Document npXrrzNg834r3dQYvowjV16GR

American Society of Heating and Ventilating Engineers Guide, 1931 Table 6. Comparative Capacity of Steam Lines at Various Pitches* Pitch of Pipe in Inches per 10 Ft. Pitch or Pipe--in. H nr. 1 IN. lHm. 2 IN. 3 IN. Pipe Sice Inches Sq. Ft Rad. Based on 240 B.tu. 2 si Sq. Ft Rad. Based on 240 B.tu. > 4 s So. Ft Rad. Based on 240 B.t.u. 2 a a Sq. Ft. Rad. Based 00 240 B.tu. > i s Sq. Ft Rad. Based on 240 B.tu. :> sa Sq. Ft Rad. Based on 240 B.tu. Max-Vel. 4 IN. 5 0! Sq. Ft Rad. SBased aon 240 B.tu. S Sq-Ft Rad. Baaed on 240 B.tq.. k 1 25.0 12 45.8 12 30.3 14 52.6 15 37.3 18 63.0 17 40.4 19 70.0 20 42.5 20 75.2 22 46.1 21 83.0 23 47.5 22 87.9 25 lH 104.9 18 117.2 20 133.0 23 144.5 2S 154.0 27 165.0 28 172.6 29 2 142.6 18 159.0 21 181.0 23 196.5 25 209.3 27 224.0 28 234.8 30 256.0 19 263.5 20 299.5 23 325.5 25 346.5 27 371.5 28 388.4 29 401.1 Table 7. Effect of Reaming Entrance to One-Inch One-Pipe Risers* Reamed entrances Rounded entrances... ........................................... Squared entrances......... ..................................... Three wheel cutter ... Single wheel cutter.- ............................................. Maximum Capacjtt op Rises 24.7 lb. per hour 23.9 lb. per hour 22.2 lb. per hour 19.2 lb. per hour 17.6 lb. per hour Pas Cb.vt Decsease 0.0 3.2 10.1 22.2 28.7 Table 8. Per Cent Difference in Capacity Due to Variation of Pipe Sue and Smoothness* Maximum Condensation, Lb. per H*. Size of Pipe.. Minimum___ Maximum..... Per Cent Variation____ K" 14.00 15.20 8.6 1' 24.89 30.08 20.8 IK" 45.42 52.08 14.7 IK" 70.50- 82.00 16.3 Data from American Society of Heating and Ventilating Engineers Research Laboratory. steam must be kept below the point where it will seriously interfere with the returning water. The maximum allowable velocity of steam for satis factory operation has been determined by the American Society of Heating and Ventilating Engineers Research Laboratory: Table 5 gives the maximum allowable capacity and velocities of flow for up-feed one-pipe risers while Table 6 gives \he maximum capacity and velocity for horizontal pipes with various pitch. Since the maximum velocity must not be exceeded in any part of the system, if silent and satisfactory operation are desired, care should be exercised to eliminate obstructions due to poor pipe, lack of or faulty reaming and improper use of pipe dope. Tables 7 and 8 give the variation in capacity of pipe due to reaming and variation in size and smoothness of pipe as determined by experiments at the American Society of Heating and Ventilating Engineers Research Laboratory. There are certain variations in manufacture which apparently cannot be avoided, which actually caused a 20 per cent variation in the capacity of a 1 in. pipe, as indicated by Table 8. A factor 158 Chapter 10--Piping for Steam Heating Systems f :. . . heen allowed in all of the capacity tables in this chapter so of safety ., interesting, need not be used to discount the other that Table , table*' . q is to be used in designing one-pipe systems up to 200 ft. T, t lpnirth of run. For designing larger one-pipe systems where equivalent 8 . of steam to all parts of the building is difficult to SSTnE 10 shall be used. Fig. 2. Typical Air-Vent One-Pipe Down-Feed Steam System to it as for the up-feed system: The branches may leave the overhead main from the top, in which case the condensation drains at the end, or the branches may leave the overhead main from the bottom, in which case each branch drains the condensation, and in which case the instal lation of eccentric fittings in the overhead main may be avoided. The illustration indicates no drain at the base of the main supply riser: When this risei* is more than very few feet from the boiler a connection from the bottom of the riser into the wet return should be made. Air-Vent Two-Pipe System Two-pipe systems, Fig. 3, require separate supply and return mains and a separate supply and return connection for each heating unit. Like one-pipe systems, they require air valves on heating units and mains. The connection may be either at the top or the bottom of the unit, but the outlet is always at the bottom so that all condensation will drain through this to the return mains instead of back through the inlet con nection to the supply mains, as with the one-pipe system. Both radiator connections, should be valved. 159'