Using a novel integrated design approach, Weir Minerals engineers have developed the Warman® WRT® impeller and throatbush combination, which delivers significant wear life improvements in Warman® AH® pumps.

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Weir Minerals engineers have developed a new WRT® impeller and throatbush combination for its Warman® AH® pumps, which delivers significant wear life improvements.

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.

Wear life improvements for Warman AH pump

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

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

Put to the test recently on a gold mine with significant clay content in its slurry feed, the WRT impeller and throatbush combination excelled. The high clay content leads 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 new WRT impeller and throatbush combination, which were retrofitted into the Warman pump.

After installation, the impeller worked so well that the variable speed drive (VSD) was able to reduce pump speed whilst delivering the same throughput, due to the lower NPSH characteristics of the new impeller and its 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 impeller showed some wear on the vane’s 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.

New 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 new impeller and throatbush installed. All setups, fitment and general maintenance remain the same, no pump speed change is necessary, nor are any specialised tools for fitment required.

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Crown Publications, one of South Africa’s largest business-to-business publishing houses, came into existence in 1986. Since then, the company has grown from producing a single magazine, Electricity SA (renamed Electricity+Control), to publishing six monthly magazines, three quarterlies, and a number of engineering handbooks.