BESTECH Delivers New Ventilation-on-Demand System for Underground Mine

Background

Without ventilation, the air in a mine is filled with dangerous contaminants. Miners may work at depths of a mile or more underground where contaminants such as carbon monoxide, as well as the dust created from the mining cycle exist. Worker safety is essential to any mine’s operation and success, but also presents challenges.

Mining companies must provide fresh air to the work force to ensure a safe working environment. This airflow is continuously removing and diluting contaminants. The cost of ventilating mines is high and rising even higher as energy prices increase and mines expand in depth. Approximately 50 percent of a typical mine’s energy costs are associated with ventilation.

Many hard-rock mines contain dozens of main ventilation fans and hundreds of auxiliary ones. Both types are usually controlled manually and operated continuously at maximum speed, or peak capacity, to keep
air flowing through each part of the mine 24 hours a day. Unfortunately, keeping all those fans running at maximum speeds – even during non-peak demand periods – wastes precious energy.

Ventilation-on-Demand (VOD) systems operate according to the production requirements of a mine, automatically adjusting to peak and non-peak demand periods. Air flows can be directed where and when they are needed for more energy-efficient operation. For example, a diesel loader entering a particular area of a mine may require 100 percent air volume, but a drill entering a different area of the mine, or in the same area at a different time, may require only 20 percent air volume. As such, fan speeds can be set so that full performance requirements are met at 5 to 10 percent of full motor speed, which reduces power consumption to 70 to 90 percent, compared to fans running at maximum speed. Lower operating speeds also translate into longer motor life, ultimately reducing maintenance and operating costs.

BESTECH, a leading provider of system automation to the mining industry in Canada, recently created a new approach to help mining companies more efficiently manage their processes, equipment and energy usage in a safe manner. NRG1-ECO™ (Energy Consumption Optimisation) combines hardware and software to manage many pieces of automated equipment in a mine.

“When combined with a VOD module, mining companies can realize significant energy savings,” said Paul Lalonde, product developer – Automation, BESTECH. “The hardware and software system also can dramatically reduce a mine’s greenhouse gas emissions, while increasing its productivity and air quality.”

Challenge

When BESTECH developed the NRG1-ECO™ technology, it formed a consortium of industry experts and organisations to establish best practices and standards. The consortium members include organisations such as the Centre for Mining Excellence, and mining giants Vale and Xstrata Nickel.

Vale asked BESTECH to tailor a VOD system for its Coleman Mine, which already included some variable frequency drives (VFDs) in its underground equipment. BESTECH engineers faced a new challenge – they needed skid-mounted VFDs that could be easily confi gured and installed on mine fans and seamlessly integrated with the BESTECH NRG1-ECO™ system.

BESTECH and Vale engineers evaluated VFDs from multiple suppliers and selected Rockwell Automation based on the ease of integration into the existing control system and the seamless communication between the controllers, the VFDs and NRG1-ECO™. System reliability was also a critical issue, as it is for any mine, so that ventilation is available to miners 24/7. The BESTECH engineers found that the Allen-Bradley VFDs from Rockwell Automation were reliable and right for the job.

Solutions

To optimise air flow throughout the mine, the Coleman Mine had an existing system of regulators on each mine level with fresh air fans. On one level of the mine, auxiliary fans are controlled by Allen-Bradley PowerFlex 700H 600-volt VFDs on skids underground. The PowerFlex VFDs significantly reduce the energy used during fan operation by precisely regulating motor speed, and maintaining torque levels to match the needs of the load. The VFDs also reduce the mechanical stress on the motors by providing “soft-start” capability. After the installation of NRG1-ECO™, Vale installed Allen-Bradley PowerFlex 7000 medium-voltage VFDs mounted in a portable e-house on the surface of the mine to help reduce energy use and ventilation costs.

