UNDERSTANDING AND SELECTING MINE DEWATERING PUMPS

Don't get flooded out... understanding and selecting mine dewatering pumps

Posted on 11 November 2020

Selecting a mine dewatering pump is crucial in obtaining the precious minerals - therefore a suitable and adequate pump is vital to the mine’s success. In order to help you select the right dewatering pump for your site, Global Pumps have shared their experience in this blog…

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What is dewatering?

Dewatering is the process of removing groundwater or surface water from a site - typically mining and construction sites, to lower the water table to ensure operations can be carried out safely and efficiently.

On a mine site, dewatering is usually an ongoing process, and is crucial in accessing underground minerals. While on construction sites, dewatering is required before works such as digging and drilling can start on sub-surface excavations.

Water can be an obstacle to excavation efforts, and if the water levels are not controlled, there are a number of negative impacts - not only on the efficiency and economic viability of a project, but also the safety of the workers.

What is a dewatering pump?

A dewatering pump is pump installed below groundwater level, to reduce the water level and then maintain it at this level.

Installing a dewatering pump offers mine sites great cost savings, including: fewer explosives required to clear out dry environments, dry ore and waste material weighs less and is easier to move, better working conditions leads to less down time and improved structural integrity of the work area is a safety benefit to all.

What do you need to know when selecting a dewatering pump?

If the pump selected is too small, or there is an insufficient number of them, there is the possibility of being flooded out and subsequently losing equipment and operational time. On the other hand, if the selected dewatering pump is too large, the motor could burn out due to too many starts per hour. The motor would not have enough time to cool off prior to recommencing. The pump could also experience suction cavitation, which occurs when the pump is ‘starving’ for water.

Therefore, Global Pumps suggest the following key considerations prior to selecting your dewatering pump:

Static head: As with any pump, you need to determine the static head that it needs to overcome - if the pump cannot produce enough pressure to overcome the vertical distance, the required flow will not be achieved.

Flow rate: What is the flow needed to properly remove the amount of water in order to keep the mine dry? During this stage, you would also consider what style of pump is most suited for the application. If the pump is self-priming, what is the length of the suction line? It is important the size of your suction line is equal to, or greater than, the size of the suction or inlet port - this will reduce the possibility of suction cavitation. 

Depth of the underground sump: The available net positive suction head (NPSHa) is the static pressure available in the system to force the water into the pump. The type of pump selected largely influences the NPSHa.

The NPSHa is affected by several variables, relevant to the specific environment, these may include:

  • static differentiation between the pump’s suction and the water level
  • length of the suction pipeline
  • pump’s elevation above sea level
  • temperature
  • specific gravity

It is crucial that you consider the required pressure the mine dewatering pump needs to perform. Every pump has a minimum NPSH requirement to ensure it offers continuous flow - which depends on its operating duty point. Therefore, the net positive suction head available (NPSHa) must be compared to the net positive suction head required (NPSHr) when selecting a dewatering pump.

Global Pumps recommend that NPSHmust always be more than NPSHr, ideally between 1-1.5 m safety margin to prevent any risk of suction cavitation. 

Capabilities of the pumping system: Due to the nature of dewatering pumping, the efficiency of the pumps may change. As the pressure changes due to wear, or other factors, the pump's performance may move away from the best efficiency point (BEP).

If the pump selected is too small, or there is an insufficient number of them, flooding out or the loss of critical equipment and operational time could occur. Conversely, if the pumps are too large, the motor could burn on the pump due to many starts per hour. The motor will have no time to cool off before starting again, and the pump could experience suction cavitation as it is starving for water. 

 

Want to learn more?

Are you ready to discuss your mine dewatering pump? Or maybe you're stuck on a few considerations listed above? If so, get in touch with Global Pumps! Our team have worked closely with maintenance and site managers to ensure the optimal dewatering pump is selected. 

Tags: Dewatering pumps, mine pumps, mineral processing

NOT SURE WHERE TO START

Guide To Selecting the Best Pump

If you need some guidance on how to select the right pump then you’re not alone! There’s such a wide range of pumps in Australia, from centrifugal pumps to hose pumps to diaphragm pumps. The options available to you can make it a difficult choice, so we’ve created this special guide to help step you through the process of selecting the ideal pump for your requirements.

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