Remove Tramp Metal from Aggregate Conveyors with Metal Detectors and Magnetic Separators

During the process of quarrying aggregate and mining ore, tramp metal is frequently introduced into the mix alongside valuable raw materials. It is essential that this tramp metal is effectively detected and removed in order to protect crushers, screens, and conveyors from costly damage and the downtime that results. Additionally, if tramp metal is allowed to remain in a material stream, the purity of the raw material is compromised and its value suffers as a result. Fortunately, magnetic separators and metal detectors excel at removing tramp metal from aggregate and mining product streams.

The design of a metal detector or magnetic separator depends heavily on the application it is being used in. It is also important to fully understand the nature of the tramp metal entering the product stream, evaluating the traits of different types of tramp metal such as drill rods, digger teeth, chains, crusher plates, nuts, bolts, bars, or even fine tramp metals in sand.

Metal Detection

All metal detectors operate based on the same fundamental principle. When electricity passes through a coil contained within a metal detector, a magnetic field or frequency is produced. This magnetic field remains stable unless a metal particle is introduced and disrupts it. Then, this subsequent change in the magnetic field triggers a control in the metal detector so that the section of product containing the source of contamination is located and/or removed from the greater process flow.

In quarry and mine environments, metal detectors are usually installed over a conveyor belt. When tramp metal comes into the metal detector’s magnetic field, the control activates and either stops the conveyor entirely or diverts contaminated product away from the main product flow.

Bunting’s TN77 Series conveyor belt metal detector features a tunnel-style design, and has been engineered specifically to suit the needs of aggregate and mining applications. It is easy to install and can be purchased in several different standard sizes, as well as custom designed to suit a customer’s specific requirements. The TN77 is able to easily detect tramp iron and low-grade manganese steel, but ignores non-magnetic copper alloy conveyor belt fasteners. Additionally, its control panel is able to indicate if one or two pieces of tramp metal have been detected.

Magnetic Separators

Metal detectors are capable of detecting all sources of tramp metal contamination. Meanwhile, magnetic separators are designed to attract and remove exclusively ferrous tramp metal. This is not a weakness, but a unique strength. Magnetic separators and metal detectors are frequently used together to achieve optimum removal of tramp metal. A magnetic separator will be used first to remove ferrous tramp metal, which often makes up a large amount of the total tramp metal present. Then, a metal detector is used to catch any ferrous material that may have been trapped in the flow of materials or manganese wear items that have broken off of equipment.

The two magnetic separator designs most commonly used in the aggregate and mining industries include the crossbelt magnet and pulley magnet.

Crossbelt Magnet

Crossbelt magnets (also known as overband magnets) use permanent magnets or an electromagnetic coil to generate a powerful magnetic field. Crossbelt magnets are suspended over conveyors, projecting the magnetic field downward into the material being conveyed. As ferrous tramp metal passes into the magnetic field, it is attracted upwards towards the crossbelt magnet and removed from the burden of material.

Permanent crossbelt magnets are well known as an industry standard, and are frequently found in quarries as well as on mobile screens and crushes. For heavier-duty applications where conveyors are transporting high tonnages of material, electro crossbelt magnets may be utilized instead due to their ability to produce deeper, stronger magnetic fields. Both the permanent and electromagnetic crossbelt options can be custom designed to suit your application and can be supplied both with or without self-cleaning gear.

Pulley Magnet

A permanent pulley magnet replaces a conveyor’s standard head pulley. Permanent pulley magnets project a magnetic field up through the conveyor, and continuously attract any tramp metal in the conveyed material. The magnetic field holds the tramp metal to the conveyor belt, where it is then automatically removed once the conveyor belt leaves the pulley’s surface. Bunting offers “Take Off Rails” that can extend the return of this tramp metal even further on the return section of conveyor belts.

Good Protection Means Less Downtime

By installing the optimum magnetic separators and metal detectors, you can ensure the purity of your product and the protection of your other processing equipment. With Bunting magnetic separators and metal detectors, you are able to avoid damage to crushers, screens, and conveyors that is otherwise inconvenient, time-consuming, and costly in terms of downtime and missed production.

For more information about magnetic separators and metal detectors for the aggregate, mining, and mineral industries, Contact us Today.