While legislation stipulates diesel engines are only permitted to be operated in methane levels of less that 1.25%, Simtars testing is proving they can be safely operated at nearly 10 times that level.

Convinced that flameproof diesel engines can be a vital vehicle for underground emergency escapes, Simtars - in association with the Queensland Mines and Rescue Service - has continued a two-year project testing engine performance in high methane atmospheres.

The results have shown that not only can the engines function, they may be able to be fitted with specially designed equipment and become life rafts in the event of an underground accident.

"Research just completed has shown that flameproof diesel engines can be safely operated without loss of control at up to 12 percent methane," said Simtars principal engineer Ray Davis.

"A transport vehicle fitted with a flameproof diesel engine suddenly encountering a high methane concentration would have more power available to it.

"The operator could easily allow for this increased power by reducing pedal effort. In the worst case situation, and particularly with worn engines, the engine may idle at high revs - up to 2500rpm."

The engines have also proven to operate safely when exposed to oxygen levels as low as 17%.

Davis said Simtars has modified a personnel transport vehicle to be fitted with a high-speed methane analyser, a sonic navigation device and an onboard air supply as a prototype for testing as a means of underground escape.

While the devices require certification before they can be operated underground, he said they have demonstrated - through testing - their worth.

"Many underground coal mine production faces in Queensland are over seven kilometres from the surface," Davis explained.

"In the event of a fire or explosion, this is a long way to walk if a miner is wearing an oxygen self-rescuer. Indeed, trial emergency evacuations held over the past few years in Queensland have indicated that many miners would not survive such a walk.

"Under such circumstances, the possibility of assisting an injured person to escape is considered highly unlikely. Added to this, visibility in the mine can be reduced to zero as fine coal dust is raised into suspension following an explosion."

In terms of engine performance Davis said research proved worn engines showed a tendency to rev quite high - up to 2500rpm - at idle when methane concentrations reached 6 - 8%.

"This tendency meant that the vehicle could be driven at speeds up to 10 kilometres per hour in top gear on level ground without using the accelerator pedal," Davis said.

"Selecting first gear kept this speed to three to four kilometres per hour. For lower speeds than this, the brakes would need to be applied. It may be necessary to drive slower, if visibility was extremely poor."

Next on the agenda for the research team is negotiating with OEMs to develop an intrinsically safe methane analyser and sonic navigation system.

Davis said while Simtars is certain the devices will prove priceless at mines the two groups had to overcome cost and marketability obstacles.

"ACARP is continuing to engage industry directly to garner support to cement a market for the products. Currently several mining companies have committed to help fund this development," Davis said.

"The availability of a transport vehicle, equipped with the features described above, that could assist in an evacuation may some day save a life that would otherwise be lost."