"When we were called in to evaluate their drum requirements, they told us they wanted more production out of their plant by converting to a counterflow system, but they wanted to accomplish that objective without making a lot of major changes to their existing plant," Murphy notes. "Other drum designs have flight zones that are 4-foot 8-inch to 5-foot long and our design has flight zones that are 2.5-foot long due to the shorter rows and staggering of the flights.
"The design produces better veiling, more uniform veiling of the material during the drying process, which allows the material to dry in a shorter distance as it travels down the drum," he says.
The other advantage results from the MAXAMizer Heat Recovery System, which reduces the air and fuel required to dry the material being processed. That allows for increased production at a lower cost per ton.
According to Cox, the 320-tph Maxam drum system fits the bill for the plant's production needs.
"The installation really went well and the production capacity is all we need to serve our customers," Cox says. "We generally operate year-round, six days a week, and we don't run any RAP (reclaimed asphalt pavement) in our mix designs because Arizona (Department of Transportation) doesn't spec RAP into projects.
"The new drum system is easy to operate and maintain, and the electrical system required to install and operate the new drum is very simple and straightforward," he adds.
The Vulcan plant serves a variety of customer needs from residential mix requirements to DOT Superpave designs.
"Everybody wants more production out of their plants, but we just want to produce the quality mix our customers demand and do so in the most cost-effective manner possible," Cox says. "We went with the waste oil burner for efficiency and we went with the heat recovery system for efficiency and to reduce unnecessary emissions."
The other significant benefit of the new Maxam drum that Cox really likes is the self-aligning trunnions.
"We never have to worry about making adjustments to the trunnions because they're free-floating, and that minimizes the wear and maintenance concerns you have with other systems," Cox says. "On average, we're operating this plant at about 90 percent capacity. So, we know we have the capacity to meet the needs of our customers and we know we can operate without worrying about some of the usual maintenance items you have to address on other systems."
Cox also notes that the flights inside the drum are easy to maintain and the close spacing that produces a uniform veil during the mixing process helps produce the quality mix he wants to turn out.
"We have two 200-ton silos at this facility, and with this new drum, we know we can keep up with the various mixes our customers require, and we can do it in an economical and productive manner," Cox says. "We're a grocery store operation, stopping and starting all day. We have to produce three or four different mix designs each day, and the new system allows us to do that without a lot of wasted product and minimal disruption to our production.
"We also had a stack test (for emissions) shortly after installing the new system and the output was well below that of our old parallel-flow drum system," he adds. "That's another significant benefit for the community we serve."
So for Cox and the Vulcan operation, the drum upgrade has given the old plant a new lease on life and has allowed the asphalt produce to increase production, cut its production costs, and lower emissions in the process.