Mr Jason Willis

In belt conveying, pulley lagging is the source of necessary friction for power transfer. The constant need to transfer bulk materials at higher rates over longer distances has resulted in a requirement to transfer more power through the drive pulley. Despite these changes, conveyor design standards (ISO5048, DIN22101, CEMA) continue to utilise the over-simplified rope friction model (Euler's equation) to determine power transfer limits. The primary, well-known limitation of this model lies in the assumption of a constant coefficient of friction around the lagging surface that is fully developed. Recent research has demonstrated that the friction between the lagging and belt bottom cover varies with factors such as wrap pressure and speed, resulting in a misrepresentation of the behaviour in the interphase and, consequently, inadequate design of the belt conveyor system.

With recent advancements in conveying technologies, conveyors are required to achieve greater lifts, longer conveying distances and higher throughputs. As such, drive stations continue to increase in size, with gearless drive stations in excess of 10 MW in existence. A significant amount of research has been conducted into the design and optimization of these systems, however, the use of standard methodologies to quantify drive friction is a known limitation that remains. Currently, design standards use Euler's classical 'rope friction' equation to determine drive limitations, with this method failing to account for a variable friction coefficient around the drive pulley. Due to this, the calculated drive is conservative and reaches the limit of efficacy with high-capacity conveyors, due to the high belt tensions required, and the necessary overdesign in structure. This paper investigates the frictional behaviour between a belt conveyor and pulley lagging materials and presents test results demonstrating how the friction coefficient varies with changing load and slip velocity. This improved understanding of the frictional behaviour between the conveyor and drive pulley lagging will further the design capabilities of high-capacity conveyor systems.