Dr Ramani first visited Australia some 23 years ago and, apart from a whistle-stop tour of Blackwater in 1977, had not been back in an Australian coal mine since. During his recent visit, he saw five thick longwall faces in New South Wales and Queensland. In comparing US and Australian conditions, Dr Ramani noted that technology, retreat mining methods and geological conditions were similar. The main differences were an average face width in Australia of 250m as opposed to 280-300m in the US, and an average panel length of 2500m in Australia versus 3000-4000m in the US.

Dr Ramani believes the move to mine thicker seams will necessitate adaptations to current longwall technology, comparable to the adaptations that took place when longwalling was introduced into US mines in the 1950s. In particular the development of thick seam mining technology in Australia would see a greater amount of dust being generated underground.

In recent years two of the main issues to have occupied US longwall mines have been subsidence and dust control, Dr Ramani said. Subsidence had been a major environmental issue in the US, but has been successfully handled at both state and federal government levels, while dust is of serious concern in the US because of high levels of black lung disease among miners and instances of sampling fraud in some underground mines.

Black lung (pneumoconiosis) and silicosis are irreversible, disabling and long suffering fatal lung diseases. In 1998, US mine operators reported 238 new cases of black lung and silicosis among coal miners. Some x-ray surveillance programs in the 1990s detected signs of black lung in more than 9% of participating underground coal miners and more than 4% of participating surface coal miners.

Dr Ramani was part of a federal taskforce formed in 1996 to assess the problem in the US. One of the areas of research evaluated real-time dust monitors because the results of dust sampling in the past usually took over a week to be processed. He said the development of a prototype respirable dust dosimeter was a promising advancement.

“Dust control in longwalling is now a major topic because of increasing production from longwalls,” Dr Ramani said. “In the US there are questions about whether we have adequate protection. Legislation prescribes 2mg/cu.m of air.”

He said one of the major concerns with dust was that it is chronic, insidious and manifests over a very long period of time. “I define the gas problem as instantaneously catastrophic. Therefore, everyone pays attention. The level of importance attached to dust grows the more we know about it.”

From his visits to Australian mines, Dr Ramani observed that in three mines dust seemed to be the domain of the production personnel. “The ventilation people don’t appear to get actively involved in dust control practices, as in the US,” he said. “In the US you will find whoever is responsible for ventilation is also responsible for dust. The production people generate the dust, but once it enters the ventilation stream it is everyone’s problem. We need to make sure everyone gets involved in the dust control problem in their own job. It is both an individual and collective responsibility.”

Dr Ramani warned that increased coal production brings with it additional dust generation. “For every tonne of coal produced we need to look at how much dust is produced by the shearer, the shields, the gate-end, etc. We need to produce a model relating dust generation with production to develop improved control technology.”

On the matter of increasing productivity, Dr Ramani said: “Question one is how to increase the production time of the longwall face? How can we get 480 minutes of coal production out of a 480-minute shift? Speaking as a mining engineer I feel we have to concentrate on understanding better the geological conditions and reduce their negative effects, but they are still the most difficult.

“Then we have to bring up the efficiency of everything else. The shearer should be available 100% of the time, shields 100%, and the outbye clearance must be available pretty much 100% of the time.

“The only unpredictable thing about the whole mining system is the geology, whether you’re going to get into rough cutting conditions, etc. The rest of it is purely mechanical. The conveyors are mechanical; the roof supports are mechanical. The only thing I accept as a problem is geological conditions such as bad roof, unexpected gas or water conditions.”

* This article originally appeared in the September 2000 edition of Australia's Longwalls.