Optimizing Pumping Systems to Minimize First or Life-cycle Cost

Numerical optimization methods offer a powerful new technology for pump users when combined with pumping system analysis software. Whether the design goal is to reduce first costs or life-cycle costs, this technology promises to significantly reduce pumping system costs and energy usage. Optimization methods work by automatically selecting pipe and pump sizes to minimize cost. Design engineers define the constraints for the system, such as flowrate, NPSH margin, or fluid velocity. The optimization software then finds the combination of pipe and pump sizes to minimize the cost while satisfying the constraints. A new design concept is introduced called the optimal pumping system operating point (OPSOP). In simple terms, the OPSOP uses cost data to identify the optimum tradeoff in pipe, pump, and (optionally) energy costs for a system that may have one or more duty points. Using this information, a new and improved method of pump sizing is described. To establish benchmark comparisons for typical petrochemical pumping systems, these optimization methods were applied to four previously designed systems. With a modest amount of effort, first cost reductions were as much as 17 percent, and life-cycle cost reductions were as much as 72 percent (based on 10 years), with savings of over $100,000 in several cases.