Wear of impellers is often encountered in mixing applications. It is possible, however, to maximize their lifetime by implementing appropriate measures with respect to their shape, coating or solid ceramic design or a combination of the above. The resulting cost savings easily provide a high return-on-investment (ROI) after only a short period of time.
Protective coating is usually applied in thin layers. Once they are worn off, the base material will again be subject to high wear rates. Instead of coatings, impeller blades or complete impellers can be made from solid ceramics. In contrast to coatings, a solid ceramic structure offers the advantage of the same hardness throughout the entire component. A direct comparison with steel or alloys reveals that the lifetime of an impeller in abrasive environments can be increased by a factor of 10 – 20 by solid ceramic components. The use of advanced ceramics is not only recommended in the raw materials or building materials industry, where worn out components can cause tremendous downtime costs. High purity materials like silica compounds for the electronic or medical industry do not allow contamination by metal attrition. Ceramic is here also the material of choice.
Due to recent advances in processing ceramics it is possible to manufacture complex geometries of blades for impellers up to two meter in diameter. These industrial ceramics have excellent material characteristics which make them virtually predestined for use in heavy duty applications in the process industry: a constant strength even at very high temperatures, corrosion resistance and surface hardness. Nevertheless, it is an essential requirement for the design of such impellers to know the hydraulic and vibrational loads on the impeller blades exactly. These loads, coming from intense mixing, are determined e.g. by numerical flow simulations (CFD). Beyond that, as the ceramic components are shock sensitive it needs a specific know how to achieve a reliable design.
