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502 CHAPTER 21 1955 Guide Table 5. Steam Pipe Capacities for Low Pressure Ststems (Reference to this table will be by column letter A through L) This table is based on pipe size data developed through the research investigations of Tbb American Society op Heating and Ventilating Engineers. CAPACITIES OF STEAM MAINS AND RISERS Special Capacities fob Ons-Pipb Systems Only Pipe Size In. Direction of Compensate Flow in Pipe Line Radi. With tho Steam in One-Pipe and Two-Pipe Syatema ator Radi Against the Steam Supply Valves ator or 10* Drop 1 r-? or 10* Drop A psi or 1 Os Drop or 20* Drop l psi or 4 0* Drop 4 psi or 8 Os Drop Two-Pipe Only Vertical Hori zontal UpFeed Vertical Riser sec outs tions B CD B FG /0 J* K f Capacity Expressed in Square FeelE D R i 1 n 11 2 21 3 31 4 5 6 8 10 12 16 30 30| 39 46 56 87 100 122 134 155 190 273 315 386 449 518 635 822 948 1,160 1,230 1,420 1,740 1,740 2,010 2.460 3,210 3,710 4,550 5,280 6,100 7.460 11,00012,700 15.500 120,000|23,100 28,300 32,000:37,100 45.500 ,61,000 69,700j84,800 791 173 269 546 898 1,650 2,460 3,480 6,430 10,550 21,970 40,100 64,300 121,000 ! 111I 157 245 346 380 538 77ll 1,091 1,270! 1,800 2,330 3,290 3,470 4,910 4,910 6,950 9,090 12.900 14,900 21,100 31,070 43.900 56,700 80,200 91,000 1129.000 170,000 242.000 56 122 190 386 635 1,130 1,550 2,040 4.200 7.200 15.000 28.000 46.000 88.000 34 75 108 195 395 700 1.150 1,700 3.150 5,600 12,000 123.000 38.000 76.000 25 45 98 152 288 464 800 1,140 1,520 - - - 28 62 93 169 28 62 93 169 260 475 745 1,110 2,180 Capacity Expressed in Pounds per Hour _f 1 U H 2 21 3 31 4 5 6 8 10 12 ,16 8 10 12 14 22 25 31 34 39 48 68 79 97 112 130 159 206 237 307 355 435 502 806 922 1,320 1,52( 291 434 614 1,140 1,870 2.750] 3,170 3,880 5,010 5,790! 7,090 8,040 9,29011,400 15,100 17,400 21,200 20 43 67 137 225 411 614 869 1,610 2,640 5,490 10,000 16,100 30,300 28 61 95 193 318 581 869 1,230 2,270 3,730 7,770 14,200 22,700 42,400 8 40 14 9 87 31 19] 135 48 27 273 97 49 449 159 99 822 282 175 1,230 387 288 1,740 511 425 3,210 1,0501 788 5,280 1,800 1,400 11,000 3,7501 3.000 20,000 7,000 5,700 32,200 11,500 9,500 60,500 22,000 19.000 6| 11 7 20 16 38 23 72 42 116 200 286 380 7 7 16 23 42 65 119 186 278 545 All Horizontal Mains and Down-Feed Risen Mainn Dp- Feed Risers and UnI dripped Hun outs DpFeed Risers Radi ator Con nec tions Run outs Not DriPP I Note.--Steam at an average pressure of 1 psig is used as a basis for calculating capacities. Ali drops sbowa are *inDposni poet rus1e00Cfotloumf enquBivfaolrednrtorpusn--ofb1a/2se4door n1/p32ippeepi;rsoupbesrltyitureteamCeodlu. mn C or Column B as required. b Do not use Column J ior drop 1/32 psi except on sizes 3 in. and over; below 3 in. substitute Column c Pitch of horizontal runouts to risers and radiators should be not less than 1/2 in. per it. Where this PltcD cannot be obtained, runouts over 8 ft in length should be one pipe size larger than called for in Table a- Steam Heating Systems 503 critical velocities of the steam to permit the counter flow of condensate without noise. Return piping may be sized with the aid of Tables 6 and 7 where pipe capacities for wet, dry, and vacuum return lines are shown for the pres sure drops per 100 ft corresponding to the drops in Table 5. It is cus tomary to use the same pressure drop on both the steam and return sides of a system. Example 2: What pressure drop should be used for the steam piping of a system if the measured length of the longest run is 500 ft, and the initial pressure is not to be over 2-psig? Solution: It will be assumed, if the measured length of the longest run is 500 ft., that when the allowance for fittings is added, the equivalent length of run will not exceed 1,000 ft. Then, with the pressure drop not over one-half of the initial pressure, the drop could be 1 psi or less. With a pressure drop of 1 psi and a length of run of 1,000 ft, the drop per 100 ft would be j'a psi, while if the total drop were J psi, the drop per 100 ft would be -'o psi. In the first instance the pipe could be sized according to Column D for psi per 100 ft, and in the second case, the pipe could be sized accord ing to Column C for fi psi. On completion of the sizing, the drop could be checked by taking the longest line and actually calculating the equivalent length of run from the pipe sizes determined. If the calculated drop is less than that assumed, the pipe size is all right; if it is more, it is probable that there are an unusual number of fittings involved, and either the lines must be straightened or the column for the next lower drop must be used, and the lines resized. Ordinarily, resizing will be unnecessary. TABLES FOR PIPE SIZING FOR HIGH PRESSURE SYSTEMS Many of the recent installations of heating systems for large industrial type buildings have been designed for the use of high pressure steam, that is, without the use of pressure reducing valves. Such systems usually involve the use of unit heaters or large built-up fan units with blast heating coils. Pressures on these systems vary from 30 to 150 psi. Temperatures are controlled by a modulating or throttling type thermostatic valve con trolled by the air temperature in the room,, fan inlet or outlet. Tables 8 to 11 may be used for the sizing of steam and return piping for systems of 30 and 150 psi pressure at various pressure drops. These tables are based on Babcock's formula, and have been used as the basis of design for a number of years. SIZING PIPING FOR ONE-PIPE GRAVITY SYSTEMS Gravity one-pipe air-vent systems, in which the equivalent length of run does not exceed 200 ft, should be sized by means of Tables 5, 6 and 7 as follows: 1. For the steam main and dripped runouts to risers where the steam and condensate flow in the same direction, use ,'j-psi drop (Column /)). 2. Where the riser runouts are not dripped and the steam and condensate flow in Pposite directions, and also in the radiator runouts where the same condition occurs, use Column L. 3. For up-feed steam risers carrying condensate back from the radiators, use Lolumn J. 4- For down-feed systems, the main risers of which do not carry any radiator con densate, use Column H. 5- For the radiator valve size and the stub connection, use Column K. A- For the dry-return main, use Column U. 1 For the wet-return main, use Column T. On systems exceeding an equivalent length of 200 ft., it is suggested that the total drop be not over j psi. The return piping sizes should corre spond with the drop used on the steam side of the system. Thus, where 4?-psi drop is being used, the steam main and dripped runouts would be