Austar the trailblazer

ABANDONED by Australia’s coal scene following the Christmas Day fire in 2003, Yancoal Australia’s Austar mine is shaking off industry misconceptions while assisting Bucyrus and the Chinese with innovations to the longwall top coal caving process.

Blair Price

Published in March 2010 Australian Longwall Magazine

The former Southland colliery near Cessnock in the Hunter Valley was acquired by Yancoal’s parent company, Yanzhou Coal Mining, for a mere $US24 million back in 2004, contrasting with Yanzhou’s $A3.5 billion takeover of Felix Resources at the end of 2009.

While the old mine is known for its heavy strata conditions and for sending previous owner Gympie Gold broke after the devastating fire, Austar is paving the road for future LTCC mining in Australia and demonstrating that Chinese ownership does not halt Aussie innovation.

Austar will gain part ownership of new LTCC technology being developed at the mine in conjunction with Bucyrus, currently the only supplier with LTCC equipment installed in Australia.

The mine is trialling a new Bucyrus interlace drive on the rear armoured face conveyor which catches the collapsed coal, and Yanzhou personnel are keeping track of the progress. The interlace drive will eliminate the need for a rear drive, as the gear box comes to the heading.

The better design will cut lost production time caused by blockages on the rear AFC.

Longwall mechanical engineer Matthew Wang said Yanzhou was learning from how Austar could improve its LTCC set-up.

Apart from the promise held by the research and development on the interlace drive, he said Austar made superior use of shearer sprays and also employed Bucyrus’s latest PMC-R system for the shields – which is unavailable in China.

Austar produced 1.8 million tonnes of run-of-mine coal in 2009, well below LTCC output of up to 7Mt in Chinese operations, with the mine’s conveyor system limiting the pace of production.

Austar mine manager Dave McLean said the shearer was running at 5 metres per minute along the 220m-wide longwall face, unlike the 8-12m/min at most other mines.

“Our drift belt is running 1000 tonnes per hour and our overland belt to the washery is rated at 750 tonnes per hour,” he said.

“You can imagine what sort of bottleneck that is when you have a longwall that’s capable of producing 3500 tonnes per hour.

“In saying that, we have achieved over 70,000 tonnes per week during my time at the mine.

“We have also got constraints on the rail, as the South Maitland Railway line is limited to a 19-tonne axle load, and our train shunt at the coal preparation plant limits the load to around 2000 tonnes per set.

“From a logistical point of view, our outbye belt capacity and our rail are two things that would really open the mine up if they were to be upgraded.”

McLean said Austar had huge potential and was working towards its Stage 3 expansion, with the mine heading east under the Quorrobolong Valley.

The expansion will lift production to 3.6Mt per annum ROM coal by 2016, with longwall blocks A6 to A17 expected to produce 45.3Mt over 21 years.

While the current depth of cover at the mine is 530m, the Stage 3 longwall panels – some more than 3km long – will extract the Greta seam at depths of 400-700m.

McLean said the current seam thickness ranged between 6m and 6.5m of coal, with up to 15m of interbedded siltstone and sandstone laminated roof.

Above this strata up to the surface lies solid and continuous sandstone known as the Branxton formation.

In total, more than 450m of sandstone lies above the seam, which makes Austar one of the deepest longwall mines in Australia.

The Stage 3 development consent has given approval for the mine until December 31, 2030. However, the mine plan layout for Stage 3 sees the exhaustion of reserves by 2040. Yanzhou has plans to develop the mine further into a Stage 4 area east of Abernethy.

McLean said the Stage 3 development included a corridor to allow access to Stage 4 with exploratory drilling in the area to kick off later this year.

Preparing the way for Stage 3 is the 18-month construction of a 465m-deep ventilation shaft, which started in December 2009. The shaft is located on the other side of a major faulting system (Quorrobolong fault) which separates the current workings from Stage 3. The fault drivage will be driven by a roadheader and is expected to start in the December quarter.

Crews are yet to drive through suchconditions as they get ready to take on the Central Dyke prior to reaching the Quorrobolong fault.

McLean said the mine design was based on conservative drivage rates as this would be the first time the mine workings would have passed through both structures. The Central Dyke consists of a 2m-thick dyke followed by another 20m-thick dyke separated by 40m of coal. The Quorrobolong fault is some 500m inbye of the Central Dyke.

The mine uses a detailed plan from belt move to belt move similar to most mines, but instead of process owners, Austar utilises the shift undermanagers to develop the weekly, day-to-day planning and operation of the development units. The medium to longer term planning is carried out by the production superintendent.

McLean said good progress had been made of late by development crews in testing conditions, with best rates at 34m and 31m in a 12-hour shift. These results are record shifts in the mine’s history.

While many Australian longwall mines have foreign ownership, Austar is the first Chinese-owned coal mine in the country and offers insight into Chinese management approaches. This has become more relevant since Yanzhou took over Felix Resources and China Shenhua Energy entered the country with the Watermark project in the Gunnedah Basin.

