A commercial steel pipe is being designed to transport liquid benzene at 185°F to a heat exchanger at a flow rate of 850 gpm. The fittings, valves, supports, and pump are estimated to cost 6 times the installed pipe cost per ft. Annual maintenance is estimated to be 1.5% of the installed pipe and hardware initial costs per ft. For this service, the ASME pipe classification is determined to be 400 and a sch-80 pipe is required. The pump in the system runs 18 hours per day, 260 days per year. The efficiency of the pump is estimated to be 62%. The cost of electrical energy to run the pump is $0.11/kWh. The pipeline is expected to have a 45-year life. An engineering economic analysis reveals that the rate of return due to the investment in the pipeline is 16%. Use an estimated escalation rate of 2% to account for yearly inflation.

a. Determine the economic diameter and specify the standard pipe size that results in the minimum system cost if the design work was done for an installation that occurred in 2014.

b. Determine the economic velocity of the fluid (ft/s).

c. Construct the cost curves for this scenario assuming that the friction factor can be assumed constant at the value computed for the economic diameter from part (a). Your plot should look similar to Figure 4.8.

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Annual cost (S/ft) 70 60 50 40 30 20 10 0 0.3 0.35 0.4 0.45 0.5 D (ft) FIGURE 4.8 Cost curves for the pipe system described in Example 4.12. COT 5 32 WE 0.55 0.6 0.65 0.7