South African-based manufacturer APE Pumps has recently refurbished serveral concrete volute cooling water recirculation pumps for a southern African power station.
The cooling-water pumps at this power station comprise very large, single-stage vertical machines manufactured by APE Pumps in 1983. They have run to specification for 30 years, each one transferring water at a rate of just under 6 tons per second (5.8 m3/s).
Responding to the request by the power station for a higher flow rate, APE Pumps commissioned research by parent company WPIL into the feasibility of modifying the impeller design.
WPIL proposed a re-designed impeller that would increase the output of each pump by almost seven percent, from 5.8 - 6.2 m3/s, but which would also fit into the existing concrete volute housings, which are fixed and cannot be changed.
When the pump refurbishment programme is complete, the combined additional output of all twelve pumps will be 4.8 m3/s, equivalent to an additional machine at the current, reduced, rate of flow of the units already installed, all of which are suffering diminished efficiencies owing to age.
The net effect will be to allow higher operational turbine efficiencies and additional electricity output from the power station.
In addition to refurbishing the original pumps, APE manufactured one new machine to be used as a changeover unit to allow the power station to continue operating while the original pumps are removed one at a time for refurbishment in Wadeville.
