A circulating pump takes hot water at $85^{\circ} \mathrm{C}$ from a storage tank, circulates it through a piping system at a rate of $150 \mathrm{gpm}$, and discharges it to the atmosphere. The tank is at atmospheric pressure, and the water level in the tank is $20 \mathrm{ft}$ above the pump. The piping consists of $500 \mathrm{ft}$ of $2 \mathrm{in}$. sch 40 pipe, with one globe valve upstream of the pump and three globe valves and eight threaded elbows downstream of the pump. If the pump has the characteristics shown in Figure 8.2, determine

Figure 8.2

(a) The head that the pump must deliver, the best impeller diameter to use with the pump, the pump efficiency and NPSH at the operating point, and the motor horsepower required to drive the pump

(b) How far the pump can be located from the tank without cavitating

Properties of water at $85^{\circ} \mathrm{C}$ : viscosity $=0.334 \mathrm{cP}$, density $=0.970 \mathrm{~g} / \mathrm{cm}^{3}$, vapor pressure $=433.6 \mathrm{mmHg}$.

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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