Centennial Coal’s Myuna Colliery, winner of the Austmine Innovative Mining Solution at the 2017 Prospect Awards, was facing an uncertain future.
An underground mine at Wangi Wangi on the western shores of Lake Macquarie, Myuna, which uniquely mines three coal seams, has supplied Eraring Power Station, and currently employs 200 people.
The Myuna operation was facing certain closure unless a new mining system was identified to ensure long-term sustainability of the mine and its employees.
The Myuna operation supplies coal directly to Eraring via an overland conveyor. Coal from Myuna’s Fassifern seam was previously mined to higher ash B Ply, with place change mining, a process that produced a suitable product when blended with low ash from the Wallarah seam.
When mining at the Wallarah seam ceased, however, Fassifern seam place change operations had to mine to the lower ash C Ply, leading to higher costs and lower productivity due to the increased difficulty of supporting the C Ply mining horizon with the place change method.
Over 35 years of consistent operation, the geological conditions of the region had been affected to the extent that place change mining had become a less viable option for the Myuna project.
Place change mining is reliant on suitable geology and since the mines had become increasingly denuded, a change was needed to cement the project’s future success.
A viable system – the Myuna Herringbone System – was developed by the Centennial management team, in consultation with the workforce, after significant research and review.
The Myuna team selected the dual bolter miner super panel as the optimum mining method. It designed a herringbone layout involving unsupported cuts for improved strata control, lower costs, increased productivity, reduction in manual handling and musculoskeletal injuries.
Centennial improved productivity and efficiency in several ways, including a reduction in strata control costs.
The herringbone layout of the Myuna system was optimised for three-way intersections rather than the previously used four, eliminating the requirement of cable bolts and increasing unsupported cuts. This allowed for a much faster workflow due to the time saved by not having to bolt the roof.
As an added bonus, floor conditions also improved, as less time bolting led to reduced machine movement on the mine’s soft floor, and as a result less time on road repairs as a result. This also allowed miners to perform a second pass, allowing for increased hauls of high-quality floor coal. Altogether, the system has reduced associated costs of cable bolt supports by up to 85 per cent.
The Myuna Herringbone System has increased productivity at the mine by a massive 80 per cent, rising from 5000 tonnes per year to 8930 tonnes per year overall. The new system has also allowed production to shift from five days to seven, allowing for a 50 per cent increase in maintenance time.
To be recognised throughout the mining industry as a finalist for the Prospect Awards is a great honour,” said a Myuna spokesperson. “It shows that the industry encourages innovation and collaboration and that a wider audience has acknowledged the efforts of our workforce.”
“This is an opportunity to showcase all the hard work that the workforce and management have undertaken to make Myuna a sustainable operation moving forward. The workforce has embraced the change in operations at Myuna with outstanding results and this deserves to be recognised on a national stage.”
On the safety side, the Myuna Herringbone system uses auxiliary fans and vent tubes, decreasing risk of dust exposure to workers, replacing the previous brattice ventilation.
Total recordable injuries have decreased due to improvements in respiratory conditions, improved floor conditions (leading to fewer trips and falls), and less bolt cable handling thanks to the introduction of an efficient monorail system. The combination of these factors has seen an overall improvement in workplace culture.
“The current state of the mining industry is very positive with opportunities for growth and expansion not only for Myuna Colliery but the industry in general,” the spokesperson said. “Compared to this time last year, Myuna sees this current state in the industry as a move in a positive direction for Australian mining.”
This article also appears in the November edition of Australian Mining.