Centrifugal Pumps

A “stable” curve is important for pump operation, especially for pumps in parallel operation. The higher the energy level and the more critical an installation, the more the pump curve could become an issue.
The International Paper plant in Courtland, Ala., had experienced problems with a white water pump on a paper machine since the plant installed the pump in the late 1970s.
Commerce, Texas, relies on nearby Lake Tawakoni for supplying water, but falling lake levels were creating problems for its vertical turbine pumps.
Last month I reviewed an Excel-based Radial Thrust Calculator and showed how it can predict the magnitude of unbalanced radial thrust when a centrifugal pump is operated to the left of BEP.
Our attempts to normalize or classify water turbine hydraulic performance culminated in 1915 with the development of the specific speed concept, which was later applied to centrifugal pumps.
A number of technical papers (1, 4, 7, 8) have shown that the maximum damage rate to centrifugal pumps, at least in water services, typically occurs when the NPSHA is in the range of two to three times the NPSHR3.
In 1982, Richard Dubner of Chevron developed a graph for use in establishing minimum continuous flow rates for centrifugal pumps.
If it is necessary to increase a system's NPSHA, one or more of the following steps may be employed.NPSH, net positive suction head, pump system optimization
The diesel exhaust fluid market creates opportunities for pump manufacturers.
The McGraw-Hill scientific dictionary [5] states that a volute is "a spiral casing for a centrifugal pump... designed so that speed will be converted to pressure."
When the motor amps are kicking a unit offline, the first question is whether the motor or the pump is the problem.
Last year in “Trending Revelations in Vibration Analysis,” (Pumps & Systems, June 2009), I discussed the importance of statistic trending in vibrations analysis. Usually, as most would expect, vibrations gradually increase with time. This increase reflects the normal internal wear, accumulative misalignment and deformations that can occur within a pump. All these wear conditions will lead to eventual failure.
Vibration analysis trending can be a helpful tool in predicting brewing problems, before they develop into a big issue.
Vortex action: how lower efficiency can reduce overall cost. pump efficiency
Proper installation and adjustment can make the difference between the success and failure of a packed pump. By keeping in mind the fine points of a few key principles, the chances of success are greatly increased.
The Hydraulic Institute NPSHA Margin Work Group (1) recommended NPSH margins ranging from zero to four times the NPSHR (NPSHA÷NPSHR = 1 to 5).


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