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Rubber-lined 0,15m pump 3-vane impeller diam. = □MSm rpm = 760 1140 periite mineral

Solids density ratio, S3 = 2.39 d50= 350 |iid

Rubber-lined 0,15m pump 4-vane impeller dijim. - 0.45m rpm = 600 Copper tailings

d50= 1M|im

FIGURE 13 Head and efficiency reduction curves for two products (from Sellgren and Vappling, 1986). [Note: for dimensions in inches, divide mm by 25.4 and multiply m by 39.36.]

With equivalent reductions, RH = Rv, the power consumption increases directly with the relative slurry density.

with Rh < Rh (Hr > hr), Eq. 1 becomes that is, the power consumption becomes larger than that given by Eq. 1.

Finally, the calculated reductions may be underestimated if the solid particles are coarse and very angular. For example, the solids used in the preceding examples consisted of crushed angular particles and actually gave reductions in head and efficiency well over 10% (Sellgren et al., 1997), compared to RH = 8% calculated here based on Figure 12.

On the other hand, with very fine particles, or large Xh-values and high solids concentrations, most slurries are practically nonsettling. In this case, the solids effect is mainly related to the rheological behavior. When pumping nonsettling slurries in industrial applications, the slurry normally behaves in a non-Newtonian way, giving widely varied pump performance effects. In general, however, small pumps are affected more than large units when pumping highly viscous or non-Newtonian media. Furthermore, the influence on the efficiency is normally larger than on the head.

Occasionally, highly non-Newtonian slurries may be pumped by centrifugal pumps operating at flow rates much lower than the maximum-efficiency value QBEP. This may cause a dramatic drop in head, which creates an unstable head curve, seen for example in Figure 14.

Pm 7 Sm

FIGURE 14 Effect of highly non-Newtonian slurries on pump head and efficiency (from Sellgren et al., 1997). [Note: for flow rate in gpm, multiply m3/s by 15,850; for head in ft, multiply m by 3.28.]
Survival Treasure

Survival Treasure

This is a collection of 3 guides all about survival. Within this collection you find the following titles: Outdoor Survival Skills, Survival Basics and The Wilderness Survival Guide.

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