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
Many years ago, when working as a student engineer at a mine in northern Canada, I overheard the following exchange between the duty shiftboss and the cage tender. The means of communication was the shaft phone system, which was broadcast in the shifters’ office and at each shaft station.
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 conversation that ensued when the frustrated official finally caught up with the recalcitrant operative, but the incident serves well to illustrate the power and pitfalls of personto- 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 conversation 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 communications system needs to be designed so that no single individual has the capability of jamming 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 overall effect of the impasse was to render ineffective timely management of the operation. Put another way, a simple conversation between two people, who perhaps 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 communications. 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 everything from fan speeds to flocculant addition, as well as keeping track of personnel and equipment.
Without doubt, the driving force in the context of personnel tracking has come from the coal industry, with recent incidents having served to reinforce the need for accurate location of people and machines underground. Yet existing systems, no matter how effective they may be during normal operations, can provide little in the way of assistance in emergencies if the incident itself has caused irreparable damage to the system infrastructure. Thus there is an inherent problem: to be effective under all situations, and especially in times of dire need, a communications system has to be essentially 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 conundrum. 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 occasions 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 scheduling 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 requirements of a small mine will clearly be different from those of Kidd Creek or Olympic Dam. Similarly, a mine laid out as a room-andpillar operation will present different challenges in terms of its infrastructure 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 completely different set of operational requirements from one designed for the underground environment.
Going back to the example of the shifter and the cage tender, in the early 1970s comms technology had progressed from “four-plus-two bells to go down, one bell to go up” to permanently installed telephone systems at the shaft bank and on the shaft stations, but that was about the limit. The concept of having 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 problems.
“Miners frequently viewed the radio as a means for management to tighten its control over them,” he said, explaining “the miner’s natural resistance 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 equipment. This tended to increase maintenance costs,” said Cawley.
There was a silver lining to this particular 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 structure.” 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 individual 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 reasons, 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 carriercurrent 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 system provides the primary means of voice communication,” Aldridge said.
The problem, of course, is conventional telephone systems are, by their very nature, inflexible. They need hardwiring, with fixed communication points, so have limited practical value in the highly dynamic underground mining environment. The communicator 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.
Workers Stay Happier by Staying in TouchIt 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 communications are restricted to mines with large drift cross-sections, due to excessive refractive and roughness (scattering) losses incurred in small drifts.
As mining projects spring up in increasingly remote areas of the world, feelings of isolation can become quite common throughout an onsite workforce. One key to retaining employees facing long periods of separation is to provide convenient communications to the outside world.
Vancouver, British Columbia-based First Quantum Minerals, which operates copper/gold mines in Zambia, Democratic Republic of Congo and Mauritania, has taken steps to alleviate this problem by setting up a satellite earth station specifically for the communication needs of employee housing compounds. New Era Systems, of Pompano Beach, Florida, already handles the full communication needs of the company’s mine sites, and now has been tasked to do the same for the compounds.
Phil Thomas, president of New Era Systems, explained the process of providing satellite communication for this purpose isn’t a complex task. “We send FQM a complete equipment package and a local installer makes the system operational within three days of receiving it.”
The system consists of a dish, a satellite radio, modem and a router. Depending on the layout of the compound, each room can be connected by cable or wireless link. An important point, said Thomas, is the housing communication system is totally separate from the corporate system.
With the communications system up and running, employees are able to exchange e-mail, photographs, telephone and even video conversations with their families and friends.
“MF communications can be effectively used to streamline haulage operations and locate key underground supervisory and maintenance personnel,” they added, before pointing out that: “MF systems 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 telephone systems, with radio as an acceptable alternative where these could not be installed for one reason or another. The focus on personnel safety is also significant, 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 hazard, and bring everyone to the surface quickly and safely through the use of personal locator units. Conversely, we have also seen that even the most comprehensive 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 universally accepted for their benefits, but are not yet fail-safe.
Last year, Canmet published a comprehensive 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 Communications 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 various systems available, with their benefits and disadvantages. It also reports on the results of a survey of 13 mining companies which, if anything, make somewhat uncomfortable reading. “The findings 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 current comms needs are being met by the manufacturers.
Lightweight Fiber Optic Reel System Offers Multiple Carry OptionsThe Canmet report looks at:
Roanoke, Virginia, USA-based Optical Cable Corp. (OCC) has developed a Modular Fiber Optic Reel System (MARS) claimed to be the industry’s first lightweight cable deployment system designed for use in harsh-environment fiber-optic installations such as mining.
Constructed of high-impact glass reinforced polymer material, MARS offers features not afforded by metal-style reels. The lightweight, modular system is easily transported in a variety of carrying options, including a transit case, A-frame, bumper mount or backpack. A retractable crank and handle system allows operators to easily rotate the reel during payout or take-up. To maintain optimal connector operation, an optional built-in fiber optic connection cleaning kit ensures connectors remain dirt- and dust-free in harsh environment situations.
