FEATURE PUMPS, VALVES & ACTUATORS UP TO THE CHALLENGE!
Lesley Eaton, business development and marketing manager at Seepex, describes how progressive cavity pumps can overcome tough processing challenges
P
rocess pumps are the world’s most popular piece of rotating equipment,
and in some plants they can represent as much as 85% of rotating equipment, and use 90% of all industrial electric motors. Despite pumps being essential to many processing operations, there remain challenges associated with choosing the correct pump for the job. However, developments in technology mean that the progressive cavity (PC) pump can deliver superior pumping ability while overcoming some of the common pumping headaches found in industry. Challenge 1: Maintaining product
integrity – The design of the PC pump moves the product through the pump in a series of cavities, which prevents slip from the discharge back through the pump. This means PC pumps have a very low shear action, preserving the quality of shear-sensitive products, such as multiphase products in the oil industry, polymers used in waste water treatment, and whipped products in food and beverage production. All of which are transferred without loss of integrity and functionality. Challenge 2: Lifting products–High
suction lifts of up to 9m can be achieved, making PC pumps ideal for lifting products from IBC, barrels or mixing tanks. The ability to pump against almost a full vacuum ensures the efficient use of degassing equipment and enhances many final food products too. Furthermore, surface-mounted PC pumps can lift from wastewater sumps, removing the need for submersible equipment. Challenge 3: Batch and continuous
dosing – The cavities have a given chamber volume which means the PC pump is ideal for batch dosing applications where specific amounts of product must be dosed accurately; for example, dosing tomato sauce directly onto pizza dough or addition of polymers or chemicals to make up tanks. Furthermore, since the flow has very low pulsation, dosing into mixers or pipelines delivers the right amount in a
smooth, continuous action, without the need for complicated controls or lengthy calibration methods. Challenge 4: Handling solid particles – The PC pump is able to handle solid particles without compromising either the product or the pump efficiency - suitable for applications as diverse as waste water treatment, to sauces containing vegetables and spices. They are used in any area where solid particles can cause downtime issues with other pump designs. Challenge 5: Variable flow rates –PC
pumps are available with flow rates from 100ml/hr to 500m³
/hr, and the ability to
handle temperatures ranging from -20˚C to 220˚C. As the flow volume is constant for each cycle of operation, and is proportional to the rotational speed, calibration is simple and is unaffected by the viscosity of the product, unlike some pumps which slow when viscosity is high. This linear accuracy means that only one variable – pump speed – needs to be changed to vary the flow volume. Challenge 6: Viscosity – PC pumps’ suction characteristics means they can handle a wide range of viscosities; from water to products with viscosity over 1,000,000 cps. The pumping action means that variations in viscosity do not affect the flow rate. This offers practical advantages such as accuracy, process stability and reduced downtime. Challenge 7: Solids pumping –There are some instances where products don’t free flow hence the development of auger mechanisms to constantly feed non- flowable media into the pumping elements. The use of these mechanisms push product that do not flow into the
Lesley Eaton is business development and marketing manager at Seepex
PC pumps are used in waste water treatment applications
pumping elements, so they can then be moved through pipes (the alternative would have been to use a conveyor). This technique makes long distance transfer possible, plus waste products from production areas can be moved to the factory exterior. In addition, the development of sophisticated auger mechanisms in some PC pumps means that they have the ability to handle and even mix solids. Challenge 8: Design compatibility – Corrosive and abrasive products, water industry standards, strict hygiene requirements, low/high pH, or high temperature, are all factors that need to be considered when configuring or choosing a pump. PC pumps can be constructed – and the product feed mechanism adapted – in line with the application requirements, whether that is CIP capability or chemical resistance. Challenge 9: Operating pressures –
Seepex food grade pumps meet strict hygiene standards
Pumps have to overcome pressure when transferring products, and PC pumps are able to generate pressures up to 48bar as standard. This is due to the interference fit between the rotor and stator plus the absence of slip between the pumping elements, meaning that they can pump long distances - many km in some cases! Challenge 10: Installation and operation – PC pumps are easy to operate and install. They have both forward and backward pumping action in the same pump, so one pump can often do the job of two alternative designs. They can be installed horizontally or vertically, making them ideal for factories with restricted floor space, and designs such as Seepex’s Smart Conveying Technology have smaller installation needs.
Seepex
www.seepex.com
12 SEPTEMBER 2017 | PROCESS & CONTROL
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