R&D Portfolio - Research Goal 3.1 : Reduce noise on continuous mining machines using coated flight bars
MSHA data indicate that of all underground coal mining equipment, the continuous mining machine has the highest percentage of operators whose noise exposure exceeds 100% of the PEL. Continuous miners are large machines that cut the coal at the working face of coal mines, gather it up, and transport it via an onboard conveyor to the back of the machine where it is loaded onto either another conveyor or other equipment designed to carry the coal away from the working face. One of the major noise sources on continuous mining machines is the onboard conveyor. It consists of a chain with flight bars that drag the coal along the base of the conveyor system. The metal chain and flight bars in contact with the metal base and the coal itself are a significant noise source and contribute as much as 50% of the noise exposure of workers at the face. Continuous miner operators stand near the chain conveyor, especially at the back of the machine, and receive a significant portion of their noise exposure from the conveyor.
The HLR program addressed this issue by developing a chain conveyor with coated flights as a noise control for these machines. By coating the flight bars with a heavy-duty, highly-durable plastic, the noise generated by metal to metal and metal to coal contact was reduced by approximately 7 dB(A) at the operator position.,  In many cases, this brought the machine operator’s noise exposure into compliance with current regulations. The coated flight bars have proven to be very durable in the harsh mining environment, lasting at least six months. That is comparable to the expected life of a chain conveyor with the old flight bars. The HLR program designed, developed, and lab tested this control in a partnership effort with labor (UMWA), industry (NMA, BCOA), a continuous miner manufacturer (Joy Mining Machinery), and MSHA.
Coated flight bars on a continuous mining machine
 Internal database maintained by Department of Labor, Mine Safety and Health Administration, August 2004