If a VSD pump is used in Problem 8.5.1 above, determine the speed at which the pump should be run to maintain the flow rate of 3000 bbl/hr. The rated pump speed is 3560 RPM.

Problem 8.5.1

The origin pump station at Harvard on a 50 mile pipeline consists of two pumps in series, each developing 1450 ft of head at 3000 bbl/hr. Diesel fuel (specific gravity 0.85 and viscosity 5.9 cSt) is pumped from Harvard to a delivery terminal at Banning. The required discharge pressure at Harvard has been calculated to be 995 psi. The pump station suction pressure is maintained at 50 psi. Use a combined pump efficiency of 84% at the given flow rate.

(a) Analyze the pump station pressures and determine the amount of throttle pressure and HP wasted.

(b) If electrical energy costs 10 cents/kWh, estimate the dollars lost in control valve throttling.