Improvements in Apparatus for Determining the Quantity of Moisture in Steam.
Year: 1889

page_text: COMPLETE SPECIFICATION.
Improvements in Apparatus for Determining the Quantity of
Moisture in Steam.
I, GEORGE HALE BARRUS, of the Town of Reading, in the County of Middlesex
and State of Massachusetts, United States of America, Civil Engineer, do
hereby declare the nature of my invention and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement:
My invention has for its object to provide a simple, reliable, easily operated, and
inexpensive apparatus for determining the quantity of moisture in wet steam, and it
consists in the improvements which I will now proceed to describe.
The construction and the method of operation of my improved, apparatus will be
understood by reference to the appended drawing, which forms a part of this
specification and represents a sectional view of said apparatus.
The apparatus consists of two parts, one a drip chamber, and the other a heat
measuring device.
In the drawings
G represents the main service pipe which conducts steam from the boiler.
F represents a pipe inserted in the service pipe G and provided within the latter
with numerous small holes, about fifty one-eighth inch holes being a suitable number.
A supply valve H is connected with the pipe F to prevent the passage of steam there-
through when the apparatus is not in use. The steam passing through the pipe F
The pipe B
is conducted by a pipe B, connected therewith, into a drip chamber A.
extends into the drip chamber below the steam outlet E, described later, so that the
particles of entrained water are thrown to the bottom of the drip chamber and are there
deposited. The water which thus collects is drawn off through valve D into a
receptacle, not shown, and its quantity is determined by weighing. The level of the
water in the chamber A is determined by a glass water gauge C. The steam is
deprived of most of its moisture in the drip chamber, and passes from the latter
through the pipe E to the heat measurer, which consists of the following elements,
viz.: first, a chamber K connected with the pipe E; secondly, a thermometer M the
bulb of which is within said chamber; thirdly, the chamber L connected with the
chamber K so as to receive the steam which passes through the latter, and having
its lower end open to the atmosphere; fourthly, a thermometer N in the chamber L;
fifthly, a device for wire-drawing the steam between the chambers K and L, said
device being here shown as a diaphragm R provided with a small orifice I, about
one-eighth of an inch in diameter, and clamped between two flanges S S on the
pipes which connect the chambers K and L; and lastly a heat insulating device to
prevent the conduction of heat along the pipes to the point where the steam is
reduced to low pressure.
The heat insulating device is here shown as composed of
layers J of asbestos, or other non-conductor of heat, interposed between the
diaphragm and the flanges S S and placed under the heads of the bolts which connect
said flanges.
The wire-drawing orifice 1 may be formed in a movable valve or other suitable
body instead of in a diaphragm. The orifice I by wire-drawing the steain superheats

