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Heating Ventilating Air Conditioning Guide 1939 TABLES FOR PIPE SIZING2 Factors determining the capacity are as follows: 1. Pipe condensate flowing with steam. 2. Pipe condensate flowing against steam. 3. Pipe and radiator condensate flowing with steam. 4. Pipe and radiator condensate flowing against steam. It is apparent that (3) and (4) are practically limited to one-pipe systems while (1) and (2) cover all other systems. Tables 8 and 9, worked out for determining pipe sizes, have their col umns lettered continuously, Columns A through L being in Table 8, and M through EE in Table 9. In the following text, reference made to columns will be by letter. The tables are based on the actual inside diameters of the pipe and the condensation of lb (4 oz) of steam per square foot of equivalent direct radiation3 (abbreviated EDR) per hour. The drops indicated are drops in pressure per 100 ft of equivalent length of run. The pipe is assumed to be well reamed without unusual or notice able defects. Table 8 may be used for sizing piping for steam heating systems by1 determining the allowable or desired pressure drop per 100 equivalent feet of run and reading from the column for that particular pressure drop. This applies to all steam mains on both one-pipe and two-pipe systems, vapor systems, and vacuum systems. Columns B to G, inclusive, are used where the steam and condensation flow in the same direction, while Columns II and I are for cases where the steam and condensation flow in opposite directions, as in risers and runouts that are not dripped. Columns J, K, andL are for one-pipe systems and cover riser, radiator valve. and vertical connection sizes, and radiator and runout sizes, all of which are based on the critical velocities of the steam to permit the counter flow of condensation without noise. Sizing of return piping may be done with the aid of Table 9 where pipe capacities for wet, dry, and vacuum return lines are shown for the pressure drops per 100 ft corresponding to the drops in Table 8. It is customary to use the same pressure drop on both the steam and return sides of a system. Example 2. What pressure drop should Jbe 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-lb gage? 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 lb or less. With a pressure drop of 1 lb and a length of run of 1,000 ft, the drop per 100 ft would be Yo lb, while if the total drop were 'A. lb, the drop per 100 ft . *Pipe size tables in this chapter have been compiled in simplified and condensed form for the convenience of the user; at the same time all of the information contained in previous editions of The Guide has been retained. Values of pressure drops, formerly expressed in ounces, are now expressed in fractions of a pound. As steam system design has materially changed in recent years so that 240 Btu no longer expresses the heat of condensation from a square foot of radiator surface per hour, and as present day heating units have different characteristics from older forms of radiation, it is the purpose of The Guide to gradually eliminate the empirical expression square foot of equivalent direct radiation. EDR, and to substitute a iogical unit based on the Btu. The new terms to express the equivalent of 1000 Btu (Mb), and 1000 Btu per hour (Mbn), have been approved by the A.S.H.V.E. 314 Chapter 16. Piping for Steam Heating Systems , be Ho lb. In the first instance the pipe could be sized according to Column D for 4h per IIX) f*i and *n t^ie secon<? case, the pipe could be sized according to Column C K* lb On completion of the sizing, the drop could be checked by taking the longest for 7*4 a*ctuaiiy calculating the equivalent length of run from the pipe sizes determined. to*e.a calculated drop is less than that assumed, the pipe size is all right; if it is more, it is II j!abie that there are an unusual number of fittings involved, and either the lines must P^rtiahtened or the column for the next lower drop must be used and the lines resized. gd&y resizing will be unnecessary. Table 8. Steam Pipe Capacities Capacity Expressed in Square Feet of Equivalent Direct Radiation (Reference to this table will be by column letter A through L) This table is based on pipe size data developed through the research investiga tions of the American Society op Heating and Ventilating Engineers. CAPACITIES OF STEAM MAINS AND RISERS Direction or Condensation Flow in Pipe Line With the Steam io Ooe-Pipe and Two-Pipe Systems Pipe Vs* lb */*4 lb Vie lb HIb Mlb Mlb Two-Pipe Only Vt Os HOt 1 Oz Drop Drop Drop 2 Oz 4*0z Drop . Drop 8 0s Drop Vertical Hori* zontal AB C D B F G Io %` 30 - 30 1 39 46 56 79 in 157 56 26 Wi 87 100 122 173 245 346 122 58 134 155 190 269 380 538 190 95 2 273 315 386 546 771 1,091 386 195 2Vs 449 518 635 898 1,270 1,797 635 395 3 822 948 1,163 1,645 2,326 3,289 1,129 700 3M 1,228 1,419 1,737 2,457 3,474 4,913 1,548 1-.150 4 1,738 2,011 2,457 3,475 4,914 6,950 2,042 1,700 5 3,214 3,712 4,546 6,429 9,092 12,858 3,150 6 5,276 6,094 7,462 10,553 14,924 21,105 8 10,983 12,682 15,533 21,967 31,066 43,934 10 20,043 23,144 28,345 40,085 56,689 80j171 12 32,168 37,145 45,492 64,336 90,985 128,672 16 60,506 69,671 84,849 121,012 169,698 242,024 -- -- Special Capacities for One-Pipe Systems Only Risers UpFeed Radiator Radiator and Conneclions Riser Run- : /b K Lc 25 45 98 152 288 464 799 1,144 1,520 20 20 55 55 81 81 165 165 260 475 745 1,110 2,180 - AQ Horizontal Mains and Down-Feed Risen Up. Feed Risers Mains and Un dripped Run- outs Up. Feed Risers Radiator Con- nections Run outs Not Dripped Mote.--All drops shown are in pounds per 100 ft of equivalent run--based on pipe properly reamed. "Do not use Column H for drops of 1/24 or 1/32 lb; substitute Column C or Column B as required. bDo not use Column J for drop of 1/32 lb except on sizes 3 in. and over; below 3 in. substitute Column B. On radiator runouts over 8 ft long increase one pipe size over that shown in Table 8. f A orCopyright uerican Society Heating and-Ventilating Engineers I Not to be Reprinted Wlth- 1 Beating, Piping and Air Conditioning Contractors National Association f out Special Permission ONE-PIPE GRAVITY AIR-VENT SYSTEMS One-pipe gravity air-vent systems in which the equivalent length of run does not exceed 200 ft should be sized as follows: 1. for the steam main and dripped runouts to risers where the steam and condensate now in the same direction, use drop (Column D). 2. Where the riser runouts are not dripped and the steam and condensation flow in opposite directions, and also in the radiator runouts where the same condition occurs, use column L.