Steam:
Its Generation and Use

■4 FLOW OF STEAM THROUGH PIPES. The approximate weight of any fluid which will flow in one minute through any given pipe with a given head or pressure may be found by the following formula: W — 300 /i /^ (A - A) d’- in which //z= weight in pounds avoirdupois, d — diameter in inches, D — density or weight per cubic foot; pr the initial pressure, p.> pressure at end of pipe, and L — the length in feet. The following table gives, approximately, the weight of steam per minute which will flow from various initial pressures, with one pound loss of pressure through straight smooth pipes, each having a length of 240 times its own diameter. For sizes of pipe below 6-inch, the flow is cal- culated from the actual areas of “standard” pipe of such nominal diameters. The resistance at an elbow is equal to % that of a globe valve. These equivalents—for open- ing, for elbows, and for valves,— must be added in each instance to the actual length of pipe. Thus a 4-in. pipe, 120 diameters (40 feet) long, with a globe valve and three elbows, would be equivalent to 120 + 60 + 60 + (3 X 40) = 360 diameters long ; and 360 -s- 240 = It would therefore have lbs. loss of pressure at the flow given in the table, or deliver (1 -s- -j/i^ = .816), 81.6 per cent, of the steam with the same (1 lb.) loss of pressure. FLOW OF STEAM FROM A GIVEN ORIFICE. Steam of any pressure flowing through an opening into any other pressure, less than three- fifths of the initial, has practically a constant velocity, 888 feet per second, or a little over ten miles per minute; hence the amount discharged in pounds is proportionate to the weight or dens- ity of the steam. To ascertain the pounds, TABLE OF FLOW OF STEAM THROUGH PIPES. c Diameter of Pipe in inches. Length of each 240 diameters. tue cr □ V) u. % 2 3 4 . 5 6 8 ’° 12 '5 ■8 Initi by lbs. p Weight of Steam per minute in pounds, with one pound loss of pressure. 1 1.16 2.07 5-7 10.27 T5-45 25-38 46-85 77-3 115-9 211.4 341-i 502.4 804 1177 10 1 -44 2-57 7-1 12.72 19.15 3T-45 58-05 95 8 143.6 262.0 422-7 622.5 996 1458 20 1.70 3-02 8.3 14.94 22.49 36-94 68.20 112.6 168.7 307.8 496-5 731-3 1170 1713 30 i.91 3-4° 9-4 16.84 25-35 41-63 76.84 126.9 190.1 30 8 559-5 824. i 1318 1930 40 2.10 3-74 i". > 18.51 27.87 45-77 84-49 139-5 209.0 38i-3 615-3 906.0 ’45° 2122 50 2.27 4-°4 11.2 2O.OI 30.13 49.48 9I-34 150.8 226.0 412.2 665.0 979-5 1567 2294 60 2-43 4-32 II.9 21.38 32.19 52-87 97.60 t6i . i 24I-5 440-5 710.6 1046.7 1675 2451 70 2.57 4-58 12.6 22.65 34-1° 56.00 103.37 170.7 255-8 466.5 752-7 1108.5 1774 2596 80 2.71 4.82 *3-3 23-82 35.87 58.91 108.74 179-5 269.0 490-7 791.7 ii66.i 1866 2731 90 2.83 5'°4 J3-9 24.92 37 -52 61.62 113-74 187.8 281.4 513-3 828. i 1219.8 1951 2856 100 z-95 5-25 14-5 25.96 39-07 64.18 118.47 195-6 293.1 534-6 862.6 1270.I 2032 2975 170 3.16 5-63 15.5 27.85 4I*93 68.87 I27.12 209.9 3J4'5 573-7 925.6 J3^3-3 2181 3193 150 3-45 6.14 17.0 3° -37 45.72 75-°9 138.61 228.8 343-° 625.5 1009.2 1486.5 2378 3481 For horse-power, multiply the figures in the table by 2. For any other loss of pressure, mul- tiply by the square root of the given loss. For any other length of pipe, divide 240 by the given length expressed in diameters, and multiply the figures in the table by the square root of this quotient, which will give the flow for 1 lb. loss of pressure. Conversely dividing the given length by 240 will give the loss of pressure for the How given in the table. The loss of head due to getting up the velocity, to the friction of the steam entering the pipe, and passing elbows and valves, will reduce the flow given in the tables. The resistance at the open- ing, and that at a globe valve, are each about the same as that fora length of pipe equal to 114 diameters divided by a number represented by t (3.6 -i- diameter). For the sizes of pipes given in the table, these corresponding lengths are : I 1 I I 2 l 2^ I 3 I 4 I 5 I 6 I 8 I 10 I X2 I 15 I i! 20 I 25 I 34 I 41 I 47 I 52 I 60 I 66 I 71 I 79 I 84 I 88 i 92 I 9^ avoirdupois, discharged per minute, multiply the area of opening in inches, by 370 times the weight per cubic foot of the steam. (See p. 49 .) Or the quantity discharged, per minute, may be approximately found by Rankine’s formula : W — 6 a p -r- 7 in which W— weight in pounds, a=area, in square inches, and p — absolute press- ure. The theoretical flow requires to be mul- tiplied by >{1 = 0.93, for a short pipe, or 0.63 for a thin opening, as in a plate, or a safety valve. Where the steam flows into a pressure more than the pressure in the boiler: IF— 1.9 a k 3/ (/> — 8) b; in which 8 = differ- ence in pressure between the two sides, in pounds per square inch, and a, p and k as above. To reduce to horse-power, multiply by 2. Where a given horse-power is required to flow through a given opening, to determine the nec- essary difference in pressure : 8 = 2 H.P.2 i4«a k 73