page_text: it, because the steam which enters the heat-measurer contains such a small amount of
moisture that when it is expanded through said orifice to the atmospheric pressure
which exists beneath, the moisture is all evaporated and the steam in its state of
reduced pressure becomes superheated. The extent to which superheating is produced
is shown by the thermometer N. In proportion as the quantity of moistures varies,
the quantity of superheat varies, and upon this fact depends the operation of the
heat measurer. The insulator prevents the conduction of heat from the high
pressure steam to the low pressure steam through the walls of the connecting pipes.
If no insulator were used, the low pressure steam might be superheated to some
extent by means of heat derived from the walls of the main service pipe G, and a
result obtained which would not show the true condition of the steam. The particular
arrangement of insulator here shown is not essential to the accomplishment of the
desired object. The insulator may he of any form to intercept the conduction of
heat along the walls of the pipe, and may be placed at any point between the service
main and the orifice. A pressure gauge may be used in place of the thermometer M,
but the thermometer is to be preferred.
The thermometer chambers are filled with oil or mercury, and the exterior of the
apparatus is preferably protected from radiation by a covering of hair felting, or
other non-conducting material.
In operating this apparatus a sample of the steam to be tested is drawn from
the main service pipe G. The drip valve D is kept opened sufficiently to maintain
the water level in the drip chamber at a constant point, the hot water which is
drained off being carried by means of a rubber tube into a bucket of cold water
resting on scales. The increase in weight which the scales register in any given
period of time, represents the quantity of moisture deposited in the drip chamber,
and its percentage is found by comparison with the quantity of steam discharged in
the same time from the orifice. This last quantity is found either by calculation in
accordance with the law concerning the flow of steam through an orifice, or by
actual determination, the steam being carried for this purpose into a barrel of water
resting on scales or into a condenser. This determines a part of the desired result.
The remaining quantity of moisture is determined by observing the thermometers M
and N. The moisture in the steam passing through this part of the apparatus, is
represented by the difference between the total heat of the escaping low pressure
steam, which is at atmospheric pressure, and that of dry steam of the high pressure.
The total heat of the escaping steam is found by subtracting 212 degrees from the
indication of the thermometer N, and adding the number of thermal units corre-
sponding to the superheating thus found to 1178 (the total heat of one pound of dry-
steam of atmospheric pressure). For example, suppose thermometer M indicates 320
degrees, the pressure above the orifice being about 80 pounds, and thermometer N
262 degrees.
The total heat of one pound of dry steam at 320 degrees is 1211
thermal units. The escaping atmospheric steam is superheated 262-212=50° and
its total heat is 1178+ (50x475)=1178+23-7=12017 (475 being the specific heat
of superheated steam). The difference between the two total heats is 1211-1201-7
=9-3 thermal units, and this difference forms a measure, as above indicated, of the
quantity of moisture which is present. The percentage of moisture is obtained by
dividing this quantity by the latent heat of the high pressure steam, that is, by 888.1,
and multiplying the result by 100. Thus 9.3-888-1 x 100=1-059%. The percentage
of moisture thus obtained added to that found in the drip chamber already pointed
out, and corrected for a constant loss of heat due to radiation from the apparatus,
gives the total quantity of moisture desired.
The complete apparatus in the form thus far described, is intended for cases where
the amount of moisture is excessive, that is where (for pressures in the neighborhood
of 80 pounds) the percentage exceeds say 3%. If the steam contains less than 3%
at pressures of about 80 lbs., or if it is practically dry, the drip chamber may be
dispensed with and simply the heat-measurer used. The apparatus is constructed with
'two interchangeable unions P and Q, so that either the complete apparatus or simply
the heat-measurer may be attached to the supply valve H, as desired. When it is

page_text: desired to make a test, a preliminary trial is first made, using simply the heat-
measurer. If the thermometer N indicates a temperature considerably above 212
degrees, this part of the apparatus will answer all requirements. If, on the other
hand, the temperature is 212 degrees or only slightly in excess of 212 degrees,
either continuously or intermittently, the complete apparatus must be called
into use.
While the insulating device is a very desirable part of the apparatus, as above
stated, I do not desire to limit myself to its use in all cases, as a comparatively
useful apparatus can be made without said device.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :
1. In an apparatus for determining the quantity of moisture in steam a drip
chamber for the deposit and measurement of most of the entrained water contained
in the wet steam tested, combined with a heat-measurer in which the balance of the
moisture is measured, in the manner and for the purposes set forth.
2. In an apparatus for determining the quantity of moisture in steam the combination
of two thermometer chambers, with their respective thermometers, one subjected to
the steam of initial pressure, the other to the escaping steam of atmospheric pressure,
the second chamber being open to the atmosphere, and means for wire-drawing the
steam interposed between the two thermometer chambers, in the manner aud for the
purposes set forth.
3. In an apparatus for determining the quantity of moisture in steam the com-
bination of two thermometer chambers with their respective thermometers, one
subjected to the steam of initial pressure, the other to the escaping steam of atmospheric
pressure, the second chamber being open to the atmosphero, means for wire-drawing
the steam interposed between the two thermometer chambers, and an insulating device
for intercepting the transfer of heat along the walls of the pipe to the wire-drawn
steam, in the manner and for the purposes set forth.
4. In an apparatus for determining the quantity of moisture in steam the com-
bination of means for wire-drawing the steam, and a thermometer chamber (which
is open to the atmosphere) with its thermometer for showing the temperature of the
escaping steam, in the manner and for the purposes set forth.
5. In an apparatus for determining the quantity of moisture in steam the com-
bination of means for wire-drawing the steam, a thermometer chamber (which is
open to the atmosphere) with its thermometer for showing the temperature of the
escaping steam, and an insulating device for intercepting the transfer of heat along
the walls of the pipe to the wire-drawn steam, in the manner and for the purposes
set forth.
רדי
GEORGE HALE BARRUS.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, Agents for the Applicant.