Water & Wastewater Treatment

PUMP CENTRE CONFERENCE & EXHIBITION 2015 PREVIEW 17 allow a faster and more efficient pump start up procedure, while also making monitoring easier. In the existing system, operators had to go to the site and work for three to four hours to start up a pump, making the operation time-consuming and costly. The final requirement was providing dual electrical power supply from the National Grid and up to 1.5MW of power supply from a photovoltaic (PV) system located in an adjacent field. Solution To address these requirements, the Boulting Group completed a holistic, objective site testing and evaluation process of the entire system, including Front End Engineering and Design (FEED). This resulted in a set of recommendations, including the upgrade of assets like switchgear, motors, drives and control systems. Although the Boulting Group report had no further contractual obligations attached and Thames Water was free to commission a different contractor to implement any improvements, the deep-rooted collaboration with Pump Management and previous successful projects prompted the water giant to assign the engineering, design, procurement and implementation contracts to the Boulting Group. Hydraulic redesign of impellers The original impellers were limited in efficiency to around 80 per cent. To improve the hydraulic performance and the priming process, Boulting Pump Management suggested a pump upgrade, including a complete redesign and manufacture of the pump impellers to help improve the net positive suction head (NPSH) characteristic and pump efficiency. The specific design Boulting created for this project allows an improvement to 87 per cent pump efficiency and increased reliability during start up and operation. Another benefit of the new design was the minimisation of cavitation and its damaging effects on the pump components. Improved priming process Poor priming also made the old system difficult to manage, time-consuming and expensive. To resolve the issue, the Boulting Group suggested the installa- tion of a new and automated priming system that uses motive air vacuum ejectors and continuous water level monitoring. To further increase priming reliabil- ity, the Boulting Group replaced the old packed glands with mechanical seals. This reduced leakage to virtually zero, making the system more reliable and adding an extra two per cent to overall system efficiency. Increased energy efficiency The pump upgrade and refurbishing also meant an improvement in overall energy efficiency. In the new installa- tion, the pumps, motors, drives and channel level will be automatically controlled to optimise the Specific Energy Consumption (SEC) of the system. Each component will be controlled individually and automated using Boulting PSOp (Pump System Optimisation), installed within SCADA managed Programmable Logic Control- lers (PLCs). In addition, the remote control feature of the Boulting PSOp so—ware meant even further cost savings for the Littleton system. In the past, operators had to go on site and manually start the pumps; the new system reduces pump start up time by up to 96 per cent. Dual power supply Another interesting feature of this project was the need to integrate dual power supply from the National Grid as well as a separate solar power photovoltaic system. Relying on its expertise as an established solutions provider, the Boulting Group installed a High Voltage Switchboard that enables the pump station to use PV power when available and supplement it with grid power when necessary. Aesthetic considerations were at the forefront for the project team throughout. The unique character of the Littleton pump station comes from the beautifully designed pump room, created in the mid-1920s. To preserve the personality and historical character of the space, the Boulting Group suggested changing the layout of the system. This meant removing some equipment installed in the 1950s and several add-on pieces such as air ducts, as well as installing modern inverters, panels, transformers and control system in an adjacent room. The original pumps are connected to new high performance motors and gearboxes, close to the oldest static steam driven pump, which will be kept as a museum piece. Conclusion Thames Water originally estimated the upgrade would take at least two years, but by working closely with the Boulting Group, the project is expected to take only half that time, including the design, delivery and installation of the new system. The Littleton RWPS project is expected to be completed and fully operational by June 2015.

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