Document O1kL7VZBBgYyeEZp1VmgwkBMv

American Society of Heating and Ventilating Engineers Guide, 1929 ratio as the system increases in capacity, in accordance with Table 13. It should be noted that while water capacities of pumps for fan blast heaters are to be based upon their equivalent in direct radiation the air capacities for this class of radiation may be considerably less than that corresponding to this equivalent. The air capacity measurement of a vacuum heating pump should be made at a point in the main vacuum return line close to and before it enters the pump strainer, while the pump is in operation, under the Table 12. Receiver Tank Capacities for Centrifugal or Rotary Vacuum Heating Pumps '. Sq. Ft. Equivalent Direct Cast Iron Radiation Total Receiver Tank Capacity in Gallons Receiver Tank Capacity between High and Low Water Limits where Automatic Water Line Control is Used. 8,000 16,000 26,000 40,000 65,000 100,000 28 33 40 49 63 80 20 24 29 35 47 63 vacuum specified at the pump suction and while handling the quantity of condensate specified at a temperature not exceeding 180 deg. fahr. Air test in general may be made with water at lower temperatures; these determinations shall be made by means of a standard test orifice located in an inlet connection to the pump suction, consisting of a plate y8 in. thick with a reamed hole having sharp edges and of a diameter corresponding to the capacity of the pump. Table 13. Air Capacities for Vacuum Heating Pumps Sq. Ft. Direct Equivalent Radiation Surface 8,000 . 16,000 26,000 40,000 65,000 100,000 150.000 300,000 Diameter Orifice Vac. 10 in. 9* 64 A" y*r. h" Vi" VT A" Three (3) W Air Capacity Cu. Ft. per Min. 5 9 15 19 34 60 80 180 Fig. 3, may be used to give the quantity of air handled, corresponding to several sizes of orifices and different degrees of vacuum to be met. The water capacity of vacuum heating pumps, when operating against 8 in. of mercury vacuum, should be not less than 2A lb. of water per hour per square foot of equivalent cast-iron direct radiation, based upon condensate at a temperature of not over 180 deg. fahr. when the pump is delivering water against a specified gage pressure at the water discharge of the pump. For pumps handling both air and. water the above water capacity must be delivered when the pump is maintaining a vacuum.of -8 in. of mercury and handling air through a standard orifice corresponding to the air capacity of the pump as herein specified. 296 Chapter XVIII--Pumps and Traps for Heating and Ventilating Equipment In estimating the water capacity no additional allowance need be made for covered mains or risers, but exposed mains or risers used as heating surfaces should be included in computing the equivalent square feet of direct radiation. Steam driven vacuum pump size determination should take into con sideration the following variables: (a) The degree of tightness of system, (6) the efficiency of the radiator traps, (e) the temperature of the condensate at the pump, (d) the probable cooling effect of the return piping, (e) the use of lift points in the return, (/) vacuum to be maintained at the pump, (g) introduction of large volumes of high temperature water into the return piping near the pump, (h) the use of long runs of piping from the source of steam supply to the farthest radiator. High-pressure traps should not discharge directly into a vacuum return because of the vapor formfed by the re-evaporation of a part of the hot condensation. Fig. 4 shows one method which may be used for disposing of the greater part of the vapor of re-evaporation. Table 14. Direct Double Acting Steam Driven Reciprocating Vacuum Pumps Diameter in Inches Water Cylinder Condensation Lb. per Hr. for Pumps with Stroke Equal to Bore Direct Cast Iron Radiation Served . .. Pipe Sizes . Steam Suction In. In. Discharge In. Pumps Having Unequal Stroke and Bore Stroke -7* Bore Capacity Factor 3 510 1700 m. 2.50 1.58 4 5 1047 1830 3490 6100 A A 2va : .1 IX 2.25 2:00 1.48 1.38 6 2890 9633 A va- VA 1.90 1.34 7 4250 . 14,166 X VA-1 1.80 1.31 8 5920 19,733 % 3-3A 2' 1.75 1.29 9 7980 26,600 H 3A-* 2 1.70 1.27 10 10,350 34,500 l 4-iA W 1.67 1.25 12 16,300 54,333 l 4A-S 3A 1.60 1.23 14 24,000 80,000 iX 5-6 3 i.50 1.10 16 33,500 111,666 - 1M 6^7 3A 1.40 1.15 18 45,000 150,000 lH 7 4 1.33 1.13 20 58,500 195,000 1A 7-8 4A 1.30 1.12 22 74,300 247,666 2 8 m 1.25 1.10 24 92,300 317,666 2 8-10 5 1.20 1.08 26 112,800 376,000 m 10 28 135,800 452,666 VA 12 30 161,300 537,666 VA. 12 32 189,600 632,000 3 14 34 221,000 736,333 3, 14 36 254,000 846,666 3 14 '6 6 ;6 . -7 ... 7. 8 1.10 1.00 0.90 0.80 0.75 0.70 1.04 1.00 0.96 0.91 0.89 0.87 . 0.67 0.85 0.60 0.82 0.50 0.78 Note I.---The capacities given in Table 14 are for pumps having water cylinder with the length of stroke equal to the diameter of the water piston. Note 2.--The capacities for pumps of a greater or less length of stroke may be found by use of the last two columns in this table as follows: Divide the stroke by the piston diameter and find the corresponding ratio in the column headed stroke bore. The capacity factor opposite this in the last column is then multiplied by the capacity .given in the table to give the capacity of the pump in question. iVo/< 5.--When reciprocating pumps discharge against a head exceeding 5 lb. per square inch the pump stroke should exceed the bore to reduce the ill effect of clearance.' 297