October 2013

Proximity detection takes root underground

A push by regulators and operators is driving the growth of underground proximity detection tools

By Janice Leuschen

Technology developers working to improve personnel safety have struggled with the constraints of the underground mining environment. A steady effort by regulators and miners, however, has helped the industry work through these difficulties and drive the growth of underground proximity detection tools.

Thirty-seven fatalities in 30 years that involved miners being crushed by a continuous mining machine in underground coal mines in the United States were just too many deaths for the regulatory body tasked with mine safety.

“It seemed to us there should be a way of keeping the miners away from those machines and avoiding those crushing accidents.” says David Chirdon, new technology program manager of the Mining Safety and Health Administration (MSHA) with the U.S. Department of Labour. In the late 1990s, Chirdon took on the task of finding a solution.

“We found some technology called proximity detection systems being developed in other industries that we thought could be leveraged for use in the mining industry,” Chirdon says.

A difficult environment

However, adapting technology used in surface mining or on construction sites proved challenging. Global positioning satellites have unlocked enormous opportunities for surface operations but are useless underground. “It’s a very different application working in much more confined spaces with heavy machinery, plus the equipment has to be explosion-proof – which is a significant design constraint,” Chirdon says.

In 2002, MSHA partnered with system design and manufacturer Nautilus International in Burnaby B.C., with the cooperation of a number of mining companies, and began developing such a proximity detection system for continuous mining machines.

“We had many failed underground field tests and were repeatedly going back to the drawing board to redesign,” Chirdon says. The original system was developed for diesel machines, he explains. “When the Nautilus system was adapted to an electrical machine, we experienced ‘parasitic coupling,’ which was the electromagnetic signal for the proximity detection system coupling onto the machine’s electrical power cable that distorted the signals resulting in false distance indications.”

The system includes antennas on the machine, which create a magnetic field around it. A device, worn by the miner, measures the strength of the field and communicates that information by radio signal to a microprocessor on the machine. Depending on the distance from the miner to the machine, the system will respond by either turning on a warning light or stopping the machine.

The first field test of the Coal Buddy system was in 2003. “The first successful field test, where the system actually performed as we had intended and was designed to meet the explosion proof requirements, obtaining MSHA approval, was in 2006.”

Growing coverage

Today, there are a number of MSHA-approved systems, and the application of the technology is expanding. Alliance Coal Company, which owns the electronics company Matrix Design Group, has installed proximity detection on all of the company’s 78 continuous mining machines. Earlier this summer, Matrix released a second-generation version of the technology called IntelliZone, which expands the proximity detection beyond the continuous mining machines to other mobile haulage machines.

The mining industry in South Africa has also been active in developing this technology, says Mike Berube, COO of Strata Worldwide. In November 2010, Strata acquired Frederick Mining Controls (FMC) that developed personnel proximity detection and vehicle collision avoidance products.

Strata’s HazardAvert technology is focused on near-field (30 metres or closer) or slow-speed (five miles per hour and less) objects and can be applied to a range of underground vehicles. It also relies on electromagnetics to alert persons on the ground as well as vehicle operators of a potentially dangerous encounter.

Dowling, Ontario-based Hard-Line Solutions recently released a proximity detection system called Prox, which is integrated with its Muckmaster Radio Remote Control System for LHD vehicles. “We have several customers who are using our remote control systems, and they wanted a system that would ensure that the operator didn’t get too close to the piece of equipment he was operating,” says Ryan Siggelkow, vice-president of Hard-Line Solutions.

Hard-line’s product also uses magnetic resonance that generates a magnetic field around the LHD. A receiver in the unit and the radio remote control interfaces with the magnetic field and this relationship generates two zones: a kill zone and a warning zone. The sizes of each zone can be adjusted.

“If the operator gets into the warning zone, the machines’ lights will start flashing and horns will go off,” says Max Gray, director of sales of North America and global marketing for Hard-Line. “He is getting into an area he should probably think about getting out of. The red zone will either shut down the machine or it will cease to operate under his control.”

Systems of the future

Chirdon says low-frequency electromagnetic systems are preferred in the underground mining application, because the low-frequency nature of the signal can penetrate coal and hard rock and eliminate blind spots around that machine.“The problem,” says Chirdon, “is it is limited to close ranges. When you get into faster moving machines it might not be as effective as some other technologies.”

Radio frequency identification (RFID) systems use higher frequency signals and may be more effective at greater speeds. “That’s something that I think we will see eventually in the U.S.,” says Chirdon.

Currently, a system created by Becker Mining Systems uses a suite of technologies to extend the reach of its collision avoidance system. Chirdon saw the tool in action at an Xstrata mine in South Africa. “It had the very low-frequency electromagnetic system for the slow moving machines and for the close distances and the higher-frequency RFID systems for the larger distances,” he goes on to say. “It also had a radar system to detect objects. All of these technologies were communicating with each other. I think ultimately that’s where we could get the most effective system, but this is a technology that is still in its infancy.”

Regulation approaching

To spark greater uptake of the technology among coal miners, Chirdon explains the regulatory body “proposed a rule to require proximity detection on continuous mining machines in August 2011. That activity really got the attention of the mining industry and that’s when we started to see them actually making the effort to start installing these systems on these machines.

“Additionally, the [MSHA] regulatory agenda says that we are planning to publish a second proposed rule in November 2013 that would require proximity detection systems on other mobile machines in underground mines.”

In Canada, regulators have not been as active in pushing adoption of the technology. Nevertheless, Glenn Staskus, a mining specialist with Ontario’s Ministry of Labour, confirmed that the provincial ministry is in the midst of its own survey of proximity detection solutions for both underground and surface mines.

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