Document MGQwvnvVE1599qjxmzG1DnGqV

American Society of Heating and Ventilating Engineers Guide, 1924-25 especially with widely fluctuating loads as the efficiencies of centrifugal boiler feed pumps drop off very rapidly for the smaller sizes of pumps and for low load conditions. For this reason centrifugal pumps are not usually employed for installations of less than 1000 b.hp. For small capacities screw pumps may be successfully used for greater economy. CONDENSATION RETURN PUMPS Condensation return pumps are generally of two classes: 1. Automatic pumps and receivers. 2. Continuous operation non-automatic return pumps. AUTOMATIC PUMPS AND RECEIVERS The volumetric capacities of receivers should be from 2 to 5 times the maximum minute volumetric flow of condensation to be handled, meas ured between the high and low water lines in the receivers for electric driven pumps and much smaller for steam driven pumps. The piston speeds in feet pier minute should not be more than 10 times the square root of the number of inches in the length of stroke. The volumetric displacement rate of water pistons should be 3 or more times the maximum volumetric rate of. the flow of condensate to be handled. The normal capacities for centrifugal pumps should be 2 or more times the maximum rate of flow of the condensation to be handled. CONTINUOUS OPERATION NON-AUTOMATIC RETURN PUMP The volumetric displacement rate of water pistons should be not less than 2 times the maximum rate of flow of the condensation to be handled. Piston speeds in feet pier minute should not be . more than 10 times the square root of the number of inches in the length of stroke. The quantities of condensate to be handled from direct radiation, direct-indirect radiation and indirect or fan blast radiation can be esti mated as follows: The normal capacity of pumps should be based on condensate at a temperature of not over 180 deg. fahr. For temperature of condensate above 180 deg. fahr. capacity should be increased above that estimated for 180 deg. fahr. condensate as per Table 58. TABLE 58. TEMPERATURE OF CONDENSATE AT PUMP SUCTION Deg. fahr. 190 200 204 Factor 1.15 1.56 2.00 78 American Society of Heating and Ventilating Engineers Guide, 1924-25 TABLE 59. CENTRIFUGAL RETURN PUMPS WITH RECEIVERS Size of Pump Discharge Inches 1 iA 2 Receiver Capacity Gallons 40 60 100 Sq. Ft. Direct Radiation 12,000 25,500 42,000 Lbs. Condensate per Hour 4000 8500 14,000 H. P. TO Drive i iA 2 Total Head Ft. 25 50 50 TABLE 60. CHARACTERISTICS OF CENTRIFUGAL PUMPS AND RECEIVERS DELIVERING AGAINST 15 LB. Sl2E 101 102 103 104 105 Sq. Ft. Equivalent Direct Radiation Gal. per Min. 8000 16,000 26,000 40,000 65,000 11 22 35 60 90 R. P. M. 1725 1725 1725 1140 1140 Actual H. P. 0.4 0.6 0.8 1.0 1.4 ' H. P. Motor Supplied % Va. i ' iA 2 Floor Space 5' 3"x3' 8" 5' 3'x3' 8" 6' 5"x3'8' V 6"x4' 2" V 6ffx4' 2" Shipping Weight 700 700 750 1050 1100 TABLE 61. SIZES. SPEEDS. HORSE-POWERS AND CAPACITIES ELECTRIC MOTOR DRIVEN CONDENSATION RETURN PUMPS Rating in Sq. Ft....................... Discharge Pressure, Lb--........ Gallons per Min........................ H. P. Motor............................... R. P. M. 60 Cycle and D. C... R. P. M. 25 Cycle.................... Shipping Weight--.................. 0 to 2000 10 20 33 AA 1700 1700 1440 1440 330 350 2000-4000 10 20 66 AA 1700 1700 1440 1440 350 370 4000-8000 10 20 10 10 AA 1700 1700 1440 1440 420 440 8000-16000 10 20 20 20 . AA 1700 1700 1440 1440 535 565 TABLE 62. MOTOR DRIVEN CONDENSATION PUMP CAPACITIES FOR DELIVERING AGAINST VARIOUS PRESSURES Radia tion in Sq. Ft. of Direct Radia tion Minimum Gallons per Mm. Maximum Boiler Motor Pressure H. P. Lb. 4000 4000 4000 6-8 6-8 6-8 10 15-40 50-60 A A A 6000 6000 6000 9-12 9-12 9-12 10 15-40 50-60 A A 1 8000 8000 8000 8000 10,000 10,000 10,000 10,000 10,000 12-16 12-16 12-16 12-16 15-20 15-20 15-20 15-20 15-20 10 15 20 30-60 10 15 20-30 3040 50-60 A A l lA A A l \A 2 Sug gested Size of Piping Inches i i 1 m iA m lA iA iA m lA m iA lA m Radia tion in Sq. Ft. of Direct Radia tion Minimum Gallons per Min. Maximum Boiler Pressure Lb. Motor H. P. 15,000 15,000 15,000 15,000 15,000 20,000 20,000 20,000 20,000 20,000 25,000 25,000 25,000 25,000 25,000 30,000 30,000 30,000 30,000 25-30 25-30 25-30 25-30 25-30 30-40 30-40 30-40 30-40 30-40 40-50 40-50 40-50 40-50 40-50 50-60 50-60 50-60 50-60 10 15 20-30 40 50-60 10 15 20 30-40 50-60 10 15 20 30-40 50-60 10 15 20 30-60 A l lA 2 3 A 1 2 3 5 1 m 2 3 5 1 iA 2 5 Sug gested Size of Piping Inches 2 2 2` 2 2 2 2 2 2 2 2A 2A 2A 2A 2A 2A 2A 2A : 2A