California Academy of Soieaoea Carl Ewald Gruneky Bequest August I, 1034

i

The Venturi Meter

BUILDERS IRON FOUNDRY PROVIDENCE, R. I., U. S. A.

o en

^

THE VENTURI METER

PATENTED BY &

CLEMENS HERSCHEL

HYDRAULIC ENGINEER

AND BUILDERS IRON FOUNDRY

MADE BY

BUILDERS IRON FOUNDRY

FOUNDERS AND MACHINISTS

PROVIDENCE, R. I., u. s. A. 1898.

COPYRIGHTED, 1898, BY BUILDERS IRON FOUNDRY, PROVIDENCE, R. PRESS OF LIVERMORE & KNIGHT CO., PROVIDENCE, R. !.

PREFACE

In the papers that have hitherto been published by us concerning the Venturi Meter, (copies of which will be furnished upon application), we have given a more or less technical explanation of the physical laws governing the action of the meter, and called attention to the uses to which it could be applied. The object of this pamphlet is to again state the facts relating to the operation of the meter, as briefly as possible, and to show by some illustrations how it has been applied in actual uses.

BUILDERS IRON FOUNDRY.

PROVIDENCE, R. I., January i, 1898.

THE VENTURI METER

The Meter is named for the Italian philosopher ongin of name. Venturi, who first called attention, in 1796, to the relation between the velocities and pressures of fluids when flowing through converging and diverging tubes.

The Meter consists of two parts — the Tube, Principal parts

. .of meter.

through which the water flows, and the Register, which sums up and indicates on a dial the quantity of water that has passed through the tube.

The Tube is formed of two truncated cones, The Tube, its joined at their smallest diameters by a short throat piece. At the upstream end and at the throat there are encircling pressure chambers that are connected with the interior by carefully drilled holes, and from which pressure pipes lead to the register. See Figure i .

The operation of the Venturi Meter is due to the operation of the fact that when water in any pipe passes from a state of rest to movement, or from one velocity of flow to a greater velocity, a certain amount of pressure against the shell of the pipe disappears, and that the disap- velocities. pearance of pressure, or loss of head, is entirely dependent upon the velocities of flow past the points in the pipe at which pressure is taken.

Therefore, at two points in a taper pipe, or Venturi tube, as at U-T, Figure i, because of different sec-

VENTURI METER

FIGURE i. SECTIONAL VIEW OF VENTURI METER TUBE AND REGISTER.

tional area, different velocities and consequently differ- ent pressures must exist whenever there is any flow through the tube. The difference in pressure at the two points is always the same for the same velocity of flow, whatever the total or hydraulic pressure may be; and by exhaustive experiment has been shown to be nearly equal (in feet of water) to 1-64 the square of the velocity of flow (in feet per second) through throat of meter tube; or, in other words, to coincide closely with the fundamental hydraulic formula for the head corresponding to any velocity of discharge from an orifice,

in which "h" corresponds to the difference in pressure at U and T, V the velocity of flow through throat, and g the acceleration of gravity.

For demonstration of the preceding statements, see Herschel's Rowland Prize Paper, Transactions of American Society of Civil Engineers, December, 1877. Reprint furnished on application. Merriman's Hydraulics, Article 71, (Reprinted herewith.) Illustrations of the Theorem of Bernouilli under " Hydro- mechanics," — Qth Edition Encyclopaedia Britannica, or reprint furnished on application, and almost any modern text book on Hydraulics.

The different pressures existing at the upstream Register. end and throat of the meter tube are transmitted by small pipes T— U, to the register (Figure i), where they oppose one another, and are balanced by dis- placement of level of two columns of mercury in cylindrical tubes, one within the other. The inner mercury column carries a float, J, V, the position of which is dependent on, and as previously explained is an indication of the velocity of water flowing through

FIGURE 2. REGISTER.

the tube. The position assumed by an idler wheel H carried by this float, relative to an intermittently re- volving integrating drum I, determines the duration of contact of gears G and F connecting drum and counter, by which the flow for successive intervals is registered.

