Quality checks are a fundamental part of food and beverage processing, and companies make extensive use of them to assure that finished goods are consistent and safe.
Screening for biological contamination is necessarily done in a laboratory, and scientific advances have considerably shortened the turnaround time for test results. Nonetheless, thousands of pounds of product can move through a production line in the interim, putting a high cost on contaminant-positive results. The ideal solution is in-line inspection, and while that’s impossible with microbes, considerable progress has been made with other quality factors.
Metal detectors, checkweighers and X-ray machines are the industry’s core in-line tools. Production facilities lacking at least two of the three are few and far between. Checkweighers maintain a tight tolerance between short-weighting and product giveaway – a business essential but not a food safety concern. But potential customers would turn and run in the absence of either metal detectors or X-ray units.
Baby food manufacturers were among the first processors to adopt X-ray inspection to protect against glass fragments. Metalized film drove other firms to X-ray machines, and for awhile it seemed the X-ray option would become the technology of choice for end-of-line contaminant inspection. A funny thing happened on the way to market domination, however: metal detectors became more versatile and precise.
Multi-frequency machines have been introduced by most of the major metal detection suppliers in recent years, but “there was something of a Rube Goldberg feel” to the first generation, according to Steve Gidman, president of Fortress Technology Inc. (www.fortresstechnology.com), Toronto. Machines had too many moving parts, and outcomes represented only incremental improvements in the tradeoff between increased sensitivity and excessive false positives. Only recently have software algorithms that analyze signal data caught up with the potential value of both low- and high-frequency signals.
Fortress recently rolled out an enhanced Interceptor metal detector that simultaneously reads two frequencies and can accurately inspect products packaged in metalized film. “The gain we’ve made with a coil structure that can take advantage of multiple frequencies is thousands of times better,” Gidman says. “The performance with metalized film is comparable to an X-ray machine’s capabilities.”
The primary target of the detector, however, is products that are naturally conductive, those with high moisture, salt and acid content. Previously, detector adjustments to compensate for conductivity lost the ability to detect stainless steel and other nonmagnetic metals. “Non-ferrous metal detection suffered a bit, too,” notes Gidman.
Simultaneous multi-frequency systems overcome those limitations by distinguishing between signals that define the product and those that indicate anomalies.
Eriez Magnetics’ metal detectors can’t inspect products packaged in metalized film, concedes Ray Spurgeon, product manager-metal detectors at the Erie, Pa. firm (www.eriez.com). But for food companies that want to detect contaminants upstream of filling, Eriez now offers a compact detector called Vertical Xtreme.
The unit can be integrated with a vertical form/fill/machine, prior to filling, although Spurgeon suggests a more effective placement might be adjacent to a permanent magnet separator on a hopper for free-flowing materials. In that scenario, the detector verifies the thoroughness of the separator.
“Removing metal before the material is pulverized or crushed and metal is fragmented into a thousand pieces can save a lot of downtime,” he points out.
The detector itself doesn’t require a metal-free zone around the sensing head, making placement practical in close proximity with piping and machinery. Fragments as small as 1mm can be detected. Perhaps the biggest functional improvement is the operator's icon-based color touch screen. Spurgeon likens it to a smart phone: “It’s intuitive technology.”
A “user-friendly interface” and large color screen also is touted by Kathryn Bors, brand manager for Loma Systems’ IQ4 metal detectors. Both ferrous and nonferrous metal detection has improved incrementally, although Bors declines to say how much, but the HMI upgrade is more meaningful for food processors, she believes.
Operating parameters are communicated with visual prompts, and set-up time for different products is accomplished in 3-4 sample runs. But automating the learning process and communicating it in multiple languages may provide a bigger benefit to users, Bors suggests.