INDUSTRY FOCUS Food & Beverage
Sensing solutions for safer food
Many factors in the manufacturing process affect safety, but two of the most important are hygiene and temperature. Andy Walker of Ifm Electronic discusses new sensing solutions to keep these critical factors under tight control
P
roduction plant hygiene is an essential requirement in food manufacturing. This ensures product purity and minimal
risk of cross-contamination between product changeovers. Many modern food manufacturing processes rely on cleaning in place (CIP) to reach the required standards of cleanliness whilst keeping the plant downtime needed for cleaning to a minimum. CIP typically works by introducing cleaning fl uids into the plant and then fl ushing them out again, before the plant is returned to service. It is an excellent solution, but there are two key requirements: the concentration of cleaning solution must be correct, and all traces of the solution must be fl ushed out from the plant at the end of each cleaning cycle. Failure to satisfy either of these requirements could lead to product wastage and even a harmful product reaching the market.
As might be expected, food producers put rigorous procedures in place to minimise the risk of these problems occurring, but a more dependable approach is to directly monitor and measure what’s going on. The most convenient way to do this is to look at the conductivity of fl uids in the plant. The correct concentration of cleaning fl uid will have a relatively high and known conductivity, and the fl ushing a very low conductivity, once all the cleaning fl uid residues have been removed. While conductivity sensors are nothing
new, what is new is a sensor that can deliver the level of accuracy needed at high conductivity levels to confi rm the correct concentration of the cleaning fl uid, and also at very low conductivity levels to confi rm that fl ushing is complete. The new sensors achieve this partly by advanced design and construction and partly by using digital signals in the form of IO-Link, to send data to the control system. In contrast with traditional analogue techniques, the accuracy of signals transmitted via IO-Link are unaff ected by electrical noise and have no conversion (A-D) losses, making it possible to achieve exceptional resolution over a very wide measuring range.
automationmagazine.co.uk As well as helping to guarantee product
safety, using a conductivity sensor to monitor CIP can also boost productivity. The reason is simple: with the sensor providing positive confi rmation that all cleaning fl uid has been fl ushed from the plant, it is no longer necessary to prolong the fl ushing process “just to be sure”. This means shorter CIP cycle time, leading to increased plant availability and higher productivity.
Let us turn now to temperature, which is one of the most critical aspects of food processing techniques like pasteurisation, where even marginally incorrect temperatures can lead to serious quality and safety issues. Temperature sensors are commonplace, but here’s a question: if the calibration of a temperature sensor starts to drift, how much product will be compromised before anyone notices? A serious error is likely to be noticed quickly, but even then there may be considerable product wastage. A more subtle error may persist for some time before detection, which could mean whole batches of product have to be scrapped or even recalled. The remedy is a new type of temperature sensor that incorporates two sensing elements with opposing (PTC/NTC) characteristics. The sensor constantly compares the measurements from the two sensing elements which under normal circumstances match very closely. If a mismatch occurs, indicating calibration drift, this is detected immediately and the sensor provides a local visual indication as well as sending a warning to the plant control system. Like the conductivity sensors discussed earlier, these new temperature sensors use IO-Link digital communication to ensure that they deliver highly-accurate data to the control system. These new conductivity and temperature sensors were specifi cally developed for the food industry and therefore comply with all major national and international standards for hygienic applications. Whether used in new plants or as a retrofi t upgrade to existing ones, their cost is modest but the benefi ts they deliver in terms of enhanced product safety and peace of mind are invaluable.
CONTACT:
Ifm Electronic
www.ifm.com
Automation | November 2021
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