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TN77 metal detectors prove popular in the US

TN77 metal detector

Bunting Magnetics seeing increase in sales of metal detectors to American quarry operators

TN77 metal detectors are proving popular with quarry operators in the US. The ‘Metal Detection’ branded equipment is used to identify tramp metal in conveyed aggregate and prevent damage to screens and crushers.

Metal Detection is part of the Bunting Magnetics group, one of the world’s leading designers and manufacturers of magnetic separators and metal detectors for the recycling, quarrying and mining industries.


The company’s wide range of metal separation and detection equipment is manufactured at its Master Magnets facility in Redditch, UK.

The TN77 metal detector is a tunnel-type device used widely in the quarrying, mining and recycling industries where the conveyed material is non-metallic or non-conductive.

The TN77 detects tramp iron and manganese steel, such as digger teeth, drill rods, crusher plates, bars, chains, nuts and bolts, which can cause significant damage to other processing equipment such as crushers, shredders, screens and conveyors.

In operation, the coil of the metal detector (surrounding the conveyor) continuously emits a magnetic field. Any tramp metal passing through the metal detector changes the magnetic field, which is registered by a control.

When a change in magnetic field is registered, the control processes the signal from the search coil and sends a second signal to other circuits which stop the conveyor, operate an audible and/or visual alarm, or initiate a rejection mechanism.

One useful optional extra is a marker, whereby either a flag or spray of ink is deposited when tramp metal is detected, making it easier to locate and remove the tramp metal.

Each TN77 metal detector installed in the US has a control unit housed in an IP52 wall-fixing cabinet, which is positioned either locally or remotely from the search coil of the detector.

The search coils of the TN77 metal detectors used in the US vary considerably, with several designed to suit customers’ specific requirements. The flat-pack design of the metal detector keeps shipping costs low and makes installation simple with no need to cut the conveyor belt.

‘Since Master Magnets were acquired by Bunting Magnetics, we have seen a significant increase in sales of metal detectors into the US,’ explained Metal Detection product manager Joe Cetti.

‘We have designed the TN77 with export markets in mind. The flat-pack design keeps shipping costs to a minimum whilst also making installation simple. This design is being used in quarries and mines in many remote locations, such as in Australia and Africa, and we anticipate continued growth in our sales to the US.’


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