Document G5VQBRoqg72kQ303g9DYXGp4r

American Society of Heating and Ventilating Engineers Guide, 1932 the counter-flowing steam and water may produce objectionable sounds, water hammer, or may retain water in some parts of the system until pressure goes off. The velocity at which such disturbance takes place depends upon the size of the pipe, its position (whether vertical or hori zontal), its pitch and the quantity of water flowing counter to the steam. Table 5. Maximum Allowable Capacities of Up-Feed Risers for One-Pipe Low Pressure Steam Based on A. S. H. V. E. Research Laboratory Tests Pips Sob Inches A i Hi tx 2 2X 3 3X 4 Velocity Feet per Second Pressure Drop Ounces per 100 Ft. B 14.1 17.6 20.0 23.0 26.0 29.0 31.0 32.0 C 0.68 0.66 0.66 0.57 0.54 0.48 0.44 0.39 Sq. Ft Radiation D 45 98 152 288 464 799 1144 1520 Capacity B.Lu. per Hour 10.961 23,765 36,860 69,840 112,520 193,600 277,000 368,000 Lb. Steam per Hour F. 11.3 24.5 . 38.0 72.0 116.0 199 .'8 286.0 380.0 INSTRUCTIONS FOR USING TABLE 5 1. Capacities given in Table 5 should never be exceeded on one-pipe risers. 2. Capacities based on X lb. condensation per square foot equivalent radiation and actual diameter of standard pipe. 3. All pipe should be well reamed and free from constrictions. Fittings should be up to size. (See ' Tables 7 and 8). Table 6. Comparative Capacity of Steam Lines at Various Pitches Pitch of Pipe in Inches per 10 Ft. XPitch op Pipe-- in. K ra. 1 IN. Pipe Site Inches Sq. Ft. Rad. Based on 240 B.Lu. > a 2 Sq. Ft. Rad. Based on 240 B.Lu. *>S $ 2 Sq. Ft. Rad. Based on 240 B.Lu. Max.Vel. Max-Vel. IK w- Sq. Ft. Rad. Based on 240 B.Lu. 2 IN. 3 IN. Sq. Ft Sq. Ft Rad. Based 'o > Rad. Based on 240 on 240 B.Lu. B.Lu. 4 IN. 5 IN. iSq. Ft. Rad. Based on 240 B.Lu. *>3 i a Sq. Ft. Rad. Based on 240 B.Lu. X 25.0 12 30.3 14 37.3 18 40.4 19 42.5 20 46.1 21 47.5 22 49.3 23 1 45.8 12 52.6 15 63.0 17 70.0 20 75.2 22 83.0 23 87.9 25 90.2 26 IK IK 2 104.9 18 117.2 20 133.0 23 144.5 25 154.0 27 165.0 28 172.6 29 178.2 31 142.6 18 159.0 21 181.0 23 196.5 25 209.3 27 224.0 28 234.8 30 242.6 31 236.0 19 263.5 20 299.5 23 325.5 25 346.5 27 371.5 28 388.4 29 401.1 30 "Data from A.S.H.V.E. Research Laboratory. Buildings which are heated intermittently or which have less heating . surface than is required for quick initial warming prior to occupancy, must have extra large piping in order to compensate for the unusual demand on the piping per unit of radiation. Chapter 9--Steam Heating Systems and Pipe Sizes Reaming 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 of safety has been allowed in all of the capacity tables in this chapter so that Table 8, while interesting, need not be used to discount the other tables. Pipe Size Tables Tables for the selection of pipe sizes for steam heating systems have been developed through the cooperative research investigations of the Table 7. Effect of Reaming Entrance to One-Inch One-Pipe Risers Maximum Capacity op Riser 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 Per Cent Decrease 0.0 3.2 10.1 22.2 28.7 Table 8. Per Cent Difference in Capacity Due to Variation of Pipe Size and Smoothness Maximum Condensation, Lb. per Hr. Size of Pipe....................................... X' 14.00 15.20 . 8.6 1" 24.89 30.08 20.8 \X" 45.42 52.08 14,7 IX' 70.50 82.00 16.3 aData from American Society of Heating and Ventilating Engineers Research Laboratory. American Society of Heating and Ventilating Engineers and the Heating and Piping Contractors National Association. (See Tables 9 to 16). While these tables, literally followed out, will serve as an efficient guide to the designer, it is impossible entirely to eliminate the factor of good engineering judgment. For example: While a given main might be calculated to begin at 5 in. and to end at 1^2 in., better practice often would make it begin at 4 in. and end at 2)4 in., since the dryer steam and higher, velocity at the entry would compensate for the smaller size at the end. DESIGN OF STEAM HEATING SYSTEMS Steam heating systems may be broadly classified as (1) air-vent onepipe, (2) air-vent two-pipe, (3) vapor and (4) vacuum. The choice of air-vent one-pipe, two-pipe, vapor or vacuum return line systems depends upon the requirements as to first cost, convenience, 139