Articles & Case Studies

COLCHESTER PUMPING STATION – A STUDY IN ENERGY CAPTURE

Posted: Tuesday 8th January 2013

Modern pumping stations require equipment which reduces energy consumption and cost. We profile one pumping station that switched to energy efficient Flygt pumps and saved more than £77,000 per annum.

Old and unreliable pumps can be costly for pumping stations not just from years of wear and tear, which can lead to increased site call-outs and maintenance costs, but also due to energy consumption issues. Colchester Inlet Pumping Station was subject to a full efficiency survey by Panks, Alliance Partner with Xylem Water Solutions, which returned impressive results.

Station at risk

Colchester Sewage Treatment Works was founded in 1969 and is the primary pumping station in the area helping to serve a population of approximately 115,000. This pumping station is critical to Anglian Water and in 1995 action was taken to replace the ineffective vertical SPP spindle pumps, in an attempt to stop the regular blockages.

Paul Fookes –Business Development Manager at Xylem, takes up the story:

“30 years after its opening, a major capital refurbishment project was put in place to address the recurring pumping problems at Colchester STW which houses a total of six pumps. The original vertical SPP spindle pumps were removed and new dry well non-Flygt submersible units were installed.”

Paul Fookes continues: “A considerable amount of money, time and effort was spent on trying to improve the performance of these new pumps and several different impellers were tried without success. After two years these pumps were abandoned.”

Out with the old

Having two main pumps out of service, and with the remaining spindle pumps requiring expensive repairs, Colchester Inlet Pumping Station was operating at inefficient inlet wet well levels. Anglian Water then turned to fluid handling specialists Panks and Xylem Water Solutions UK to conduct a full efficiency survey, with a view to improving operational output and reducing site call-outs and maintenance costs.

The results from the survey revealed that the old shaft driven pumps were highly inefficient in terms of the amount of power required to get the correct flow, and a full year energy capture of £68,000 was forecast if pumps five and six were replaced with Flygt 3000 series, N Pumps.

The total cost of the operation was estimated at £235,000. This meant the purchase and installation of the pumps from Flygt, a Xylem brand, could be entirely funded by the energy capture, giving a payback period of approximately 3.45 years. With the results of the efficiency survey meeting the criteria set out by the energy team at Anglian Water, Panks was instructed to proceed with the installation of the two Flygt pumps from Xylem.

Surpassed expectations

The initial efficiency survey evaluated the energy capture levels and after three months the results were higher than anticipated. The actual energy saving has now been confirmed as £77,000 per annum, which equates to a massive saving of 777,850 kW hours over a full twelve months, reducing the payback period to 3.04 years.

The new Flygt N-pumps now take all dry weather flow, operating on duty/assist, with the second pump only being used after heavy rainfall. The pumps run on average eleven and a half hours each per day and are configured on auto rotate after three hours.

The four remaining vertical spindle pumps are each programmed to run briefly once per day as a precautionary measure, only to keep them operational.

Paul Fookes concludes: “The installation of two Flygt NT-3400 140kW pumps has made a big difference to the way the flows are managed coming into Colchester Sewage Treatment Works, significantly improving both operational output and asset reliability.”

“Working closely as a team with Anglian Water and Panks allows us to design pumping systems to maximise our customer’s energy and operational savings.”




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