"MSHA's new performance rules were recently published and established the minimum allowable standards,” said Venture’s Jim Barrett.

“But most people in the industry will be driven by their own values to look beyond the minimum to find ‘the right thing to do’ for their mines and their miners.”

It was for that reason that WMS and Venture partnered to help explain what might be previously unchartered territory for mines that are choosing systems – what wireless technology entails – as well as the benefits of the companies’ system.

The end result of the groups’ research brought them to the current design of the system, according to MineTracer senior engineer Rod Nemitz, and its status as meeting those requirements set forth by MSHA is no accident.

“Our requirements are driven by what is necessary for human life,” Nemitz said.

“We wanted to do the right thing for the people who are at risk in these hazardous environments – even before Sago we were working on this system.”

Wireless coverage

Barrett pointed out that the wireless coverage we are used to, that of cell phones, allows us to understand that there are areas where we can use the devices and others where we cannot.

“[However] an effective underground wireless system must allow every miner to simultaneously receive and send important safety-related communication at all times, especially when an accident is unfolding,” Barrett said.

“Just as importantly, each individual needs to be able to contact the mine office at any time if they urgently need help, and to easily send an alert message and their location.

“By quickly knowing where a miner is and that he needs help, rescuers have the best chance of succeeding.”

Wireless coverage must therefore be designed so that dead zones do not exist in regions of high traffic, those areas being at least two escapeways underground with supplemental coverage in adjacent entries and crosscuts.

Precision

The ability to locate workers through tracking is also vital to a wireless system, and is a central feature of MineTracer, as accuracy and effectiveness of rescue efforts go hand in hand.

“A minimum effective tracking system must continuously cover at least two separate entries (primary and alternate escapeways) and offer, according to MSHA, at least +/-200 feet of absolute accuracy in working areas,” Barrett said, adding that the rate of update is also key.

“If updates take as long as one minute, for example, a man’s travel distance on foot will increase the uncertainty to +/-500 feet (+/-2000 feet if travelling in a vehicle).

“MineTracer provides +/-100 feet absolute accuracy wherever it is installed for continuous tracking [and] can also be configured for more economical zonal tracking, at the discretion of the mine operator, in any areas that are infrequently populated by miners.”

The MineTracer system also manages groups of people underground, as many as 30 at speeds of up to 20 miles per hour.

“A tracking system is useless unless it operates effectively when miners are in groups or are travelling in vehicles,” Barrett said.

According to MSHA’s outlines under the MINER Act, systems must effectively relay safety information in an emergency situation.

Barrett said that while there is no “perfect system” for this at this time, the disadvantages of common walkie-talkies have been improved with two-way text systems, but not without their own issues.

“In times of crisis, voice systems can be overloaded when many miners are all trying to get ‘on-channel’ with a single dispatcher,” he said.

“Worse, voice systems built on Voice over IP (VoIP) mesh have severe capacity limitations – in mesh systems the digital packets carrying your voice information must travel like a bucket-brigade through multiple relay stations called ‘hops’.”

The MineTracer system permits simultaneous usage by many users, particularly important during an emergency, and the system’s effectiveness is increased when a mine uses redundant systems.

“The best underground communication solutions combine more than one of these approaches so that critical communications can take place under all conditions,” Barrett said.

“MineTracer can even operate together with new or existing leaky feeder systems for mine operators that want everyday voice service.”

In the event the system does suffer damage in an underground incident, it is designed to continue working.

“MineTracer uses redundancy, self-healing and multiple alternate communications paths between the surface and underground,” Barrett pointed out.

“MineTracer can also be optionally ‘hardened’ against damage such as roof fall, fire or explosion.”

Standby power

The ability for any communication system to work both before and after an emergency situation is imperative to its use, particularly when standby power is intrinsically safe and lasts long enough to be properly used by crews that may still be beneath the surface.

“The Sago rescue effort lasted 41 hours; Quecreek lasted three days. Clearly, operating times on standby power must be able to handle incidents such as these,” Barrett said.

It is crucial that any portable wireless unit be able to work for 48 to 96 hours without “conscious intervention” by its user as the potential exists that the person could be injured or otherwise incapacitated.

The MineTracer system specifically offers at least 48 hours of power in standby mode for both the infrastructure units and miners’ person-carried devices.

Reliability and ease of use

Robustness of wireless communications systems, including their ease of use and maintenance needs, is also important to a system’s success.

“MineTracer has undergone military standard (Mil-Spec) reliability testing, that far exceeds any requirements of MSHA, and it incorporates self-diagnostics that perform automatic self-health assessments,” Barrett said.

“The earliest MineTracer system has been operating reliably for 18 months in a West Virginia coal mine.”

The most usable units will be straightforward to use and give clear information to workers both underground and at the surface. To make it complex, Barrett noted, could actually cause resistance in use by a mine’s workforce.

Finally, mines are looking to get the greatest value for their dollar, particularly in a slower economic environment. The companies said operations should look at the price of the system but also expenses involved with installation as well as maintenance.

“The best performing systems do not necessarily cost more. MineTracer is the lowest-cost communication and tracking system that meets all MSHA performance requirements for MINER Act compliance,” the companies said.

Venture and WMS noted that the benefits of the MineTracer system in particular go well beyond safety, and one coal operator recently concurred.

“It [the MineTracer system] makes us a much more efficient coal mine,” said Big Branch superintendent Les Fox.