Ideal Locations for Magnetic Separators and Metal Detectors in a Vegetable Processing Plant
Processed vegetables are a vital part of the food chain. Tens of thousands of bags of pre-cut carrots and freshly prepared kale are bought in supermarkets daily. Frozen vegetables have been very popular since Clarence Birdseye invented the quick freezing method in 1924. Also, often-unnoticed processed vegetables are present in many everyday food items such as tinned soup, baby food, sauces, and ready-made meals.
However, processing vegetables takes a great deal of care and attention as the products are often delicate and can be easily damaged.
As with all processed foods, there is always the risk of metal contamination. Metal can be introduced at various stages in the process. The design and positioning of the Magnetic Separator or Metal Detector has to also respect the delicate nature of the product.
Untreated Vegetables Feedstock
During the collection and transportation of the raw vegetables, there is always a high risk of metal contamination. This can be remove using a Plate Magnet. To avoid contact with the vegetables and eliminate the risk of damage, the Plate Magnet is suspended above the incline conveyor feeding the washer. Metal is attracted up onto the face of the Magnet and held until cleaned. This is ideal to remove larger metal items such as screws and nails.
The vegetables washing process frees dirt and other detritus including metal particles. Prior to the washed vegetables being fed into a drier, a Permanent Magnetic Pulley, replacing the standard head pulley of a conveyor, attracts and automatically removes any free metal before entering the drier. Again, there is no physical content between the Magnetic Separator and the vegetables. After drying, the vegetables are fed into a dicing machine.
Prior to Dicing
The blades on a dicing machine are delicate and expensive. Metal contamination can cause significant damage. To ensure that no metal is present, the dried vegetables are fed over the surface of a Plate Magnet. This enables higher levels of separation that when the Plate Magnet is suspended as the material is passing closer to the area of maximum magnetic strength. Any potential damage to the vegetables as they flow over the surface of the Plate Magnet is limited. Metal is captured and then held under the lip of a tapered step on the surface of the Magnet.
Smaller sized diced vegetables are often taken on a different route. They can be mixed with water, for ease of transportation, before being reintroduced into the process. Immediately after dicing, the smaller particles fall through a Quicktron Metal Detector to remove any small ferrous and non-ferrous metals (including any broken blades from the dicer). Water from the external source is passed through a Magnetic Liquid Filter Magnet to ensure that any rust or other ferrous metal contamination is not introduced into the process. The Undersized Vegetables are mixed with the water and then re-introduced into the process.
Final Packed Product
The final stage of weighing and packing includes 3 steps of Metal Removal and Detection. Prior to weighing, the processed vegetables are passed over the surface of a Plate Magnet to ensure that all ferrous metal contamination has been removed. After weighing, the vegetables fall under gravity through a Quicktron Metal Detector where any non-ferrous metals are removed. Finally, after packing, the finished packed batch of processed vegetables are passed through a tunnel-type Metron C02 Metal Detector as a final check prior to shipment.
This is a typical example of a Vegetable Processing Plant. However, each plant is unique and often a site visit is required to assess and recommend the best ways to ensure a metal-free end product.