Document OE9jLp5poLZ63wzqpV9L0wdmL

290 Chapter 15 1945 Guide I Table 4. Friction Heads (in Milinches) of Central CircularDiaphragm Orifices in Unions (One milinch equals 0.001 in.) Dukbtsh or- Orifices ------(IffCHKB) 2 Velocttt or Watsa in Pips ra Inches per Second 3| 4| 6 10 12 18 24 | 36 Pipe . 0.25 0.30 0.35 0.40 0.45 0.50 0.55 1300 650 330 170 2900 1450 740 380 185 5000 2500 1300 660 330 155 75 11,300 5700 2900 1500 740 350 170 .20,800 10,400 5200 2600 1300 620 300 32,000 16,000 8000 4000 2000 970 480 45.000 23,000 12,000 6800 2900 1400 700 57,000 26,000 13,000 6500 3200 1600 47,000 24,000 53,000 12,000 27,000 5700 13,000 2800 6400 0.35 0.40. 0.45 0.50 0.55 0.60 0.65 900 2000 3500 460 1000 1800 270 570 1000 160 330 580 190 330 200 120 1-in. Pipe 7800 4000 2300 1400 750 440 260 14,000 7200 4100 2300 1300 800 460 22,000 12,000 6400 3700 2200 1300 720 32,000 17,000 9300 5400 3000 1800 1100 37,000 21,000 12,000 7000 4200 2400 65,000 37,000 22,000 50,000 13,000 28,000 7400 17,000 4300 10,000 0.45 0.50 0.55 0.60 0.65 .0.70 0.75 1000 660 430 280 190 2250 1450 950 630 420 285 190 4000 2600 1700 1100 750 510 330 l\~in. Pipe 8900 5800 3800 2500 1700 1150 750 16,000 10,400 6800 4400 3000 2000 1300 25,000 16,400 10,500 6900 4700 3100 2100 36,000 23,000 15,000 10,000 6700 4500 3000 53,000 34,000 22,000 15,000 10,000 6700 60,000 40,000 27,000 60,000 18,000 40;000 12,000 26,000 0.55 0.60 0.65 0.70 0.75 0.80 0.85 850 600 . 400 260 - 180 1900 1300 850 600 400 300 200 3300 2300 1500 1100 760 540 380 iy&-in. Pipe 7400 5400 3600 2600 1800 1200 860 13,000 8600 7200 4400 3000 2200 1600 21,000 16,800 10,400 7000 5000 3200 2300 30.000 21.000 14,000 10,000 7000 5000 3000 50,000 30,000 21,000 14,000 10.200 7800 53,000 39,000 28,000 19,000 45,000 13,000 30.000 0.70 890 1850 3500 0.80 470 975 1800 O'. 90 . 255 560 1000 1.00 160 340 610 1.10 214 375 1.20 195 1.30 2-in. Pipe 7400 3900 2200 1320 850 460 275 14,000 7400 4200 2520 1600 950 525 22,300 11,700 6500 4000 2500 1360 980 33,000 17,000 9500 5800 3700 1910 1375 37,000 20.500 12,500 7900 4200 3100 38,000 23,000 49,000 14,000 30,000 8100 16,800 4400 8850 Not*.--The losses of head for the orifices in the and 2-in. pipe were calculated from those ih the smaller pipes, the calculations being'based on the assumption that, for any given velocity, the loss of head is a function of the ratio of the diameter of the pipe to that of the orifice. This had been found to be practically true in the tests to determine the losses of head in orifices in %-in., 1-in., and IH-in. pipe, con ducted by the Texas Engineering Experiment Station, and also in the tests to determine the losses of head in orifices in 4-in.. 6-in., and 12-in. pipe, conducted by the Engineering Experiment Station of the University of Illinois. (Bulletin 109, Table 6, p. 38, Davis and Jordan). FRICTION HEAD IN MILINCHES PER FOOT OF PIPE Hot Water Heating Systems and Piping 291- control of hot water circulation. :This improved performance-merits the small increase in operating cost necessary to circulate the water mechani cally. The velocities required should be determined by calculation for the particular system under consideration. Since forced circulation velocities are higher than those -in gravity systems, and since the friction heads in a heating system vary almost as the squares of the velocities, a given error in the calculation or assump tion of a velocity is less important in a forced circulation system than-in For other temperature drops the pipe capacities may be changed correspondingly. For example, with a temperature drop of 30 F, the capacities shown in this figure are to be multiplied by 1.5. a gravity circulation system, and, consequently, it is easier to design a satisfactory forced circulation system than a satisfactory gravity circu lation system. forced hot water systems, it is customary to use a temperature drop of 20 or 30 F between the water entering and leaving the boiler or other *}ea.tr- The head against which the system is to operate must then be inn i ' This varies from 2 to 5 ft for small systems and may rise to 100 ft on large jobs with a. group of buildings. For-iron pipe, the sizes