In his presentation on “Respirable dust past, present and future” Borchick outlined the current regulations governing underground coal mines, and the control measures mines were using underground, both around the longwall and the continuous miner.
Respirable coal dust consists of very small particles that can be inhaled and deposited in the lungs causing coal worker’s pneumoconiosis (black lung), silicosis, and chronic obstructive pulmonary disease.
As every worker underground knows, dust is particularly prevalent when cutting coal on the face, coal loading, drilling, crushers and feeders, conveyors and transfer points, shield movement, blasting, and equipment traveling on haul roads.
Coal dust exposure is regulated by Title 30 CFR, Part 70, which has established a respirable coal mine dust standard of 2mg/m3, unless quartz is present. It also provides for a dust standard of 1mg/m3 for intake air.
The regulation also stipulates mine operators must collect and submit 5 dust samples from a designated occupation during each bimonthly sampling period. Operators are also required to develop and submit a Dust Control Plan to be approved by Mine Safety and Health Administration.
Most coal mines revolve their dust control around a few simple principals: prevent dust generation, remove dust from the atmosphere, suppress dust before it enters the miner’s breathing zone, isolate the miner from the dust, and dilute dust to lower concentrations.
On the continuous miner controls include water spray design and location, remote control operation, machine mounted scrubbers, spray fan, cutting sequence, ventilation, and outby contamination controls.
At the longwall face controls include shearer and shield water sprays, remote control operation, stage loader mounted scrubbers, cutting sequence, ventilation, water additives, outby contamination controls, worker positioning and PPE.
Obviously the most effective control for dust is removing the worker from the dust. Borchick said in the future automation would become more reliable, enabling management to remove people from the longwall face.
He said shield water sprays and water curtains offer promising results for better dust control, adding water infusion was bound to become more common as more mines use horizontal degas holes to reduce methane liberation prior to longwall mining.
Looking ahead, Borchick said regulations could change to lower the coal mine dust standard, but there was much debate surrounding this option over whether the move was necessary.
He said new continuous personal dust monitor sampling devices, like the PDM, could be adopted and regulations could be changed to incorporate the new technology that has been developed.
“Most agree that real time sampling devices should be utilized in future respirable dust sampling,” he said.
“It may now be time to take another look at the original sampling methods with the development of new technologies, and to upgrade the present system to the 21st century.”