Metal detection technology has recently emerged as an attractive alternative to conventional X-ray inspection methods, being a much less expensive system than X-ray systems while keeping much the same performance in many applications.
Metal detectors in the food manufacturing industry are used to detect and eliminate threats of tramp metal contaminants in food goods.
The detection of these particles can make or break a young business, and save established manufacturers from losing product and brand quality to metal contaminant recalls.
The Two Metal Detection Systems
Modern metal detectors operate using two main techniques, the ‘Balanced Coil’ system, and the magnetic ‘Ferrous-in-Foil’ system.
The first industrial metal detection system, the Balanced Coil system has evolved from tubes and transistor circuits to today’s DSP based systems (Digital Signal Processors) and are still the most popular choice for general-purpose metal detection.
Ferrous-in-Foil detection systems make use of a full loop electro magnet primarily to detect ferrous metal and magnetic stainless steel in aluminum packaged products.
Both are accurate and efficient metal detection processes, and serve a wide array of real world applications, most prominently in the inspection of food.
But how does this technology work?
The Balanced Coil System
Metal detection is made possible through a principle known as the Balanced Coil Full Loop System.
Three coils are wrapped around the aperture through which the product passes. In the center of the enclosure is the transmitter coil that broadcasts a radio frequency signal and generates an Electro-magnetic field.
Equally spaced on either side of the transmitter coil are two receiver coils
Anything that enters into this field that is either Magnetic, or Electrically Conductive will cause a disturbance in the field strength around it. All metals have either one or both of these characteristics and will be detectable if the size of the signal is large enough.
The signals from the receiving coils are connected in opposition to each other and therefore when no disturbance is occurring there will be a net signal across the coils of zero – they are balanced.
This forms the electrical equivalent of a balance weigh scale
As metal passes through the detector the balance will be offset as the contaminant enters the aperture and again as it leaves the exit side. This disturbance is amplified and analyzed by the control electronics and detection will occur if the sensitivity threshold has been exceeded.
The Ferrous-in-Foil System
Unlike the Balanced Coil System, the Ferrous-in-Foil system of metal detection detects magnetic metals in products that contain Nonferrous packaging or components.
In this case, the system’s aperture contains a powerful electro magnet.
Magnetized particles detected by the system create a disturbance which is then intercepted and amplified by the detector’s electronics and transmitted digitally into the detector’s user interface.
The Ferrous in Foil detector is capable of detecting Iron, Steel and Magnetic stainless steel. In the food industry inspection of pies in aluminum foil trays is a typical Ferrous in Foil application. In the textile business ignoring brass zippers in garments while detecting steel sewing needles is a good example.
The User Interface
Today’s industrial metal detectors come equipped with a fully integrated user interface, which electronically communicates with the receiving coils and translates the signals they send into functional data.
The typical interface will record results of Q.C. tests, time/date of detection, relative size of the tramp metal sample and all detector settings. Proximity sensors connected to an automatic reject device can also confirm the reject device is working correctly.
The ability to use interfaces such as these gives manufacturers incredible insight into the system’s running statistics, component and signal messages, and analytical information. The use of these interfaces drastically streamlines and improves the management of metal detectors and aids in traceability in the event of a recall.
Metal Detection and Its Place in Food Production
Today, the food industry produces goods with the utmost efficiency, creating as much quality products as possible in a given period. To protect brands and consumer appeal, many companies have adopted and implemented high-end metal detection technologies in their production lines.
The metal detectors used in contemporary food production are a less costly alternative to X-ray inspection systems and have a lower cost of ownership. The detection technology also meets HACCP requirements.
This ability to detect imperfections and unsuitable products before they reach the consumer is a strong advantage to have in any food business, aiding to prevent any brand-ruining recalls or legal actions that may come from manufacturing unsafe products.
Learn More about Metal Detection in the Food Industry
To learn more about the role metal detection plays in food production, please download our free ebook, “Metal Detection – A Practical Guide to Metal Detection in the Food Manufacturing Industry,” or contact us directly.
