Document MGk2pXJOXKbyVyGb485gyVZVV

American Society of Heating and Ventilating Engineers Guide, 1924-25 quantity of water is the pressure necessary to overcome friction in the pipes (when horizontal) plus the static pressure when the discharge is higher than the supply. Table 95, column 1, gives the vertical rise in feet to any fixture up to 150 ft. in height; column 2, gives the static head in lb. per sq. in. corre sponding with the vertical rise. The underlying principle involved in determining the proper pipe sizes for mains, risers and branches is to so regulate the size of these pipes that they will carry the maximum amount of water required of them and absorb by friction and static head, all the pressure at the source and still deliver water at the fixture in sufficient quantity but at a pressure prac tically equalling zero or slightly above except that due to velocity of flow through the fixture. Table 92 gives the amount of water in gallons which should flow per minute for the number of fixtures indicated of each different type, together with the branch pipe size necessary to carry this amount of water with a pressure drop of 30 lb. per 100 ft. of run. The volume of water required per fixture is reduced as the number <jf fixtures in each group is increased, to take care of the factor of probable use. In estimating the pipe size for any part of a riser in a building of several stories, take 60 per cent of. the water to be used on any floor and 411 floors above as determined from Table 92 and deduct 10 per cent for each floor above. This reduction in estimated amount is to take care of probable use. Thus, if 100 gallons are used on each floor of a 10-story building the size or pipe will be determined as follows: TABLE 93. WATER RISERS FOR MANUFACTURING BUILDINGS, LOFT BUILDINGS. APARTMENT HOUSES, HOTELS Pipe Size with 10 Lb. Drop 10 41 6 10 5 10 * 3 * 10 2 " 10 * 1 * 100 gal. 200 x 0.60 300 x 0.60 400 x 0.60 500 x 0.60 600x0.60 700 x 0.60 800 x 0.60 900 x 0.60 1000 x 0.60 60% 60 90% - 108 80% - 144 70% - 168 60% = 180 50% = 180 40% - 184 40% - 192 40% - 216 40% = 240 ' ' -- . 2" 2 H" 2H" 3" 3' 3' 3* 3' 3' 3' Note.--For residences, use Table 92, and for the main supply use 25 per cent of total of gallons used by fixtures and then take pipe size from Table 94 on a basis of 10 lb. pressure drop per 100 ft. or less if water supply pressure is less than 50 lb. The pressure drop of 30 lb. per 100 ft. of run will give satisfactory results for branches on the top floor but a higher pressure drop can be used on floors below corresponding with the pressures as given in Table 94 which show that for a building 100 ft. in height, a pressure drop of 100 lb. can be used on the fixture branches and that for a building 50 ft. in height, a pressure drop of 75 lb. can be used on the fixture branches; Table 92, however, can be used with safety on any of the floors but will give pipe sizes larger than necessary for the lower floors in a very tall building. 162 American Society of Heating and Ventilating Engineers Guide, 1924-25 TABLE 94. PIPES MAY BE SIZED FOR GIVING ANY DESIRED PRESSURE DROP PER 100 FT. OF RUN Friction Pressure Drop Lb. per Sq. In. per 100 Ft. Run H Pipe Sizes in Inches 1 IH m 2 2^ 3 3% 4 Gallons per Minute 5 7 50 75 5.4 11 19 30 62 109 171 252 353 6.4 7.6 10.8 13.2 15.0 -17.0 13 15 22 27 31 35 23 27 38 47 54 60 36 74 129 203 298 418 43 88 154 242 357 499 61 125 218 343 504 706 76 153 267 420 618 864 86 176 308 485 714 998 96 197 345 542 800 1115 21.0 24.0 27.0 30.0 43 49 55 60 74 85 96 105 117 242 136 278 152 311 166 341 423 665 978 1365 485 769 1130 1578 544 858 1260 1765 598 939 1380 1930 TABLE 95. SHOWING WATER PRESSURE REQUIRED TO DELIVER WATER TO TOP OF VERTICAL RISER WITH 15 LB. PRESSURE AT THE TOP BRANCH Vertical. Rise or Water from Main to Highest Fixture Branch Static Head in Lb. per Sq. In. Water Pressure in Lbs. Required to Deliver Water to Top of Riser with 15 Lb. Terminal Pressure 5 Lb. : Pressure Drop per 100 Ft. 7 Lb. 10 Lb. 20 Lb. 0 0 15 . 15 15 4.33 20.5 20.7 21 20 8.66 25 25.4 26 30 40 50 12.99 17.32 21.65 29.5 35 39.5 30.1 35.8 40.5 31 37 42 25.99 44 45.2 47 70 so 30.32 34.65 49.5 54 50.9 55.6 53 58 100 no 120 130 38.98 43.31 47.64 51.97 56.30 58.5 64 68.5 73 77.5 60.3 66 70.7 75.4 80.1 63 69 74 79 84 140 60.63 83 85.9 90 150 64.96 87.5 90.5 . 95 110 Note.--The water pressures given in above table are the pressures at the base of the riser, necessary to deliver water to top of riser with a terminal pressure of 15 lb., when discharging the number of gallons per minute called for in Table 94, at the pressure drop indicated. The following examples show how to use Table 94: Example.--What are the sizes required for mains and branches in a building 100 ft. high, supplied with a water pressure of 75 lb. per sq. in. with 100 gal. of water per minute required on each floor? This is worked out in Table 93 and gives the pipe sizes for the main riser with a 10 lb. drop for 100 ft. of run and shows that a 3 in. main, reduced to 2 in., would be required: branches to the various groups of fixtures can be taken from Tables 94 and 95. On the top floor it will be necessary to use, a 1J4 in. branch to carry 75 gal. per min. with a pressure drop of 30 lb. but that at 50 ft. vertically from the supply, a t'A in. branch pipe will carry 74 gal. per minute, therefore 1)4 in. pipe could be selected for this branch. Assuming that the pressure drop in the main riser is 10 lb. per 100 ft. run and the pressure drop on the top flqor in the branch does not exceed 15 lb. in all and the static head for building 100 ft. as given in column 2 of Table 95 is 43.31 lb. making a total of 58.31 lb. ; it wjJI be seen that 75 lb.--58.31 lb., which equals 16.59 lb., is the amount of pressure over and above that required, and that this pressure can be utilized to overcome the triction drop in the main feed line running from the source of supply to the base of the riser. From Table 93 it is found that 240 gal. per min. will flow at the first floor, and assuming that tms water supply is to be brought in a main 300 ft. long; Table 94 will show that a oyb tn. supply would be necessary. 163 .