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FEATURE MACHINE BUILDING, FRAMEWORKS & SAFETY
sponsored by DESIGNING A SOLUTION TO FIND
A ‘NEEDLE IN A POTATO SACK’ To keep potato products free from metal contaminants, Fortress has designed the
industrial-sized Bulk Potato Slider Detector System A
s one of the world’s most versatile, main food crops, demand for potatoes never drops. With 5.31 million tons of potatoes harvested annually, and an annual UK farm gate value worth £703 million, ensuring crops are free of metal contaminants is essential. However, in October 2014, potato processors suffered a serious
industry blow – the discovery of needles in potatoes for one large international farmer resulted in a nationwide recall of nearly one million pounds of produce. Although no sharp metal objects were detected in produce farmed by Fortress customers, one major potato
processor took proactive steps to reassure its extensive supplier base and prevent an incident of this magnitude occurring. Now, three robust industrial-sized Fortress metal detectors are being used to inspect 140,000 pounds of potatoes every hour.
DETECTING METAL FRAGMENTS Without upstream inspection, a potato containing a needle could unknowingly be thinly sliced into crisps, and the subsequent metal fragments may be too small for even the most sensitive downstream metal inspection systems to detect. For a market that’s worth over £2 billion annually, crisp producers are eager to ensure their suppliers have robust inspection systems in place to help eliminate contaminants in root vegetables before processing. In addition to needles, drink cans discarded in crop fields, machinery nuts and bolts, or wire fencing blown
down in a storm, can all be turned into the smallest metal fragments by powerful harvesters – and these can easily disperse and embed contaminants into crops. So, the prominent crop processor swiftly installed three industrial-sized Fortress Bulk Potato Slider Detector Systems to help guarantee high standards across the potato supply chain.
AN ACCURATE DESIGN When creating the design, Fortress was mindful that potatoes have a number of product attributes that could affect the accuracy of the metal detectors. Fortress european managing director, Phil Brown, explained: “Potatoes are typically washed and wet. They are neither super clean or dry, and they come in all different sizes.” These factors can impact a metal detector’s ability to distinguish between the potatoes and any metal contaminants introduced, leading to false signals and consequently wasted produce. To ensure the potatoes were run at the highest performance level, Fortress engineered a special VLF (very
low frequency) coil. This allows all potatoes to appear as dry products on the machine, essentially ignoring the product effect caused by soil, grit and moisture. Another essential feature designed for harsh, rigorous production environments, is the BSH rugged casing. This
helps to provide better stability and metal detector performance for when rolling potatoes collide with the sides of the system as they are funnelled down the conveyor. Another challenge Fortress addressed was orientation effect, especially when trying to detect long, thin needles.
Typically, these contaminants will be embedded within the potato or root vegetable. Detecting any fragments will depend entirely on the direction that a bouncing potato is passing through the metal detector. In one orientation, the signal for the needle may be huge, but if turned 90 degrees the needle may pass through the metal detector’s electromagnetic field undetected with little to no disturbance. To combat this, Fortress engineered the metal detector with a rolling-system rather than traditional belt, which
provides a stronger signal than stagnant objects. “The potatoes roll through the metal detector to limit the chance that a needle misses detection due to orientation effect,” added Brown. According to the company, the technique worked remarkably well in all test cases, with the customised metal detection unit reporting minimal false positives and superior accuracy and metal detection sensitivity. Warehouse floorspace and how the reject system could align with other design features were also carefully
addressed. Brown explained: “Space on farms is often tight. Products also roll through at fast speeds, making it challenging to account for the placement of potatoes as they pass through the metal detectors. The benefit of our roll-through design is there is no belt. Instead, a flap expels contaminated product to the reject area below.” A simple conveyor with a low-maintenance UHMW slider bed was integrated alongside the farmers existing
cleaning and grading systems, resulting in an optimised and cost-effective solution. Although product tampering is extremely rare, in the last decade Fortress has observed a large uplift in enquiries from root vegetable and potato farmers, and bulk processors, for robust gravity and conveyor metal detection systems. These can help to prevent future adulteration and contamination events from causing potentially catastrophic damage to brand reputations.
Fortress Technology (Europe) T: 01295 256266
22 DESIGN SOLUTIONS NOVEMBER 2023
https://fortresstechnology.co.uk
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