Gearless Conveyor Drives: boosting ore throughput while reducing energy usage, CO₂ and noise emissions

Gearless conveyor drives (GCDs) are now the preferred solution in many mining projects, particularly those that require high drive power, helping to boost the efficiency of higher-capacity belt systems for greater ore throughput and reduced energy usage, equipment downtime and maintenance costs.

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Chiquicamata Site Overview

First published in in Global Mining Review May/June 2021

In the high-power regime, conventional conveyor drives face multiple challenges, mostly associated with the gearbox. Building a gearbox that can handle powers above 3.5MW is a complex process; once in operation they are maintenance intensive, and their productive lifetime is relatively short. 

A GCD, in contrast, uses a large, low-speed synchronous electric motor driving directly onto the pulley shaft designed to handle the high torque produced by such motors. The motor is controlled by a variable-speed drive to produce a shaft rotational speed typically in the range of 50–70rpm. There are usually several drive modules in a drive station and there can be multiple drive stations on the conveyor.

Existing GCDs vary from 2.5–7MW, with a total connected power of 5–20MW. GCDs are also robust, require minimal maintenance, and can boost the energy efficiency of high-power systems by 3–8 percent.

GCDs developed by ABB offer mining operators these benefits and are currently proving their worth at one of the most challenging mining projects of all time at the Chuquicamata mine in Chile.

By Ulf Richter linkedin
Global Product Manager Gearless Conveyor Drives, ABB

ABB GCDs: resetting the parameters for power and control

In September 2020, 2,850m above sea level in the high desert of the Antofagasta region in northern Chile, the world’s most powerful belt conveyor system, 13km long, was brought online, connecting underground operations at the Codelco-owned open-pit copper mine directly to the concentrator.

Two 20MW TAKRAF conveyors each lift 11,000 tonnes per hour (tph) of ore more than 600 metres to reach the surface of the underground mine. The total lift is about 1.3km and then the ore is fed to a 15MW overland conveyor.

GCDs were the only economically feasible way to provide enough power to run the 20MW conveyors. The limit for an input pinion gearbox on a conveyor is 3-4MW, so the belt system at Chuquicamata would have either required 8 motors driving into a gearbox with an output shaft or multiple conveyors with lower power ratings and multiple transfer stations. Either scenario requires substantially more materials, space and infrastructure to deliver the requisite power. GCDs were therefore the simplest way to achieve the production output that the customer wanted, with the added benefit of reduced maintenance and significant efficiency gains.

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ABB, in partnership with TAKRAF, successfully commissioned this most powerful GCD system in the world, comprising a total of 11 drives with synchronous motors running at low speeds of 50-60rpm, and with a rated power of 5MW each, resulting in a motor shaft torque of roughly 900kNm. The total installed drive power for the entire system, including multiple feeder conveyors, is 58MW.

GCDs were the only economically feasible way to provide enough power to run the 20MW conveyors.

Volume control: reducing CO₂ and noise emissions using GCDs

At Chuquicamata, switching from open-pit with truck/shovel operations to underground operations using the TAKRAF conveyor with ABB gearless drives will help mine owner Codelco save roughly 130 million litres of gasoline per year by eliminating the need for 120 large-haul trucks, bringing the CO₂ emissions from the mine from 340,000t per annum to 100,000t, a saving of approximately 66 percent.

In Europe, meanwhile, ABB is partnering with a mine in the Czech Republic to reduce emissions of a different kind. By upgrading shaft mounted geared drives on an existing conveyor system with GCDs powered by synchronous permanent magnet motors, the mine owner is able to meet stringent EU noise emission limits, as well as prevent frequent motor bearing failing due to vibration issues.

Drives containing gearboxes with multiple moving parts turning at 1,000rpm or higher can be very loud, and run the risk of exceeding the EU noise emissions limit of 85dB(A) (A-weighted decibels).

Using GCDs at around 50rpm, ABB restricts noise emissions from the drive unit to less than 75dBA, giving the mine all the benefits of gearless drives while negating the need for noise encapsulation (housing around the whole geared drive unit) or noise protection walls along the conveyor system.

Wide-ranging benefits from installation of TAKRAF conveyors with ABB gearless drives

Energy efficiency and monitoring with ABB Ability™ 800xA

Unlike conventional drive pulleys with gears and motors, the 5MW motors at Chuquicamata are directly coupled to the drive pulley and employed in the conveyor systems with four 5MW motors, a total of 20MW.

The GCD solution is highly integrated as part of the drive pulley. A single bearing solution for the motor with a special membrane coupling was designed and patented by TAKRAF.

