You have to select a pump to transfer benzene from the reboiler of a distillation column to a storage tank at a rate of $250 \mathrm{gpm}$. The reboiler pressure is $15 \mathrm{psig}$ and the temperature is $60^{\circ} \mathrm{C}$. The tank is $5 \mathrm{ft}$ higher than the reboiler and is at a pressure of $25 \mathrm{psig}$. The total length of piping is $140 \mathrm{ft}$ of $2 \mathrm{in}$. sch 40 pipe. The discharge line from the pump contains 3 gate valves and 10 elbows, and the suction line has 2 gate valves and 6 elbows. The vapor pressure of benzene at $60^{\circ} \mathrm{C}$ is $400 \mathrm{mmHg}$.

(a) Using the pump curves shown in Figure 8.2, determine the impeller diameter to use in the pump, the head that the pump would develop, the power of the motor required to drive the pump, and the NPSH required for the pump.

(b) If the pump is on the same level as the reboiler, how far from the reboiler could it be located without cavitating?

Figure 8.2

Transcribed Image Text:

Size 2 3 R & C 1% in. Pedestal 3500 rpm 4' minimum NPSH 400 Impeller dia. 300 200 8% in 8% in 7% in 7% in 6% in. 6% in. I Total head feet 100 50 MISSION VALVE AND PUMP COM Semi-open impeller Dia. 6%-8% in. Eye area 9.8 in. Curve 8 S1 20 ft Max. sphere 1% in. Maximum normal capacity for slurries and abrasive fluids 7ft 30% 10ft. 140% 15 ft 145% 50% 50 50 40HP 15 HP 20 HP 30 HP1 25 HP 25ft, 50% 45% 60 HP 50 HP 400 40% 500 600 700 Capacity-U.S. gallons per minute 100 200 300