It is a common but erroneous impression that water common error

n • • i i • ' • i • ' j regarding loss of

flowing through a contracting pipe brings an increased head pressure against the entire converging surface which it meets. The reverse of this impression is true. The pressure of water flowing through the Venturi Tube decreases from the inlet to the throat, and increases from the throat to the outlet. The difference between pres- sures at inlet and outlet ends of the Tube is the friction head or loss of head caused by its operation, and under ordinary circumstances is inconsiderable. The amount

/- i • i • i -11 r ' * inconsiderable.

of this loss in tubes with throat area 1-9 of main is stated in the accompanying tables and shown by dia- gram, Figure 10. By adaptation of the tube to re- quirements, the loss of head may be limited to any desired amount.

There is no limit to the size of the meter tubes, Advantage of nor the quantity of water that may be measured. The ™l™~™ largest that has yet been made is 9 feet diameter, with maximum capacity at the rate of more than 200,000,000 gallons in 24 hours.

Usually the meter tubes, for sizes under 60 inches diameter, are made of cast iron, with bronze-lined throat pieces, but for special service may be made of wooden staves, sheet steel, cement-concrete, brick or other material, with suitable metal parts for throat and up- steam pressure chambers.

The tube is usually laid as a part of the pipe line Meter not and is not injuriously affected by water hammer or

stances in the

FIGURE 3. BACK OF REGISTER.

the most violent fluctuations of velocity or pressure, and requires no more care than the pipe line itself. The meter cannot be disarranged by fish, gravel or other substances carried through the pipe line by the water.

The meter may be said to have created a field of General u

J ness.

usefulness for water meters which did not previously exist. It accomplishes with little difficulty what otherwise is done only laboriously or approximately and clumsily.

In water works, this meter enables a record to be Special ad kept of the total quantity consumed, also, of the quantities consumed by large users, such as adjacent towns and cities, the several districts of one and the same city, railroads, factories and the like. See Fig. 11.

As it cannot be disarranged by substances in the Fire service. water, it is especially desirable, when the water it measures is liable to be used for fire service.

It can be used as a " waste-water meter," keeping a record of the quantity passing the meter at any time. Its use in the detection of wastes and leaks,* and as a measure of the slip of pumps/)* and the action of filter plants, makes it very valuable to all works for a pub- lic supply of water.

A similar line of service can be done by this meter special adva

i c f i • i tages forsew

in the case or sewerage systems, many or which, as agesystem. now built, are constructed and operated for the joint benefit of several towns and cities, with the cost of operation divided pro rata between them, according to the quantity of sewage contributed.

For irrigation works this meter can accomplish what special adva has hitherto been desired but has not been practicable, [^work^ It enables water for irrigation purposes to be sold strictly by measure, and with practically no constraint as to the time when it may be drawn.

*See Report of 1896-97, Water Commissioners, Clinton, Mass. fSee Report of Bureau of Water, City of Philadelphia, 1896.

I I

Special advan- tages for mills and factories.

In the case of water powers, this meter is valuable in determining the quantity of water drawn by tenants of water-rights for power, or for wash water and other purposes other than power.

It offers to mills and factories a means of checking charges for power, or for ascertaining the amount of power used.J Figure 5. It can be submerged in a flume or penstock, and enables large bodies of water to be measured regularly and accurately.

4-lNCH VENTURI TUBE, SPIGOT ENDS.

MEMORANDA

Column of water i foot high Column of water i foot high cury 0.883 ms- n^gh> at 62° F. Gallon

Cubic foot of water Cubic foot of water Flow at rate of i cubic ft. per 646,000 gallons.

