Specialist manufacturer of high-density and alumina ceramics Multotec Wear Linings, part of the Multotec group of companies, offers a range of ceramic impellers for slurry pumps in the coal, andalu- site, platinum and other related industries.
Designed, patented and manu-
factured by Multotec Wear Linings, these ceramic impellers significantly reduce operating and maintenance costs, while delivering better yield consis-
tency over a longer period.
The high-density alumina ceramic used for the impellers is second only to diamonds on the Mohs scale of hardness and it is considered the most versatile and effective wear resistant material available for high-wear areas in process plants, reports the company. Comparative testing has shown that, in most applications, no other material can compete on a cost-to-life basis with the charac- teristics of alumina ceramic.
The enhanced wear characteristics of alumina ceramics prevent wear in critical areas, which enables the impeller to function for far longer at constant revolutions per minute. This is of importance in areas such as gold mine milling circuits, where cyclone performance is directly dependent on a constant delivery and pressure from the pump.
Ceramic impellers offer significantly lower maintenance costs when compared with conventional rubber and Ni-hard impellers, reduced downtime, longer and more consistently high yields and better pump liner life owing to less recirculation, and have a small but significant saving owing to 45% lower weight and remaining in balance for longer periods.
The Multotec ceramic impeller comprises a steel frame that absorbs mechanical forces and a ceramic outer lining, which affords enhanced wear resis- tance.
Alumina ceramic impellers are particularly resistant to the ripping and tearing damage caused by sharp objects often found in slurries. Ceramic impellers are chemically inert and suitable for use in hazardous and hostile environ- ments. The impeller design and assembly, however, has to be adapted to suit specific applications, such as the pumping of acidic materials.
The ceramic components are mounted onto the steel structure by means of Multotec’s proprietary adhesive.
This resilient bonding mechanism is an integral part of the design and absorbs the impact
resulting from foreign objects passing through the pump.
This makes the composite assembly effective in arduous pumping applications and
results in better impact resistance, allowing the impeller to absorb impact from small stones, tramp metal, and nuts and bolts passing through the pump.
The impeller has a steel base frame with a threaded boss for mounting it onto the standard drive shaft. A polyurethane seal provides protection around the mounting boss and prevents corrosion of the metal frame.
The extreme hardness and high density of ceramic impellers lead to a superior erosion and corrosion resistance at both high- and low-impingement angles. This makes ceramic impellers ideal for use in slurry pumping installations and ensures longer life because the pump can be operated at a constant speed throughout its life without significant reduction in performance.
Production volumes are maintained because of the consistent performance achieved during the entire working life of the ceramic impeller. The increased life of ceramic impellers, in some cases between four and six times longer than that of conventional rubber or steel impellers, results in substantially reduced downtime.
The performance of the cera- mic impeller results in increased pump volute life, which translates into greatly reduced maintenance costs. The mass of the ceramic impeller is about half that of a steel impeller, which means that bearing maintenance is substantially reduced.
All the impellers are individually balanced, ensuring smooth trouble-free operation, which, as tests have shown, also leads to increased liner and volute life. This can be attributed to the fact that the impeller retains its dimensions longer and, with the fit between the impeller and the housing remaining tight, this prevents changes in the flow patterns within the pump housing which can lead to less erosion of pump components.