Peristaltic pump perfects pasty patina

Having suffered repeated failures using conventional impeller pumps for the transfer of liquid egg in glazing processes operated at Cornish food manufacturer Rowe’s the bakers, the company turned to peristaltic pump technology from Watson-Marlow Pumps Group.

Originating in 1949 as a bakery in Falmouth, Cornwall, Rowe’s today comprises two production sites (both in excess of 1850 m²), 17 retail outlets and more than 400 employees. As well as selling products such as pasties, savouries, sandwiches, cakes, breads, rolls and confectionery through its own stores, the company also supplies on a wholesale basis to virtually all the UK’s leading supermarkets.

Maintaining such a vibrant manufacturing enterprise presents a real challenge to engineers such as Phil Thomson, who is part of a team that helps ensure production is both continuous and efficient.

One particular recent problem on the pasty production line was causing the maintenance team more than a few headaches. Here, egg mix is pumped into a glazing unit that is effectively a container with two integral spinners. The spinners create a mist that is allowed to fall and form a glaze on pasties passing below on a conveyor. Until recently, the company was using a conventional impeller pump for the task, but repeated failures and downtime became a growing cause for concern.

“The problem with an impeller pump is that it lacks a non-return valve, so if the process stops then the pump needs to be re-primed,” explains Thomson.

“Furthermore, because egg congeals, dedicated cleaning of both the pump and its connections is required. The escalating downtime meant ultimately that we had to find an alternative.”

Fortunately, Rowe’s already had chemical dosing pumps from Watson-Marlow on site and so Thomson was aware of the capabilities of peristaltic technology.

“I called Watson-Marlow and they explained what pumps would be suited to the application, finally recommending a 520 series process pump that they kindly supplied on loan for trial purposes.”

Described as the world’s fastest growing pump type, peristaltic pumps have no valves, seals or glands and the fluid contacts only the bore of the hose or tube, eliminating the risk of the pump contaminating the fluid or the fluid contaminating the pump.

Importantly for Rowe’s, Watson-Marlow pumps enable users to clean inline at full velocity, without the intrusion of the bypass required by most other positive displacement pumps. The pump self-drains, has low-shear action and straight-through flow and the tube is fully swept for superior hygienic performance.

After a two-week trial at the company’s production facility in Falmouth, Rowe’s duly acquired the Watson-Marlow 520 series pump.

“While impeller pumps are cheaper, we could easily burn out four a year on a single production line,” says Thomson. “If you add in the downtime and labour costs, peristaltic technology makes far more economic sense.”

As a further benefit, the peristaltic pump has also reduced the amount of foam caused previously by air entrapment in the impeller pump. Foam is classified as product waste and was being created at a rate of around 1 litre an hour.

“We couldn’t be more pleased with the peristaltic pump,” states Thomson.

“Considering all the costs we incurred with our impellor pumps, I estimate that we will achieve payback on our investment within 12 months. In fact, we have just ordered a second pump for another glazing unit and hope to replace them all over the course of the coming two years.”