Communications: Vital for Safety and Management
Reliable communications is an increasingly important factor in mine safety and productivity. Comms systems are improving rapidly, but are not yet fail-safe.
By Simon Walker, European Editor
Shiftboss: "I'm on the 1,600 level and want to go down to 2,000."
Cage tender: "That's fine by me ....." We draw a discreet veil over the con- versation that ensued when the frustrat- ed official finally caught up with the recalcitrant operative, but the incident serves well to illustrate the power and pitfalls of person- to-person communications. The shifter needed the tender's help insofar as he controlled where the cage was at any particular time. The tender—perhaps in the belief the broadcast conver- sation might improve his own image in the eyes of anyone who happened to overhear—chose to exercise the power of veto over the shifter's request.
What this situation also shows is that an effective com- munications system needs to be designed so that no single indi- vidual has the capability of jam- ming it, either by mistake or bad intent. Both the shifter and the tender had their own agendas, no doubt equally important in their own eyes, but the over- all effect of the impasse was to render ineffective timely management of the operation. Put another way, a simple con- versation between two people, who per- haps did not get on too well personally and so took opposing views, jeopardized the way the mine was being run during that particular shift.
That was yesterday, and both needs and expectations have moved on a lot since then when it comes to communica- tions. Today's management structures rely on regular data inputs from all areas of an operation; information that can be fed into systems that can control every- thing from fan speeds to flocculant addi- tion, as well as keeping track of person- nel and equipment.
Without doubt, the driving force in the context of personnel tracking has come from the coal industry, with recent inci- dents having served to reinforce the need for accurate location of people and machines underground. Yet existing sys- tems, no matter how effective they may be during normal operations, can provide little in the way of assistance in emer- gencies if the incident itself has caused irreparable damage to the system infra- structure. Thus there is an inherent prob- lem: to be effective under all situations, and especially in times of dire need, a communications system has to be essen- tially indestructible. No cables that can be cut; no repeaters that require their own power supplies; no hardware that can fail.
And that, of course, is the conun- drum. Current technology has been developed to such an extent that mine communications networks have become more and more reliable, both on surface and underground, under normal working conditions. The challenge is to make them equally reliable on the rare occa- sions when things do not go to plan.
For What Reason?
The term "communications" covers a wide range of issues and requirements, from basic voice-to-voice to transmitting significant amounts of operational data to satisfy demands as varied as real-time control, machine movements, equipment maintenance sched- uling and accounting. Comms networks can cover as little as a few offices, or can reach around the world. Data from machines in one country can be analyzed by OEMs in another; exploration teams can adapt their programs on the basis of assay results from distant labs.
On an individual mine basis, the question has to be asked: "what does the comms network need to do here?" The require- ments of a small mine will clear- ly be different from those of Kidd Creek or Olympic Dam. Similarly, a mine laid out as a room-and- pillar operation will present dif- ferent challenges in terms of its infra- structure needs than one, say, that extends to a depth of 1,000 m or more from surface. And, without wishing to state the obvious, a comms system for an open-pit will have to address a complete- ly different set of operational require- ments from one designed for the under- ground environment.
Going back to the example of the shifter and the cage tender, in the early 1970s comms technology had pro- gressed from "four-plus-two bells to go down, one bell to go up" to permanently nstalled telephone systems at the shaft bank and on the shaft stations, but that was about the limit. The concept of hav- ing a comms system that could cover a complete underground mine was still some way away, but when it became available, uptake accelerated.
That is not to say, however, that acceptance was universal. In a report prepared not much more than a decade later, James Cawley of the former U.S. Bureau of Mines commented that the introduction of leaky feeder-based radio systems had not been without its prob- lems. "Miners frequently viewed the radio as a means for management to tighten its control over them," he said, explaining "the miner's natural resist- ance to change caused rejection or excessive criticism of the system."
However, there may have been some significant contributory factors at play here. "In all cases studied, the miners were not properly trained in the use of the radio equipment. This gave rise to the following problem areas: the systems were not used to their full potential, and; miners were unaware of the cost of a portable radio and abused the equip- ment. This tended to increase mainte- nance costs," said Cawley.
There was a silver lining to this par- ticular dark cloud, though, since he also found that "several mines reported after an initial period of adjustment, miners who carried portable radios regarded them as a status symbol, designating them as VIPs in the mine operating struc- ture." In these situations, he noted, there was significantly less abuse of radio equipment.
From this, it becomes clear in the early days of mine-wide comms networks, the basic concept behind the investment was often unclear to the people who stood most to benefit from it: the indi- vidual miners.
The concept of radio systems for use underground is not as recent as some might imagine. In a report prepared in the early 1980s on the development of medium-frequency radio systems for use in underground mines, Harry Dobroski and Larry Stolarczyk noted the concept was already under development in South Africa in the late 1940s. "The result was that by 1973, an advanced 1-W single sideband (SSB) portable radio system had been developed that apparently worked well," they said.
