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Certificates of Compiance
Is There an Expiration Date for Certificates of Compliance?
August 1, 2024
Stay Food Safe While Celebrating with Family and Friends
Stay Food Safe While Celebrating with Family and Friends
October 1, 2024
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Aluminum vs. Brass

Aluminum vs. BrassAluminum vs. Brass in Metal Detection

Here at Regal Packaging Services, we are sometimes asked about using certified aluminum spheres for our test pieces. Brass has long been the standard non-ferrous material for testing metal detectors in the food industry. Brass is typically used because it has a high electrical conductivity property that metal detectors can detect.   Brass is an alloy (copper and zinc) that is non-magnetic. All non-ferrous metals are detected by a metal detector through conductivity.  Non-Ferrous metals create an electromagnetic field, that disrupts the detector’s magnetic field.

Interestingly, aluminum is exceedingly rare in native form, and the process to refine it from ores is complex, so for most of human history it was unknown. In fact, “Now ubiquitous and vital to modern life, aluminum was once more expensive than gold…The most familiar story of the first extraction of aluminum is that the youthful Ohioan Charles Martin Hall developed aluminum’s electrolytic extraction process in his family’s woodshed in 1886…The company Hall helped found drove the price down to below $1 per pound by 1891, and when a lightweight aluminum crankcase for their engine enabled the Wright Brothers to take their famous first flight, the metal was about $0.30 per pound.”1

“High purity aluminium is a soft material … which limits its usability in industrial applications.”2 This may be another reason brass was chosen as the standard for metal detection testing in the food industry.

However, because some companies have aluminum components along the production line, there’s always a concern that testing should be required for that type of metal either in place of, or in addition to, the brass.

FDA regulations3 state that a company must:

“Develop sensitivity standards that are based on whether the potential hazard is ferrous, non-ferrous, or stainless steel, or obtain such standards from the equipment manufacturer.” Unfortunately, it does not specify what type of ferrous, non-ferrous or grade of stainless steel should be used in testing. When it comes to ferrous, there isn’t really a better choice than chrome steel.  “Chrome plating steel is any type of steel that has been mixed with chromium with the aim of preventing rusting. This type of steel has undergone a process known as chrome plating.”4

Stainless Steel (alloy) 316 is the best choice for this kind of steel. 316 is the least magnetic or conductive of the stainless steel alloys used in the industry. The simple theory is that if you capture and reject SS 316, you’ll also be rejecting 304 and other types of stainless steel.  Conversely, if you test using 304, you may not be rejecting 316.

So, what about non-ferrous? In our own in-house testing, we have found that aluminum and brass will perform (be detected) nearly identically in both wet and dry modes.  What’s critical then, is choosing the metal which is most commonly found on your production line and writing that into your HACCP plan and SOPs. If any change is to be made, thorough testing should be done before implementing any new practices.

But there is one benefit to using brass over aluminum, and that is its availability within the test piece market. There is a much wider variety of sizes available in brass than you will find in aluminum. So, for instance, you might find 2.8mm Brass, but you may not find 2.8mm Aluminum. So if your standard isn’t a common size, getting the right aluminum test piece may be difficult.

There is also a vast difference between aluminum and brass in x-ray inspection. Aluminum is much less dense (2.7g/cm3) than brass (8.48g/cm3). So comparably, while brass would be easily visible, aluminum would be harder to detect. And if the goal is to keep as many contaminants as possible out of the product, then using a lower density material for testing just makes good sense, so long as the product density itself doesn’t interfere with the test standard visibility.

The bottom line, in general then, is that it’s a good idea to maintain the industry standard use of brass over aluminum unless your HACCP plan and SOPs have been written specifically for aluminum and you have aluminum on your production line.  You’ll find aluminum and non-ferrous (brass) testrods, acetal test cards, laminate cards and thermoform cards right here on our website.

 

  1. https://sciencehistory.org/stories/magazine/aluminum-common-metal-uncommon-past/
  2. https://material-properties.org/brass-vs-aluminium-alloy-comparison-pros-and-cons/
  3. https://www.fda.gov/media/80342/download
  4. https://www.rocheindustry.com/chrome-vs-stainless-steel/

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Floatable Thermoform Test Cards

Some applications involve large tubs, vats, or some other type of product travel where it would be nice to have a test piece that floats. Once again, our thermoform cards provide the simplest solution. We simply insert some type of structure that forces the thermoform card to retain air, which, of course, is what makes it float. We have also manufactured floating rods, which are more difficult because there is less space to close in enough air to make the rod float but is doable.

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We took an ordinary plastic “chip clip” as defined by the customer and embedded the contaminant into the clip. The clip can be attached to the product on the line without damaging or opening the product for testing purposes.

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Bone is a difficult contaminant to find because it can vary widely based on the size, age, and calcium content (as well as feed used) of the animal. After working with several customers, Regal Packaging Services offers Pork, Beef and Chicken Bone Simulate. We have a small range of sizes at a variety of depths to simulate whatever you might expect to find in the product. Our recommendation (assuming your x-ray has visual display) is always to start with a multi-card. Using a multi-card gives you an easy way to test several sizes and depths to determine what matches the bone you’re using. Once you’ve made a comparison, testing the card against the bone you’re looking for, you can purchase a card with a single contaminant for regular testing.

