Engineering & Mining Journal

FEB 2018

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HYDROCYCLONES 30 E&MJ; • FEBRUARY 2018 www.e-mj.com per-gold producer. "Initially, the mine used FLSmidth Krebs D26B cyclones with rub- ber liners and a ceramic apex, which gave a life of about 4,000 hours," he said. "Replacing the liners with super-thick resilient rubber increased this to 7,000 hours, which we were then able to double when those cyclones were replaced with gMAX26s. The liners on these are BPC (natural gum rubber) in the upper sec- tions, nitride-bonded silicon carbide in the upper middle cone, reaction-bonded silicon carbide in the lower middle cone and high-grade, sintered alpha silicon carbide in the lower cone and apexes to provide the greatest abrasion resistance." FLSmidth's most recent technology advance for hydrocyclones has been its wireless SmartCyclone monitoring sys- tem. "The key advantage is detecting rop- ing," Buttler explained. "When a cyclone is roping, it is misplacing coarse material to the overflow, which is usually the feed to the flotation circuit. "In serious cases, if the plant opera- tors are not watching carefully, this can lead to sanding-up of the flotation cells, which will then need to be shut down and dug out, all of which costs money." SmartCyclone is a monitoring and con- trol solution for reducing cyclone-related process upsets, improving cyclone overflow particle-size distribution, predicting and controlling cyclone maintenance sched- ules, and optimizing closed-circuit grinding processes. Buttler told E&MJ; the new wire- less sensors, fitted close to the underflow discharge, "listen" to the noise produced by the flow. "When roping begins, the noise drops off, and ceases altogether if the cy- clone apex is blocked. The sensor sends a wireless signal to the control screen, which immediately flags up to the plant operators that there is a problem." He went on to describe how the con- centrator at Vallex Mining's Teghout cop- per-moly operation in Armenia had typi- cally been experiencing 12 hours a month downtime because of cyclone issues. Since the installation of wireless SmartCy- clone monitors, downtime has been zero — "and at $20,000 an hour for down- time, that's significant," he commented. E&MJ; also asked Buttler what FLSmidth has done to help its custom- ers reduce the costs and time involved in maintaining their cyclones. "The basic construction of a cyclone has not changed much, but we have been working with our customers to simplify maintenance," he said. "As an example, we have designed a cradle that can facilitate transporting two or three large cyclones from being stripped out to one of our authorized re- build shops — it just makes the mainte- nance crews' job easier." And the company recently reported on a success story from Kirkland Lake Gold's Fosterville mine near Bendigo in Austra- lia. Experience with the previously used rubber-lined cyclones there had shown that apex replacement was required every four weeks, with total cyclone relining at a cost of some US$9,000 after four apex cycles. Installing new ceramic liners has pushed out the rebuild interval to a year, with replacement units being delivered on a "slot-in" basis and relining done off-site, rather than using the mine's personnel to do the job. In addition, the cyclone over- flow P 80 sizing is now less variable, and there is much less sand being misdirected to the flotation cells, FLSmidth noted. Advanced Liners Help Cut Cyclone Wear Morgan Advanced Materials produces wear-resistant inserts for hydrocyclones. The company told E&MJ; that its Tech- nical Ceramics business manufactures a wide range of high-performance hydrocy- clone liners from its Deranox 975 alumina material, chosen for its wear-resistance in abrasive applications. Morgan's commercial manager, Oliver Ridd, explained that while its principal market for these liners is in the oil and gas industry, where hydrocyclones are used for de-sanding fluids, the mineral sector is also important for the company. "Slurry separation in mineral processing is a significant application for hydrocylon- es, and we see this as a growth market for us, worldwide," he said. Containing 97.5% alumina, Deranox 975 is not only abrasion-resistant, but also has good mechanical strength and corrosion resistance, Ridd added. "We can provide a wide range of liner sizes with our most common being between 1 in. and 4 in. internal diameter. Sizes The difference between normal underflow (right) and roping, which FLSmidth's SmartCyclone sensors, fitted close to the apex, can distinguish and send a warning to the plant operators. Alumina liner inserts made by Morgan Advanced Materials are widely used in hydrocyclones used for oil-industry desanding.

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