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Choosing the Right Equipment for Removing Metal Contamination

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Metal contamination in powder and bulk solids materials can pose devastating consequences for consumers and manufacturers.

Metal contamination in powder and bulk solids materials can pose devastating consequences for consumers and manufacturers. When handling powder and bulk solids, it is of great importance to not only ensure metal contamination is removed, but also to ensure that you are using the correct equipment to do so. Magnetic separation and metal detection equipment provide reliable, efficient solutions for the removal of metal contamination, but when selecting magnetic separation or metal detection equipment, it must be selected with the unique needs of the material being handled in mind.

There is a broad range of materials classified under the category of powder and bulk solids, spanning across an equally broad range of industries. These industries include building materials, food, plastics, rubber, wood, paper, chemical, grain, and more. Materials that can be conveyed at any given time include grain, nuts, sugar, starches, flour, food ingredients, minerals, pigments, plastic resin, and recycled plastics. These materials will have different consistencies, different flow rates, and different levels of abrasiveness. Additionally, certain unique factors, such as food safety regulations and explosionproof ratings, must also be considered when handling certain materials.

In general, all materials share similar risks regarding where, when, and how metal contamination can enter the product stream. Metal contamination can first be present in the raw materials being conveyed. For example, a shipment of grain or other mechanically harvested produce may contain metal contamination such as wire or broken pieces of tools. If this initial source of metal contamination is allowed to remain in the product stream, it will go on to cause damage to airlocks or processing equipment in your facility, which leads to more metal contamination entering your product stream. To combat this initial metal contamination, it is recommended that magnetic separation and metal detection equipment be installed in the first line of defense in your facility.

To minimize rates of contamination present in the raw materials they receive, manufacturers must thoroughly review their vendors. By identifying problematic suppliers or ingredients, manufacturers have the opportunity to address contamination issues and either work with problematic suppliers to resolve these issues or select new vendors altogether. However, even when working under optimal circumstances, some amount of metal contamination will always be present in raw materials. To combat this contamination, it is recommended that manufacturers implement preventative measures against metal contamination as the very first step in their manufacturing process. At the very least, all material coming into the plant should pass through one round of magnetic separation and metal detection equipment in order to prevent tramp metal contamination in raw materials from entering your greater manufacturing system.

Metal contamination may also enter your system as a result of degradation of your equipment over time. If metal contamination is present in raw material and allowed to travel throughout the production facility, small pieces of tramp metal can scrape and grind against other metal equipment, causing small metal shavings and eventually larger pieces of metal to break off and enter the product flow. This creates a chain reaction—as more metal begins to enter the product stream, equipment later down the production line is damaged until ultimately all of the equipment in your facility is shedding metal and creating a constant stream of contamination entering your product flow. By placing magnetic separation and metal detection equipment at various key points in your production line, you are able to isolate the point where the damaged equipment is and prevent contamination further down the line.

It is of great importance to consistently monitor the equipment in your facility for wear and tear. By constantly checking the integrity of your equipment, you are able to monitor the status of more worn-out equipment and make repairs and replacements where necessary. Equipment such as screens and sifters should be monitored frequently due to the risk for wear or breakage that can cause more mental contamination to enter the product stream if not properly maintained. Performing routine equipment maintenance is key to ensuring a basic level of quality assurance throughout your production environment.

When selecting the ideal piece of magnetic separation or metal detection equipment to be implemented in a facility, there are several factors to consider. Manufacturers must consider the flow rate of the material they are handling, including the bulk density of the product and how much material they will be running through their system in a given time frame. Manufacturers must also take their product’s nature and characteristics into account—for example, if it is a free-flowing material, an abrasive material, or a material that is prone to bridging. Manufacturers must also identify their goal with magnetic separation and metal detection equipment. For example, with magnetic separation equipment, they must identify if they are seeking to capture large pieces of tramp metal or smaller fines. With metal detectors, manufacturers need to consider not only the size of the material they are trying to remove, but also the level of sensitivity they will require in a metal detector.

Magnetic separation and metal detection equipment is available for various types of conveying systems, including gravity free-flow systems, pneumatic conveying, and belted conveying. When using magnetic separation and metal detection equipment in pressurized lines, they must be in a dilute phase. Typical installations can be in both vertical and horizontal lines. Variables to consider will be line pressure, product speed, and line size for a successful installation. For gravity installations, there are different types of magnet configurations in magnetic separation equipment available to overcome common material flow problems, such as bridging, clumping, and line clogs. When considering a belted conveying belt type, non-ferrous conveyor sections, burden, and product depth are among the variables to consider.

Metal contamination can start off with small particles, but these small particles can lead to very large problems. If metal contamination is allowed to remain in your product flow, your product purity will be compromised, your brand reputation may suffer, and the other equipment in your facility can go on to be severely damaged. Equipment damage is of a particularly high concern, as it can lead to expensive repairs in addition to extremely costly downtime. Because metal contamination is such a pervasive, constant threat, magnetic separation and metal detection equipment is essential for all manufacturers working with powder and bulk solids across various industries.

Veronica Zuccarello is technical copywriter, Bunting (Newton, KS). For more information, email vzuccarello@buntingmagnetics.com, call 316-284-2020 or visit buntingmagnetics.com.

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