Long Term, Trouble-Free, Lime Slurry Pumping
Lime slurry, widely used in water treatment, is a problem for most pump designs due to a tendency to settle out rapidly once pumping stops. This is not the case however for six Watson-Marlow Bredel hose pumps on lime slurry dosing duties at Dwr Cymru Welsh Water's Cefni Water Treatment Works which have an excellent record of long term service. Hose life in excess of 8000 running hours is regularly achieved.
photo: Six Watson-Marlow Bredel hose pumps on lime slurry dosing duties at Dwr Cymru Welsh Water's Cefni Water Treatment Works have and excellent record of long term service.
When used on similar duties, conventional metallic pumps encountered difficulties with blockage and fluctuating flow rates, leading to high running costs and excessive downtime. In contrast, the Watson-Marlow Bredel pumps with their “straight through” flow path, unobstructed by valves, vanes, rotors or glands, and with only the hose in contact with the slurry, have been operating consistently for more than seven years with highly accurate flow rates, long hose life and only routine maintenance.
First pumps in 1993
The six pumps operate in pairs as duty and standby. Two SP40 (40mm bore hose) pumps were installed in 1993 to transfer freshly mixed slurry to dosing tanks. Maximum speed is 54 rev/min with inverter control turn down to provide flow rates from 430 to 4300 l/h.
Additional pumps were installed when the works was enlarged in 1994. An SP15 pump (with standby) doses 5% lime slurry into the water as part of the treatment process. Using inverters, flow is varied from 25 to 250 l/h based on a maximum speed of 49 rev/min.
An SP25 pump (with standby) handles a 2.5% lime mix on the same duty. Flow range is 82 to 825 l/h based on a maximum speed of 46 rev/min. All pumps operate with flooded suctions and discharge pressures up to 5 bar. Discharge lines vary in length with a maximum of approximately 200 metres.
Also on the site are two Watson-Marlow 504U/RL tube pumps. These were originally supplied in 1979 for use in a chlorination plant and are shortly to be re-installed for similar duties.
Situated in the centre of Anglesey, Cefni Water Treatment Works produces 180 l/s of treated water when working at maximum capacity. There are similar lime slurry dosing installations using Watson-Marlow Bredel pumps at a number of other Dwr Cymru Welsh Water Treatment Works, notably at Llyn Conwy and Llyn Alaw
Produced for outputs up to 80 m³/h and pressures up to 16 bar, Watson-Marlow Bredel pumps are extensively used in water and sewage treatment both for highly accurate dosing of additives – including easily damaged flocculants – and for pumping viscous, abrasive, high solids content sewage sludges.
For more information contact Mike Sullivan or Heather Beale, Watson-Marlow Bredel Pumps on Tel: 01326 370370 or Fax: 01326 376009 or visit us at www.watson-marlow.com
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