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The Scottish Water sewage treatment works in Glendevon has called upon the services of Brevini after two of its thickener drives were deemed to be obsolete.

Recent energy price rises and a growing awareness of its carbon footprint has prompted Scottish Water to audit the efficiency of the equipment at its Glendevon site.

During the audit the drives of two thickeners were deemed to be obsolete.

The Combidrive double-reduction gearboxes provided an output speed of 0.04 to 0.082rpm with an output torque of 9,291Nm.

The drives produced poor energy efficiency and were in danger of failing.

Due to their size, a site will not have a stand-by option if one fails, if one does go out of commission other thickeners have to take on the extra load.

For this reason it was imperative that a solution was found quickly before the drives became completely redundant.

Scottish Water contacted Brammer who were quick to recommend Brevini, a specialist in no-engineering drive solutions for water treatment works.

Typical solutions such as replacement or repair were unfeasible.

A complete replacement would involve the re-engineering of the thickener’s structure, which would be extremely costly and time consuming.

Alternatively, repairing the existing drives would be inefficient as it would only provide a temporary solution.

As well as initial cost it is important to consider running costs as drives with poor energy efficiency will have an impact on a site’s energy consumption.

Planetary gearbox specialist Brevini was able to provide an alternative solution that would allow the gearboxes to be replaced without having to re-engineer the mounting bracket.

Jon Snaith, managing director of Brevini UK, said: ‘This particular project had a number of difficulties to overcome.

‘First, the two drives were supposed to be identical.

‘However, on closer examination and measuring it was determined that through age and usage some of the bolt hole patterns and holes had elongated and stretched making the design of the new solution very difficult because we had to make sure the one design would be able to be installed on either tank.’ The planetary gearboxes use three planetary gears mounted in two rows of needle bearings, this leads to 98 per cent efficiency per stage.

The overall ratio of the planetary gearboxes installed was 17,512:1; they had a continuous torque rating of 13,000Nm and a maximum torque rating of 20,000Nm.

The gearboxes now run at 90.4 per cent efficiency.

Due to the high reduction ratios possible with a planetary gearbox a far smaller motor is needed to power them, meaning a site can run with less energy.

The theoretical life expectancy of the gearboxes added at the Glendevon site is in excess of 200,000 hours.

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