ABB’s Mining Conveyor Control Program is a software package developed by ABB for conveyor drives control. It has been designed to run directly on the control board of its medium voltage (MV) or low voltage (LV) variable-speed drives. The software is specifically configured for conveyor applications, allowing for setting (by parameter) of the essential conveyor drives control functions. Used at Chuquicamata, it ensures smooth belt operation and safe synchronization between high-power motors and high-power hydraulic brakes, necessary for secure operation of steep uphill conveyors – the GCD technology meets the high demands of the massive conveyor system for accurate starting with no roll-back and precise load-sharing control.

ABB liquid-cooled MV voltage-source frequency converters, together with the large synchronous motors, deliver a decrease in active and reactive power consumption for high energy efficiency.

A system that transports cooling liquid several kilometres out of the tunnel was installed to manage significant heat losses from the motors – in excess of 1MW – in the subterranean environment.

A complete solution including GCDs, data-to-insight process and Mining Conveyor Control Program, a software specifically configured for conveyor applications

The ABB/TAKRAF solution at Chuquicamata is connected to ABB Ability™ System 800xA, ABB's control system for efficient data acquisition, equipment assessment and process optimization, including condition monitoring of the pulley bearings. System 800xA monitors and collects data from multiple sensors embedded in the motor drive system, monitoring for failures and identifying maintenance needs.

Incredibly moving: overcoming logistical challenges at Chuquicamata

The Chuquicamata project also constituted a major logistical undertaking. With 50 percent of the conveyor system located underground, installing large equipment such as five containerized e-rooms housing electrification, control and instrumentation equipment, and the drive station was major challenge, particularly in the remote, dry and dusty conditions that typify the high desert in northern Chile.

ABB synchronous motors are factory assembled and tested as complete units, including the base frame, which was shipped and installed in one piece. A novel embedding concept jointly developed by TAKRAF and ABB enabled the GCD motors to be installed and aligned in a single day, a major benefit compared with existing cantilevered GCD solutions that can take two days or more to install.

The motors can also be mechanically disconnected from the drive pulley quickly, so that operations continue if drive failure occurs. The motor air gap is fully under control and can be re-adjusted easily. In total, commissioning of the drives took just 14 days, a new record. The underground project is expected to extend operations at Chuquicamata for the next 40 years.

In addition, ABB provided an installation supervisor and 100 percent perfect documentation of the whole drive system so that a third-party company can install it without support, as per customer requirements.

Breathe easy with ventilation on demand

ABB has also installed its ventilation on demand (VoD) solution, ABB Ability™ Ventilation Optimizer, at Chuquicamata to provide clean air to workers in line with the strict HSE requirements.

Ventilation systems can account for 50 percent of energy use in underground mines, yet production may only be concentrated in 20 percent of a facility at any one time. By distributing clean air only where and when people or machines are working, Ventilation Optimizer streamlines ventilation systems and reduces energy costs, while at the same time ensuring a safe working environment for personnel.

It does this by employing sensors throughout the mine that transmit real-time information regarding air quality, diesel vehicle usage and personnel to an ABB Ability™ System 800xA operator for analysis. Ventilation Optimizer then operates equipment according to actual ventilation demands dynamically calculated from mine production schedules and events, and event equipment status and location.

The VoD solution has three implementation levels, the most advanced of which uses an algorithm, sensor feedback and advanced multivariable control technology to run all ventilation fans in optimal mode, distributing the air supply more efficiently and minimizing energy consumption in real time. By controlling mine ventilation in this manner, annual energy savings of up to 50 percent are possible.

ABB sees Ventilation Optimizer as part of the transition on the journey towards the all-electric mines of the future by helping to reduce nitrous oxide emissions from diesel and diesel-electric hybrid trucks.

An innovative ventilation-on-demand solution to help ensure the highest levels of wellness for mine workers through supply of clean air

Forward thinking: future GCD and digital technologies

With global demand for medium power conveyors from 3-10MW for use in major projects such as Chuquicamata set to increase, ABB has developed gearless conveyor drives for medium power to ensure mining customers continue to reduce the cost per ton of production and stay competitive.

Meanwhile, innovations in the sphere of augmented reality, now allow ABB experts to see the same view as an on-site service engineer in real time, allowing them to provide remote support, which is of value in the wake of Covid-19 travel restrictions.

ABB’s augmented reality collaboration application, Visual Remote Support, digitalizes the field operator experience and vastly improves interaction between field and control room operations. Operatives will be able to access hands-free, real-time data related to plant assets, processes or procedures using industrial tablets, smartphones and Microsoft HoloLens glasses, not only increasing real-time collaboration, but also enabling immediate data entry from the user interface in the field.

Similarly, ABB’s newer solutions use advanced data analytics, AI tools and machine learning to correlate and analyse signals from critical mining machinery such as GCDs and motors. Not only does this equate to better online support from off-site experts, it has the potential to remove personnel from risky environments – while all the time maintaining mine production and maximising profits.

Enabling remote visibility and control with ABB experts seeing on-site service engineer views in real time, allowing them to provide support virtually

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