TANKS AND CISTERNS.
Fig. 593.
A tank is an artificial receptacle for liquids, thus: a tank engine is one which carries the water and fuel it requires, thereby dispensing with a tender; tank-iron or steel is common plate used in building tanks. Steel is cheaper than sheet-iron. A cistern is primarily a natural reservoir—a hollow place containing water; more commonly an underground reservoir or tank. Closed pressure tanks are usually cylindrical shells similar to a horizontal steam boiler, having bumped or rounded heads to save bracing. Closed pressure tanks are used extensively in connection with hydraulic elevators; the requisite pressure for these was formerly derived from an open tank installed upon the roof of the building, but the closed pressure tank, located in the engine room, now very generally takes the place of the open tank.
A closed pressure tank is shown in Fig. [596] in use with a hydraulic elevator.
A reservoir is a place where water is collected and kept for use when wanted, so as to supply a fountain, a canal or a city by means of aqueducts or to drive a mill-wheel or the like.
Fig. 594.
A receiving reservoir is a principal reservoir into which an aqueduct or rising main, delivers water and from which a distributing reservoir draws its supply.
A graduated tank is one fitted with water gauges and indicating marks, at different heights, between which, the capacity of the tank is shown.
A ship’s ballast tank is the compartment for water to be pumped in and out for the purpose of insuring the proper stability of the vessel, to avoid capsizing and to secure the greatest effectiveness of the propelling power.
Fig. 595.
A vat is a cistern or tub, especially one used for holding liquors in an immature state, as chemical preparations and tanning liquor for leather. Fig. [594].
A tub is an open wooden vessel formed with staves, bottom and hoops; a kind of short cask, half barrel or firkin, usually with but one head. Fig. [595].
A gallon (U.S.) is equal to 231 cubic inches or 0.13368 cubic feet and weighs 81⁄3 lbs. nearly, (i.e. 8.3356). This is almost exactly equivalent to a cylinder 7 inches in diameter and 6 inches in height.
The imperial gallon of England contains 277.274 cubic inches, and is equivalent to 1.2 U.S. gallons and at 62° Fah. weighs 10 lbs.
A cubic foot contains 74805⁄10000 (71⁄2 nearly) U.S. gallons, and weighs 62355⁄1000 (621⁄3 nearly) lbs.
A barrel = 311⁄2 gallons. 1 hogshead = 2 bbls. = 63 gallons.
The strength of a tank is of the first importance; 2351⁄2 gallons of water weigh as much as a ton of coal, but unlike the latter, it presses in all directions. Immense losses both of life and property have been caused by the “bursting” or giving way of tanks; particularly of those of a considerable size and elevation.
Fig. 596.
Note.—Tank Valves. The “Corcoran” valve is made for either side or bottom outlet and for 1, 11⁄4, 11⁄2, 2 and 21⁄2 inch pipe; its action is automatic; the pull by which it is operated is controlled by a ratchet. This valve closes the pipe inside the tank. It thus becomes easy to empty the pipes in order to prevent freezing. The hoops, lugs and lock nut nipples are important parts of a well constructed tank. The foundations upon which tanks are supported should be carefully considered, as the average weight of a well made tank, when full of water, is about five tons to 1000 gallons.
The following table gives the capacity of round tanks or cisterns for each 12 inches in depth, if the tank is 24 inches deep instead of 12 inches, the result would be, twice the number of gallons.
Table.
| DIAM. | GALL. |
|---|---|
| 25 feet | 3671 |
| 20 „ | 2349 |
| 15 „ | 1321 |
| 14 „ | 1150 |
| 13 „ | 992 |
| 12 „ | 846 |
| 11 „ | 710 |
| 10 „ | 587 |
| 9 „ | 475 |
| 8 „ | 376 |
| 7 „ | 287 |
| 61⁄2 „ | 247 |
| 6 „ | 211 |
| 5 „ | 147 |
| 4 „ | 94 |
| 3 „ | 53 |
| 21⁄2 „ | 36 |
| 2 „ | 23 |
The contents of cisterns and tanks are estimated either in gallons or in cubic feet. The weight of water in any cistern or tank can be ascertained by multiplying the number of gallons by the weight of one gallon, which is 81⁄3 pounds, 8.333. For instance, taking the largest cistern in the above table containing 3671 gallons: 3671 × 8.33 = 30579.43 lbs. (nearly).
If the cistern is rectangular, the number of gallons and weight of water are found by multiplying the dimensions of the cistern to get the cubical contents. For instance, for a cistern or tank 96 inches long, 72 inches wide, and 48 inches deep, the formula would be: 96 × 72 × 48 = 331,776 cubic inches.
As a gallon contains 231 cubic inches; 331,776 divided by 231 gives 1,436 gallons, which multiplied by 8.33 will give the weight of water in the cistern. Fig. [594].
For round cisterns or tanks, the rule is: Area of bottom on inside multiplied by the height, equals cubical capacity. For instance, taking the last tank or cistern in the table: area of 24 inches (diameter) is 452.39, which multiplied by 12 inches (height) gives 5527.6 cubic inches, and this divided by 231 cubic inches in a gallon gives 23 gallons. Fig. [595].
Rule for obtaining the contents of a barrel in gallons. Take the diameter at the bung, then square it, double it, then add square of head diameter; multiply this sum by length of cask, and that product by .2618 which will give volume in cubic inches; this, divided by 231, will give result in gallons.