Aggressive fluids meet their match with peristaltic pumps

Paul Boughton

If your pumping application involves aggressive fluids, but at the same time costs have to be cut and production expanded, then peristaltic pumps offer an economical solution. Sean Ottewell reports.

AHC Benelux, a specialist in the provision of surface treatment technologies for engineering applications, has installed a series 521F/RC close-coupled peristaltic pump from Watson-Marlow Pumps to help process aggressive wastewater fluids produced by various plating and galvanising processes at its sit

In Eindhoven, eight flexible production lines run 24 hours a day, with processes such as electroplating silver, gold, copper and tin, electro-less nickel and synergetic coating, taking centre stage. AHC in Venlo has large, fully-automated lines and focuses primarily on technical and hard anodising, synergetic coatings, electro-less nickel on steel, as well as specific treatments such as chromic acid anodising, chromating and lacquering. AHC's customers come from a range of sectors: everything from automotive, electronics and aerospace, through to pharmaceutical and food and beverage.

"Running these continuous coating operations produces wastewater that needs to be treated before disposal in accordance with environmental regulations," explains Luc Heldens, supervisor chemicals at AHC Benelux. "Both sites are certified to ISO14001 and we take great pride in our green credentials. To prepare process wastewater for disposal, both hydrochloric acid and caustic soda are used to ensure pH is maintained at regulatory levels."

Originally, an air-operated diaphragm pump (AOD) was considered for the task, but as wastewater from production contains around 33 per cent acid chloride, solids in the acid would destroy the pump's membrane. The AOD would also be unable to ensure accurate dosing of both hydrochloric acid and caustic soda - and this would cause unwanted fluctuations in the pH levels.

The company initially worked with a competitor supplier of peristaltic pumps but switched to Watson-Marlow because of problems with long delivery times. The first Watson-Marlow baseplate pump was installed many years ago. Now, having reached the end of its natural life after many years' reliable service, AHC had no hesitation in returning to Watson-Marlow to order another, this time in the form of a series 521F/REC close coupled pump, specifically designed for demanding industrial applications.

Featuring high performance engineered plastics and a stainless steel pumphead, easy set-up and maintenance are critical features of this innovative peristaltic pump, which is particularly suited to aggressive fluids. Its high resistance to chemical attack makes it rugged enough for the harshest environments, delivering cost-effective, precise pumping and a long service life (Fig.1).

In peristaltic technology, nothing but the hose or tube touches the fluid, eliminating the risk of the pump contaminating the fluid, or the fluid contaminating the pump. Fluids are drawn into the tube, trapped between two rollers, and expelled - the complete closure of the tube gives the pump its positive displacement action, preventing backflow and eliminating the need for check-valves.

"We installed the 521F/REC pump fitted with Marprene thermoplastic tubing elements in February 2010 and it has since performed extremely well," says Heldens. "It's pumping hydrochloric acid for about an hour a day - and caustic for around 15hours a day. The pump is linked integrally to our pH controller and I have to say we've had no issues whatsoever with reliability, it simply runs as required without any need for intervention, it ensures a high level of chemical resistance, is easy to operate and needs very little maintenance."

Cost savings

Meanwhile supplier of pumps and accessories Verder Pumps South Africa (VPSA) says that the use of the VF125 pump range contributes to cost savings and increased productivity at platinum mines. This was seen at a precious-metal producer's concentrator upgrade project, near Rustenburg, where VPSA was required to upgrade the thickener transfer pumps for higher production capacity, says VPSA consultant Daan Louw. The upgrade was possible as the pumps are able to pump slurry with 1.7 specific gravity and at a flow rate of 60m3/h over a distance of 690m, with a height of 30m.

The VF125 thickener pumps resulted in cost savings and increased production capacity.

Process engineering company DRA was appointed project engineer on the project and approached VPSA to assist in the design of six thickener transfer pumps. "No other pump on the market is able to transfer the slurry without a second pump station, which would come at a significant cost to the mine and would probably take more time to process," says DRA project engineer Thys de Beer.

There are currently 24 VF125 pumps operating at 37kWh at the platinum processing plant. The design for these pumps included installing pulsation dampeners to help decrease the pressure build-up in the pipeline. Build-up in the hoses is eliminated by using rubber Verderflex hoses that are designed to increase life expectancy and production performance. These are designed to handle tough operating conditions; they reduce downtime, decrease maintenance costs and provide easy operation and reliable solutions in difficult pumping environments.

Sludge solution

Blackmer's Abaque series of peristaltic pumps is said by the company to be the technology of choice when it comes to viscous and/or abrasive sludges, water-thin, non-lubricating fluids, corrosive chemicals, or sheer-sensitive materials. Because of the novel technology used, typical applications span many process applications, including wastewater, chemical processing and food manufacturing.

The pumps are available in nine different sizes that provide flow rates of.15-48,000l/h. Being constructed of natural rubber, Buna, or ethylene propylene diene monomer (EPDM) within the pump's casing, they provide high levels of volumetric accuracy for sampling, transfer, and metering applications. A seal-less design eliminates leaks, contamination and wear problems associated with difficult to seal products, while they are self priming to nine metres.

In market news, Pulsafeeder has announced the acquisition of PeriFlo, a provider of peristaltic pumps for the industrial and municipal water and wastewater markets. PeriFlo offers a complete family of peristaltic hose pumps for a wide variety of applications.

PeriFlo's pump designs have been accepted by both the international community and the US market since their introduction into those markets in the mid-1990s.

Peristaltic pump technology is currently the fastest growing technology in the positive displacement pump market; growing at almost twice the rate of the next closest technology, says the company.

Meanwhile, Salem-Republic Rubbernow offers replacement hose for all manufacturers of peristaltic hose pumps. Custom manufacture allows control over all properties of the hose, the interior core (tube), carcass (exterior shell) and supporting wall thickness. Because of this, Salem-Republic offers peristaltic pump hose completely customised to accommodate specific requirements for individual applications. Tube linings are available in the following material choices: natural rubber, EPDM, nitrile (Buna-N), or FDA safe white and tan gum.

Peristaltic pump hose life is affected by three areas: the pump conditions, quality of the hose and the material moving through the hose. The company's 'no-crush' poly carcass is constructed using multiple plies of high tensile polyester cord. A smooth, precision ground concentric cover insures optimum performance and in-service life in the most demanding applications including pumping adhesives, starch, chemicals, pulp/papermaking slurries, lubricants, and food oils, waste and water treatment.