2g - 64.33

= 0.433 lt>s- at 62° F. = Column of Mer-

231 cubic ins. 0.1337 cubic foot. 8.335lbs.at62°F. 3.786 litres. 7.480 gallons. 62.355 lbs.at62°F. second for 24 hours

2 » 8.02

JSee Engineering News, Vol. XXXVIII, No. 2, July Pioneer Electric Power Co., at Ogden, Utah."

1897. " The Plant of the

12

FIGURE 5.

ONE OF Two 54-INCH VENTURI METERS.

POWER STATION PIONEER ELECTRIC POWER Co.

OGDEN, UTAH.

FIGURE 6. 16-lNCH VENTURI METER TUBE.

FIGURE 7. 20-lNCH VENTURI METER TUBE.

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w fc ffi o to £

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TABLE SHOWING QUANTITY OF WATER PASSING THROUGH VENTURI METER TUBES OF DIFFERENT SIZES (THROAT AREA 1-9 OF MAIN), WITH CORRESPOND- ING VELOCITY OF FLOW IN THROAT, " HEAD ON

VENTURI," AND " FRICTION HEAD."*

" HEAD ON VENTURI " is the difference of pressure, in feet of water, at throat and up-stream end of tube.

" FRICTION HEAD " is the difference of pressure, in feet of water, at up-stream and down-stream ends of tube, or the LOSS OF HEAD due to introduction of meter tube.

Vel. through throat in ft. per second	Quantity in Cubic Feet per Second.	Head on Venturi, in feet.	Friction Head in feet, approxi- mate.
lo-inch Meter.	12-inch Meter.	i5-inch Meter.	i6-inch Meter.	i8-inch Meter.	2O-inch Meter.
2-5	.152	.218	•340	•389	.490	.608	.097	•015
3-	.182	.261	.408	.466	.589	.728	.14	.02
3-5	.212	•305	•477	•543	.687	.848	.19	.025
4-	.242	.348	•545	.619	.784	.968	•25	•03
5-	•303	.436	.681	•778	.981	1. 212	•39	•05
6.	•364	.523	.818	•932	.179	1.456	.56	.07
7-	.424	.6lO	•954	.086	•374	1.696	.76	.10
8.	.485	.697	.090	•238	-570	1.940	1. 00	•13
9-	•545	.785	.227	.398	.767	2.180	1.20	•17
10.	.606	.872	.362	.556	-963	2.424	1.50	.22
12.	.727	.047	.636	.864	2-357	2.908	2.26	.32
14-	.850	.224	.908	2.172 1 2.748	3.400	3.10	.42
16.	.970	•396	2.181	2.476	3-!4i	3.880	4-05	•53
18.	.090	•570	2-454	2.796	3-534	4.360	5.16	.67
20.	.212	•745	2.727	3.II2	3-927	4.848	6.40	.82
24.	•450	2.094	3.272	3.728	4.712	5.800	9.21	1.20
28.	.700	2-443	3-8i7	4-344	5-497	6.800	12.73	1.68
32-	.940	2.792	4-363	4-952	6.287	7.760	17.25	2.IO
36.	2.180	3-Hi	4.908	5-592	7.062	8.720	21.75	2.70
38.	2.300	3-3*6	5.181	5-9I3	7-455	9.200	24.50	3.00

* To meet special requirements as to Capacity or Friction Head, Meter Tubes are made with throats of any area less than one-fourth the area of main pipe.

TABLE SHOWING QUANTITY OF WATER PASSING THROUGH VENTURI METER TUBES OF DIFFERENT SIZES (THROAT AREA 1-9 OF MAIN), WITH CORRESPOND- ING VELOCITY OF FLOW IN THROAT, " HEAD ON

VENTURI," AND " FRICTION HEAD."*

" HEAD ON VENTURI" is the difference of pressure, in feet of water, at throat and up-stream end of tube.

" FRICTION HEAD" is the difference of pressure, in feet of water, at up-stream and down-stream ends of tube, or the LOSS OF HEAD due to introduction of meter tube.

