Locating the greatest centrifugal pump energy savings

Determination of the maximum required flow rate from the pump is the most important criteria in setting the energy usage for a centrifugal pumping application. When the maximum required flow rate is set, it is generally specified as the rated flow. The more obvious energy savings are those associated with improvements in the efficiency of the driver and the efficiency of the pump. While these are worth pursuing, they are small in comparison to efficiency gains to be realized by properly analyzing the pumping system to achieve the best fit of the pump to the system and operating requirements. Gains of 2–5 % may be realized if high efficiency motors are used in preference to standard motors. Improved design and manufacturing techniques may result in the availability of a high efficiency pump, with a further 3–7% efficiency gain potential. Such gains, in themselves, are often worth the added capital cost, and are being implemented by a larger number of pump users. Additional small efficiency gains may be realized through optimization of running clearances; typically, reducing wear ring clearances, using special materials that tolerate a degree of contact, and allowing the wear ring clearances to establish their natural minimum.