Side-Entering Mixers

When abrasive solid particles must be suspended, maintenance costs for the submerged shaft seal of a side-entering propeller may become high enough to make this type of mixer an uneconomical choice. 

Side entering mixers are used for blending pui-poses. The side entering propeller type mixer is economical and establishes an effective flow pattern in almost any size tank. Because the shaft seal is below the liquid level, its use in fluids without corrosive and erosive properties is usually ideal. 

For turbine mixers that the width of a baffle should not exceed more than one-twelfth of the tank diameter and, for propeller mixers, no more than one-eighteenth the tank diameter. With side-entering, inclined or off-center propellers, as shown in Figure 13, baffles are not required. Instead, shrouded impellers and diffuser rings may be used to suppress vortex formation. These devices contribute to flow resistance and reduce circulation by creating intense shear and abnormal turbulence... 

Side Entering describes a mixer design whieh has a horizontal shaft entering through the side of a mixing vessel. 

Figure 5-23G. Side-entering propeller mixer position, large tanks. By permission, Rushton, J. H., Petroleum Refiner, V. 33, 1954, p. 101 [17].

The top entering mixer units are better for producing flow at constant power than the side entering units [29]. The radial flow impellers require more horsepower when compared to the marine impellers. 

Side entering mixers (usually propellers) as shown in Figure 5-23G are placed 18-24 inches above a flat tank floor with the shaft horizontal, and at a 10° horizontal angle with a vertical plane through the tank centerline. This equipment is used for fluids up to 500 centipoise [21]. For fluids from 500-5000 c.p., the mixer is usually top entering. 

For side entering horizontal mixers not limited to blending operations, there are some differences in recommendations concerning the physical location of the impeller ... 

Oldshue, J. Y, H. E. Hirschland and A. T. Gretton, Blending of Low Viscosity Liquids Widi Side Entering Mixers, Chem. Eng. Prog. 52, 1956, 481. 

Figure 38.2 Side-entering propeller-type mixer...

Side-entering propeller (SEP) mixers, 26 706, 708, 709 Side reactions, 20 357-359... 

Table V gives a typical values for estimation purposes of blending horsepower required for various low-and medium viscosity situations. Mixers may be either top entering or side entering. Again, a side-entering mixer requires more power and less capital dollars, and this must be evaluated in looking at practical equipment. Side-entering mixers have a stuffing box or mechanical seal and are limited for use on materials that are naturally lubricating, noncorrosive, or nonabrasive.

FIGURE 29 Typical orientation of side-entering mixer in large petroleum storage tanks. 

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