Published in June 2007 Australian Longwall Magazine

Differing opinions marked this year’s Australian Longwall Magazine consultants’ survey. While some consultants heralded longwall top coal caving and the 400-plus metre longwall face as a great development with an exciting future, others remained more hesitant, pointing out the dangers and complexity of these new methods.

Though some consultants called the rise in the number of junior and mid-tier players as “healthy”, others drew attention to the shortcomings of smaller companies and the push to get things done while the going is good.

What all the consultants did seem to agree on was that while the “clean coal” push was going to be hard yards at the start, it was essential for the industry’s future.

Consultants taking part in this year’s survey comprised Coffey Mining; IMC Mining Solutions; John T Boyd; Minarco, MineConsult, Runge; Mining Consultancy Services; Palaris Mining; Seedsman Geotechnics; Snowden; SRK Consulting; and Strata Engineering.

All the rage

The Australian longwall industry has entered an exciting phase with the ramp up of Australia’s widest face at Ulan and the introduction of longwall top coal caving at Austar. The consultants had mixed reactions to the onset of these new methods but most agreed the jury was still out on the success of operating a wider face in Australia, and whether LTCC will succeed.

Snowden’s Kevin Irving summed up LTCC as “an exciting development in Australia and one that people will watch with interest” – certainly true given the popularity of Austar stories with this magazine’s readers.

Coffey Mining principal engineer Brian White said the increase in production and long-term reduction in production costs from both methods would assist in reducing the impact from prevalent issues such as the ageing work force, the skills shortage, and the consequential increase in salaries.

Minarco, MineConsult, Runge said LTCC may have a significant impact on the risk profile of deeper operations with thicker seams, as LTCC provides face stability benefits – critical at increasing depth.

Seedsman Geotechnics’ Ross Seedsman was a little more anxious about the benefits of the new methods. “These improved longwall technologies are just increasing the pressure on development, and possibly drawing attention and expertise away from solving that problem.”

While for many the success of LTCC was still to be proven in Australia, Strata Engineering chief executive Tim Watson said no specific reports of reliability issues from Austar to date should “certainly ease the fears of other operators who may be considering using the system”

John T Boyd Australia managing director Ian Alexander showed some apprehension about the short-term success of LTCC in Australia, stating while it was an effective method for maximising coal resource recovery, it would take some time before it is widely embraced by the Australian industry.

“There are potential issues with untrained labour (both operators and maintenance), increased dust generation from the caving process and significant dilution.

“Top coal caving methods are generally less productive on a shift or day basis than one pass shearing methods. The time required for the un-sheared coal to crush and fail is dependent upon several factors including coal strength, location in the face line, depth of cover, and strength of roof strata.

“Coal generation from the longwall face cannot be sped up as is the case with single pass shearing systems. Another potential limitation of top coal caving methods is in highly gassy seams, where the caving process promotes a sharp increase in methane gas emissions.”

Mining Consultancy Services’ Chris Wilkinson felt while the jury was still out on the success and applicability of LTCC in Australia, it could provide a viable alternative to conventional longwall technology in many applications. MCS is currently undertaking a study on the application of LTCC in central Queensland.

Wilkinson was also upbeat on the adoption of the wider face in Australia and named Ulan as the possible successful forerunner of several face extension projects on the cards.

While wider faces offer the benefits of reduced development to extraction, reduced frequency of face moves and improved reserve recovery, if a mine was not suitable to expand its face due to poor roof conditions, Wilkinson said this may well “change the competitiveness of some mines” into the future.

John T Boyd added while wider faces offered significant advantages in reducing development, it had downsides. “Significantly higher capital costs, as the roof supports are the largest capital component of an underground longwall mine, and increasingly more powerful main/tailgate drives to move the larger chain and coal on the chain. The more powerful equipment results in more heat at the longwall face, which is already an issue in Queensland mines and many are already moving to refrigeration methods to keep temperatures below statutory levels, particularly in development.

“There are relatively fewer simple, un-faulted deposits remaining that are suitable for a longwall installation; the wider faces further reduce mine plan flexibility and resource recovery.”

Alexander said despite these issues, John T Boyd expected to see more longwall installations with wider face widths as newer generation faces replace older equipment.

Snowden’s Irving backed wider faces in Australian mines, stating they could “only improve operational efficiencies of the longwall” primarily by reducing the number of turnarounds at each end of the face. “As mines go deeper and the face ‘T’ junction becomes increasingly more difficult to control, then long faces become a very desirable proposition.” He also emphasised the importance of keeping the face advancing.

IMC Mining Solutions principal consultant Chris Hanson said recent experiences at Oaky No 1 and Ulan had been positive, but the benefits needed to be balanced againstArticle continues, click here.