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THESIS
A STUDY AND CALIBRATION
oF
VENTURI WATER METERS
| we re BY wey
E.G. SCHUBAGH, = 8; P; WANDEL.
JUEB
1912.
THESIS
Introduction.

This thesis eonsists of the study and calibration of three
Venturi water meters, to determine their coefficients. These
meters were designed by J. <A. Polson, Asa't Prof. Meah, Eng.
and made to determine the boiler feed water at M. A. 9. The
general plan followed and the apparatus used will be deseribed
under separate heads. a

Tests were made with a steady pressure sedur ing a very
constant flow. Resdings were taken under different pressures,
beginning with 10 lbs. pressure per square ineh and running up
to 50 by intervals of 5 and then by intervals of 25 up to 100
ibs. per square inch. Several Fates of flow under each pres-
aure head were taken,

Much information concerning the above exper inent was ob-
tained from the different engineering magasines and also from
the "Transactions of the Ameriean Society of caviar and Mechani-
cal Engineers" e@. g.

Trans. A. 8 C. B. June 1891, "Discussion on Water
Meters* by J. Thompson.

Trans. A. 8. C. Be. Deo. 21, 1887, "Papers Pertaining
to Tests on Venturi Meters® by Clemens Hersehel.

Trans. A. 8. C. B. Vol. 31, 1909, "Testa on Venturi
Meter® by Prof. C. M. Allen.

Engineering News, Feb. 28, 1901, "Gauges to be Used with
Venturi Meter® by C. P. Spalding.

We are also indebted to Prof. Polson of the Engineering
Laboratory for information and help in performing the tests, al-
eo te Mr. Crawford for the setting up of the apparatus.

LO3751L
oe
Description ef Apparatus.

The apparatus used in performing the tests is showa in
the picture attached herete. The meters were connected up in
series to the pressure tank. The first of the testa &. g-

10 & 20 lbs. were run by means of this tank only, this giving
a steady head. This consists of a large tank on the fourth
floor of Engineering Hall, water being forced up by means of
the pump. SBya series of valves on the oylindrical tank in
Hyfraulio Laberatory shown in the picture a—é the water is
allewed to flew down thru this tank by gravity and thru the
meters. The water is allowed to flow in the tank en fourth
fleor during the entire tests, thus keeping the desired head.

_ Manometer tubes were made and placed as indicated by the
pieture. By means of these the Venturi head and friction
losses were determined, the first manometer denoting the Ven-
turi head, the secondthe loss in friction in the particular
tube to which it is attached.

At the end of the series of meters was connected a stani-
ard moter reading the discharge direct. At the entrance of
. the first moter was placed a pressure gauge, to determine the
prepaure at entrance, also one was placed at the end to de-
‘terming the pressure at the discharge end. These gauges are
indicated as Ne. 1 and Ho. & on the picture.

A valve was inserted in the pipe which connects the meter
with the pressure tank, which by means of throttiing the desired
pressure head was obtainable. <A sseond vaive (valve No. 2)
was inserted at the pipe leading to the weighing tank.

To each pipe ieading to the manometer tubes was placed a
vaive. In each of these manometer tubes was piaced from
eighteen to twenty inches of mercury.

The weighing tank shown in the picture was placed upon
the scales and had a eapacity of some fifty cubic feet.
a
Method of Operation
The first two pressures were ebtained by means of punping
water to the tank on the fourth floor ef Rngineering Hall,
then throttling the valve to obtain the desired head. The
remainder of the testes were run by using the Dupies pump ia

the Steam Laboratory, pumping the water from the Ceddér river
direct to the meters, regulating the pressure by means of valve

Noe le
The maximum flow was first obtained by cheeking the water

flowing thru the meter by means of valve No. 2. This valve
being placed here in order to regulate the flow, thus keeping
the mercury column on the scale, making them readable andi also
keeping the meters under the desired pressure.

After the maximum flow was obtained the valves leading
to manometer tubes were opened, water being allowed te run

thru the meters until the mercury columns beeame steady. The w
water was now directed to the weighing tank. Several rates
of flew were made upon each head by checking valve No. 2.

While the water was being discharged into the tank five

readings were taken on each of the different flows, thus obtain
ing a fair average of the readings of the mereury columns.
The time in each case varied with the quantity of discharge
which depended upon the rate of flow.
The fluctuations ef the meroury in the manometer tubes
due te unsteadiness ef the Duplex pump were overcome by partly
filling the pressure qhamber in the laboratory with air, the
air acting "SB a Guahion, alse by means of throttling valves
. leading to the pressure chamber. yy
All thermometers, acales and pressure gauges were cali- -
brated. }
~5-
She scales were found to be sorrect within a very large
range. The thermometer was ealibrated by comparing with
the etandard thermometer Mo. 26 which itself was correct up

to 77° being within limits of temperatures obtained in the testy
Pressure gauges were calibrated by means of the “"Croaby

Gauge Testor®.

Gauge No. 1 indicating the gauge at entrance and No. 2
the one at the discharge end.

Curves pertaining to calibrations are shown iu the
appendix.
a,
VYormulae and Calculations

fo reduce inches of mercury to feet of water taking
the unbalaneed column of water inte account ‘

grecific gravity XH} #
he rT

~ (13.88 — i)
h= , lz » 1.05 H
h= 14.56 X 1.05 = 15.28 ft. ef water

where H= inches of meroury as read,

 

h= feet of water

Vv
wt
905
=" 3 X 60 X 62.4
where @= actual quantity delivered(eu. ft. sec.)

