Aggregates Manager Digital Magazine
Issue link: https://read.dmtmag.com/i/120734
OPERAT Bes 1 Understand the physics Start with a Good Sample W hen it comes to making sure that the customer is happy with the product loaded into his truck, there are few steps more important than proper sampling to ensure the product meets the specifications of the customer's order. "One of the keys to stockpile management is that you don't have a problem until somebody grabs a sample and says it's out of gradation," says James R.D. Cox, director of technical services, aggregate, for Cemex USA. "A lot of times, I find that we're not obtaining a representative sample of that material. To me, that is probably the most common problem." In fact, members of the technical committee of the Ohio Aggregates & Industrial Minerals Association (OAIMA) identified sampling technology as an educational target area. "The technical committee felt that sampling technology was low-hanging fruit in terms of consistency and reliability of results," says Patrick A. Jacomet, executive director of OAIMA. "We felt that if we didn't get a proper sample, we didn't have good data." To help operators better understand how segregation takes place during the formation of a stockpile and how to both sample and load correctly, the association developed tools and training. Scale-model sizes of various aggregates were created in an assortment of colors, and a scale conveyor belt was developed. AGGREGATES MANAGER "The premise was that we knew material segregated at the stockpile, but we couldn't see the different sizes because, generally, the sizes blend together when you look at the stockpile," Jacomet says. "By creating the scale model aggregate and conveyor, we could actually create stockpiles with the colored aggregate and see the sizes. You could see the coarse material roll down to the toe and front of the pile. You could see the fines toward the conveyor side of the pile. It was one of those 'aha' moments. We knew we had something that would show everyone, and they'd understand." Once operators understand how stockpile segregation takes place, it's much more likely that they will work the stockpile with that in mind. One way to ensure the right mix of product is to "load out the material 90 degrees to the creation of the stockpile," Cox says. "If you can get in 90 degrees to the conveyor and load across the face of the stockpile, you will help reduce the segregation tremendously." He trains equipment operators on how to get into the stockpile to obtain a representative sample. The operator then uses the same techniques when loading customer trucks, ensuring the same results. "It's amazing how a lot of people, even people who are in testing, don't take the time to instruct loader operators on how to properly take samples and, at the same time, coach on how to load customer trucks," Cox adds. As it is transported to a stockpile, fine materials tend to sink, while more coarse material tends to float. When a conveyor discharges aggregate, fine material falls near the end of the belt, leaving it in the middle of the stockpile, while larger-sized material rolls to the bottom of the stockpile and the toe. With a truck dump stockpile, fine material falls near the highwall as coarse material drops along the outer and upper portions of the stockpile. 4 Reduce degradation Material degradation can take place from over-handling of material, particularly in aggregates with high L.A. abrasion. Eliminate unnecessary transfers of material and minimize the distance material falls from the conveyor or truck to the stockpile. The same holds true when loading the aggregate into the customer's truck. Rather than dumping it from a point that is higher than necessary, gently roll the bucket into the truck bed.