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Process Equipment Update


process were reaching the end of their natural life, they had performed well so it was decided to continue with this type of pump,” explains Black & Veatch’s project M&E co-ordinator at the Walton site. Watson-Marlow 620 series close-coupled pumps are


pumping inorganic polymer coagulants such as ferric sulphate, which perform well with thick flocs and offers fast sedimentation. The water is then treated using CoCoDAFF and passes


through post-ozone and granular activated carbon (GAC) contactors, as well as slow sand filters before arriving at the disinfection stage, where sodium hypochlorite is introduced to contact tanks in doses using 520 series Watson-Marlow pumps.


Sodium hypochlorite is a highly corrosive chemical that


has disinfection and bleaching properties. It is used in the purification of wastewater and the disinfection of drinking water. However, dealing with the chemical can be difficult as


it is toxic and emits chlorine when in contact with acids. It naturally releases tiny bubbles of gas, which have a tendency to collect on the small ball valves found in conventional diaphragm dosing pumps. This can cause gas locks in the system, which prevent the pumps from functioning. Because peristaltic pumps retain the fluid completely within the tube and have no valves that can leak or corrode, they can be used for the accurate metering of substances as challenging as sodium hypochlorite, without the associated gas locking and maintenance problems. Peristaltic technology therefore helps to keep costly


downtime at the site to a minimum. It’s a similar story with Verder GPM, the US partner of


Verderflex peristaltic pumps, which has used its expertise to overcome persistent problems at a North Carolina water and wastewater treatment plant. Often overlooked, the reliable peristaltic pump has again


proved its worth at Coddle Creek water treatment plant, eliminating the mixed results of a few years previously experienced using a submersible pump dosing powder activated carbon (PAC) from a wet well. After more than three submersible pumps failed in just over a year the maintenance and operations management sought an alternative.


The problem was the location of the pump: in the pump room eight metres above the bottom of the well and additionally, the pump must also be able to resist the PAC’s abrasive nature. So the plant called on Verder GPM to help find a solution. Lance LeBrun, Verder GPM’s regional sales manager for


the Carolinas, recognised that the best pump for the job would be a Verderflex peristaltic pump. Using a flow paced controller, the Verderflex hose pump can transfer and dose variable flows in accordance with the plant’s demand and by their very nature these pumps can gently pump abrasive suspensions such as PAC and lime slurries without any check valves.


Suction lift


Given the flow rate, suction and discharge pressures needed, Verder GPM chose the Verderflex VF15 hose pump with its 15mm diameter natural rubber hose. The VF15 is capable of short term flow rates up to 600l/h and continuous flows of 375l/h at pressures up to 12Bar. Use of the high pressure rotor and Verderflex’s reinforced hose technology creates excellent suction lift and easily manages the eight metre lift needed by Coddle Creek. Verderflex manufactures a large range of peristaltic pumps


for many process applications, from small custom tube pumps used in OEM equipment through to the VF125, the largest high pressure peristaltic hose pump in the world and Scada- controlled Smart tube pumps that accurately and consistently dosing process chemicals. The company says that during difficult economic times


customers are increasingly looking for reliable, low cost of ownership engineered solutions over cheaper but high maintenance alternatives and recent studies indicate that more and more customers will be using peristaltic technology in the future.


Small and ruggged


Meanwhile Eccentric Pumps has launched its new MiniPump small peristaltic pump. The company says that its latest addition delivers the same performance advantages as the rest of the peristaltic pump product line. With a 6mm, 1mm or 13mm ID hose, the MiniPump is a small and efficient peristaltic pump that covers a pumping range from 1-120 gallons/hr.. l


Multi-channel peristaltic pumps A


ccuStaltic multi-channel peristaltic pumps from Ledebuhr Industries are reliable pumps that simply squeeze the liquid out of a flexible tube, with precision rollers, in a continuous or cyclic rotary motion The fluid only contacts the inside of


the resilient tubing. AccuStaltic pumps are specifically designed to use multiple tubes simultaneously. The pumps range from 4-12 individual flow


channels which can be combined with different manifolds and tubing to create flows from single continuous flows up to 180l/min to 12 accurately


12 www.engineerlive.com


metered individual flows of as little as 0.5ml/ cycle. In terms of accuracy, AccuStaltic pumps work at ± 5 per cent of average flow over their speed range and the life of the tube for most tubes. The design keeps older, swollen tubes from pinching and rubbing, for longer tube life. Double-sealed, synthetic-lubed bearings are impervious to contamination. All parts are stainless steel or coated to resist all but the strongest alkali solutions.


Serviceability is simplified with four bolts or fewer needed to remove any component – and


all parts are available individually off-the-shelf. In addition, hoses can be inspected without a total pump disassembly, making for easy routine maintenance. The pumps are also readily rebuildable, at the fraction of a cost of a new pump, often within an hour. Ledebuhr has included a wide range of turnkey drive options, for example fixed speed, a sensorless variable-speed AC, hydraulic, and mechanical link. The company says the new pumps can handle pressures over 70psi, with the proper tubes, with minimal effect on flow rate. l


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