Handling frothy and shear-sensitive slurries


The slurry pumps used in mining and mineral processing applications face a range of difficult operating conditions, often handling highly-corrosive and abrasive slurries with large amounts of (sometimes large) entrained solid particles. Specific applications bring with them additional challenges, however. These can include:


  • Frothy slurries with large amounts of entrained air.  
  • Slurries containing shear-sensitive solids, such as those used for carbon transfer in gold leaching processes.  


The challenge of froth


In applications such as flotation, concentrate slurries will contained significant amounts of entrained air. These frothy slurries require special consideration, as they perform differently to other slurries at the same pump speed.


The problem arises when the slurry contacts the impeller. Here, the entrained air expands in the low-pressure zone at the impeller eye, effectively blocking or seriously inhibiting flow – a condition known as air locking. This reduces the hydraulic performance of the pump, leading to an increase in the liquid level in the sump and rising pressure at the inlet. This pressure ultimately compresses the entrained air and forces it through the pump, resulting in a surge of slurry that can strain the bearings, impeller, and shaft, and result in increased wear.


As the pressure is released, the entrained air will again begin to expand and another air lock will form in a repeating cycle that causes significant fluctuations in pump performance. At the very least, this reduces productivity but, in severe cases, air locks can bring production to a shuddering halt.


Eliminate air locks with KREBS hMAX slurry pumps 


The traditional solution to air locking is to oversize the pump to account for the higher volume of air at the eye and deliver the required flow rate. But oversizing brings with it issues of its own, not least when it comes to energy consumption and pump efficiency. It’s also not the only solution.


KREBS hMAX pumps by FLS feature an alternative open-vortex impeller design that allows clear passage of air-entrained slurries without impacting duty flow and head. Constant recirculation also breaks-up an air bubbles that may otherwise block the eye, increasing pump efficiency, reducing power consumption, and minimising instability in the flow. As a result, KREBS hMAX pumps can handle slurries with up to 30% entrained air.


Handling shear-sensitive solids


KREBS hMAX pumps also provide a solution when handling shear-sensitive solids. Thanks to their heavy-duty concentric casing and recessed impeller design, hMAX pumps feature large internal clearances that allow for the passage of shear-sensitive solids through the pump without impacting or clogging the impeller. This makes them ideal for handling shear-sensitive solids; tramp materials also pass through the pump with ease. 


A further benefit of the concentric casing design is the reduction in radial loads, which significantly extends the life of the pump, seals, and bearings. 

Did you enjoy this article?

Then don’t miss out on our other blogs and continue the journey into the world of centrifugal slurry pumps.

Blog | Selecting a slurry pump for mining and minerals processing applications. 

Blog | Split-case slurry pumps: KREBS® slurryMAX™. 

Blog | Setting the standard: KREBS® millMAX™. 

Blog | Challenging wear conditions: UMD™ mill discharge pumps


You can also dive deeper and discover why KREBS pumps are the ideal choice for your slurry handling needs in the webinar. Or download the brochure and learn more about our innovative KREBS hMAX slurry pumps. For further information on how our reliable slurry pump parts can extend your pump's lifetime, feel free to contact us.