Pumps deliver high-viscosity fluids with high accuracy

MW Polymers, a leading manufacturer of gas leakage repair systems, is using Watson-Marlow Bredel peristaltic pumps to help achieve fast turnaround repairs based on the successful delivery of its revolutionary two-part polymer Ecoseal system. The peristaltic pumps not only cut filling and handling time in half, but they also improve delivery accuracy and help simplify the dispensing process.

There are 12million joints connecting the gas distribution pipes beneath Britain's road network and MW Polymers has developed a niche yet robust market by providing a repair service for these joint. Although established over 30 years ago, MW Polymer's recent Ecoseal innovation is said to have pushed the company to the forefront of the industry.

Michael Wild, MW Polymer's managing director, explains: "Today there is huge pressure on contractors to minimise the size of the road excavations required to undertake repairs. With this in mind, 'keyhole' repair methodology has been developed over the past five years that entails a small hole being drilled down to the top of the main, through which Ecoseal can be used to provide a safe, permanent repair, saving huge amounts of money and time."

Benefits over piston pumps

However, MW Polymers found that sourcing a reliable, fast, accurate and economic method of pumping Ecoseal was easier said than done. Wild says: "In our experience, piston pumps struggle when it comes to high-viscosity products such as Ecoseal. Because we wanted to avoid contamination of the pumping mechanism, we opted for a peristaltic pump, albeit a small-capacity model."

Unfortunately for MW Polymers the pump was not quick enough at filling the twin-barrel cartridges that dispense the Ecoseal component parts. Furthermore, the pump could only dispense one product at a time, which meant double-handling. Desperate for a better pump, the company contacted Watson-Marlow Bredel.

Wild says: "The applications engineer from Watson-Marlow was very helpful. Firstly he suggested we increased the capacity of the peristaltic pump, suggesting the Watson-Marlow 620Di/RE model, which is a dedicated dispensing pump that uses a single-channel tube element pumphead. He also suggested we use two pumps to reduce our handling time."

The Watson-Marlow Bredel 620 series dispensing pumps are designed to deliver accurate, repeatable volumes with set dosing and interval times to suit the application. The pumps can deliver up to 1080 litres/hour at up to 4 bar pressure through a chemical-resistant tube element.

Pump operation

In Watson-Marlow Bredel peristaltic pumps, nothing but the tube touches the fluid, thereby eliminating the risk of the pump contaminating the fluid or the fluid contaminating the pump. Fluid is drawn into the pumphead and trapped between the rollers and the track. As the next roller moves forward, the pocket of fluid is expelled and more is drawn into the tube by the vacuum that is created. The complete closure of the tube gives the pump its positive displacement action, preventing backflow and eliminating the need for check-valves when the pump is not running. The pumps, which often run 24/7, can be used for slurries, viscous, shear-sensitive and aggressive fluids. They are easy to install, simple to operate and inexpensive to maintain, requiring only a disposable and quickly replaced tube. 620 LoadSure pumps use tube elements with industry-standard Cam and Groove fittings.

Wild comments: "The 620 series pumps have really hit the nail on the head. Not only have they cut filling time from 20 seconds to 10 seconds, we can dispense both products at the same time, cutting our handling time in half."

The pump application at MW Polymers is far from straightforward. Many pumps find it extremely difficult to pump two different materials (with different viscosities) into the same component at the same time. For instance, one product might take 9 seconds to fill, while the other could take 12 seconds.

Wild concludes: "The engineers at Watson-Marlow have been very helpful. Following their guidance and training, our operators are now able to judge accurately how the liquids will dispense, depending on the ambient temperatures at the time of repair. Dispensing accuracy is now better than one per cent."