Industrial Mixer Shaft Design – Part 4 of 4
Our previous blog post discussed the when to use a steady bearing in your industrial mixer shaft design. So if a steady bearing provides so much value, why doesn’t every industrial mixer use one? There are several reasons:
- Increased Maintenance
- Process Incompatibility
- Flushing Requirements (Abrasive Slurry Applications)
The first reason a steady bearing often isn’t used is increased maintenance. Steady bearings wear out relatively quickly compared to most other industrial mixer components. Most steady bearings should have the bushing and wear sleeve replaced about once a year. An initial steady bearing installation should be inspected after the first six months of operation to ensure more frequent changes are not necessary.
From a mechanic’s point of view, it is generally easy to replace a steady bearings’ wearing components. ProQuip always uses a wear sleeve on the end of the industrial mixer shaft. The wear sleeve slips over the bottom end of the industrial mixer shaft and can be easily replaced. Likewise, the bushing is inserted in the housing and held with retaining plates that allow changing it without disturbing the rest of the industrial mixer installation. The metal sleeve wears more than the elastomer bushing in about 90% of cases, but they should be replaced together.
A problem with changing these wearing components is that someone has to physically enter the mixing vessel. In many cases, mixing vessel entry is potentially dangerous and must follow a specific procedures. If you are not familiar with your company’s mixing vessel entry procedure, contact your safety manager. An especially hazardous mixing vessel entry can take a week of preparation and may require a complete process shutdown.
The second reason a steady bearing is not used in many industrial mixer applications is process incompatibility. Only a few bushing materials are approved for steady bearing use and all have limits:
- Elastomers – application limits
- Bronze – incompatibility with many materials and processes
- Cast iron – very limited applications
- Polytetrafluoroethylene (PTFE) – temperature restrictions
The steady bearing is normally lubricated and cooled by the vessel contents. You should never operate a steady bearing unit for a prolonged period of time without liquid coverage. Moreover, there are many materials that will polymerize, crystallize or otherwise react in high shear annulus between the bushing and the sleeve. This condition can make the use of a steady bearing impractical for your industrial mixer application.
Finally, a steady bearing may also be a poor choice for use in an abrasive slurry. Although a steady bearing can be equipped with a flushing system for the annulus, this is an additional expense and must be carefully maintained. Flushing systems can also be used for sanitary applications, including the capability for steam flushing. However, flushing will not prevent wear and the steady bearing will still have to be serviced on a regular basis.
For More Information
Whether to install a steady bearing or not will depend on your process and safety procedures. To help determine if you should install a steady bearing, read our blog post “When to Use a Steady Bearing in Your Industrial Mixer Shaft Design,” complete the ProQuip Applications Data Sheet or contact us at 330-468-1850 or firstname.lastname@example.org. We can provide industrial mixer pricing with and without a steady bearing and explain proper maintenance procedures of a steady bearing unit to ensure reliable performance.
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