Modern Mining April 2021

PUMPS AND VALVES

example, presents a number of issues for valve selection. Large particle sizes, high percentages of solids and high specific gravity (SG) make valve selection critical to ensure the least possible down- time. Separation processes, on the other hand, including hydrocyclones, classifiers and flotations process large volumes of slurry, classifying it based on different sizes and/or specific gravity (SG). It is challenging to securely isolate the high density slurry produced by these processes. To provide a reliable solution, you will need a self-flushing, pocketless design. Weir Minerals’ Delta Industrial Series 15 valve is ideally suited for these requirements. Secondly, the type of media that goes through the valve is crucial in influencing the choice of valve. “There is need to establish whether it’s fine or coarse material, or whether it’s gold or platinum, for example. That will help you choose a valve that is compatible with that type of material,” he says. Application conditions also play a critical role in the selection process. “It’s important to establish whether there are any chemicals in your slurry, so that one can select the body material suited to those conditions,” says Diphare. Leaching processes, for example, provide some of the most difficult oper- ating conditions for valves. This process typically involves high wear applications coupled with highly corrosive fluid and often high temperatures. The design features of Weir Minerals’ Delta Industrial valves provide superior wear and isolation capabili- ties required in these difficult applications. Another factor to look at is actuation. “Establish whether you will be operating the valve pneumati- cally or electrically. In remote areas where electricity may be a problem, for example, electric actuation may not be ideal. If you have a compressor on site, then you can choose pneumatic actuation. It’s all dictated by what’s available on site and the mainte- nance requirements.” Operating conditions, adds Diphare, also play a crucial role in selecting the right valve for the applica- tion. For example, if operating close to the sea where the atmosphere is quite corrosive, it’s important to choose the correct body material like stainless steel. Key trends Commenting on some new industry trends in the pump sector, Koorts says there is an “increased appetite” for rubber liners in the market. “Rubber is getting increased attention, especially on larger pumps. There have been some recorded successes in certain applications where it actually outlasts metal liners. It also comes at a cost-effective price, and it’s lighter and easier to handle,” says Koorts. With the mining industry’s drive for large ton- nages, Koorts also notes a trend towards big plants in the sector, which in turn calls for larger pumps. It was only in the 1990s when a Warman AH 20/18 pump was one of the largest available. Now it is

regarded as a medium sized model, eclipsed by the likes of the mammoth Warman MC 760 pump. The rising demand for cost-effective valves is one key trend noted by Diphare on the valve side of things. This, he says, is in line with the mines’ renewed approach to prudent capital allocation and expenditure. “Due to the current tough economic conditions, we have noted/observed that customers don’t wish to hold large amounts of stock because they regard stockholding as idle capital they could allocate to more pressing needs in their businesses. They there- fore expect the supplier to be able to deliver these components within a short timeframe,” says Diphare, adding that Weir Minerals is equipped to meet these needs through its network of local branches across the African continent. In conclusion, Diphare also notes that customers are demanding ease of maintenance to reduce costly downtime. “They don’t want valves that require com- plicated tooling, for example,” says Diphare. 

Isogate knife gate valves in a tailings application.

Key takeaways  Given that pumps and valves used in mining applications are subject to some of the harshest and most demanding conditions, it is important to select the most appropriate components for each specific application  A principal factor in the selection of pumps is energy efficiency  Once it has been determined what the operating requirements are, it is vital that the valve selection is based on accurate process information  With the mining industry’s drive for large tonnages, Weir Minerals Africa has noted a trend towards big plants in the sector, which in turn calls for larger pumps

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April 2021  MODERN MINING  23