Chapter 8 - When two pumps are cheaper than one

Abstract

This chapter presents a case where two pumps are favored over a single pump on the basis of consideration of energy costs, projected maintenance costs, and capital cost. Alternatively, reliability may prove to be the deciding factor. Assuming that the correct pump was purchased for the service, initial hydraulic performance may be assumed to be comparable for each case, but may prove to be different in the longer term. The chance of a major mechanical seal failure or a major pump failure may also differ. These areas need to be reviewed before making the decision to purchase either one or two pumps for an application involving frequent flow variations of substantial magnitude. Further, a comparison of advantages and disadvantages of both two- and single-pump application should be reviewed before purchasing. Energy savings must be compared against any increase in capital cost for two smaller pumps instead of one large one, and also weighed against the projected maintenance costs. In addition, where reliability is of prime importance, two pump operations prove beneficial where a large flow fluctuation is required.