The PowerFlex drives allow operators to vary the speed of fan motors electrically rather than mechanically, allowing greater flexibility. Lacking a drive, the fan motors would run at full speed continuously regardless of varying demands for air flow, resulting in a significant waste of energy.

A series of air-flow meters, air temperature sensors and carbon monoxide detectors also were installed as part of the new system. On one level in the mine, fans, regulators and air-flow sensors are controlled by Allen-Bradley Bulletin 1747 SLC 5/05 programmable logic controllers (PLC) and Allen-Bradley MicroLogix 1400 PLCs from Rockwell Automation. The sensors seamlessly connect with Allen-Bradley CompactLogix L35E programmable automation controllers (PAC) from Rockwell Automation to allow system wide control. The EtherNet/IP network connects fans, regulators and sensors to the controllers to allow seamless communication on a common network infrastructure.

Allen-Bradley Stratix 8000™, Stratix 6000™ and Stratix 2000™ managed and unmanaged Ethernet switches simplify the deployment of EtherNet/IP in the mine. Stratix 8000 switches use a Cisco Catalyst Operating System, feature set, and user interface to provide a familiar environment for IT professionals. Stratix 6000 switches use a CIP interface to the Rockwell Automation Integrated Architecture to help ease deployment of EtherNet/IP in the mine. Stratix 2000 switches do not require confi guration and use simple cable connections for easy connection to the controllers. They also segment the EtherNet/IP network and direct network traffic more efficiently than repeating hubs.

The switches use configuration screens in the programming software via an add-on profile to ease integration and diagnostics of networked devices. Using FactoryTalk® View human-machine interface (HMI) software faceplates as part of the system, operators can view diagnostic data to easily access information about system activity and quickly identify and troubleshoot problems.

Rockwell Software® RSLogix™ 5000 programming software minimised system development time and provided a single programming environment for the CompactLogix L35E controllers, soft starters and VFDs. Engineers used Rockwell Software® RSLogix 500 programming software to program the MicroLogix 1400 controllers and SLC 5/05 PLCs. The Integrated Architecture from Rockwell Automation provides multidiscipline functionality on a single EtherNet/IP network, which helps converge control, visualisation and decision support throughout the entire mine.

BESTECH engineers also used the Integrated Architecture Accelerator Toolkit from Rockwell Automation to help simplify installation and reduce the overall time to design, develop and deliver the solution. The tools help engineers select components, develop drawings, write code, lay out HMI screens, and troubleshoot and start up machines.

During system installation, operators pre-set the default parameters for the air flow regulation system using the FactoryTalk View software in the surface control room. Each entrance into the mine includes its own display to show current air flow, temperature and carbon monoxide levels. This air quality data is readily available and easily visible at each level of the mine to notify workers of potentially dangerous conditions, such as high carbon monoxide levels and/or minimum air flow, before entering.

Results

After implementing the VOD system, the mine has realised greater energy savings than the originally anticipated estimate of 30 percent. The VOD system is also helping the mine reduce its carbon footprint by 1,577 kilograms of carbon monoxide for every kilowatt reduction in energy use. “Taken all together, these numbers illustrate signifi cant cost savings for the Coleman Mine,” Lalonde said. “We expect to see a savings of approximately 1.4 million dollars in energy costs per year, and the VOD system contributes greatly to this overall savings. The VOD system is also helping to save about three million kilowatt hours, or 540 tons of carbon monoxide per year.”

The new BESTECH technology is attracting the attention of other mining giants. By working with Rockwell Automation, BESTECH can integrate the NRG1-ECO™ with any mine’s existing technology to help save costs without compromising worker safety. The NRG1-ECO™ integrates with the Coleman Mine’s tracking system, which helps mine operators detect the location of personnel in an emergency situation through tagging. Tagging also allows mine operators to ramp down or turn off the fans if no one is detected in a certain area of the mine, decreasing energy consumption but also helping keep workers safe. Safety engineers can also use the system to understand the air quality at any given time using real-time data.