A NEW OR IMPROVED LOW AND HIGH WATER INDICATOR FOR STEAM BOILERS
Year: 1871

page_text: LETTERS PATENT to John Millward, of Curzon Chambers, Paradise
Street, Birmingham, in the County of Warwick, Civil Engineer,
for the Invention of "A NEW OR IMPROVED LOW AND HIGH WATER
INDICATOR FOR STEAM BOILERS."-A communication from abroad by
Frank Millward, of Cincinnati, in the County of Hamilton, State of
Ohio, United States of America.
Sealed the 5th December 1871, and dated the 7th June 1871.
PROVISIONAL SPECIFICATION left by the said John Millward at
the Office of the Commissioners of Patents, with his Petition, on
the 7th June 1871.
I, JOHN MILLWARD, of Curzon Chambers, Paradise Street, Bir-
mingham, in the County of Warwick, Civil Engineer, do hereby declare
the nature of the said Invention for "A NEW OR IMPROVED LOW AND HIGH
WATER INDICATOR FOR STEAM BOILERS," to be as follows:-
PROVISIONAL SPECIFICATION left by the said John Millward at
the Office of the Commissioners of Patents, with his Petition, on
the 7th June 1871.
I, JOHN MILLWARD, of Curzon Chambers, Paradise Street, Bir-
mingham, in the County of Warwick, Civil Engineer, do hereby declare
the nature of the said Invention for "A NEW OR IMPROVED LOW AND HIGH
WATER INDICATOR FOR STEAM BOILERS," to be as follows:-
The object of this Invention is to obviate the difficulties hitherto
experienced in the operation of indicators arising from incrustation,

page_text: friction, and other causes, and to provide an indicator which operates
with certainty and precision under all conditions of boiler pressure, is free
from incrustation, and has no rubbing or moving parts liable to stick.
A low water indicator constructed in accordance with this Invention,
consists of a closed metallic case divided into two separate and steam- 5
tight chambers or compartments by an elastic or flexible diaphragm of
corrugated sheet metal or other equivalent affixed therein, and the said
metallic case is supported outside the steam boiler, to which it is
attached at a suitable distance above the water level thereof.
One compartment or division of the said case is made to communicate 1
with the steam space of the said boiler by means of a suitable pipe or
duct, and the other compartment or division communicates with the
water space of the boiler by a separate dip pipe or suitable duct opening
into the boiler at the low water or danger level, both compartments of
the case being thus under pressure.
1
The steam compartment is provided with an alarm vent, which is
opened or closed by a valve operated by a simple and direct connection
with the diaphragm. When the water in the boiler is at its proper
working level the compartment in connection with the water space and
its connecting pipe are kept filled with water by the pressure of steam 2
in the boiler, and the pressure per square inch upon the water side of
the diaphragm is less than that of the steam by the amount of pressure
'necessary to support the hydrostatic column reaching up to the case,
while the pressure on the steam side of the diaphragm is practically
the same as in the boiler, and this preponderance deflects the elastic 2
diaphragm, and keeps the alarm valve closed. But as soon as the water
in the boiler sinks below the dip pipe or lower duct this and the com-
partment with which it communicates empty into the boiler and become
filled with steam, and the pressure on both sides of the diaphragm being
equalized the elasticity and retractile force of the diaphragm at once 3
opens the valve governing the alarm vent, to which may be attached the
usual alarm whistle.
The diaphragm valve and' seat may be plated with nickel or otherwise
protected to prevent corrosion, and as the water never enters the valve
side of the instrument no incrustation can take place, and great 3
durability and freedom of motion are secured. A. cock may be fixed
to that compartment of the case in connection with the water space
to empty it of air when the boiler furnace is first lighted, but this is

