Crinum in central Queensland has experienced plenty of success at its South mine, consistently featuring in the top five Australian longwall producers. However, a 60m displacement fault system bound to the east of Longwall 15 dictated operations would have to be moved.
Mine planners assessed the opportunities and challenges of developing through the fault and continuing with the main entries versus developing a punch longwall from the existing open cut on the east side of the fault. The punch longwall option was chosen, using an existing open cut highwall and the development of a purpose-built box cut to access the six longwall panels.
Like any major longwall move a lot of planning went into the strategy and scheduling. Planning for the relocation from Crinum South to Crinum East began in 2007 with 60 days scheduled for the entire move.
To take full advantage of the move, BMA decided upon a significant retrofit of the mine’s roof supports, including a new hydraulic and electric control system, a full rehose, and new DA rams and relay bars on the full face of 156 shields.
The retrofit was undertaken by Bucyrus in Mackay, with the original equipment manufacturer budgeting six retrofits per day in an assembly line fashion. Bucyrus met the challenge successfully and the shields were delivered back to the mine in time for installation at Crinum East within schedule.
“Transport logistics were considerable and made more challenging due to the January floods that cut roads and limited carry weights,” said Gregory Crinum Mine general manager Steve Badenhorst. “Despite the complexity of moving an entire longwall from one mining area over a public road to another mining area the move was carried out in 57 days, three under budget.
“The success of the move was due to detailed planning early in the project with a very strong focus on roles and responsibilities and detailed contingency plans.”
In the new East area the mine has been able to take advantage of a mainly new conveyor system – a challenge at the previous South area.
“The biggest operational challenge at the Crinum South mine was the five underground and one surface conveyor system,” Badenhorst said. “Some of these belts were nearly 14 years old and unreliable. The age and some power restrictions which had developed with distance from the surface resulted in a requirement to limit longwall capacity.”
He said although the majority of the drives had been re-used from the South, much of the Crinum East conveyor infrastructure was new with a full nameplate capacity of 4000 tonnes per hour.
The punch system has also meant only a single underground conveyor system is required to be installed. “The surface conveyors benefit from reduced telemetric monitoring and underground restrictions, as well as the improved access for maintenance with vehicles and cranage,” Badenhorst said, adding the early benefits of the system had already been realised on the first panel.
The mine is working to meet its production targets in the new area. “After an issue with staple locks and a first cave weighting event, the benefits of a punch longwall system, some new equipment, good strata conditions and new conveyors have resulted in significant productivity gains,” Badenhorst said.
Besides the new conveyors and retrofitted roof supports, a new longwall transformer, distribution control box and pump cart were also commissioned on the first panel at Crinum East.
The new face is an identical width (270m) to Crinum South. However, mine management said a rebuild program had been initiated involving the purchase of 19 additional shields, allowing 19 shields to be fully rebuilt during the operation of each panel.
Badenhorst said this program would enable the mine to use the 1996 shields in the next punch longwall mining area – Crinum North – and widen the wall to a planned 303m.
BMA will spend four years at Crinum East before relocation to Crinum North.