“The MARS system is a vast improvement over metal reels, which are heavy to transport and can rust in field deployments making them even harder to use,” said Pete File, director of specialty sales, OCC. “These modular MARS components are ideal for applications where cable needs to be deployed and reeled-in quickly and stored efficiently in tight spaces.”
MARS components are designed to meet or excel MIL-R- 3241E requirements. Reels can be stacked and interlocked during transit and are available in a variety of colors, with configurations to meet every deployment need. Reel widths ranging from 5 in. to 26.75 in. provide options for varying cable lengths. Total weight ranges from 9.5 to 14 lb.
• 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 covered include anti-collision systems, and remote controls and remote operation, 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 within Canada’s mining industry. By far the greatest proportion of mines use leaky feeders, he said, with the technology having been established for well over 20 years. By contrast, tracking and Wi-Fi (VOIP – voice-over-internet protocol) systems 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 perceived 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 maintenance,” he said. “Leaky feeders are easy to repair if they get damaged, but IT systems are much more complicated and need specialized people to look after them. Even so, these new communications systems are slowly getting into the mines, and they will be the standard in a few years’ time.”
Given the speed with which communications technology generally has been advancing, it comes as little surprise that there have been rapid recent developments systems for mining applications.
According to Laliberté, several manufacturers have contacted him since the publication of his report, pointing out that their products and services have been upgraded over the past couple of years.
One of the industry’s suppliers of satellite-based comms systems, CapRock Communications, was recently taken over by Harris Corp., in a deal worth $525 million. CapRock provides services such as corporate networking, VOIP, broadband and real-time data and video transmission on a world-wide basis, allowing mining companies to link their exploration, production and administrative operations. The company cites PT Arutmin and PT Kaltim Prima Coal in Indonesia as two of its clients, using satellite technology to link their offices, mines and port facilities.
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 battery 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-,
Cutting Through the Noise
One of the greatest challenges in person-to-person communication in noisy working environments is actually being able to hear what the other person is saying. A conversation held next to a rotating ball mill or a rock drill can often end up being a shouting match, with no guarantee that the correct information has been received on either side.
The Australian company, Sensear, offers one solution to the challenge of achieving effective communications in situations where the noise level is so dangerous that people are compelled to wear double hearing protection. Sensear claims a world first with its Smart Double Protection (SDP) communication muff, which uses the company’s SENS (Speech Enhancement, Noise Suppression) technology. This simultaneously isolates and enhances speech while suppressing dangerous background noise. The latest addition to Sensear’s range of high-noise communication products, the SDP system uses a combination of earplug and earmuff technology to provide clear communication via two-way radio and Bluetooth cell phones in noise levels of up to 120 db, while the user’s hearing remains protected, the company states.
Sensear claims it has the only technology that can effectively distinguish speech from background noise. Its SENS system combines an array of tiny microphones connected to a small processor within its products. This acts to distinguish speech from background noise, selectively enhancing speech and simultaneously suppressing noise. Postfiltering techniques are used to improve the system performance. The background noise characteristics are retained, including binaural capability (the natural ability to decipher the direction of any sound), while at the same time lowering noise to safe levels to ensure users remain aware of their surroundings. The result, Sensear says, is high-quality natural speech played directly into earmuffs or earplugs, or optionally connected via Bluetooth to a mobile phone or two-way radio.
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 mining and tunneling operations over the past 25 years. Its primary product, the Flexcom system, uses leaky-feeder technology to give simultaneous voice, video and data transmission. Meanwhile Multicom, also based on leaky-feeder networks, provides 32 voice/data channels and 16 video channels to give realtime 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 datatransport capacity and integrity, but present greater challenges in terms of cable strength and maintenance. As U.S.- based Amphenol Fiber Systems International (AFSI) points out, fiberoptic cables are unaffected by noise, lightning and the various forms of electromagnetic interference associated with electric drives used in mining. A fiberoptic 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 connectors and custom-made, Kevlar-reinforced 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 supplied 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 person- to-person communication capability, Becker reports, as well as messaging and emergency facilities.
Other safety-orientated systems from the company include its collision-avoidance system, which uses tags carried by personnel and vehicles to alert equipment operators their presence nearby. Tags can be fitted to cap-lamps, or to machinery, with mobile equipment fitted with antennae to detect their signals and then warn the operator accordingly.
Looking at personnel location in a somewhat different way, L-3 Communications is currently developing its Tru- Tracker system which, instead of attaching 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 communications, 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 Accolade wireless mesh mine communications system, which incorporates individual radios that are linked through fixed mesh nodes and gateway nodes to a surface control center. More details of mesh systems can be found in E&MJ’s most recent article 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 reporting recent contracts to install systems at Arch Coal’s Lone Mountain and Mountain Laurel complexes in Appalachia. Nonetheless, 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 system, whether it is between remote exploration camps and head office, or between people underground, is becoming increasingly 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, operational control and, ultimately, corporate success.