May 02, 2007NL Technologies, a Canadian designer and manufacturer of underground lighting and digital communications solutions for the mining industry, is readying an RFID system that uses active 433 MHz tags to track and manage miners and vehicles underground.
To build the RFID capability into its network—a fiber optic backbone that includes 802.11 access points—NL Technologies partnered with WaveTrend, a manufacturer of active 433 MHz RFID tags and interrogators utilizing a proprietary air-interface protocol.
The tags are affixed to batteries worn on miners' belts, says Daniel Rose, NL Technologies' chief operating officer, while the batteries are connected to and power the cap lamps miners wear on their heads. Each tag's unique ID number is associated in NL Technologies' Northern Light Digital Software Suite with a miner assigned that specific tagged cap lamp. The tags can also be affixed to vehicles within a mine to monitor and track the vehicles' locations.
To determine the position of a miner or vehicle, two RFID readers—connected to the NL Technologies access points installed in a mine—calculate the coordinates. Tag positions can be determined within a 30- to 50-meter (100- to 165-foot) radius, Rose says. Location information can also be ascertained, albeit on a broader scale, from a single reader, because every access point has an IP address correlated with a zone in the mine. The access points have a linear range of 600 to 700 meters (1,968 to 2,296 feet).
In addition to the tracking capability, NL Technologies also offers Messenger, a two-way Wi-Fi-based radio enabling administrators to communicate with the miners via text messaging. Administrators can send instructions for the day's work, for example, while miners can easily respond by picking among 50 preprogrammed responses.
Another unique aspect to this solution is that it can be used in the event of a mining emergency. Typically, when an accident occurs, networks and communications systems must be powered down to prevent further troubles. For example, in the Sago, W.Va., mining accident of January 2006, in which 12 miners lost their lives, the power had to be shut off in the mine to avoid additional explosions. Thus, rescuers had no way of locating the miners' position or monitoring gas levels. "The rescuers," Rose says, "had to proceed very slowly and very carefully because of the potential of hazardous gases."
Consequently, NL Technologies, which first announced a version of its monitoring network in October 2004, spent the past three years re-engineering the hardware infrastructure to make it intrinsically safe. "The circuitry has been designed to operate at a very low power," Rose explains, "so in the event of a short circuit, there'll be no sparks."
NL Technologies is working on getting approvals for its intrinsic safety features from both the U.S. Department of Labor's Mines Safety and Health Administration (MSHA) and TestSafe Australia, a testing, certification, research and investigation facility.
At the end of May, NL Technologies will begin installing its RFID-enabled network in the Grasstree mine, an underground coking coal mine owned and operated by Anglo Coal Australia, and located in central Queensland, Australia. The implementation will use RFID tags to track about 250 miners initially, and will eventually include vehicles as well.