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Ending the nightmare of wet-wipe pump blockages

An ingenious device developed in partnership with Scottish Water promises to reduce wastewater pump maintenance by detecting and clearing wet wipes on the impeller

A wastewater pump that has become blocked by wet wipesA wastewater pump that has become blocked by wet wipes

-This WWT Insight Report is produced in association with Clearwater Controls

Wet wipe and rag blockages still present a massive headache each year to the water industry, costing millions to remove or repair and replace affected assets.

As well as the labour cost of manually lifting and cleaning pumps, there is a significant associated energy cost: pumps that are impeded by rags will naturally have to run longer and consume more energy in order to maintain the required liquid flows.

If a pump becomes severely clogged, it will trip, and the blockage can be addressed. But what about pumps that get partially blocked - not enough to trip, but enough to reduce efficiency and lead to excessive run times and unnecessary energy consumption? This could account for the vast majority of wastewater pumps impacted by ragging.

Much is done to improve customer habits, via advertising campaigns, and yet the problem seems to continue unabated.

There have been many solutions proffered to address the issue of ragging, but one simple but ingenious invention now seems to be gaining more and more momentum.

It is a UK invention, developed initially in collaboration with Scottish Water, and now gaining adoption in global regions, including the United States, Canada and Australia.

Like all the best innovations it is simple, but very ingenious. A small (35mm by 100mm by 115mm) device called the Deragger II retrofits into an existing control panel, and then measures in real-time the power and wave-forms to a wastewater pump.

The real-time measurement allows the device 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.

The reversals are all performed in accordance with pump manufacturers’ recommendations.

The pioneer in this new technology has been Scottish Water. Numerous sites have been implemented, and now due to the Deragger II’s capability to monitor in real-time almost all the operating conditions and parameters of the pump, the benefits are being very carefully monitored and recorded.

The Burnside Sewage Pumping Station had Deragger II devices implemented on four pumps, 2 foul pumps and 2 storm pumps. The results were a substantial reduction in blockages, energy consumption reduced by up to 46.8%, and labour costs reduced due to the removal of manual cleaning processes.

Other Scottish Water sites include Shiresmill, where blockages were removed and energy reduction reduced by up to 39%. There was also the added benefit that by removing blockages, the run current of the pump no longer exceeded the operating current. By facilitating such an improvement the Deragger II will help extend pump life.

Not all the savings will be as high as thirty and forty per cent, but even on small pumps, quantifiable energy savings are being achieved.

What does the future hold for the Deragger II? Clearwater Controls Managing Director Simon Crompton comments: “With any new innovation it is about proving the benefits and non-stop perseverance. With more and more case studies coming in from UK and abroad, detailing and evidencing the tremendous benefits the device delivers, we are confident we can finally make a huge impact on the issue of wet-wipe style ragging blockages.”

-The Deragger II has been shortlisted in the Most Innovative Use of an Existing Technology category at the Water Industry Achievement Awards, to be held on May 23rd. wwtonline.co.uk/awards

Topic: Innovation , Pumps & Pumping Systems
Tags: wastewater , pumps , Scottish Water , Innovation , ragging


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