Stormer viscosimeter

Viscosity and Plasticity—Viscosity and plasticity are closely related. Viscosity may be defined as the force required to move a unit-area of plane surface with unit-speed relative to another parallel plane surface, from which it is separated by a layer of the liquid of unit-thickness. Other definitions have been applied to viscosity, an equivalent one being the ratio of shearing stress to rate of shear. When a mud or slurry is moved in a pipe in more or less plastic condition the viscosity is not the same for all rates of shear, as in the case of ordinary fluids. A material may be called plastic if the apparent viscosity varies with the rate of shear. The physical behavior of muds and slurries is markedly affected by viscosity. However, consistency of muds and slurries is not necessarily the same as viscosity but is dependent upon a number of factors, many of which are not yet clearly understood. The viscosity of a plastic material cannot be measured in the manner used for liquids. The usual instrument consists of a cup in which the plastic material is placed and rotated at constant speed, causing the deflection of a torsional pendulum whose bob is immersed in the liquid. The Stormer viscosimeter, for example, consists of a fixed outer cylinder and an inner cylinder which is revolved by means of a weight or weights. 

The viscosities of four different grouts, as measured by a Stormer viscosimeter, are shown in Fig. 10.5. Viscosities, of course, vary with percent (dissolved) solids, and the chart is presented in that fashion. The usable viscosities of the various materials depend on the minimum desirable field concentration of solids. Thus, while it is obviously possible to work with a 20% sodium silicate solution in the Joosten process (a viscosity of between 3 and 4 cP), a gel would not form at that low a concentration, and it would be misleading to claim a 4 cP viscosity. In a similar fashion, other silicate formulations can be used to give either low viscosity of high strength, and it is misleading to list those values simultaneously as if they were the properties of the same fluid. 

At this point, the role of viscosity must be considered. Figure 39 shows the effect of viscosity on mass transfer coefficient. It is necessary to measure viscosity with a viscosimeter which mixes while it measures viscosity. Figure 40 illustrates the Stormer viscosimeter which is one device that can be used to establish viscosity under mixing conditions with shear rates that can be established. 

Viscosity Stormer viscosimeter (ASTM D562-81) and Brookfield viscosimeter (ASTM 2196-86)... 

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