WHY STABILIZE?

In some instances, you may need to maintain agitation while liquid level in the tank is pumped down. As a general rule, operating mixers through draw-down is not desirable. A mixer is physically capable of running as the tank is pumped down, or with the tank completely empty. However, a mixer which operates continually through draw-down will experience severely increased loading on the geardrive, and added stress to the mixer shaft.

For improved service life, the minimum liquid coverage above the impeller is generally one (1) impeller diameter or more. Optimum process results are often obtained with a coverage of two (2) or more impeller diameters.

The lower impeller of a gear-driven mixer with a shaft length longer than four (4) feet generally needs to have downward extending stabilizers. Stabilizers come in the form of rings or fins. The object of stabilizers is to have some impeller mass extending down into the process liquid when the liquid level is even with the level of the impeller in the tank. The impeller pumps down. The force of liquid against the impeller is upward and to the side. Without stabilizers, the impeller will kick out the solution. This is known as "walking", and it puts severe stress on the shaft.

Note: In dual-impeller systems, the lower impeller (which has its own stabilizers) acts as a stabilizer for the upper impeller running through draw-down.