Mining equipment solutions provider Weir Minerals Africa is expanding its range of pumps intended for use in high-head mine dewatering and general dewatering applications, including acid mine water drainage (AMD).

In April, Weir Minerals Africa expanded its range of submersible slurry pumps from two to nine models with the introduction of a new range of Warman heavy-duty slurry submersible pumps.

The first of the new models, currently in transit to South Africa, are expected to arrive within the next eight weeks.

The extended range of pumps will be trialled through the company’s rental store, providing more options for the company’s customers.

Rentals

“The rental model was introduced onto the market in 2009, with only nine pumps on offer for rental. The response to this market need has been positive and resulted in the growth of the rental fleet to in excess of 350 units available for rental throughout Africa today,” asserts Weir Minerals Africa rental and submersibles manager Howard Jones.

“Weir Minerals is continuously expanding its rental fleet throughout Africa, in line with customer and market demand,” says Jones.

He notes that the rental division was established, in part, owing to the global downturn, which limited some companies’ abilities to access additional capital expen- diture, thus preventing companies from buying new equipment, and customer demand for Weir Minerals to set up a rental store.

Vertical Turbine Pump

The company also recently introduced the Floway vertical turbine mining pump. Floway pumps are manufactured using Weir Minerals’ specialised materials for construction. The pump also features reduced vibration owing to the incorporation of the patented Thrust Pot, which increases the pump’s life span, reduces downtime and repairs, and lowers the overall life cycle cost.

Weir Minerals Africa dewatering manager Ian Farquhar notes that the low net positive suction head (NPSH) first-stage impellers, made from corrosion-resistant materials, are designed to meet low NPSH requirements, allowing for shorter pumps and barrels.

To date, the company has sold four Floway units to Zambia and ten units to Zimbabwe, all of which are being used at power stations.

The in-house three-dimensional solid modelling, hydraulic design, computational fluid dynamics analysis, stress and deflection analy- sis using finite element analysis, lateral and torsional rotor dynamic analysis, and structural natural frequency analysis have ensured that the pump meets the demanding application requirements, says Farquhar

Farquhar believes that all the features of the Floway could make it a reliable answer to the serious problem of AMD, which is negatively impacting on parts of Johannesburg and its surrounding locations.

Warman DWU Pump

Farquhar explains that the Warman DWU dewatering pump has been developed to further enhance Weir Minerals Africa’s existing high-lift dewatering range.

The pump was initially trialled for use in 2011 at the Foskor flotation and filtration plant in Phalaborwa, Limpopo province.

“The new Warman DWU dewatering pump design offers customers a high-head option, together with the required speeds for diesel and electrically driven applications, with heads exceeding 140 m,” says Farquhar.

The pump’s wet-end materials of construction include an SG 500 ductile-iron casing, SG 500 ductile iron suction cover, 27% chrome white iron sideliners, with a tempered 27% chrome white iron impeller, and an SG 500 ductile iron stuffing box, which uses the Warman WBH slurry pump bearing frame assembly.

“Using the new Warman WBH mechanical end design, operators can interchange parts, thereby reducing the stockholding of spares,” notes Farquhar.

He says the new compact design offers a 90% commonality of parts with the Warman WBH mechanical end, allowing for easy inter- change ability.

Farquhar asserts that this will further cut down on the spares holding owing to the ease of interchange of parts.

The one-piece frame aids the correct alignment of the bearings, seals and impeller. The pump’s large-capacity bearings are capable of withstanding high loads, thus ensuring long bearing life. The double-volute design implemented by Weir Minerals’ research and development engineers reduces radial loads, while the thrust reduction impeller design reduces axial thrust loads, thus enhancing bearing life.

The Warman DWU pump can be used in dirty water with a specific gravity of 1.05, and its casing is pressure-rated at 70 bar for series pumping.
The range comprises four pump frames, namely the Warman DWU 200, 150, 125 and 75. At maximum operating speed, the Warman DWU 200 pump will achieve a head of 130 m at best efficiency point, with smaller units able to achieve 140 m.

“The Warman DWU is a dirty-water pump that offers clean water efficiencies of up to 78%. This is an increased efficiency on the previous C5 Warman centrifugal slurry pump of about 11%,” states Farquhar

The Warman DWU can also be used on barges and pontoons.

Jones explains that the company is using Warman DWUs in place of traditional electric units, which would have a priming problem in this application. Weir Minerals places the suction end of the pumps into the water, while the pump and the motor are mounted at an angle above the water line. This ensures that the suction end of the pump is submerged at all times, preventing suction problems.

However, he adds that diesel sets cannot be mounted at an angle, as the diesel engine must operate on the horizontal plane to ensure that the engine is not starved of oil.

“Should a diesel engine be used, we install a vacuum-assisted priming system, which is controlled by means of probes. If, during an operation, the pump loses prime, the vacuum system will automatically start up and it will reprime the pump,” explains Jones.

He adds that this system has been successful in Australia and Indonesia and that, in the last 18 months, several of these systems have been put into operation on diamond mines throughout South Africa.

“Another option available to customers is the mounting of the pump onto a pontoon, skid or trailer, which allows for series pumping at base level,” explains Jones, noting that this gives operators the flexibility to move the pump around.

Weir Minerals Africa has standardised on Caterpillar engines; however, Farquhar adds that the customers’ preferences will always be accommodated.

As of May 8, the company had sold 59 Warman DWU pumps units globally. Thirty of the units were sold to China, while the rest were sold throughout Africa.