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product news Clearing the Air Underground with Shotcrete
Based in Anniston, Ala., Blastcrete Equipment provides a variety of wet and dry shotcrete equipment. With more than 60 years of experience in the manufacturing industry, Blastcrete has established itself as a company committed to providing high value equipment for enhancing mine safe- ty. The company offers a variety of mixer and pumps in its product line.
The compact Mine Mate system applies 12 cubic yards of shotcrete per hour.
In recent years, a string of coal mine igni- tions have exposed the danger posed to underground coal miners. Explosions are one of the extreme hazards associated with underground coal mining; others include a lack of fresh air, working in con- fined space, and reduced visibility. Miners enter this environment on a daily basis to cut coal.
Strata Mine Services (SMS) is one of the companies trying to help ensure the safety of those working underground. SMS is a contracting service company that mining companies employee to handle a variety of projects, anything from general labor to ventilation controls. "One of our specialties is in the application of shotcrete as under- ground reinforcements for use with spray panel overcasts," said Jeff Waggett, P.E., senior development engineer, SMS. Spray panel overcast systems are often used to properly ventilate underground workings. Constructed of lightweight pan- els, overcasts are designed to isolate a pas- sageway or prevent air from mixing at the intersection of two aircourses. "As one can imagine, ventilation is a crucial element of underground safety so it's a major compo- nent of our offerings," Wagget said.
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These structures consist of two layers of wire mesh with polystyrene in between each layer. The layout is similar to that of a highway overpass, except in this case, it's air (not vehicles) that is being redirected to avoid collision. Before the structures can be deemed complete, they must first be rein- forced with wet or dry shotcrete (gunite). Wet shotcrete is the process of pumping a low slump concrete material to a dis- charge nozzle where compressed air is injected allowing the material to be sprayed on to vertical and overhead surfaces. Dry shotcrete (gunite) is the process of intro- ducing a dry or predampened shotcrete material into an air stream that conveys the material to a nozzle where water is injected in to the material. Both processes require special equipment to apply the material. Specialized construction work such as this is part of the SMS repertoire. The company has a long-standing commit- ment to safety, with quality work and cus- tomer service key to its core values. For the company to provide this elevated lev- el of service to customers, it needs reli- able equipment from trusted suppliers. Blastcrete Equipment Co. is one such supplier.
Waggett began working with Blastcrete in June 2010 when he purchased cus- tomized versions of the company's AA020 Piccola gunite machines. At the time, Strata was using the dry gunite process almost exclusively for the overcast systems, and Waggett was looking to add some new machines to the mix. "As a development engineer, I have a lot of involvement on the product and equipment side of the busi- ness," Waggett said. "So I'm always the type of person seeking out new, advanced equip- ment. Something that's easier to operate, safer and more cost-effective."
What initially drew Strata and Waggett to Blastcrete was the ability to obtain custom equipment. "Unlike other manufacturers we've worked with in the past, we didn't have to purchase the model 'off the shelf,'" Waggett said. "Blastcrete was willing to work closely with us to customize the equipment to suit our exact needs. Up to that point, no other company had been willing to do that." Strata had been using dry process shotcrete, as it had been the industry stan- dard. But gunite certainly comes with its share of drawbacks and Strata was really beginning to notice the negative implica- tions. Because it's a dry-mix process, gunite applications produce a lot of dust—a major problem in underground mines where air passes throughout the entire mine. Once that air is laden with dust, it will circulate to the other areas in the mine causing a seri- ous health and safety concern.
For Waggett, the health and safety issues were a top concern. "In addition to breath- ing in harmful dust, there's also the safety issue of reduced visibility. You can't see as well when there are dust particles every- where," he said.
Strata had been exploring the idea of using a wet-mix, or wet shotcrete, process to combat some of the issues posed by the dust. Typically, a wet-mix shotcrete process
December 2011