Mechanical Technology March 2016

⎪ Pump systems, pipes, valves and seals ⎪

State-of-the art pumps for Sishen’s modular pump station Following the delivery of a first-of-a-kind modular pumping plant to Sishen earlier this year – a system constructed, tested and commissioned under factory conditions in Efficient Engineering’s Germiston workshops – MechTech talks to KSB’s Gideon Rochér (right) about the pumps used for the installation and his company’s local offering.

“ F or KSB, this project dates back to February 19, 2015, when we were approached by Chris van Aardt of Ef- ficient Engineering, who had been sent pump specifications from consulting engineering company, Aurecon. After some telephone conversations, emails and meetings, we came to a suitable pump specification for the duty and elevation required for the Sishen site,” begins Rochér. With Sishen’s open pit getting ever deeper, an additional dewatering pump station was required to provide an ad- ditional flow of around 1 800 m 3 /h into a 40 m head. Water from the mine’s iron ore pit is pumped into a reservoir and then gravity fed into the Vaal Gamagara municipal system. “Four pumps were specified, each with a nominal flow capacity of 600 m 3 /h, giving a total flow capacity of some 2 400 m 3 /h into the 40 m head. This is quite substantial,” Rochér suggests. “Along with my mentor at that time, Louis Opperman, who was a stalwart of South Africa’s pumps industry, we looked at supplying two larger pumps to the project to meet the required flow. “We were surprised at how much more expensive it would have been to go this route. By the time the costs for the larger pumps, motors and switchgear were factored in, it would have been 25% more expensive to use two pumps instead of the four originally specified,” he tells MechTech . The pump model chosen for the project was the KSB Omega 200-420 A. “These are each capable of pumping above the 600 m 3 /h (167 ℓ /s) requirements. They have a 200 mm discharge, impellers with a 420 mm diameter and an A-hydraulic impeller, which signified the highest duty and efficiency hydraulic selection for this impeller size,” Rochér explains.

KSB Omega pumps have axially split casings with an in-line design. Notable features include: a short distance be- tween bearings on a correspondingly short shaft; a compact joint flange with long, pre-stressed bolts to ensure leak- tight operation; a counter-rotation feature using identical internal components; and a self-aligning upper casing for easy mounting. The high-performance computer op- timised impeller is designed for double entry – flow enters the impeller from both sides simultaneously to minimise axial thrust – and the vane passages offer ex- cellent hydraulic characteristics. A large impeller eye area and a swirl-free, low energy loss inlet also Sishen modular plant, have been fitted with PT100 tem- perature sensor systems (thermis- tors) to continuously monitor and transmit bearing temperatures to the controller,” Rochér notes. For additional longevity and corrosion protection, Rochér informs us, the cast volutes of the pumps for Sishen’s modu- lar pump station were specified with 400  µ m glass flake linings. “This is a polyamine cured epoxy coating reinforced with glass flakes. It forms a hydrophobic surface that, as well as resisting erosion and corrosion, significantly reduces hy- draulic/friction losses in the pump,” he explains, adding that the internal compo- nents of these Omega pumps – impellers, shafts, seals and wear rings – “are all made from 316 stainless steel.” From a service perspective, shorter aid smooth and quiet running. “In addition, these pumps use sealed for life bearings, which, for the

shafts offer better rigidity for reduced vibration. Assembly is also adjustment- free, with quick and easy assembly/ dismantling of the rotor components due to the elastically pre-stressed mountings. Cartex 70 mm mechani-

cal seals, supplied by Dutch company, EagleBurgmann, were fitted to each of the pumps, which were then mounted on base plates and coupled via Fennaflex

KSB Omega axially split volute casing

pumps feature: a double entry impeller to compensate

for axial forces, reducing the load on the maintenance-free bearings (1); solid bear- ing brackets, a short and rigid shaft and pre-loaded bearings for lower vibration and extended operating lives of bearings, seals and couplings (2); the self-centring upper part of the casing and spring-loaded rotor enable cover and rotor assembly without any adjustments (3). F120H flexible couplings to 110 kW IE2 motors from Zest WEG. “At best efficiency, the pumps ab- sorb 79 kW each running off VSDs at 1 270 rpm. This creates the room to increase the flow rate when the demand arises, without taking the system too far

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Mechanical Technology — March 2016