However, when the USBM evaluated this system in U.S. coal mines, it proved to be less effective for a number of rea- sons, not least of which was the greater level of electrification used in these operations. Indeed, only a few years before, Dr. M D Aldridge, in an analysis of communications systems in coal mines, had identified that there were then just two systems in common use: various forms of telephone, and carrier- current radio systems that used a trolley line as the interconnection circuit. "Carrier-current radio is used almost exclusively for control of rail traffic by the dispatcher while the telephone sys- tem provides the primary means of voice communication," Aldridge said.
The problem, of course, is conven- tional telephone systems are, by their very nature, inflexible. They need hard- wiring, with fixed communication points, so have limited practical value in the highly dynamic underground mining environment. The communica- tor has to go to the telephone before being able to communicate. Hence the long-standing interest in developing some form of wireless network that would allow miners to be in touch while on the move.
It quickly became apparent there were significant challenges to establishing a reliable radio network underground. In 1981, a report prepared for the USBM concluded that: "medium-frequency (MF) transmission is feasible and optimum in all metal/non-metal mine drifts having existing wiring regardless of the area of the drift cross-section. This is contrary," the report's authors went on, "to that observed for UHF signals, where commu- nications are restricted to mines with large drift cross-sections, due to excessive refractive and roughness (scattering) loss- es incurred in small drifts.
"MF communications can be effec- tively used to streamline haulage opera- tions and locate key underground super- visory and maintenance personnel," they added, before pointing out that: "MF sys- tems can also provide advance warning of impending health and safety problems in mine working areas where permanent mine wiring and fixed communications are not economically feasible."
This last comment is interesting in its own right, since it suggests that current perceptions (in the early 1980s, that is) were still focused on hard-wired tele- phone systems, with radio as an accept- able alternative where these could not be installed for one reason or another. The focus on personnel safety is also signifi- cant, and is echoed in many of the research reports issued at that time.
More recent events have highlighted the benefits, and indeed the shortfalls, of today's underground comms systems. On the plus side, we have the ability to warn the entire workforce of a potential haz- ard, and bring everyone to the surface quickly and safely through the use of per- sonal locator units. Conversely, we have also seen that even the most comprehen- sive comms system can be physically overwhelmed by the speed of unfolding tragedies, leaving vulnerable the people who have relied on them for their safety. Systems have improved, and are now uni- versally accepted for their benefits, but are not yet fail-safe.
Last year, Canmet published a compre- hensive study report on the various comms concepts now available for use in underground mining. The impetus for the recent surge in development came, the report notes, from the passing of the Miner Act in 2006, with U.S. coal mines now required to install systems for both communications and personnel location. The report drew on assistance from the West Virginia Office of Miners' Health, Safety and Training, Emergency Com- munications and Tracking, which has itself undertaken trials of various systems in the state's mines and has developed a comprehensive library of reports and data relating to underground communications technology (See www.wvminesafety.org/ comtraclibrary.htm).
Prepared by Pierre Laliberté at Canmet's experimental mine section in Val d'Or, Québec, the report lists the var- ious systems available, with their bene- fits and disadvantages. It also reports on the results of a survey of 13 mining com- panies which, if anything, make some- what uncomfortable reading. "The find- ings suggest that the level of knowledge of new communication technologies varies considerably," it notes. "It also appears that the mining industry is reluctant to use these new technologies even knowing they are reliable." On the other hand, a majority of the companies polled for this survey said that their cur- rent comms needs are being met by the manufacturers.
The Canmet report looks at:
• Very-low frequency through-the-earth (VLF/ULF);
• Medium-frequency (MF);
• VHF leaky feeders;
• UHF leaky feeders;
• Distributed antennas;
• Mesh networks; and
• Ultra-wide band (UWB); before turning to a review of equipment and personnel tracking systems. Other aspects cov- ered include anti-collision systems, and remote controls and remote opera- tion, although these are outside the focus of this article.
Just by looking at this list, it is clear mining companies now have a wide range of choices when selecting a comms system. The Canmet report also pointed out the suitability of a specific system is highly dependent on the layout and requirements of the individual mine. For example, is the requirement just for voice communication, or for personnel tracking, or is a high volume of data transmission needed as well? What level of system redundancy is appropriate? Each set of circumstances will dictate which of the systems is likely to give the best service.
E&MJ asked Pierre Laliberté about the penetration of different systems with- in Canada's mining industry. By far the greatest proportion of mines use leaky feeders, he said, with the technology hav- ing been established for well over 20 years. By contrast, tracking and Wi-Fi (VOIP – voice-over-internet protocol) sys- tems have yet to make a significant impact within the industry, with very few mine operators having decided to invest in them.
