Centrifugal pumps series operation

The piping and valves may be arranged to enable two centrifugal pumps to be operated either in series or in parallel. For two identical pumps, series operation gives a total head of 2Ah at a capacity Q and parallel operation gives a capacity of 2Q at a total head Ah. The efficiency of either the series or parallel combination is practically the same as for a single pump. 

Figure 3-35. Operation curves of two duplicate centrifugal pumps in series and parailel.

Diskind (1959) determined the operating characteristics for centrifugal pumps in parallel and in series using a simple graphical method. 

Two centrifugal pumps are connected in series in a given pumping system. Plot total head Ah against capacity Q pump and system curves and determine the operating points for... 

Figure 7.17. Operating points of centrifugal pumps under a variety of conditions, (a) Operating points with a particular pump characteristic and system curves corresponding to various amounts of flow throttling with a control valve, (b) Operating point with two identical pumps in parallel each pump delivers one-half the flow and each has the same head, (c) Operating point with two identical pumps in series each pump delivers one-half the head and each has the same flow.

In the true gravity case, pumps are not used. If, however, the liquid is highly viscous, to achieve efficient operation, pumps are required to force the fluid through the pressure filters. The pump can be considered essentially as a press with a plate-and-frame filter. The plate-and-frame filter consists of a series ot frames over which the filter medium is stretched. A centrifugal basket of fine mesh is another method of particulate removal. 

The method of transporting ore from the mine to the beneficiation plant depends on ore characteristics, mining methods, and local infrastructure. Railroad transport has been practiced in Russia and Iraq. Haul trucks and belt conveyors are commonly used in China, Jordan, Mexico, Morocco, Russia, Syria, Tunisia, and the western United States. Slurry pipelines of 18-22 in. diameter, operating at less than 100 psig, are used exclusively in central Florida, north Florida, and eastern North Carolina. The pipelines may be extended up to 10 miles or more, by installing a series of centrifugal slurry pumps at 4000 ft intervals. 

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