Vel. thro' throat in feet per sec.	Quantity in Cubic Feet per second.	Head on Venturi, in feet.	Friction Head in feet, approx- imate.
2i-inch Meter.	24-inch Meter.	27-inch Meter.	30-inch Meter.	36-inch Meter.	42-inch Meter.
2.5	.668	.872	I.IO4	I-363	1.963	2.672	•097	.015
3-	.801	1.046	I-325	1.636	2-355	3.207	.14	.02
3-5	•935	1. 221	I.546	1.908	2.748	3-741	.19	-025
4-	1.069	1.396	1.767	2.181	3-I4I	4.277	.25	•°3
5-	1.336	1.744	2.208	2.727	3-927	5-345	•39	•°5
6.	1.603	2.092	2^650	3-272	4.712	6.414	•56	.07
7-	1.871	2-443	3.092	3.817	5-497	7.482	•76	.IO
8.	2.138	2.792	3-534	4-363	5-283	8-552	I.OO	•13
9-	2.405	3-I38	3-976	4.908	7.068	9.621	i. 20	•17
10.	2.672	3.488	4.417	5-454	7-854	10.690	1.50	.22
12.	3.204	4.188	5-301	6-545	9-424	12.828	2.26	•32
14.	3.740	4.888	6.184	7-630	10.995	14.964	3.10	.42
16.	4.276	5.585	7.068	8.727	12.566	17.104	4-05	•53
18.	4.812	6.284	7.952	9.817	H.I37	19.242	5.16	-67
20.	5-345	6.976	8.835	10.908	15.708	21.386	6.40	.82
24.	6.408	8-377	10.602	13.090	18.849	25-656	9.21	1.20
28.	7.484	9-773	12.370	15.271	21.991	29.932	12.73	1.68
32.	8.552	1 1 . 1 70	H.I37	J7-453	25-132	34.208	17.25	2.10
36.	9.624	12.566	15.904	19-635	28.274	38.484	21-75	2-70
38.	10-155	13.264	16.776	20.725	29.845	40.622	24.50	3-oo

* To meet special requirements as to Capacity or Friction Head, Meter Tubes are made with throats of any area less than one-fourth the area of main pipe.

20

TABLE SHOWING QUANTITY OF WATER PASSING THROUGH VENTURI METER TUBES OF DIFFERENT SIZES

(THROAT AREA 1-9 OF MAIN), WITH CORRESPOND- ING VELOCITY OF FLOW IN THROAT, " HEAD ON

VENTURI," AND "FRICTION HEAD."*

" HEAD ON VENTURI " is the difference of pressure, in feet of water, at throat and up-stream end of tube.

" FRICTION HEAD " is the difference of pressure, in feet of water, at up-stream and down-stream ends of tube, or the LOSS OF HEAD due to introduction of meter tube.

Ill	Quantity in Cubic Feet per Second.	Head on	Friction Head
•til	48-inch	54-inch	6o-inch	72-inch	8o-inch	Venturi, in feet.	in feet, approxi-
	Meter.	Meter.	Meter.	Meter.	Meter.		mate.
2-5	3-490	4.417	5-454	7-854	9.647	.097	.015
3.	4.188	5-301	6-545	9-435	11-577	.14	.02
l.C	4.886	6.185	7.640	10.995	I3-507	.19	•025
J -J 4-	5-585	7.068	8.728	12.682	I5-500	•25	•03
5.	6.981	8.835	10.906	15.708	19.295	-39	•05
6.	8-377	IO.6O2	13.090	18.849	23.154	•56	.07
7.	9.772	12.370	15.280	21.990	27.014	-76	.IO
8.	1 1 . 1 7O	14.136	I7-452	23-364	3I.OOO	I.OO	•13
9-	12.564	15-903	19-635	25-305	34-731	i. 20	•17
10. 12.	13.962 16.754	17.670 21.204	21.816 26.180	31.416 37.698	38-390 46.308	1.50 2.26	.22 •32
14.	19-554	24.740	30.560	43.980	54.028	3.10	.42
16. 18. 20.	22.340 25.128 27.924	28.272 31.806 35-340	34.904 39.270	50.728 56.610 62.832	62.000 69.462 76.780	4-05 5.16 6.40	•53 -67 .82
24. 28.	33-508 39.088	42.408 49.480	52.360 61.120	75-396 87.960	92.616 108.046	9.21 12.73	1.20 1.68
32- 36.	44.780 50.256	56-544 63.612	69.808 78.549	101.456 II3-738	124.000 138.924	17-25 21-75	2.IO 2.70
38-	53-052	67.146	82.900	119.442	i47-!54	24.50	3.00

