The installation of ABB ACQ810 water industry specific drives has almost eliminated pump ragging problems at a major waste-water treatment works in Ireland.

Celtic Anglian Water (CAW) is the largest private provider of operations & maintenance solutions for water infrastructure in Ireland. The company operates and maintains the Ringsend Wastewater Treatment Plant for Dublin City Council, which is amongst the largest and most advanced wastewater treatment plants in Europe.

The Ringsend treatment works uses three 90 kW pumps for transferring 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 within the plant.

Reducing maintenance

The pumps were prone to ragging, caused by debris fouling the pump inlet and preventing them from operating normally. When this occurred, the pumps had to be removed, stripped down and cleaned, before being re-assembled and lowered back into their housing.  This task could take a full day, and at least one pump would need to be lifted every storm event: sometimes all three.

An ABB ACQ810 90kw inverter drive with water industry specific was installed for evaluation.  One of its functions is an automatic pump cleaning technique. When the function is triggered, a cleaning cycle is initiated and operates in a number of user-defined cleaning cycles. The function enables the drive to automatically perform preventive maintenance on the pump. The cleaning trigger commands are very flexible and adaptable to each process.

During the month long trial period, no blockages were experienced and there was no reduction in flow. Following the trial, a permanent installation was provided for all three pumps.  In the following year, CAW have not had to lift the pumps once.

One of the major advantages of the solution is that the drive can take in a signal from an external flow meter mounted to measure the output from the pump. The standard way of detecting flow problems is to react if the pump is drawing a higher than normal current or torque as it tries to deal with the extra load. This method of detection is not always reliable and can be too late as the blockage has already reached a critical stage and cannot be undone easily. Equally the pump characteristic can be such that the load will actually drop, like deadheading, thus rendering this method unreliable. The ABB drive takes action before things get critical, instigating the cleaning cycle once the flow rate starts to drift away from the nominal rate.

By preventing blockages in the storm return pumps, the ACQ810solution 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.

ABB drives are available from 999 Inverters UK