Published in the June 2011 Australian Longwall Magazine

Changing over from a hip-worn, self-contained self rescuer to a longer duration breathing apparatus is part of standard longwall mine evacuation strategies, yet emergency exercises have consistently found that many miners fail to correctly perform this critical task.

The Austar longwall mine in the Hunter Valley, which cuts coal at depths of greater than 450 metres, addressed this issue by installing a series of AirDocs at strategic locations throughout the mine back in 2006.

While management knew that changing over in hostile atmospheres was a major hazard, a safety exercise held in the last quarter of 2010 demonstrated the difficulties of using the hip-worn self rescuers in non-hazardous conditions.

In the scenario, a crew at a development panel unit was told that there was too much carbon monoxide coming into the panel.

Unlike other miners who suspected a possible safety drill was on the horizon, this particular crew did not know they would be put to the test. They were required to don their self rescuers and evacuate by the mine’s second egress.

To more closely simulate smoky conditions which limit visibility, Newcastle Mines Rescue staff covered up the crew’s cap lamps.

In the complete darkness they had to link together as a team to evacuate the area.

An AirDoc is always within 500-600 metres of a working face, and the crew needed to make this journey with their 20-minute duration self rescuers before changing over.

Austar outbye superintendent Tony Sutcliffe observed the difficulties the crew experienced during the exercise.

Once the crew entered the AirDoc and pulled off their self rescuers, he saw big sighs of relief all around as they bathed in the fresh air.

While it’s designed to provide a safe environment to safely changeover to longer duration self rescuers, each AirDoc can house eight people comfortably in seats.

In the exercise it also provided the crew members the opportunity to drink good water and prepare for other challenges.

“They could communicate with each other, they could also communicate with the Mines Rescue Service as well as the surface control room via the phone, in the AirDoc,” Sutcliffe said.

“They could recall and regather their thought processes and plan of attack to get out of the mine after that.”

The mouthpiece of a self rescuer prevents miners from even talking sideways, with communication to other crew members relying on hand signals and taps.

But once evacuating miners get together in the safe environment of an AirDoc, there is an opportunity to make vital group decisions.

In this scenario it quickly became evident that one of the crew members lacked fitness and could not keep up the pace.

He was the last to don his self rescuer and observers noted he struggled for the first 200 metres.

“In a real scenario, if we had to continue all the way back to the surface, the guy would have been left behind in that refuge, just because of his unfit state,” Sutcliffe said.

Sutcliffe clarified that the mine does not want people to stay behind in a changeover station and wait to be rescued.

“We don’t promote that, but if they have to stay in there, with the scrubber system removing the carbon dioxide, you have got six big G size medical air bottles to supply air as well.”

Fortunately there was no need to make such a decision, and the crew went on to fight a simulated fire before the exercise ended.

Sutcliffe did not rate the particular individual who struggled with his fitness as appearing significantly overweight.

When asked if there could be one unfit bloke in just about every underground crew, Sutcliffe said it was possible in the context of average body mass index ratios.

“I would definitely say in the mining industry, especially if you are a smoker, I think you will have quite a few unfit people.”

Strata Safety Products general manager Tony Farrugia led the development of the AirDoc, with this product designed to address industry concerns over the dangers of changing over from one self-rescuer to another in hostile environments.

“That is where the danger is and it’s very well documented, mines know if something is going to happen that’s where it will happen,” he said.

Farrugia was impressed with the benefits the AirDoc demonstrated in the scenario.

“We have never had any situation before where the units have been out under test in an exercise. And the exercise was monitored very carefully for the need of that type of equipment.”

He discussed the management observations from the exercise.

“Without the AirDoc they really thought some of the guys wouldn’t have made it,” Farrugia said.

Even in a controlled exercise environment, Farrugia does not discount the difficulties with using self-rescuers – especially the heat they generate during continual movement and how they affect communication.

“They were disorientated, they didn’t know where they were, there was just too much happening in an emergency, in that instance, without having a room to stop and collect your thoughts,” he said.

“Those changeover bases really prove the point that guys really need that, to rethink, collect their thoughts, work out a strategy and get going.”

Perhaps the biggest surprise was how necessary the AirDoc proved to be for unfit miners.

Farrugia notes that a lot of the mine rescue exercises and competitions involve guys who value their fitness.

“But in a real life scenario that’s not the case, you have got guys who smoke and their health is not 100%,” he said.

“They’re the ones who will struggle a lot more than the very fit person – the younger guys.

“Giving them that space to really recollect and regroup is virtually critical.”

To completely evacuate the mine, which stretches for around 8km, Sutcliffe estimated it could take two hours in a real emergency if smoke did not significantly affect the atmosphere.

Austar’s pioneering role with introducing the changeover stations to further strengthen safety is not surprising, given the damage to the mine from the Christmas Day fire in 2003 when it was known as the Southland colliery.

But Sutcliffe would like to see other mines introduce the changeover stations.

“In New South Wales, they [Strata Products] are not selling too many of the AirDoc stations to the mines that don’t run the compressed air breathing apparatus units,” he said.

“But a lot of other pits are just sticking these self-rescuers in a cut through in a box, not being proactive like here at Austar.

Crews at Austar feel safer having them at the mine, and they capture the attention of visitors from other longwall operations.

“I really think with all the visits we have here for our prospective deputies and undermanagers doing their certificates of competency, when they come and look at these AirDoc stations they are pretty impressed with what they see.”

Austar has eight AirDocs within the mine and, with consultation with Newcastle Mines Rescue after conducting simulated emergency walk out trials wearing rescuers, determined the maximum distance to have them apart from each other.

The mine recently added the new 60-minute duration Dräger Oxy 6000 self rescuer units to its range, while each of the AirDocs can house 120 self rescuers.

Fresh air to the changeover stations is supplied by a compressed air line, while the six bottles of medical air can turned on if that air supply is interrupted.

Mines which are more orientated towards CABA units than self-rescuers have not yet been a target market for the AirDoc.