Coal Age

OCT 2015

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DSI Underground Systems has developed a noncombustible, non- respirable rock dust mixture (DYWIDust) and an application system (DYWIDuster). Coal operators can use the technique to convert their dry rock dust into a wet-dusting system that is dependable and user- friendly. The DYWIDuster is a hydraulically powered unit that sits in the bucket of a scoop. At the beginning of the shift, miners prepare a batch by mixing the dust with water and a polymer, and then set the system aside. They can apply the DYWIDust as needed as the contin- uous miner moves between headings without having to withdraw the crew from the section. Knowing the situation with dust compliance in the U.S., DSI began to research different wet and foam dust technologies. In 2011, the company partnered with a U.S. underground coal operator and began a development process. "After several months of work, we understood that we needed to have patents filed as far as protecting intellectual properties," said Jim Pinkley, president and general manager, DSI Underground Systems. "We filed two patents, one for the batching composition and the second for the applicator equip- ment." DSI now holds patents for the machines and the polymers in the U.S. and South Africa, and patents are pending in Australia. The company then engaged the Mine Safety and Health Administration (MSHA) and the National Institute for Occupational Safety and Health (NIOSH). The NIOSH protocol for evaluation involved underground testing at the Bruceton facilities and working with another underground coal operator in the U.S. DSI completed several underground tests at their site. All of the data was evaluated by MSHA tech support and NIOSH. The evaluation process was completed in July 2013. Part of the protocol involved building a blast canister that could operate in complete coal dust explosions. Working with the University of Kentucky, DSI built a canister and completed a series of inerting tests with coal dust explosions. "To date, the DSI DYWIDust product, when dry, has never failed a coal dust inerting test," Pinkley said, "At that point, we felt pretty good about the product as far as how well it would perform underground." This is an allowed version of MSHA wet dust product in 75.403, Pinkley explained. "We place a good amount of rock dust on the roof and ribs compared to MSHA's wet dust," Pinkley said. "It appears we have better rock dust application." "The allowance in 30 CFR is for an application of foam rock dust followed by a dry dust application," said John McDonnell, technical director, DSI Underground Systems. "The foam dust, when any has tested similarly to dry dusting with inerting explosions and noncom- bustible material compliance. At the very least, we believe it should reduce the amount of dry dust." In July, 30CFR 75.403 was updated with the allowance for the application of foam rock dust. "For any mine using the MSHA wet dust now, this is a similar process that reduces the splash back and makes the coverage more efficient," McDonnell said. "It reduces the time it takes to wet dust a section." Dispensing DYWIDust The mine supplies the rock dust and adds the water and DSI polymer using the DSI dispensing machine, the DYWIDuster. "The mine uses their own C737 ASTM rock dust and we provide them with a set of batching instructions and a best practices sheet," McDonnell said. "They add water and dust and then the polymer concentrate additive, and then they agitate it to develop the DYWIDust." Applying DYWIDust is a two-man job, one scoop operator and one miner manning the applicator wand. The miners load the DYWIDuster into the bucket of a scoop and the mixing process begins. They roll it up to the face and apply the DYWIDust. For a face application, where the mine is taking a 40-ft cut, depending on roof height, Rusty Linn, technical sales and strategic business manager, DSI Underground Systems, estimates that they will cover four or five cuts from each batch they mix, depending on seam height. Miners can load the unit and mix a batch in 15 to 20 minutes. The DYWIDuster has two hydraulic lines with quick disconnects. It can be quickly offloaded into a crosscut and the scoop can still be used for other jobs. Essentially the applicator is similar to any other hydraulically powered accessory for a scoop in a coal mine. From a production standpoint, the continuous miner crews do not have to shut down for a whole shift and evacuate the section to rock dust. "The big advantage, however, is once they pull the bolter, they can start dusting while other people are working in the next entry," Linn said. "The system doesn't dust the other miners off the section." The polymer keeps the dust in suspension. "We have let a batch sit for 24 hours and then re-agitated it and sprayed it," Linn said. "They can mix the batch first thing at the beginning of the shift, leave it in the crosscut and then use it when it's needed." One of the things that hinders the MSHA wet dust program was the need to clear the machine at the end of the shift. If the 38 October 2015 The 160-gallon capacity DYWIDuster sits on one side of the scoop. Powered by the scoop's hydraulic system, the machine mixes and applies DYWIDust. o p e r a t i n g i d e a s Innovative Rock-Dusting System to Assist with Respirable Dust Compliance B Y S T E V E F I S C O R , E D I T O R - I N - C H I E F

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