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Peristaltic pumping tackles tricky processing problems

1st February 2013


Page 1 of 3

Peristaltic pumping offers a host of advantages over conventional pumping techniques, especially when coupled with the latest control technology. Sean Ottewell reports.

Compared with lobe pumps, diaphragm pumps, gear pumps and piston pumps, and every other type of pump, the advantages of peristaltic pumps are many, including no contamination of the fluid being pumped, no contamination of the pump itself, ideal for shear-sensitive and aggressive fluids, dry-running, no valves/glands/seals, and reversibility.

One of the latest companies to avail of these benefits is London, UK-based Wine Innovations, the inventor, founder and pioneer of 'the tulip' pre-filled wine goblet. The company is now using industrial peristaltic filling machines from Flexicon Liquid Filling, part of the Watson-Marlow Pumps Group, on its latest filling lines.

Having originally used volumetric filling equipment, the company is enjoying a vast array of benefits from its switch to Flexicon technology.

The tulip itself is a pre-filled and sealed shatter-proof plastic wine goblet (187ml) for outdoor events such as concerts, festivals, sporting events, parties and fairs. Its advantages include rapid serve time, no spillage or waste, safer than glass and full recyclability.

Growing take-up

Now the company is finding additional success as a convenient solution for airlines, ferries, hotel mini bars and railways. With its one-year shelf life, there is also growing take-up from retail outlets.

The original volumetric filling machine was accurate and quick, but came with a lot of complex parts such as stainless steel pipes, pistons, three-way valves and air diaphragms. These all cause certain issues when it comes to cleaning, for example creating opportunities for yeast, bacteria and mould to thrive.

The regular and long-winded cleaning regime this required, including hot water and steam, proved unacceptable from a productivity point of view.

So after working with Watson-Marlow, Wine Innovations decided to acquire Flexicon PD22I industrial peristaltic machines in combination with Flexicon MC12P OEM control units.

The Flexicon PD22I is a table-top unit that requires no cleaning validation. It also facilitates easy and rapid product change-over (less than 60 seconds) and provides no potential for cross-contamination, hence providing the perfect solution to the problems faced by Wine Innovations.

Ease of installation

There are other benefits, too, including ease of installation, the equipment's accuracy (+/-0.5 per cent) and speed, its adjustable acceleration and deceleration capability, plus the ability to adjust other parameters at the simple touch of a button.

Importantly the company is also achieving a much better dissolved oxygen result than before. Oxygen is the 'enemy' of wine, and volumetric fillers can occasionally churn the product, creating bubbles, which in turn leads to rejects.

Watson Marlow Pumps has also had success at Thames Water's advanced water treatment works (AWTW) in Walton, Surrey, where engineering, consulting and construction company Black & Veatch opted to install a number of 520 series and 620 series peristaltic models.

Quick release functionality

Offering continuous, high-pressure and quick release functionality, the new pumps have slotted comfortably into their high-tech surroundings at Walton, which is one of Thames Water's flagship process plants.

Several processes reliant on pumping operations are vital to the advanced water treatment process at Walton. For instance, pre-ozonated water is mixed with a coagulant in the flocculators to aid the production of large flocs, which are floated more easily in the subsequent CoCoDAFF (counter-current dissolved air flotation and filtration) process. The addition of coagulant is today facilitated by newly installed 620 series pumps from Watson-Marlow.

Historically this site has had close association with peristaltic pumping technology.

"While the previous 504 series pumps for the coagulant 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.

Eccentric says that its customers have used its small, rugged peristaltic pumps to solve problems such as handling bleach, acids and alkali, abrasive or corrosive slurries, or other difficult-to-pump fluids and materials.

"Our customers appreciate our self-priming, positive flow, high suction lift, dry running, and sealless peristaltic pump design," it says.

The company also offers replacement hoses for competitors' pumps, including Watson Marlow, Bredel, Periflo, Verder, Verderflex and Blackmer.


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