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Dewatering in mining projects

Published by
Global Mining Review,

The deeper the pit, the more difficult the dewatering process. When conventional pumps reach their limits, multi-level pumps are the solution.

The global race to secure scarce resources is well underway. Deposits are now being mined that were either economically unviable or were impossible to obtain a few years ago. Also, infrastructure projects, such as the Gotthard base tunnel, are becoming increasingly ambitious, which poses challenges to the dewatering processes.

Distances cannot always simply be bridged with conventional submersible pumps, it is the vertical distances that are decisive. Most pumps can only pump to heights of between 10 and 40 m, but even these values are relative. In practice they can only lift a small part of the stated maximum pumping capacity to this height because the greater the height, the less water passes.

Switching pumps in series

Some operators work around this problem by using a series of pumps; two pumps that are operated sequentially in one section. This will almost double the achievable distance, although the pumping capacity remains the same. Usually, hoses are fitted between the aggregates. The problem with this concept is that the same core risk associated with all complex systems applies. Too many components, often not in their best condition, are not correctly installed or should not have been combined in the first place.

Tsurumi has manufactured an adapter that allows two pumps to be directly coupled to create a more powerful single pump. However, the limiting factor is the physics of the speed and impeller, which is why many manufacturers’ pump programmes end at this point.

If this is insufficient for the dewatering process, things become difficult for tunnel builders and miners. In contrast to clear water, there are few pumps in the dewatering field that can improve the output.

If you want to pump higher, then multi-level pumps are needed. Technologically speaking, this means that several impellers are mounted inside the casing. Whilst the pumping capacity remains the same, the pumping height increases with the number of these levels. The pump supplies more pressure and is therefore able to reach a higher head.

The LH4110W is the premium model of this type of pump. It is able to pump waste water vertically to a height of 216 m. The aggregate can move 400 l/min. If requirements are lowered, for instance to a pumping height of 170 m, the pumping output is increased five-fold to 2000 l per min. The power required for this is generated by a 110 kW motor.

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