TABLE 9.-SHEWING THE WEIGHT OF A COLUMN OF WATER, OR THE LOAD TO BE OVERCOME IN PUMP-BARRELS, EXCLUSIVE 136 212 306 416 544 689 850 1029 1227 1436 1663 1663 2176 2754 3400 4895 120 368 500 199 200 153 ΠΟ 85 150 233 338 458 92 164 255 130 99 177 276 398 542 707 895 1105 1337 140 107 192 297 429 583 762 964 1190 1440 150 115 204 318 459 624 816 1033 1275 1543 1840 160 124 218 340 490 666 870 1102 1360 1646 170 130 232 362 520 707 925 1172 1445 180 138 245 383 552 749 979 1239 1530 146 259 404 582 792 1034 1308 1615 272 426 612 832 832 1089 1378 599 758 935 1132 1349 1580 1829 2393 3029 3740 5385 653 826 1020 1234 1472 1724 1996 2612 3304 4079 5874 1595 1867 2162 2829 3580 4419 6364 1717 2012 2328 3046 3855 3855 4759 6853 2155 2495 3264 4130 5099 7343 1963 2298 2662 2662 3482 4406 5439 7832 1748 2085 2442 2827 2827 3699 4681 5779 8322 1852 2208 2585 2993 3916 4956 4956 6119 8812 Perpen TABLE 10.-SHEWING THE QUANTITY OF WATER DISCHARGED PER MINUTE BY SINGLE-, DOUBLE-, AND TREBLE-BARREL PUMPS AT VARIOUS SPEEDS, EXCLUSIVE OF SLIP. The Rose at the bottom of the suction-pipe of a pump, for preventing the admission of small stones and rubbish, is generally either cylindrical, circular, or egg-shaped. The aggregate area of the perforations should be equal to from 1 to 2 times the area of the suction-pipe. TABLE 11.-SHEWING THE QUANTITY OF WATER IN GALLONS DELIVERED AT EACH STROKE OF A PUMP. 076 100 125 15 17 '20 *22 *25 *28 *30 $35 '4 *45 611 *764 '917 106 1'22 1'37 1'52 1.83 32 27 31 36 *40 34 4 *45 *20 24 27 *31 *34 *38 '41 *48 *55 •62 832 104 1.25 145 166 187 2:08 2.50 4956 .63 '71 '77 .85 '92 1'13 1.27 1'70 2.12 81 *92 1'02 I'12 1'22 142 163 1.83 2'44 3:05 3.67 125 138 152 166 1994 2.22 2:59 3.33 1.81 2'0 2.17 2:53 290 3.26 4'35 4:16 5:00 1963 190 217 244 272 14 36 2010 22 98 25.85 28.72 34'47 The Strength of Steam-Cylinders, Water-Cylinders, pipes, and tubes of all kinds subject to internal pressure, may be found by the following rules. In the case of steam cylinders, allowance must be made for wear and for boring and re-boring. Thickness of Metal for Pipes.-Rule: Multiply the working pressure inside the pipe in lbs. per square inch, by the internal radius of the pipe in inches, and divide the product by the safe working tension given in the table below for the material of which the pipe is made, to which quotient add the constant number C., and the result will be the thickness of the pipe in inches. The value of C. ranges from 13 to 10, according to circumstances, for cast-iron pipes for water, C. is 3; and for steampipes 5, the working pressure in each case being taken at 133 lbs. per square inch, to allow for contingencies in making stock sizes of pipes. Example required the thickness of a cast-iron pipe 8 inches in diameter, suitable for a working head of 300 feet water-pressure, or 133 lbs. per 133 lbs. pressure × 4 (radius of pipe) square inch, then = =212 + 3 2500 safe working tension of cast-iron =512 inches thickness. Bursting Pressure of Pipes.-Rule: Multiply the bursting tension. in lbs. per square inch-given in the table below-of the metal of which the pipe is made, by the thickness of metal in inches, and divide the product by the internal radius of the pipe in inches, the result will be the bursting pressure in lbs. per square inch, Example, required the bursting pressure of the 8-inch pipe given in the last example, then, 15000 bursting tension X 512 thickness of pipe 1920 lbs. bursting pressure. 4 inches internal radius of pipe TABLE 12.-STRENGTH OF MATERIALS FOR PIPES FOR THE ABOVE RULES. CAST-IRON SOCKET-PIPES FOR WATER. Pipes should be cast from good grey metal, twice run, of such quality that a bar of the same 2 inches deep x 1 inch thick placed upon supports 3 feet apart will not break with a less load than from 28 to 30 cwt. suspended at the centre, which weight will cause a deflection of about inch. Strength of Metal.-The tenacity of the cast-iron of which pipes are usually made, averages 15000 lbs. per square inch, which divided by the factor of safety, 6, gives a working strength of 2500 lbs. per square inch. Thickness of Metal of Pipes.-Besides making the thickness sufficient to bear the water pressure, allowance must be made for hydraulic shocks due to the closing of cocks, &c., as well as for the strain due to weights falling upon, or passing over them after they are laid underground; the following two rules are used by makers of water-pipes, both of which give good and nearly the same results. Rule 1.-Multiply the internal diameter of the pipe in inches by the working head in feet, divide the product by 10,000, and add the constant number, 30, to the result, which will give the thickness of metal (cast-iron) in inches. Rule 2.-Multiply the working pressure in lbs. per square inch by the internal radius of the pipe in inches, and divide the product by the working strength of the metal 2500, then add the constant number 30 to the result, which will give the thickness of the metal of the pipe in inches; this constant number is added for the allowance to be made for shocks, &c., mentioned above, and may be varied to suit circumstances. The Depth of Socket is varied a little by different iron founders; a good proportion is to make the inside depth according to the following rule. Multiply the internal diameter of the pipe by 13, and add the constant number 3 to the result. The space for the lead joint should be inch for small pipes, inch for medium-sized pipes, inch for large pipes, and inch for very large pipes. Testing Pipes.-Pipes should be tested to double their working pressure-but not beyond that otherwise the metal is liable to be strained and weakened; and, while under pressure, they should be struck moderately hard with a hammer to represent the shocks they will be subject to after being laid underground. Deviation in thickness and weight.—A deviation in thickness of inch for small, and inch for medium sized, and for large sizes, is sometimes permitted, and a deviation in weight of about 1 lb. per inch in diameter is permitted. Weight of Socket-Pipes.-The weights of ordinary sizes of pipes for water are given in Table 13. The first two sizes are suitable for a working head of 100 feet water pressure, the 1 to 9-inch pipes are suitable for 150 feet water-pressure, and the pipes above that size are suitable for a working head of 300 feet water-pressure the proof strain being double these quantities. |