Peristaltic pumps increase accuracy and reliability


In modern paper and cardboard production, there are endless dosing tasks, for which precision and high reliability are especially critical. Mindful of these factors, European carton maker Moritz J Weig GmbH is increasingly turning to Qdos peristaltic pumps from Watson-Marlow Fluid Technology Group (WMFTG), as MEPCA found out.

Moritz J Weig, a supplier of folding boxboard and plasterboard made from recovered paper, runs two carton machines at its head office in Mayen, Germany, with a total capacity of 630,000 tonnes per year.

Precision and reliability

For modern and efficient paper production, dosing of various chemicals such as paper additives or processing aids is unavoidable. On both of Weig’s carton machines, many pumping tasks take place, which the company relies on different pump types to achieve. However, for challenging dosing tasks that demand precision and reliability, Weig is increasingly shifting its focus to Qdos peristaltic pumps from WMFTG.

The first field test for a Qdos pump at Weig was in the wet section on ‘KM3’, a machine for folding boxboard. During sheet formation for the surface layer, a chemical antifoam agent is dosed into the running water. Until recently, solenoid diaphragm pumps were used, but they were unable to guarantee the necessary long-term accuracy.

“The diaphragm pumps performed dosing tasks with a strongly pulsating flow,” reports Peter Molitor who, as Project Engineer, is responsible for material and water treatment on both carton machines in Weig. “We use a flow meter to control the dosage. However, due to high pulsation, recording the dosage was difficult and unreliable.”

When the dosing is not exact, there can be a negative impact on product quality, sometimes even leading to rejected stock. High maintenance and repair requirements of the diaphragm pumps proved to be troublesome in the production process, and their design means they need a ball valve on both the inlet and discharge side.

“These valves tended to clog, while torn membranes caused further problems,” continued Molitor. “Replacing a membrane is very laborious and therefore expensive, so in many cases, we just replaced the entire pump to minimise interruption to production.”

When the company began searching for alternatives, it found what it was looking for with the Qdos dosing pump from WMFTG.

Innovative design

Qdos pumps do not have any membranes, valves or seals. Moreover, they use a particularly innovative design principle: the only wear part is the patented ReNu pumphead, which can be rapidly replaced without tools. As the pumphead is completely sealed, leakage of fluid is prevented, so the operator does not come into contact with chemicals.

Weig opted for the Qdos 60 model, which doses at up to 1,000 ml/min with an accuracy of ±1%. Trials with the Qdos peristaltic pump were very successful from the outset, explained Molitor: “Thanks to lower pulsation, recording the dosage in the flow meter is now trouble-free. Strictly speaking, the pump is so accurate that in theory, we will be able to dispense with the use of an additional flow meter in future.”

And with regard to maintenance, the Qdos pump delivered on its promise, as Molitor confirmed: “We have been dosing antifoam for about a year now. Despite 24/7 operation, it is still on its first pumphead.”

Six more pumps

After this experience, it made sense to use Qdos in other applications on the KM3 machine. Since autumn 2017, a total of six have been dosing retention agent.

“The use of Qdos pumps has prevented precious fibres, fines and fillers being flushed away,” added Molitor. “The pumps each supply around 33 to 38 litres/hour of the slightly viscous retention agent to different dosing points in the dilution water line, with a counter-pressure of about 5 bar.”


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