boilErs, PumPs & valvEs


example and instead Bürkert would use an angled seat valve with a PTFE seal, suitable for use with nitric acid and ensuring that it can achieve its seven million cycle lifetime. It is important to select the body and seal materials most effective for use with the chemicals in each specific application. PTFE is commonly used for seals,


diaphragms, as well as valve bodies. Resistant to nearly all chemicals, including acids and alkalis, PTFE is an ideal choice for CIP applications. Its carbon-fluorine bonds make it inert and therefore ideal for use with reactive and corrosive chemicals. It is, however, susceptible to cold flow, which is distortion under stress of high temperatures or temperature fluctuations. Advanced PTFE can instead be specified if the application includes extreme temperature changes or frequent sterilisation. Alternatively for diaphragm use, GYLON is


a third generation PTFE, which is used across the widest range of applications. With increased resistance to stress, it can be used


EHEDG ProGrEssivE cavity PumPs for HiGHEst ProDuct quality


S


with greater fluctuations in temperatures as well as higher temperatures, and has a longer lifetime. EPDM is also frequently used for diaphragms and seals because of its resistance to ozone and hot water, as well as FKM which is often selected for its resistance to oil. Valve bodies are frequently brass or stainless


steel, or a suitable hard plastic variant with sufficient impact resistance. Polypropylene and polyethylene are commonly selected for their resistance to various organic solvents, acids, bases and salts while polyamide is appropriate for use with greases, oils, waxes and fuels. Meanwhile, PPS is ideal for use in high temperatures above 200 degrees centigrade. The chemical composition of the valve


components and the media flowing through it are critical factors for a wide range of applications. The challenge can be complex so engaging the right application expertise is well advised.


Bürkert Fluid Control Systems www.burkert.co.uk


UKManufacturing Summer 2021 41


EEPEX’s latest design of hygienic progressive cavity (PC) pump has achieved EHEDG certification, delivering the highest microbiological results with residue free cleaning guaranteed using CIP systems.


The EHEDG pump is the latest addition to the Seepex’s range of hygienic PC pumps which


are used widely wherever thin to highly viscous, shear sensitive products and those containing soft solids need to be transferred. Food processors have to ensure that product quality and viscosity can be maintained throughout processing and packaging; selecting the best pumps for shear sensitive products is therefore vital to deliver the best product to consumers. Traditional pumping systems can have a detrimental effect on the quality and texture of


some dairy products, particularly yogurt, with shear stresses changing the product consistency by shear thinning, producing a ‘thin runny’ product. Often costly additives are used to preserve or restore product quality changes; however,


there is another solution – the use of progressive cavity pumps with their gentle, low shear action, ability to handle soft solids without damage and minimal pulsation flow rates.


SHEar StrESS – baCkflow anD ‘SlIP’ Traditionally, twin screw or lobe pumps are used to handle products such as yogurt after the fermentation stage, when the product has set. The running clearance between the screws or lobes results in backflow– also known as ‘slip’ – and this is the main cause of shear-thinning which, in the case of yogurt production, can cause breakdown to a runny, thin product. The higher the pumping pressure, for example through heating or cooling equipment, the more this slip increases. SEEPEX PC pumps are known for their gentle handling of viscous products. This is due to their


unique design, which enables the product to move through the pump in a series of cavities. These cavities are not compressed or distorted in any way, creating a gentle, non-pulsating flow. This ’non- slip’ action preserves the quality of shear-sensitive products such as yogurt. Additionally, minimal pulsation action creates a smooth laminar flow through pipelines and ensures a constant feed through heat exchangers, minimising mechanical stress and product thinning. SEEPEX PC pumps are used in many dairy manufacturing plants globally, including for


pumping fruit yogurt where the ability to handle soft solids without damage is essential for maintaining fruit piece integrity. PC pump flow has minimal pulsation and linear accuracy, delivering accurate dosing with simple calibration and controls when adding flavours and syrups either in batch or in-line into liquid or viscous products. www.seepex.com


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