MechChem Africa November 2017

⎪ Products and industry news ⎪

Choose your rubber lining with care

the most suitable wear material in such applications where wet abrasion is found, for example in thepumpingand separation of fine particle slurries Equipment used in these processes is frequently lined with pre-cured rubber sheet. Where mines, fabricators and ap- plicators have access to an autoclave or open steam facility, steam cured rubber sheet could be used. Linatex ® premium rubber has superior physical properties, and this Budhu says is due to the unique manufacturing process used by Weir Minerals. The manufactur- ing process to make Linatex incorporates ‘liquid phase processing’ and ensures that the original molecular structure of natural rubber is retained. Budhu says this is criti- cal to the performance characteristics of the product because, Linatex premium rubber has an evendispersion throughout the rubber sheet. “The combination of a high wet ARI (Abrasion Resistance Index), high re- silience and tensile strength with a bi- modalmolecularweight distribution, gives Linatex rubber its superior performance in fine slurry applications,” he says. www.minerals.weir filter to remove most of coarser particles from the air entering a compressor room, the compressor’s own filters will need to be replaced far less often. “A spin filter consists of a cyclone- shaped tube, through which air is pro- pelled or drawn. On entering the tube, the air is induced to spinusing vanes. Particles in the tubemove to the outside of the vor- tex, and the clean air in the vortex centre exits through a central orifice at the end of the tube. A secondary stream of air is used to evacuate the dust-laden air back to where it came from,” he explains. Spin filters are also useful in the direct ventilation of the variable speed drives (VSDs) that are used on many compres- sors. RTS Africa Engineering has devel- oped a technique it calls ‘back-channel cooling’ of VSDs. www.rtsafrica.co.za

The choice of rubber lining in any mining or quarrying application remains complex and experience-based; one certainty, however, is that hardness and price per ki- logramare insufficient factors to consider when making that choice. According to Yatheen Budhu, prod- uct manager rubber products at Weir Minerals Africa, the mining industry has fallen into the habit of specifying rubber by hardness alone. Budhu says: “Other

important factors, including resilience, tensile strength, tear strength, cutting resistance and dry/wet abrasion resis- tance index (ARI), need to be considered to ensure that the option selected is fit for the application. “The quality of rubber sheeting varies widely within the industry. Moreover, rubbers which are formulated for dry abrasive applications may not be suitable for wet abrasion applications,” he says. “An essential primary step is to assess the application requirement when selecting the type of rubber sheeting.” Rubber sheeting has had to compete increasingly with synthetic elastomers, polymers, ceramics and other abrasion resistant metals, he says. Nonetheless, rubber has retained its position as the preferred wear material for fine slurry abrasion resistance, as well as impact and chemical resistance in themining industry. Most processes used in themining sec- tor to recover base and precious metals, coal, diamonds andotherminerals involve the suspensions of solids in water. Budhu explains that natural rubber is considered grinding paste, whichwill acceleratewear dramatically,” he adds. All compressors have their own air intake filters, which are, in the main, de- signed tofilter out tiny low-mass particles. However, if a compressor is exposed to excessive dust from manufacturing or miningwhere the particles are larger than three microns (μm), the compressor’s air filters block up rapidly. In this circumstance, one of two things will happen: either, the compressor owner has to spend a lot of money more fre- quently changing proprietary air filters; or the filters suffer from total neglect. “With a blocked air filter, the compres- sorisincreasinglystarvedofairanditseffi- ciency levels drop. Ultimately, this leads to compressor failure. With large industrial compressors costing anything upwards of

Weir Minerals produces custom rubber linings including Linatex at its plant in Alrode.

RTS Africa spin filters do away with dust damage

“Many industrial air compressors work in very dusty conditions, particularly in the mining industry, where dust from newly broken rock is particularly abrasive,” ex- plains managing director of RTS Africa Engineering, Ian Fraser. “If you get dust into the cylinders of a compressor, it com- bineswith theoil to formahighlycorrosive

Cummins Africa relocates to Allandale Building Cummins Africa and the Middle East (AME) has announced that it has relocated to new prem- ises in the Allandale Building in Waterfall City, Midrand, close to theMall of Africa development. The relocation became necessary because of the company’s success on the continent; a healthy andgrowingorganisationnowrequires expanded facilities. “We would like to welcome Cummins to Waterfall City,” said Morné Wilken, CEO of developer, Attacq. “We are confident that Cummins, a global energy and power leader, will benefit from its new office’s strategic location and facilities, whichmakeWaterfall City the ideal site for the company’s Middle East and Africa headquarters.” africa.cummins.com

half a million rand, an unsched- uled and urgent capital require- ment for a replacement and the cost of lost production time can have serious consequences for a company,” Fraser says. RTS Africa spin filters will re- move98%of 15μmparticles and above, 93% of 10 μm particles, and 80% of 5.0 μm particles. By using an RTS Africa inertial spin

Spin filters for use in back-channel cooling of VSDs.

40 ¦ MechChem Africa • November 2017