Wear of stirrer heads

The theoretical prediction of the relationship p oc h (u being the tip speed of the stirrer, comparable with the collision rate of the particles) was fully confirmed. It was independent of stirrer type. The same applied for the dependence v = /(t). It was found that the wear is greatest at the beginning with the not yet reduced stirrer diameter at which the tip speed was highest. Later on it leveled off until a constant value was reached, which is virtually independent of the starting conditions. 

The relationship p = /(t) was suitable for estimating the operating lifetime of stirrers. It is only necessary to supply the maximum permissible diameter reduction d/da- In practice d/da values in the range of 0.9 to 0.99 are acceptable. 

The wear rate increased directly proportionally up to = wt.-5%, above which it decreased. The cause is the ever greater collision frequency between the particles themselves. The influence of the particle diameter dp on the wear rate is considerable p oc dp. This relationship can also be proven theoretically [274]. 

As regards the influence of the type of solid on the wear, there are only approximate data. The wear is roughly 50 times smaller with lime particles than with corundum, with the corresponding values for glass and quartz being 3 and 1.1 

Shear Stress on the Particulate Material Being Mixed 

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