Nonetheless, he went on, there is increasing interest in high-tech systems, with fiber-optic links for data having been used extensively for applications such as programmable logic controllers (PLCs) for a considerable time now. "It is, of course, a question of balancing costs against per- ceived benefits and payback," he said. "In existing mines, there needs to be a good argument to convince management that it is worthwhile changing an existing system. It is much easier to design a new system into a new mine.
"There is also the question of mainte- nance," he said. "Leaky feeders are easy to repair if they get damaged, but IT sys- tems are much more complicated and need specialized people to look after them. Even so, these new communica- tions systems are slowly getting into the mines, and they will be the standard in a few years' time."
Given the speed with which communica- tions technology generally has been advancing, it comes as little surprise that there have been rapid recent develop- ments systems for mining applications. According to Laliberté, several manufac- turers have contacted him since the pub- lication of his report, pointing out that their products and services have been upgraded over the past couple of years.
Turning to the hardware needed for satellite communications, in April Inmarsat revealed details of its latest hand-held satellite phone, the IsatPhone Pro. The company claims that this will offer good global coverage, robustness, reliable network connectivity, clear voice quality, ease of use, and the longest bat- tery life currently available—up to eight hours' talk time and up to 100 hours on standby.
Designed with heavy industrial use in mind, the new phone is also dust-, splash- and shock-resistant, and can operate at temperatures from -20°C to 55°C, Inmarsat adds. It also supports Bluetooth, can be used hands-free, and features a larger keypad that makes it easier for a user to dial when wearing gloves.
For underground specifically, Mine Radio Systems (MRS) reports having installed over 400 of its systems in min- ing and tunneling operations over the past 25 years. Its primary product, the Flexcom system, uses leaky-feeder tech- nology to give simultaneous voice, video and data transmission. Meanwhile Multicom, also based on leaky-feeder networks, provides 32 voice/data chan- nels and 16 video channels to give real- time information access, and can also be integrated with fiber optics to provide broader bandwidth, MRS says.
Fiber optics have a major advantage over leaky feeders in terms of their data- transport capacity and integrity, but pres- ent greater challenges in terms of cable strength and maintenance. As U.S.- based Amphenol Fiber Systems International (AFSI) points out, fiber- optic cables are unaffected by noise, lightning and the various forms of elec- tromagnetic interference associated with electric drives used in mining. A fiber- optic Ethernet also allows operators to use VOIP systems to link surface and underground communications into one system, the company says, while adding that cables can be designed to house spare fibers (dark fiber) that can be used for communications in the event of an emergency.
Mining-specific products from AFSI include multi-channel fiber-optic con- nectors and custom-made, Kevlar-rein- forced cable assemblies that are, the company claims, simple to alter or extend when the need arises. Connectors are designed so as to be easy to clean, even in dirty underground conditions.
Last year, two longwall operations in Australia, Peabody's Metropolitan mine and Rio Tinto's Kestrel, carried out trials on a leaky-feeder/UHF radio system sup- plied by Becker Mining Systems. Becker's radios had received regulatory accreditation there earlier in the year. As well as interconnecting with the feeder system, the radios also give direct per- son-to-person communication capability, Becker reports, as well as messaging and emergency facilities.
Looking at personnel location in a somewhat different way, L-3 Communi- cations is currently developing its Tru- Tracker system which, instead of attach- ing a tag on a moveable item and using a fixed receiver to identify and locate it, uses a network of long-endurance RFID tags at fixed points throughout a mine, with the miner or equipment carrying the receiver/reader unit. Tru-Tracker relies on an ultra-wideband system that overcomes the reflective surfaces and other noise that impede existing narrow-band com- munications, the company states. Tag signal data are stored by the reader unit, then transmitted at regular intervals to the surface control terminal, which can display individual locations in real time.
Tru-Tracker complements L-3's Acco- lade wireless mesh mine communications system, which incorporates individual radios that are linked through fixed mesh nodes and gateway nodes to a surface con- trol center. More details of mesh systems can be found in E&MJ's most recent arti- cle on the topic, in the July/August 2009 edition (pp.48–51). Like many recent developments, Accolade has been targeted initially at the coal sector, with L-3 report- ing recent contracts to install systems at Arch Coal's Lone Mountain and Mountain Laurel complexes in Appalachia. Nonethe- less, the technology can be transferred to the hard-rock sector, where conditions may be different but the need for effective communications remains the same.
Having a reliable communications sys- tem, whether it is between remote explo- ration camps and head office, or between people underground, is becoming increas- ingly important. Mine operators have to decide what their requirements are, and then solicit responses from suppliers to meet these at a realistic cost. Individual circumstances may require tailor-made solutions, or at least modifications to the standard packages that are on offer.
Good communications have become a watch-word of the 21st Century, helping improve miners' health and safety, oper- ational control and, ultimately, corporate success.