The Role of Wing-Type Pulleys and Their Alternatives
Wing-type pulleys are commonly installed to reduce the risk of belt damage caused by material lumps getting stuck between the belt and the pulley. These pulleys feature vanes reminiscent of steamboat paddle wheels. This design allows material that would otherwise cause blockages with solid pulleys to pass through the pulley face. Crossbars on the pulley include inclined, valley-shaped recesses that prevent fine or granular material from getting trapped between the tail pulley and the return belt. These valleys enable self-cleaning by minimizing material accumulation, and the pulley's rotation throws any remaining material off its surface.
In instances where a conveyor may spill cargo onto the return belt, wing pulleys effectively remove spillage without damaging the belt, although optimal protection involves sealing the belt at the load zone and using a pulley-protection plow. 
Wing-type pulleys are also used in gravity take-ups, offering similar benefits and limitations.
Despite their intended design, wing-type tail pulleys still experience buildup and entrapment issues, often failing to provide the desired protection. They perform best on slow-moving belts where frequent cleaning and sealing are less critical. Larger material lumps can lodge in the pulley's wings, potentially causing the damage these pulleys are designed to prevent.
Using wing-type tail pulleys with a bend radius below the manufacturer's recommended minimum can damage the conveyor belt's carcass.
The main drawback of wing pulleys is the oscillating action they introduce to the belt path, destabilizing it and adversely affecting belt-sealing systems. This can be counterproductive when attempting to design stable transfer points to minimize fugitive material. The Conveyor Equipment Manufacturers Association (CEMA) advises against using wing pulleys on belts traveling over 225 meters per second (450 ft/min).
A superior alternative to conventional winged tail pulleys is the spiral-wrapped tail pulley. These pulleys feature an additional steel strip spirally wrapped around the pulley circumference, covering the wings. This design maintains the self-cleaning function while eliminating the belt's bounce.
Spiral-wrapped wing pulleys are sometimes installed as original equipment on new conveyor systems. Existing wing pulleys can be upgraded by welding narrow, 50 to 75 mm (2 to 3 in.) steel strips around the outer edge of the wings.
To prevent material buildup on tail pulleys effectively, using a solid flat steel pulley with a cleaning device positioned directly in front of it is recommended. This diagonal or V-type plow should be placed just before the tail pulley on the non-carrying side of the belt to remove any fugitive material that may accumulate inside the belt.