Document XO0qwmyO49G5xBXVn8ZD2ygxg

American Society of Heating and Ventilating Engineers Guide, 1924-25 back against the flow of steam, 'and if it is not certain that the velocity is below the critical limit, the pipe should be provided with a separate drip. The following tables for the carrying capacities of pipes as used in steam heating installations with the exception of dry returns have been de termined by Unwin's formula for the flow of steam in pipes which reads as follows: where W - Weight of steam flowing through the pipe in lb. per min. P ~ Difference of pressure between the two ends of the pipe. C = Density of steam in lb. per cu. ft. d -- Actual inside diameter of pipe. L = Length of pipe in feet. This formula with the capacity expressed in sq. ft. of radiation on the basis of each sq. ft. of radiation with connected piping condensing 0.3 lb. of steam per hour will be as follows: = 17,400 y P C d where R -- Sq. ft. of radiation. L (d + 3.6) Capacities of dry returns have been calculated by the Chezy formula for flow in open conduits which is expressed in the form Q = dcyrs where Q = Discharge in cu. ft. per sec. a ~ Wet area of pipe in sq. ft. r = Hydraulic mean depth (areas of wet cross-section divided by the wet-perimeter.) c = Constant from Kutter's formula. s = Slope or grade. In the tables for one-pipe, two-pipe and vapor systems without the use of thermostatic traps the tables have been calculated on the basis of the water occupying one-eighth the area of the pipe while for vapor systems using thermostatic traps the capacity is based on water occupying threesixteenth the area. All supply mains, branches to riser, when dripped, where steam and condensation flow in the same direction, and supply risers (with the exception of up-feed one-pipe risers), are based on a pressure drop of loz. per 100 ft. length of pipe or equivalent. All supply mains, branches to risers, not dripped where condensation and steam are flowing in opposite directions and up-feed one-pipe risers are based on a velocity.of 16 ft. per second. 40 American Society of Heating and Ventilating Engineers Guide, 1924-25 Branches to radiators 5 ft. in length or less are based on velocities from 10 to 19 ft. per second depending on the size of branch while branches to radiators 5 to 10 ft. in length are based on a velocity of approximately 10 ft. per second. Wet returns are calculated on a drop of Yi oz. per 100 ft. length of pipe or equivalent. Radiator valve sizes for one and two-pipe gravity systems are based on standard practice. An allowance must be made for ells and fittings in the line of flow by adding the number of feet given in Table 27 to the straight run of pipe plus 25 ft. for entrance to last radiator to obtain the total equivalent length. TABLE 27. FLOW OF STEAM IN PIPES P=Loss in pressure in lb. d=Inside diameter of pipe in inches L = Length of pipe in feet D=* Weight of 1 cu. ft. steam W=Lb. of steam per min. / P D d* W= 75 Vo / 3.6\ W L P = . 000131 [1 + d J D d* Col. 1 IN OZ. 1 2 3 4 s 6 7 8 10 12 14 16 20 24 28 32 40 48 80 160 320 480 S7.5-A/---yj ioo 2.175 3.076 3.767 4.350 4.863 5.328 5.754 6.152 6.878 7.532 8.138 8.700 9.727 10.655 11.509 12.290 13.756 15.069 19.454 27.512 38.863 47.652 Dia. Pipe 1 im va 2 2A 3 3M 4 iA 5 6 7 8 9 10 12 14 16 Col.* 2 1 4/. . 3.6 l1+-r 0.522 1.177 1.828 3.709 6.109 11.183 16.705 23.630 32.098 43.719 69.718 105.35 150.33 205.37 271.16 437.51 733.90 925.19 -- --:...... Press By Gage 0.0 0.3 1.3 2.3 5.3 10.3 15.3 20.3 30.3 40.3 50.3 60.3 75.3 100.3 125.3 150.3 175.3 _20_0_.3 ___ -- Col. 3 W/ yd 0.193 0.195 0.201 0.207 0.223 0.248 0-. 270 0.290 0.326 0.358 0.388 0.415 0.452 0.507. 0.557 0.603 0.645 0_._68_5 . ___ ___ -- Length Pips in Feet 20 40 60 80 100 120 140 160 180 200 250. 300 350 400 450 500 600 700 800 900 1000 1400 Col 4 wY1 100 -- 2.240 1.580 1.290 1.120 1.000 0.912 0.841 0.793 0.741 0.710 0.632 0.578 . 0.538 0.500 0..477 0.447 0.407 0.378 0.354 0.333 0.316 0.267 Column 1 X 2 X 3 X 4 = lb. steam per min. will flow through a straight pipe for a given condition. Example.--X oz. drop -- 2-in. pipe -- 1.31b. press. -- 100 ft. long -- 2.175 X 3.709 X 0.201 X 1 = 1.615 lb. per min., then 1.615 X 60 - 20 per cent = 77.28 lb. per hr. 41