Some basic peristaltic-pump parameters explicated
Peristaltic hose pumps prove their worth in lime dosing and other critical applications
By Tom O’Donnell
The world’s major industries would come to a screeching halt without enough water. It’s an ingredient in many finished products and a by-product of many processes. Water is also an industrial-equipment cleaning or cooling agent. Water often becomes wastewater, which must either be treated or disposed of. With increasing environmental responsibility, proper wastewater handling and treatment is a big deal.
Wherever there is water there are pumps. There is demand today for pumping technology that delivers efficient, reliable and safe handling of water, from its pristine state to the soiled variety that flows into a water-treatment facility. In fact, wastewater presents special challenges for pumping technology. Pumps can be fouled with abrasives or solids. Hazardous materials must be contained to protect plant personnel and the environment.
It is this author’s contention that positive-displacement peristaltic pumps, i.e., hose pumps, are more than up to the challenge inherent in the handling and treatment of water and wastewater in a wide variety of municipal and industrial applications.
Proving the contention
Design and operational characteristics of the peristaltic hose pump, first patented in 1925 in France, make it a wise choice for water-handling applications — whether moving viscous or abrasive slurries or transferring water-thin, non-lubricating fluids or shear-sensitive materials. Peristaltic hose pumps are ideal for the full array of diverse operations within the water-and-wastewater industry.
The smooth-wall, flexible hose fitted in the peristaltic pump casing is squeezed between the rotor shoes and the inside of the pump casing. The alternating contraction and relaxation of the peristaltic pump hose forces the contents through the pump and into the discharge piping, with a pump’s rotating action delivering a constant displacement rate.
Hose restitution, following the squeeze, produces an “almost-full” vacuum that draws product into the hose from the intake piping. The pump casing is lubricated to cool the pump and lengthen shoe and hose service life. Since product contacts only the hose and not internal pump components, the technology is suitable for abrasive and corrosive applications.
The pump’s volumetric consistency is excellent for the strict dosing and 24/7 operating cycles found in wastewater treatment. A seal-free design makes it dry-run, self-priming and low-slip capable, and eliminates any potential leak or contamination points — while simultaneously providing superior suction lift. Finally, peristaltic hose pumps are easy to operate and maintain. Pumping direction can be reversed.
Know your hose
The peristaltic pump hose — which, because of its seal-less design, is the only component to actually come in contact with the pumped medium — needs the highest level of material compatibility, while reliably delivering the millions of pumping cycles that will be required during its service life.
Another hose-material consideration is “fatigue resistance” to hose failure as it is run through its millions of pumping cycles. A hose material susceptible to developing cracks and holes relatively early is not as desirable as one meeting the demands of repeated contraction and relaxation, especially when particulate-laden liquids are being pumped. Reinforced construction of peristaltic hose and use of rubber compositions that withstand the stresses within the peristaltic hose allow for the optimum life cycle and performance.
Hoses may be typically available in three materials of construction, chosen because of their high levels of fatigue resistance:
· Natural rubber – highly resilient with excellent abrasion resistance and strength
· EPDM – high chemical resistance, especially when handling concentrated acids, and alcohols
· Buna-N – highly wear-resistant to natural gas containing products
Peristaltic hose pumps can be a reliable component in the optimization of water-and-wastewater operations.
Today’s pumps feature a seal-free design that eliminates leaks and product contamination, which enables them to handle the toughest water-and-wastewater pumping applications, from abrasive and aggressive fluids to shear-sensitive and viscous materials. The pumps, which can run in either forward or reverse, are self-priming and offer suction-lift capabilities to 9 meters (25.5 feet), as well as the ability to run dry continuously without adversely affecting the pump’s performance. Ductile-iron and steel construction lets the pump produce discharge pressures as high as16 bar (232 psi).
Pumps with flow rates ranging from 1.7 to 1,249 L/min (0.46 to 330 gpm) handle products with water-like viscosities and those as high as 70,000 cSt (352,000 SSU), solid particle sizes from 1.5 mm to 18 mm (0.06 inches to 0.71 inches) and soft particle sizes from 1.5 mm to 31 mm (0.06 inches to 1.22 inches).
Pumps can handle product temperatures ranging from 32 F to 158 F with models featuring an EPDM hose capable of handling maximum temperatures to 176 F. Optional equipment includes hose-failure detectors, vacuum kits and non-metallic (PPH and PVDF) inserts.
The water-and-wastewater universe is diverse, which means pumps used in water-and-wastewater operations must be nimble and versatile, to cope with fluids that vary in qualities related to viscosity, temperature, corrosiveness, toxicity, abrasiveness and particulate levels, to name a few. These attributes must be attended to while adhering to production quotas and environmental requirements. For more than 80 years, peristaltic hose pump technology has been a leading choice for water-and-wastewater handlers and treaters.
Tom O’Donnell is a Business Development Manager for Abaque® Series pumps. He can be reached at Tom.ODonnell@neptune1.com.
Abaque Series pumps are a leading brand of peristaltic (hose) pumps from Dover Corporation’s Pump Solutions Group (PSG®) and manufactured in PSG’s Neptune facility in North Wales, Pa.
Headquartered in Oakbrook Terrace, Ill., PSG is comprised of several leading pump brands, including Abaque®, Almatec®, Blackmer®, Ebsray, Finder, Griswold™, Maag, Mouvex®, Neptune™, Quattroflow™ and Wilden®. You can find more information at www.psgdover.com.