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Peristaltic pumps solve difficult pumping problems

10th April 2013


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Many pumps struggle to pump abrasive and corrosive fluids, causing expensive and inconvenient equipment failures. Peristaltic pumping overcomes these problems.
 
Since adopting Bredel SPX50 hose pumps from Watson-Marlow Pumps Group in various parts of its process, the water treatment plant at Kembla Grange in Australia has saved significant costs associated with downtime and maintenance.
 
The pumps were selected for tough applications such as pumping abrasive lime slurry and corrosive chlorine solutions, which were causing expensive and inconvenient failures of existing pumps (Fig. 1).  
 
Located 50km south of Sydney, the water treatment and filtration plant at Kembla Grange is operated by Veolia Water. It produces 210 million litres/day of high quality drinking water across the Illawarra region on behalf of Sydney Water. Failures and downtime are simply not conducive to efficient operations, so having reliable equipment that can be maintained safely and quickly is vital.
 
“When you add up the ongoing hassles of other pumps types, it became evident that Bredel pumps were our preference,” says Pino Taglieri, the plant’s operations supervisor. “It’s the nature of the hose pump - it just pushes the lime aside with its shoe, they’re gutsy and get the job done.”
 
Hose pumps are well suited to water treatment processes as they move fluid by compressing a shoe on to a reinforced hose in a circular motion, pushing pockets of fluid downstream quickly and easily by positive displacement.
 
Originally two progressive cavity pumps had been specified and installed at Kembla Grange for dosing lime slurry, which is used to maintain and control pH in water. However, the abrasive nature of the substance wreaked havoc on the pump’s rotor and stators.
 
“It was hard to maintain the set-point flows and there were constant blockages,” states Taglieri. “Depending on the demand we’d go through rotors and stators every couple of months, which was a costly exercise. On top of the parts, it would take two guys two hours to fix, plus the hassle of cleaning the lines. A few years ago we replaced these with Bredel SPX50s and the hoses last over a year. The performance of the pump was far beyond our expectations and we had huge cost savings.”
 
The inherent design of Bredel hose pumps means there are no intrusions in the flow path, eliminating any risk of blockages. This makes them particularly adept at handling problematic fluids such as abrasive lime, chemicals or sludge with high solids content, for example.
 
It was a similar story in another part of the plant where two piston diaphragm pumps were originally specified and installed to pump a chlorine solution into a 750 mm main at 16 bar. Chlorine is a corrosive disinfectant, in effect bleach, making it a tough application.
 
“These pumps were a nightmare to maintain, the amount of time and effort involved as well as getting the parts. It would take up to a day and a half to get each pump up and running; from the set-up, the timing, and so on.”
 
Taglieri again turned to Bredel pumps for the solution. Bredel pumps are self-priming and dry-running, making them easy to start and stop. Relative to other pump types, Bredel hose pumps have one wearing part – the hose. In this instance, the two SPX50s installed at Kembla Grange were fitted with Hypalon hoses, which offer excellent chemical resistance.
 
“They last 3-4 months and take an hour to switch out - what a difference it has made,” adds Taglieri.


 
Detailed design
 
Verderflex, the producer of innovative, green peristaltic pumps has released the new Dura 45 in the first of a new generation of medium flow, industrial hose pumps.
 
The Verderflex development team responded to feedback from customers by identifying the crucial utility and critical features of their pumping systems, which they felt could be improved.
 
The company responded with the Dura 45, a pump developed through examining hundreds of customer processes and nearly two years of testing and refinement.
 
According to company, the results of these tests have shown a genuine class-leading fluid-handling performance, high quality design through meticulous attention to detail of every component and assembly, and a safer, more reliable pump that can be trusted in customers’ processes.
 
The Dura 45 is suitable for medium flow applications of up to 12m3/h in fluid handling applications including acids, alkalis, oily and fatty liquids, polymers and lime. The overall Dura family is suitable for all types of slurries, sludge, viscous liquids and many other traditional applications.
 
