This section discusses the application of centrifugal pumps to the transport of slurries as
introduced in Subsection 9.16.1.
Where the distance is large and the size of the solids less than about 100 microns,
positive displacement pumps are usually applied. If the solids to be transported are
smaller than about 60 mm in size, water is readily available or already part of the
process, and the distance is less than 12 miles (20 km), a pipeline driven by centrifugal
slurry pumps is usually more cost-effective than belt conveyors, trucks, or railway
Types of solids transported vary from sag mill feed in a copper mine, iron ore, phos-
phate matrix, coal, rock salt, tar sands, red mud, various types of waste tailings, and
crushed rock and silt. An 18 in (0.45 m) diameter pipeline, for example, is capable of trans-
porting as many as 2200 tons/hr (2000 tonnes/hr) of sand. This equates to about one hun-
dred truckloads per hour over the distance involved.
The application that involves the largest quantities is in the dredging industry, con-
tinually maintaining navigation in harbors and rivers, altering coastlines, and mining
material for landfill and construction purposes. Because a single dredge may be required
to maintain a throughput of 7000 tons/hr of slurry or more, very large centrifugal pumps
are used. Figures 1 and 2 show, respectively, an exterior view of a dredge pump on test, and
a view of a large slurry pump impeller (Addie and Helmly, 1989).
Because the aim is to transport solids and not water, the higher the concentration of
solids, the better for energy consumption and capital cost. This does, however, mean that
wear due to the abrasive solids will be significant, requiring a special type of centrifugal
pump design and the use of special materials. Slurry pumps may be selected for low-
concentration dirty-water service. Most of what follows, however, is about pumps designed