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This small pill shaped test piece is used in a system with a vacuum tube that shoots the test piece through the aperture and returns it to the “home” base. Your system may never be like it, but the point is that we can make a customized solution no matter how unusual or impossible it might seem.

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As you may have seen in some of the other thermoform card descriptions, we can put nearly as many seeds as you can imagine on a single card. Pictured here you will find a wide variety of configurations and contaminants. Just let us know your specs: size of the card (up to 8” x 8”) along with size and type contaminant(s) and we’ll get you a quote as quickly as possible. Working with a multi-card is especially helpful when you are looking for multiple types of contaminants or when you want to determine what size of the same contaminant you are able to detect. In that event, once the size is chosen, you can order individual card(s) for regular, standard inspection and detection.

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There are a wide range of applications that require a test piece much longer than our standard 5” or 6” Testrods. We can make up to 3/8” x 34” or 1/2” x 34” rigid test pieces which can then be extended well beyond that length with a “handle” made of acetal cylinder larger than the 3/8” or 1/2” extension. In the photos, we used a 1” x 24” cylinder handle with a 3/8” x 24” inch extension.

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Test pieces can be made in a variety of sizes and given a pointed end in applications that require the contaminant (metal) to be inserted into a food package such as sugar or some other soft packaged food product. This allows the metal to reach the center of the aperture.

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Double-End Test Whips are also available, with metal in both ends. One consideration is to make certain that the whip is long enough to keep the metal on the non-testing side of the whip outside the metal free zone of your detector. If you insert, for instance one end of a whip with 2.0mm and 3.0mm Ferrous, you need to make certain that the 2.0mm metal doesn’t affect the detection of the 3.0mm metal (and vice versa). If the 3.0mm metal is inside the metal free zone, then the detector will be reacting to the 2.0 as well as the 3.0 as if they were combined.

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Multi-seed laminate test cards are designed for seeds 4.0mm or less. Multi-cards are useful in x-ray inspection to determine what sizes and types of contaminants your system can achieve. They can be especially useful in temperate environments and applications. If your application is rugged or wet, or your standards are larger, we recommend our thermoform multi-cards.

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We can simulate a variety of packaging in an application where you need the test piece to mimic what is traveling down the production line. In this case, we manufactured a clear “package” with the seed inside. With this method, the customer is able to reject the container appropriately, and, in the event the package is not rejected, it is easily seen by the line worker for manual removal.

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There are two types of “candy bars” pictured here – one similar to a flat candy bar and the other in a custom, near perfect copy of a candy bar. Since we’re now able to produce many variations using colored material, the copy was made in red (Fe), green (NFe) and blue (SS 316). We have the equipment to accomplish nearly anything you can imagine, and these kinds of designs are proof positive.

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Need a test piece that looks and handles like chicken nugget? We can do it. Interestingly enough, in this situation, our first version for the customer left too much “void” in the hole where the metal was placed. Given the sensitivity the customer system was using, the void had the effect of causing false positives. We were able to minimize that hole and supply the test piece with almost no void. It’s an example of how we can work with you before, during and after manufacturing to ensure all the specifications were met.

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Our standard acetal card is 2 1/4"x3 3/8,” but if needed, we can cut that size down to as small as 1 1/4” x 1 1/4” (with limited engraving). If a larger card or a card with multiple seeds is needed, see our Custom Shape-Size Blocks and Tablets.

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This distinctive test piece was created to mimic an actual hamburger patty. The customer supplied photos of the raw product, which we were able to reproduce and then we placed blue glove contaminant. Using this configuration, the customer was able to determine what size piece the vision scanning system could detect with the raw burger as the background. Had they simply used a blank card with the glove, the system could easily have achieved contaminant rejection, but they needed to be sure the system could “see” the blue against the product itself.

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A card with 100 seeds in a 10x10 configuration is used to place beneath whole chickens on a production line. This gives the x-ray system operator the ability not just to see IF the equipment can detect the metal in the card, but also WHERE the equipment can detect it. If there is a problem, the operator (or company) can make any changes necessary to achieve the end goal – safe chicken in this case. This card really highlights another valuable facet of our thermoform cards.

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In this scenario, a company processing sugar needed to have a “bag” simulated with the same weight in order to accurately fall through the reject mechanism. A lighter test piece had the risk of passing over the reject mechanism.

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Our standard cubes are 1” and 1.5,” but we can also manufacture other sizes if needed. The cubes shown here are 1/2" in dimensions. Cubes can be helpful in applications where a ball or cylinder may bounce or roll away during testing, making their retrieval difficult, or, in some cases, present a hazard to the product or production equipment.

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This is a test piece that is dropped into a bottle. It’s designed so that the metal appears in the center of the aperture when testing the metal detector. In addition, the round stop makes the test piece easily removable after testing.

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Hexagonal Shaped test pieces can be very useful in places where a cylinder or ball might roll or bounce around a production floor whether dropped by a line worker or ejection from a reject mechanism. Hexagons are similar in weight to the 1inch cylinders without having the smooth, rounded cylinder edge.

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Our customer in this plant needed a test piece with a thickness less than 5.0mm. Because we have the capacity to customize sizes and shapes, we were able to mill down a product that met their specifications. That’s always our goal, meeting the specs you need for your product, testing environment and contaminants.