This makes the cable difficult to install during development and to recover as the longwall retreats. These cables were jointed using common mechanical splices fitted into splice cassettes and then the cassette was housed in some sort of dust and water proof housing to protect the joints from the elements. The combination of cable and connectors doesn’t mix very well with a longwall monorail system, and is not sufficiently resistant to damage from excess tension, abrasions, and equipment strikes. In short, no mine-tough optical fibre cable and mine-tough connectors to join them were available.
Despite all this, many longwall operators remain committed to the idea of an optical fibre based communications system, saying it offers unprecedented management opportunities. The eventual aim? To run a completely automated longwall face. Optical-fibre-based systems are capable of offering a true communications “superhighway” with sufficient bandwidth for data, voice and video communication, the latter the key to longwall automation.
These problems have been solved and the products are available today. The solution is to use tactical field deployable, military-grade optical fibre cable; the same stuff that is routinely used by the world’s military services. These cables are tough, extremely reliable (they can survive being run over by an army tank), and are very flexible. In fact they can be wrapped around pillar and post and tied into tight knots without breaking or degradation of signal.
To couple this cable together requires an equally tough and reliable connector. Enter the tactical field deployable Mil-Spec. optical fibre connector. These connectors are being used by some of the world’s military forces, by major sports television networks, and by various other industries that require optical fibre systems that can be deployed and retrieved quickly in severe conditions. The connectors can accommodate cables ranging from one single optical fibre core (channel) up to as many as 12 channels in one connector. They are available in aluminium, bronze, mild steel and stainless steel, and are hermaphroditic, which means they are non-gender specific. Without the use of any tools, a male plug can quickly, with a turn of the wrist, be reconfigured as a female connector.
These connectors are available as in-line cable connectors and are also available as flange-mounted equipment connectors. The connectors can be easily cleaned in the field simply by swirling them in a cup of clean water and then wiping their faces off with a clean cloth (a “t-shirt” will do nicely). If the connector ferrules become scratched they can be easily re-polished in the field. That is, underground, using a simple re-polishing kit. To overcome the problem of entering an optical fibre cable into a flameproof enclosure, an approved optical fibre glanding arrangement is also available and has been successfully used.
Now that the cable and connector issues are solved, what remains unresolved are IS regulations governing all ancillary attachments, such as video cameras and battery supplies. To date it would appear no underground Australian coal operation has yet been able to get truly portable/mobile video functionality. Moderate to high data functionality has been achieved, but at the expense of implementing the traditional (non Mil-Spec.) optical fibre cable/connector systems previously described above, which have a relatively high whole-of-life cost.
One Bowen Basin mine has taken the technological leap and implemented a Mil-Spec optical-fibre-based data network, and has done so with resounding success. The mine has 10 megabit Ethernet links extending all the way to the longwall face. It works, and it works reliably.
Yet there remains something somewhat attractive about the future of longwall automation. You will have a mine employee at the longwall face who is able to go to a PC on the maingate control unit when the face is down and call up equipment drawings and parts books that have been served (transmitted) down the optical fibre backbone. If he needs more help, he can communicate via voice or e-mail to the surface shop, or to the equipment manufacturer half-way round the world. And if more help is needed, live video conferencing is just around the corner.
That’s where I see mine communications going, and most of the technology needed is here now, with video conferencing capabilities only 2-3 years away. You can’t get that unless you go to optical-fibre-based voice, data, and video communications.
In the past it’s been argued that increased data gathering capabilities tend to keep people on the surface, sitting at their desks to manage an underground longwall operation from afar. By itself, a plethora of information, perhaps obtained 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.
Many experienced underground operators insist that nothing ever replaces the gut instinct of an experienced, qualified coal miner. It can also be argued that the greatest opportunity to effect positive business outcomes is to make the business decisions right where the action is — at the coalface. Optical-fibre-based systems allow the mine operator to extend his office network, and hence the plethora of information available there, right down to the working face. Marrying gut instinct with these not necessarily new, but previously unavailable, forms of information is going to be a great bonus to mine operators as communication systems come into their own.
Many operators believe the jury is still out on the ability of optical-fibre-based communications systems to offer comprehensive voice, video and data coverage. However, the verdict is in. Reliable, practical, and affordable fibre-optic-based communications systems are here today.
* John Ruble is Engineering Manager for Nu-Lec Systems, a division of Nu-Lec Projects Pty Ltd.