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Dosing: are you in control?

26 February 2018

Lesley Eaton argues that all dosing pumps are not the same. In this article she explains the benefits of the progressive cavity pump over other solutions. 

For continuous processing and in-line blending applications, when it is necessary to dispense a constant, accurate amount of product every time, dosing pumps are essential. However, not all dosing pumps are the same – while most positive displacement pumps are capable of dosing, progressive cavity (PC) pumps are becoming the dosing pump of choice for many food processors looking to improve performance.

When accurate control of dispensing ingredients or products is required dosing pumps are an obvious choice, particularly when it is essential that the ingredients or products being added are dispensed at a constant, proportionate rate to ensure even mixing and distribution to control ingredient costs and ensure consistency.

Many traditional dosing pump designs such as piston pumps, air diaphragm pumps and peristaltic pumps have a pulsating action. This pulsed flow means that once the pump has dispensed a product, there is a pause before it can dispense again. This results in a gap in the process and can cause uneven distribution of ingredients. Some of these pump designs also require check valves. If solid or viscous particles get caught behind the valves it can cause them to stick, blocking the pump and halting the process.

In contrast, PC pumps are virtually pulsation-free. They use a rotor/stator pumping action which delivers a continuous flow into the product stream, compared to the start/stop action of piston or other positive displacement pumps. PC dosing pumps from SEEPEX, for example, produce a stable flow rate with a linear accuracy of +/-1%.

A sticky situation
Another benefit of PC dosing pumps over the alternatives is their ability to handle highly viscous products, sticky materials and those that contain solid particles. Rather than just dispensing simple, free-flowing liquids such as sauces and flavourings, PC pumps can dose sauces containing herbs and spices, ice cream with hard biscuit inclusions, and even abrasive pastes directly onto biscuit dough sheets. The action of PC pumps is also low-shear, meaning they can dose traditionally difficult-to-pump solid, semi-solid or shear-sensitive materials without damaging them. A variety of different products of differing viscosity or solidity can be dosed by a single PC pump as their flow rate is not affected by pressure or product viscosity.

Just as important, due to the constant, pulse-free action of PC pumps, the use of pulsation dampeners, flow control valves and ball valves is not required. This allows the pumps to be used in complex applications, such as dosing directly into product streams for in-line blending. They can also handle corrosive and abrasive materials. 

Right first time, every time
The benefits to manufacturers and processors of using PC pumps for dosing are multiple. By providing an accurate, linear flow they dispense the correct amount of ingredients every time, maintaining product quality. This accuracy also reduces wastage and means that overdosing, often required with pulsating pumps, is not needed, helping to keep down the costs of raw materials. As an automated process, it also saves on labour and forms part of a system that can help to control an inventory. In addition, dosing pumps provide traceability – essential for today’s food manufacturers.

What’s more, as flow valves, ball valves and pulsation dampeners are not required, installation and maintenance costs are reduced compared to alternative solutions. System costs are also lower, as the lack of pulsation reduces the wear on pipework. And as PC pumps can be wall-mounted or installed vertically, horizontally or even upside down, they are suitable for almost any site, including those with a small footprint or an unconventional layout.

The sweet taste of success
The use of PC pumps by Heineken in Hereford offers a good demonstration of their benefits. Successful cider making depends on accurately dosing ingredients to produce the correct flavour and colour profile, from variable raw materials. Heineken wanted to make improvements to its ingredient dosing process to ensure high product quality. The traditionally used diaphragm pumps, which dosed acids, sweeteners and colours into the cider, were difficult to maintain and recalibrate due to the pulsating nature of the flow, so Heineken turned to SEEPEX, who recommended hygienic PC dosing pumps to deliver all the ingredients required – even those with a high viscosity – directly into the product pipeline.

For Heineken, the use of PC pumps has eliminated problems caused by sticking ball valves and the high maintenance requirement, and the company has found the flow calibration simple and changes to the flow easy to make. Labour costs on maintenance and calibration have been reduced, downtime is lower, and spares costs have also dropped. Dosing control and accuracy have improved so much that Heineken has now replaced all of its remaining diaphragm pumps with hygienic PC pumps.

Smarten up?
Whatever your reason for specifying a dosing pump, it is also important to keep in mind the impact that Industry 4.0 will soon have on UK food manufacturing. All processes, no matter how simple, will benefit from being future proofed and ready to play a role in your smart factory –this includes dosing pumps. This is why the SEEPEX range of PC dosing pumps includes a Smart Dosing Pump (SDP). Users need input just one parameter – the proportional flow ratio – and the pump, featuring an integrated PLC monitor, will then make any necessary adjustments automatically. Once set, the flow rate is monitored and controlled entirely by the pump drive, which adapts to variations in operating conditions to ensure accurate, repeatable dosing. In addition, dry running and over-pressure sensors feed back to the drive to protect the pump from damage, helping to increase service intervals and the lifespan of the product. 

Lesley Eaton is business development and marketing manager at SEEPEX.

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