* To meet special requirements as to Capacity or Friction Head, Meter Tubes are made fith throats of any area less than one-fourth the area of main pipe.

21

uosjwj 01 • •- si/«y wn 01

ACCURACY

The accuracy of the meter has been fully de- monstrated by numerous tests, and when these have been made with the care that should be exercised in any hydraulic experiment, most satisfactory results have been obtained.

No better demonstration of the accuracy of the Venturi meter can be presented than the continuous performance of thirteen meters on the works of the East Jersey Water Company. That Company has a contract with the City of Newark, N. J., to supply it with not more than 27^2 million gallons of water per day. The Company controls the water shed and plant supplying this water, and is allowed to dispose of the balance that the works supply to other cities and towns. In this way it supplies at the present time Jersey City, the City of Bayonne, the Township of Franklin, the Town of Montclair, N. J., and other consumers. All the water is sold by measure, through ten Venturi meters, and daily records are kept of the quantities delivered to the principal consumers, with weekly and monthly records for the smaller consumers. Daily records are also kept of the quantities delivered to the conduits through receiving meters at the intake.

The arrangement of the meters is shown by diagram, Fig. n,and the following table compiled from official records of the Company shows comparison of Receiving and Selling meters for seventeen months.

From this table it will be seen that in seventeen

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months 27,2 1 8,700,000 gallons of water were delivered into the conduits Nos. i and 2, through two 48-inch intake meters, and remeasured through ten selling or outlet meters, varying in size from 1 2 to 48 inches, with a difference of measurements between the two sets of meters of only y2 of i per cent. Considering only the months November, 1896, to July, 1897, during which performance of the meters was not interfered with by irregular " unmeasured drafts of water " for test- ing pipe lines, etc., it will be seen that 12,996,500,000 gallons of water were measured by the intake meters and remeasured by the selling meters, with a difference of only 17,600,000 gallons, or 14-100 of i per cent.

12-iNCH VENTURI METER TUBE, SPIGOT ENDS.

26

SETTING OF METER

The meter tube is set in the pipe-line, wherever most convenient. See Figures 5, 6, 7, 8 and 9. The register is usually placed ten feet or more below the hydraulic grade, and not more than 1000 feet from the tube. The tube and register are connected by two lines of y2 inch brass, lead or tin-lined pipe, and as a matter of economy are usually placed as near one another as possible.

The register must be properly protected from freezing, and when a gate-house, pumping-station or other building suitable for the purpose is not available a vault or register house must be provided. This should be frost proof, and not less than 6 ft. x 6 ft. inside; but in other respects may be built to suit the taste and requirements of the purchaser. Figures 12, 13 14, 15 and 16 illustrate a few that have been found entirely satisfactory. Drawings for that shown by Figure 14 will be furnished when desired.

When the meter must be placed where frequent readings cannot easily be obtained, the registrations may be automatically transmitted by electricity to a secondary or office dial, figure 17, which may be placed any distance from the register.

c

L

VENTURI METER

BUILDERS IRON FOUNm

FIGURE 17. SECONDARY OR OFFICE DIAL.

THE VENTURI WATER METER.

MANSFIELD MERRIMAN'S "HYDRAULICS." ARTICLE 71.

