“We found that the leaky feeder is pretty ordinary in the sense that you’ve got 30m to transmit and 100m to receive in line of sight of the leaky feeder. Coverage is a big problem.You race off and say let’s put in a leaky feeder and it will get rid of our inductive loop Taiheiyo radio system which costs us a fortune in maintenance and handsets now that it’s so old. But you need another system on top of a leaky feeder to get that coverage. The more we’ve thought about it the more we realise leaky feeder isn’t the saviour and it isn’t the answer for emergency communications which are important to us in underground situations.”
Eaton said MineCom was chosen to be the standard supplier of leaky feeder systems to BHP’s Illawarra collieries.
At the company’s new Crinum mine in Queensland, four forms of communication are in use: Mine Site’s PED system, Austdac’s in-house telephone system linked back to the surface, a two-way leaky feeder radio system from Nixon Communication and a DAC system throughout the mine. This is a fairly typical communications configuration for modern coal operations, characterised by the different functionality of the various parts of the system.
Crinum’s mine electrical engineer Lionel Smith said the need for genuine two-way communication between all personnel underground was rare. Only key personnel utilised the leaky feeder radio at the mine. Everyone else walked to phones if they needed to contact the surface. Emergency recall was achieved through the PED.
Yet there remains something mightily attractive about the picture of the future as painted by Warwick Sommer of Newcastle electrical equipment manufacturer Ampcontrol.
“You’ll have a mining engineer sitting at home and he gets a buzzer on his pager saying a shearer is down via a leaky feeder backbone,” he postulated.
“He will be able to go to his mine homepage on the net and pick up the shearer on longwall number 1, or whatever, and actually get a line of sight video link of his crew working. Then he can say, well the machine set-up doesn’t look correct, have you tried this? That’s where I suggest mine communications can end up, but it’s 3-5 years away. ‘You can’t get that unless you go to voice, data, video communicators.”
MineCom’s Wilson argued such technology had been in place for some time, which “is why we came up with the Flexcom 2000 design”
“The same digital handheld that the engineer uses to talk to the operator underground can also be used to transmit and receive video, or talk between two computers or monitor and view a pump station, sub station, etc. The new system has been designed in Australia, and will initially be built in Australia and yes, it has been designed for use in coal mines from day one.”
Appealing though these long-term visions are, there are numerous implications, some less apparent than others. Such systems revolve around operational management and manning issues. By itself, a plethora of information, sourced perhaps from transducers, real-time video footage, or a range of other inputs, is nearly useless. Someone, with the aid of an interface such as a sophisticated computer program, has to analyse the information and make management decisions. That individual has to be trained, not only to operate the software, but to understand what the information represents and how to act upon it. This could have the effect of spreading information and knowledge usually held by engineers and geologists. Furthermore, there are numerous experienced underground operators who will insist that nothing ever replaces the gut instinct often displayed during a physical examination of a faulty system. Marrying gut instinct with new forms of information is going to be one of the central challenges as communication systems come into their own.
Another of the human implications of leaky feeder systems is the issue of tracking people and equipment. Sommer said: “If we could offer a customer a comprehensive and accurate personnel tagging system, they will have to weigh up the safety benefits versus the potential industrial relations backlash, from the unions, that comes with this level of personnel accountability.”
It is the tracking of people and equipment which has some operators secretly droolling about greatly increased efficiency. Mine Site is busy putting together a tagging system which it hopes to make available to coal mines within 12-18 months. The company said it had had some successes with metalliferous mines using the system but making the transfer into underground coal mines was going to be the challenge.
“Metal/hard rock mines are at an advantage when it comes to communications with no IS requirements,” Kent said. “ It means newer technologies can be tested and applied far more readily than in coal mines. This has resulted in hard rock mines introducing technologies several years earlier than coal mines. Some, if not all, of these developments could offer benefits to coal mines, so feedback from coal miners on developments within the hard rock industry could be very useful in ensuring technology transfer is achieved, where applicable, and without loss of functionality. Mine Site Technologies would certainly welcome the opportunity to discuss what leaky feeder can truly deliver and how to implement it with mine operators.”
Many operators know the jury is still out on the ability of leaky feeder systems to offer comprehensive voice, video and data coverage, and until a verdict is delivered, cash consciousness will continue to dictate caution in the purchase of communications systems for underground coal mines.
