As IM goes to press on its March print issue and a feature on dewatering, sector leader Weir Minerals is stressing the importance of using a fit-for-purpose pump that can handle “dirty water”.
While the market offers specialised slurry pumps to handle thick and abrasive slurries, as well as submersible and sump pumps for pumping clean water, neither of these options provide an effective solution for pumping dirty mine water, Weir Minerals says.
The company has leveraged its extensive knowledge of pumping slurries and developed the Warman® DWU (Dirty Water Unit) pump, designed to handle both increased suspended solids in dirty water while operating at high discharge head pressures.
“The introduction of, and subsequent clogging from, suspended solids is one of the most common causes of premature failure in a dewatering pump,” Weir Minerals says. “‘Upset’ conditions during the underground mining process are the general cause of increased suspended solids levels entering the mine’s dewatering discharge water.”
The Warman DWU pump combats both these challenges, transporting the dirty mine water to its designated discharge point via single (140 m), multi-stage (480 m) portable, or permanent pumping solutions, the company says.
‘Dirty water’ is the name given to water with too high a percentage of suspended solids to considered be ‘clean’, but too low of a percentage to be classed as slurry, Weir Minerals says. “Dirty water becomes a problem onsite when the solids concentrate inside a dewatering pump collects around the motor frame, overheating the pump and causing the motor to fail.”
The Warman DWU pump is, Weir Minerals says, specifically designed to handle dirty water from onsite ponds and open pits with specific gravity of up to 1.05. Where a pump built to handle clean water will fail once dirty particles are introduced, the DWU pump will not, according to Weir. “That is because the DWU was designed using computational fluid dynamics and utilises Weir Minerals’ advanced material technology, allowing the DWU pump to process the fluid efficiently and minimise pump maintenance in the long run,” the company said.
Marnus Koorts, Product Manager for Pumps at Weir Minerals Africa, said: “In most circumstances, high-head clean water pumps will fail when they are required to process even a minute amount of particles. Once you have greater than 1% of particles, a site’s only other option is to install slurry pumps.”
Slurry pumps are commonly used to address the dirty water problem, but this solution is costly and inefficient, according to Weir Minerals.
“Without a specialised dirty water pump like the Warman DWU, up to three slurry pumps need to be sourced, installed, and maintained just to pump the dirty water as far as a single Warman DWU pump can,” the company said. “The pump utilises a new high-pressure casing to withstand pressures up to 7,000 kPa, enabling it to pump operating at maximum speed and achieve a head of 140 m at the best efficiency point.”
Koorts summarises: “This results in a lower total ownership cost and reduced downtime for the customer while providing them with increased efficiency and energy savings over using slurry pumps in the same application.”
The Warman DWU pump provides a solution to a fluid transfer problem that can quickly affect an entire operation, according to Weir Minerals. “By making use of the latest Warman WBH® mechanical end design, customers benefit from 90% common component interchangeability, allowing them to reduce stockholding of spares,” the company said. “In addition, the Warman DWU pump is available with either an electric or diesel motor and can be mounted on either a pontoon, skid, or trailer, which provides sites with the flexibility to move the pump around to where it’s needed.”
Koorts said: “Pontoon mounting an electric DWU pump allows for series pumping at base level or stage pumping out of an open pit. With Weir Minerals’ dewatering expertise we’re able to engineer a complete solution that places the suction end of the pumps into the water, while the pump and motor are mounted at an angle above the water line. This keeps the suction end of the pump submerged and eliminates suction problems. With a diesel driven pump, we install a vacuum assisted priming system that reprimes the pump when needed.
“Essentially, customers can set and forget.”
The Warman DWU pump provides a flexible dewatering solution to sites, not only in the portability around site, but in the range of fluids the pump is built to handle, Weir Minerals says. “In the nine years the pump has been on the market, Weir Minerals engineers have continued to improve the DWU’s capabilities.”
Although designed to handle dirty water, the Warman DWU pump is also able to process clean water with 78% efficiency, and the addition of a stainless-steel casing means the DWU pump is now suitable for highly acidic applications (pH >2), according to Weir Minerals.