When Australian Longwall Magazine visited Austar, it was apparent general manager Frank Fulham and McLean were running the operation unhindered.

“We have a good working relationship with our Chinese colleagues,” McLean said.

“They brought their technology here and together we have adapted it to our conditions.”

McLean added that Chinese management at the mine were keenly watching, learning and listening while looking to the rest of the industry to see how coal was won in Australia.

The mine manager is also free to trial new innovations at the mine to yield operational and safety benefits.

In 2008 a high-potential incident involving the articulation area of the load haul dump occurred while attempting to line up and attach a trailer to the rear of the LHD.

Inspired by the guidance forks used on a passenger vehicle towbar to line up the tow hitch of a caravan, Austar employees came up with the design of a steel cone on the enclave of the mine’s LHDs to effortlessly guide the trailer’s tow point into position.

McLean plans to submit the design to the New South Wales Minerals Council awards this year. He said other longwall mines could easily implement the innovation, which would make the task of attaching a trailer safer and more efficient.

Austar miners use Mine Site Technologies’ PED communication system and the mine also employs MST’s tracker system to help locate people during an emergency and to yield operational efficiencies.

Tracking is expected to cut down the handover time between shifts and also to better manage the diesel fleet to keep safe levels of fresh air underground.

Austar has cut its lost-time injury frequency rate to 11, bettering the state underground mine average of 20 in 2008. Management attributed the rate to putting all Austar miners through a G1 safety and training course, supervisors completing the G2 course and a number of senior management staff completing the G3 risk management course. All three levels are based heavily on the workplace safety model (Nertney wheel).

At the start of 2009, to ensure hazards were identified and rectified before commencing work, the miners were reintroduced to the STAR system – Stop, Take Five, Assess, Resolve.

The next longwall move from panel A2 to A3 is planned this month, which will include a rehand and will extend the move up to three months.

Given the substantial downtime, Austar will shift to seven-day production in 2010 to maintain annual output.

The mine will then move to panel A4 in 2011, A5 in March 2012 and A6, the first Stage 3 longwall, in January 2013.

For strata control in the longwall tailgate roadway during longwall panel A2, the mine used three 8m bolts from Megabolt every 2m and also installed Link’n’lock cribs and timber props as needed.

“Our previous longwalls had used passive support like that more frequently, now we are installing a combination of 8-metre megabolts and 4-metre flexibolts along with additional 4-metre flexibolts into the ribs of the chain pillar,” McLean said.

“Generally what we are heading towards is a cribless tailgate. We’ve increased the size of the chain pillar and the density of our secondary support in an effort to improve the roadway stability and serviceability in an effort to minimise the use of passive support.”

Mining at Austar is also subject to cyclic loading, or “weighting events”, which are currently 20-25m apart. McLean said they had been iron-bound twice last year due to these events while mining under large sandstone channels that lay immediately above the seam.

Tough strata conditions and design issues, particularly in the goaf at the tailgate end, caused welds to break down on the legs of two shields underground last year, pulling the legs right out of the clevises on the underside of the shield canopy.

The matter was resolved after gaining approval from the Department of Planning and Infrastructure (now the Department of Industry and Investment) to allow cutting and welding on the longwall face to repair the damaged clevises.

Marking another first for the mine, Austar is working with Bucyrus to replace the six-legged gate-end shields by developing a four-legged shield to overcome the tough conditions, while at the same time affording greater protection to the rear AFC conveyor drives and improving cycle times around the gate ends.

Wang said Yancoal looked forward to changing the design. Chinese LTCC operations did not face the same issues due to a shorter maingate and rear canopy and a smaller gearbox on the drive, with the overall shorter length putting less force on the rear leg of the shields.

McLean said the development of the four-legged shield should be ready by October with a lot of the design coming from Austar’s engineering team.

In the meantime, the longwall crews bolt the roof at the tailgate end of the face at times, along with chain mesh to minimise coal tops falling between the shields and the rear tailgate drive. Cutting to the correct horizon in this area is critical to ensure operating standards are maintained and additional support in this area is kept to a minimum.

While the strata conditions can be unforgiving, high inseam gas content synonymous with deeper coal seams is not a hazard as Austar has only 2-3 cubic metres of inseam gas per tonne and rarely registers more than 0.1% methane in the general body of the tailgate.

Countering perceptions Austar was an old mine with nothing new, McLean said many people were unaware of the operation’s lengthy future, with over 25 years in Stage 3 alone.

Late last year, Austar held a round of the Newcastle Mines Rescue Service training sessions to assist with the training program and to familiarise other rescue trainees with the recent expansion of the mine.

McLean hoped the exercise had not only been a success for the NMRS, but had “opened people’s eyes” and showed the rest of the industry what improvements had been made in the way the mine was maintained and operated.

“You go to the mine now, you will see a totally different mine to what it was under previous owners,” he said.

“I believe the standards in the mine are second to none and I’ve been around a number of mines in the last few years.”

The recent takeover of Felix will offer Yancoal’s employees more career opportunities within the group.

It also gives Austar blending opportunity with Felix’s Moolarben and Ashton mines.

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