Effective dewatering sits at the heart of modern mining. It ensures operations remain productive and that the mine can continue to function safely and sustainably. When water isn’t properly controlled, access to mineral deposits becomes limited, and reliance on external clean water supplies quickly increases.

The process – where excess water is taken from open bodies, pits and shafts is used in a wide range of applications from the cost-effective transfer of minerals suspended within the medium – eliminating the need for conveyors, trucks or other equipment, to the feeding of other equipment for cooling, filter presses or attrition cells. Removal of excess water also ensures access to valuable stone reserves below the current water level, which was an application we were recently contacted about. 

A client in the mining industry were looking to standardise two pumps in operation at one of their quarries. The pumps were being utilised to dewater a pit and enable access to stone reserves required for a cement manufacturing process.

The pumps had been installed for several years and were different models from different manufacturers. In effect, they had two different pumps for the same application with different motors and pump sizes.

This gave our client three major problems:

• Lack of Redundancy – Differing Power Requirements and shaft sizing meant that neither the pumps or motors were interchangeable, and that units were using more energy than necessary meaning savings could be made in energy consumption
• Excess Spare Part Holding – Due to 2 different models of pumps being used, twice the number of spare parts were required to ensure if either broke down, they could be serviced
• Lengthy Lead Times – Manufacturers were quoting long lead times to supply both replacement pumps and spare parts

We worked closely with the customer to specify the best pumps for this application, which meant they had to be fully interchangeable, as well as being able to deliver the required flow and pressure at a lower installed power.

Whilst we had numerous design options for multistage pumps, for this particular project we specified two of our end suction horizontal centrifugal multistage dewatering pumps from our XMZ range. These are capable of high pressures - up to 45 bar and flow rates of up to 400m³/hr, however they are closely related to our XM range which can handle pressures up to 950M Head, and flows of 800M³H for deep mining applications.

In addition, they are engineered for continuous operation thanks to additional bearings located with the pump head. These not only remove strain from the motor bearings during operation, but also help balance thrust ensuring the stability of the pump shaft during operation.

Our XMZ horizontal End suction multistage pumps are of end suction design which feature a horizontally designed suction port which provides a strong suction, as friction losses are minimised. It also meant in this installation that pipework modifications were not necessary.

Multistage Pump Design

Multistage pumps are assembled utilising multiple closed impellers, with diffusers assembled with sacrificial wear rings to enable the unit to deliver very high pressures efficiently. The wear rings and diffusers protect the casing and impellers from wear by reducing recirculation flow. Normally due to the tight clearances in such pumps, the solids handling ability is extremely limited, however if pumps are oversized sufficiently, clearances are large enough to allow the passage of small solids, provided adequate filtration is used at the inlet of the pump.

Surface mounted dewatering pumps offer superior longevity to submersible designs, due to pumps being installed outside the pumping medium which is often aggressive and corrosive in nature to elastomers which are difficult to protect in submersible pumps as motor cables are often exposed. Maintenance is more proactive as operators are more likely to notice leaks, or abnormal sounds early without having to remove the unit from pits, and stop operation which isn’t always practical when mining.

Such designs offer far simpler maintenance, with most key components readily available worldwide for quick sourcing during servicing or unexpected breakdowns. They can be adapted for self-priming operation either through the use of a foot valve, or installation of a priming pump, eliminating the need for submersible designs entirely.

Surface mounted pumps are not just lower maintenance, they also tend to be built more robustly than their submersible counterparts.

Outcome

As the existing manufacturers of the 2 pumps on site were quoting excessively long lead times – twice as long as the timescales we presented the client, they reached out to us to determine the correct duty point for their application.

After visiting site and agreeing on the right pump specification, North Ridge supplied two high pressure multistage pumps, with a spare bareshaft pump which could quickly be installed when the existing pumps needed servicing.