Hills Quarry Products reduce pump failures and cut maintenance and energy costs using variable-speed drive
HILLS Quarry Products have reduced pump failures and cut their maintenance and energy costs using an ABB variable-speed drive. As a result, up to 1,200 tonnes of aggregate per day can now be consistently processed at their Cerney Wick site, in Gloucestershire.
Aggregate production at Cerney Wick demands a high volume of water which returns to a sump for pumping to a settling bed. Float level switches in the sump activated a fixed-speed pump, but the fixed speed could be too high for demand, leading to the sump running dry and the pump failing.
Moreover, because the motor only ran at one speed, the stress on the pump set could lead to broken transmission belts, motor overcurrent or blocked pumps, leading to costly failures, typically every two weeks.
‘The pump could be out of action for a few hours to a full day, depending on whether it was a simple belt change or if the pump needed to be raised from the sump,’ said quarry manager Olly Thompson.
‘We extract between 1,000 and 1,200 tonnes of aggregate every day at Cerney Wick, so any downtime is extremely costly – not just in terms of lost production, but also due to the extra expenses incurred by our maintenance team and external contractors.’
Following a recommendation from ABB Value Provider APDS, a 55kW variable-speed drive (VSD) and level control device were installed to automatically adjust the pump motor’s speed according to demand, whilst a pressure transducer, installed in the sump, monitors water pressure. The VSD calculates the water level that corresponds to this measured pressure and adjusts the pump speed to avoid overflows or the sump running dry.
‘This system has reduced downtime, increased production and reduced the number of replacement drive belts as well as the cost of repairing the pump when it ran dry,’ said Mr Thompson.
‘As well as avoiding failures and the associated costs, we have also cut electricity usage on the application by around 50% by matching motor speed to demand, achieving further savings.’