Tech Insights · 2026-08-31
Permanent Magnetic Pulleys for Recovery
Rare-earth magnetic pulleys separate ferrous contamination at the discharge point without external power. We look at field gradient, belt-speed limits and typical recovery rates in mining and recycling.
The separation challenge
Nails, wire, rebar and grinder teeth travel with the conveyed material. If they reach crushers, screens or downstream belts they cause punctures, tears and equipment damage. Manual sorting at transfer points is inconsistent and hazardous. A magnetic pulley installed as the head pulley of a conveyor removes ferrous objects automatically as the belt discharges.
How it works
A permanent-magnet rotor inside a stainless-steel shell creates a magnetic field that penetrates the belt and lifts ferrous material to the top of the pulley arc. As the belt leaves the pulley, ferrous material is held against the belt and carried around past the natural discharge point; it then falls into a separate chute once the magnetic field is no longer sufficient. No power supply, coils or cooling are required.
Field gradient and belt speed
Recovery efficiency depends on magnetic field strength at the belt surface, field gradient, and belt speed. Rare-earth (NdFeB) circuits can maintain 1,800–2,500 gauss at the belt surface, sufficient for nails and small tramp at belt speeds up to 3 m/s. For coarse, weakly magnetic material or higher speeds, a deeper-reaching magnetic circuit and lower belt speed improve capture.
Recovery rates
In construction-demolition recycling, magnetic pulleys typically recover 85–95% of inbound ferrous by weight, depending on feed layering and belt speed. In mining, they are used primarily as a damage-prevention device rather than a concentrator, removing stray steel before it reaches the processing plant.
Integration tips
Position the magnetic pulley so the belt wraps at least 180°. Install a splitter plate that can be adjusted as the material burden changes. Keep the belt clean; heavy carry-back can shield tramp metal from the magnetic field. HBXM magnetic pulleys are built with sealed bearings and labyrinth seals for continuous outdoor duty.
References & Sources
- CEMA. Belt Conveyors for Bulk Materials, 7th ed. (2nd printing, 2020). Conveyor Equipment Manufacturers Association, 815 pp. ISBN 978-1891171-44-4.
- DIN 22101:2011-12. Continuous conveyors — Belt conveyors for loose bulk materials — Basis for calculation and dimensioning. DOI 10.31030/1821227.
- MagnetGlobal. Permanent Magnetic Drum Separators — technical data (98%+ iron-removal efficiency; surface field 3,000–10,000 Gauss).
- ISO 5048:1989. Continuous mechanical handling equipment — Belt conveyors with carrying idlers — Calculation of operating power and tensile forces.