Green conveyor systems driven by slow-speed gearless drives in the Czech Republic

Improve reliability……while simultaneously bring sustainable benefits to local communities and beyond

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Initially published in International Mining, April 2022

By Ulf Richter, Product manager, ABB linkedin
and Petr Kunz, Predeco linkedin 

Petr Kunz of Prodeco and ABB’s Ulf Richter explain how a new ‘green’ conveyor system featuring ABB slow-speed gearless drives is helping an operator in the Czech Republic reduce both noise and dust pollution, and its CO2 footprint, while maintaining the efficiency of materials handling operations.

Noise pollution, energy consumption and emissions of dust particles: three of the main challenges faced by mine operators as they look to optimize ore throughput, production and revenues, while also ensuring their operations comply with stringent local and global environmental legislation.

Conveyor systems are responsible for almost 80% of the energy consumption in mines, equating to many tonnes of CO2 emissions over the lifetime. Material on conveyors may cover distances of tens of kilometres and ascend steep gradients. To increase overall reliability, mine operators want fewer transfer stations between conveyors, which may in turn require wider and longer belts.

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The gearbox is an integral part of the drive system; if it fails, the system will be down for a considerable time. For this reason, low-speed gearless conveyor drives (GCD) are increasingly becoming the solution of choice for mining projects – particularly those that require high drive power. GCDs enable and help to boost the efficiency of high-capacity belt systems, while reducing energy usage, downtime and maintenance.

Gearboxes that are able to handle powers in excess of 3.5MW are maintenance-intensive and their productive lifetime is relatively short. ABB has addressed this issue by replacing the gearbox with robust, reliable control from variable speed drives running accurately performing, low-speed motors.

In this set-up, permanent magnet motors can produce the same torque power with 20–25% less motor current, thus reducing the size of frequency converters and motor feed cables. Because of their compactness they reach similar sizes as geared drives and so can replace them. Also, the number of motors needed on the drive system by combining the power demand in one permanent magnet motor can be reduced, resulting in less maintenance and energy consumption.

The multiple benefits of using low-speed gearless drives in conveyor systems when it comes to the environment and production efficiency were illustrated during a ground-breaking project involving the installation of a new 333m-long ‘green’ E1 conveyor system at the Bílina mine in the west of the Czech Republic.

As the project demonstrates, designing both mine conveyor and drive systems with environmental performance front of mind serves the dual purpose of helping operators maintain the efficiency of materials handling operations while simultaneously achieve their ambitious sustainability targets. It has brought benefits to both local communities through the reduction of noise and dust pollution as well as wider environmental benefits.

A customized drive solution

Central to this strategy was the mine operator's decision – following the successful completion of the first stage of the hauling relocation at the Bílina site – to install ABB slow-speed gearless drives developed specifically for the conveyor system at the site, and designed by Czech company Prodeco, the first time the concept has been used in long-distance crawler transport in the Czech Republic.

Gearless conveyor drives use a large, low-speed synchronous electric motor mounted on a pulley shaft designed to handle the high torque that is produced. The motor itself is controlled by a variable-speed drive and produces a shaft rotational speed typically in the range of 45–70rpm.

The ABB drive installed at Bílina contains a motor that turns at 48rpm, identical to the speed of the conveyer pulley, reducing energy consumption by an estimated 6–10%. In compliance with the request from Severočeské doly, ABB designed a customized motor that fitted the existing internal conveyance station. Adapting the new slow-speed gearless solution in size and performance to the original conventional drive means that, if necessary, in future it can be replaced in as little as 12 hours. In that way a step by step upgrade from geared to gearless would be possible.

Other advantages of using this drive include the elimination of mechanical gears causing wear and tear and thus the possibility of failure in proportion to the period of use. By eliminating the gearbox from the conventional drive, the new concept of the drive unit has resulted in a device with a low risk of failure (only motor bearings, and coolant), minimal maintenance requirements (relubrication of bearings once a year, checking the coolant once a month) and much lower ambient noise levels6

Better by design: limiting noise from conveyor systems

Another key project requisite was to limit noise from the conveyor. Drives containing gearboxes with multiple moving parts turning at 1,000rpm or higher run the risk of exceeding the EU noise emissions limit of 85dB(A) (A-weighted decibels). By running at less than 50rpm, the slow-speed drive restricts noise emissions from the drive unit to less than 73dB(A), negating the need for noise encapsulation (housing around the whole geared drive unit) or noise protection walls along the conveyor system.

Conscious of the impact the mine has on the surrounding environment – in particular the villages of Braňany and Mariánské Radčice less than 1km away – Severočeské doly has installed noise barriers and anti-dust measures, alongside greening the extraction and transport of the extracted placer material and mined lignite.

Noise levels from the conveyor system at the Bílina mine were also limited by placing the drive unit at the bottom of the steel structure (in conventional solutions it is located at the top) as well as by employing the following damping elements: impact bed, the soundproof design of the transport rollers, low-noise motor cooler, or by using more precise bearings. In addition, the middle parts of the mine conveyor route were specifically designed by Prodeco to reduce vibrations and resonances of the steel structure.

In terms of dust emissions, the full-circuit overfill seal minimizes take-off, while the overfill impact surfaces are lined around the inner perimeter with damping material in order to eliminate noise.

Environmental benefits for the local communities and beyond

Prodeco’s new ‘green’ E1 conveyor system, incorporating the bespoke low-speed gearless drive supplied by ABB, was delivered to the customer in Q1 2021, commissioned in Q2 2021, and has been running at Severočeské doly’s Bílina mine since July 2021.

In summary, the customer reports the following significant environmental benefits:

  • A significant reduction in the noise level from the drive (originally more than 85dB, guaranteed by the ABB manufacturer to be less than 73dB, and actually measured at 71 dB)
  • Dust reduction (achieved by a complete covering of the top, equipping the top at the return station of the downstream conveyor with a shock bed, etc.)
  • A reduction in overall conveyor ambient noise (more precise bearings, damped rollers, etc).
  • A reduction of energy consumption by between 6 and 10%.


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