The Suction Performance Of Centrifugal Pumps Possibilities And Limits Of Improvements
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Following a brief description of the general suction performance of pumps and starting from an impeller designed for standard requirements, it will be discussed by which modifications and up to which limit the suction performance can be improved. In this context, it will be shown that the well-known measures – e.g., enlargement of the impeller inlet diameter, reduction of the vane number or installation of an inducer – may result in some restrictions concerning the possible operational range and may pose a risk of cavitation erosion. These undesirable consequences can, however, be avoided or at least moderated by modifications upstream of the impeller. The suction performance can also be improved by using double suction instead of single suction pumps. It is explained why the resulting improvement may not be as substantial as could be assumed at a first glace. Pumps with inlet velocities exceeding 25 to 30 m/s that are expected to run for 10,000 hr and more without cavitation damage cannot operate at NPSH values corresponding to a 3.0 percent head drop, even if a highly cavitation-resistant material is used. It is demonstrated that the design parameters of their impellers differ from those used for ‘normal’ impellers. If NPSHA is not sufficient, a booster pump has to be provided, or the rotational speed has to be reduced. As the latter is an expensive alternative, the question arises what the minimum booster pump head is. Some information regarding this issue is given. It will also be demonstrated that there is an upper limit of the rotational speed of the main pump beyond which can economical solution is impossible.
Hergt, Peter; Nicklas, Alexander; Mollenkopf, Gerhard; Brodersen, Sonke (1996). The Suction Performance Of Centrifugal Pumps Possibilities And Limits Of Improvements. Texas A&M University. Turbomachinery Laboratories. Available electronically from