page_text: not a necessity as the air is condensed into a very small space by the
pressure of steam and is soon absorbed.
This indicator is applicable as a high water indicator by simply con-
structing the alarm valve so as to cause it to be opened by the deflection
of the diaphragm (or the central part of the diaphragm may itself be
made to close the alarm vent, and so form a valve of itself), and by
arranging the lower duct or dip pipe at such a level that it commu-
nicates with the water space only when the water level is too high.
Various modifications may be made without departing from the main
feature or principle of the Invention, such as the substitution for the
diaphragm of a piston working in a closed cylinder, the retracting of
the piston being effected by a weight or by springs acting thereon,
though this would be a comparatively imperfect arrangement.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Jolin Millward in the Great Seal Patent Office on
the 6th December 1871.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
MILLWARD, of Curzon Chambers, Paradise Street, Birmingham, in the
County of Warwick, Civil Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Seventh day of June, in the year of
our Lord One thousand eight hundred and seventy-one, in the thirty-
fourth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said John Millward, Her special licence
that I, the said John Millward, my executors, administrators, and
assigns, or such others as I, the said John Millward, 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 "A NEW OR IMPROVED
LOW AND HIGH WATER INDICATOR FOR STEAM BOILERS," (a communication
to me from abroad by Frank Millward, of Cincinnati, in the County of
Hamilton, State of Ohio, United States of America,) upon the condition
(amongst others) that I, the said John Millward, my executors or
administrators, by an instrument in writing under my, or their, or one

page_text: of their hands and seals, should' particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be
performed, 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.
5
NOW KNOW YE, that I, the said John Millward, do hereby declare
the nature of the 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 accompanying
Sheet of Drawings and to the figures and letters marked thereon, that is 1
to say:-
-
The object of this Invention is to obviate the difficulties hitherto
experienced in the operation of indicators arising from incrustation,
friction, and other causes, and to provide an indicator which operates
with certainty and precision under all conditions of boiler pressure, is free ]
from incrustation, and has no rubbing or moving parts liable to stick.
A low water indicator constructed in accordance with this Invention
consists of a closed metallic case divided into two separate and steam-
tight chambers or compartments by an elastic or flexible diaphragm
of corrugated sheet metal or other equivalent affixed therein, and the
said metallic case is supported outside the steam boiler to which it is
attached at a suitable distance above the water level thereof.
One compartment or division of the said case is made to communicate
with the steam space of the said boiler by means of a suitable pipe or
duct and the other compartment or division communicates with the ?
water space of the boiler by a separate dip pipe or suitable, duct opening
into the boiler at the low water or danger level, both compartments
of the case being thus under pressure.
The steam compartment is provided with an alarm vent which is
opened or closed by a valve operated by a simple and direct con-
nection with the diaphragm. When the water in the boiler is at
its proper working level the compartment in connection with the water
space and its connecting pipe are kept filled with water by the pressure
of steam in the boiler, and the pressure per square inch upon the
water side of the diaphragm is less than that of the steam by the
amount of pressure necessary to support the hydrostatic column reaching
up to the case, while the pressure on the steam side of the diaphragm
is practically the same as in the boiler, and this preponderance deflects.

page_text: the elastic diaphragm and keeps the alarm valve closed, but as soon
as the water in the boiler sinks below the dip pipe or lower duct,.
this and the compartment with which it communicates empty into
the boiler and become filled with steam, and the pressure on both
sides of the diaphragm being equalized, the elasticity and retractile
force of the diaphragm at once opens the valve governing the alarm
vent to which may be attached the usual alarm whistle.
•
The diaphragm valve and seat may be plated with nickel or otherwise
protected to prevent corrosion, and as the water never enters the valve
side of the instrument no incrustation can take place and great durability
and freedom of motion are secured. A cock may be fixed to that com-
partment of the case in connection with the water space to empty it of
air when the boiler furnace is first lighted, but this is not a necessity
as the air is condensed into a very small space by the pressure of steam.
and is soon absorbed.
This indicator is applicable as a high water indicator by simply con-
structing the alarm valve so as to cause it to be opened by the deflection.
of the diaphragm, (or the central part of the diaphragm may itself be
made to close the alarm vent and so form a valve of itself,) and by
arranging the lower duct or dip pipe at such a level that it communicates.
with the water space only when the water level is too high.
Various modifications may be made without departing from the main
feature or principle of the Invention such as the substitution for the
diaphragm of a piston working in a closed cylinder, the retracting of
the piston being effected by a weight or by springs acting thereon,
though this would be a comparatively imperfect arrangement.
But in order that this Invention may be fully understood I shall
now proceed moro particularly to describe the manner of performing
the same, and for that purpose shall refer to the several figures on the
accompanying Drawing, the same letters of reference indicating corre-
sponding parts throughout the corresponding Figures.
Figure 1 is a vertical section of a low water indicator constructed
in accordance with this Invention, the connecting pipes being shewn
broken through to diminish height of Drawing. The moving parts are
shown in the position they take when the water in the steam boiler
with which the indicator is in connection is at its proper working height
or level. Figure 2 is a section of the principal portion of the same,'
when the moving parts have changed position to give an alarm when

