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HEATING VENTILATING AIR CONDITIONING GUIDE 1941 TABLES FOR PIPE SIZING2 Factors determining the size of a steam pipe and its allowable limit of capacity are the direction of the flow of condensate, whether against or with the steam. Tables 8 and 9 are based on the actual inside diameters of the pipe and the condensation of M 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 noticeable defects. Table 8 may be used for sizing piping for steam heating systems by 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 H 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, and L 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 S. 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-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 l'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 Ho lb, while if the total drop were H lb, the drop per 100 ft would be Ho lb. In the first instance the pipe could be sized according to Column D for He lb per 100 ft, and in the second case, the pipe could be sized according to Column C for H4 lb. 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. 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: ipipe gize 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 logical unit baseo 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. ' 274 CHAPTER 14. PIPING FOR STEAM HEATING SYSTEMS :: 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 of Heating and Ventilating Engineers. CAPACITIES OF STEAM MAINS AND ..RISERS Direction of Condensation Flow in Pipe Line Special Capacities fob One-Pipe Systems Onlt Pips With tiie Steam in One-Pipe and Two-Pipe Systems In. 1/s* lb or */j4 lb or Vi lb or HOb HOs 1 Os Drop Drop Drop Hlb or 2 0s Drop Hlb or 4 0s Drop Hlb ' or 8 Os Drop Against the Steam Two-Pipe Only Vertical Hori zontal Supply Risers Radiator Valves and Radiator and UpFeed Con nections Run outs AB C D B F G ffa /e Jb K ha M 30 l 39 46 56 79 iii 30 157 56 1H 87 100 122 173 245 346 122 1H 134 155 190 269 380 538 190 2 273 315 386 546 771 1,091 386 2H 449 518 635 - : 898 1,270 1,797 635 3 822 948 1,163 ` 1,645 2,326 3,289 1,129 3H 1,228 1,419 .1,737 2,457 3,474 4,913 1,548 4 1,738 2,011 2,457 3,475 4,914 6,950 2,042 5 3,214 3,712 4,546 6,429 9,092 12,858 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 80,171 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 -- 26 58 95 195 395 700 1,150 1,700 3,150 -- 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 Risers Up- Fced Risers Mains and Un dripped Run-. outs FUepedRisers Radiator Con- Run outs nections Dripped Note.--AH 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. $Convrlnht vj tu ^ American Societt Beating, Piping and of Heating and Ventilating Engineers Air Conditioning Contractors National Auodation 1j1 Not to be Reprinted With* out Special Permission 1. For the steam, main and dripped runouts to risers where the steam and condensate flow in the same direction, use Hs-lb 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. 3. For up-feed steam risers carrying condensation back from the radiators, use Column J. 4. For down-feed systems the main risers of which do not carry any radiator con densation, use Column H. 5. For the radiator valve size and the stub connection, use Column K. 6. For the dry return main, use Column U. 7. 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 lb. The return piping sizes should correspond with the drop used ori the steam side of the system. Thus, where H4-lb drop is being used, the steam main and dripped runouts would be sized from