Energy-efficient pump utilization

The result of a technical-economic survey of energy usage by centrifugal pumping equipment in the United States is presented. The possibility of significant energy savings in at least four key pumping categories is discussed. Methods of improving pump and system efficiencies in order to effect these savings are given. The present and future economics of enhanced pumping efficiencies are also considered. I. Introduction R ECENT dramatic rises in the cost of energy, along with concerns over future energy supplies in the United States, dictate that all types of machinery and systems be carefully examined for possible energy savings. One of the most common types of machinery in use is the pump. Only electric motors are more numerous,1 and over half of these above one horse-power are used to drive pumps.2 Thus, pumping equipment clearly represents a major consumption of energy and the apparent possibility of significant energy savings in the future. Centrifugal pumps are at the focus of the present study because of their commanding numbers relative to other pump types,3 and because they are utilized across a broad range of sizes, power inputs, and efficiencies. A centrifugal pump imparts energy to a liquid through the work done by a rapidly rotating vaned impeller. Some fraction of the impeller energy appears as increased pressure or head in the liquid discharged by the pump. Centrifugal pumps are thus distinct from rotary and reciprocating pumps, which involve a positivedisplacement action rather than an impeller, and from compressors, fans, and blowers, which impart energy to gases rather than to liquids. This paper concerns a study aimed at defining a national program in energy-effici ent pump utilization. The study includes a broad technical-economic survey of energy usage by pumps in the United States, followed by technical analysis and performance testing to identify the means by which significant national energy savings are possible. Portions of the study are still in progress and will be fully reported on at a later date.4