14 It has been shown by Herschel* that a compound tube provided with piezometers may be used for the accurate measurement of water. The apparatus, which is called by him the Venturi Water Meter, is shown in outline in the accompanying figure, and consists of a compound tube terminated by cylinders, into the top of which are tapped

jDATUM^PLANE

the piezometers Hi. and H ^ Surrounding the small sec- tion #2 is a chamber into which four or more holes lead from the top, bottom and sides of the tube, and from

* Transactions American Society of Civil Engineers, 1887, Vol. XVIII, p. 228.

which rises the piezometer Hz. The flow passing through the tube has the velocities vi, Vz, and v3 at the sections 0i, #2, and a3, and these velocities are inversely as the areas of the sections. When the pressure in a? is positive, the water stands in the central piezometer at a height H*, as shown in the figure; when the pressure is negative the air is rarefied, and a column of water lifted to the height hz. If E is the height of the top of the section a* above the datum, the value of Hz for the case of negative pressure was taken to be E — hz. The apparatus was constructed so that the areas ai and a3 were equal, while a2 was about 1-9 of these.

To determine the discharge per second through the tube, the areas a* and a* are to be accurately found by measurements of the diameters " ; then (the quantity pass- ing is equal to the area X the velocity or)

Q = #! i}it or Q = a* V?.

If no losses of head due to friction occur between the sec- tions a i and az, the quantity h' in the formula of the last article is o, and

o =

Inserting in this for vi and v* their values in terms of and then solving for Q, gives the result

which may be called the theoretic discharge. Dividing this expression by a* gives the velocity vt, and dividing it

t This equation is deduced from the well-known law that the sum of velocity and fric- tion heads is constant.

36

by a* gives the velocity v*. Owing to the losses of head which actually exist, this expression is to be multiplied by a co-efficient c\ thus:

a-2

is the formula for the actual discharge per second.

Reference is made to Herschel's paper, above quoted, for a full description of the method of conducting the experiments. The discharge was actually measured either in a large tank or by a weir; and thus q being known for observed piezometer heights Hi and //2,the value of c was computed by dividing the actual by the theoretic dis- charge. For example, the smaller tube used had the areas

ai = 0.77288, #2 = 0.08634 square feet; hence the theoretic discharge is

Q = 0.086884 ^ 2g(Hi— H* ), and the co-efficient of discharge or velocity is

•-•§

In experiment No. I the value of H* was 99.069, while //2 was 24. 509 feet, and the actual discharge was 4.29 cubic feet per second. As .fi'was 84.704, the value of H* is 60.195 feet. The theoretic discharge then is

2 = 0.086884 X 8.02 y/38.874 = 4.345.

Dividing 4.29 by this, gives for c the value 0.988. Fifty- five experiments made in this manner, in all of which negative pressure existed in a-2, gave co-efficients ranging

37

in value from 0.94 to 1.04, only four being greater than i.oi and only two less than 0.96.

The larger tube used had the areas ai = 57.823 and #2 = 7.074 square feet, and the pressure at the central piezometer was both positive and negative. Twenty-eight experiments give co-efficients ranging from 0.95 to 0.99, the highest co-efficients being for the lowest velocities. In this tube the velocity at the section #2 ranged from 5 to 34.5 feet per second. The small variation in the co-effi- cients for the large range in velocity indicates that the apparatus may in the future take a high rank as an accurate instrument for the measurement of water. Under low velocities, however, it is not probable that the arrange- ment of piezometers shown in the accompanying figure will give the best results ; in order that Hi may correctly indicate the mean pressure in #i, connection seems to be required both at the bottom and sides of the tube like that at a*. It is thought, moreover, that the elevation E should be measured to the centre of the section rather than to the top. The lower piezometer H3 is not an essential part of the apparatus and may be omitted, although it was of value in the experiments as showing the total loss of head.

U.C. BERKELEY LIBRARIES

U.C. BERKELEY LIBRARIES

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