Reducing Operational & Maintenance costs with Multotec ceramic impellers

In the highly abrasive arena of slurry transportation applications, the replacement of impellers adds significantly to both operational and maintenance costs. By using high alumina ceramic impellers it is possible to achieve significant cost reductions, while simultaneously achieving consistently good performance over an extended period of time.

“Because high alumina ceramic is second only to diamond on the MOH hardness scale, as well as being chemically inert, it is suitable for use in hazardous and hostile environments. It is perfect for use in slurry transportation applications in the coal, andalusite, platinum, gold and iron ore industries,” Stephen Jackson, marketing manager of Multotec Wear Linings, says.

The success of the Multotec Ceramic Impeller is based on the non-monolithic design of its structure. It comprises a steel frame that takes up the mechanical forces and a ceramic outer lining with a minimum thickness of 8 mm, which affords optimum wear resistance. The impeller’s steel base frame has a threaded boss for mounting it onto the drive and a polyurethane seal to ensure closure around the mounting point and to prevent corrosion of the metal.

“We have mounted the ceramic components on to the steel structure using Multotec’s resilient proprietary polymeric Hi-bond epoxy to provide an optimum combination of the best properties of the spectrum of available materials. This overcomes the inherent brittleness of ceramics, making the composite extremely effective in arduous pumping applications,” Jackson explains.

The distinctive combination of these materials results in better impact absorption, allowing the impeller to absorb a certain amount of impact from small stones, tramp metal and nuts and bolts passing through the pump.

High alumina ceramic impellers exhibit a number of advantages over their steel counterparts. Since the mass of the ceramic impeller is about half that of a steel impeller, this provides greatly reduced general stress on the pump itself and a lower power draw.

Tests show that there is also an increase in the liner and casing life because the impeller retains its dimensions for a longer period. In steel liners, the fit between the impeller and the housing remains tight, preventing changes in the flow patterns within the pump housing. This can result in cavitation and vortexes forming within the pump with a resultant high wear.

Due to the formation of holes on steel impellers leads and the resultant dragging and grinding of the slurry between the impeller and the housing, excessive wear is common. “Tests on our ceramic impellers showed that very little cavitation occurs on the outside. Alumina ceramic wears away by a chipping action which takes place only when the kinetic energy of the impacting particles exceeds the intermolecular bond strength of the alumina particles. The higher the percentage of alumina used, the higher the bond strength and the greater the resistance to chipping,” Jackson points out.

A range of over 25 standard impeller types is available and the Multotec team can customise impellers to meet specific application requirements. The impellers are capable of operating at up to 2 900 rpm producing a head of up to 150 metres on a 3” outlet pipe.

“We have noted an increased lifespan of our ceramic impellers of up to four and six times more than conventional rubber or steel impellers. Not only does this equate to substantially reduced downtime, but the performance of the ceramic impeller resulted in increased pump volute life,” Jackson concludes.