Advances in technology
Although inline detection equipment has been present in bakeries for many years, the past decade has seen rapid advances in controls and technology. Common threads include overcoming product effect and phase angle problems by monitoring multiple frequencies at once. These systems are also able to “learn” products on their own and eliminate noise and product effect, and some completely do away with manual tuning.
Fortress Technology engineered its Interceptor metal detector to put simultaneous multi-frequency operation to work for improving the system’s sensitivity. “It was designed specifically for the baking industry because it overcomes the issue of product effect,” Ms. Sharpe said. “The first use was for fast food hamburger buns, a product that has to meet very strict specs. It does this by processing multiple frequencies over a broad spectrum.”
Product effect will cause false rejections because conductive elements, such as moisture, salt or iron, alter the electromagnetic field of a metal detector, simulating the presence of metal when none exists, according to Heat and Control. The simultaneous and continuous use of multiple electromagnetic fields by the company’s CEIA THS/MS21 technology differentiates between metal and product effect. “This produces consistently accurate metal detection while preventing product waste and delays for re-inspecting suspect product,” the company stated. “It also permits reliable inspection of products having different characteristics on the same production line.”
TNA took advantage of new technology for its Hyper-Detect 5 system to solve weaknesses caused by the physical shape of the metal detector’s inspection gateway, according to Mr. Lozano. These systems are typically installed on snack packaging lines between the net-weighing scale and the bagger. “We changed the geometry of how product passes from the scale through the metal detector and into the bag,” he said. “The coils’ ability to detect metals is weakest in the center of the detection zone. With the new design, the product does not flow through the center. Therefore, you get higher detection levels and better accuracy.”
Adding learning and visuals
Because tramp metal presents such a danger, many operators verify the accuracy of metal detectors many times during the production day. This requires an interruption in service, and even though individual stoppages are short, they consume considerable time and labor when totaled.
Automatic testing was incorporated into the Halo software that runs Fortress Technology’s Interceptor. “Company procedures may call for hourly testing, and that can be awkward when the detector is installed in a difficult-to-reach position, say overhead or high up on a vertical form/fill/seal packager,” Ms. Sharpe said. “The unit still has to be tested at regular intervals, but now the automatic test features make it much less awkward for the operator. When considering labor savings alone, our Halo software can pay for the whole system in less than a year.”
Sesotec’s Intuity simultaneous multi-frequency metal detector is programmed to “learn” products. “It is designed to be not only simpler to operate but also predictive in results,” Mr. Pedersen said. “When it learns a product, it can forecast performance. Such prediction works well with the food safety procedures of a food facility.”
The new detector does something else. Its software performs concurrent analysis using signals digitized from multiple, simultaneous, variable frequencies to generate an electromagnetic image of the product, thus pinpointing the location of the metallic contaminant.
This new technology is a big departure from previous models that have the challenge of identifying the phase angle and sensitivity settings. “Current metal detectors have limitations due to fixed thresholds and phase angles,” Mr. Pedersen explained. “Small fragments can be hidden if their signal doesn’t exceed thresholds. Plus, metals that are the same phase angle as the product are not detectable.”
Bar and line charts — the way previous metal detector systems displayed measurements — are giving way to more graphic approaches. A visual depiction of the inspected product’s electromagnetic signature has far more meaning to the human eye than a bar graph moving on a screen, according to Mr. Pedersen.
CEIA’s THS Production software provides real-time visualization of metal detector status for either single or multiple units.
“The system will generate charts and reports as well as provide exportable data in HTML with digital signature and CSV format. Data is also configurable to export to an external SQL database,” the company stated in product literature. Users can edit and control systems via remote application on an Ethernet network instead of making adjustments on the factory floor.
The ability to learn product characteristics also applies to X-ray systems, Mr. Pedersen noted. “The operator of a Sesotec Raycon unit presses a button and feeds the product through; the machine learns the characteristics,” he explained.
Continue reading to learn more about X-ray systems.
