Engineering & Mining Journal

JUL 2019

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Page 33 of 67

PUMPS, PIPING AND VALVES 32 E&MJ • JULY 2019 Corflex believes pinch valves are often the most suitable valve for slurry han- dling, because in the open position they resemble a rubber-lined pipe. Other types of valves, according to the company, have problems with abrasive material or pres- sure: Quarter-turn designs such as plug and ball valves generally have a reduced port that increases the velocity and each time they are turned they are scratched and end up leaking. Knife gates often have blades that are thinner than blank flanges for the same pressure and at high pressure can leak or form dished ends. Recently, the company filled an order for 450-mm pinch valves to operate at a pressure of 25 bar for a tailings project at a mine in South Africa. Corflex said that pinch valves used for high-pressure appli- cations have to be built with both safety and performance in mind –— the force required to close and seal a 450-mm pinch valve at 25 bar, for example, is 77 tons. To build a 450-mm product suitable for 25 bar appli- cations, a special valve had to be designed and built that, in every respect, was similar to Corflex's 500-mm high-pressure pinch valve. The 450-mm pinch valve sleeve developed to handle such high pressures required the design of special tooling and needed the addition of larger-gauge wire re- inforcement in the flange area. The tooling development work enabled the company to build a 450-mm pinch valve for a working pressure up to 35 bar, a test pressure of 70 bar and a calculated burst of 105 bar. The 450-mm valves are fitted with 4 x 160-mm hydraulic cylinders, which, at a hydraulic pressure of 200 bar, would seal the valves against a pressure of 34 bar, providing a sealing safety factor in excess of 30%. The hydraulic power pack to operate the valves has a constant recharge sys- tem to ensure the valves stay closed and do not creep open. Although not required for this project, the hydraulic power pack could have been built to automatical- ly close the pinch valves in the event of an electrical power failure, which means the valves could be used as open/close or nonreturn valves. According to Corflex, typical nonreturn valves in slurry pipe- lines are not always reliable so this sys- tem offers significant advantages. Automated Adjustments Save Time Efficient pump operation in aggressive wear applications depends on thorough and precise week- ly maintenance. A common mainte- nance procedure for large centrifugal cy- clone feed pumps, for example, in- volves adjusting the internal clearance between the pump impeller nose gap and the suction lin- er — a task that's usually done man- ually. As mineral producers strive to cut operational and maintenance costs, sometimes the next best thing to reduc- ing or eliminating periodic mandato- ry maintenance on pumps is to simply remove the need to have a worker, or a crew, present during a maintenance procedure. That was the objective when Minera Escondida reached out to GIW to request an automated solution for nose-gap ad- justments on its MDX pumps. Manual adjustments were taking three or four hours per pump, and because these ad- justments had to be made frequently, it resulted in higher maintenance costs. Minera Escondida wanted a solution with controls that could be managed remotely. After several months of testing and prototyping, GIW unveiled the Remote- ly Adjusted Mechanical Suction Liner (RAMSL). According to Leo Perry, GIW senior engineer, "Periodic adjustments to MDX cyclone feed lines historically have been made using hand tools. RAMSL al- lows for the adjustments to be made and monitored remotely at the touch of a but- ton." This makes the weekly gap adjust- ments much faster and more accurate, reducing the time needed per adjustment from hours to just a minute. Perry said GIW evaluated different options for the RAMSL, but finally de- cided to base the design on mechanical components in order to provide a more robust product with easy maintenance features and high operation reliability. "Other options were evaluated such as a hydraulic or pneumatic design, but all of them required more complex configu- rations adding potential points of failure and demanding more maintenance time by the end-user. "The RAMSL user interface serves as both the control panel for the operation of the unit and as an output source for crit- ical data taken from the pump, such as real-time vibration readings and precise movements of the suction liner (to within 0.01 mm)," he explained. This product enhancement carries two primary benefits: ease of maintenance and more efficient use of time and re- sources. "Both benefits stem from the ability to adjust the equipment against roughly 400,000 pounds of force from a safe distance without exerting more effort than it takes to press a button on a touch- screen," said Perry. Peripheral benefits include the ability to match maintenance schedules to best suit the needs of each pump installation, and RAMSL can also help minimize the potential for equip - ment damage due to over-adjustments caused by using traditional methods. And, there are long-term technology benefits associated with the project as well. "We are beginning to see how the collaboration of RAMSL with the internet of things (IoT) to collect and analyze data can benefit our customers in the area of predictive maintenance and inventory planning," explained Diwakar Aduri, GIW product development manager. KSB Group subsidiary GIW Industries develops a remotely controlled mechanical system for making critical, frequent adjustments to its MDX cyclone feed pumps at Minera Escondida.

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