of the diaphragm
is produced, the valve which is no longer pressed home upon its seat recedes
therefrom and the whistle sounds.

page_text: As soon as the water rises sufficiently to immerse the tube of the water-
compartment this latter is filled with water, the equilibrium is disturbed, and the
diaphragin in bending forces the valve to close and the whistling ceases.
The same apparatus can be used for preventing an excessive introduction of
water into the boiler, and for this purpose the passage of the steam compartment
is extended to the highest point which the level is to reach; when the water
rises to this latter point it fills the steam compartment and consequently diminishes
the pressure upon the diaphragm; the water compartment being also full of water
equilibrium is established between the two sides, but pressure is diminished on the
side of the whistle to the extent of the difference of pressure in the boiler and that
of the atmosphere on the closing section. This difference of pressure and the
natural springiness of the diaphragm cause the valve to open, and the water
escapes with little noise, but forcibly, till the level falls below the steam passage.
By a slight modification the apparatus can be caused to sound the whistle when
the feed is excessive. For this purpose the tube of the water-compartment is just
above the normal water level, and the steam passage flush with the boilor.
When the two compartments contain steam only the two faces of the diaphragm
are in equilibrium, and the valve is forced on to its seat by the steam and by the
diaphragm and cuts off all communication, but when the level rises sufficiently to
reach the tube the water-compartment is filled with water and the equilibrium is
destroyed; the valve forced by the diaphragm opens and allows the steam to pass
to the whistle.
The two arrangements of apparatus, above set forth, may be combined so that
one portion of the combined apparatus serves for indicating low water, and the
other over-feed. One steam passage may be common to both whistles which may
have different sounds.
These apparatus need not be placed vertically on the boilers or generators, and
provided that the tubes are arranged substantially in the manner above stated,
the working is assured; they can also be constructed with inclined or horizontal
diaphragms.
The water or steam escaping through the valve, as the case may be, can be
directed on to the fire or employed for other purposes.
These diaphragms can be employed as a substitute for the ordinary floats now
in use for working valves or slides, or for other like purposes.