A 20 HP motor drives a Cornell Model 2.5WH centrifugal pump. The pump discharges

Question

A 20 HP motor drives a Cornell Model 2.5WH centrifugal pump. The pump discharges at 320 gpm into a 2.5 in nominal OD steel schedule-40 line. The pump suction is 35 kPa below standard atmospheric pressure. The friction head loss to the system is 3.3 m. The pump efficiency is 73%. The suction and discharge lines are at the same elevation. Determine the dynamic head available, recommended impeller diameter, and NPSHR.

Model 2.5WH: 3600 RPM-60 Hertz Speed Impeller Dia. Style Solids Dia. Ns Suction Discharge No. vanes 3525 VARIOUS ENCLOSED .50" 1357 3 2.5 5 SINGLE VOLUTE MOUNTING CONFIG CC, VM, F, VF, EM, VC Clear Liquid Pump -70 225 -60 a 200 150 40 Z 125 55 DIA F30 100 H 75 10 100 200 CAPACITY U.S. GALLONS PER MINUTE 100 125 CUBIC METERS PER HOUR Feet x .305 Melers MAXIMUM IMPELLER DIAMETER inches x25.4 Millimeters GPM x 227 Cubic Meters/Hour FOR FULL FOR FULL MOTOR LOAD GPM x 3.785 Liters/Minute MOTOR LOAD PLUS 15% SF B (6.44) 15 B+ (6.88) C (5.88) 10 C (5.50) D+ (5.31) 7.5 D (4.88) Performances shown are for Cool Water, Close-Coupled Electric configuration with Packing. other mounting styles or liquids may require horsepower and/or performance adjustments. Cornell Pump company Portland, oregon CORNELL

Explanation / Answer

dynamic head available = (2.5 * 3.3 * 40)/(5.65)

                                      = 58.4

recommended impeller diameter = (20 * 106 * 2.5)/(35000 * 10000)

                                                   = 0.1428 m

NPSHR   =   (14 * 0.73 * 5)/60

              = 0.851

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