Published in September 2006 Australian Longwall Magazine

The high risk and potentially explosive atmosphere of an underground coal mine presents many challenges to a mine operator, not the least of which is being able to locate and communicate with mine workers.

The new IS system, called Messenger, has been developed by Queensland-based company NLT Australia and its Canadian counterpart, Northern Light Technologies (NLT), and allows underground miners to send and receive messages through their cap lamps.

The 802.11 wireless two-way messaging device is integrated into the cap lamp and operates on an underground wireless local area network.

The idea of reliable two-way communications in the underground coal environment is relatively new, as fixed communications are not always easily reached by miners and other systems used for everyday communications (without IS approvals) have to be shut down during an emergency. Messenger addresses and solves this issue.

NLT managing director Tim Haight told Australian Longwall Magazine that Messenger operates on a combination of the existing mine fibre network and NLT’s Digital Network wireless nodes.

The complete Messenger system consists of three elements: the Digital Network; the Messenger Cap Lamp; and the NLT Mine Software suite, which includes messaging, tracking, traffic and environmental monitoring functions.

Messages are transmitted via the digital network and received and responded to with the cap lamp. The system is an SMS messaging type of product that operates on a wireless ethernet, similar to the systems that operate in domestic and office applications.

“But our products are much more rugged; we’re getting a heck of a lot more distance,” Haight said.

“We’re using antenna technology with our access points that is specially designed for underground – that enables us to get distance far beyond typical wireless ethernet you would see in most applications.”

Because the Digital Network operates on web-based software, a message can be sent from any PC on the network. The software looks for the miner’s lamp (Messenger) on the network but if the miner is out of range the system holds the message until his lamp connects and then sends the message.

The same also happens in reverse, so if a miner’s lamp is out of range when he sends a response, it buffers and then sends when he logs on, which means no messages lost in either direction.

The Messenger system also logs and time-stamps when the cap lamp received the message, when the miner read the message and when he responded.

“With one-way messaging systems, you would send a message out and never know if the intended recipient received it. Even if they did, they might be a half hour’s walk away from a phone, which means in most cases, no response,” Haight said.

“With Messenger they can reply straightaway, and the sender of the message can use any PC on the system to check whether it has been received.”

The NLT cap lamps also have their own internet protocol address, which essentially means they can be tracked and located.

“The product has been under development and evolving for about two to three years, and the lamp and tagging components have already been IS approved. Messenger and the associated access points are now weeks away from their own individual approvals,” Haight said.

A number of mines have already committed to using the technology, and Haight said the company expected to have several full systems up and running by the end of this year.

Looking towards the future of underground communications, Haight said he expected two-way communications to become commonplace throughout the industry.

“There has not been cost-effective two-way communications available until now. Leaky Feeder was trialled with limited, if any at all, success. The issue now is having reliable, intrinsically safe equipment available and easily deployable.

“It is really a market for niche companies such as ours – high on investment with slow return. Most of the larger players are not interested in the huge amount of development as well as being after a larger, quicker return,” Haight said.