Dublin Bay wastewater treatment works cuts maintenance costs11 April 2013

Maintenance costs and out of service hours of a critical pumping application at a Dublin Bay wastewater treatment works have been slashed by using a variable-speed drive's anti-ragging routine.

The Ringsend wastewater treatment works, operated by Celtic Anglian Water (CAW), runs three 90kW pumps to transfer accumulated water from six storm tanks back to the plant for treatment.

The 62,000 m3 storage tanks are used during times of high rainfall to hold the storm flows and act as buffers for the plant.

The pumps were prone to ragging, caused by debris fouling the inlet – meaning that pumps had to be removed, stripped down and cleaned, before being re-assembled and lowered back into their housings.

At least one pump would need to be lifted at every storm event, with all three sometimes needing attention simultaneously due to heavy ragging.

But Brendan Riley, CAW's site maintenance engineer, explains that using an overhead lifting beam, electric hoist and maintenance team, meant the procedure was costly and time-consuming. Two fitters were needed for each operation, which could take a full day, he says.

So Riley turned to ACS Drives and Control Systems, a member of the ABB Drives Alliance, to provide a solution.

"We had worked with ACS on a small sludge transfer pump that also suffered frequent ragging. ACS installed a trial drive free of charge to prove the effectiveness of the ACQ810, which eliminated the problem. They then installed a 90kW trial drive in a similar way and it delivered the same result," he says.

Riley reports that, during the month long trial, no blockages were experienced and there was no reduction in flow. Following the trial, a permanent installation was provided for all three pumps, since which time CAW has not lifted any of the pumps once.


"By preventing blockages in the storm return pumps, the ABB solution has improved the reliability of the whole storm return operation, cutting the labour required and reducing the risk of returning untreated water to the environment," comments Riley.

"Since installation in July 2012 we have not had to lift a pump for cleaning."

The ABB ACQ810industrial drive is equipped with several intelligent functions, one of which is an anti-ragging technique. When the function is triggered, a cleaning cycle initiates. The function enables the drive to automatically perform preventive maintenance on the pump.

Brian Tinham

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