page_text: the water has fallen below a safe level in the boiler; Figure 3 (drawn
to a smaller scale) shews a combined high and low water indicator on
one stand or support.
The section to the right hand is that of a high water indicator con-
structed in accordance with this Invention the position of the moving |
parts being that taken when the water in the boiler with which the
indicator is in connection is at the proper working level. The indicator
to the left hand is a low water indicator in elevation.
Figure 4 (on the same scale as Figures 1 and 2) is a section of the
principal portion of the high water indicator with the parts in the
position of giving an alarm in consequence of the water being too
high in the boiler.
In the Drawings of the low water indicator, Figures 1 and 2,
A represents a portion of a steam boiler to which the indicator is
attached; B is the closed metallic case made in two parts screwed 1
together in the manner shewn or in any other suitable way. This case
is divided into two chambers or compartments by the diaphragm C
which is inserted and fixed in the said case so as to divide it into two
separate and steam-tight chambers or compartments. The chamber or
compartment D is designed for holding steam exclusively, and the 2
chamber or compartment E for holding steam and water alternately,
the latter chamber being connected with the boiler at the low water
line by the pipe F which is prolonged inside the boiler to the low
water or danger level. The diaphragm is constructed of a sheet of
metal or other suitable material of a flexible or elastic nature, so as 2
to be deflected easily by a slight excess of pressure upon one side,
and may be either plain or corrugated concentrically and radially, to
give freedom of action. It may consist of a volute spring covered
with caoutchouc or other flexible material like the compound diaphragms
used in some pressure gauges. Its upper or exclusively steam face may 3
be constructed by preference of such a shape as to throw off any con-
densed water back into the boiler, and a small notch may be made
under the rib b for this purpose. G is a small pipe connecting the
compartment D with the steam space of the boiler. The pipes F and G
may be connected to the boiler by means of a junction block H, screwed 3
into the boiler as shewn, and may form a stand for the indicator, or
the indicator may be supported in any other preferred position, and the
pipe connections performed in any other known manner. The chamber

page_text: or compartment D of the case B has a vent or aperture at top governed
by a valve I resting upon the valve seat K. The valve is connected
with the diaphragm by means of the stem i screwed or otherwise attached
thereto, and may have a screw or other adjustment as shewn at top to
¡ regulate its action with that of the diaphragm. The stem must be
small enough to allow of the free passage of the steam to the valve, and
no part of this stem need touch the sides of the aperture for the steam
vent, so that frictional surfaces likely to stick upon slight corrosion can
be entirely avoided. If preferred, the seat, valve, and diaphragm may
be plated with nickel or other non-corrosible covering. The chamber D
has no communication with the water space of the boiler, so that no
incrustation can take place in it. The alarm vent may be connected
with a steam whistle L, as shewn. An air cock M (Fig. 3) can be
fixed to the lower compartment for use when first starting to fire the
boiler, but this is not considered necessary as any air is soon absorbed.
When the boiler is in operation and the water high enough to cover
the lower end of the pipe F, the chamber E is filled with water, and
when in this condition the pressure upon the lower side of the diaphragm C
is less than that upon the upper side, owing to the weight of the hydro-
static column in the pipe F, which acts against the pressure of the
stcam in the boiler, and thus reduces to an extent directly proportioned
to its height the pressure on the lower side of the diaphragm, which
would otherwise be exercised by the steam in the boiler, and the excess
of pressure on the exclusively steam side of the diaphragm will keep
the valve closely to its seat and prevent any alarm as long as the water
is at its proper working level. As soon however as it sinks below this
level and uncovers the lower end of the pipe F, the water in the
chamber E is discharged into the boiler and steam takes its place and
equalizes the pressure on both sides of the diaphragm. The latter by
its retractile force and elasticity then resumes its normal shape and
assumes the position shewn in Figure 2, at the same time opening the
valvo and giving the alarm.
To illustrate the principles regulating the dimensions of the apparatus
in accordance with the thickness of the diaphragm or the height of the
indicator above the water level in the boiler I will take the case of an
indicator with an acting diameter of diaphragm of 6 inches and placed
at a level of a little over 2 feet above the water level in the boiler.
With this column an excess of pressure of about 1 lb. per square inch

