PUMPS, VALVES & ACTUATORS FEATURE TAKE YOUR FINGER OFF THE PULSE
Dosing pumps are essential for dispensing a constant, accurate amount of product every time. According to Lesley Eaton, business development and marketing manager, SEEPEX, progressive cavity (PC) pumps are fast becoming the dosing pump of choice
D
osing pumps are specified when accurate control of dispensing
ingredients or products is required. Examples of applications include adding colourings or flavourings to food products, and accurate dosing of chemicals in wastewater treatment. In such tasks, it’s essential that the ingredients or products being added are dispensed at a constant, proportionate rate to ensure even mixing and distribution. However, 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. Furthermore, some of these pump designs 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. In the case of SEEPEX’s PC dosing pumps, this produces a stable flow rate with a linear accuracy of +/-1%. Another benefit of PC dosing pumps 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 dough sheets. The action of PC pumps is low-shear and can therefore
dose traditionally difficult-to-pump solid, semi-solid or shear-sensitive materials without damaging them, such as: buttermilk, yogurt, ice cream, polymers and flocculants. In fact, a variety of different products of differing viscosity or solidity can be dosed by a single pump, since the flow rate of PC pumps is not affected by pressure or product viscosity. They can also handle harsh, abrasive chemicals, such as ferric sulphate dosing at wastewater treatment plants or anaerobic digestion facilities. Also, due to the constant, pulse-free
action of PC pumps, the use of flow control valves and ball valves is not required. This means that they can be used in complex applications, such as dosing into and from chemical tanks. For manufacturers, the benefits of 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 manufacturers. The flexibility of the pumps mean they can be specified according to customer needs. In line with Industry 4.0 requirements, SEEPEX’s range of PC dosing pumps includes a Smart Dosing Pump (SDP). Users input just one parameter – the proportional flow ratio – and the pump, featuring an integrated PLC monitor, will
PC pumps can be wall- mounted or installed vertically, horizontally or even upside down, so they are suitable for almost any site, including those with a small footprint or an
unconventional layout
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. The SDP is easy to operate, comprising a
PC pump with an intelligent inverter drive which is programmed either locally via an HMI or centrally via a fieldbus interface. It can also be controlled via analogue/digital I/Os, either locally or remotely by a PLC. Successful cider making depends upon
accurately dosing ingredients to produce the correct flavour and colour profile for each cider product. Heineken in Hereford was unhappy with its existing diaphragm pumps, and wanted to improve ingredient dosing to ensure product quality. The company turned to SEEPEX, who
recommended hygienic PC dosing pumps to deliver all the ingredients required, directly into the product pipeline. The PC pumps have eliminated the
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
problems caused by sticking ball valves and the high maintenance requirement, and Heineken has found the flow calibration simple and changes to the flow easy to make. Dosing control and accuracy have improved so much that Heineken has since replaced all its remaining diaphragm pumps with SEEPEX hygienic PC pumps.
SEEPEX
www.seepex.com
PROCESS & CONTROL | MAY 2018 17
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