Also sufficient longwall retreating was yet to occur to achieve initial roof caving, so no experience of caving characteristics was available to date, the company said in its quarterly statement yesterday.

Underground installation of the longwall began in early April 2012 and was completed on June 6 with the first longwall coal cut on June 12. But the company was now seeking to address automation software issues with the longwall manufacturer Caterpillar/Bucyrus, Whitehaven said.

The commissioning and ramp-up of the longwall was expected to take approximately 12 weeks, during which time start-up issues would be addressed, any rectification and modification works done and operating practices developed, Whitehaven said.

“As with any installation of a new longwall into a new mining environment, there is a significant learning curve as experience is gained with the mining conditions and the machinery,” it said.

“Mechanical and electrical commissioning of the longwall underground has progressed well, except for the automation software, with which Cat/Bucyrus has not yet been able to achieve effective operation.

“This is requiring the longwall to be operated manually, which is in turn putting additional pressure on the training of Narrabri’s longwall operating team. This software issue and a number of other less important issues are being actively addressed with Cat/Bucyrus.

“CAT/Bucyrus remains accountable for achieving design performance of the longwall and Narrabri is working actively with them to ensure commissioning and ramp-up objectives are achieved.”

The Narrabri longwall has produced 20,000t so far during commissioning. Narrabri underground development continued during the June quarter with four continuous miners operating and a total of 86,000t of ROM coal produced in the quarter.

A total of 386,000t of ROM coal was produced from Narrabri for the year to June 30, 2012.

The main operating issue currently being addressed is the development of longwall operating techniques for dealing with the relatively hard Narrabri coal.

“This was an issue that also had to be dealt with when Narrabri commenced continuous miner [CM] operations, when the initial setup of the CM cutting heads was ineffective,” Whitehaven said.

“Modifications to pick design resolved this problem with the CMs. A number of modifications to the longwall shearer pick specifications are being trialled to achieve the desired outcome.”

Assuming the longwall commissioning and ramp-up proceeds broadly as planned, forecast production is between 4 and 5Mt of ROM coal in FY2013.

“Narrabri mining conditions remain excellent and development productivity is good,” Whitehaven said.

“Main road development has advanced to longwall panel #3 and installation of the maingate conveyor for longwall panel #2 is complete, with maingate #2 development now underway.”

Narrabri continues to successfully drain in-seam gas (85% CO2) to levels below the threshold required for continuous mining. A program of surface to in-seam and underground in-seam drilling is continuing and a substantial inventory of drained coal is being established, with the development roadways for longwall panel #5 now being drained.

Mine infrastructure at Narrabri is operating well, including the permanent ventilation system and coal handling and process plant (CHPP), however the CHPP is yet to achieve its full capacity of 1000t per hour and is currently running at around 900tph.

A number of issues are being addressed with Sedgman, however large throughput tonnages of longwall coal are required before the CHPP can be fully optimised so that steady, high volume operation can be achieved.

Narrabri has also commissioned an upgrade to the original Stage 1 raw coal crushing and stacking system, which is currently unutilised. When upgraded, this will provide an additional 1000 tph of raw saleable coal crushing and stacking capacity, which will provide redundancy for the CHPP and additional capacity if and when required.

The shortage of skilled labour for Narrabri remains a challenge for the company.

“There is continuing difficulty in recruiting sufficient experienced underground miners and professional staff to achieve the full complement of people at Narrabri, but this is currently not hampering effective operations,” the company said.

“Whitehaven is continuing to actively pursue options for recruitment, including internationally.”