Document VJn9dk3NKpV8bGLgRD8Jmvvng

HEATING VENTILATING AIR CONDITIONING GUIDE 1943 Table 4. Friction Heads (in Milinches) of Central Circular Diaphragm Orifices in Unions (One triilinch equals 0.001 in.) Diameter OP Velocity op Water in'Pipe in Feet per Minute - (Inches) 10 15 20 | 30 | 40 | 50 | 60 j 90 | 120 | 180 %-in. Pipe 0.25 0.30 0.35 0.40 0.45 0.50 0.55 1300 2900 5000 11,300 20,800 32,000 45,000 650 1450 2500 5700 10,400 16,000 23,000 57,000 330 740 1300 2900 .5200 8000 12,000 26,000 47,000 170. 380 660 1500 2600, 4000 6800 13,000 24,000 53,000 185 330 740 1300'., 2000 2900 6500 12,000 27,000 155 350 620, 970 1400 3200 5700 13,000 75 170 300 480 700 1600 2800 6400 0.35 0.40 0.45 0.50 0=55 0.60 0.65 1-in. Pipe 900 2000 3500 7800 14,000 22,000 32,000 460 1000 1800 270 570 1000 4000 2300 7200 12,000 17,000 37,000 65,000 4100 6400 9300 21,000 37,000 160 330 580 1400 2300 3700 5400 12,000 22,000 50.000 190 330 750 1300 2200 3000 7000 13,000 28.000 200 . 440 , 800 1300 1800 4200 7400 17.000 120 260 460 720 1100 2400 4300 10.000 0.45 0.50 0.55 0.60 0.65 0.70 0.75 1000 2250 660 1450 430 950 280 . 630 190 420 285 190 4000 2600 1700 1100 750 510 330 l)i-in. Pipe 8900 16,000 '25,000 36,000 5800 10,400 16,400 23,000 53,000 3800 6800 10,500 15,000 34,000 60,000 2500 4400 6900 10,000 22,000 40,000 1700 3000 4700 6700 15,000 27,000 60,000 1150 2000 3100 4500 10,000 18,000 40,000 750 1300 2100 3000 6700 12,000 26,000 0.55 0.60 0.65 0.70 0.75 0.80 0.85 850 1900 3300 600- 1300 2300 400 850 1500 260 600 1100 180 400 760 300 540 200 " 380 llfain. 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 1 28,000 19,000 45,000 13,000 30,000 0.70 . 890 0.80 470 0.90 255 1.00 160 1.10 1.20 1.30 1850 3500 975 1800 560 1000 340 610 214 '375 * 195 S-in. Pipe 7400 3900 2200. 1320 850 . 460 275 14,000. 22,300 7400 11,700 4200 6500 2520 4000 . 1600 2500 950 , 1360 525 980. 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 "The losses of head for the orifices in the 1 M-in. and 2-in. pipe were calculated from those in 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 le-in., 1-in., and 1W-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-ul, and 12-m; pipe.'conducted by the Engineering Expeririient' Station of the University of Illinois, (BidUttn 109, Table 6, p. 38, Davis and Jordan). 318 CHAPTER 16. HOT WATER HEATING SYSTEMS AND PIPING . highest radiator and be protected against freezing. Closed tanks are generally placed in the basement oyer the boiler. A relief yalve installed on a closed tank will not operate often provided the tank is of adequate size. It is essential that the relief valve be kept in good condition to eliminate any possible failure when operation is necessary. INSTALLATION DETAILS Items that should be considered in the design of this type of system are: All piping must be so pitched that all air in the system can be vented either through, an open expansion tank, radiators or automatic relief valves. All piping must be arranged so that the entire system can be drained. Sections of piping individually valved shall have corresponding drain valves. In large buildings, the piping may be zoned according to exposure of building, usage of building, or method of control. All piping must be installed so that it is free to expand and contract with changes of temperature without producing undue stresses in the pipes pr connections.. For. this purpose it is generally sufficient to allow for a variation in length of 1 in. for 100 ft of pipe. The pipe system should'be designed so that each circuit has its correct friction head for balanced water distribution. This may be done by change of pipe size or change in piping detail. The connections from the boiler to the mains should be short and direct, to reduce the - friction head and allow for expansion. It is frequently possible to avoid an elbow and to reduce the length of the pipe by running the pipe in a diagonal direction, either in a .horizontal or in a vertical plane. . .. . The mains and branches .should pitch up and away from'the heater, generally not less than 1 in. in 10 ft: The connections from mains to branches and to risers should be such that circulation through the risers will start in the right direction. Hence, in a one-pipe system the flow connection must be nearer the heater than the return connection. In a correctly- ' designed two-pipe system, the pressure in the' flow main is higher than that in the return main, and a slight variation in.the distances of the flow and return connections from the heater is not material; but it is generally best .to have the two connections about equally distant from the heater. . ' , ......... Generally, connections to risers or radiators are taken out of the top of mains either 319