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Impeller and throatbush combination delivers wear life improvements

USING a novel integrated design approach, Weir Minerals engineers developed the Warman® WRT® impeller and throatbush combination – delivering significant wear life improvements in Warman® AH® pumps.

It began with an extensive research and development programme by Weir Minerals engineers, aimed at better understanding the wear characteristics at the inlet and outlet of centrifugal slurry pump impellers. This was done as part of Weir Minerals’ drive to reduce total cost of ownership on its range of products. The culmination of the project resulted in a new impeller and matching throatbush design which provides Warman® AH® pump users with significant advantages.

Leveraging years of wear data on the popular Warman® AH® pump design, the design engineers compared this ‘real world’ data with computational fluid dynamics (CFD) simulation. This allowed them to obtain the correlation between predicted and actual results for the standard five vane slurry impellers.

The resulting design for the new impeller incorporates a unique vanelet on the back shroud which streamlines the flow through the impeller outlet. This improvement also provides higher efficiency and therefore lower absorbed power and improvements in the net positive suction head (NPSH) performance.

Put to the test recently on a gold mine with significant clay content in its slurry feed, the Warman® WRT® impeller and throatbush combination excelled. The mine faced the challenge of its high clay content leading to increased slurry viscosity. Also, the clay contained sharp, coarse quartz particles that caused high impact wear on the leading edge of the impeller vane in the installed pump.

The mine needed to increase its throughput, but the incumbent competitor impeller was unable to maintain the required level due to the viscosity of the slurry. The Weir Minerals team recommended the Warman® WRT® impeller and throatbush combination, which were retrofitted into the Warman® pump.

After installation, the Warman® WRT® impeller worked so well that the variable speed drive (VSD) reduced whilst delivering the same throughput. These results were due to the new WRT® impeller with its lower NPSH characteristics and ability to pump the viscous clay slurry without cavitation.

The pump was inspected after 1 200 hours of operation with the Warman® WRT® impeller and throatbush. The Warman® impeller showed some wear on the impeller vane leading edges, but practically no wear on the front shroud. The Warman® pump with WRT® technology went on to achieve 1 500 hours of wear life, an improvement of 125% on the average wear life of 670 hours for the competitor’s impeller.

This achieved a considerable saving for the mine, due to the higher efficiency of the impeller, less solid recirculation, longer wear life of both items and fewer pump rebuilds. The technology also facilitates savings in energy costs as the pump consumes less power.

The WRT® parts are interchangeable and can be retrofitted into all current Warman® AH® pumps. This can be done during a normal maintenance shutdown, when the two standard parts can be removed and the Warman® WRT® parts installed. All setups, fitment and general maintenance remain the same. No speed change is required, nor are any specialised tools for fitment.

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