The burdens borne by underground mine communication networks have grown in the last decade, as monitoring and remote control functions generate new potential data streams for every piece of mobile and stationary equipment. At the same time, a series of underground coal mine accidents in the United States in 2006 opened a flood of public research funding into fail-safe communication systems. The result has been an incremental improvement in the day-to-day technologies used and a big boost for less familiar ideas.
Shocked by the deaths of miners who might have been saved had they been located earlier, the U.S. Congress, with the development of the Mine Improvement and New Emergency Response (MINER) Act, adopted the vision of a completely wireless underground communications system. That remains a physical impossibility right now, but most mines need better access to the underground network through the use of Wi-Fi Access Points, according to Eric Brouillette, vice-president of sales at Laird global mining division. Surveyors benefit from continuous communication to surface, and most advanced fleet management solutions and programmable logic controllers have Wi-Fi available as a medium. “You need to deploy a Wi-Fi backbone in key areas underground, and the technology is available now,” says Brouillette.
But the density of coverage required for having seamless roaming makes installing wireless access points expensive. Plus, according to Joe Gladu, Canadian general manager at PBE Group, the rarity of such systems in the underground environment drives up their price. “Right now, if you look within Canada at organizations that provide purpose-built solutions for the mining industry centred around wireless and voice-over-internet protocol (VOIP), there’s less than a handful that do it,” he says. “There’s a whole bunch standing on the periphery trying to take solutions that are built for surface and bring them underground. And the challenge there is that they’re not fit for purpose, for a dusty, dirty environment. They just won’t hold up.”
Nevertheless, Gladu believes that wireless and VOIP solutions will become less expensive, as did the now-ubiquitous leaky feeder technology. He thinks the foreseeable future will include a need for hybrid technology: leaky feeder in the vast majority of the mine and wireless/VOIP in key areas.
The old with the new
Several developers, including Becker Varis and PBE Group, have sought to add data capability directly to leaky feeder lines. Although no technology out there can match the bandwidth of fibre-optic cable – nearly limitless at thousands of megabits per second (Mbps) – mines do not necessarily need that much capacity. Brouillette estimates that most will need no more than 50 to 100 Mbps over the next few years. Mine operators approach fibre-optic cable, which requires more specialized skills to repair compared to the coaxial cable used in leaky feeder systems, with caution.
PBE’s Centrian leaky feeder, installed in upwards of 30 mines, uses a CMTS (cable modem termination system) at the leaky feeder head end and an amplifier that supports a direct radio frequency link to an external cable modem, which in turn can be connected to any Ethernet-based device at about 22 Mbps downstream. Becker Varis’ Smart Com uses amplifiers similarly, with an advertised bandwidth of 54 Mbps downstream.
Taking the same idea in a different direction, the SIAMnet system sold by Laird adds antennas that allow the coaxial cable to be installed in shotcrete or protected by metallic pipes. At that point it is no longer a leaky feeder system, as the cable itself does not radiate RF energy. “Our system is an extension of the surface Ethernet network into the underground mine,” says Brouillette. The company has responded to customer requests by shrinking components and improving bandwidth to the current 150 Mbps from 20 Mbps in 2005.
Hudbay Minerals is drawing on several of these elements for its Lalor mine in Manitoba. “I’d say the technology we’re deploying is at the upper end of what’s currently available,” says Richard Trudeau, mine manager of the Flin Flon and Snow Lake mines. Still under construction, Lalor will eventually have a leaky feeder radio system with 60 Mbps Ethernet data capability and three 10 gigabit Ethernet networks (for corporate, video, and process functions). It will also have separate fibre-optic networks for specific hoists and for remote-controlling rock breakers. Some areas of the mine will have Wi-Fi coverage.
For phone service, Trudeau says most offices and shop telephones will use the corporate Ethernet network, but up to 50 copper phone lines are planned for critical locations like shafts and refuge stations. This is part of a general backup strategy that includes four key requirements: redundant power sources; backup battery systems; redundant, ring-style installations; and communication that can be powered from surface, which is true of the radio and copper lines at Lalor.
In addition to these standard safeguards, the National Institute of Occupational Safety and Health (NIOSH) has worked with U.S. regulators, industry and labour unions to speed up nascent alternatives. In the early days after Congress passed its 2006 MINER Act, mandating better communications and personnel tracking in underground coal mines, NIOSH and the Mines Safety and Health Administration (MSHA) set up a test area at a coal mine and invited various vendors to test their equipment.
“It was amazing,” says NIOSH researcher John Burr, “that while these things might work very well above ground, when you get in the confined area of an underground coal mine with all the conductive media and noise sources around you, very few of these technologies showed any promise at all. And for the ones that did, it was obvious that a significant engineering effort would be required to adapt them. And most of the vendors at that point did not have the willingness to proceed. And that’s where NIOSH really stepped to the plate with its funding strategy, to see if we couldn’t take the most promising one and push it.”
That was how defence-focused Kutta Technologies entered the mining world. The company has since commercialized a medium-frequency backup system called DRUM that “hitchhikes” on existing mine infrastructure, so that metal conveyor frames and phone lines become communication conduits. The portable version of the repeater unit can be stored in key areas and grabbed in case of emergency.
Using some extra wiring, DRUM can also be installed so as to be interoperable with high-frequency radio handsets. Interoperability is another strong interest at NIOSH, according to Jeffery Kohler, director of the office for mine safety and health research at NIOSH. “You can think of it as having little electronic interfaces distributed in the mine, such that the interface is capable of receiving a signal on, say, the medium-frequency band, but then converting it to and attaching it to the infrastructure for the leaky feeder or for the fibre-optic router-based system. When you start to talk about those options, you really expand your ability to have post-accident functionality,” he says.
Through-the-earth communication – TTE, or as Kohler calls it, “the holy grail” – could find its place in such an interoperable system. Truly wireless, low-frequency signals can penetrate from surface through thousands of feet of rock, but their uses until recently have been limited to simple one-way messages via a very large surface loop antenna. Several NIOSH-funded alternatives have improved on that: Lockheed Martin’s MagneLink allows two-way communications, as does E-Spectrum’s Rescue Dog. But Kohler would like to see something even better: a TTE system that could catch another system’s signal and send it to surface.
Although TTE itself is in its early stages, the basic principle of interoperability and the other secondary systems available have been proven, according to Kohler. “I think we can say that there aren’t serious technical limitations holding back the adoption of these secondary systems,” he says. “I think the technology is there, it’s demonstrated, it’s reliable; it’s more a question of people deciding how they work it into their operating strategies.”
The sector matures
Whatever the uptake on the user end will be, it will rely on a limited number of suppliers. Joe Gladu says that after the MINER Act passed, “it was a very interesting time to be on the supply side, because it created this boom for organizations such as PBE and a lot of others that had communications solutions.” That resulted in consolidation as large players like PBE sought to marry different technologies by buying smaller companies, while companies with lower-tech solutions were unable to compete.
“Once MSHA was satisfied that those solutions were in place, you saw that boom and that demand for technologies drop significantly,” continues Gladu. “So the result is you had a consolidation in terms of the numbers of players that were there. And it’s probably a handful of people that play in that space now versus what you saw in 2008.”
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