The Dura 45 pump is also suitable for special conditions where suction lift is required, where the pump needs to be truly self-priming or a compact footprint is required. Should a site’s floor space be restricted, a Verderflex Dura pump can be mounted in any orientation for the most efficient use of plant floor space.
 
The Dura range is also the first choice pump for chemical dosing systems at sewage treatment works and in major utility installations completed by contractors and the Verder UK Pumping Systems service team.
 
In terms of performance, Verderflex says the new pump has surpassed all expectations during testing to deliver best-in-class results compared to any other peristaltic pump brand. This includes increased flow rate, delivering 25 per cent more fluid per revolution than the nearest competitor’s equivalent model. This equates to 300 fewer revolutions needed to pump 2000 litres. The company also says that a Dura 45 can deliver higher flow rates flow rates than equivalent pumps for all pressures up to 16 bar.
 
The new design features extremely long-life build quality with an optimum number of reinforcement fibres, plus a textured outer for distribution of lubricant. In addition, precise wall-thickness throughout the length of the pump is assured by checks for consistency, finish, small cuts and imperfections.
 
Another design feature is the patented, innovative flange system for fast changing of hoses and containment of chemicals. This includes a quarter lock system for quick removal of flanges for hose changes. The two-piece liner flange uses polypropylene and polyvinylidene fluoride (PVDF) inserts for chemical options. Meanwhile, the PVDF/316 stainless flange outer gives far higher nozzle load rating than weak bracket designs.
 
Also new is the improved front casing with captive screws, fully supported rotor shoes to prevent cracking, a robust mounting frame for stability and resistance to corrosion, and a typically 16 per cent smaller footprint than similar peristaltic pumps.
 
Meanwhile, Ledebuhr industries’ AccuStaltic multi-channel peristaltic pumps are positive displacement pumps that accurately produce synchronised flows of any liquid with no valves, seals or pistons.
 
They 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 also 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 180 litres/minute to 12 accurately metered individual flows of as little as 0.5 ml per cycle.
 
AccuStaltic pumps are self-priming, non-cavitating, and can be run dry with no pump damage.
 
Other benefits include accuracy, a patented design that prevents tube swell in older tubes, double sealed bearings that avoid contamination, replacement parts available off-the-shelf, and ease of inspection because the pump does not have to be disassembled to do this.

 
Longer lasting hoses

Graco says that its peristaltic hose pumps are ideal for industrial metering and transfer. These positive displacement hose pumps rotate a full 360° and use a single roller to compress the low friction hose once per revolution so that hoses last longer and users have less maintenance and downtime.
 
The company’s peristaltic hose pumps are used at municipal and industrial sites - wherever fluids are metered, dosed, or transferred from one place to another. Graco’s customers solve novel and complicated problems such as handling bleach, corrosive and abrasive slurries, acids, alkali, colourants, inks and other difficult to pump solutions.
 
In terms of products on offer, the EP2 Series hose pump has a maximum flow rate of 2.1 gallons/minute (7.9 litres/minute) and is ideal for chemical metering applications. The EP3 Series hose pump comes with a maximum flow rate of 6.2 gallons/minute (23.6 litres/minute) and is aimed at chemical metering and sanitary applications.
 
Meanwhile the EP4 Series hose pump can cope with a maximum flow rate of 19.5 gallons/minute (73.8 litres/minute) - ideal for abrasive material transfer applications.
 
The design of the EP4 Series utilises a single oversized roller that compresses a low friction hose through a full 360° of rotation. This innovative design means longer hose life when pumping caustic, abrasive or sensitive materials for metering or transfer.
 
Other benefits cited by Graco for this type of pumping include: 50 per cent more flow per revolution than conventional designs; one hose compression per revolution to improve hose life; no moving parts in the fluid stream; inexpensive to maintain – no valves, seals or glands; pumps are reversible and can be used to empty lines or clear blockages; integral drive and motor can run as low as one rpm; compact design, ideal for tight spaces and flexible placement; ‘quick change’ one-piece hose clamp assembly; and quick replacement of hose and lube.


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