Water & Wastewater Treatment

6 WWT PUMP AND VALVE SUPPLEMENT 2018 In Focus: wastewater pump ragging could prevent these problematic blockages from occurring. The device The DERAGGER is one example of such innovation. It is a small (35mm by 100mm by 115mm) rail-mounted device which retrofits into an existing control panel, and then measures in real-time the power and wave-forms to a wastewater pump. It works by detecting tiny changes in flow rate, run time, variable frequency, drive speed and power consumption in the pump, which can indicate the presence of a rag on the impeller at a very early stage. It then reverses the pump temporarily until it dislodges the rag allowing it to re-enter the wastewater flow. The device is sensitive enough to detect when even a single wet-wipe starts to impede the impellers. On detection, the device momentarily stops the pump and puts it into reverse motion in order to dislodge the obstruction, before returning it to forward motion in order to pass it along the network in suspended flow. The device can be set up to reverse upon detection of rags, upon an increase of torque or at set intervals, thus preventing the build-up of rags and the associated increased wear on the pump and increased use of power. Invented in Scotland, the DERAG- GER has already been installed at 270 sites, many of them Scottish Water assets. However, the trial was intended to demonstrate to the English water companies the type of sites that the device is most suitable for and the benefits and return on investment that it could achieve. The study The trial saw the DERAGGER installed at five sites, one of these owned by Wessex Water and the other four belonging to United Utilities. Thames Water and Jacobs were among the organisation with a watching brief on the trial. The sites were chosen to cover a range of pumping station configurations and conditions: wet and dry wells, large and small pumps, pumps that had a history of blocking and those that did not. "We knew that the DERAGGER worked well when applied to badly blocking pumps, but what we were particularly keen to understand was what was happening when it was applied to pumps that weren't regularly tripping – which, a"er all, is the bulk of the network," explained Clearwater Controls Managing Director Simon Crompton. "We wanted to be able to show the energy-saving benefits of using it as a wider solution in the network." The sites involved were monitored

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