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Reliability is the key

Drives and motors from ABB Automation are helping to maintain the production of chalk slurry for Rugby Cement's newly refurbished cement works in Rugby. A £150 million refurbishment will allow the plant to increase its annual cement output from 390,000 tonnes to 1,350,000 tonnes.

Two ACS 600 variable-speed drives and two ABB AC motors have been installed at the heart of the production process 57 miles away at Rugby Cement's Kensworth Quarry, near Dunstable, which provides all the chalk needs for the Rugby plant.

Because of the amount of capital investment and the impracticality of doubling-up on pipework, spares, changeover valves, pumps and motors, there are no back-up systems at the quarry. The slurry production facility within the quarry has had to develop its existing slurry plant to keep up with cement production at the new plant. Chalk is extracted at a rate of 900 tonnes/h and is then mixed with water in a 20m long and 4m diameter wash drum which turns the chalk to slurry.

The slurry is pumped over screens to separate out any large particles. Once through the screen, the slurry is pumped at a rate of 720m3/h into a 40m diameter and 12m deep storage tank. Here it is agitated with air to maintain a suspended solution of chalk in water. This operation uses two 132kW ABB motors (four pole, 415V) and two ABB ACS 600 drives, each rated at 160kW. From the storage tank the slurry is pumped along a 57-mile pipeline between the quarry and the new cement works.

The cement manufacturing process is governed by the production of slurry not the demand of the cement works. It is imperative, therefore, that the quarry can supply a steady flow of slurry. The storage basin acts as a buffer for this purpose and can provide enough slurry for four days full-capacity cement production at the new plant.

The drives were supplied through ABB Drives' alliance partner Sentridge Ltd of Coventry, who are also handling the site's maintenance agreement.

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