The bottom bearing is a slide bearing with a shaft sleeve running on a bushing installed into a housing that is mounted to the tank bottom. A wearing sleeve is at the end of the agitator shaft. As the shaft end runs inside the steady bearing, shaft deflections are practically eliminated. This continuous support has a significant impact on the agitator’s critical speed and radial loads to the agitator drive unit. UTG applies a wide range of bushing materials to cover different wear and corrosion conditions, such as PET, PTFE, Rubber, Ceramic/PU composite and alloyed steels (e.g. DEVA metal).
The deflection limiter or catch ring is a support frame installed to the tank bottom. Unlike bottom bearings, there is no continuous contact between the shaft and bottom support. The deflection limiter prevents only extreme deflection of the shaft. An advantage compared to bottom bearings is that there are no wear parts. The disadvantage is that the catch ring has no impact on the critical speed of agitator or normal radial load of the drive unit. The deflection limiter mainly acts in case of running the agitator while filling or emptying the tank. The higher bending moments are in this case reduced, and the agitator can be reduced in size.
For cases where bottom bearings and catch rings are out of the question, the safety of shaft mechanics can be improved with a dynamic stabilator. UTG’s proprietary RA turbine does not have a positive effect on the critical speed and radial loads of the drive unit. It is applied especially in slurry tanks where the settling of large/heavy particles is seen as a risk for the bottom bearing and for the process.