page_text: will exist on the steam side of the diaphragm, and this acting on the
area of a 6 inch circle will give (after allowing a deduction for the
unbalanced boiler pressure upon the valve) about 25 lbs. to deflect the
diaphragm and keep the valve to its seat. In order to produce a greater
difference than this it is only necessary to increase the height of column |
or the diameter of the diaphragm. The acting force can in this way
be increased or diminished to suit any thickness of plate or a more or
less flexible material of which the diaphragm may be made. The
diaphragms are by preference circular on plan, but any other practicable
configuration may be used.
A high water indicator constructed in accordance with this Invention
is shewn on the right-hand side of Fig. 3 and also in Fig. 4, but it differs
from the low water indicator only in this, that the valve acts in the
opposite direction and the seat is on the inside of the case. The valve
is therefore shut when the diaphragm is exposed to steam pressure on
both sides. The water pipe is made to reach only to the high water
line, so that on the water in the boiler reaching this level and filling the
compartment on the lower side of the diaphragm, an excess of pressure
will be produced above the latter in the same manner as above
described, whereby the diaphragm will be forcibly deflected and the
valve opened and the alarm given. In this indicator the diaphragm
may be made to form its own valve by fixing a faced stud in the middle
of the same, and forming a nozzle to project down from the under side of
the alarm vent to meet it and act as the seat. As regards the general
arrangement of these indicators in relation to the steam boilers, to
which they are connected, it is obvious that the indicator proper may
be placed in almost any position, and at any angle or inclination so
long as the diaphragm or acting part is raised sufficiently above the
working water level in the boiler.
Although the most important application of this Invention is to low
water alarm indicators it is as has already been shewn easily applicable
to high water indicators. Separate indicators for high and low water are
preferred, yet an arrangement is shown in Figure 3 by which two
indicators for high and low water respectively may be combined upon
one stand and with a single attachment to the boiler. In this Figure
N is a cast metal stand or hollow pillar with a partition along its whole
length, and furnished at its base or connection with the boiler with
a pipe from each compartment, dipping to. high and low water lines

page_text: respectively; pipes or elbows F, F, carrying the indicators are screwed
into the cap of the stand and communicate with the corresponding
divisions of the stand pipe. The steam pipe G communicates with the
steam space of the boiler by means of a separate orifice in the base of
the stand and branches off at top to the indicators.
The arrangement preferred in the application of the low water indi-
cators to boilers known as the "Cornish" or "Fairbairn" types where
the flat ends project through the brick seating, is that of securing tho
main pipe or the pipe communicating with the water compartment of
the indicator by an elbow or junction piece screwing into or to the front
of the boiler at the low water level, and arranging it vertically in front
of the boiler, and by connecting the steam compartment by a short
vertical pipe from the top of the boiler. This is the most compact and
economical arrangement, and is also applicable to boilers of the vertical
typo by supposing any part of the circumference of the shell to bo
represented by the front of a Cornish boiler. This arrangement is also
applicable to high water indicators by an obvious alteration in the
position of the junction with the boiler of the pipe connecting with
the water side of the indicator. The connecting pipes of low water
indicators may also be used in combination with gauge cocks so as to
save separate connections with the boiler.
By the above-described means an alarm indicator for low or high
water is provided in which friction is almost or entirely avoided, and the
incrustation of the valve and seat which so much prevails in the best
indicators heretofore in use, thus rendering them comparatively useless,
is prevented, and a certain and reliable alarm insured.
Having thus described the nature of this Invention, and the manner
in which the same is to be performed, I wish it to be understood that I
do not limit myself to the precise details of construction and arrange-
ments of the improved apparatus herein-before described with reference
to the accompanying Drawing, as it is obvious that many modifications
may be made in the construction of these indicators, and in their
arrangement with reference to the boilers with which they are connected,
without in any way departing from the principles of construction or
essential features of the Invention, but what I claim as new and desire
to have secured to me by the herein-before in part recited Letters
Patent is, the construction of a water level alarm indicator for steam
boilers wherein a flexible diaphragm or its equivalent is acted on by

page_text: preponderating fluid pressure, substantially as and for the purpose
herein-before described.
In witness whereof, I, the said John Millward, have hereunto
set my hand and seal, this Fifth day of December, in the year
of our Lord One thousand eight hundred and seventy-one.