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 ages ystem. 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. 2 g - 64.33 = 0.433 lt> s - at 62 F. = Column of Mer- 231 cubic ins. 0.1337 cubic foot. 8.335lbs.at62F. 3.786 litres. 7.480 gallons. 62.355 lbs.at62F. 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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