*4.1.2 Power savings via pump load management at a refinery product loading terminal*

The example refinery had multiple storage tanks for its various liquid products which had to be loaded onto ships at the dock about 5 km away. A schematic diagram is shown in **Figure 20**. All pumps were equal-sized with 3550 rpm fixed-speed motors and no flow control valves.

The original design basis assumptions were:


**Figure 20.** *Flowsheet for product loading station at a refinery.*


During the optimization study, the reality was found to be quite different. Each ship has its own max loading rate (to prevent capsizing), significantly less than the pump run-out flow rate (a case of oversizing). The system curve had low ΔP, which meant that the valve at the loading dock had to be severely throttled. The configuration resulted in a system which has an opportunity for significant power saving. The best solution turned out to be replacement of the existing 3550 rpm motors on 4 of the 5 pumps with dual-speed 3550/1770 rpm motors, and then apply load management techniques to match the pump network flowrate to the required ship loading rate. Total savings for a typical year worked out to be 76 kWh/1000 bbl of product shipped, about 68% savings compared to the previous operating policy. Until the 2-speed motor replacement project was approved, the no-cost savings from load management of the high full speed motors was estimated to be 30 kWh/ 1000 bbl, or 26% savings compared to the base case.
