Developing system head curves for closed systems

Development of system head curves is a relatively straightforward process for pumping systems that have a tank on both the suction and discharge side of the pump. However, because the current hydraulic models work on the basic premise that demands are fixed, such methods for creating system head curves do not produce accurate results for complex, closed systems with no discharge-side tank. In this article, the authors introduce a method developed to rectify this shortcoming. The model described in this article works by accurately capturing the relationship of pressure versus demand at water consumers' taps. Engineers and operators can use this model in selecting new pumps and identifying inefficiencies in existing pump operations. Comparisons of head curves for systems with and without discharge-side tanks indicated that head curves were steeper and exhibited wider variation for systems with no discharge-side tank, a factor that should be taken into consideration in both pump selection and setup of operational controls.