Unplanned downtime has a sweet outcome for British Sugar
02 September 2010
When a worm gear drive crown wheel failed due to overload on a crucial conveyor belt at British Sugar’s Wissington plant in King’s Lynn, the priority was to get things up and running again quickly. A costly temporary measure was taken, but the impact of this was minimised by some pretty fast footwork by the original power transmission supplier
British Sugar’s Wissington plant in King’s Lynn processed over three million tonnes of beet this season alone, to produce a wide range of sugar products, including the renewable fuel, bioethanol. But this was not achieved without a particularly serious setback that threatened the plant’s throughput at a critical time in its production cycle.
In the run-up to Wissington’s busiest time of year, a conveyor at the facility feeding limestone and coke into a kiln that serves part of the sugar purification process had to be taken offline. A worm gear drive crown wheel had failed as the result of a conveyor overload, and two men and a shovel loader were subsequently hired to load the feeder manually around the clock. However, this was only ever going to be a temporary measure, not least because of the costs involved.
British Sugar approached Siemens Industry’s mechanical handling division, which had supplied the original Flender Cavex 280 worm gear unit in 1997. Any delivery delay could have affected the start of British Sugar’s next ‘campaign’ period and would also have meant no time for running in and appropriate checks. The company had already considered a refurbished competitor’s unit, but this had a lower rating than the Flender unit and it was not at all confident of its suitability for the task.
The Siemens service team suggested a more energy-efficient, bevel helical Flender FZG gearbox (size B3HH08). Where the existing 280 Cavex worm gear unit had a rating of 12,500Nm at 1,000rpm, the new Flender bevel helical unit was rated at 27,000Nm, a considerably higher torque rating. The bevel helical unit also fortunately had the same hollow shaft diameter as the Cavex worm gear unit, so the customer was able to use the existing head shaft. Even better, the unit could be supplied directly from Siemens’ Bradford factory. Moreover, the old unit was between 74% and 85% efficient, whereas the new one offered 95% efficiency, an improvement of at least 10%.
The new gearbox was actually selected and supplied all within eight days of British Sugar’s enquiry, against which drawings were also submitted with the quotation to ensure that the existing hydraulic motor would also fit.
The biggest bonus of all for British Sugar was the fact that the new unit cost less than a replacement worm gear unit would have done. As a spokesman for the company commented: “We’ve had great service turnaround; we have a new, more efficient gear unit with twice the rating, and at a lower purchase cost. It’s a great result as far as we’re concerned.”
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