South Staffs Water Pump Efficiency Programme (2022)

Large boosters consuming <£500k energy per annum - Courtesy of Integrated Water Services (IWS) M&E Ltd

Minimising energy consumption and CO2 emissions are at heart of all modern water companies and the 2030 net zero carbon emission target can only be achieved if real and direct effort is dedicated to this. The pump efficiency programme described within this article is a major part of the energy efficiency strategy undertaken by South Staffs Water; the water supply company serving circa 1.6 million customers in Staffordshire, the West Midlands, Cambridge and the surrounding area. Once a year, a number of pumpsets are selected for detailed performance surveys. Units are tested in 1 to 5 years intervals with the largest units analysed annually whilst the smallest rated machines, 30-50kW, are on a 5-year testing cycle.

Undertakings

Integrated Water Services (IWS) M&E Ltd was contracted by South Staffs Water to undertake pump performance testing, system testing thermography and vibration analysis throughout the south Staffordshire region as part of their Pump Efficiency Programme (PEP).

Pump Efficiency Programme: Supply chain – key participants

• Client: South Staffs Water
• Main contractor: Integrated Water Services M&E Ltd
• High efficiency pumpsets: Wilo UK Ltd
• Drive selection & installation: Sentridge Control
• Drive manufacturer: ABB
• Bearings: Access Engineering Supplies
• Mechanical seals: Eagle Burgmann
• Efficiency coatings: Belzona Polymerics

Understanding ‘normal’ operations

Following the on-site testing, IWS obtained flow data to enable in-depth analysis to formulate a complete understanding of a site’s normal operational regime. This process required the compilation of accurate cost analysis detailing current energy consumption and an evaluation of CO2 emissions. This allowed IWS to report to South Staffs Water to better target capital investment.

IWS undertook pump performance testing to determine the best solution; be it refurbishment of existing infrastructure, replacement for new highly efficient infrastructure or by optimising the current site operational regime. The adoption of the testing within this programme led to an increase in resilience, reliability and a reduction of greenhouse gas emissions for South Staffs Water and helped improve the efficiency and asset life of the pumps.

This programme focused on five key sites which were targeted as those expected to yield the greatest energy savings potential. Details regarding each of these sites and the solutions adopted are discussed in this case study.

Cookley Borehole – Energy efficiency replacements

Pump performance testing undertaken by IWS on the borehole pumps indicated that all three pumps were displaying poor performance. When operating at the required duty point for the site, all three units were operating to the right of their best efficiency points (BEP) indicating that they were incorrectly sized for their application.

Due to the findings, IWS sourced a suitable replacement option to return the greatest operational efficiency, including permanent magnet motors (PMM) to significantly increase the drive efficiency by circa 10% when compared to a standard submersible motor.

IWS contacted numerous suppliers and it was determined that new units complete with permanent magnet motors from Wilo UK Ltd were the optimal solution for the application. The selected units operate at their respective BEPs at the required duty, indicating they are a good match for the system.

Cookley Boreholes performance tests – Courtesy of Integrated Water Services (M&E)

At the time of writing (April 2022) the new pumpsets have been successfully installed. Once undertaken, post installation testing will validate the actual energy savings achieved via this scheme, which are estimated at £27,500 per annum.

Seedy Mill WTW, Ashwood and Hinksford Pumping Stations

• Seedy Mill Low Lift Pumps – Energy Efficiency Refurbishment: IWS undertook pump performance testing on the two low lift pumps. This testing indicated Pump 3 had decayed in performance by 3-4% when compared with the previously recorded performance in 2014; increasing the OPEX of the system by £6,400 per annum when compared with the expected post-refurbishment performance.
• Ashwood Booster PS – Energy Efficiency Refurbishment: Pump performance testing on the four booster pumps indicated that Pump 3 had decayed in performance by 4-5% when compared with the previously recorded performance in both 2013 and 2016. This performance loss was increasing the system’s OPEX by £5,100 per annum when compared with the expected post-refurbishment performance.
• Hinksford Booster PS – Energy Efficiency Refurbishment: Pump performance testing on the two booster pumps indicated that Pump 2 had decayed significantly in performance when compared with the manufacturers published performance specifications as well as the previously recorded performance in 2016. The 6-10% loss of performance was increasing the OPEX of the system by £5,100 per annum.

(left) Seedy Mill low lift pumps performance tests and (right) Hinksford pump performance tests – Courtesy of Integrated Water Services (M&E)

Due to these findings, South Staffs Water and IWS opted to refurbish the under-performing units to reduce the system’s OPEX. After refurbishment, Belzona Polymerics efficiency coatings were applied to further increase the hydraulic performance of the units; reducing the post-refurbishment operational costs at each site.

Yoxall PS – Priming pump variable speed drive installation

Pump performance testing on the two booster pumps and two priming pumps installed at Yoxhall Pumping Station indicated that the installation of variable speed drives (VSD) on the current priming pumps would reduce the hydraulic head to which they operate; leading to a reduction of the OPEX associated with this system.

This hydraulic head reduction on the priming pumps would mean that boosters were needed to deliver the additional head; ensuring the local delivery zone remained sufficiently pressurised. Despite this, the installation of variable speed drives to the priming pumps was estimated to reduce the OPEX associated with this system by circa £1,600 per annum.

Yoxhall priming pump performance tests – Courtesy of Integrated Water Services (M&E)

Summary of savings

South Staffs Water’s Pump Efficiency Programme at Cookley PS, Ashwood PS, Hinksford PS, Seedy Mill WTW and Yoxall PS resulted in significant energy efficiency savings of approx. £46,000 per annum against an implementation cost of approx. £121,000, providing a payback period of just 2.64 years.