Document RJ2GDw05mZrBoOEJ70kkQwVa8

T a b le 9. R eturn Pip e Capacities Capacity Expressed in Square Feet of Equivalent Direct Radiation (Reference to this table w ill be b y column le tte r U through B E ) I' : CAPACITY OF RETURN MAINS AND RISERS This table is based on pipe size data developed through the research investigations of the A' merican Society op H sating ANP'VHNTiLATiNc_ ENcmBgRS. '~ HEATING VENTILATING AIR CONDITIONING CUIDE 1940 296 C opyright { *> R e p rin te d W ith o u t S pecial P e rm issio n CHAPTER 16. PIPING FOR STEAM HEATING SYSTEMS Column C; radiator runouts and undripped riser runouts from Column L; uo-feed risers from Column J; the main riser on a down-feed system from Column C (it will be noted that if Column if is used the drop would exceed the limit of Hi lb); the dry return from Column R; and the wet return from Column Q. With a J^-lb drop the sizing would be the same as for Hi lb except that the steam main and dripped runouts would be sized from Column B, the main riser on a down-feed system from Column B, the dry return from Column 0, and the wet return from Column N. Table 10. Pipe Sizes for One-Pipe Up-feed System Shown in Fig. 2 Pabt or SrsTEM Branches to radiators.. Branches to radiators.. Riser________________ Riser..-......................... Riser_........................-- Branch to riser............ Supply main------------Branch to supply main Dry return main.......... Wet return main.......... Wet return main_____ Wet return main......... Section or Pip ___ atob b to c ctod d to e e to / /tog g to h h toj f to * k to m mton n to p Radiation Supplied (SqFt) Tbeoebtical Pipe size (Inches) Practical Pips bob (Inches) 100 2 2 50 m 1M 200 2 2 300 2H 2H 400 2H 2H 500 3 3 600 3 3 600 3H 3H 600 3 3 600 2H 3 600 l H '2 600 1 2 600 1 2 600 1 2 ni ^ nu Fig. 2. Riser, Supply Main and Return Main of One-Pipe System /. s' Example S. Size the one-pipe gravity steam system shown in Fig. 2 assuming that this is all there is to the system or that the riser and run shown involve the longest run on the system. Solution. The total length of run actually shown is 215 ft. If the equivalent length of run is taken at double this, it will amount to 430 ft, and with a total drop of H lb the drop per 100 ft will be slightly less than He lb. It would be well in this case to use Hi lb, and this would result in the theoretical sizes indicated in Table 10. These theo retical sizes, however, should be modified by not using a wet return less than 2 in. while the main supply, g-h, if from the uptake of a boiler, should be made the full size of the main, or 3 in. Also the portion of the main k-m should be made 2 in. if the wet return is made 2 in. Notes on Gravity One-Pipe Air-Vent Systems 1. Pitch of mains should not be less than H in. in 10 ft. 2. Pitch of horizontal runouts to risers and radiators should not be less than H lo in 10 ft. Where this pitch cannot be obtained runouts over 8 ft in length should be one size larger than called for in the table. 3. In general, it is not desirable to have a main less than 2 in. The diameter of the far end of the supply main should not be less than half its diameter at its largest part. 4. Supply mains, branches to risers, or risers, should be dripped where necessary. 297