Magnetic Separation and Metal Detection for Cereal Processors

Metal contamination in cereal products poses a significant risk to manufacturers and consumers. If metal contamination is present in a final cereal product, a consumer may be harmed, and the manufacturer’s brand reputation will be significantly harmed as well. Additionally, metal contamination can cause extensive damage to other equipment in a facility if it is allowed to remain in cereal throughout the manufacturing process.

To achieve optimal removal of metal contamination, it is recommended that food processors install a comprehensive system that incorporates magnetic separation as well as metal detection. Magnetic separation removes ferrous metal contaminants, while metal detectors are able to detect and remove ferrous, non-ferrous, and stainless steel metal contaminants. Certain magnetic separation and metal detection equipment is best installed at different key points in the processing line to provide maximum protection of equipment and reduce downtime.

When processing raw bulk grain material for use in cereal products, magnetic separation must be introduced at the earliest stage possible. As raw bulk grain material enters a plant from a truck or rail car, there is a high likelihood that there is metal contamination hidden within it. The contamination is typically ferrous metal, originating from machinery or stray nuts, bolts, etc., that may have broken off or otherwise entered the raw material. If material is being unloaded from a vehicle by a gravity free-fall mechanism, a heavy-duty grate magnet may be placed directly where material is being unloaded. If material is being pneumatically conveyed, a pneumatic inline magnet and a pneumatic metal detector may be placed at the equivalent earliest stage in transport.

After material enters a facility, it is conveyed to large incoming storage bins. To prevent metal contamination from entering these storage sites, a hump magnet or drum magnet may be placed directly prior to the entrance of these storage units. These large, heavy-duty magnetic separators are excellent for flowing high volume product. Hump magnets are uniquely beneficial because they are designed to break up material as it flows through the chute and over the plate magnet housed within, reducing the problem of bridging, choking, and build up. Drum magnets allow material to flow over the rotating face of the drum, which helps to dislodge non-metallic product from the magnetic materials being extracted. Gravity free fall metal detectors, particularly cowbell style metal detectors, are also suitable for installation at this point and will be able to detect and remove ferrous, non-ferrous, and stainless steel contamination.

Installing magnetic separation equipment at this point is critical, as bulk metal contamination not removed at this early stage in the process can cause severe damage to other equipment in a processing facility. Bulk materials such as flour, oats, or other grains are processed through a sifter shortly after they arrive in a facility so that debris such as stones, twigs, and other large items are removed while smaller sized cereal grains pass through screens unhindered. While screens and sieves may capture large pieces of metal contamination, smaller metal particles will easily pass through the fine mesh of the screen. Large metal pieces also have the potential to cause metal-on-metal wear and abrasion to the screens or sieves, causing them to deteriorate and their parts to break off. Installing a magnetic separator prior to the sifting step significantly reduces the risk of damage to your screens.

After raw materials have been initially processed and brought into the plant, the process to turn them into a cereal product begins.

After raw materials have been initially processed and brought into the plant, the process to turn them into a cereal product begins. The most common method used in this process is extrusion, which forces soft blended ingredients through an opening with a perforated plate or die that produces the correct shape. The product then goes on to be cut by blades to a specific size.

The first step in the extrusion process is for raw materials to be ground down to an appropriate particle size, typically similar to a coarse flour consistency. Before material is allowed to pass through a grinder, it is important that it first passes through a magnetic separator or metal detector, as any hidden metal contamination in the raw material can damage the grinder. A grinder coming into contact with metal contamination risks damage as metal-on-metal wear occurs between the grinder and the contaminant metal fragments. For this reason, it is strongly recommended that raw material pass through a magnetic separator or metal detector prior to entering a grinder.

Once material has been ground, it enters the extruder where the cooking process takes place. Once material has been cooked within the extruder, it is forced outwards through the die by the extruder’s rotating screw. This die is responsible for creating the shape of the cereal product. If metal contamination remains present in material that has entered an extruder, there is the risk that contaminant particles will damage the die of the extruder. If the die comes into contact with metal contamination, it can become damaged and continuously degrade over time, leading to additional metal contamination entering cereal as it is extruded. This leads to a compromised product shape, an interruption to the process, and a risk for continued damage down the line.

After being extruded, material will then be cut into the desired size. If metal contamination is present in the extruded material, this contamination can damage the cutting blade and, again, lead to more metal contamination continuously entering the product.

Metal contamination may also enter a cereal product from other ingredients. Common ingredients added to cereal mixtures include nuts and dried fruits, and both possess similar risks of encountering contamination. Additional ingredients must be subject to the same standards of rigorous metal contaminant removal as base grain ingredients.

As you can see, a failure to remove metal contamination at even a single critical point leads to a domino effect that results in greater and greater amounts of metal contamination entering a processing system. This ultimately results in extensive damage to equipment, profit and productivity lost as a result of downtime, and damage to a manufacturer’s brand name and reputation should a customer consume a contaminated product.

Placing magnetic separation and metal detection equipment must occur at the most critical process points.

For the most rigorous standard of metal contaminant removal, it is best to place magnetic separators and metal detectors before and after key processing equipment such as extruders. Magnetic separators are most critical early on in the process, as they excel at removing the ferrous contamination most associated with ingredients that have not yet undergone extensive processing. Metal detectors are highly valuable due to their ability to detect stainless steel, which is a predominant material used in food processing equipment. Installing magnetic separators and metal detectors at multiple points in a processing line not only removes contamination, but can also provide valuable insight to places in a processing line where equipment may be deteriorating or failing.

Magnetic separation and metal detection equipment is typically unobtrusive, and integrates easily into an existing process line. Selecting equipment depends on various factors, such as whether the other equipment in the facility is primarily constructed of stainless steel metal or ferrous metal. For example, if the majority of a plant’s equipment is stainless steel, metal detectors will be recommended over magnetic separators. Another factor is the retention of good product. Magnetic separators remove only the ferrous metal contamination, with little if any waste of product. Metal detectors use a reject mechanism that will reject the contaminant along with a small amount of good product. Many companies today install magnetic separators ahead of metal detectors to reduce the amount of good product rejected. Depending on the way material is being conveyed, pneumatic and gravity free-fall magnetic separators and metal detectors are both available for manufacturers to install.

Bunting is a leader in the food processing industry, providing the highest quality of magnetic separation and metal detection equipment. The company offers extensive custom design options for equipment, as well as comprehensive ongoing customer support. To learn more, please call 316-284-2020 or Contact Us.