Today’s processing lines are complex and, increasingly, automated, making the detection of foreign contaminants in both raw materials and finished products more challenging than ever. Companies need comprehensive programs to ensure that contaminants never reach the consumer. Good manufacturing processes are an essential component of any overall program.
Explore this issueOctober/November 2008
While no single technology can guarantee that contaminants will not reach consumers, utilizing a variety of technologies can reduce the likelihood dramatically. Two types of technology that can effectively contribute to an overall contamination control program are metal detection and X-ray inspection. While neither of these technologies is new, both offer a high degree of reliability and have undergone dramatic improvements in terms of software, automation, and ease of use.
In the past, a human operator watched the monitor, flagging errors in products when the machine detected them. Today, no operator is required; instead, the system automatically rejects any predetermined setting or contaminated package. Today’s systems are also extremely user friendly. An operator with very little training can easily perform the initial product setup using a touch screen color monitor. With recent software advances and these ease-of-use improvements, plants are able to operate more efficiently while improving product safety.
Of course, all line operators must be trained in proper equipment use. Imagine if this key process was not in place. A device might be in place without a proper reject bin, for example, so that contaminated product simply dropped onto the floor. An untrained operator entering the scene might simply pick the product up and put it back on the line, not realizing it had been rejected due to contamination.
It is important to inspect the product at several stages of the production line. Even when a contaminant is found and rejected at the beginning of the line, it is still possible for a different contaminant to be introduced at a later point, resulting in a contaminated end product. Inspecting only at the end of the line does not make sense, either; this strategy results in much greater product waste. In addition to these procedures, each company must make certain that all ingredients are purchased from a supplier with equally strict inspection policies.
One of the most common product contaminants is metal. Metal contaminants can be introduced to product as shards that break off of machinery in the production line. If left in the product, such metal pieces can destroy equipment farther down the line, creating a much larger problem, with multiple fragments in more product. This kind of problem can grow exponentially if it is not caught early.
The potential for metal contamination makes a metal detector essential to any foreign object control program. With many installed throughout the world, metal detectors are well established in the food industry. Vast improvements in software have made them highly reliable and capable of detecting a variety of metal types, including the non-magnetic stainless steel that other forms of contaminant detectors like magnets cannot find.
The most common types of metal contamination found in a broad range of industries include ferrous (iron), copper, aluminum, lead, and various types of stainless steel. Of these, ferrous metal is the easiest to detect; relatively simple metal detectors, or even magnetic separators, can perform this task well. Stainless steel alloys, which are extensively used in food processing equipment, are the most difficult to detect, especially the common non-magnetic grades like 316 (SN58J) and 304L (EN58E). Non-ferrous metals such as copper and lead fall between these two. Only metal detectors that use a balanced three-coil system have the capability to detect small non-ferrous and stainless steel particles. A variety of factors influence a detector’s sensitivity and stability. The metal case itself has an effect, while minute movements of the coils in relation to each other can cause an out-of-balance voltage and a false detect signal. One of the major design issues to be addressed is the need for a totally rigid and stable system, one unaffected by vibration from motors, pulleys, auto-reject devices, temperature changes, transportation, and machinery nearby. Potting material, coils specification, and case design are crucial.