Gearless Belt Conveyor Drives

When it comes to drive sizes exceeding 3500 kW per individual drive, there are no conventional drives with electric motors and helical bevel gears. Gearless drives, like those implemented for mine hoists in underground mining operations, allow the use of larger drive units and are increasingly being utilized to drive belt conveyors.

Introduction

Individual belt conveyors in hard rock mining operations all over the world nowadays extend over distances of more than 16 km and overcome height differences of up to 500 m, while normally achieving outputs of approx. 12000 t/h.

Such belt conveyors have had a significant impact on the development of individual components. Conveyor belts with strength of up to 7800 N/mm are actually in use today. In South American copper mines such belts are driven by electromechanical drives, consisting of electrical motors (wound rotor or squirrel cage motor) and helical bevel gears with a capacity of up to 3150 kW each.

The performance requirements of belt conveyors are redefined by lower ore contents and deeper deposits. Nowadays conveyors are routed through tunnel systems such that the maximum length available is required in order to reduce the number of underground transfer stations. This places higher demands on the quality and strength of the conveyor belts. Today, the St 10.000 with strength of 10000 N per Millimeter of belt width is available.

An alternative for continuously improving belt quality with ever-increasing drives located at both ends of the conveyor is to optimize the application of drive forces on the belt. Possible alternatives include:

• Belt on belt drives (TT-drives)
• Intermediate drives in the top strand and/or bottom strand
• Motorized carrying rollers [1]