Centrifugal Pump Specification And Selection - A System's Approach

Lecturepg. 93Proper pump specification and selection results in the best pump being purchased for the required service. Economic considerations may meant that “best” is not always the most efficient, best hydraulic fit or most expensive. As in most process or operational applications, the three primary areas of consideration are safety, reliability, and cost. Mechanical equipment requires periodic maintenance; therefore, maintainability must be included as a fourth area of concern. Prioritizing these four is a first step. Pump specification proceeds from this point. The entire process of specification and selection is a team effort involving various disciplines. Typical areas and personnel involved are process/operations, design, rotating equipment specialist, and purchasing, mechanical, and vendors. The complete process f centrifugal pump specification and selection is discussed as it involves these various disciplines. Primarily, some of the critical hydraulic areas of primary concern are addressed, along with the interrelationship between process requirements in these areas and the analytical approach to highlighting these areas in the selection process. The effect of pump design on suction specific speed, recommended minimum continuous flow and net positive suction head requirements are highlighted, together with process system variables which influence these parameters. The process is sequential and proper completion requires clear definition of the first step. Specifying the pump is not the first step after a brief review of boundary parameters. A full system analysis must precede pump specification. Pump vendors and most contactors are aware of this, but it is left to the user to address this need in the early stages. Only after completion of system analysis can we confidently proceed to pump specification, bid request, bid review and finally pump selection. The result of such a process is the selection of a pump which satisfies both process and mechanical needs