In March, 1989, a miner was killed at Noranda’s Lyon Lake mine in Ontario when a load-haul-dump machine (LHD), controlled by a radio frequency remote control, scooped him up and drove over a 24-metre ledge into a sublevel open stope. The accident occurred when an identical radio transmitter (operating on the same frequency and the same digital identification code) used to operate a remote LHD on the level below took over control of the LHD carrying the hapless miner. Previous to the accident, the LHD on the upper level was under remote control, but when the operator shut off his transmitter, the identical transmitter on the level below took control of both machines. The control units were manufactured by Nautilus International of Burnaby, B.C.
A subsequent judicial inquest had eight recommendations for the safe operation of such devices. One is that mines keep a log book containing all identification codes, frequencies, etc., so that miners can sign out remote control transmitters. Such a system may have prevented the fatality at Lyon Lake. Nonetheless, in the near future the Ontario government is expected to propose legislation governing the use of radio frequency remote-control units in the province. And the Mines Accident Prevention Association of Ontario has drafted a 6-page list of 18 specific guidelines for manufacturers and users of remote control devices (copies may be obtained from George Sotiro, project engineer, MAPAO, Box 1468, North Bay, Ont. P1B 8K6.)
In the 12 months since the accident, Nautilus has significantly modified its remote-control units. Tough polycarbonate labels, with hardened clear windows and a light-emitting diode display, clearly indicate machine identification codes, operating frequency, serial numbers, and so on, on each unit; 3-second delays with audible alarm and visual countdown have been included to prevent the operator from accidentally hitting the wrong switch and starting the engine, releasing the parking brake or activating the fire suppression system; the system checks all switches and the engine start button is disabled unless the parking brake is on. If two transmitters are on the same frequency and the same identification code and both have about the same effective radiated power, then the radio control system will shut down and ignore both transmitters. The company is also introducing a “bodyguard” system. It causes a machine under remote control to sound its horn and flash its lights if it comes within a pre-set warning distance to the operator. Then it will come to a full stop, put the machine in neutral and reduce the throttle if it comes within a pre-set “stop” distance of an operator.
“Our systems now cost significantly more to produce,” says president Jason Hart, “but these changes have been absorbed by Nautilus and have not affected our list price.” Nautilus supplies remote-control LHD-manufacturer Eimco Jarvis Clark.
At least three other manufacturers supply radio frequency remote control devices to Canadian mines. Black Box Radio Remote Controls of Georgetown, Ont., has sold about 50 radio frequency remote-control systems to underground mines. The company also manufactures a more advanced system which shuts down the machine if two signals of the same frequency are detected. But chief engineer Ron Patey says mine operators prefer the older version because they are familiar with its service systems.
Wagner Mining Products of Portland, Ore. has been in the radio- frequency remote control business for roughly 10 years. “In our experience, the Moog system (manufactured by Moog Inc. of East Aurora, N.Y.) is the best,” says Walt Goska, engineering technician for Wagner. Each unit is adjustable to four different frequencies and even if a receiver picked up two signals on the same frequency, a cancelling feature automatically shuts the machine down. About two years ago, Wagner redesigned its remote control/machine interface to make it more compact and simple, Goska says.
Dan Thomson of Sudbury-based Thomson Technology says the Ontario guidelines don’t go far enough. “We think no mine should use the same frequency on any two machines,” Thomson says. For four years now, his company has been marketing radio frequency remote-control technology developed in the overhead crane industry by Telemotive of Chicago and manufactured in Canada by Berlet Electronics of Burlington, Ont. The system is more than a remote-control system. Equipped with a micro-computer, the Telemotive system can monitor engine oil pressure and shut down the machine if there is an emergency. The Telemotive system requires two identification codes to operate and is also designed so that a machine is operated in a similar sequence as it would be in manual operation, Thomson says. Priced at about mid-range compared to competitors, six Telemotive systems have been purchased by Canadian mining companies and about 25 are on order.
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