Thames Water plant ups efficiency through gearbox replacement

London - Thames Water has replaced an old gearbox on a picket fence thickener sludge tank at its White Walham sewage treatment works in Slough, UK. The double-reduction worm gearbox had a single V-belt running from the motor to the gearbox and was proving to be very inefficient – running at just 60% capacity. The V-belt was also being used as a torque limiter on the unit meaning that if the tank paddle jammed, the belt would slip and shred requiring time-intensive mechanical work.

The replacement project was led by Brammer, which recommended installing a new modern gearbox - rather than overhauling the old unit, which had become obsolete, with spares no longer available for repairs. The team, in conjunction with Brevini Gearboxes, selected a standard planetary gearbox with an incorporated torque limiter as the best solution.

To install the new unit,  Brammer had to drain the tank and erect scaffolding inside to allow the old gearbox to be unbolted and uncoupled from underneath.
A local engineering firm manufactured a bespoke ball housing to bolt in between the gearbox and the sludge tank. The housing encases a Renold pin coupling and SKF thrust bearing and stub shaft to hold the weight of the sludge tank paddle.

The new gearbox has increased efficiency to 95%, according to Brammer. The integral torque limiter, it said, means that if the tank paddle jams the torque limiter will trip and will simply need resetting – providing time and cost savings for Thames Water as this negates the need for mechanical repairs.
The Brevini planetary gearbox can also be removed in the future without the need to drain the tank and pay for scaffolding inside.

“The installation of the Brevini gearbox will extend product life, reduce the need for costly maintenance and provide real energy efficiency savings for Thames Water," said Mitch Chambers of Brammer. "We have also taken the opportunity to standardise all parts used which will reduce working capital in the long term.”