Mixer having exposed clean-in-place bearing assemblies

Abstract

An improved immersible magnetically-coupled mixer has a plurality of rollable bearing assemblies readily cleanable by flushing in place and easily removable and replaceable without damage to either the mixer impeller or the bearings. The rollable bearings are resistant to corrosion, capable of running without lubrication, and have low propensity for batch contamination through wear. The rolling and fixed elements of the bearings are impervious to attack by the process materials being mixed, the rollable elements, preferably balls, can be formed of a hybrid ceramic such as silicon nitride, and the races can be formed of a nickel-beryllium or cobalt-chromium-tungsten alloy. A mixer impeller having a central bore is rotatably mounted at the upper end of the bore on the rollable bearings on an adapter collar receivable over an end of a fixed impeller shaft attached to the inner wall of a vessel at the bottom of the mixing space, which shaft may be on existing mixer shaft, thus requiring no modification of the shaft to retrofit the impeller assembly. The impeller contains magnets and is couplable in driving relationship to an external magnetic mixer drive. The bearings are exposed to the liquid in the vessel during agitation, and the impeller provides a continual flow of liquid across the bearing balls and races and the adapter collar, preventing formation of stagnant areas of process materials within the mixer assembly and permitting cleaning of all mixer surfaces by flushing.