We actual weight of water

 

* 1692 eu, ft. s8Ge

ws unit weight at temperature of water
t= time in secends

Qn Mex 8.08 bh
A f

1

008432 % 02 X 8.02 X 15.28" .1758 ou. ft.

=~ (.005452)

: . S6C.
where @ theoretical quantity (ou. ft. acc.$

a= area of throat in square feet
a area of iniet in square feet
h= venturi head in feet of water
mt

69

where of coefficient.
APPENDIX.
Outiine of Thesis

Title: Study and Calibration of Three Benturi Tubes

The object is to calibrate and study the three tubes, te be
used in measuring Bailer feed water, The tests to be made in

order to determinde the coefficient. Tests to be made with
steady pressure, securing a very constant flow.

Owing te the fact that heads greater than 50 ibs cannot
be obtained by means of the facilities offered in the Hydraulic
Laboratory, therefore the mumber of readings will be limited
to four e. g- 20, 50, 40, and 50 ibs. heads. The rest of
the test to be run in the engine room or laberatory , obtaining
the desired heads by means of the pump, The heads here are
to be 125 lbs. per sq. in. as the highest and then baek by
intervals of 25 e. g. 125, 100, 75, 60, 25. ‘The meters to be
tested were made in the shops. They are te be connected up
in series. A pipe is to be connected up with the meters and
the tank. In connection with this a standard tube, with man-
ometer attached is to be placed so that a eomparison can be
made. This standard is to be shifted e. g. inserting it at
the ends and then to see the affect ut any by changing to another
position. |

PieZometer tubes or mercury eolumns whet(necessary to be
inserted into the tubes to obtain the Venturi head and the
head due to friction. A valve is to be inserted at the end.

Rates of flow will be run under seach head by throttling he
valve, The tests are to be made by diverting the discharge
Le

inte the weighing tank, ene tank being weighed while the other
is filling, the duration to be noted as well as the Venturi
heads. Readings to be taken every five minutes.
Yormula to be used.
Wa 60 wact 2g h
We actual weight of water from the tank
weight of eubic foot at that temperature

a area Venturi throat

7

e= coefficient
t= time in minutes
he Venturi head

qemessreteeraneneedlloncenceneece
o" 60 wa t gh

References:

Trans. A. 8. C. BE. June 1692, "Diseussion on Water Meters* by
g- Thomson.

Trans. A. 8. ©. 3. Dee. 21, 1887, "Papers Pertaining to Tests

on Venturi Meters® by Clemens Herehel.

Trans. A. 8. M. B. Vol. 31, 1909, "Tests on Venturi Meters"
by Prof. C. M. Allen.

Trans. A. 8. M. E. Dea. 1893, "Calibration of a Verthington
Water Meter® by John A. Laird.

Engineering “News Feb. 26, 1901, "Gauges to be Used With the
Venturi Meter® by Charies P. Spalding.

Engineering News Sept. 2, 1882, "Description of Gauges?
Catalogs and other literature were read from Builders

Yron Foundry Co. and Simplex Valve and Meter Co. Other small

articles were read in Engineer ing News ,Engineering Record ,

and Engineering Journal.
~10-

Final Thesis Time Report.

Mareh 28 te April 7 was spent inreading in the library on
she Venturi Meters, tests and general information,

Apr. 7 to APr. 12Fixing pipe for overflow and adjusting Ventut
tubes.

Apr. 12, to Apr. 18 tesaning out run-off, calibrating scales.

Apr. 19 Testing out Venturi tubes separately.

Apr. 19, to Apr. 27 Fixing and adjusting tubes to pressure
tank, Cleaning mercury.

May 3 Began on tests, running ‘on the average of two pressure
heads per day. |

May 9 Ran 100lb. pressure head.

May 18 to May 20 Tried to run 1251b.

May 22 to May 31 Time was spent on data, writing up, Plot-
ting curves, ete.

Tetal time up to date = 225 hours.
“Lie

Conclusions.

Many difficulties were encountered in performing this

thesis.
Considerable time was spent in repairing the meters,
especially meter No. il. Several sand holds were formed ,

whereupon water entering would leak thru. The meters were

finally set up and arranged as indicated in the picture.
Mere trouble was eneountered with the manometer tubes,

mereury being foreed out thre the eonnections, this how-
Ser eas not @nosuntered until higher pressures were met with,

It was our intention first to shift the meters after the
first series of tests were run (placing the meter in differ-
ent series) but owing to the length of time taken in perform-
ing the first tests this was impossible,

In comparing the results obtained under the conditions
imposed upom us, it can be seen on consulting the data sheets
that meter Ho. 2 is iowest in friction loss, No. 3 and No. 4
follewing in order. In respect to the corfficients of the }
three meters, the first meter no doubt is the best, as the
coeffieients of each flow are all more uniform than in the
other two, also lying within limits of coefficients which
men Of authority have determined.

In meter No. 3 the coefficients all vary to a greater

extent, but averaging to a reasonable coefficient. In meter
No. 2 the coefficients all range above 1.00.
oe
The coeffieient of each meter compared with the constant
in the formula

a, a
~ a= ey is as follows:
meter constant ecefficient
Now 1 1.15 2965
Ko. 2 1.15 1.04
Ho. 3 1-45 09935

The diameters of each meter were not to dimensions: as
indicated on the data sheets.

In general, moter No.l would be the most desirable to
be used. |
 

 
 

 

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